I _JfJ LIBB ARY UNIVERSITY OF CALIFORNIA DAVIS DEPARTMENT OF NATURAL RESOURCES WARREN T. HANNUM, D.fKlof STATE OF CALIFORNIA EARL WARREN. Co>'«"'or DIVISION OF MINES Fffrry Building, Son FranciKO OlAF P. JENKINS. Clii«f Son Francisco Bulletin 158 December 1952 EVOLUTION OF THE CALIFORNIA LANDSCAPE By NORMAN E. A. HINDS Associate Professor, Oeporrment of Geological Sciences University of California, Berkeley, California LIBRARY UNIVERSITY OF CU-IFORNIA DAVIS LETTER OF TRANSMITTAL To His Excfxlenxy The Honorable Earl Warren Governor of the State of California Dear Sir: I have the honor to transmit herewith Bulletin 158, Evolution of the California Landscape, prepared under the direction of Olaf P. Jenkins, Chief of the Division of Mines, Department of Natural Resources. This volume is pro- fusely illustrated with photoo;raphs, maps, and drawings, characterizing the sig- nificant surface features of the entire State. The author. Professor Xorman E. A. Hinds of the Department of Geological Sciences, University of California, has systematically described those surface features as they are related to the geology and rock structures of the State, and has shown how these features have developed through natural processes operating over the long periods of time required to pro- duce California's diversified landscape. HuUetin 158 should find a useful place in the schools of the State and among those persons who love to travel and admire California. It should help to increase enjoyment of what is to be seen by explaining thoroughly why the surface features are what thev are. Respectfully submitted, Warren T. Hannum, Director Department of Xatural Resources Approved : W. T. H. November 17, 1952 (3) FRONTISPIECE. Sierra Nevada west of Bridgeport, Modo County. Photo by C. W. Chcsterman. TABLE OF CONTENTS Page Introduction 7 Sierra Nevada n~- Basin-Kanges 61 Mojave Desert 87 Colorado Desert 97 Modoc Plateau 109 Cascade Range 117"~ Klamath Mountains 137 — Great Valley 143— Coast Ranges 155, 231 — Transverse Ranges 183 Peninsular Ranges 195 Sea Floor 217 Index 233 ( 5 ) INTRODUCTION INTRODUCTION California may be divided into a number of units called geomorphic provincfs (the Sierra Ne\-ada. Basin Ranges, Mojave Desert, Colorado Desert, Modoc Plateau, Cascade Kanjre, Klamath Mountains, Great Valley, Coast Ranja^y:?:-:>wte sw NE KiG. 2. Cross section of the Rierrn Nevada. California, through Xlt. Whitney, its hichei«t peak. The boundar.v fault s.vstem along which the range has been elevated l>.v tilting is shown on the right-hand side of the section. In this part of the range, most of the rock exposed at the surface is granite, but there are considerable areas of the intensely folded and faulted bedrock into which the granite was intruded. Alter F. E. Slatthe; U. S. Oeol. Survey Prof. Paper ISO, p. 25. Most of the range trends slightly west of north, but at the southern end the direction changes to west of south. Strikingly contrasted are the two slopes : that to the west of the crest is broad and gentle, but that to the east is much more steeply inclined. Because of this unsj-m- metrical cross section, the crests of high peaks lie only a few miles from the eastern boundary of the Sierra Nevada, but from 30 to 70 miles from the western base. At the northern end of the Sierra, peaks of highest elevation are between 6.000 and 7,000 feet ; near Lake Tahoe, Pyramid Peak, Mount Tallac, and other mountains in the vicinity are 9.000 to more than 10,000 feet high ; in Yosemite National Park, the peaks reach 12,000 to 13,000 feet in elevation ; and in Mount Whitney region the highest peaks are found — Mounts Williamson (14,384 feet) and Langley (14,042 feet), and, of course. Mount Whitney itself (14,496 feet). Farther south elevations decrease to about 6,500 feet where the Sierra Nevada province adjoins the Cali- fornia Coast Ranges near Tehachapi Pass, nearly 100 miles from Mount Whitney. Because of the gentle ascent from the Great Valley, the western side of the Sierra Nevada does not present a particularly imposing spectacle, though the crest peak.s, in the highest part of the range, stand out in striking fashion. Part of the ea.stern side, on the other hand, is one of the most imposing mountain escarpments in the world. The northern section is not impressive, for it is lower and is split into minor ranges branching off in a northerlj- direction from the main range. From near Lake Tahoe southward the ea.st front is higher and less broken. It rises about 6.000 feet above Mono Lake, 10,000 feet at the head of Owens Valley west of Bishop, and more than 11,(K)0 feet near Mount Whitney. Then as the range decreases in height farther south, the escarpment lowers. In the Owens Valley section in particular, the eastern face appears to be an almost vertical declivity towering above a rather even lowland. This illusion is dispelled, how- ever, by actual measurement of the slope of the front which in feV places exceeds 25 degrees. The highest section is immediately west of Lone Pine. From there Mount Whitney is visible, but elsewhere in Owens Valley this peak cannot be seen since it is located at the head of a great canyon far back from the main front. The most conspicuous peak seen from Owens Valley is Mount Williamson, which stands out because of its particularly ragged form and its position more than a mile to the east of the main divide. Mount Langley is a somewhat lower peak but also presents an imposing appearance ; Lone Pine Peak (12,951 feet), which stands about 2 miles east of the main crest, rises directly above Owens Valley, and appears to be even higher than Mount Whitney. Climate Since the Sierra Nevada parallels the Pacific coast, it forms a gigantic barrier lying athwart the path of the prevailing westerly winds, which most of the time carry moist air from the Pacific Ocean over the continent. The Coast Ranges farther west are too low to rob the air currents of much of their moisture except at their northern end where rainfall is heavy. As the winds ascend Sierran slopes to elevations where temperatures are lower, condensation gives abundant winter and spring snow and rain. Most of the precipitation falls on .the western side increasing rapidly from about 4,000 feet and decreas- ing above 6,500 feet, according to the U. S. Weather Bureau, though Dr. Matthes puts the limit of heavy snow and rain at 9,000 feet. Below 4,000 feet the climate is .semi-arid but less dry than in the Great Valley to the west. Above 9,000 feet it also is relatively dry because of the heavy extraction of moisture below that level ; however, snow hangs much later in the year on the higher peaks because the longer duration of cold weather retards melting, the snow disappearing in June, July, or even August, and returning commonly in October. (13) 14 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 KiG, 8. Ensl face of the Sierra Nevada as seen frcnn (")\vens \'alley. Tbe boundary fault system lies immediately at the base of the ranee. In the foreground is part of the Owens Valley Kraben. Krosion has modelled the scarp into a series of det-p canyons, most of which are glaciated in their upper parts, separated by steep-sided narrow-crested ridces. J'halu by U'. C. Mendenhall. courtesy U. »S'. Geological Survey. Within the zone of heavy precipitation, depth of winter snow exceeds that in any other part of the United States except the Olympic Mountains in northwestern Washin<;ton, the northern part of the Cascade Ranpe farther east in the same state, and perhaps certain sections of the Rocky Mountains. Between elevations of 6,000 and 7,000 feet alonj; the Southern Pacific Railroad, the annual snowfall amounts to 30 or 40 feet with as much as 60 feet fallinj; in some years; at Norden Station (elevation 6.871 feet) the averajje yearly fall over a 34-year period is 34 feet. At Tamarack in Alpine County (elevation 8,000 feet), 73.5 feet of snow fell in 1906, the greatest amount ever recorded for the entire Sierra Nevada. Frequently there are 10 to 12 feet of snow on the "rround at a single time and in protected spots the pile may reach 30 to 40 feet deep. Again at Tamarack during the winter of 1906-07, 8.8 feet of snow fell during a single storm, another record for the whole of the range. Because the winds lose so much of their moisture as they travel up the western slope, relatively little pas.ses to the eastern side, though considerable snow does accumulate at high elevations on account of the long duration of the cold. As the winds descend the east slope, they are warmed and consequently are able to evaporate moisture from the ground. The lower eastern slopes therefore are quite arid, except in the section near Mono Lake where the range base stands 7,000 feet and more above sea level. In the northern Sierra Nevada, the crest is con- siderably lower and more moisture is carried over to the eastern side, though again the lowest slopes are quite dry. Dry summers are characteristic of the range. Little rain falls for periods of two or three months, but occasional thunderstorms occur, which generally are of short duration. Most of the streams draining the range run roughly at right angles to its trend, that is, they flow south of west on the western side and north of east on the eastern side. There are some exceptions; for example, part of the course of the upper Kern River, the head of the Middle Fork of the San Joaquin River, Granite Creek and Chiquito Creek which parallel the crests of peaks. Because the divide between the eastward and westward flowing drainage is roughly the crest of the range, eastern streams are short and western are long; most of the ea.stern streams are comparatively small because of less available supply of water, and most disappear either within the lower parts of their canyons or very quickly after they emerge onto the desert basins at the base of the range. The principal exception is the Truckee River, flowing from Lake Tahoe and emptying into beautiful Pyramid Lake which lies in a desert basin more than 30 miles northeast of Reno. Some streams flow into Mono and other lakes in the section where the range base is at highest elevation, and Owens River, fed by Sierran tributaries, flows southward into Owens Lake. The heavy concentration of precipitation on the western slope of the Sierra Nevada gives its streams much greater volume, though there is notable fluctuation caused by the dry season during summer and fall. The western streams, with the exception of the Kern River, are tributary either to the San Joaquin River in the southern part of the Great Valley or to the Sacramento in the northern part. These two trunk rivers join not far from Carquinez Strait, the single opening in the mountainous rim surrounding the Great Valley, and flow into San Francisco Bay. The Kern River is kept from joining the San Joaquin by a great barrier of sediment in the southern part of the San Joaquin Valley and flows into Tulare basin formerly occupied 1952] SIERRA NEVADA 15 by a large, shallow lake, most of which has been drained to develop agricultural land. The principal rivers flowing down the western slope, named in order from south to north, are the Kern, Kaweah, Kings. San Joaquin, Tuolumne, Stanislaus, Mokelumne, American, Yuba, and Feather. In the upper reaches of the range, these streams are formed by the union of large as well as small tributaries, so that we find the Middle and North Forks of the Kings, and similar divisions of the others. Because of the high elevation of the Sierra Nevada and sufficient slope in both directions from it. the main streams and their tributaries have cut narrow canyons. On the eastern side, the gorges are deep to the base of the range, but on the western side, the lower part of the range has quite gentle slope and consequently valley depth becomes much less. Some of the canyons in their headward parts range from 2.000 to 7,000 feet deep. The Tuolumne and the Kern, for example, are 4,000 to 5,000 feet deep in places, and the Kings and some of its tributaries measure 6,000 to 7.000 feet. On the western slope, the canyons are separated by considerable stretches of rolling upland, while between the gorges cutting the steeper eastern side, there are sharp-crested, narrow ridges. Evolution of the Mountains Mountains and mountain ranges are evolved in four principal ways : (1) by deformation, which is responsible for the principal eminences of the continents and larger islands; (2) volcanic action, which has produced some of the most conspicuous and splendid peaks of the lands and the only type of mountains rising above sea level from the floors of the very deep oceans; (.3) erosion; and (4) deposition. Volcanic mountains are formed either by deformation of the surface as volcanic rock is forced into the outer part of the earth, or bj- eruption, which builds volcanoes and plains on the surface. Streams are principally responsible for erosion mountains, which in regions high above sea level may be mighty features of the relief. Deposition mountains are better termed hills and ridges; generally they are quite low, though some sand dunes rise a thousand feet above their base. In terms of the length of earth history, mountains and mountain ranges, the most conspicuous features of the landscape, are relatively ephemeral, being built at various times and then destroyed. At many places in the earth, there is record of ranges great and small which have been worn down to rolling plains, with perhaps a few higher eminences, and then buried by hundreds of feet of debris deposited partly below and partly above sea level. The development of principal mountain ranges either by deformation or volcanic action is a revolu- tionary event because of the profound changes in rocks, rock structures, and relief which take place ; but, as with all revolutions, many or most of their effects are later wiped out. From time to time parts of many ranges may be rebuilt and their span of life thus increased, but finally even these rejuvenated sections are subdued and their former presence is proved only by certain rocks and rock structures which remain. Deformation mountains are of three types, the principal being fold-fault ranges evolved by compression of long, narrow belts of the earth's rocky shell with consequent abundant folding and faulting. The major and most of the minor ranges of the continents and large islands are of the fold-fault variety, and some very important groups rise from the floor of the shallow ocean, as for example the great island galaxy off the west shores of Asia and Australia. Also, there are fold mountains, which are more or less simple anticlinal domes, usually of small size and moderate height, like the Kettleman and Elk Hills in the southwestern San Joaquin Valley. Fault mountains are blocks of the rocky shell bounded by faults along which they have been elevated, generally with some tilting. The Klamath Mountains, the Sierra Nevada, the Transverse and Peninsular Ranges, and ranges of the Basin-Ranges province of eastern and southeastern California were originally fold-fault mountains, but they were built so long ago that they have been re-elevated on various occasions after erosion had greatly modified their initial topography. The Coast Ranges, on the other hand, are fold-fault mountains which have been created during the last half million or million years. Evolution of the Sierra Nevada started perhaps 120 or 130 million years ago, when, in the late part of the Jurassic period, the western half of a great debris-filled trough or geosyncline was crumpled into mountains. The oldest rocks known from the Sierra Nevada belong to the Silurian period and are about 330 million years old ; but there is plenty of indirect evidence, though not in the Sierra itself, which suggests that the geosyncline existed long before. The youngest forma- tions involved in the deformation are late but not latest Jurassic, and were laid down in an ocean. Therefore it is quite possible that the first ridges of the ancestral Sierra Nevada appeared as islands projecting above this sea and later were welded into more continuous land. Compression was intense, so that once-horizontal layers are now steeply inclined and broken by great numbers of faults. Magnificent sections of the formations showing both sedimentary and volcanic rocks may be seen along Highways 40 and .50 traversing the Sierra Nevada, along Highway 24 following the canyon of the Feather River, and along Highway 120 leading from Mariposa to Yosemite National Park. There are of course good sections in many other places, most less accessible. How far the belt of Jurassic deformation extended is not definitely known. Some believe that it included most of California, western Nevada. Oregon. Washington, and much of British Columbia, even extending into Alaska and Lower California. Others think that con- siderably less territory was affected. Much of the belt has been very deeply eroded since the deformation, covered by deposits of later age, and broken to pieces by more modern faulting. 16 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 Those who have studied the Sierra Nevada think that the Jurassic fold-fault mountains were not particularly higrh — perhaps 6,000 or 7,000 feet maximum. Prior to the building of the Sierra Nevada fold-fault ranges very different geofrraphy existed. West of the present California coiist there was a long land area or .series of land areas known as Cascadia which extended for some distance into the eastern part of what is now the Pacific basin. Until late in Cenozoic time, Cascadia was the principal erosion area in this part of America, for it stood higher than most of the land stretching off to the east. This picture strikingly contrasts with that of the present, for Cascadia no longer exists and the great mountainous belt from the Pacific Coast to the Rockies has become the principal center of erosion. Streams flowed down the eastern slope of Cascadia either across lowlands which lay at its base or into shallow oceans which spread from time to time over these plains. For a very long period, the low country fronting the land now gone was a basin of deposition, though at times accumulation of sediment was inter- rupted and erosion modelled the deposits which had formed. Also there were important volcanic cycles when immense quantities of lava were poured out and fragments were violently blasted from volcanoes. Part (if these eruptions occurred below sea level and part above. This com- plex history is recorded in the multitude of rock layers and rock ma.sses found in the mountain ranges of the state ; the time involved extended from before the beginning of the Paleozoic era to the end of the last epoch of Cenozoic time, very likely including more than a billion years. Probably a shallow trough-like depression was first formed by de- forni.1t ion along the margin of the Ca.scadian highland. This depression was enlarged and deepened by the load of .sediment accumulated within it, which generated stresses in the weak zone below the crust, causing solid outflow of material from beneath the belt of maximum deposition. Eruption of volcanic material onto the surface within this belt also aided evolution of the trough. Eventually thousands of feet of sedimentary and volcanic deposits were formed. The sediments and remains of life buried within them show that most of the deposits were accumulated under the ocean which in few places was deeper than 600 feet at any time and over most of its extent was much shal- lower. From this evidence it is clear that, while the base of the trough sank many thousands of feet (the total thickness of the deposits is not kno«ni but certainly exceeds 30,000 feet in many places), the upper surface when below sea level sloped gently from the water's edge to very shallow depths. This was part of the continental shelf, which is the continuation of land under the ocean to where slopes increase and lead to the floor of the deep ocean. When the shelf rose above sea level, it rarely stood more than a few hundred feet high. A sediment-filled trough of huge dimensions evolved in the fashion described above is called a geosyncline. Over the continental interior east of the geosyncline deposition of sediment was much lighter and the surface of the rocky shell in con- sequence was not depressed so far. As weathered rock was removed from Cascadia, that land was gradually lowered, but from time to time, deforming forces elevated it, accelerating the erosive proces.ses and increasing the ruggedness of its relief. Some sediment came into the geosyncline from other bor- dering lands, but the coarseness and mass of the deposits adjacent to Cascadia clearly prove that region to have been the prime source of the debris. Geological evidence shows that accumulation of sediment and vol- canic material in a geosyncline continues, though not without inter- ruptions, for tens or even hundreds of millions of years. Fossils present in strata in the Sierra Nevada and in other California mountains clearly show a span of about half a billion years, and there are rocks long antedating these strata containing indirect evidence of life but no actual fossils. Deposition in a geosyncline is always voluminous but never continuous. From time to time the sea bottom is lifted out of the ocean to form low plains which suffer some erosion though they also may receive a veneer of continental sediment or volcanic rocks. Proof of such interruptions is clearly shown in breaks separating the various formations exposed in the mountains. Although deposition in a geosyncline may go on for an immensely long period, it eventually ends; these troughs are weak belts in the crust because they contain so much unconsolidated or poorly consoli- dated debris and consequently they are rather easily deformed. Even- tually the trough yields to the stresses constantly at work in the earth and begins to buckle and break. In a large section of California this happened more than a hundred million years ago. The rocks were folded into great arches called anticlines and troughs called s)/nclines; also they were broken apart by faults of various sizes along which minor or major dislocations occurred. The architecture of the earth in this region was revolutionized, for, previous to the deformation, most of the rocks had been more or less nearly horizontal sheets. The growing ridges were upfolds and blocks bounded by faults and between them lay basins or troughs which were downfolds and fault blocks. Such a mountainous complex is called a fold-fault system. Sections which have been re-elevated in recent time are the Klamath Mountains of northwestern California, the Sierra Nevada, part of the Tran.sverse Range? east of Los Angeles, the Peninsular Ranges in the southwest corner of the state, and some of the fault block ranges lying beyond all of these mountains and extending across the Nevada border. 1952] SIERRA NEVADA 17 The deformation of this belt did not proceed without interruption, for there were times of frreater activity separated by times of relative quiescence. None the less, over a relatively short jjeolojrical interval — a few million years — in the later part of the Jurassic period, the building of the initial ranges was completed. The height of these mountains is not kno\m, but it was considerably less than that of the highest part of the Sierra Nevada today; the principal peaks may have stood 6.000 to 7.000 feet above sea level but probably not much more. During the disturbances resulting in the deformation of a geosyn- cline into mountains, major changes go on within the heart of the folded belt. Not only are the rocks bent and broken by the stresses exerted upon them, but those at some depth below the surface are metamorphosed ; that is. they are partially or completely reerystallized. and new minerals and structures develop. Furthermore much igneous activity is initiated. The igneous mechanism is extraordinarily compli- cated and may be contained entirely below the surface as appears to have been the case during the deformation which produced the Jurassic mountains in California. There is no field evidence so far discovered that surface eruptions took place during this time, although there had been many before the folding began. As has happened in so manj- similar settings, an enormous body of granitoid rock developed a mile or more below the surface. The folded belt undoubtedly was invaded by liquid rock which evolved at still greater depth, but considerable sections of the granitoid mass appear to have been formed by the remaking of other rocks by volcanic gases and solutions into new material which cannot be distinguished from that formed during the crj-stallization of a molten mass. This process of remaking other igneous * and sedimentary rocks into rocks definitely of granitoid character is called granitization. Igneous action, like deformation, was not continuous but rather occurred in a series of waves, for many bodies of granitoid rook have been differentiated in the Sierra Nevada, all apparently belonging to the same volcanic cycle. Some bodies transgress others, showing that they are slightly younger. In other words, the total body which is called a batholith or deep-seated igneous intrusion, was formed over a considerable time and consists of many parts, only a few of which have so far been separated. Granitoid rock like that composing the Sierran batholith includes true granite and other rocks closely associated in chemical and mineral composition. They have been formed probably at depths of at least a mile below the surface. For this reason the growth of crystal grains has been relatively slow and the rocks are generally medium- to coarse- grained. They are characteristically light colored, grray being the • Igneous rocks have soltdifled from molten masses. Sedimentary rocks have been formed chiefly from waste products of other rocks or from organic debris, or by chemical precipitation in water. c dominant shade. The rocks are made to a very large extent of two light-colored minerals, one called quartz and the other feldspar. Quartz is a mineral of simple composition, always being composed of one part of silicon and two parts of oxygen ; feldspar, on the other hand, is represented by several varieties, each much more complex in composition than quartz. In most granitoid rock, there is a distinctly minor quantity of the dark-colored mineral grains that give the rock its pepper-and-salt appearance. These dark-colored minerals contain various proportions of iron and magnesium while the light-colored varieties do not. The volcanic cycle apparently started during the deformation in the late Jurassic and continued after it. possibly into the earlier part of the Cretaceous period. When finished, a gigantic rock com- plex was evolved entirely under the surface. It probably extends throughout the folded belt and, in the Sierra Nevada at least, evi- dence derived from study of earthquake waves indicates that it is 10 to 12 miles thick. Round about the margins of this great mass, the covering rocks were intensely metamorphosed into new types, the metamorphic eflFects decreasing with distance from the batholith. The granitoid rock is very resistant as are most of the metamorphic rocks. Closer to the surface where the metamorphism did not reach and where the rocks of the geosyncline were less thoroughly consoli- dated, the materials were weaker and more easily weathered and eroded. The development of the granitoid core and its associated zone or aureole of metamorphic rocks thus increased the strength of the heart of the deformed belt. The Sierra Nevada of today is very different and much more majestic than the ancestral ranges of Jurassic time. Instead of being a series of elevated ridges separated by troughs and basins, it is now a gigantic tilted fault block so huge that within it are a number of minor ranges, each of considerable magnitude. The eastern face of this immense block is a scarp developed along a multitude of fractures called faults. A fault is a break in the outer earth along which the adjacent blocks slip past each other. The western side of the Sierra Nevada is a complex of landscapes evolved during the long interval since the birth of the original fold-fault system. Understanding of the many changes which have occurred in Sierran landscape requires a brief analysis of what has transpired since the mountains first appeared. Because the size of the range is so great and its geologj- so complex, at present it is possible only to outline the principal steps in the story. Between the end of the first rise of the system and the close of Cretaceous time, nearly 60 million years elapsed, but of this interval there is only the scantiest record. By the beginning of the last or Cenozoic era. another 60 million years a^o. the ranges had been so eroded that they were quite inconspicuous, and in places the ocean 18 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 spread to their western base. The land was so low that winds sweeping inland from the Pacific Ocean did not lose most of their moisture over Sierran slopes as they do todav. Instead they provided enoujjh rain for hundreds of miles inland to permit the frrowth of a luxuriant vefjetation which could not possibly exist over most of the reyrion under the arid conditions that now prevail. This is proved by the character of fossil plants found in deposits belonging to that time. During the Eocene, first epoch of the Cenozoic Tertiary period, the region was bowed upward along an axis approximately that of the present Sierra-Cascade system. A low mountain barrier was created and fairly deep gorges were cut into the rising hills. The shore line still remained close to the present western base of the Sierra Nevada. During Miocene time, however, the mountains had been elevated sufficiently to cut off most of the moisture and the region to the east became arid. Much more vigorous disturbances marked the end of the Miocene and the beginning of the Pliocene epochs, for the Sierra Nevada was elevated considerably and became strongly unsymmetrieal in form with a broad western and short eastern slope. There was much fault- ing and associated volcanic activity. Faulting conspicuously increased the boldness of the eastern slope, especially north of Mono Lake where several long range spurs were developed. Between one of these spurs, the Carson Range, and the main Sierra Nevada, a section sank, evolv- ing the basin now partly occupied by Lake Tahoe. Faults also broke the western foothills, so that the long slope in places descends in a series of abrupt steps. Then followed a period of relative calm during most of Pliocene time and erosion dominated over elevation by deformation. Con- siderable changes in the landscape of the range resulted. But the quiescence was not enduring, for at the end of the Pliocene and con- tinuing into the earlier part of Pleistocene, the deformation was vigor- ously renewed. These movements lifted the Sierra Nevada approxi- mately to its present height and the country to the east also was elevated .so that Owens Valley stood about 9,000 feet above sea level, considerably above its present maximum height. Most of the elevation took place before the beginning of the Pleistocene or Glacial epoch so that the snow and ice which remained year after year was bulky enough to generate the slowly moving ice masses called glaciers. Rec- ords of profound glaciation recognized as belonging to the earliest part of Pleistocene time have been found, hence the region must have been nearly as high as now for, even during the climaxes of the glaciations, the snow line in the Sierra Nevada apparently did not lie much below 11,000 feet. Most convincing evidence left by an early glacier is provided by the debris deposited on the mountains west of McGee Canyon. The principal glaciers on the cast side of the Sierra Nevada, because of the steepness of its slope, were vnllcy glaciers, that is they formed in valleys or canyons which already had been eroded by rivers. Moraines are great heaps of unassorted rock fragments, some of which are very large. Valley glaciers leave two principal types, the more common side moraines formed from debris frozen in the sides of the ice and carried on its top, and terminal moraines, compo.sed of rocks and fine sediment pushed in front of the ice and melted from its end. The McGee moraine, which has been identified as belonging to the first of the four glacial stages, ends abruptly at the great eastern scarp, and stands about :?,000 feet above Long Valley at the base of the scarp. Study of the moraine .shows that its glacier followed a rather flat, shal- low valley high in the Sierra Nevada, proving that McGee Canyon anfl the scarp into which it has been cut did not exist. Moreover the McGee moraine, in spite of some later damage, obviously was about as large as the moraines of the later glaciers. This, together with much other evidence, indicates that the Sierra Nevada had about as large an ice mantle during the early Pleistocene as it did later in the epoch. Abundant evidence indicates that the ea.stern scarp does not owe its height to elevation along faults at the base of the range. Rather, long, narrow blocks sank, developing Owens, Carson, and other valleys immediately east of the range. These depressed masses were broken into great numbers of fragments by lesser faults and along them there has been much volcanic eruption. On the other hand there is not much evidence of shattering within the main mass of the Sierra Nevada at the time of the last disturbance. Other proof that the depressed blocks have sunk is afforded by the slant of the lowlands toward relatively fresh fault scarps. At the base of the range and against these scarps is either wet, swampy land or lakes, such as Owens Lake, which is deepest near its western shore against the highest section of the Sierran scarp ; the wet meadows sloping to the range base near Bigpine; Mono Lake, lying next to a steep scarp and deepest on its western side; the marshes in Carson Valley which lie directly beneath fresh fault clilTs at the base of the Carson Range ; and Honey Lake at the far northern end of the scarp. The giant scarp, without doubt the most magnificent example in America, thus is not much over 800,000 years old and has been increas- ing in majesty as the bordering, eastern blocks have continued to sink. It has been considerably battered, for a multitude of deep gorges have been cut into it and the upper parts or even the entire length of many of these gorges have been glaciated. Faulting at the base of the range has occurred intermittently, some of it being very recent. Very probably there have been differential movements along the faults so that the Sierra Nevada has risen some- 1952] SIERRA NEVADA 19 what but its height has not been yrreatly increased over that developed by the late I'liiH'ene-early I'leistocene deformation. Farther east in the Basin-Ranjres province, similar faulting sepa- rated formerly continuous stretches of landscape, raising some to form ridges and ranges, and depressing others to form troughs and basins. Some of this faulting to the east started as early as Miocene time, some is of much later, and some is going on actively today. Of the blocks which were isolated by faulting, the Sierra Nevada is by far the largest. It must not be supposed that the great fracture systems bounding the blocks were developed quickly or that the immense dis- locations were accomplished in brief intervals. Rather, the faults grew in length and complexity and the individual movements along them were relatively small, a few feet to a few score of feet. Furthermore, there is no evidence that dislocations occurred along the entire length of a fault system at the same time. There is much additional information about the growth of the Sierra Nevada contained in F. E. Matthes' entertaining book. The Incomparable Valley, compiled after his death by Fritiof Fr>-xell. Much of the foregoing story of the later history of the range is sum- marizetl from this volume. As the up-arching of the Sierran region went on. the maximum elevation was attained in the northern half of the southern section. Very possibly this height is being slightly increased while the adja- cent valley blocks are still sinking. Eastern Fault Scarp In places, as along most of the western side of Owens Valley, the principal fault bounding the eastern base of the Sierra Nevada appears to be relatively simple and most of the movement was concentrated along it. Along most of the range, however, intersecting fractures are indicated by salients and re-entrants like those west of Bishop near the head of Owens Valley. Also, there are many faults parallel to the main system along which blocks have sunk less than the valley blocks, producing a terraced front. South of Mount Whitney, there seems to be no actual evidence of faulting along the base of the range, but its form definitely suggests that this portion as well is a tilted fault block. The fracture zone appears to have been completely buried by great masses of sediment carried from canyons worn into the fault scarp. The faulting in this southern section appears simple for there is little evidence of the step-blocks that produce a terraced front. The great scarp is highest and most clearly defined from Olancha at the southern end of Owens Valley to Independence, for the abrupt descent from the crest of the range is not broken by any foothills. Striking faceltd spurs, the truncated ends of ridges broken by the faulting, may be seen south of Owens Lake but are larger and bolder southwest of Independence. The east .slope of Mount Williamson, dominating peak of the Sierra Nevada visible from this part of Owens Valley, is a huge triangular facet into which have been cut three lesser facets. Each of the three rises to a height of 10,000 feet, below which the range slope shows the marked over-steepening characteristic of recently developed fault scarps. West of Independence, the Sierran scarp changes in contour. The base exhibits salients and re-entrants formed by granite foothills pro- truding through the deposits at the base of the range and apparently lying against its main mass along the principal fault system. These foothills doubtless are step fault blocks which either have not sunk as far as the Owens ^'alley graben or have not been elevated as far as the main block. Farther north toward Bishop, fine triangular facets again appear indicating that the boundary fracture is a simple one. As far north as Birch Mountain, the eastern side of the Sierra Nevada presents unmistakable proof that it has been developed by profound dislocation along the fault system, but from there northward to Bishop Creek, the evidence is less convincing. Long, straggling foothills project into Owens Valley and merge with the main mountain mass. In this section, there probably are a number of parallel faults, with the dislocation distributed more or less equally along them through quite a wide zone. There has been sufficient erosion to obscure most evidence of faulting, a common occurrence where this step structure is present. In the ^^cinity of Bishop Creek, the fault system is offset to the west about 8 miles in a manner characteristic of the area farther north. The scarp here shows the same abruptness and simplicity as near Owens Lake ; the best development is the extraordinarily steep slope facing Round Valley. The fault indicated by this declivity, if pro- longed southward, would coincide with the canyon of the South Fork of Bishop Creek, which is conspicuous among the canyons on the east side of the Sierra Nevada in having an approximately northward trend. There is good evidence that this canyon has been developed by faulting. The fact that an advanced erosion surface standing 2,500 feet above the river in the bottom of the canyon is at essentially the same elevation on both sides of the canyon indicates that this gorge, if evolved by faulting, is a rift valley: that is, its floor is a block which has sunk between two faults. An oiled road leads up this valley from Bishop to the beautiful glacial lake country on the east side of the high Sierra. Multiple displacements along both sides of Truckee Meadows have formed this (jrabeii,' which has hill areas projecting above its surface. North of the Truckee River, the faulting and therefore the Sierran front change notably. Displacement along the boundary fault dimin- ishes, the faulting apparently is multiple in many places, and north- ward-trending ridges project from the main mass of the range. • A graben is a basin or trough formed by sul>sidence of a block or blocks of the earth's crust along faults. 20 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 >?P^> —', -^^$=0^ Vk.. 4. Lake Talioe (background). Fallen Leaf Lake (left foreground) occupies a basin formed by a terminal moraine left by a valley glacier that came from the Pyramid Peak area. Photo hy courtety U. S. Army Air Corps. 1952] SIERRA NEVADA 21 Fig. 5. Section showing fault scarp north of Kern River, east of Bakersfield. After G. K. Gilbert, V. S. Geol. Surrey Prof. Paper toS. p. 88. Tahoe Basin The outstanding example of the effect of faultinl Creek ; CR. Cathe<>' >>-^ tv-'-V Fio. 9. Itiril's-pye view of thr Yosemife Vnliry ns it probably was in the nmuii- tain-vnlley sta^e. after it had liefn (ieeponed about 700 feet by the Merced River in consequence of the tirsit ;;reat uptiltiiiK of the Sierra Nevada. The valley was flanked by upbiiuls. and Ribbon (.'reek, Ynseniiie f'reek. Sentinel Creek, Britbtlveil Creek, and Meacbiw Uronk cax-aded steeply fmni the mouths of hantjinK valleys. Tenaya Creek, Illibuiette Creek, and Indian Creek, however, had cut their valleys down to the level of the Merced, The re;;ion was covered with mixed forests containing sequoias. A/rer F. E. Matthes, V. S. Geol. Survey Prof. Paper J60, p. 41. MLF Fig. 10. Bird's-eye view of the Yosemite Valley as it probably was in the canyon stage, just before it was invaded by the glaciers of the ice age. The valley had been cut 1,300 feet deeper by the Merced River, in consequence of the second great up- tilting of the Sierra Nevada, and had a V-shaped inner gorge and two sets of hanging side-valleys. Illilouette Creek and Indian Creek now also made cascades, but Tenaya Creek and lower Bridalveil Creek had cut gulches down to the level of the Merced. The region was covered with coniferous forests adapted to a temperate climate with cold, snowy winters. Ajter F. E. Matthes, V. S. Geol. Survey Prof, Paper 160, p. ^8. 1952] SIERRA NEVADA 25 ticularly in the southern part of the range. Naturally they have suffered much damage by later erosion and in parts of the Sierra Nevada have not been detected, though more thorough study may reveal them. In late Miocene and early Pliocene time, the northern third of the Sierra Nevada at least became a great volcanic field. Frequent explo- sions erupted great quantities of coarse and fine debris of andesitic lava and a considerable number of flows also were poured out. Jlost of the centers of this activity lay east of the present Sierran crest but some have been recognized in the crest region. The fragmental deposits for reasons that we do not know became waterlogged and moved as great avalanches down the valleys piling one upon another as the vol- canic cycle continued. Even after much erosion in the crest region there are sections of these volcanic mud flows 1.500 to 2.000 feet thick. In spite of the relatively low slope of the valleys, the mudflows were liquid enough to move through them and in some cases passed the base of the Sierra, spreading onto the eastern side of the Great Valley. The valleys in the range were well filled and some of the lower ridges were over- whelmed but the higher eminences projected above the volcanic sur- face. Apparently the mudflows formed a flat area with masses of bedrock protruding through it. Certainly this landscape covered much of the northern third of the Sierra Nevada but how far south it extended cannot be determined as the amount of erosion which has since occurred is difficult to estimate. The suggestion is strong, how- ever, that most of the southern section of the range lay beyond the limits of the volcanic activity. After the close of the volcanic episode in the earlier part of Pliocene time, the Sierra Nevada which then probably was much broader than today was elevated about 3,000 feet. The deformation doubtless was not continuous, but was concentrated in certain intervals with others of relative quiescence between. The elevation of course increased the slopes of the range and the streams were correspondingly invigorated. Where they had started to flow on the volcanic surface, they cut through it into the bedrock, while others in the broad valleys cut young gorges below the surfaces of the terraces which they had eroded prior to the elevation. These new canyons were 1,200 to 1,500 feet deep by late Pliocene time. The upper part of the Kern River, flowing parallel to the crests of peaks, reached maturity while the streams descending the steeper western slope were still young, at least through- out most of their length. The Kern therefore began to widen its valley, destroying much of the terrace which had been cut before the early Pliocene elevation. Remnants of the broad Miocene valley are pre- served along the sides of the peaks of both eastern and western crests but are not particularly conspicuous; none the less it is possible to reconstruct the valley approximately. Remnants of the Pliocene mature valley are finely preserved as flat areas in the Mount Whitney region. Thus there is striking contrast between this longitudinal mature valley and the dominantly young canyons of the same cycle on the western slope. The Pliocene landscape, which is a much more \-igorous one than the Miocene, has been termed the mountain valley landscape. The highest peaks of the Sierra Nevada at this time seem to have stood about 6.000 to 8,000 feet above sea level, but most of them had been evolved during the still earlier erosion cycle. The late Pliocene and early Pleistocene elevation of the Sierra Nevada and the region to the east caused a sharp increase in the gradient of the streams and therefore in their downcutting power. They began the incision of the great canyons like the Yuba, the American, the King, and the Kern. Since the range probabh- is sti.ll rising to some extent, the canyons are still being deepened ; they are narrow. V-shaped gorges with bold, ragged slopes rising abruptly from the sides of the streams, except where the canyon form has been modified by glaeiation. as in Yosemite Valley. Although these great gashes have been speedily eroded because of the considerable increase in slope of the western Sierra Nevada and the abundance of water available, the elevation has been recent enough so that broad stretches of the older landscape remain between them, making it possible to read at least part of the chapters of later Sierran hi.story. The canyons naturally are deepest in the central, highest part of the range ; to the north and the south they are less conspicuous, but are nevertheless deep gorges. This stage of landscape development, which started on the western side of the range in late Pliocene time is called the canyon stage. Unlike the others, it is also represented on the eastern side, but there the gorges have been slashed into the great fault scarp, most of which was formed after the first glacial stage of the Pleistocene epoch. Remnants of the older landscapes are not present on the eastern side of the Sierra Nevada except in a few places where they have been preserved on step-fault blocks. On the eastern side the landscape is mostly a succession of deep gorges separated by narrow crested ridges. GLACrATION Except for the great fault scarp on the east side of the Sierra Nevada and Tahoe basin with its beautiful lake, the most startling features of the range are those which have been modeled in part at least by glacial ice. snow avalanches, and frost wedging with associated fall of blocks of rock. To understand the extraordinarj- work of ice in sculpturing the high Sierra Nevada requires a brief discussion of the last chapter of earth history, the Pleistocene epoch of Tertiarj- time or, as it is com- monly called, the Glacial epoch. During the last great marine period of earth history, the Cretaceous, extensive seas prevailed, and the climate over most parts of the earth 26 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull, 158 was much more equable than today — a characteristic of the iropor- practically all of the ice disappeared from the earth. Areas outside tant marine intervals. Such climate continued over somewhat reduced of the polar regions were strikingly changed climatically during both areas and with some modifications for the next 15 or 20 million years; glacial and interglacial times. but, as the continents gradually enlarged, far-reaching climatic mt . ^^ ^iii ^ lu u 1^1,111,,, ..^ a, • „i,,. V ,; _ v„ , , „„ -J J u • £ J Probably the beginning of the epoch was not more than 2 million regions which earlier had been so widespread were becoming confined , , m, > .. p ■ , ■ , , . , . , ._,.., . ,. ., J ^, r 11, » T iu years back. Uie lengths ot the glacial and interglacial stages also arc to a relatively narrow belt north and south of the equator. In the ■' , . , ..,,,, ,,.,,, .... <•->"»<• extreme north and south and at high altitudes, cold blanketed larger uncer am. Assuming that the epoch started about 1 million years ago, and larger areas. In this progressive climatic change the rise of the *^« following chronology has been suggested : continents to abnormal heights above sea level and the extensive First glacial stage 1,000.000-900,000 years building of mountains which had characterized late geological time ^'"" interglacial stage 900,000-700,000 years played an important role. Other factors, not vet determined, were also Second glacial stage 700,000-600.000 years undoubtedly involved. " Second interglacial stage 600,000-325,000 years .„^ . „, . , , , .„. , Third glacial stage 325.000-22.->,000 years When the Glacial epoch started a million or two years ago, the area Third interglacial stage 225,000-100,000 years over which polar climates prevailed rapidly expanded in high and p„„^,^ ^,^^5^, ^^^^^ 100,000 years to present moderately high latitudes both north and south-of the equator and at a. Culmination 55,000 years high altitudes. Where the climate was glacial, the cold was so intense ^- Beginning of last principal ice retreat 25,000 years that a lasting cover of snow and ice began to grow, since all of the snow ai'ciimulated during the colder months could not be dissipated during the slightly warmer days and weeks. This blanket gradually increased in thickness, and from the margins of the larger masses, moving fronts or tongues of ice called glaciers were projected. Beyond the glacial areas and regions were stretches of the slightly less hostile tundra climate where snow and ice melted during a few warmer weeks 'S^V^ of the year, and frozen ground was thawed to depths of a very few feet. Below this shallow melt-zone, ice extended for scores or even hundreds of feet, particularly in the higher latitudes of the northern hemisphere and there even today tundra regions are very extensive. ^ N.''^Vk^\J!*nPWnHB\.ii ^i'W -r- , ,. i^»- - Under the permanent ice, water also was frozen in the rocks and L- ""x ^''^ ^'J^U-^^''^9!^^-.M'^f^^^^''^^kf^MtK9fi»iv^' remained so throughout the year. ^^'^'^v^ij^^BBB.^ ■'^!l>*^!i5%^* * '*'■'* "»' **- "A During the Glacial epoch, the climate fluctuated notably over much v V^*' ♦"V^^sBS^J^^ " ''?'.'' of the world. Four times the glacial areas expanded, increasing the ^ ■ ' ' , ^^^T*^ extent of the lasting mantle of snow and ice until the maximum _ '^ rvjiife-* coverage amounted to about 32 percent of the land above sea level. ■ ^" These four episodes are the glacial stages, in the last one of which we * S V ^ij^" "- *"UfKl^^KK ^ live. Then, for reasons as little known as are the causes of their expan- ,., ,, ..., , ., t.- ., „ , , , , , , • . ., ' * III.. 11. I li'* v'lii^' ''i'nyon of the feather Uiver hns t).', Ml (l..|i!v eroded into the sion, the areas dominated by polar climate shrank, glaciers and other Su-mui i...ir,.tk as tiu- result of invigoration of .streams caused by tiie laie I'liocene masses of ice receded or disappeared, and warmer conditions developed ''"'^y i*iei«iocene elevation of the region. The form of ihi.s canyon i» typical (.f the i. i» ii. 1 J • 1 ,. ij • iu ■ c J.I. ' mu non-glaciated portions of all canyons in the range. /*Ao(o cour/cgu 0/ H'cjfkrn /*aci/ic over most of the land previously held in the grip of the ice. The Railroad. magnitude of ice recession during these interglacial stages is not known, but doubtless it was different in each as also was the magni- If the Glacial epoch includes more than 1 million years, the figures tude of advance during the four glacial stages. It is quite probable given above must be proportionately increased ; further studies also that, at least during the longest (the second) of the interglacial stages, may revise the proportions between glacial and interglacial stages. 1952] SIERRA NEVADA 27 Two facts, however, are well established. The j^lacial staiires are the outstanding features of the epoch, but the interfrlacial stages were of considerably greater length. Considering the small amount of ice on the earth in pre-Glaeial and interglacial time, the creation of the glaciers and other ice masses was rapid and on an enormous scale. As previously noted, the maxi- mum coverage included at least 32 percent of the land above sea level, and in addition va.st areas of the ocean were frozen to depths of a few feet or, in some places, as much as a few hundred feet. The la.st glacial stage, the one in which we live, witnessed the overwhelming of about 27 percent of the land, and of this area more than a third still lies beneath the snow-ice blanket. It is dear therefore that the present is a brief interval in the waning of a glacial stage, a fact not only evidenced by the extent and volume of snow and ice but also by the great areas over which climates still prevail which are not very far removed from the glacial and which could become glacial with a slight decrease in average temperature. The formation of snow and ice fields which last for long periods represents storage on the earth of water evaporated into the atmos- phere and later precipitated as snow. The principal evaporating basin is the ocean, though of course a certain amount goes from the waters of the lands. As the ice mas.ses grew during the glacial stages, the volume of the ocean gradually shrank. Sea level was slowly lowered and the land covered by shallow depths of ocean water emerged. It is believed that the maximum fall of the oceans when the ice reached its greatest extent and thickness was between 300 and 400 feet, whereas at the culmination of the last glacial stage it amounted to 250 or 300 feet. This caused a small increa.se in the size of continents and islands and the joining of some large and many small islands to the continents or to each other. For example, the water between Alaska and Siberia is so shallow that the above-mentioned lowering of the ocean united the two areas. The area of California increased somewhat as the ocean went down, but the continental shelf off the California coast is narrow in most places, hence the increase was not of much moment. The depres- sion now occupied by San Francisco Bay had a very different appear- ance during the last glacial stage at lea.st because the depth of water in the Golden Gate is about 381 feet and mo.st of the bay is quite shallow. Therefore when the ocean reached its lowest stand, the bay had largely disappeared and was not restored to material size until sea level had risen appreciably thus bringing the development of the present bay down to the last few thou-sand years. Four times during the Glacial epoch ocean level fell and four times it rose, though there appears to have been a slight drop in very recent time occasioned by a moderate chilling of earth climate and some increase of ice. A large volume of water is still locked up in the Green- land and Antarctic sheets and a much smaller amount in other ice masses. Calculations indicate that, if this ice disappeared, sea level would rise between 50 and 100 feet around the earth. This would submerge many exceedingly low areas along continental and island shores and low islands; also, drowning of the land would isolate certain higher areas as islands. The profound climatic changes which brought on and did away with the glacial stages naturally were felt far beyond the limits to which the ice expanded. In both hemispheres, though more conspicuously in the northern because of its greater land acreage, the belt of eastward moving storms with its cloudiness and precipitation shifted equator- ward as the glacial stages advanced toward their climax, spreading over many regions which are semi-desert or desert today and bringing greater precipitation over both lowlands and highlands. In more northerly and southerly lowlands and particularly in adjacent moun- tains, both rainfall and winter snow increa.sed. Streams multiplied or grew in volume ; lakes without outlets expanded, some developing outlets ; and great numbers of new lakes appeared. The changes were more notable in the poleward and higher parts of the regions arid today. It is clear that each maximum spread of greater humidity over the present dry regions coincided with the culmination of each glacial stage. This climate prevailed about 55,000 years ago. when the fourth glaciation reached its height. The present aridity has evolved prin- cipally during the last 25,000 years when the ice recession has been most rapid. Today desert climate prevails over about 35 percent of the land above sea level and vast areas are semi-desert. The very dry parts of western United States present a splendid record of this climatic change. Professor Flint of Yale University has shown that there are 128 closed basins in this region where evidence of 98 former lakes or expansions of existing lakes has been obtained. Only 8 basins have not yielded positive evidence of former lakes and 20 have been insufficiently studied to show whether lakes were present or not. The 98 basins contained 71 lakes, as some flooded more than one basin. Mono Lake, at the eastern base of the central Sierra N'evaila. was much larger and during the third glacial stage attained a depth of nearly 900 feet. Owens Lake at the .south end of Owens Valley in- creased notably in size. In the Mojave Desert section of the Basin- Ranges province there is record of many former lakes, some of goodly dimension. Panamint Valley held a large one, and another, more than 90 miles long and some 6tX) feet deep, lay in Death Valley, now one of the most arid regions of the world. The evidence of these former lakes and expanded existing lakes includes wave-cut cliffs and a.ssociated wave-cut terraces standing at various elevations along the sides of 28 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 ]Y« -^jL-2'* --^^^^^-^^s^e.-'-.- ■• - ■ - -ii«/>9' - •'JEf'a^'St^^- -^ '>&^^S^•^^■- Fio. 12. Vosemite roKinn fnun .Mt, Spem-.r. K>„lul,„u Has... in foreground. Mt. Huxley to left. Mt. Goddard to right. Photo bv Oeorge J. You„g. 1952] SIERRA NEVADA 29 the mountains apainst which waves pounded, topether with beach sedi- ments and other deposits laid down in quiet waters. It is true that, since the culmination of the last glacial stage about 55.000 years ago. the climate of the earth has become warmer and drier and the ice blanket has notably diminished ; but there have been fluctuations both in the climite and in the stand of the ice during even this interval. Neither the advance to the climax of a glacial stage nor its recession has continued unbroken. In very recent times there is abundant evidence of one of these fluctuations, for the greatest warmth and dryness of the fourth glacial stage was reached between 6.000 and 4,000 years ago. Since then, also with minor fluctuations, earth climate has become somewhat cooler and moister. Even as late as 500 B.C.. the general climate was warmer than today. This warm, relatively dry episode which began to wane so late in human history is termed the Climatic Optimum. The proof of the climatic change just referred to is both geologic and biologic. For example, in the Sierra Nevada it has been shown that the regional snow line was considerably higher than today, the average summer temperature also was higher, and the summer season was somewhat longer. This means that none of the small valley-head or cirtiue glaciers are remnants of former valley glaciers, as had long been believed, but are infants conceived during the cooler interval which started about 4.000 years ago. To judge from the speed with which these glaciers are now wasting, it seems impossible that they could have survived the greater warmth of the Climatic Optimum. The extreme youth of these glaciers also is shown by the freshness of the debris composing their moraines and by the fact that the moraines in some instances contain cores of glacier ice. Moraines of older glaciers, those born during the fourth glacial stage, are somewhat weathered and contain no ice cores. Certain lakes, like Owens in California, do not contain as much salt as they should if they were residues of larger lakes evaporated to their present size. Therefore it is believed that these lakes disappeared during the climatic optimum and have been recreated in the last 4.000 years. It is possible that most or all existing lakes in western North America may have had similar histories, but this has yet to be proved. Since the present Sierra Nevada began to rise only a little before the beginning of the Glacial epoch, it soon felt the effect of the increas- ing cold. The climate became more wintrj" and the higher parts of the range were blanketed by snow and ice which did not disappear during the slightly warmer months. As the glacial stages advanced, the snow- ice piles became thicker' and thicker until they generated glaciers, most of which moved down canyons already scored deep into the rocks by rivers. However, on the western side, the rolling uplands between the canyons provided sites for the generation of small and not particularly thick ice caps, most of which sent tongues into the canyons, adding to the glaciers already descending from cirques being eroded into the canyon heads. On the ea.stern side, where the snowfall was less, the valley glaciers were thinner and shorter and there was no room for ice-cap formation. However, tongues from certain caps on the western side found their way into the eastern canyons, as for example, in the Tioga Pass section above Mono Lake. In the relatively low, northern section of the Sierra Nevada, where the high peaks do not much exceed 6,000 and 7.000 feet above sea level, only cirque or valley-head glaciers and short valley glaciers were present. Since this portion of the range has received little geological study, ice effects are not well known. South of the Kern River where again the peaks are lower as they approach the terminus of the range at Tehachapi Pass, there was little or no glacial ice. The long section between these two parts, however, is quite different. Around Donner Pass, which is crossed by Highway 40. glaciers of the last stage measured 10 to 15 miles in length and apparently joined to form an ice field approximately 250 square miles in area. Donner Pass was overwhelmed by ice during each of the four stages, long tongues projecting both to the east and west. Toward the southern end of Lake Tahoe. where the peaks on the western side are 9.000 to 10.000 feet high, the later glaciers on the west side of the main crest were at least 20 miles long, the earlier ones shorter, measuring only 5 to 10 miles. So bulky was the ice mass that part of it was forced across the divide and this together with short valley glaciers developing on the eastern side descended into Lake Tahoe. Between Lake Tahoe and Yosemite National Park, the crests rise from 11.000 to 13.000 feet above sea level. So much snow fell in this section that, on the rolling uplands — remnants of the elevated ancient landscapes — a domed ice cap formed which ran along the trend of the range for about 80 miles and had a width of about 40 miles. Above this considerable ice mass only the highest peaks projected as lonely nunataks. From the cap, tongues flowed into canyons already eroded by rivers, and its volume was great enough to force some ice upward through low passes onto the eastern side of the Sierra Nevada. The largest glacier invaded Tuolumne Canyon and in the earlier glacier stages had a length of about 60 miles. The lesser ice of the last stage did not descend the canyon more than 46 miles. The Yosemite glaciers were the shortest of the tongues in the section under discussion, for most of the ice formed in a relatively small basin and there was only a modest contribution from the ice cap. Another considerable ice mass about 50 miles long and 30 miles wide developed in the broad basin of the upper San Joaquin River and there were adjacent masses in the basins of Dinkey Creek and the North Fork of the Kings River. The main body was not a cap like 30 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 Fig. 13. Ciriiuf ;;l;icior on Mt. M:u-Iure in the Sierra Nevada. Photo by O. K. Qilhert, courtesy V. S. Geological Survey. that in the Yosemite-Tahoe region, for it appears to have been formed by the union of several valley glaciers too thick to be contained in the canj-ons where they originated. In the last glacial stage, there was not enough ice to create such a field and the glaciers were held within tlieir canyons. The principal ice tongues in this area followed the Middle and South Porks of the San Joaquin River, starting from Evolution Basin and joining into a short trunk stream at Balloon Dome. In the Kings River drainage area, the canyons were so deep that the ice was held in them. The Middle and South Fork glaciers were the chief ones but the supply was insu(ficient to cause them to join so they remained separate streams. In Kaweah Basin, each tributary canyon harbored a vigorous glacier 5 to 7 miles long. The main mass of ice in this region, however, lay in a section extending from Tokopah Valley to the head of the Marble Pork of Kaweah River. The southernmost of the Sierran valley glaciers lay in the Kern River canyon. During the earlier glacial stages, the ice overflowed the canyon onto the surrounding bench lands which are parts of old valleys generated before the last elevation of the range. The glaciers of the last stage seem to have been confined to the Kern Canyon and its tributaries. The earlier ice was about 32 miles long, extending down to the vicinity of Hoekett Peak ; the last ice was about 7 miles shorter. Ilockett Peak appears to mark the southern limit of glaciation in the Sierra Nevada. Today, there are about 60 tiny glaciers in the high Sierra, the best known being two on Mount Lyell, a third on Mount McClure, and a I'ciurtli, the Palisade glacier farther south at the head of Big Pine Creek. All are true glaciers, though they are now shrinking, and, because of their small size, they move very slowl}^ They arc not rem- nants of earlier valley glaciers belonging to the culmination of the fourth glacial stage, but have been created during the slight upswing of the cold, known as the "little ice age." Prom evidence at hand, it appears that these miniature glaciers began to evolve about 4,000 \oars ago. Jlost of them lie in high peak cirques * facing north and northeast though some are on the north and northeast slopes of nar- row, comb ridges. In all cases, they are located where abundant snow is drifted by the wind and where they are protected from the sun by the great rock walls above. The upper part of the Merced River canyon in the Yosemite region was invaded by ice at least three times during the Glacial epoch. The Yosemite glaciers were formed by two principal tributaries, one descending Little Merced canyon south of Half Dome and Liberty Cap while the other followed Tenaya Canyon on the north side. The two streams joined about where Camp Curry and the Awahnee Hotel are now located and proceeded down the main canyon. The first two glaciers were much thicker and longer than the third ; little evidence remains of the initial stream but the second and third left a fine record. The Merced River canyon prior to the appearance of the ice probably was 1,200 to 1,500 feet deep and possessed the usual V-shaped contour of such gorges. When the glaciers reached their maximum, they filled the canyon which was being appreciably deepened and widened by ' A cirque is a steep-walled, round-bottomed amphitheater evolved by glaciation of the head of a mountain canyon. Fio. 14. Dotted line shows probable cross section of Yosemite Valley before Klaciation. Solid line shows the present cross-section and figures indicate amount of widening and deepening by the glaciers. After F. E. Matthes, V. S. Oeol. Survey Prof. Paper 160, p. S5. 19521 SIERRA NEVADA 31 their erosive action. The modi6eations cannot be correctly appor- tioned to the various ice tongues, but in total the canyon was deepened about 1,500 feet at its head where it was widened 1,800 feet on the north side and 1,700 feet on the south side. Excavation decreased in amount downstream. Glacier Point along the rim at the upper end of Yosemite Valley was covered by about 700 feet of ice, but Sentinel Dome which stands a mile back from the rim, the upper 700 feet of Half Dome, the top of El Capitan, and Eagle Peak, highest of the Three Brothers, were not overwhelmed. The lower limit of the ice projected perhaps 5 miles below El Portal where the typical glacial U-shaped canyon begins ; the lower few miles of the glaciers were thin and did not erode that part of the canyon to any extent. The last glacier was much thinner, measuring about 2,700 feet at the head of Yosemite Valley, instead of more than 4,000 feet as did the third glacier, and extended only a short distance below the great, bold promontory, El Capitan. This tongue of the fourth stage left a terminal and a number of recessional moraines as its fluctuated after its maximum advance. Recessional moraines are ridges of debris comparable with a terminal moraine and roughly paralleling it. They are developed by temporary advances of the ice after recession from the maximum development has begun. One of the recessional moraines lies a little below El Capitan and now appears as a high embankment well covered with trees and shrubs. It contains great numbers of granitoid boulders embedded in finer debris. As the glacier receded Elev above sea level Fio. li>. Section across Tenaya and Little Yosemite Canyons showing highest levels reached by glaciers in the second (Glacier Point) and third (Wisconsin) stages. After F. E. ilattkei. V. S. Geol. Surrey Prof. Paper 160. p. 8S. Ml. L>«ll^ Kio. 16. the Longitudinal profile of the two last glaciers that occupied Yosemite Valley and its tributaries during the glacial epoch. The lower solid line shows the last upper solid line indicates the much thicker and longer tongue of the ice of the third glacial stage. .l//er F. E. ilatlket, V. S. Geol. Surrey Prof. Paper 160, p. glacier, SO. 32 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 Fio. 17. Bird's-eye view of the Yosemite Valley as it probably was immediately after the ice age. The valley had been broadened and deepened to essentially its present proportions. The deepening accomplished by the ice ranged from 600 feet at the lower end to 1,500 feet at the upper end. A lake 5J miles long occupied a basin gouged into the rock floor of the valley and dammed in addition by a glacial moraine. After F. E. Matthes, V. 8. Oeol. Survey Prof. Paper 160, p. i9. up the valley from this moraine, a short, wide lake formed between the ice front and the rock barrier. With continued withdrawal of the ice, the lake grew until it extended to the upper end of Yosemite Valley, then attaining a length of about 6 miles. Because of the greater amount of glacial erosion toward the head of the valley than farther down, a basin had been formed sloping in that direction from the lower section where erosion had been much less vigorous. The moraine therefore merely increased the depth of the basin and the lake was much deeper at its upper end than its lower end, measuring perhaps 300 feet. When the lake reached its greatest size, upper Yosemite Valley must have been a glorious sight with the great, deep blue body of water fringed by gray walls rising nearly vertically above it. But Lake Yosemite did not last long in terms of geological time for into it quantities of sediment were poured by streams coming from the waning ice; thus the basin was filled rather rapidly. At the upper end the delta, as such deposits are known, finally rose slightly above average water level, forming at first a small delta plain. This advanced down the lake until it reached the crest of the dam, driving out the last of the water. The tributary streams formed the post-glacial Merced River which developed a serpentine path over the even surface of the delta plain until it came to the morainal dam down which it plunged into the unfilled, lower section of the canyon. Thus, though the lower part of Yosemite Valley as far as El Portal is a characteristic, trough-shaped, glacial canyon, the upper part has a flat floor, covered with trees and other vegetation. Since the disappearance of the lake, the Merced River for some unknown reason seems to have rather suddenly developed a shallow breach in the dam. cut a trench about 15 feet deep into the sediments, and then proceeded to widen its valley into a flat floor over which the river lazily meanders. Little Yosemite Valley, which was evacuated by the ice considerably later than the main Yosemite, had a roek-basin lake about 2J miles long and a mile wide. Since the basin does not appear to have been more than 50 feet deep, it was filled even before Lake Yosemite. Mirror Lake in the mouth of Tenaya Canyon is not a glacial product but was impounded by landslides, particularly from a place on the west wall of the canyon behind the Washington Column. This lake is being rapidly filled with sediment, though steps are now being taken to prevent its destruction. In no other Sierran canyon is there a lake history which matches that of upper Yosemite Valley. Small lakes, chiefly of the rock-basin type, are present and many have been filled, or nearly so, developing little meadows, but no large lake is known to have existed. The deepening and widening of the valley together with the trim- ming off' of spur ends between tributary gorges have given the bold, barren sides which stand so prominently above the valley floor. The excavation was greatly facilitated or hindered by the abundance or scarcity of joints, for where they were closely spaced removal by quarrying was easy, but where widely separated it was relatively ineffective and wear was accomplished by abrasion. The widest part of the valley, the upper half, therefore lies in closely jointed rock, but the lower part and the tributary gorges are in rock jointed less prom- inently. In the main valley, the widening decreases from about 1,800 feet on either side to a minimum of 500 feet on either side not far below El Capitan. Ascent of the Yosemite, Tenaya, and Upper Merced canyons is accomplished by a series of steps, another characteristic of glaciated 19521 SIERRA NEVADA 33 Fic. 18. Present configuration uf Yosemiie Valley. Merced River now meanders through the filled-in bed of Lake Yosemite. Photo courtesy U. S. Armjf Air Corps. 34 EVOLUTION OF THE CALIPORXIA LANDSCAPE (Bull. 158 Fig. 19. Yosemite Valley from Wawonu road. To the left is El Ciipitiui. I.i the richt Cathedral Rock and Bridalveil Fall. Photo by J. T. Boysen, courtesy V. S. Qeologicat Survey. 1952] SIERRA NEVADA 35 J M flu. -0. View up LiltJe Yoseniite \'al]ey. Photo court* a u I'. S. Army Air Curpa. EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 1952] SIERRA NEVADA 37 38 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 i :'^> Fio. 23. I'pper drop of Yosemite Falls (about 1,430 feetl. as seen from Merced River. Nortnan E. A. Hinds, OEOMORPHOLOOY (copi/right 19^3 by Prentice-Hall, Inc., AVtr York). Reproduced by permission of the publisher. canyons. The risers of the steps have been evolved in rock cut both by vertical and nearly horizontal joints where quarrying was easy ; the edges of the steps and the treads between them are in relatively unbroken rock, which resisted this type of erosion. Each tread is essentially a basip, and the edges are barriers of virtually unquarry- able rock, smoothed on the upstream side by abrasion and steepened on the downstream side by removal where more abundant jointing begins. Excavation took place most actively at the head of each tread for there the ice exerted its greatest force because of its plunge down- ward from the step above. Thus is explained the replacement of the steeply rising irregular preglacial canyon bottom by a nearly level, basined rock floor, and also why the excavation by the ice was nearly three times as great at the upper end of Yosemite Valley as at the lower. The ice entered the valley not only by the great stairway from whose steps Vernal and Nevada Falls now plunge, and from Tenaya Canyon, but also by a gigantic cataract from a cap of moderate size on the rolling upland at the base of Half Dome. The deep, walled-in headfe of Little Yosemite and Tenaya canyons also were excavated by similar ice cataracts coming from the sheet ice on the upland. Joints determined the level of each step in the valley. The high stand of the Little Yosemite above the main eanj'on resulted from the height of a very massive body of granite that forms the upper step of the great stairway in that canyon. The absence of such a step at the mouth of Tenaya canyon is explained by the presence there of jointed rock which greatly aided glacial excavation. Evolution of the minor features of the walls of Yosemite Valley also have been controlled by the jointing which has played a most signifi- cant part in the weathering that has taken place. Vertical master joints have controlled the position and profile of most of the great cliflf faces, including the sheer precipices over w-hich the falls plunge. The smooth, sheer front of Sentinel Rock is bounded by such a joint. Where there is little fracturing, the relief features are massive, as for example the great promontory. El Capitan, which rises so boldly for 3,000 feet above the valley floor. Cathedral Rocks Fio. 24. Glacial striae in rocks along middle fork of Kincs River south of Grouse Meadow. Photo by George J . Young. 1952] SIERRA XEVADA 39 Flc. '2o. Royiil Arches, Washingtuu Culumn (nui •me (upper center). Photo by F. E. .\tatthe$, courtesy I 40 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 also have been sculptured into some of the most masshe rock in the entire valley. In contrast are frail Cathedral Spires where the jointing is more closely spaced ; elsewhere manj' recesses which have been excavated along narrow, abundantly broken zones. The Royal Arches have been etched into a complexly jointed slanting cliff face about 1,500 feet high. Along highly inclined and curved joints, frost wedging has pried loose blocks bounded by these fractures. The Wash- ington Column standing just east of the arches has been carved out of a less broken mass or rock. Adding great beauty to Yosemite landscape when water is abundant are the many falls which plunge from hanging valleys standing at various elevations above the valley floor. Most waterfalls are broken in their descent by projecting ledges and should properly be called cascades; it is primarily in glaciated valleys that this less common, high, free-leaping type of waterfall is present, though some are formed in other environments. The streams responsible for the Yosemite Falls are small and consequently thej' appear as veils or ribbons of water rather than as massive cataracts, except for those of the Merced which are somewhat heavier. During the dry season the streams decrease in volume, the falls become largely misty clouds, and some disappear. Bridal Veil is one of the most perfect examples, emerging from the edge of a V-shaped guleh and plunging over a precipice 620 feet high. In the spring and early summer when the snow is melting the torrent is of considerable size, but during the rest of the year it is filmy and veil-like. Directly opposite on the other side of the valley, Ribbon Falls drop 1,612 feet from the edge of the upland ; it is the highest of all, but does not make a free descent throughout for it is held in a narrow, sheer-walled recess in the side of the valley. Even Fig. 2G. Diasrara showing how, by progressive exfoliation, the original angularities of a rock mass are replaced bv smooth curves. After F. E. Malthes. V. S. Geo!. Survej/ Prof. Paper ISO. p. 115. though they are produced by a stream of modest size, Yosemite Falls are the supreme spectacle of the valley. They are in three sections, the upper dropping over a cliff 1,4.30 feet high and being one of the highest if not the highest free-leaping fall in the world, though it does not clear quite this entire distance in a free plunge. Then the water scatters over several acres, collecting into sheets and rivulets that converge toward a half-bowl of polished granite from which the re- made stream races through a narrow winding gorge. After this tor- tuous descent of 815 feet, the water again plunges over a 320-foot cliff to the floor of the valley. In the short stretch of the Merced Canyon that connects the Little Yosemite with the main valley, there is an abundance of falling water, for the river descends 2,000 feet in a mile and a half. In the upper part the stream drops over the risers of the giant stairway producing Vernal and Nevada Falls, the former 317 and the latter 594 feet high, and farther down races in a series of raging cascades and rapids. A rival of Yoi?emite Falls is the Tueeulala in Ilctch lletchy Valley which has a total drop of about 1,000 feet, but a free leap of only about 600 feet. Morainal deposits include the terminal and recessional barriers which impounded the lake that lay so lately in the upper part of Yosemite Valley, and side moraines along the valley walls which have been added to by boulder fall and avalanches from the precipitous cliffs after the ice went away. One of the features characteristic of a glaciated region is polished, scratched or striated, and grooved bedrock, a product of the abrasive action of the moving ice. Particularly in resistant rock like granite, the polish is often remarkable. The scratches apparently are made by sand dragged along by the ice ; the grooves, which may reach a yard or more in depth, are formed by resistant boulders grinding into the rock. Such features can be produced in other wa.vs, but, where present over considerable areas and associated with other features of glaciation, can be interpreted only as the product of ice action. The famous domes of the Yosemite upland have been evolved from giant, joint-bounded columns of granite bj' long-continued exfoliation. This breaking off of shells of rock along more or less concentric frac- tures apparently has been caused by expansion of the rock as the load upon it has been relieved by erosion. Some of these domes in the Yosemite region were ice covered, others were not. The breaking off of shells of rock has also been aided by the prying action which results when water freezes in the joints. The Half Dome has an exceptional form because its steep northwestern side, a sheer drop of more than 2,000 feet, has been exposed only recently as the result of glacial modi- fications of the canyon below and the exposure of a nearly vertical 1952) SIERRA NEVADA 41 Fig. 27. Northeast side of Half Dome in Yosemite Valley. Frost wedging of joint blocks along a system of curved joints has produced shells that are several feet thick. Photo by F. C. Catkins, courtesy U. S. Geological Survey. system of joints which controls the precipitous face. The form of the southern side is eontrolled by concentric curved joints along which frost wedging has pried loose shell after shell. Tahoe Region In the vicinity of Laice Tahoe, the western mountains range from 8,000 to 10,000 feet in elevation, are broken by deep valleys which have been much ice worn and have prominent cirques at their heads. In the valleys are many rock basins and the characteristic stairway topography already described from the Yosemite section. The moun- tains in part are narrow ridges but certain areas like the Tallac-Dick's Peak range liave broad, flat summits. The higher parts were not cov- ered by ice and consequently have topography characteristic of vig- orous mechanical weathering, gravity transfer, and snow avalanehing above the limit to which the ice extended. In the mountain canyons there are few morainal deposits. Ice-abraded surfaces prevail, but such features as grooving, striation. and polishing have been exten- sively destroyed by rock weathering which lias followed disappearance of the glaciers. In some places there is considerable burial by talus. When the ice reached its maximum thickness, it covered all but the higliest ridges and tlat summits, moving principally from a large area of accumulation in Desolation Valley. Tongues traveled north, east, and south. Other glaciers came from cirque heads of valleys tributary to the main ones. While the main movement was down the valleys, several of the lower divides between them also were covered. This Fig. 2.S. Rock basin lakes and Fallen Leaf Lake. Lake Tahoe in the distance occupies the southern part of a long, narrow fault basin. Photo courtesy Southern Pacific Railroad. zone of vigorous glaciation possesses the wildest, most spectactilar scenery to be found about Lake Tahoe. Toward the lake is a zone of morainal ridges and irregular hiUs in which there are a number of lakes behind morainal barriers. The landscape is far different from that of the mountainous section pre- senting little that is startling but much that is beautiful. In this zone are Fallen Leaf ami Cascade Lakes and Emerald Bay ; the upper end of each is a basin scoured out of the bedrock, the lower end of each is made 42 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull, 158 Vi... :;'.>, Kiiio I wes ,:ike ( fi>resrou tern part t>f \v ml) lies in a glacially eroded rook basin. Fallen Leaf Lake (left niiilille Kriiuiidl i» iMipounded liy a terminal moraine, while Lake Tahoe. the hich shows beyond Fallen Leaf Lake, is contained in the lowest part of the Tahoe fault basin. Pholo hn V. S. Army Air Corpi. 1952] SIERRA NEVADA 43 by a combination of lateral and terminal moraines. At the southern end of the lake plain extending south from Lake Tahoe there is an extensive area of morainal hills and ridges left by a combined piedmont glacial mass formed by tongues moving northward in the upper Truckee Valley and eastward through Echo Lakes basin. At the southern end of the Tahoe fault basin is a series of flat plains standing at three levels. The most extensive of the three was formed by outwash left by subglacial streams coming from glaciers which lay to the west and south. About 20 feet below this outwash plain is a lower, much less extensive series of terraces eroded by the L^pper Truckee River since the ice receded. About 20 feet above the outwash deposit is the third section of the plain ; its origin is uncertain but it very possibly represents deposits of the larger Lake Tahoe before its waters developed the outlet eastward by erosion of Truckee River Canyon. In the heart of the western mountain areas is Desolation Valley, or, as it is called on certain maps. Devil 's Basin. On its southwestern border rise the bold slopes of a range dominated by Pyramid Peak (elevation 10,200 feet) which constitutes a barrier between the basin and a group of westward oriented valleys. The Cracked Crags separate Desolation Valley from Glen Alpine and Echo Lakes valleys, and north- directed spurs from the Pyramid Peak Range and Jack's Peak unite at Mosquito Pass and form a divide beyond which is Rockbound Basin. Southward a |rroup of low hills partly isolate Desolation Valley from the steep gorge down which its drainage flows to the South Fork of the American River. During at least some of the glacial stages, ice so filled Desolation Valley that it overflowed northward into Rockbound Valley, eastward into Glen Alpine and Echo Lakes valleys, and southward into the can- yon of the South Fork of the American River. The relatively low elevation of the divides crossed by the glaciers in part has resulted from the hea\y wear by the advancing ice. Largest and most complex of the valleys in this region and perhaps the most attractive scenically is Glen Alpine. In it lies Heather, Susie, Half Moon, and Grass lakes, which occupy rock basins, and Gilmore Lake which is held in by a morainal dam. There are prominent cirques, particularly at the head of Half Moon Valley, and the canyon sides exhibit evidence of vigorous glacial erosion. The rounded rock knobs called roches moutonnees are fairly abundant in the valley bottoms. Echo Lakes valley is similar to, but is not branched like Glen Alpine. Lower Echo Lake is unique in that it occupies a rock basin on the southeastern rim of which is a low morainal ridge. The remainder of the eastern rim is bedrock, from which there is a long, steep, ice-worn slope descending to the lake plain. Down this slope Echo Lakes glacier must have plunged as a gigantic ice cascade. In the northern part of this mountain section the valleys tributary to Cascade Lake and Emerald Bay show glacial features similar to those in the Desolation area, but they were developed by glaciers which grew in the valley heads. Rockbound Valley also was deeply eroded by ice flowing in from Desolation Basin. The longest valley beading in this glaciated mountain region is that of the South Fork of the American River. In the upper part are abundant morainal deposits and as.sociated marshy flats, doubtless fills of small lakes lying between the morainal ridges. This morainal cover extends down the .valley about a mile southwest of Phillips, beyond which glacially eroded features are prominent as far as Lovers' Leap, about 3J miles to the southwest. Mount Whitney Region The Mount Whitney region of the Sierra Nevada lies a little south of the middle of the range and is the highest part of the fault block. Mount Whitney, 14,496 feet above sea level, is its culminating summit. Normally the higher part of a mountain range of great altitude which has been powerfully eroded consists of an alternation of deep, narrow canyons separated by high and narrow crested ridges sur- mounted by sharp pointed peaks. If such a landscape has been intensely glaciated, the boldness and raggedness of the topography is greatly increased. Mount Whitney and many other peaks in this and other sections of the Sierra Nevada, however, have gently sloping, table-like summits which could not have been formed by initial erosion ; rather they are gradually being destroyed by weathering and removal of debris. Therefore these mountains must belong to an earlier cycle of erosion when the landscape looked quite different from that of today. Because of the long time which has elapsed since the first building of the range, 120 to 130 million years, we see none of the landscape developed by the deformation, but we do see relics which have been carved from it. The great folded and faulted ridges brought into being by the compression of the region are gone, but fortunately in places their roots are still preserved showing the structures which were evolved. In the southern two-thirds of the range, ero.sion has gone deeper into the granitoid batholith which formed in the heart of the mountains as they were originally elevated. None the less, there are scattered remnants of folded and faulted cover which had projected farther than the average into the intrusive mass. After the ancestral Sierra Nevada had been eroded for about 60 million years, it had been so worn down that there remained only rows of hills probably marking the sites of the original deformation ridges ; beyond were lowlands sloping gently westward toward the ocean and for an unknown distance to the east. Between the ridges, the streams flowed mostly in northwesterly and southeasterly directions as they had done 44 EVOLUTION OP THE CALIFORNIA LANDSCAPE (Bull. 158 Mount Whitney. ATorman E. A. Hinds, QEOMORPHOLOQY (copyright 19^3 by Prentice-Hall, Inc., Neu> York). Reproduced by permission of the publisher. from the early days of the range, with less important drainage directed toward the southwest and northeast. Possibly 40 or 50 million years ago began the first of a series of uplifts vhich eventually led to the development of the present Sierra Nevada. The Sierra and the country east of it seems to have been tilted to the southwest so that new master streams flowing in that direction were created. However, lesser streams between the ridges were unable to change direction and continued in their previous courses parallel to the trend of the range. As each uplift occurred all of the streams were invigorated and cut young canyons deeper into the rocks of the range, the principal ones directed to the southwest, lesser ones to the northwest and southeast. In the evolution of present Sierran relief the northwesterly-south- easterly crests roughly paralleling the principal crest along the eastern margin are of prime significance. They are among the oldest features of the landscape and are inheritances from the original ridges of the fold- fault range. Some of these longitudinal crests have been carved into folded and faulted rock, as for example the Ritter Range. The south- U152] SIERRA NEVADA 45 .m^- F:o. 31. Sierra Nevada, California. Huge talus cniit-s nn^i talus aprons extend far up the walls of the deeply glaciated canyons. }iorman E. A. Hindi, OEOMQRVUOLOQY (copyright 19^3 by I'rentice-Itall, Inc., A'eir York). Reproduced by permission of the publisher. eastward-trending upper canj-on of the Middle Fork of the San Joaquin River, paralleling the Ritter Range as far south as Pumice Flat, has been eroded into the same mass of rock and follows the direc- tion of the folds. Le Conte Divide is another example. On the other hand, the South Fork of San Joaquin River has cut its northwestward- trending canyon in the rock of the batholith. Farther south in the headwaters of the Kings River and in Sequoia National Park, where the folded structures of the Sierra Nevada bend farther south and southeastward, the principal crests and valleys follow them but are carved mostly in granitoid rock. The Great Western Divide contains folded rocks in the vicinity of Mineral King and in the Kaweah group. The upper Kern River canyon is cut entirely in the batholithic rock ; Mount Whitney itself is composed of the same material. The crest of which Whitney is a part and for which the name Muir has been appropriately suggested, runs south-southeastward for about 17 miles from Shepherd Pass on the north to Cottonwood Pass on the south. It contains seven of eleven peaks in the Sierra Nevada whose EVOLUTION OP THE CALIFORNIA LANDSCAPE Fig 32. Mt. Whitney and the Sierra crest. A'ormon E. A. Hinds, GEOMORPHOLOOY (copyright 194S by Prenlice-Uall, Inc., New York). Reproduced by permission of the pubiisher. elevations exceed 14,000 feet — Tyndall, Williamson, Barnard, Rus- sell, Whitney, Muir, and Langley — as well as several which are only slightly under that elevation. West of this crest is the upper part of the Kern River canyon. The river's position may have been determined by tlie ridges on either side, or by a fault, which may be of equal antiquity and which was easier to erode than the unbroken rock on either side. There are features on the east side of the Muir crest which suggest that another longitudinal valley of great age lay in that direction, a valley generated long before the late elevation of the Sierran region and the depression of Owens Valley. The crest appears to have been more sharply outlined by valley deepening east and west of it during the episode of elevation, perhaps 40 or 50 million years ago. Many of the peaks in the various crests show a summit platform similar to that of Whitney and some of them slope downward on one or more sides to what evidently were at one time broad valleys. At this time Mount Whitney was a dome-like hill which rose about 1,500 feet above the adjacent valley floors. The distance from the sea coast was 19521 SIERRA NEVADA 47 ^><^^' 3?r.^s^ r?> '^'' ■^- i3^» . ^* Kio. Xi. Franklin Pass. Mineral Kini^ is to left of tbe ruige along the skyline. Photo by OforgeJ. Young. Tvi. M. Ml. Metjee and Kvtilution Itasin. Debris in center was left \>\ siacier. Photo 6y George J. Young. less than today, for the oi-ean covered much of the region now occupied by the Coast Ranpes and the Great Valley, but the peak must have stood at least 50 miles inland. Comparing this with other regions, it has been concluded that the elevation at the base of the "Whitney Hill" was perhaps 500 feet, so its summit stood approximately 2,000 feet above sea level. The many flat-topped peaks in the high Sierra similar to Whitney evidently are of the same origin. Perhaps most striking is Table Mountain (13,464 feet) in the Great Western Divide on the opposite side of the Kern River Canyon from Mount Wliitney, but there are others in the vicinity. These peaks are about 1,000 feet lower than Whitney, but they are 10 to 15 miles farther west where the general slope of the range carries them to lower elevation. Farther north in the range are Darwin, which has two separated platforms standing at altitudes of l.'),841 and 1.3.701 feet, respectively; Kuna, Koip, and Blacktop in Yosemite National Park which together form a continuous platform about 3J miles long and between 12.500 and 13,000 feet in elevation. Parker Peak (12,8.50 feet). Mount Gibbs (12,700 feet), and Mount Dana (13,050 feet) are other examples. The lower elevation of these more northerly peaks is consonant with the slope of the crest of the fault block in that direction from the Mount Whitney region. Mount Whitney is about 1,000 feet higher than other peaks in the immediate vicinity which have rounded or gently sloping summits, such as Young, Hitchcock, Lone Pine, and Cirque. Mount Langley ( 14,042 feet ) also exceeds by a similar amount summits in its neighbor- hood. Furthermore the smoothly curving slopes of these lower moun- tains descend to levels at about 12,000 feet and seem to have been evolved with reference to lower valley floors than either Whitney or Langley, whose slopes descend to remnants of a former valley which now stand nearly 13,000 feet above sea level. Thus it seems that the first elevation of the Sierran region in early Cenozoic time caused the streams to carve canyons about 1.000 feet deep on both sides of the crest of which Whitney and Langley are a part, and of course, similar erosion occurred elsewhere in the range. During the quiet that fol- lowed this disturbance the streams passed from youth to maturity, widening their valleys by cutting terraces into the bedrock on either side of their courses. At the same time the mountain slopes were worn back to rather gentle angles. This uplift increased the elevation of 48 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 Fig. 35. Part of Evolution group 1!)52] SIERRA NEVADA 49 5#'tf\ '^^"T.t;^-^*-' I Fio. 36. The Sierra Nevada Id the vicinity I'f Mount Whitney, California. Before the last elevation of the range, the high peaks were low. rounded mountains rising little over 2..KW feet above wide valleys, a fine example of which shows in the middle ground of the photograph. The canyon of the Kern River has been eroded as the range has risen to its i>resent height. All of the peaks and canyons have been deeply glaciated. A great cirque has been eroded into the eastern side of Mount Whitney, the peak in the foreground. .VormOB E. A. Hindi. OEOilORPHOLOGY (copyright 194S 6v Prenlice-IIall, Inc.. Xetc York). Reproduced hn permission of Ihe publisher. Mount Whitney to about 4,000 feet, and, because of the valley erosion, caused it to stand another 500 to 600 feet higher above its immediate base. Also, long spurs were carved on both sides of the crest, which are represented by Mount Young (13,493 feet) and Lone Pine Peak (12,951 feet). West of Cirque Peak and about 1,500 feet below its rounded summit is a gently undulating plateau that extends unbroken for 7 miles to the canyon of the Kern River. This plateau undoubtedly represents part of a broad valley developed by the ancestral Kern River following a second uplift ; other remnants are Guyot Flat northwest of Mount 50 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 Trough-like glaciated river canyoDS, cirques, and snow avalanche sculpture in the high Sierra Nevada near Mount Whitney. Norman E. A. Hinds, QEOMOR- PHOLOOY (copi/right 194S hy Prentice-Bait, Inc., Neic York). Reproduced by permittion of the publither. Guyot and Bighorn Plateau between Wallace Creek and Tyndall Creek. Apparently this second deformation, which occurred in late Miocene and early Pliocene time, added about 3,000 feet to the elevation of Mount Whitney, so that it stood 7,000 feet above sea level. Its height above its western base resulting from this further valley cutting was about 2,000 feet as compared with the 500 feet of the "Whitney Hill" first described. About 1,500 feet below the terrace remnants just described lie broad, gently sloping rock benches that flank the deep Kern River canyon. One of these is the Chagoopa Plateau which rises from an elevation of about 8,600 feet at the canyon rim to about 10,500 feet at the base of the mountains. These benches are clearly remnants of a former broad valley of the Kern River eroded after a third period of uplift which seems to have added about 2,000 feet to the elevation of the Sierra Nevada, thus raising the summit of Mount Whitney to about 9,000 feet. Probably this was part of the Miocene-Pliocene deformation. The present Kern River canyon, like other deep canyons in the Sierra Nevada, is the product of vigorous stream erosion accompany- 1952] SIERRA NEVADA 51 ing the elevation of the region which started just before the beginning of the Glacial epoch and has continued with notably decreased inten- sity until the present. The part of the Kern River canyon in the Mount Whitney region is 2,000 to 2,500 feet deep and has been strongly glaciated. The U-shaped form of the upper part of the Kern River canyon is the product of glacial modification of a normal V-shaped river canyon. There were at least three invasions by the ice and further study may reveal a fourth. Tributary to the master gorge are the canyons of Wallace, Whitney, Rock, and other creeks. Because of the recency of elevation in the Sierran region, these tributaries have eroded gorges only about a mile in length, at the mouths of which water plunges precipitously into the main canyon. Thus they are hanging valleys such as are present in the Yosemite and other sections of the Sierra Nevada. The glaciation of the valley of Whitney Creek differs mate- rially in its various parts. In the lower section, the ice was never more than 600 feet thick and wrought only moderate changes ; but, near the base of Mount Whitney, where two tributary glaciers joined, the com- bined tongue exceeded 1,000 feet in depth and the glacier remained longer than it did far down the valley, altering the original form of the river-cut gorge to greater degree. On the eastern side of the Muir Crest, vigorous ice attack pro- foundly modified the canyon heads by eroding large cirques which worked back, destroying pre-glacial slopes and spurs and even carrjang away part of the main divide as between Mount Whitney and Whitney Pass, where only the western slope now remains. In some places, as south of Mount Le Conte, the divide was attacked from both sides, and was reduced to a narrow, ragged, comb ridge; in others, as be- tween Mounts Whitney and Russell, the growth of opposing cirques was so extensive as to leave only a thin rock wall. In a few localities, as between Mounts McAdie and Mallory, the divide was destroyed and replaced by a saddle. Mount Whitney must have been a dome of considerable bulk, even if not of great height above its surroundings, or it would have been reduced to a thin spire like its neighbor. Mount Russell. Even so, the entire eastern half has been cut away by small, but long-lived glaciers which lay upon its slopes until comparatively recent times. Destruc- tion still goes on vigorously because of frost wedging and the fall of multitudes of loosened blocks down the steep slopes. A considerable section of the north side of the peak was removed by the glacial widening of a canyon between it and Mount RusseU, and on the west, the lower pre-glacial slope has been destroyed by the enlargement of Whitney Canyon while occupied by ice. The southeast side also lost a small slice by the incision of a narrow cleft, the northernmost of a similar series that break the crestline at intervals of more than a mile to the south of Mount Whitney and through which occasional views may be obtained to the eastward from the trail up the mountain. These clefts are not glacial features but have resulted from active frost wedg- ing aided by snow sliding along vertical zones where the granite appears to have been sheared by ancient faulting into thin, rather easily removable vertical plates. Only on the southwestern side does Whitney retain its original pre-glacial slope which connects it with the equally unglaciated slope of the main divide. The upper slopes of Mount Whitney and the entire length of the Muir Crest show no evidence of glacial attack, in striking contrast with the abundant evidence of such action in the upper San Joaquin and Tuolumne drainage areas and in the Kaweah, Kings, and Kern basins. This probably results from the close proximity of the Muir Crest to the southern limit of Sierran glaciation and also to the effect of the Great Western Divide upon which the rising air currents delivered most of their moisture as they do today, thus keeping a greater share from the Muir Crest. Such topographic barriers produce striking cli- matic contrasts within short distances. Above the level of the ancient glaciers, the sides of Mount Whitney are furrowed by parallel or converging snow or avalanche chutes developed by powerful erosion as the great snow cascades swept down the steep slopes. Some of the chutes are 50 to 100 feet deep, and, where close together, are separated by narrow rock ribs which give the cliffs a fluted appearance. The bottoms of the chutes have been worn smoothly concave by the abrasive action of rock carried along by the snow slides. Avalanche chutes are best developed on the west side of Mount Whitney, though they also show well on the north side. Even more perfect, though not so deep, are those on the north side of Mount Hitchcock and in the cirque at the head of Wliitney Canyon. The Whitney region is especially rich in this t\-pe of sculpture because of rather regular joint and fault structure in the granitoid rock which makes for easy erosion. In other parts, where the joints are more widely spaced or irregular, the chutes are sparse and not well developed. Studies indicate that snow conditions prevailing on the flattish sum- mit of Mount Whitney are closely related to evolution of the chutes. The avalanches producing them come largely from snow blown to the ea.st as great "snow banners" by terrific winds sweeping across the top of the mountain. Although most of the snow goes eastward, con- siderable amounts are driven in other directions, accumulating as massive cornices at the edge of platforms, with the snow now and then collapsing to produce the avalanches. Today in the winter the flat tops of the Sierran peaks are covered only with a thin mantle of snow because of the powerful winds which sweep across them ; this condition seems to have prevailed during the 52 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 glacial stages. Therefore these summits have escaped the ice attack which has been so effective at lower elevations. Not only this, but there also has been little stream erosion to modify thejr contour. Heavy showers are rare at such high elevations and snow melts too slowly to produce streams of water. In fact, most of the water sinks into the rocks where it freezes during both summer and winter, cracking the rod; to produce the great multitude of blocks which cover the tops of the flat peaks and have fallen down the slopes to form huge talus cones and aprons. Thus we have in Mount Whitney and most of the other peaks of the high Sierra, hills and low mountains belonging to a time when the highest stood not more than 2,000 feet above sea level and the Sierra Nevada was anything but an imposing region. This perhaps was 60 million years ago. The changes which have followed have produced the remarkable multiple landscape, of which extensive remnants have been preserved because the vigorous erosion accompanying the late elevation of the range has not had time to destroy them. Glacial Lakes In the glaciated sections of the Sierra Nevada are hundreds of small, very beautiful lakes which add immensely to the glory of a landscape undoubtedly almost lakeless prior to invasion by the ice. Although there may have been a good many lakes and swamps when the Sierran region was worn down to its lowest stand 60 million years ago, it is certain that few existed as the mountains rose ; the normal processes of mountain erosion are against their formation as the land is too much broken up by active streams. A few basins may be evolved by faulting, landsliding, or volcanic action but their total is far short of the number present in those sections of all mountain ranges remodeled by ice. The present lakes were produced by the latest glaciers though undoubtedly many were formed as the earlier sheets and tongues left the range. Perhaps in many cases the thinner and weaker glaciers of the last stage merely cleaned out debris-filled basins excavated by the earlier, more powerful ice masses, but without doubt they dug addi- tional basins. In the high Sierra, where the reservoir ice supplying the glaciers evolved in canyon heads and eroded cirques, it etched depressions into the bedrock in which lie hundreds of cirque lakes. In this part of the range, and also in the lower northern and southern sections, cirque lakes are most abundant on northeast slopes where the snow was drifted by the prevailing westerly winds and where melting was least effective. The peaks above such lakes are typically unsymmetrical, being steeply cliffed on the northeast side, where the cirques have been incised, and more rounded on the southwest. The rounded slopes are remnants of the ancient hills and low mountains which had been evolved prior to the late elevation of the region. Cirques not occupied by the last ice have been considerably modified by erosion, their bottoms filled with great masses of talus, and lakes that were present have been converted to meadows. In cirques where the last ice grew, the rock is generally so bare as to indicate that the glaciers have very recently left. Where several cirques are being eroded opposite each other in valleys radiating from a dome-shaped peak like most of those in the pre-glacial Sierra Nevada, the cirque lakes are separated by high ridges commonlj' having exceedingly ragged crests and the peak itself has been reduced to a steeply sloping spire. On the other hand, if several pre-glacial valleys headed in a group of mountains and converged into a trunk canyon, the cirques have a similar converging pattern, the smaller ones hanging above the canyon. The cirque lakes of such a group therefore are closely associated. In the Sierra Nevada there are many cirque lakes in basins developed under one of the two conditions described above. In the higher middle section they are present by the hundreds but farther north and south where the glaciation was less intense there are not so many. Gold Lake, at the head of a tributary of the Middle Pork of the Feather River, has a length of about 2 miles and is one of the largest cirque lakes. Somewhat farther south below Sierra Buttes near the North Fork of the Yuba River and around Fall Creek Mountain near the South Fork of the same river, are two groups of lakes. A number of small cirque lakes lie at the headwaters of the Kaweah River in Sequoia National Forest, and fourteen of them, more or less completely converted to marshes, are clustered around the head of the Stanislaus River. In some of the U-shaped valleys, basins have been excavated below the cirques. The lakes filling them, starting with those in the cirques, are connected by a stream flowing in and out and from a distance look like beads of turquoise or sapphire on a chain. The basins are in places particularly susceptible to erosion where the rock was closely jointed, or where it was slightly less resistant than the immediately adjacent rock. Such chains of lakes are found in the headwaters of Illilouette Creek, 16 miles southeast of Yosemite Valley, between Mam- moth Mountain and Mammoth Crest high on the eastern slope of the Sierra Nevada 22 miles south of Mono Lake, and farther south in the Sixty-Lake basin at the headwaters of the Kings River below Mount King. Garnet Lake and Thousand Island Lake, which have a roundabout drainage to the Middle Fork of the San Joaquin River, stand out among cirque lakes because of the many rocky islands rising above their surfaces. A few lakes like Silver, Loon, and Pleasant in glaciated branches of the South Fork of the American River appear to lie in the lowest parts of unevenly eroded valley floor. Where the valleys are narrow and steep walled, such lakes are long and oval in plan, being larger 1952] SIERRA NEVADA 53 Ki.i. :>.^ ri-..iL,iii,ui ^ii..w uialaDcbe scalpturing on the side of a peak in the Mount Whitney region. Where rock structures are favorable the avalanche chutes are sep- arated by narrow, ragged rock ribs like those in the foreground. Mormon B. A. Hindi. GEOMORPHOLOGY (copvrigkt 194S by Prentice-Hall. Inc.. Xew York). Repriy- duced 6v permiiMion of the publither. than the normal rock-basin lakes ; but if the glacial trough is wider, the lakes are broader, irregular in outline, and commonly have rocky islets projecting from them. In the barren, wind-swept, rolling upland toward the higher part of the range, where remnants of the ancient landscape are preserved ami where iee caps evolveii, small nx'k-basin lakes, such as in Devil's Basin, a wide area at about 8,200 feet at the head of the South Fork of the American River, also are present. Humphrey Basin, at about 11,000 feet at the head of the South Fork of the San Joaquin River, is another example. In this area is Desolation Lake, about 1 mile in length. Certain lakes lie at or toward the end of the glaciated section of a canyon and are partly impounded by a barrier of morainal material. The most familiar example is Donner Lake (elevation 6.400 feet) about 3 miles long, on Highway 40 on the east side of Donner Pass. In the same drainage basin, but less often seen because it lies higher in the mountains to the northeast is Independence Lake (elevation I 54 EVOLUTION OP THE CALIFORNIA LANDSCAPE (Bull. 158 FlO. 39. Donner Lake east of Donner Pass in the Sierra Nevada. Tlie lake has been impounded by a terminal moraine left by a glacier whieh advanced down the valley shown in the foreground. In the distance are Tahoe fault basin and Carson Range. Photo courteay U. S. Army A,r Corps. 1952] SIERRA NEVADA 55 7,000 feet), which is 2 miles in length. Well-known Fallen Leaf Lake (about 6,400 feet) on the southwest side of Lake Tahoe is about the same size as Donner Lake and its barrier is a relatively low moraine of the last glacial stage. However, beyond this deposit are huge moraines of the preceding stage ; one southeast of Fallen Leaf Lake is about 3 miles long and rises abruptly for 900 feet above its surround- ings. Cascade Lake, 3 miles northwest of Fallen Leaf and of about the same size and altitude, lies behind a compound loop of morainal deposits. Twin Lakes, having a combined length of 3 miles, and more than 7,000 feet high on a fork of the Walker River 15 miles southwest of Mono Lake, also lie behind a moraine and have been separated by the growth of delta plain deposits near the middle. Many of the Sierran lakes have been filled or nearly filled with sedi- ment and now are meadows covered either with small vegetation or trees; these meadows are some of the most delightful spots in the Sierran canyons. The best known is that in Yosemite Valley. Another occupies the lower part of Tenaya Canyon, northern tributarj- of the Yosemite, and is the fill of a rock-basin lake. Still a third of larger size occupies part of Little Yosemite Canyon. One of the longest filled areas is Tuolumne Meadows which apparently represents the filling of several closely spaced rock-basin lakes. Most of the meadows are larger than the lakes were, for the deposits generally have spread in some or all directions beyond the margins of the basins. Numerous lakes impounded by landslides from steep canyon walls are present in the Sierra Nevada. Mirror Lake in Yosemite Valley is one of these. Another is Kem Lake in Kern River canyon. Artificial Lakes Many reservoirs have been established in the Sierra Nevada for flood protection, water storage for irrigation and other uses, and power generation. Some of the principal examples are Almanor near the intersection of Highways 36 and 89 at the north end of the Sierra Nevada, a group in the Mokelumne basin which supplies water for cities on the east side of San Francisco Bay and another, principally Hetch Hetchy Reservoir, which is the principal source of San Fran- cisco's water supply. Still other artificial lakes of considerable size are the Pardee Reservoir near Jackson, the Calaveras Reservoir near San Andreas. Near the mouth of the canyon of the San Joaquin River is the Friant Dam which impounds Millerton Lake ; this is the second most important element in the great Central Valley Project which is so vital to the Sacramento and San Joaquin Valleys. The principal unit in this project is the huge Shasta Dam in the Klamath Mountains of California. Water is to be exported to various parts of the eastern side iif the southern San Joaquin Valley from Millerton Lake to bolster the underground and surface waters which have been severely tapped ^-^S^i^ I, 4 * ..,*f^ -V,; . . -«r ■ '-'-- •~^-^~ 1 Fio. 40. Heather I^ke. Alia Peak region. Sierra Nevada. The smoothed rock surface has beeo produced by glacial abrasion. Photo courtftp L'. ^'. Sotu^nol Park Service. 56 EVOLUTION OP THE CALIFORNIA LANDSCAPE I Bull. 158 I Fig. 41. Four stages in the filling of Kern Lake in Kern Canyon, Tulare County, liy deposition from the inHowing stream. The lake apparently was formed in ISfi" by a landslide from the west wall of the canyon which for a time dammed the river. If depcsition continues as is probable, a forest-covered lake plain or meadow will be formed. A. 1010; B. 1918; C, 1928. Photos by T. A. Church. 1952] SIERRA NEVADA 57 by frrowing population, agriculture, and industrj*. Many of these reservoirs have become pleasure resorts to which hundreds of people go for outings of various types. VOUCANISM Along part of the Kern and Little Kern canyons are the Palisades, part of a lava field that shows at least four distinct flows, each of which possesses rather crudely developed columnar jointing perpendicular to the flow surface. This jointing developed as the lava cooled and con- tracted. In other places in the field there are more flows, but thin, weathered zones between them makes separation difiicult as the lavas are similar in composition. The total thickness of the lava in remnants that are left exceeds 400 feet ; how much has been removed by erosion cannot be determined. In the Toowa Valley below Toowa Range — a high valley drained to the west by a stream kno\vn variously as Godel, Trout, Volcano, or Little Whitney creek, and to the east by the South Fork of the Middle Kern River — there is another volcanic field which covers an area about a half mile wide and 4 to 7 miles long. This field contains flows and cinder cones. Cinder cones are small volcanoes, generally less than 1,000 feet high, composed entirely of lava fragments. Most of them are built during brief eruptive cycles lasting a few days, weeks, or months. Toowa Valley is broad and open and stands at an elevation of about 8,600 feet. The cones rise from 400 to 600 feet above the veneer of flows which covers the bedrock. The latest activity blocked drainage, as two prominent cones lie along the axis of the valley — South Fork Cone where Golden Trout Creek enters Toowa Valley, and Ground- hog Cone 2 J miles farther east. Two other volcanic centers are in the vaUey, one at the head of Little Whitney Meadow and one at the Tun- nel, north of South Fork Cone. The activity has been so recent that soil is scanty and therefore vegetation is sparse. Several stages in the total eruptive cycle are recorded. It is evident that these eruptions occurred long after the major faults outlining the eastern base of the Sierra Nevada had been evolved. Earlier basalt apparently of pre-glacial age poured from vents in the canyon of the North Fork of Oak Creek and spread over an alluvial cone formed by the stream issuing from its mouth. Later this lava was partly eroded and covered by debris of the first glacial stage. Basalt flows, probably of the same age, form a number of isolated patches on the south side of Bishop Creek which issues from the Sierra Nevada. Another considerable volcanic area is located in the headwaters of the Middle Fork of the San Joaquin River to the east of the towering range which has Mount Ritter, Banner Peak, and The Minarets as its principal peaks. The summit of the range is somewhat over 13,000 feet above sea level; Mount Ritter rises abruptly more than a mile above an area of much gentler relief which finally ascends to the lower main eastern divide of the Sierra Nevada, a crest much less imposing than those to the north and south. The rolling area between the two mountainous barriers probably was part of one of the flat valleys belonging to a landscape evolved prior to the last elevation of the Sierra Nevada. The section described has been extensively covered by pumice and lava which is believed to be at least 2,000 feet thick in places. The frothy pumice fragments were exploded from a series of cones at least 30 in number lying mostly east of the Sierra Nevada and extending from Mammoth Mountain to Mono Lake, and includ- ing the Mono volcanic range. Most of the pumice came down around the volcanic pipes forming the volcanoes but finer debris was carried far by the wind and is found sprinkling a considerable part of this section of the range. Mammoth Pass and the divide for several miles north are most heavily mantled, and Pumice Flat, as the name indi- cates, has a goodly cover. Even at Reds Meadow and farther south along the Middle Fork of the San Joaquin River, there is a thin veneer of pumice. From the alignment of the cones, it is evident that they are located along some of the faults evolved during the great landscape changes in the eastern part of the Sierra Nevada. Certain of these fractures apparently penetrate into the range for some distance as is indicated by the fact that Mammoth Mountain, a greatly worn old volcano, the Little Red Cones on the east side of the Middle Fork, and Pumice Butte north of Fish Creek stand in line with them. The well-known hot spring near Reds Meadow, though somewhat to the west of the line of cones, probably rises along a branch of this fracture sj^stem. Volcanic eruptions occurred along these faults at different times. Mammoth Mountain, a modest eminence which belies its name, was built prior to the beginning of the Glacial epoch and therefore is more than a million years old. So much time has elapsed since activity ceased at this vent that the original form of the cone has been destroyed and there remains only a shapeless mass of volcanic debris. The pumice outbursts are the latest chapter in the recurrent eruptions along the faults, having begun late in the fourth glacial stage and continuing until quite recent time, though not within the historic period. During the third interglacial stage, more than 100,000 years ago, a fissure opened in ^lammoth Pass and from it spilled a flood of basaltic lava most of which streamed into the canyon of the San Joaquin's Middle Fork, spreading out as a tongue from the head of Pumice Flat beyond Rainbow Falls : the flow was at least 6 miles long and is believed to have ranged from 100 to 700 feet in thickness. As the rock cooled after consolidation from the molten liquid, it contracted and joints formed which broke it into rather easily removable columns. 58 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 M^. »jw5fS-; 1 „. 4-. i;,.Mer„ l.u^,. „f U... Sur.u NVwida. ..,.|-.,ral, ,1 l.> u fault .l.prefision from one of the westernmost of tbe fault blocks of the Basin Ranges Province. v-^^ iN« ^r"!!^.^*^. u..AS^^W*ti North of Keno. Nevada. Fhoto courtety Wfalern Pacific Railroad. SIERRA NEVADA I Fio. 43. Feather River Canjon near Rock Dam. Photo cotirtety Western Pacific Railroad. 60 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 When the last glacier descended the Middle Pork canyon, the lava flow formed an obstruction in its path ; but the ice was about 1,000 feet thick and therefore overrode the barrier. The prominent jointing made possible easy quarrying by the glacier which was present long enough to remove most of the lava and re-excavate the canyon down to the granitoid rock beneath. Only the most resistant parts of the flow escaped destruction. The largest remnant is a hump in the middle of the canyon which is about 300 yards long and 200 feet high. Because of the roscinblanee of its tall, straight columns to stacked posts, it has been called the Devil's Postpile, and a National Monument has been created to protect it. The columns forming the steep western front of the Postpile are high, straight, and very clearly outlined, but those at the southern end are even more remarkable for their curvature and radial arrange- ment with respect to a center at the top of the pile. On this upper surface may be seen the five- or six-sided ends of the columns, in places still possessing the polish and striations given to them by the over- riding glacier. REFERENCES Atwood, W. W., Jr., Crater Lake and Yosemite through the ages : National Geographic Magazine, vol. 71, pp. 326-343, 1937. Beatty, M. E.. A brief story of the geology of Yosemite Valley ; Nature Notes, Special Number, National Park Service, 1943. Blackwelder. Eliot, Pleistocene glaciation in the Sierra Nevada and Basin Ranges : Geol. Soc. America Bull., vol. 42, pp. 865-891, 1937. Blackwelder, Eliot, Supplementary notes on Pleistocene glaciation in the Great Basin : Wash. Acad. Sci. Jour., vol. 24, pp. 217-222, 1934. Davis, W. M., The lakes of California : California Jour. Mines and Geology, vol. 29. pp. 175-236, 1933. Flint, R. F., Glacial geology and the Pleistocene epoch, John Wiley and Sons, Inc.. 1947. Hills, T. M.. Gliicintion of the upper Kern and its tributaries: Sierra Club Bull., vol. 12, pp. 17-1!), 1928. Jones, W. I).. Giaoial land forms in the Sierra Nevada south of Lake Tahoe : Univ. California Pub. Geog.. vol. 3, pp. 137-157, 1929. Kesseli. J. E., Studies in the Pleistocene glaciation of the Sierra Nevada : Univ. California Pub. Geog., vol. 6, pp. 315-361, 1941. Knopf, A., and Kirk, E., A geologic reconnaissance of the Inyo Range and the eastern slope of the southern Sierra Nevada, California : U. S. Geol. Survey, Prof. Paper 110, 1918. Lawson, A. C, The geomorphology of the upper Kern Basin, California : Univ. California Dept. Geology Bull., vol. 3, pp. 291-376, 1904. Lawson, A. C, The geomorph(dogic features of the Middle Kern : Univ. California Dept. Geology Bull., vol. 4, pp. 397-409, 1906. Louderback, G. D., Lake Tafaoe, California-Nevada : Jour. Geography, vol. 9, pp. 277-279, 1911. Jjouderback. G. D., Morphologic features of Basin Range displacements in the Great Basin: Univ. California Dept. Geol. Sci. Bull., vol. 16, pp. 1-42. 1926. Matthes, F. E., Kings River and Yosemite Valley: Sierra Club Bull., vol. 12, pp. 224-2.36, 1926. Matthes, F. E, Sierra Club Bull. Matthe.s, F. E. Paper 160, 1930. Matthes, F. E. Devil's Postpile in the Sierra Nevada and its strange setting : vol. 15, pp. 1-8, 1930. Geologic history of Yosemite Valley : U. S. Geol. Survey Prof. Geography and guidebook of the Sierra Nevada : 16th Internat. Geol. Cong., Guidebook 10, pp. 26-40, 1933. Mnttbi-s. F. E., The Op..loKic hisforv of Mt. Whitney : Sierra Club Bull., vol. 22. pp. 1-18. 1937. Matthes, F. E., Avalanche sculpture in the Sierra Nevada of California : Internat. Assoc. Hydrology Bull. 23, pp. 631-637. 1938. Matthes, F. E., The incomparable valley, Univ. California Press, 160 pp., 1950. Matthes, F. E., Sequoia National Park, Univ. California Press, 136 pp., 19,50. Miller. W. J., Geologic sections across the southern Sierra Nevada of California : Univ. California Dept. Geol. Sci. Bull., vol. 20, pp. 331-360, 1931. Putnam. W. C. Quaternary geology of the June Lake district, California : Geol. Soc. America Bull., vol. 60. pp. 1281-1302, 1949. Reid, J. A., The geomorphogeny of the Sierra Nevada northeast of Lake Tahoe : Univ. California Dept. Geol. Sci. Bull., vol. 6, pp. 89-161, 1911. Webb, R. W., Kern Canyon fault, south Sierra Nevada : Jour. Geology, vol. 44, pp. 631-638, 1936. Webb, R. W., Geomorphology of the middle Kern River basin, southern Sierra Nevada, California: Geol. Soc. America Bull., vol. 57, pp. 355-362, 1946. BASIN-RANGES BASIN-RANGES Margining much of the eastern boundary of California and includ- ing a considerable part of the southeastern section of the state is a section of the Basin-Ranges province which consists of north-trending ranges separated either by completely enclosed basins or by troughs open at one or both ends. In northeastern California, the forces evohnng this province invaded the Modoc section of the great Columbia lava plateau ; the Warner Mountains, which mark the western boundary of the province in this section are composed entirely of lava. On its western side the Basin-Ranges province abuts against the eastern base of the Sierra Xevjula : its southern boundary adjoins the Mojave Desert province. The portion of the Basin-Ranges province lying in California in- cludes part of the belt folded into mountains by the deformation in Jurassic time. During the Cretaceous and earlier part of the Tertiary, this region, like the Sierra Nevada, underwent long erosion together with certain re-elevations, the details of which are little known at present. In the later part of the Tertiary period, the region was sub- jected to further deformation, mostly large- and small-scale fault- ing, though some local folding took place. Along the faults certain blocks were elevated to form a new generation of ranges, while inter- vening blocks were depressed in similar fashion, developing basins or troughs called graben. The result has been the evolution of many discontinuous mountainous areas, most of which are relatively small and not particularly high. Some, like the White-Inyo and Panamint ranges, are much more bulkj- and tower thousands of feet above the bordering lowlands. None of the blocks approaches the Sierra Nevada in size or maximum elevation. Throughout the Basin-Ranges province, elevation and depression have been mostly rotational, giving iUied range and graben blocks, though some horsts (vertically elevated blocks) are present. However, many ranges have been so deeply eroded that their original form cannot be determined. Most of the basin ranges have been examined in reconnaissance fashion, but verj* few have been studied in detail; more is known about certain of the grabens. So actually there is relatively little information about this vast region, though its general history can be partly outlined. In general the province is arid, much of it highly so ; the drjiiess increases from north to south and is more intense in lower than in higher basins. Precipitation in Death Valley, one of the lowest spots, averages about 1.4 inches annually. Independence, in southern Owens Valley (3,957 feet) receives 4.83 inches. Bishop at the north end (4,450 feet), 6.05 inches. Over the ranges, particularly the higher ones, more moisture falls, but there is very little record of this. There is snow on the higher ranges during the colder months, heavy falls on the more northerly and higher ranges, lighter on the lower and more southerly ranges. There also is considerable snow over the northern and higher basins, little or none over those at lower elevation and farther south. The rains are principally summer thunder storms which concentrate over the mountains. Many of the basins contain lakes ; some are permanent, others con- tain water only part of the year or during intervals separated by more than a year. Most of the lakes are saline or alkaline. On the east and west sides of the Warner Mountains in northeastern California are Goose and Middle Lakes. Mono Lake is at the eastern base of the Sierra Nevada below Tioga Pass. Owens Lake in the southeastern part of the valley of that name formerly was fairly large, but the Los Angeles aqueduct which takes water from the head of Owens River has mate- rially reduced its size and will do the same to Mono Lake. Honey Lake, about 70 miles northeast of Reno, Nevada, and just inside the Cali- fornia border, is dry during the summer. The Truckee River, flowing from the north end of Lake Tahoe, empties into Pyramid Lake about 35 miles northeast of Reno. Farther south, some streams flowing down the eastern side of the Sierra Nevada empty into Mono Lake. The Owens River, also supplied from the Sierra Nevada, ends in Owens Lake. Springs emerge at many places in the mountains and basins. Most of the ones in the mountains provide good water, as do some in the basins ; but many of the latter have taken up such quantities of salts as their waters have traveled underground that they are anything but potable. Since good springs are of such importance to desert travelers, signs noting their location or the distance to them have been posted at many places, and the government has published various bulletins giving much information about them. Travel off the main highways in the Basin-Ranges province should not be undertaken without first making careful inquiries about water- ing places and condition of roads; also proper equipment for a region in general quite hostile, but wonderfully interesting, is essential. The concept that the ranges and basins of this geomorphic province originated from dislocations along faults was first advanced in 1873 by G. K. Gilbert of the United States Geological Survey. Another member of the same survey, J. E. Spurr, later attempted to account for them as eroded folded mountains since he was unable to find posi- tive evidence of faulting along the margins of many of the ranges. It is recognized that the elevation and depression of the blocks started at different times in different parts of the province and that it con- (63) 64 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 tinued longer in some areas than in others. Ranges whose elevation started earlier and ended sooner naturally have changed more than those elevated in very late time or those in vehich elevation still con- tinues. Along the older ranges evidence of fault control has been largely or wholly wiped out, but in the more recent ones it is clearly defined. Between the two extremes are intermediate stages which can be recognized when the province is studied as a whole. Therefore the absence of clear-cut fault-controlled land forms by no means proves that such were not once present. The size of the fault blocks varies greatly ; low ones that make dis- tinct ridges are only a few miles long and a mile or so wide. The length of .the largest blocks is several tens of miles or even more than 100 miles, and their highest peaks rise several thousand feet above the basins. The width of these major ranges may be only a few miles or may reach a few tens of miles. In the Basin-Ranges province, the fault basins and troughs be- tween the ranges, such as Owens Valley, Panamint Valley, and Death Valley, are narrow compared with the width of the ranges. The boundary fault systems outlining one or both sides of a range can be recognized easily in most places where elevation still goes on or has recently ceased. In older ranges, the fracture systems have been buried by debris from the ranges, which is piled along their bases as alluvial fans and aprons. These deposits come from streams swollen by flood water, carrj-ing coarse sediment down the canyons through which they flow, and depositing it quickly when their velocity is checked as the water emerges onto the low land at the base of a range. Where several fans unite into a single mass, the deposit is called an alluvial apron. Along some ranges like the White-Inyo on the east side of Owens Valley, the west side of the Panamint Range on the eastern side of the valley of that name, and the Black Range at the southern end of Death Valley, the fans are small and discontinuous, indicating that vigorous recent uplift has interfered with the accumulation of debris at the canyon mouths. Elsewhere the fans have joined to form alluvial aprons which border more or less the entire mountain fronts. Small knobs or ridges of lower ends of divides between canyons may project through the mantle of unconsolidated debris. The heads of fans forming the great aprons may extend far back into the canyons, in some places to the divides which separate them from those on the other side of the range. Alluvial aprons may eventually join in the middle part of fault troughs or basins with valley-like depressions between them down which flash floods from torrential rains occasionally flow. One of the best known and most spectacular sections of the Basin- Ranges province in California is that included between the eastern base of the Sierra Nevada and the ranges on the eastern side of Death Valley, 250 miles away. In this region there are three depressed fault blocks, Owens Valley, Panamint Valley, and Death Valley, which are separated by tilted fault-block ranges. The White-Inyo, Coso, and Argus ranges lie between Owens and Panamint valleys ; Panamint and La.st Chance mountains separate Panamint Valley from Death Valley ; and on the east side of Death Valley are the Grapevine, Funeral, and Black Ranges. The region exhibits great differences of relief: the elevated blocks have peaks ranging from 8,000 to more than 14.000 feet above sea level, but part of Death Valley is more than 270 feet lower than the level of the ocean. The mountains are newly elevated and therefore rugged ; the valleys, on the other hand, have rather even floors. Owens Valley is a long basin whose floor is between 2 and 8 miles wide; the distance between the crests of the bordering Sierra Nevada and White-Inyo Mountains ranges from 15 miles between Bishop and Bigpine to 40 miles at the north end and 25 miles at Owens Lake near the south end. The floor of the graben slopes gently from an elevation of about 3,600 feet at Owens Lake to about 8,000 feet at the northern extremity of the valley. South of Owens Lake the land rises to a broad, low divide at an elevation of 3,670 feet, which separates Owens Valley from Rose Valley to the south. The Poverty. Tungsten, and Alabama Hills are isolated low emi- nences standing above the floor of the valley, but are quite incon- spicuous because of the enormous height and bulk of the great bordering ranges. The hills very likely are small, fault-bounded blocks though they may possibly be bedrock remnants left by erosion. South- west of Bigpine there is a well-preserved volcanic field comprised of explosion cones and lava flows, consisting predominantly of basaltic material, although slightly older rhyolitic rocks, including glassy rocks of various types, are present. Crater Mountain, the highest point in the field, is a cone with crater in the top which rises about 2,000 feet above the floor of Owens Valley. All evidence points to the subsidence of the Owens Valley block along a series of parallel boundary faults, one at the base of the Sierra Nevada and the other at the base of the Inyo- White Mountains. The graben bedrock in turn is broken by minor faults some paralleling and some lying transverse to the boundary faults. The subsidence of Owens Valley has not been uniform. Partial rotation has occurred and un- doubtedly the lesser blocks have moved within the main one. For example the basin holding Owens Lake seems to have been evolved by this uneven sinking and partial rotation of one of the blocks com- posing the graben. The rocks composing the Alabama Hills are Triassic or Jurassic volcanics which are intruded by granitoid rock unquestionably of the same age as that of the batholithic complex in the Sierra Nevada — 1952) BASIN-RANGES 65 Fig. 44. View of Owens Valley and the southern end of the Inyo- White Mountains from the Sierra Nevada near Mount Whitney. The low Alabama Hills in the middle ground show remnants of the ancient landscape found in the upper part of the Sierra Nevada around Mount Whitney. late Jurassic or early Cretaceous. The oldest rocks in the hills are therefore less than 200 million years old. The topography of the Ala- bama Hills contrasts strongly with that of the nearby Sierran or Inyo- White Mountains fronts, but it is similar to that of the upland around Mount Whitney, where there are well-preserved remnants of land- scape far more ancient than that of the great scarps marking the boundaries of the ranges. It is probable that the Alabama Hills are a fragment of this old landscape separated both from the Sierran upland and from the bedrock under Owens Valley by the great dis- locations which have occurred At the base of the Sierra Nevada, there is an alluvial apron com- posed of debris brought from the canyons by the mountain streams. The individual fans and the apron as a whole have a considerable slope, 10 to 15 degrees. Because of the steepness of this slope sediment 66 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 I 1' Flu. 4."!. The great battered fault .scarp of the Sierra Nevada rises about 11,000 feet above the Hour of Owens Valley in the vicinity of Lone Tine (foreground). The houndary fault system lies immediately at the base of the range. The Alabama Hills are in the middle ground. At the base of the range is an alluvial apron. .Yorman E. A. Hinds, OEOMORPIIOLOOY (copyright WiS hy Prentice-Hall, Inc., New York). Reproduced hy permission of the puhHshcr. which the streams carry, especially during time of flood, when the most active addition to the fans occurs, is coarse ; where the slope flattens abruptly, mostly fine fragments are carried. On the eastern side of the valley, the fans along the White-Inyo Range are isolated from each other and are comparatively small. Very recent, low fault scarps are present in Owens Valley indi- cating movement either along the Sierran boundary fault system or along faults roughly parallel to it. Near Lone Pine several small scarps cut late stream deposits and were evolved by dislocations at the time of the very severe earthquake in 1872 which resulted in much loss of life and damage in the town. Because the scarps are in unconsolidated debris, they have been considerably eroded ; in height they range from a few feet to about 25 feet. Recent scarps may be seen west of Bigpine also, one at least being the product of the 1872 disturbance. BASIN-RANGES Fio. 40. Alluvial apron composed of large and small fans on the eastern side of the Sierra Nevada in arid Owens Valley, yorman E. A. Hindi, OEOilORPIIOLOOY (copyright I9^S by Prentice-Uall, Inc., New York). Reproduced by permiaaion of the publisher. There are many others on the west side of Owens Valley, most of them formed prior to 1872. Like those near Lone Pine, most of these declivi- ties face eastward, but some are directed toward the Sierra Nevada. Horizontal as well as vertical movements are recorded. The total evi- dence shows that many recent minor dislocations have occurred along a series of roughly parallel faults through a zone 7 or 8 miles wide. On the eastern side of the valley, recent scarps are not common ; one, several feet high developed in 1872, is visible just north of Swan- sea where it traverses an ancient beach of Owens Lake. These recent movements are considered evidence of continuation of the settling of the sunken blocks, for similar features have not been recorded within the main mass of the Sierra Nevada. 68 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. i:)S if FlQ. 47. Red Mountain, an explosion or cinder cone erupted through a granite hill along a fault parallel to the main boundary fault of the Sierra Nevada. The cone is about (iOO feet high. Hound about are numerous flows of basalt. This volcanic field lies in Owens Valley. Between Bigpine and Independence near the eastern base of the Sierra Nevada there is a volcanic field comprised of a considerable number of cinder cones and associated lava flows. Some of the cones are on faults along which there was movement as late as 1872. Crater Mountain, highest of the group, stands about 2,000 feet above the floor of Owens Valley, but this considerable elevation results prin- cipally from the fact that the explosions burst through a granite hill rising nearly 1,400 feet above the valley, hence the cone itself is not particularly imposing. Most of the cones are on the alluvial apron projecting into Owens Valley from the base of the Sierra Nevada, but some lie along the lower bedrock slope of the range. The most intense volcanic activity occurred between Taboose and Sawmill Creeks where large flows of basalt spread far over the valley floor. The flows are extremely rough, 19521 BASIN-RANGES 69 the surfaces being wild jumbles of clinkery blocks. The lower ends of the flows have been partly covered by later alluvium, but because of inequalities in their surfaces basaltic eminences project through the deposits. The most perfectly formed cone is Red Mountain which rises about 600 feet above the alluvial apron. An extensive basalt flow poured from the vent, but the crater rim extends unbroken over the head of the flow indicating that the last phase of activity at this center was explosive. The cone is built largely of reddish fragments of lava, hence its name; most of the debris is angular and individual chunks reach an average maximum diameter of about 6 inches, but some bombs which were erupted measured at least 4 feet across. Red Mountain has suffered some erosion and also burial of part of its lower slopes by alluvium, but at first glance it looks as though it were exceedingly recent. A large but rather imperfectly formed cone stands on the upper end of the alluvial apron between Division and Sawmill Creeks ; scat- tered over its top are many large granite boulders evidently derived from debris of the apron as the eruptions blasted through it. At an elevation of about 7,000 feet on Sawmill Creek explosive eruptions occurred and basaltic lava flowed from the vent to the mouth of the canyon. Considerable basalt is present near the base of the Inyo Mountains near Aberdeen on the east side of Owens VaUey. Explosions also took place forming a number of imperfect cinder cones, closing the volcanic cycle — one that was probably contemporaneous with that on the west side of the vaUey. Red Mountain, previously referred to, stands at the south end of a clearly defined scarp in the alluWum developed at the time of the 1872 earthquake. A short distance to the north along the same scarp there is a minor quantity of exploded debris which did not form a complete cone. Still farther north on the projection of the same frac- ture is Crater Mountain. Thus three centers of eruption are located along this fault, which evidently is still active. A large cinder cone west of Fish Springs School was broken by a recent fault along which the displacement amounted to about 50 feet ; before it occurred the lower slope of the volcano had been partially buried by alluvium. On the eastern side of most of Owens Valley is a massive block 110 miles long, with one or two of its highest peaks closely approaching the maximum elevations in the Sierra Nevada. White Mountain Peak stands 14,242 feet above sea level. The range is a continuous mass though there is a depression in the central part culminating in West- gaard Pass (elevation 7,276 feet) which lies east of Bigpine. It is generally known as the White Mountains, though the southern end may still be referred to as the Inyo Mountains. Although there is no real demarcation between the two parts, in consideration of local preference, the term White-Inyo is used in this description. On the north, the White-Inyo Mountains terminate quite abruptly at Mount Montgomery ; at the southern end there is a broad depres- sion separating them from the Coso Mountains which border the southern part of Owens Valley on the eastern side. The south end of the White-Inyo block therefore is much less clearly defined than the northern. Although the average elevation of the range crest is high, more than 10,000 feet, it is considerably less than that of the corres- ponding part of the Sierra Nevada on the west side of Owens Valley, hence it is somewhat dwarfed by its greater neighbor. 7 Fig. 48. The Inyo Mountains are a tilted fault block in the Basin-Ranges Province. Rocks in the In.vo Mountains have been intensely folded and are broken by great faults, as shown on the cross-section. A large mass of intrusive granite shows to the west of Saline Valley. After Knopf and Kirk. The west side of the White-Inyo range slopes abruptly to the floor of Owens Valley and is only little less spectacular than the east Sierran front. The western base against Owens Valley is sharply defined, but its eastern margin is much less clear. The northern part of the eastern side is marked by the edge of Fish Lake Valley. Between this graben and Saline Valley farther south, there is an irregular mountainous area not clearly separated from the Inyo Range on the west and the mountains to the east. Saline Valley is an elliptical depression whose floor is about 2,500 feet lower than that of Owens Valley. The eastern face of the Inyo Mountains fronting on this vaUey is quite as abrupt and majestic as the eastern side of the Sierra Nevada. The White-Inyo Range is a gigantic fault block, but the evidence of the dislocations producing it is most clearly shown at the two extremities. At the northern end, the inter-canyon spurs projecting into Owens Valley are terminated by remarkably large, clearly defined triangular facets whose sharp edges and geometric perfection make them extraordinarih- fine illustrations of this important feature of recently uplifted fault blocks. At the southern end, which is almost completely covered by a thick mass of basaltic lava flows overlying an exceedingly even elevated erosion surface, actual dislocations of the flows are visible. Between the two ends of the range the evidence is less conspicuous, probably because the dislocation has been distributed along parallel fractures and this has prevented the development of prominent triangular facets. Such movements as have occurred in the 70 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. IJ" 4. ^\ * ' '•%. 't -*^» «>» / \% ^^t:. ■* ^ ■ ^^"^^ Fio. 49. The Whitc-Inyo Mountains on tl ast snli i.l ( iwins Valley are a fault-block rani,-' n-ni. riMi ^Tiiiiller than the Sierra Nevada. Evidence of faulting is prom- inent alonK the western front of the range. Owens Lake lying in the lowest part of the fault basin between tlie two ranges shows in the foreground. A'ormiin K. A. Ilinda, QEOMORPHOLOOY (copyright 191ii by Prenticellali, Inc., New York). Reproduced by permission of the puilisher. 1952] BASIN-RANGES 71 middle section appear to have taken place along faults which parallel the boundary fault for a distance and then run into the body of the range. Other evidence of the fault block origin of the White-Inyo Moun- tains is the straightness of the western front and its independence of the bedrock, for the front transgresses the trend of the rock layers as is commonly the case in fault block ranges. The eastern front does not provide so straight a base as the western side. However, the topog- raphy cif the eastern front in many places shows extensive faulting, especially in the great escarpment margining Saline Valley where verj- prominent triangular facets are present. Further evidence in the same place is the badly crushed rock along this escarpment which could only have been produced during dislocation along a major fault system. The slopes of the west side of the Argus Range, and the east and west sides of the Coso, Panamint, and Black Ranges are aU exceed- ingly steep, not greatly battered fault scarps. The west sides of the Coso, Argus, and Panamint Ranges also include minor scarps known to have been developed by step-faulting, for in many places traces of these lesser faults can be observed, as well as displacements along them. Highway 190 crosses both the Coso and Panamint Ranges on its way to Death Valley. Perhaps the most conspicuous fault zone bounds the east side of Panamint Valley and marks the base of the Panamint Range, for the dislocation here has been very great. There are evidences of recent movement, particularly south of Wildrose Canyon where the range front is extremely high and abrupt and the alluvial fans at the mouths of the canyons are feebly developed. For this reason the lowest part of Panamint Valley is near the base of the range rather than near the center of the valley as is normally the case. However, because the volume of debris in the present fans is only a small proportion of the total removed from the Panamint Range in the erosion of the canyons on its western side, Panamint Valley must have sunk as the range was elevated and older fans have been buried by those growing from the eastern side of the Argus Range on the opposite side of Panamint Valley. Even some of the new fans along the Panamint Range have been broken by recent faulting and parts of them elevated. In some places, the bedrock scarp, which rises to a height of 2,000 and 3,000 feet, slopes as much as 35 degrees ; apparently it is the continuous footwall of the fault so recently exposed by dislocations. The rock in which the facets are cut is greatly crushed, sheared, and discolored, additional evidence of the presence of the surface of the fault. One of the most striking bits of evidence favoring the recency of the faulting along the west side of the Panamint Range is a large north- trending graben in the alluvium just south of Wildrose Canyon. This depression is more than 3 miles long, nearly a mile wide, and 400 feet deep in its deepest part. Between the Coso and Argus Ranges is a hiUy area of low relief which is a somewhat deformed and eroded portion of an old landscape found in the higher parts of the ranges. This section includes Coso Valley and the hills immediately to the east, the Darwin Hills, and also Darwin Wash. Lower Darwin Wash, east of the Darwin Hills, is an alluviated area in which white lake beds indicate the presence of a former water body. Headward erosion of Darwin Canyon, a narrow gorge which empties into Panamint Valley, has recently drained the lake ; as a result the base of erosion for most of the intermittent streams draining Darwin Hills and the west slope of the Argus Range has been lowered about 2,000 feet, causing considerable dissection of the lake beds and the alluvium in Darwin Wash. Remnants of the ancient erosion surface are found elsewhere in the mountain ranges, and are being progressively cut to pieces by head- ward erosion of canyons which have been cut during the late uplift of the fault blocks. At one time this surface appears to have been verj- widespread over the region and probably was continuous with rem- nants found in the Sierra Nevada. In the western part of the section under present discussion, thin flows of basalt spread across the ero- sional plain completely burj-ing much of it, but, in places, hills several hundred feet high rose above the general level and were partially or completely surrounded but not covered by the flows. The age of this erosion surface which shows in the Sierra Nevada, the Coso, the Argrus, and Panamint Ranges at least, is of interest and some information is given by geological features in the Coso Range and in the Mojave Desert farther south which indicates that the surface had been evolved by the late part of the Pliocene or the very early Pleistocene epoch. Remnants of a similar surface have been reported from ranges in southwestern Nevada and possibly from the San Bernardino Moun- tains of southern California. If all are part of a once continuous land- scape, a large area had been reduced to most modest relief when the late faulting occurred. Death Valley, one of California's most interesting and spectacular scenic areas, is a completely enclosed graben about 130 miles long and from 6 to 14 miles wide. On the western side. Panamint Mountains rise to a highest elevation of more than 11,000 feet : the Last Chance Range to the north is somewhat lower. Along the eastern margin, three ranges, the Grapevine at the north, the Funeral, and the Black at the south complete the enclosure. Each of these is distinctly lower than the Panamint. Death Valley basin and the bordering ranges owe their origin to such profound fracturing as has been described in areas farther west. The deepest part of Death Valley, lying between the Panamint and EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 Black Mountains, has been lowered below sea level, though the region as we see it today has not been invaded by the ocean. However, in the past, before development of the present relief, the sea invaded this part of California several times, as is proved by the wealth of marine fossils contained in many rock layers exposed in the ranges. t-^^Si." Fig. TiO. The low cliff in the alluvium at the base of the Panamiut Range in Death Valley is a fault scarp formed by recent movement along one of the fractures close to the base of the range. Photo courtesy National Park Service. The faulting, which started in the late part of the Pliocene epoch and is still going on, is extremely complex. Its effects show best along the eastern face of the Black Range where the most recent and most active movements have occurred. The lower slope of this range is extremely steep ; although it has suffered some erosion, it is one of the best preserved fault scarps in the United States. The road along the east side of Death Valley from Furnace Creek south runs close to the scarp and affords easy access. For 15 miles below Furnace Creek, the boundary fault system cuts across Tertiary rocks, but, farther south, there are precipitous slopes in ancient, resistant formations which roughly outline the surface of the fault. Three miles north of Bad- water, the deepest point in the valley (270 feet below sea level), a fault between the Tertiary and the very old rocks is clearly exposed for many thousands of feet where it extends upward into the range, and the fault surface is continuous with the vallej^vard slope of the ancient rock farther to the south. Because of the height of the ranges around Death Valley and their ciiiiseiniently steep slopes, a host of val!p_vs has been eroded into them and the streams have carried great quantities of debris into the basin forming alluvial fans and aprons. Along the Black Range, the fans are small and discontinuous and much of the lower part of the range front is abnormally steep, both part of the evidence that this block has been recently elevated to a considerable extent or that tlir valley has sunk. Elsewhere the fans have united to form aprons having mod- erately steep slopes from the toe of the deposit to its upper end which maj- be miles up the canyons. This is notably true along the west front of the Panamint Range where the fan heads extend far back into the mountains. The steep slopes of the fans and the coarse debris compos- ing them testifies to their speedy formation. In places the fans are broken by low scarps, indicating the presence of active faults beneath them. A very good example may be seen about a mile south of Furnace Creek Inn where a scarp lies just east of the hi^'liway and oxteiuis parallel to it for some distance ; another is at the base of the Panamint Range. The floor of a considerable portion of southern Death Valley is made of rock salt formed by the evaporation of a large lake. As shown previously, during the climaxes of the glacial stages, more snow fell on the California mountains and in most places over the lowlands more rain than does today. At various places around Death Valley, there are wave-cut terraces and deposits as much as 600 feet above the valley floor. These terraces, although faintly outlined, can be distinguished, Fig. 51. Salt left by evaporation of lake in Death Valley is bcinc ciissolvrd by water falling on the valley floor and by water mipratinc downward from the adja- cent ranges. The water is an exceedingly bitter brine. Photo by Willard. 1952] BASIX-RANGES 73 Fig. 52. Sketch of Death Valley from the western side. Death Valley is a long narrow fault basin, part of which has sunk below sea level as the adjacent ranges have risen. At the base of the Panamint Range, on skyline, is a great alluvial apron formed from debris which streams have brought out of the canyons. The rough land in the foreground is weathered salt left when the large lake that formerly filled the basin evaporated. Photo courtesy R. N. Wheeler. as for example at Mormon Point and on Shore Line Butte, which is a hill of black basaltic lava rising above the valley floor, a mile north- west of Ashford Mill. This ancient lake has been given the name of Manly, for one of the early explorers in this region. Evidences of other lakes which occupied the valley at earlier times has been gained from borings into the sediments. A well 1,000 feet deep along the road across the Devil's Golf Course, passed through alternate beds of clay and salt without reaching bedrock. Each pair of salt and clay layers represents the evaporation of a lake, the salt representing the final product as the water disappeared. In the middle part of Death Valley, principally north of the road leading to Stovepipe Wells, is a small group of sand dunes made up largely of quartz sand. Considerably north of the sand dunes and only a few miles from the famous Death Valley Scotty 's Castle are the Ubehebe Craters, a group of small cones built by explosive eruption of fragments of basaltic lava. Probably these cones overlie one of the faults traversing the graben bedrock, and were erupted only a few hundred years ago. The craters in the tops of the cones are well presers'ed and in their walls the various layers of fragments blown out by the different ex- plosions are well marked. The volcanic cycle seems to have been a brief one, as is normally the case with volcanoes built solely by explosion. In the southern part of Death Valley there has been liberal outpouring of basaltic lava along the faults. Cenozoic deposits present in the valley are especially notable for their high coloring, as for example along the base of the Black Range south of Furnace Creek Inn, where a striking badland area has been developed by the occasional torrential storms. Because the rocks are quite unprotected by vegetation and surface slopes are steep, the sheet and flash floods are literally ripping the deposit to pieces. A labyrinth 74 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 I-'k;. .'n. Sand diinps near Stovppiiip WpHs in l>ert(h Valley. The dunp.s are com- IMi.sed nf loose sand drifted o\ er the ari'a \>y wind, and piled a;,'nin.st ol>.stacles, even- tiiall.v coxerin;: them. I'holo voitttfjtii Stttunial I'ork Servirc, of deep, narrow gorgres lies between high, sharp-crested ridges. Most of the sediineiits are brilliant yellow in color but there are many other shades. In the Tertiary deposits are the famous borax minerals mined long a7. Mono I>ake on the cast side of the Sierra Nevada below Tioga Pass. Around the lake are the terrace deposits and wave-cut cliffs left by former Lake Russell. /l/(er /. V. Rutselt. m 78 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 about 650 feet above the present surface of Mono Lake. In places the terraces were eroded by waves into the Sierran bedrock or into mo- raines which had been left by glaciers descending from the great range; elsewhere they were constructed of sediment deposited while for a time the lake stood at various levels and then were exposed as the waters fell to lower positions. Most of the debris which tributary streams carried into the lake is silt (very finely divided rock frag- ments), the remainder being sand and gravel. There is almost no clay in the deposits. The lake terraces now are a rather desolate area covered principally by sage brush. The small town of Leevining at the junction of the Tioga Pass road and Highway 385 stands on one of these terraces, a wide one, 380 feet above Mono Lake and the same terrace makes the broad expanse of Pumice Valley farther south. Streams flowing from the Sierra Nevada into Mono Lake, such as Rush and Leevining, have cut gorges 300 feet deep into the terrace deposits since the recession of the valley glaciers evolved during the fourth glacial stage. In the Mono Lake region on the Sierran side four glacial stages have been recognized by moraines left as the various glaciers receded. Records of the last two, the Tahoe and succeeding Tioga, are far better preserved than those of the earlier pair, for the later glaciers destroyed or greatly modified the earlier deposits. Lateral moraines project from the mouths of the larger canyons, extending beyond the base of the Sierra Nevada as a series of crescentic ridges whose slopes are broad and culminate in narrow crests. Some of the embankments rise at least 800 feet above the lake terraces which they nearly surround. There are also terminal moraines belonging to the last glacial stage but they are small as contrasted with the lateral banks. The moraines are chiefly granitoid debris, including great boulders embedded in masses of sand and gravel. The extent of the morainal belt and the volume of debris included in it is striking testi- mony of the vigor of glacial erosion. One of the most remarkable topographic features of this area is the anamolous horseshoe valley of Reversed and Rush creeks, which is jjartly occupied by four lakes, June, Gull, Silver, and Grant. The name Reversed Creek is appropriate, for the creek flows from Gull Lake toward the mountains rather than toward the low country as does the normal drainage ; it joins Rush Creek at the bend of the horseshoe, and Rush Creek flows to Grant Lake in the western arm of the loop. June Lake has no outlet except a small drainage canal cut across the marshy ground separating it from Gull Lake. The origin of this strange valley pattern has been explained in various ways. Two principal fault systems cross the area, an outer one which is the main boundary system along the eastern base of the Sierra Nevada and an inner one which runs along the escarpments of Mount Parker, Mount Wood, and San Joaquin Mountain, and under the trough occupied by Silver Lake. This second system probably has been the more important in the evolution of Reversed Creek-Rush Creek canyon. It is assumed that two eastward flowing streams crossed the area and were separated by a low divide near the south end of present Silver Lake. A tributary of one of these streams, eroding head- ward along the weak crushed zone of the inner fault system, diverted the other stream into itself. The probability is that Rush Creek (the western stream) captured Reversed Creek which lies to the east because it had the advantage of working in less resistant rock. Whether or not -■LOMCT£«S ■ EOGW «£*■£»». .'* Fio. 58. Map of Mono cones and surrounding area. A/(er n*. C. Putnam. 1952] BASIN-RANGES 79 the capture was made before the end of the next to the last (Tahoe) glacial stage has not yet been determined. The problem of the reversal of drainage direction appears to be related to the relative resistance of the bedrock in the area and the relative erosional efficiency of the two branches of the Rush Creek glacier. Rocks in the June Lake area are more resistant than those about Grant Lake, hence glacial attack upon the former was less effec- tive than on the latter. The June Lake branch of the Rush Creek glacier averaged about 2.2 miles in length, as compared with the Grant Lake arm which was only 1 mile ; the latter not only was thicker (1,800 feet as compared with 1,300 feet), but had the advantage of being concen- trated in a narrow, well-defined channel. Therefore glacial erosion was more successful in the Grant Lake than in the June Lake branch of the glacier. The depth of glacial erosion also is closely related to the fracturing of the rock, the trough at Silver Lake being deeper where the faulting and jointing has been most intense and shallower where the ice traveled over rock in which the joints are widely spaced, as immediately west of Gull Lake. Thus the valley was deepened less in the June Lake area and more around Grant Lake, causing the present Reversed Creek to flow in an abnormal direction as compared with other streams in the region. Perhaps the most unique feature of the Mono Lake region is the range of volcanic mountains called the Mono Craters, extending from the south side of the lake for about 10 miles southward, and clearly visible from Highway 395. The highest of the mountains stands about 2,700 feet above the surrounding rolling plain and the range as a whole would be quite conspicuous were it not dwarfed by the enormous bulk and height of the Sierra Nevada a few mUes to the west. ^^%.- Fio. 59. Panoramic sketch of the west .side of the Mono cones, showing cones, domes, and coulees. After U'. C. Putnam. The Mono Craters are a group of pumice cones in most of which have risen donics of obsidian (volcanic glass of granitic composition), some so bulky that they flowed over the cone walls, advancing upon the adjacent plain as short, steep-fronted and steep-sided flows, called coulees. The range, which is crescentic in groundplan bending toward the east, is divided into three nearly equal parts by the projection of ■I Kio. (M). Stages in development of the Mono cones, volcanic domes, and coulees. 1, Low cones formed by explosions of rhyolite pumice. 2, Rise of vol- canic dome in crater of cone, either flush with cone rim or projeclinp far above it. 3, Too hish dome elevation caused part of mass to overflow crater rim forming short, thick flow called a coulee, covered with blocks of obsidian. After W.C.Putnam. I 80 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 the two largest coulees nearly at right angles to the trend of the range. The northern of these two principal coulees shows only on the eastern side of the mountains, but the southern is divided nearly equally between the two sides. The Mono Range rises highest near its central part, where three turret-shaped domes of nearly equal size are present, the middle one forming the highest peak. North of the northern coulee, there are five domes and two smaller coulees; south of the southern coulee are six domes and four large explosion pits. The northernmost dome is isolated from the rest of the range, standing about a mile from it and just south of Mono Lake. This cone and dome, which is called Panum Crater, is low, the dome rising about to the level of the crater wall, from which it is separated by a trench or moat. The generation of most of the volcanic forms of the Mono Range has followed a definite sequence. At first explosions of moderate violence formed shallow, bowl-shaped depressions much resembling large shell holes. Highly gas-charged lava was blasted out building low explosion cones made of pumice fragments. Following the explo- sive episode, largely solid, cylindrical columns of obsidian rose in the craters, forming domes of various heights. If the domes were suffi- ciently elevated, they contained enough liquid — though very sticky — lava to cause the rising mass to spill over the rim of the cone, generat- ing the coulees which in their outer parts are chaotic jumbles of angular boulders. In the north and south major coulees separate outpourings coalesced to form more extensive flows. Wlien the domes ceased rising in the craters, most of the conduits were sealed. There was but one case of renewed explosive activity which produced the deep pit called the Caldera at the south end of the chain. This is a steep-sided double crater occupying the center of an obsidian dome extensively destroyed by explosion. Great streams of talus coming from the higher domes have almost completely masked the pumice cones in which they rose. The obsidian boulders forming the talus were generated by fragmentation of the steep domes as they cooled and contracted and also by later frost wedging which has further disrupted them. Two nearly complete pumice cones may be seen near the summit of the Mono Range between the southernmost of the three central domes and the south major coulee. The Devil's Punchbowl, near Highway 395, is a small but well-preserved explosion cone whose crater is about 1,200 feet in diameter and 140 feet deep ; in the bottom is a small obsidian plug about 250 feet across, rising about 40 feet above the crater floor. Panum Crater, just south of Mono Lake, illustrates a somewhat more advanced stage of dome development. The cone is low, but stands out distinctly from the rolUng plain round about. Separated from its rim b_\- a deep trench or moat is a steep-sided obsidian dome which rose after the preliminary explosions had formed the cone. The top of the dome, like that of others, is a wild jumble of spires, crags, and loosely piled blocks of obsidian. The Caldera at the south end of the range, as previously noted, is the product of explosion at the end instead of the beginning of the volcanic cycle. This crater is comprised of a large, flat-floored bowl open at the west and a small, deep pit blown through the north wall of the main depression. Originally it was believed that collapse of the dome had developed the depressions, hence the name Caldera; but later studies indicate that explosions were responsible. The tops of the obsidian cliffs forming the walls of the Caldera are covered by 30 to 50 feet of volcanic ash and the secondary pit is clearly of explosive origin, differing from the larger one only in size. There is no evidence of faulting, which should be present if the basins had been formed by collapse. The volcanic cycle which built the Mono Craters started in late Pleistocene time. Explosive activity began during the last high stand of Lake Russell for pumice is interlayered with lake sediments, but no lake shore lines cut the more recent cones, notably Panum Crater which is close to the lake and stands only 150 feet above its level. The explo- sion cones at the southwest end of the range were erupted through the floor of one of the small late Pleistocene lakes lying mainly to the east of the range. Pumice blasted out by the explosions mantles moraines of the last glacial stage, but there is no sign of activity today anywhere in the range. Warner Mountains A splendid example of a fault block range in northeastern Cali- fornia is the Warner Range, a narrow, rugged mountainous mass about 87 miles long which extends from southern Oregon across Modoc County, California, into Lassen County. On the east it projects slightly into Nevada. At the northern end, the range merges into a high plateau between Abert Lake and Warner Valley and does the same at the opposite extremity just east of the Madeline Plains in Lassen County. The width of the Warner Mountains ranges from 8 to 20 miles, the narrowest part being slightly north of Alturas, county seat of Modoc County. The highest peaks, located southeast of Alturas, are nearly 11,000 feet, but most are closer to 8,000 feet. The eastern front of the range, rising abruptly from arid Surprise Valley, is a spectacular, battered fault scarp along the base of which runs the road leading north and south of Cedarville. The northern half of the western side, as far south as Fandango Valley, closely resembles the eastern front. Fandango Valley is a major embayment which almost cuts the range in two, but has no counterpart on the eastern side. South of this valley, the western front is much less imposing, since the faulting is complex and the mountains rise in a 1952] BASIN-RANGES 81 Fio. 61. i'anum Crater south of Mono Lake and part of the Mono volcanic range. lu I'anum Cr.TUT auJ the une inimediatel.v south, volcanic domes have risen about to the level of the crater rim from which they are separated by a narrow trench or moat. series of steps, each repre,senting a block boiinded by faults. A splendid view of the western part of the Warner Mountains may be obtained along Highway 395 leading north and south of Alturas. The southern half of the western front of the Warner Mountains differs widely from the northern. There is no conspicuous escarpment, only a long unbroken slope from the base to the crest of the range. The surface of this slope for the most part coincides with the upper- most layer of lava composing the mountains. From the picture just drawn, it is evident that the northern end of the Warner Mountains is a horst or vertically elevated fault block bounded by battered scarps on both sides ; also that the southern sec- tion is a tilted fault block with the great scarp on the eastern side. The change from the one to the other is gradual. The uplands of the horst are comparatively smooth lava-capped areas, little modified by erosion, which are being destroyed by canyons being eroded headward into them from both sides of the range. i 82 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 Fio. 62. I'anorama of the eroded fault scarp forming the eastern side of the Warner Range in eastern Modoc County. The western slope of the range is a gently inclined, not greatly dissected erosion surface. Showing at the base of the range is part of Surprise Valley. Photo hy C. W. Cheaterman. West of Goose Lake Valley and the north part of Pit River Valley is an extensive plateau known as The Gardens. Most of its surface is a smooth lava cap but locally small domes of rhyolite and obsidian rise above it. Still farther west, toward the boundary of Modoc County, there has been much recent volcanic activity and large areas of the plateau are covered by lava flows, explosion cones, and other extrusive forms. This spntion is known as the Mndnc Lhvh Beds or tlio Burnt Lava Country. Surprise Valley east of the Warner Mountains is a larger trough than that on the western side. Along its eastern margin rises the Hays Canyon Range, which is bounded by a battered fault scarp, but one far less striking than the eastern declivity of the Warner Range. The rocks composing the Warner Mountains are principally lava flows and fragmental deposits which lay in essentially horizontal position at the time of the elevation of the fault block. These volcanics were erupted during a long but intermittent cycle which saw a huge section of northeastern California and still greater territory in Oregon, Washington, Idaho, and Nevada turned into one of the most gigantic volcanic fields of the earth. It is believed that prior to the deformation which produced the ranges and grabens of this region, an extensive rather even-surfaced plain existed. Below this plain the lava flows and fragmental deposits were essentially parallel with its surface. Over some sections very late basalt flows were erupted, covering them in places to depths of 600 feet. Deformation, starting toward the end of the Pliocene or in the early pai-t of the I'leistocPiic epoch, pi-iKJuced ii lircnnj dome willi its crest in the Warner block; as it evolved the dome fractured. The Warner and Hays Canyon ranges rose, while Goose Lake, Surprise Valley, Long Valley, and other grabens moved downward. There does not appear to have been much compression outside of the broad dom- ing, the principal deformation being the differential vertical disloca- tions. The evidence for the development of this breaking dome comes from the increase in elevation from the Gardens to the summit of the Warner Range and the decrease eastward from the summit of Hays Canyon Range to its base. In a north-south direction, the greatest height of the Warner Range is in its central part with decrease toward both ends. The arch in this direction, however, quite certainly resulted from differential elevation of blocks bounded by faults and not from 1952] BASIN-RANGES 83 compression. The Warner Range, therefore, is a mosaic of fault- bounded masses which have behaved in different fashions as the deformation proceeded. Indication of continued sinking of the grabens comes from the location of lakes against the base of the steepest escarpments, where apparently the movement is most active. If this dislocation were not still going on, erosional waste from the ranges which forms alluvial fans and aprons at their bases would long since have forced the lakes farther outward and the deepest parts of the grabens would be toward their centers. The broad playas of Surprise Valley, deposits formed in a lake which formerly lay against the base of the "Warner Range, Lake Annia in Jess Valley, Alkali Lake in Long Valley, High Rocky Lake in High Rocky Valley, Abort Lake, and others hug the steep escarpments. All of this evidence testifies to the recency of evolution of the major features of this remarkable landscape. Surprise Valley, the graben between the Warner Range and fault block mountains to the east, starts 7 miles south of the Oregon border on the east side of the Warner Mountains and extends for about 54 miles southward. An average width of about 8 miles is maintained over this distance, though there is narrowing at the northern and southern ends. At present there is no outlet from the valley. Perhaps the most notable feature is evidence of series of large lakes called Surprise Lake, which existed during one or more of the recent glacial stages. These great bodies of water which reached a maximum depth of 550 feet not only filled practically all of Surprise Valley but overflowed a narrow divide at its southern end, covering Duck Flats. Evidence seems to indicate that at least two lakes were separated by a time of aridity, when the valley became very dry and probably all of the water was evaporated. The old shore lines are indicated by wave-cut cliffs and terraces, and by delta and other deposits. The highest shoreline is particularly well marked and extends around the valley in virtually undamaged condition. The Duck Plat extension spread mostly over a surface of basalt which probably already had on it a growing lake, for this area also is an entlo.sed basin. In Duck Flat the highest level shore line is best developed, indicating that at this stage the lake remained relatively stable for a considerable period. Whether the water overflowed bar- riers into other basins is not known, though this is quite possible. As the water of Lake Surprise lowered, the Duck Flat section was isolated from the main body as is shown by an outlet gorge cut between the two with the slope toward Duck Flat. For a time two lakes existed with that in Duck Flat standing about 200 feet below that in Surprise Valley, but wlioii Lake Surprise was still 200 feet deep, overflow through the gorge into Duck Flat ended and its lake probably dis- appeared rather soon because it seems to have been maintained prin- cipally by water from the larger body. Finally the main lake itself was completely evaporated. On many maps of Surprise Valley, three large lakes are shown which are called by some Alkali Lakes and by others Upper, Middle, and Lower Lakes. The northern or Upper Lake when filled is a unit. Middle Lake also was a unit when it contained water, but, some years ago, it was divided by the construction of a causeway east from Cedar- li.!. Tauuruma of Fundango Vallij-, a structural J.jprcssion obliquely crossing part of the Warner fault block range in eastern Modoc County. Cross faulting apparentlj- has be«a the principal cause of the formation of the valley. Pkolo bii C. W. CAettn-nxin. 84 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 Fio. 04. Pinnacles eroded in volcanic rbyolite tuff in the Warner Mountains. Most of the rocka of the raiifje are basalt tiows. Photo by C. W. Chestcrman. 1952) BASIN-RANGES 85 Western fciTTyTTi] Hummocks [ H 5p« LliiiiU Surfoce E I Surface LillUAproo |, 1 j l|Or<.,slor.d» JVolleij 5lofw3 HAYSi CANYON RANGE FRONT Scale ?'?>;! Fig. 65. Map of Surprise Valley and the adjacent Warner and Hays Canyon Ranges. After R. J. Russell. ville, the principal town in Surprise Valley. The southern or Lower Lake, in contrast, is an aggregate of smaller lakes, each of which is a playa but does not become dry simultaneously with the others. Since the waters of the larger lakes evaporate so that only isolated depres- sions are filled, it has been customary to give names to the small residuals. Thus the term Eagleville Lake is much more significant in Surprise Valley than Lower Lake and refers to a small portion near the town of Eagleville. This lake is said to have dried up only once in the memory of many of the oldest inhabitants. Upper Lake when filled is about 13 miles long and 4 miles wide, an overflow channel into Middle Lake preventing further growth. In normally wet years, it decreases to about half its major size during the dry season, but in dry years it disappears. In the winter the frozen surface of this lake often serves as a highway between Lake City and Fort Bidwell. When completely dry, the playa surface is also used for traffic. L'pper Lake normally does not become as completely dry as the two lower ones. Middle Lake is nearly as wide as the upper one and is 18 miles long. The northern 4 miles have been isolated by the Cedarville causeway and is dry most of the time during the summer. The main lower part generally contains water until early summer and one or two pools usually remain along its western margin. Lower Lake is much smaller than either Middle Lake or ITpper Lake. Toward the south is a broad, continuous playa but northward this is broken, chiefly because of wind-blown accumulations which form isolated basins. Nearly everv vear water overflows from Middle into the Lower lakes, but during the summer most of the basins are dry. However, even in the driest years, a few depressions in the western side of the largest playa contain water coming from nearby hot springs. Evaporation of the lakes is accompanied by westward movement of the eastern shoreline until finally no water is left. When the playa beds are exposed, they crack into blocks having an irregular hexagonal pattern. In the summer frequent wind whorls carry dust to heights of LOGO to .'5.000 above the playa surface, and more violent blows cause dust storms which obscure the landscape to elevations of 2.000 to .3,000 feet above the valley. Ea.st of the playa beds salt and alkali coatings are abundant; else- where there are none. Along the ea.stern side of these salt flats there are hunmiocky areas which appear to be wind-blown accumulations of sand and dust with deposition starting mostly around sage brush. Small, actively migrating .sand dunes are found east of this hummocky area. They do not exceed 30 feet in height, and their northeast-south- west crests with the steeper slope on the eastern side indicates predonii- nantl.v .southeast-blowing winds. On the west side of the Hays Canyon Range there is a prominent alluvial apron having a slope in the steeper parts of at least 10 degrees. Recent fault scarps break the continuit.v of the apron in a number of places. Above the alluvial .slope rises the eroded Hays Can3-on fault scarp which is steeper, more barren, and more subject to considerable rockslides than is the Warner Range across the valley. Thes? notable slumps and scars appear to be a product of the deficiency of vegeta- tion over the upper slopes of the range which receive much less snow 86 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 and rain than do the Warner Mountains. The elevation of the two ranpes is approximately tlie same and the roek formations are alike. At the ends of the "Warner Range where the elevation is less and there- fore vegetation not so prevalent, slide features are more common than in the higher part. Along the Warner Mountains across Surprise Valley there also is a considerable alluvial apron, with steep slopes (up to 10 degrees) at and near the canyon mouths but decreasing farther out until they seem almost flat. At various places in the Warner Mountains there are a number of landslide lakes which have been formed by the collapse of lava rim rocks overlying more easily weathered and eroded material. Under proper conditions where there is not too much protecting talus, the canyon walls are suflSciently exposed so that the resistant rims are undermined and masses eventually break loose, cascading into the bottom of canyons where they may form dams sufBciently durable to impound lakes for considerable periods. One example, Clear Lake, located in Mill Creek Canyon 2 miles nortlK'ast of Jess Valley in the southeastern part of the AVarner Range, is small and not over 90 feet deep. It has been formed by two slides, one from each side of the canyon a thousand feet deep. The slide scars are so fresh and the delta formed by the stream flowing into the lake is so small that the barrier probably was not formed more than 100 years ago. Blue Lake, 10 miles farther south, is similar in origin and very recent, but its waters are impounded by a single slide. Both Clear and Jess lakes drain to the Pit River. On the eastern side of the range, 7,400 feet above sea level, is Lost Lake, also in a deep canyon ; the scar of the slide which holds back its waters is much less distinct than those of the lakes previously mentioned and the delta plain formed by the stream supplying the lake is half again as large as the water surface, hence it is considerably older. Jess Valley is believed to be a filled, drained, older, and larger landslide lake in the valley of the Pit River between Clear and Blue Lakes, where the river flowing from the west base of the Warner Range cuts a gorge through another up-faulted lava bed block of lower altitude. The nearly even surface of the valley is about 6 miles long and more than 2 miles wide. The slide which dammed up the river is of enormous size. Eagle Lake, 30 miles northwest of Honey Lake and therefore south of the Warner Mountains, stands about 5,100 feet above sea level, is 12 miles long and 2 to 4 miles wide. The barrier forming it appears to be a landslide on the southeast side. The level of the lake rises and falls without regard to rainfall and when it sinks streams flow from the outer slope of the barrier and are tributary to streams entering Honey Lake. This indicates the porous nature of the dam, a feature characteristic of landslide jumbles, but it also shows that the passages through which the water emerges are alternately opened and closed. REFERENCES Baker, C. L., Physiography and structure of the western EI Paso Range and the southern Sierra Nevada : Univ. California Dept. Geol. Sci. Bull., vol. 6, pp. 117-142, 1912. Blackwelder, Eliot, Lake Manlv, an extinct Lake of Death Valley : Geog. Rev., vol. 23, pp. 464-471, 1933. Blackwelder, Eliot, Yardangs: Geol. Soc. America Bull., vol. 45, pp. 159-168, 1934. Gale, H. S., Notes on the Quaternary lakes of the Great Basin with special reference to the deposition of potash and other salines: U. S. Geol. Survey Bull., vol. 540, pp. 540, pp. 3!)9^0C, 1914. Kesseli. J. E., The origin of June, Gull, and Silver lake valleys. Mono County, California : Jour. Geology, vol. 40. pp. 726-734, 1932. Knopf, A., and Kirk, E., A geological reconnaissance of the Inyo Range and the eastern slope of the Sierra Nevada, California : U. S. Geol. Survey Prof. Paper 110, 1918. Lee, C. H., An intensive study of the water resources of part of Owens Valley, California : U. S. Geol. Survey Water-Supply Paper 294, 1913. Louderback, G. D., Period of scarp production in the Great Basin; Univ. Cali- fornia Dept. Geol. Sci. Bull., vol. 15, pp. 1-44, 1924. Louderback, G. D., Morphologic features of Basin Range displacements in the Great Basin : Univ. California Dept. Geol. Sci. Bull., vol. 16, pp. 1-42, 1920. Mayo, E. B., and others. Southern extension of the Mono Craters, California : Am. Jour. Sci., 5th ser., vol. 32, pp. 81-97, 1936. Noble, L. F.. Structural features of the Virgin Spring area. Death Valley, Cali- fornia : Geol. Soc. America Bull., vol. 52, pp. 941-1000. 1941. Putnam, W. C, Quaternary geology of the June Lake District, California : Geol. Soc. America Bull., vol. 80, pp. 1281-1302, 1949. Russell, I. C, Quaternary history of Mono Valley, California : U. S. Geol. Survey Eighth Annual Report, pp. 26-394, 1889. Russell, R. J., Landslide lakes of the northwestern Great Basin : Univ. California Publ. in Geography, vol. 2, pp. 231-254, 1927. Russell, R. J., The land forms of Surprise Valley: Univ. California Publ. in Geography, pp. 323-3.58, 1927. Russell, R. J., Basin range structure and stratigraphy of the Warner Range, northeastern California: Univ. California Dept. Geol. Sci. Bull., vol. 17, pp. 387- 496, 1928. Von Engeln, O. D., Ubehebe Craters and explosions breccias in Death Valley, California : Jour. Geology, vol. 40, pp. 726-734, 1932. MOJAVE DESERT i MOJAVE DESERT As used herein the term Mojave Desert province applies to the area in southern California which has the following boundaries : the Basin- Ranges province on the north (see pi. 2) ; the southern end of the Sierra Nevada and the Tehachapi Mountains on the northwest ; on the southwest the Sawmill and Liebre Mountains, the Sierra Pelona, and the San Gabriel Mountains ; on the south the San Bernardino Mountains and the Colorado Desert. The northern margin is difficult to determine, as the Mojave Desert merges into the Great Basin. How- ever, an approximate line has been chosen between the southern part of the Great Basin where the mountain ranges are markedly parallel and the region to the south where the ranges are lower, more deeply dissected, and lacking in conspicuous parallel arrangement. This east- west line falls between the Nopah and Kingston Ranges and runs west to El Paso Mountains north of the mining camps of Randsburg and Johannesburg (see pi. 2). The Mojave Desert is characterized by a small amount of annual precipitation and low humidity. The temperatures are moderately high in the winter and extremely high in the summer, with notable daily range. At certain times of the year strong winds blow across the region. Precipitation increases with altitude, but the increase is far from uniform, the known differences in part at least resulting from position of a locality with respect to the rain-bearing winds. Faulting has been conspicuous in the Mojave Desert province and has been the prime control of separation of high- and low-standing areas. Most notable of the fault systems is the San Andreas which lies along the north base of the San Gabriel Mountains. It shows con- spicuously from the air as an almost continuous succession of long, narrow basins separated by elevated areas which undoubtedly are small fault blocks that have risen as the basins have subsided. The last known dislocation along this section of the rift occurred in 1857. Another prominent fault system, the Garlock, is found along the southeast face of El Paso Mountains. Near the town of Garlock, it cuts a large alluvial fan ; 5 or 6 miles to the northeast, near Goler Well, there are large depressions formed by dropping of blocks of ground along the fracture zone. The scarps are so fresh that the dislocation must be rather recent. Northeast of El Paso Mountains, the Garlock fault shows along low hills on the south border of Searles Valley. East of the Slate Range, a long, narrow valley — with Leach Point Moun- tains rising steeply on the southern side and a more gentle slope on the northern — suggests the same fault, which may contintfe as far as the Avawatz Mountains. However, the faults in the Avawatz Mountains may belong to another series. Southwest of El Paso Mountains there is a marked escarpment on the southeast side of the Tehachapi Moun- tains which is in almost perfect alignment with the southetist side of El Paso Mountains, containing sag ponds and other features showing that the Garlock fault continues in that direction. The San Andreas rift and the fault along the front of El Paso and Tehachapi ranges bound a conspicuous area having the form of an arrowhead, whose point is at the western edge of the desert. This area has within it only low, scattered hills but no large mountains. South of the Garlock fault, the strikingly parallel ranges and basins so characteristic of most of the Basin-Ranges province are less appar- ent, and the arrangement in most of the Mojave Desert is much less clearly defined. However, there is abundant evidence of faulting in many places, and major landscape features have been evolved by movements along the faults, many of which seem to be rather short, but have been zones of much displacement. Areas where faulting seems to have exerted notable control in land- scape evolution are Lane Mountain and the connected hills about 15 miles north of Daggett ; the basins containing the playas known as Soda, Silver, and Silurian dry lakes, with the adjacent mountains extending from the Soda Lake Mountains north to Avawatz Mountain and the New York-Providence Mountains. Others are a series of north- westward trending, short, parallel ridges north of Bagdad and Amboy, the highest of which is Old Dad Mountains, and a more or less con- tinuous range south of the Atchison, Topeka & Santa Fe Railway, extending from near Daggett for many miles southeastward and including the Bullion and Sheep Hole Mountains. Evidence is insuflScient to determine the age of much of the faulting but some certainly is of verj' late date and some faults are still active. Because most of the Mojave Desert has not been studied geologically, the history of its landscape is imperfectly known. The Afton Basin is an enlargement of the valley of the Mojave River about 40 miles east of Barstow in the Mojave Desert. This area is one of rather even-surfaced alluvial deposits — both low sloping alluvial fans and basin sediments — above which rise isolated moun- tains of moderate elevation. The basin appears at one time to have been undrained, and this condition probably continued into middle Pleistocene time. Later the Mojave River, flowing from the San Ber- nardino Mountains, advanced into the region where its waters were impounded to form Lake Manix, named for a station on the Union Pacific Railroad. An almost completely enclosed embayment of this lake occupied the Afton Basin. Later on, probably because of erosion by its outlet, this lake was drained and the sediments deposited therein have been eroded rapidly by the Mojave River and its tributaries. (88) 90 EVOLUTION OF THE CALIFORNIA LANDSCAPE (Bull. 158 i Fig. 66. Sag ponds, basins. and bu.les (cencer, formed by Sao Andreas fault near Palmdale, Mo.ave l.eser,. P>,oto courU.y FaircHili .Unol s„r,ey.. Inc. 1952] MOJAVE DESERT 91 miia»'f^0.^ h'lQ. 67. Panorama of the Cbuckawalla Mountains, Riverside County, a fault-block range in the Mojave Desert. Photo bu C. \V. CheMterman. Field evidence shows that the basin actually contained two lakes, the earlier of which disappeared because of an intervening dry epoch. Then a third much smaller lake developed in Mojave River canyon after the draining of the earlier lake water and dissection of the sedi- ments which had been deposited in it. The first lake apparently had a fluctuating level determined by the balance between inflow and evaporation. For a time it was relatively fresh as the presence of fish remains and moUusk shells proves, but later it bciame distinctly saline as is shown by gypsum crystals in some of the sediments. Manix and Afton Basins during this interval seem to have contained all the water brought in by the Mojave River, for had the lake overtopped the divide separating them from the much lower Soda Lake basin to the east, the outlet would undoubtedly have been cut down sufiiciently to have destroyed Manix Lake. The first lake lasted sufficiently long for its waves to build large and rather conspicuous gravel bars along the northeast side of the basin. The moister interval which made possible the growth of this water body probably coincided with the earlier (Tahoe) part of the fourth glacial stage. Then the climate seems to have become more arid, the Mojave River no longer reached Afton Basin, and the lake water evaporated leaving a playa floored by clay. Some minor alterations in the playa surface were caused by erosion and deposition. Again moister climate returned, this during the later (Tiogan) part of the fourth glacial stage, and the second Lake Manix developed. The surface rose about 20 feet higher than that of the first lake, and the waves, besides making important additions to the gravel bars, cut small cliffs and terraces. The new lake overflowed eastward into Soda Lake Basin. The outlet dropped about 875 feet in 14 miles and hence was a powerfully eroding stream which not only cut a deep notch on the east side of Soda Lake Basin, but with its tributaries so extensively eroded the floor on Manix Lake Basin that only small remnants of the bottom deposits of the first lake remain as divides between the gullies. The gravel bars, being farther back from the river and more porous in composition, were less affected ; they are still almost intact for per- haps half their original length. Some time after this badland topography was evolved, a third lake appeared in the Mojave River valley, but because its surface was not more than 1.637 feet above sea level, it did not extend into Manix Basin, was much smaller than its predecessors, and also was shorter lived. The cause of the development of this lake has not been dis- covered. Since a continuous gorge had been eroded from Soda Lake Ba.sin into Manix Basin, the only reasonable explanation is that this canyon was blocked in some manner, but no evidence of such barrier remains. If the third lake was formed in the manner indicated, it had no climatic significance ; the first two. however, seem to be definitely asso- ciated with the third and fourth glacial stages. In the Mojave Desert, there are a number of places where granite and other granitoid rocks exposed in mountain blocks have been eroded to form rather smooth, dome-like areas with craggy masses of the bedrock standing above the general level and detached boulders, some of large size, scattered over the surface. The ragged appearance (if the ridges and the boulders has been developed by weathering along closely spaced joints. Such domes range from 3 to more than 8 miles across and their high points stand from 500 to 2.000 feet above adja- cent lower land. Good examples may be seen at various places along Highways 66 and 91 east of Barstow. This peculiar landscape appar- ently results from the progressive erosion of an elevated fault block in which granite forms a considerable part of the bedrock. 92 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 ^T^ Fio. 68. Tbe Moapi, vok-anic necks of rhyolite in the central part of the Turtle Mountains, eastern San Hernardino County. Photo by V. W. Chemfrmnn. 1952) MOJAVE DESERT 93 ^Jt^S^^Ji Fio. tlQ. Turtle MoutiCiiiUs near ('arsons \\>U. eastern San Bernardino County. The volcanic rocks in wtii^ . -:-< that produced the more subdued forms in the foreground. Photo by C. W. Chtstcrman. nled overlie ancient grauite 94 EVOLUTION OP THE CAHPORNIA LANDSCAPE [Bull. 158 \-t,^.;.-^' v< Kui. TO. West biUe of Rattlesnake Cuiiyuu. Au eruded fault-block mountain in the Mojave Desert. Keiirock is uninite; ragced toi.ography results frnm weath.-rinK and erosion alonj; closely spaced joints. Photo courteaj/ National Park Service. 1952] MOJAVE DESERT 95 ^"'' '*■ ''n/.''"n'?'"° TT ""^ C»Iof«.^ tiJU. ^^1^1 1^ J^ l'kUsL Fig. 78. Imperial Valley and Salfon Sea. The Salton Sea haa attained its pres<'nt size primaril.v as the result of great flows from the Colorado River in 1U05 and 11)06. Photo courtesy Southern Pacific Railroad. which crossed the Mexican border and then went back into the Salton Basin some distance away. Later, because of too rapid silting in the canal, another intake was cut on the Mexican side of the border. The flood danger from the Colorado was then not well understood and no proper preparation was made to take care of the river at high water. In the spring of 1905 several unusually high floods materially widened the break made in the river bank for the canal and these floods also carried a>vay dams built to seal off this intake. By summer time when the highest water stage is reached, too much water was being diverted toward the Imperial Valley through the canal and spilling over its banks, where it wasted and began the formation of the Salton Sea. The irrigation company, involved in financial di£5cul- ties, had placed itself under obligation to the Southern Pacific Rail- road which finally took charge of the river control. Efforts were made to dam up the intakes, but successive floods carried these structures away. Growth of the Salton Sea forced the railroad to move its main line to higher ground a dozen times and threatened to engulf all of the irrigable land of the Imperial Valley. The water sweeping into the basin eroded wide gorges into the soft alluvium, in which are the present channels of New and Alamo Rivers. After most strenuous effort and great expenditure, the Southern Pacific succeeded in closing the break in November 1906, but a flood in the following month destroyed the repairs and the work had to be 1952] COLORADO DESERT 105 i^ ,*^/0 \ iilley Kraben showing the borJprinj; > iu Lhe backeround. Photo courtety Fairchild Aenal :iut leys. 106 EVOLUTION OP THE CALIFORNIA LANDSCAPE [BuU. 158 na. The buildinE of the rorabined delta and delta plain has sh..rliMied the Gulf Ftc. 80. C-olorado River flowing over its - strongly that the ranges have been elevated along fractures. The steep south front of the Cottonwood and Eagle ranges northeast of Highway 60 70 and a prominent scarp at the south side of the Maria Mountains are examples. At the north end of the Palen Mountain east of Desert Center on Highway 60 70, there is definite e\'idence of faulting. About 16 miles north of Yuma, Arizona, a long low dam, the Im- perial, has been constructed across the Colorado River impounding a large, shallow reservoir. Great canals carry water from the reservoir, one to the California side to supply the Imperial and Coachella Valleys, the other to the southwestern corner of Arizona where there is rich land in the Gila River basin. The California canal has been constructed across the Sand Hills. The main branch gives water to the ImpfTial section ; a smaller one leads north into the Coachella Valley. The desert soils in many places yield splendid crops if water can be supplied. In this highly arid region, the Colorado River is the only sufficient supply. Used since the early part of the century, its water is now being taken in much greater quantity through this AU-American Canal system. The Colorado River forms the eastern boundary of California from slightly southeast of a small settlement in Arizona called Mojave City to the Mexican border. Most of its length in this section is bordered by mountain ranges, the largest on the California side being the Maria. McCoy, Palo Verde, and Chocolate. Depending on the distance of the.se ranges from the river, its valley ranges from 2 to 2.) miles in width. Tributaries are insignificant because of the aridity of the region. The Arroyo Seco, a dry stream channel in the northeastern part of the Imperial Valley is the largest, having a length of about 50 miles. Elsewhere the mountains are connected by alluvial divides which form enclosed basins that do not drain into the Colorado. 108 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 Throughout virtually its entire length along the California border, the Colorado Valley is terraced into two parts separated by a promi- nent bluff 50 to 100 feet hi^h. The lower terrace is that being developed by the river and covered with its sediment when overbank Hoods occur, the other represents a former level at which the river flowed. The lower terrace, which is called Palo Verde Valley, has a slight slope away from the river because of the formation of natural levees along its banks, the characteristic feature developed especially by a large stream flowing through a lowland region. The surface soil is fine textured, and is added to almost every summer by floods except where artificial levees have been constructed to contain the waters in the normal channel. Numerous old channels and oxbow lakes show the usual wandering of the river from place to place over its flood plain. The Palo Verde Valley in places is 7 to 8 miles wide, but where the mountains come close to the river, as with the Chocolate Mountains near Laguna Dam north of Yuma, it is greatly constricted in width or even absent. The higher terrace, called the Palo Verde Mesa, is a narrow almost level plain a few miles in width. In some places, the Palo Verde Mesa is broken by bluffs which divide it into a series of terraces standing at various levels. West of Blythe, for example, there is a second ter- race 30 or 40 feet higher than the first part of the mesa. The surface of the terrace in most places is sandy or gravelly, but beneath there appears to be finer sediment. However, where good exposures show in the escarpment separating the Palo Verde Mesa from the flood plain below, sand and gravel predominate. Near mountain borders, the terrace rises abruptly and grades into alluvial fans at the mouths of canyons. The surface material in such places is coarse sand, pebbles, and boulders. The escarpment separating the Palo Verde Mesa from the present flood plain of the Colorado is quite .straight and has an abrupt slope, though it has been considerably notched by sheet-flood and flash-flood erosion. On the Arizona side, the terrace bluff is modified by the Gila River which joins the Colorado near the Mexican border. The bluff along the Colorado merges with a similar one which extends up the Gila Valley for at least .50 miles. This would indicate that the escarp- ments along the two rivers are similar in age and origin,, A particularly notable feature of the blulT on the California side is that it bends westward at Pilot Knob, near the international boundary, passing south of the Sand Hills on the Mexican side, and then turns northward, merging into the old shore of Lake Cahuila which is marked by a prominent wave-cut cliff for many miles northward. There is striking similarity between the escarpment along the Colo- rado River iuiil the escarpments left by the erosion of New and Alamo Rivers as the result of the overflow into the Imperial Valley in 1905 and 1906. For many miles, the gorges cut by these two streams are about 50 feet deep and nearly a quarter of a mile wide. The bluffs along these two channels are similar to those along the Colorado. ALso there is such marked similarity between the river bluffs and the old lake shore line ea.st of Imperial Valley that it is impossible to tell where one leaves off and the other begins. The suggestion is strong that both river and lake terraces may have originated at approximately the same time, the explanation possibly being the diversion of the river into the Salton Basin and the formation of ancient Lake Cahuila. The Colorado River flows down a gently sloping delta plain, whose surface is inclined both toward the Salton Sea and the G\ilf of Lower California. The construction of this delta plain of course has been the prime factor in isolating the Salton Basin from the gulf, the delta plain having been built above sea level across the great graben to the Cocopa Mountains on its west side in Mexico. It is well known that at various times the river has discharged into the Salton Basin, which stands as much as 275 feet below sea level. The slope of the delta plain in that direction is greater than toward the gulf, hence, if the river broke through its bank discharging into the basin, its fall would be temporarily increa.sed by 275 feet, and rapid erosion would occur such as happened during the overflow in 1905 and 1906. Furthermore, the basin was then deeper than now by the amount of sediment which was deposited in Lake Cahuila. If the Salton Basin did not fill too rapidly, time might be sufficient for erosion of the Palo Verde Valley to its present depth and width below the Palo Verde Mesa. Climatic fluctu- ations which unquestionably have affected this entire region during the glacial stages al.so may have been a factor in the terrace develop- ment. There does not seem to be evidence of elevation of the region which would account for the terrace development, hence the two factors mentioned above and possibly others have been involved in their development. REFERENCES Brown, J. S., Fault features of the Salton Basin, California : Jour. Geology, vol. 30, pp. 217-226, 1922. Brown, J. S., The Salton Sea region, California : U. S. Geol. Surrey Watcr- Supply Paper 497, 1923. MODOC PLATEAU Mi MODOC PLATEAU Between the Warner Mountains and the Cascade Range far to the west is a high, semi-arid plateau which is part of the great volcanic field known as the Columbia Plateau that covers a huge area in Wash- ington, Oregon, and southern Idaho. Actually the Warner Mountains and the Hays Canyon Hange on the Nevada side were once part of this region, having been elevated into mountains by movements along great faults which broke up that section of the vast tableland in relatively recent geological time. Surprise Valley between the two ranges is a depressed block bounded by faults. To the California portion of the Columbia Plateau the name Modoc is generally given because it lies very largely within the county of that name, though it is also partly in Siskiyou, Shasta, and Lassen Counties. The elevation of the region averages about 4,500 feet above sea level, but there are many peaks and ridges projecting well above the general level. The main highway crossing the Modoc Plateau is No, 299 leading from Redding to Alturas, and part of No. 89 traverses the south- western section. A third road, which is oiled, leads from Canby on Highway 299 to Klamath Falls in southern Oregon. There also are a number of dirt roads, mostly of quite uncertain quality, but con- siderable areas are not reached by road. The geology of the Modoc country is little known, most information relating to that area con- cerns the vicinity of the Lava Beds National Monument. The most ancient features in the Modoc Plateau are hills of tuff and lava in the south, southeast, and north. The rocks are dominantly basalt whether flows or fragmental, but interlayered with them are various kinds of water-laid sediments. The hills form wide areas rising from 500 to 1,500 feet above the general plateau level, and they also are present as single prominent blocks .surrounded by younger forma- tions in Timber Mountain, Double Head, Indian Butte, and the promi- nent ridge bounding the west side of Tule Lake basin. Most of the eminences are rounded because of the great proportion of fragmental rocks composing them, and the long time during which they have been subject to weathering and erosion. In places, however, resistant rocks interlayered with the exploded debris form cliffs both above and below which are slopes, thereby evolving a terraced landscape. These volcanic and .sedimentary formations quite evidently are part of a once-exten- sive sequence which has been deeply eroded and also buried by later eruptions. After the volcanic cycle, probably not later than Miocene in age, the region was broken by faults along which there was elevation and depression of blocks. The slope of the layers in the visible rem- nants shows that the blocks were tilted to some extent in the course of the deformation. Because of the long time which has elapsed since the close of this cycle, the fault scarps have been greatly eroded and undoubtedly their bases have receded somewhat from the fault zones. The present hill fronts therefore are erosional products of land forms once prominently controlled by faulting. It is clear that this first volcanic action in the Modoc region was mainly explosive and was related to central openings about which volcanoes were constructed. The activity was interrupted on various occasions and, during the intervals of quiescence, sediments, mainly lake beds, were laid dovra. Some of these deposits were covered by subsequent outbursts belonging to the same cycle. The main part of the Modoc Plateau has been built principally in Pleistocene time, the oldest lavas of this sequence being definitely later than those of the deeply eroded Pliocene volcanoes of the adjacent Cascade Range. The youngest flows are so fresh that they cannot have been erupted more than a few centuries ago. These late volcanics are divisible into three groups, the oldest being by far the thickest and most extensive. These lavas were apparently highly liquid, forming thin, rather even surfaced flows, were erupted from fissures rather than from central openings, and flooded the region to build a plain of gently undulating surface. The second group is comprised of gen- erally much rougher surfaced flows, mostly erupted from central vents about which were constructed broad, low shield volcanoes. Explosive eruptions also occurred forming a considerable number of small cinder cones. The third group includes the most recent flows such as the Callahan on the northern edge of the Medicine Lake Highland, an eastward- projecting promontory of the Cascade Range and the Burnt Lava at the southern margin of the same area. The flow surfaces are chaotic jumbles of great blocks. Rising from their surfaces are cinder cones whose craters and outer slopes are almost perfectly preserved, testify- ing to the recency of the activity ; in fact, this suggests the definite possibility of further eruptions. Evidence given by the volcanics of the Modoc group shows that, as the cycle waned, the eruptions became more and more localized and more explosive. As the plateau was being formed by the eruption of the Modoc lavas, it was broken by numerous faults. The results of movements along the faults are conspicuously expressed in the landscape. The northern part of the region, especially around the basins of Lower Klamath, Tule, and Clear Lakes, shows a series of fault scarps trend- ing mostly northward. A few, however, are nearly at right angles to this trend. Some of the declivities are low and deeply worn, others are bold, steep cliffs ranging in height from 200 to more than 400 feet. Immediately to the west of Tule Lake basin, fresh scarps are especially well defined. Four of the more prominent ones can be traced for 6 to 12 (lU) 112 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 M 81. Spatter cone on fairly recent basalt flow in Lava Beds National Monument, Modoc County. Cones are formed where concentrations of p;is break the crust of an advancing flow and throw clots of lava around the opening. In the background is a cinder cone culled Sconchin Butte. Photo hy C. \V. Vhcstcrman. 1952 MODOC PLATEAU 113 miles north and south. Tliree of tliose scarps face eastward, one to the west. From the top of each cliff the plateau slopes sentlj" to the base of the next one. The pently inclined surfaces of the plateau blocks are quite flat and evidently do not depart far from the original surfaces of the lava flows. The fault-bounded blocks thus have rotated slightly about north-south axes. The boldness of some of the scarps indicates quite recent development. Rain and snow over the Modoc Plateau are relatively light and many of the lavas are extremely permeable, hence streams and lakes are few and are restricted to the extreme north and extreme south parts of the region, leaving the central section quite destitute of water. The chief rivers are the Pit, McCloud, Fall, and Lost. Old maps show Lost River flowing into the north end of Tule Lake, but apparentlj' the small volume of water which the river carries now is entirely used for irrigation. Tule Lake, once called Rhett Lake, had an area of about 150 square miles in 1884 ; by 1924 it had shrunk to half that size, and by 1930 was represented by a small, shallow pond which has since ceased to exist as a permanent feature. Similar recent shrinkage has taken place in Lower Klamath Lake which lies west of Tule Lake. Clear Lake in contra.st has been enlarged by construction of an irrigation dam. Lake sediments are known over considerable sections of the Modoc Plateau which evidently were covered by water in quite late time, possibly during the climax of the fourth glacial stage. Under the Modoc lavas are older lake beds indicating the presence of goodly bodies of water at still earlier times. It appears that toward the close of the epoch when the oldest vol- canic rocks in the region were erupted, probably near the end of the Miocene, north-trending faults developed along which blocks were elevated and depressed. The high areas were vigorously eroded and the debris accumulated in the intervening basins, being mostly de- posited in lakes. Later the Modoc lavas were poured out over com- paratively level sedimentarj' plains between the high blocks, eventually overwhelming some of the more deeply eroded residuals and leaving others as the oldest remnants in the existing landscape. In late time further dislocations along north-trending fractures produced the block structure of the present plateau and in the lower-standing areas the modern lakes grew. The rapid .shrinkage of the lakes in recent time is noteworthy. A small amount is the result of development of reclamation projects in adjacent southern Oregon, but most appears to have resulted from climatic change which has caused general decrease in lake size over this region and beyond. There is, however, another factor which must be considered. Tule Lake has no surface outlet, and, though the basin is nearly dry, there are no conspicuous salt deposits such as normally are left by evaporat- ing water in so arid a region. Therefore, water not vaporized must be sinking into the ground; this over a considerable period may have enlarged subterranean outlets by weathering and removal of rock, thereby increasing the loss of water. The Lava Beds National Monument takes in that part of the Modoc Plateau located near the boundary between California and Oregon, partl.v in Modoc County and partly in .Si,skiyou County. Comprising about 75 square miles, the Monument is of much historic as well as geologic interest. It was in this area that for half a century the fierce wars between the Modoc Indians and the whites went on. Under Lint- puash, known as Captain Jack, one of the last and bloodiest of the campaigns was fought. With extraordinary skill, this Indian leader and a small band, entrenched in stone forts, the remnants of which may still be seen, and in lava caves, fought a much larger force of white solders during 1872-73, until they were finally killed or captured. Mute evidence of the bitter struggle may be seen in many places about the monument today — battle scarred trees, splintered rock, bones of cattle and horses, and the stone forts which gave the beleaguered war- riors part of their shelter. Of course it was a losing fight, as eventually were all of the contests between the fewer defenders and the more numerous invaders. Bearpaw or Bearfoot Cave near the center of the Monument is about 45 miles from Klamath Falls, Oregon, and 65 miles from Alturas, county seat of Modoc County in California. The paved road from Klamath Falls to Canby on California Highway 59 between Redding and Alturas passes a few miles from the Monument 's eastern boundary, but the only roads into the area are of dirt and not too good quality, for, although they are in fair condition in places, in others there are numerous lava boulders which make traveling slow and difficult. At the south end, toward Medicine Lake Highland, the elevation is about 5,200 feet ; but this decreases northward to about 4,140 feet at an old .shore line of Tule Lake which forms the northern boundary. The lavas of the Monument, which cover also a much more con- siderable area in the Modoc Plateau, radiate from faults in the Medicine Lake Highland to the south. One of the best views of the area may be obtained from a slightly eroded cinder cone which lies just beyond the southwest corner. On one side rises Medicine Lake Moun- tain ; northward is a great fanlike flow of dark lava almost free from vegetation. The flow has a bloeky top which is extremel.v rough. Close to the cone are other little explosion volcanoes with craters in their tops; running northward from them are dark, narrow, sinuous trenches. These trenches have been formed by collapse of the roofs of principal lava tunnels and in them are the principal caves and waterholes which pla}'ed so important a part in the Indian wars. lU EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 •^i V,;r^c ^i--.^'^^'^ ■ ; >" ». \ Fig. 82. Opening of Inva tunnel in I,ava Beds National Monument. Modoc County. The opening was furnied li.v collapse of a section of the roof. rho\o hy V. 11'. Cheaterman. 1952] MODOC PLATEAU 115 Farther north are three long, eastward-facing, parallel oliflfs of mod- erate height, spaced about a mile apart. These are some of the fault scarps referred to in the foregoing description of the Modoc Plateau. At the foot of the eastern cliflF is the small remnant of the once great Tule Lake ; the cliff, an almost sheer precipice and therefore a quite recent scarp, rises about 1.000 feet; its back is smooth and slopes gently toward the base of the next cliff to the west. The most conspicuous landmarks in the area are cinder cones rising from 100 to 300 feet above the surface of the flows. The newer ones are little damaged by erosion, the older are somewhat worn ; others have been breached by flows that have poured from the vents. In all there are 11 of these little mountains, most of them lying toward the southern side of the Monument. Less conspicuous are lines of spatter cones or chimneys which mark the location of fissures from which lava quietly poured ; they were formed by small foundations of gas-rich lava thrown above the gen- eral level of the flow. In many of them are tubes extending downward for 50 feet or more, evolved by the settling of the lava column inside an already hardened wall of rock. Some tubes were developed by gas and lava spatter from holes in the roofs of advancing flows. Much of the lava has a smooth ropy surface, but some is broken into chaotic jumbles of jagged blocks. The lava caves and tunnels are found only in the ropy lava, and were formed as the roof and sides solidified leaving a cavity below through which the molten liquid continued to stream. The main tube branches so that, as the flow moved forward, little or no molten lava showed, it having been conducted through a sort of subway from the fissure to the end of the stream. Then through fractures in the sides or front of the flow, the lava escaped leaving the underground passage- ways. Because the rock jointed as it cooled and contracted, sections of the roofs fell in forming many short caves, hundreds of them being present in the Monument. In length they range from a few feet to several hundred feet and in height from 10 to 75 feet. The collapsed sections make long, narrow trenches filled with broken rock. Some of the tunnels are divided horizontally so that one lies above another, even though in the same flow. In places the roof has collapsed in such manner as to have sections forming natural bridges. Bearfoot or Bearpaw Cave in the central part of the Monument has several stories; the approach is a deep trench with almost vertical walls ; descent into it is by means of a ladder. From the roof of many of these tunnels hang lava stalactites, a testimony to the tremendous heat of the liquid stream which was able to melt solid rock. On the floors of a few caves are stalagmites formed by the drip of the molten lava from pendants in the roof. Because of the high porosity of the lava resulting from abundant joints and other openings, there are no surface streams in the Monu- ment ; all of the water goes underground. It is found as pools and as ice, for the temperature in some of these tubes is so low that water remains frozen even during the summer when it is verj' warm on the surface. In others, the ice melts during the warmer months but the cave temperatures are rarely more than 40°F., and the water is close to the freezing point all of the time. Caldwell Cave in the southeast corner of the Monument is one of the largest showing abundant winter ice which forms on the floor. In summer this is replaced by a pool of water. Crj-stal Cave, about 2 miles north of the one just mentioned, has great icicles hanging from its roof and ice stalagmites rising from the floor. During the summer the stalagmites and most of the pendants melt but some of the ice remains. REFERENCES Peacock, M. A., The Modoc lava field, north California : Geog. Review, vol. 21, pp. 259-275, 1931. Stearns, H. T.. Lava Beds National Monument, California: Geog. Soc. Phila- delphia, Vol. 26, pp. 239-253, 1928. CASCADE RANGE 1 CASCADE RANGE Extending' from the north end of the Sierra Nevada virtually to the Canadian border is the Cascade Ran^re which is especially noted for the many frreat and recently active volcanoes scattered along its entire length. In California, the southernmost conspicuous peak is Lassen which erupted explosively between 1914 and 1917. From this point to Mount Shasta, the range is not particularly well defined though it does contain some cones as large as Crater Mountains (7,418 feet) and Burney Mountain (7.871 feet). Mount Shasta is the supreme peak of the range in the state standing 14,161 feet above sea level, one of the outstanding scenic Views in North America. North of this mighty eminence, the Cascade Range is better defined, being composed of a series of giant volcanoes which stand conspicuously above Shasta Valley on the west and Butte Valley on the east. Some of the vol- canoes, such as Miller and Eagle Rock, have been considerably eroded whereas others, such as Goosenest and Whaleback. are so young that little change has been wrought in the volcanic form. These peaks rise to heights of 7.000 to 8,500 feet above sea level; the cones made of basalt have broad gentle slopes; those formed of andesite lava are distinctly steeper. During Pliocene and early Pleistocene times in the southern high Cascades of California and southern Oregon, a north-trending chain of large, gently sloping shield volcanoes was built by outpourings of highly liquid basaltic lava interrupted by a few explosive inter^-als. The chief of these are Miller Mountain, partly buried under the later lavas of Willow Creek Mountain, and the Goosenest. Ball, and Rocky Mountains. McGavin Peak, and Secret Spring Mountain. East of these along Butte Valley are several contemporaneous shields which have been much modified b.v faulting. The cones were simultaneously active and there is no positive indi- cation of the order in which they began to grow. Miller Mountain is the most deeply eroded and may be the oldest whereas flows probably of late Pleistocene age were erupted from Ball Mountain, Ikes Peak, and Eagle Rock Mountain. The craters of all of these volcanoes have been destroyed although relics of former summit cones are on some of them such as Ball Mountain. None of the shields was glaciated, as were Mount Shasta and the great peaks of the Oregon and Washington sections of the Cascade Range, but the margins have been driven back by sapping action of springs and streams which have cut easily into less resistant rocks below the Cascade lavas and therefore have caused breakdown of the margins of the shields. Most of these volcanoes are elliptical in groundplan and their orientation suggests growth over two sets of faults, one set roughly north-south and the other N30°-45°W. Kic. M. Map showing distrihution of voIcan««-s in the **a.sc!lile Kanges. After Jtotcet M'itlianig. (U9) 120 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 The eastern shields never extended much beyond their present limits, but the larjier western ones must have been much more exten- sive as remnants of their lavas extend far down the Klamath River Valley and also into Shasta Valley. Mueh later than the eruptions just described are those which have occurred since the Shasta placiers began to retreat as the last glacial stage waned. There are flows and cones, some of which are so fresh that they nni.st have been erupted within the last thousand years or so. Deer Mountain (7,007 feet), for example, consists of five lava cones built over two nearly north-south-trending faults. Four of the cones are flatfish shields of basaltic lava or lava closely approaching ba.salt in composition. The fifth cone, the summit of the mountain, is steeper. No craters are visible ; they have either been destroyed by erosion or filled with later extrusions. Each of the five cones is heavily mantled with basaltic debris blown from nearby vents and all have a thin veneer of the pumice which was blasted from Mount Shasta in 1786. Near Bulani and Yellow Butte is a considerable area of flows having a distinct hummocky surface which at the southern end is covered by patches of moraines, but farther north has on top only sediment left by subglacial streams. It is believed that these lavas were erupted from fissures near the base of Mount Shasta early in the main retreat of the glaciers on that mountain. The largest of the late volcanoes north of Mount Shasta is the Whale- back which rises 3,000 to 4,000 feet above the adjacent lowlands. The mountain is a steep cone which has been modified by erosion. At the top there are two mounds of exploded debris ; the larger, about 500 feet high, has a well-preserved crater in the top. Kegg, Soule Butte, and Ilorsethief Ranch cones are older than the Little Deer Mountain volcano. The first two have been largely destroyed by quarrying, but both evidently were composed of exploded debris. Ilorsethief Butte is made by two explosion cones whose adja- cent sides overlapped as eruptions went on. Little Deer Mountain is a cinder cone between 500 and 600 feet high breached on the south side. Surrounding it is a field of recent lava more than 10 square miles in area which seems to have been erupted during the waning stages of the volcano. Perhaps the most conspicuous peak in this part of the Cascade Range is the Goosenest, the top of which rises more than 5,000 feet above the end of its longest flow. The mountain was built on top of a much eroded shield volcano and its slopes are conspicuously steeper than other shields which are adjacent to it. The Goosenest is a large lava cone at the top of which are two cinder cones, the larger being between (iOO and 700 feet high, and having a well-preserved crater in the top. The explosive activity had almost ended before any of the visible lavas had been erupted, though buried streams may have been emitted as the outbursts were going on. Most of the lavas from the Goosenest volcano flowed to the west ; the last issued from fissures at the base of the summit cinder cone probably less than a thousand years ago. The eastern half of Shasta Valley is occupied by a great flow of basalt which has been called Pluto's Cave flow after the large lava tunnel near its southern end. This flow covers more than 50 square miles and exceeds 20 miles in length ; it seems to have come from faults close to the northeast base of Mount Shasta. Before eruption of this lava. Shasta Valley was a broad depression containing low hills of andesite .some of which still rise as islands above the later basalt. Almost certainly Shasta River and Parks Creek flowed through the valley before being diverted to their present channels by the eruption. The maximum thickness of this immense stream may be close to 500 feet near Pluto's Cave but in Little Shasta Valley it decreases to a fews tens of feet. Toward the head of the flow where it is rather narrow, there is a prominent median ridge and over it there are oval domelike eminences called schoUcndomes formed by the hydrostatic pressure of the lava under the solid crust. In the lower part of the flow there also are pressure ridges and collapse depressions. The largest of the lava tunnels is Pluto's Cave discovered in 186:? which once could be traced for a mile and a half or two miles. Now probably half a mile is as far as it can be followed, access being easy in places where the roof has collapsed. Most of the accessible part of the tunnel has a diameter of 30 to 50 feet but in places it reaches 80 feet. The floor is heavily covered by blocks which have fallen from the roof and by sand drifted in from dunes on the surface. The walls show that there are three and in places four superimposed flows with clinkery tops and bottoms, which were not separate units, but lobes extruded through the front of the advancing lava. Ova] scliollcnddmcs. a few up to 20 feet high, are scattered over the lower part of the flow and marginal pres-sure ridges, some with gaping fissures in their crests, are common along the eastern margin. Collapse depressions are scattered, but are most numerous near the margins of the lower part. Most were formed by collapse of tube roofs, but some are being produced today by normal weathering processes. In ground- plan they are elongated, circular, or irregular. Many are occupied by ponds and marshes. In the southern end of Butte Valley is a basalt flow very similar in character to the Pluto Cave stream, and similar basalts probably of the same age are extensively exposed near Bray. All seem to have come from fissures on the east side of the Cascade Range. A narrow flow of black basalt poured from a fissure located about 6,000 feet high on the east wall of Butte Canyon, traveled for about 10 miles, and ended close to Soule Ranch at an elevation of about 4,800 feet. The upper part is almost completely concealed by marshes and meadows 1952] CASCADE RANGE 121 while the lower part is buried by oiitwash of subglacial streams anil by exploded cinders. The best exposures are below Mount Shasta Woods where Hutte Creek has eroded a narrow gorfre between the eastern side of the flow and a glacial moraine. Most of the lava, which ranges from 10 to 150 feet in thickness, moved through tubes beneath a smooth, undulating crust. Another flow issued from a fissure near the top of the bold northern wall of Alder Creek canyon, cascaded down this declivity, and con- tinued for about 2 miles, ending with an abrupt front as it spread over the Butte Creek ba.salt. The surface features are so well preserved that, in spite of the forest upon it, eruptions must have occurred not much over a thousand years ago. Again within the last one or two thousand years, the Klamath River was blocked by basalt flows forming a lake 35 feet deeper than present Copco Lake at its highest level. The shore lines of this expanded lake are marked by conspicuous benches of diatomite above the present water level. Diatomite is a remarkable rock that contains myriads of the beautiful .shells of the minute single-celled plants called diatoms which live abundantly in fresh waters but more prolifically in the ocean. Because the shells are made of silica, a very hard substance, this rock if pure is quarried for use as an abrasive. The Copco activit.v began with the eruption of three cinder cones ranging from 200 to 300 feet in height ; then flows, at least nine in num- ber, issued from the base of the cones, the longest moving down the valley of the Klamath River for about 2 miles. The flow crusts are bloeky, but the lava beneath shows prominent columnar jointing. Most of the columns are vertical, but some are strongly curved like those of the Devil's Postpile in the Sierra Xevada. In part the curved columns developed where younger flows traveled along the channels in the older ones, while others resulted from the intrusion of a later flow into cracks of one already emplaced. Two recent flows have erupted from the sides of Shasta and Shastina. The older one may be seen a short distance east of Dwinnel Reservoir. Along its eastern side it has ridden over glacial moraines, but its surface is barren of glacial features, being mantled only with a thin veneer of cinders. The younger flow, probably the last from Shastina, eame from fis.sures at elevations of 9,000 to 9,500 feet and covered approximately 20 square miles. Highway 95 goes around its margin. Field evidence indicates that the Shasta glaciers had shrunk to about their present size before these lavas were erupted, one flood issuing from the end moraine of Whitney glacier only a short distance below the present front of the ice. These flows are quite perfectly preserveii, have very steep fronts, and little forest cover, all testimony of their extreme youth. From the preceding account it is evident that this remarkable area ill comparatively recent time was one of the world's great volcanic fields. The frecpient eruptions must have been magnificent spectacles comparable to those which men have witnessed at many volcanic areas round about the world. The recency of many of the lavas strongly suggests dormancy rather than extinction for parts of the area at least. Older volcanic features also are present, but are much le.ss spec- tacular. For example, six volcanic necks which once served as feeders for flows stand close to the Klamath River near Copco Dam, and there are various others in the same area. Some are found in Shasta Valley. On the eastern side of the Cascade Range and .separating it from the Klamath Mountains to the west is Shasta Valley, a roughly oval basin measuring about 30 miles north-south and 15 miles east-we.st. Most of it stands between 2,400 and 2,800 feet above sea level, hence the Cascade Range rises very conspicuously above it. The eastern half of the valley is occupied by a huge flow recently erupted from the side of Mount Shasta, while the western part consists of older vol- canics which have been eroded into a multitude of hills ranging in height from a few feet to 200 and rarely 300 feet. Most of these hills are domes or cones, but some are mesas or ridges. They look much like little cinder cones of fairly recent origin, but actually they are older lavas which have been deeply eroded. Between the hills lie small ponds and marshes and the alluvial flats of winding streams, chief of which are Shasta River and its tributary Parks Creek. In the northern half of Shasta Valley, there are few streams because of the porous char- acter of the lavas and most of the underground water empties into the ponds and meadows of the lower southern end. On the east side of the Cascade Range is Butte Valley, the bed of an ancient lake, standing approximately 4,200 feet above sea level. Meiss Lake is all that remains of a former much larger bodyof water that drained through Sam's Neck into the Klamath River. As with Shasta Valley, this depression is a large structural basin, but the faults which bound it are much younger than those margining the western basin. Several flat-floored grabenslike Sam's Neck and Pleasant Valley extend beyond the margin of the basin between elevated fault blocks. AVhen the last glaciers on Mount Shasta reached their maximum about 25.000 or more years ago, those descending its northwest slopes spread into Shasta Valley leaving end moraines along the shores of present Dwinnel Reservoir and recessional barriers .southward as far as the towni of Weed. Today these glaciers have been reduced to a length of about 2 miles and none descend below 10,000 feet. A large glacier starting at about 7.000 feet flowed down the canyons of Alder and Butte Creeks reachitig an elevation of about 4.800 feet near Soule Ranch. It overflowed the western rim of the canyon near Granada Ranch, though its thickness was only 400 or 500 feet, and crossed the opposite rim near Mount Sha.sta Woods, leaving huge lateral moraines. Beyond the ends of the glaciers much outwash was deposited by the streams flowing from them. 122 EVOLUTION OP THE CALIFORNIA LANDSCAPE I Bull. 158 iViiS-tei:; I ^r«> Butte Flb4-D«(nfl> Ciodcr Conr I Cinder Con«. , fBd»«lI>c 3*i.at4-vstca>)ef Kic. S4. !*iinririinii(' skptrh r.f Mcnnl Sli;is);i ;inil vicinity in the California section of tjie Cascadi' Uuhri^s. After Iloirel W'illintfis. Mount Shasta Mount Shasta is one of the most spectacular of a great galaxy of volcanoes scattered along the Cascade Mountains from Lassen Peak on the south to Mount Baker 500 miles northward in Washington. Shasta is an isolated mountain rising about 10,000 feet above its base and 14,161 feet above sea level. In majesty and beauty it is exceeded among the Cascade volcanoes only by the higher Mount Rainier, prime feature of the National Park of that name in Washington, but others like Hood in Oregon, Baker. St. Helens, and Glacier Peak in Wash- ington are superb structures, standing like great temples above their surroundings. How old Shasta is we cannot determine, but there are suggestions that the first eruptions began toward the close of Pliocene time. The latest products certainly are not more than a few hundred years old and a hot spring near the summit may indicate that fresh lava still exists beneath the mountain. Shasta, while not the highest of the Cascade volcanoes, probably is the largest, for it rises from surroundings about 4,500 feet above sea level while Mount Rainier is built on an elevated platform whose sur- face stands about 8.000 feet above the sea. Some hold that there has been considerable erosion from the top of Rainier, even as much as 2,000 feet of the top being gone, while the summit of Shasta probably has not been lowered more than 200 or 300 feet. Even if removal from Rainier is as great as indicated above, the Shasta cone exceeds it in bulk and height. Viewed from the east, Shasta appears to be a single mountain, but from other positions it has the form of a double cone, for a small vol- cano, Shastina, rises boldly from its western side. Shasta, like many volcanic giants similarly constructed, has rather gentle slopes near the base while its upper part becomes increasingly steep. This slope change is caused primarily by the difference in fluidity of the earlier and later lavas ; the later lavas being much more sticky when erupted than were the earlier formed shorter, thicker flows which piled up around the central vent making terraces ending in steep, high steps. Furthermore river and glacial action have added their effects, for above 8,000 feet there has been deep erosion while below 5,000 feet much deposition by streams, gravity streaming, and glaciers has aided in reducing the slope. Besides the two main cones, there is a line of small cinder cones and plug domes located along a north-south fracture traversing the summit of Shasta and a very prominent plug dome. Black Butte, which rises more than 2,500 feet above the western base of the moun- tain. Lava flows of rather late date have been erupted along the base of the volcano. The lower 5,000 feet of Shasta are mantled with thick brush, while between 5,000 and 8,000 feet there is a belt of dense pine and fir forest which gradually merges into the treeless alpine top of the mountain. This alpine section is normally clad with snow from October to June and this greatly enhances the beauty of the peak. Five valley glaciers are fed from as many valley heads in the treeless upper reaches, the largest of these ice tongues being located on the northern side of the mountain where they descend to about 9.000 feet. Although the main volcano appears to be deeply scarred by erosion, actually it has been marred very little for the deepest canyon, that of Mud Creek, cuts only 1,500 feet into it. Thus a small part of the structure of the cone is visible. That part is composed very largely of lava flows, layers of exploded fragments being relatively few. Of the latter, the most abundant exposures are in the walls of Mud Creek canyon. The last explosions of Shasta came from the summit vent and produced the Red Banks, a deposit of pumice mantling the cirque heads on the south side of the peak. The crater of the volcano lies beneath a snowfieUl about 200 yards across. At the margin of the snowfield is a small hot spring. Evidence indicates that all but the latest blocky lava flows on the northeast side of Shasta and the final deposits of pumice had been erupted when a north-south fracture broke through the summit of the volcano. No displacement of the surface shows along the fissure and little or none may have occurred, but its direction is clearly indicated by the linear arrangement of five plug domes, two cinder cones, and one lava cone. The largest dome is Gray Butte, about 4 miles south of Shasta, which rises about 1,500 feet above its surroundings; the 1952] CASCADE RANGE 123 i IG. S». Mt. Shust:i and iihaata Valiv;. . Thv LiUi lu il.t- lorii:ruuiii] are croiiej reUiuaiUs of old la\a llowS. Photo courtesy Faircftild Aerial Surreyx. 124 EVOLUTION OF THE CALIFORNIA LANDSCAPE (Bull. 158 > Fio. 8C. Mt. Shasta, a composite volcano composed of two cones. The higher cone, Shasta, is older and has been deepl.v eroded b.v streams and Rlaciers ; the lower cone, Shastina. is younger and is less eroded. Skctcheil from a photograph by It. ,V. U'AecIer. .Voiman E. A. Jlinds, (lEOMOKf'IlOI.OGY (copyright IHiS by Prenticc-llall. Inc., .Vew- York), lieprodaccd by permission of the publisher. 1952] CASCADE RANGE 125 1 Kio. 87. Mt. Shasta and Shastinn, showinR the Rreat sash in the crater and side probably caused by eiplosion. Photo courlejy L'. S. Armg Air Corps. 126 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 ^•'■.'.'■;?^v V- THE SHASTA DAM AND POWER PLANT Fig. SS. Sketch of Shnst.T Dam on the Sncramento River about 16 miles north of KeddiriK- Courtesy V. S. Itureau of Jyclamalion. 1952] CASCADE RANGE 127 length of this dome is nearly 2 miles, but the rock core beneath may not be more than half that, the remainder being the great covering of talus blocks. The cinder cones are small, the northern being only 200 feet higli and the southern 800 feet ; their summits have been smoothed and the craters destroyed by glacial action. At the south end of the fissure about 2 miles from the town of McCloud is Bear Butte, a small, steep-sided hill composed of dark lava. A view of Shasta from the west shows a broad low cone rising from its long southern slope. This appears to be a miniature shield volcano of the Hawaiian type, surmounted by remnants of a cinder cone. The lavas composing the main part of this volcano were very liquid when erupted and spread over a wide area even though the slopes they traversed were quite gentle. Most of the flows went southward, though one was partly diverted to the north and changed the course of Panther Creek, Others traveled eastward and encircled Bear Butte, the small lava cone previously described. The longest outpourings from the shield volcano descended the canyon of the Sacramento River for more than 40 miles as long, narrow tongues. The river has cut through the flows, exposing in some places gravels that lay in the bottom of the canyon when the lava invaded and in others the bedrock into which the Sacramento had cut its canyon. Excellent sections of these flows may be seen at Shasta Springs where Mossbrae Palls pours out in great volume much of the underground water coming from Mount Shasta and at other places farther down the canj'on. This water is hea\'ily charged with mineral salts. The main cone of Shasta seems to have attained its present elevation before the large minor cone. Shastina, began to form. It is possible that an east-west fissure developed about the same time as the north- south one earlier described, the two intersecting at the top of the volcano. The first eruptions along this east-west fracture built a small cone about a mile and a half west of the summit of Shasta and some- what later Shastina began at a second vent a half mile farther west. Until late in its history, Shastina was constructed from short, quite viscous flows which issued from a single vent, but the last principal eruptions came from fissures which opened on the west side of the cone. The almost perfectly preser\-ed summit crater of Shastina is a bowl-shaped depression about .300 feet deep and half a mile in diameter. Within it are two more or less conical mounds which may be plug domes with much broken tops. In the western side of the crater is a deep breach and below this lies a huge V-shaped gash; possibly both of these features resulted from violent downward directed explosions accompanying the elevation of the domes within the crater, a not uncommon feature at volcanic mountains. Later explosive eruptions occurred at lower elevations, most of them centering about 3,000 feet below the rim of the Shastina crater, though activity progressed westward so that some occurred 7,000 feet below or at an elevation of about 5,000 feet above sea level. Dark flows of blocky lava also poured from the fissures covering a considerable area ; the longest descended almost to the present site of the town of Weed on Highway 99. These recent flows cannot be more than 200 years old. Rising conspicuously near Highway 99 not far from the town of Weed is the prominent eminence known as Black Butte whose summit stands about 2,500 feet above its surroundings. From some places the Butte appears to be an almost perfectly conical mountain, but else- where this form is seen to be modified bj- a series of arcuate ridges from 200 to 1.000 feet below the top and located on the northwest side. The diameter of Black Butte is about a mile and a half. The whole of it appears to be made of great blocks of lava which become larger toward the top, only a few crags of coherent rock being visible. The common belief is that this mountain is a volcano like Cinder Cone of Lassen Park and various others, but actually it is a plug dome very heavily mantled with talus. The core may be cylindrical in form with a diameter of little less than a mile. As the mass rose, cool- ing and contracting, it was heavily fractured and the great banks of talus formed. Field e'S'idence shows that prior to the protrusion of this dome, explosive eruptions occurred, but whether a small cone was built has not been determined. Black Butte is one of the latest products of Shastan activity and its completion very likely took place in a few years, a striking contrast with the many thousands of years required for the building of Shasta. Glaciers today cover a very small area on Mount Shasta, about 3 square miles, whereas not far back in Pleistocene time ice apparently blanketed the entire peak. Of the valley glaciers, the Hotlum on the northeastern side is by far the largest, accounting for almost half the total extent of the ice. Bolam and Whitney to the west of Hotlum and Konwakiton on the south side of the mountain are the others. Hotlum glacier descends to an elevation of about 9,000 feet, the lowest point reached by any of the ice tongues ; in the early days of exploring Mount Shasta, this ice mass was thought to be about 2,500 feet thick, but now we know that actually it measures only 300 feet which is a maximum for any on the peak. Konwakiton, also known as Mud Creek glacier, has been especially conspicuous at times because of the great mud flows which have descended from it. A few tens of years ago. this glacier was about 5 miles long but since there has been considerable recession. Near its head, the slope of the ice is steep, while farther down, it flattens out, the glacier ending on the brink of a cliff in Mud Creek Canyon. During dry seasons, the run-off from melting snow, which in wetter years is more gradual and sinks into the ground, becomes torrential. Great streams find their way down the crevasses in the ice and emerge on the floor of the valley at the end of the glacier. i 128 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 The water, carr>-ing large blocks of ice broken from the snout of the glacier, races through a narrow canyon, undermining the weak walls made of tuff and breccia. At times part of the undercut eastern wall collapses into the bottom of the gorge forming temporary dams. Rather quickly sufficient water is impounded behind the barrier either to flow over it or to break through and sweep it on down the canyon. This debris-laden flood after following the canyon for about 6 miles comes out onto flatter land, spills over the banks of the stream, and spreads thick sheets of sand and mud in which are embedded great boulders. Much of the finer detritus is carried into the McCloud River, from there into the Pit, and finally into the Sacramento, at times rendering that stream turbid for 200 miles below the junction with the Pit. These great mud flows were particularly well illustrated during the dry seasons of 1924, 1926, and 1931. Below Wintun and Hotlum glaciers, other mud flows may be seen, particularly along the banks of Inconstance Creek, but much of the canyons which these tongues follow is cut in lava flows and therefore less debris is available. Evidence of the fairly late coverage of the entire volcano by ice is provided by the abundance of morainal deposits around the base. However, the glacial history is not well enough known to determine whether there were various stages, though very Likely such was the case as may be inferred from their existence farther north in the Cascade Mountains of Oregon, in the nearby Klamath Mountains, and in the Sierra Nevada. When the glaciers reached their maximum, they descended into Shasta Valley west of the peak, crossed it, and rose to a height of about 4,000 feet along the mountain slopes on the western side. On the south- west, the ice covered Quail Mountain and probably was joined by other glaciers coming eastward from the Klamath Mountains. In the principal valley on the north side of Mount Shasta, the ice was prob- ably at least 1,000 feet thick, while on the south it rose within 100 feet of the top of Red Butte as is proved by polished and striated rock. All but the highest points of Gray Butte were overwhelmed, as were the cinder cones, lava domes, shield volcano, and probably Bear Butte farther south. Especially fine glacial features are the great cirques on the south- west side of Mount Shasta and some of lesser magnitude on the east. The most perfect of the lot is that at the head of Cascade Gulch between Shasta and Shastina. There are well-preserved moraines in the cirque. Elsewhere high on the mountain good moraines are scarce except at the ends of existing glaciers, but there are some examples on the plateau southwest of Horse Camp. The road to the town of McCloud along the south base of the mountain cuts through a group of side moraines, while in the canyons of Whitney and Bolam Creeks these deposits lie beneath recent flows of blocky lava. In spite of the abundance of snow and ice on Mount Shasta, there are few large streams and these cease to flow during the winter; most of them are restricted to the north and east sides of the mountain. The cause of the scarcity of water is the porosity of the lavas and the glacial debris. The water sinks below the surface flowing underground to the base of the cone where it comes out in many good sized springs, notably on the south and southwest sides. The finest display is at Mossbrae Palls in the Sacramento Canyon. Traces of avalanches are numerous especially at elevations of about 8,000 feet where the steep upper slopes gradually flatten out toward the mouths of cirques. Frost wedging apparently dislodges large masses from the highest ridges ; in some cases they race over snow- banks increasing in volume as they go. One by the side of the trail up Mount Shasta near Horse Camp, occurring probably not more than 50 or 60 years ago, plowed a path half a mile long through tall timber. Fio. 89. Flow of basalt that descended the upper part of the Sacramento Canyon for about 40 miles from a vent on the lower, southern slope of Mt. Shasta. The Sac- ramento River has cut through the flow into much older rocks of the underlying formations. Photo by Olaf P. Jenkins. Pliocene (?) Cascade Volcanoes Between the Mount Shasta and the Medicine Lake Highland is a broad, irregular mountainous belt whose lavas appear at a few places under the volcanic rocks near the middle of the Highland. Their principal display is an arcuate outcrop around its eastern margin from which they extend westward and merge into the base of Mount Shasta. 1952 CASCADE RANG3 129 This area is composcil principally of massive, deeply eroded, j;ray isli, loose-textured lavas, most of wliieli are andesites and basalts whieh appear to have been erupted from volcanoes of the Shasta type. In fact the character of the rocks and the topo<;raphy they produce definitely relate them to that sort of volcano, hence they are co itrasted with the oldest lavas of the nearby Modoc Plateau which are darker in color and were poured out as fissure flows. The relief of the area occupied by this belt of frray lavas reaches a maximum of 6,000 feet. Haijrht Jlountain, near the western margin exceeds 8,000 feet; Garner Mountain and Horse Peak each are more than 7,000 feet. Grizzly Peak and several other conspicuous summits stand over 6,000 feet. On the other hand, the Pit River, which crosses the southern part of the area, has cut a gorge below the 2,000-foot mark into the lavas. Most of the landscape is the product of erosion, being determined by the Pit and McCloud rivers together with their tributaries. How- ever, the major forms seem to be dependent upon original peaks which had been developed during a considerable volcanic cycle. These heights are deeply eroded conical or pyramidal mountains so similar in form to Mount Shasta itself that they are far more likely the eroded products of like volcanoes than dissected remnants of a lava plateau. The lavas weather easily and have produced a thick soil which sup- ports a hea\"j' forest growth ; this results in scarcity of outcrops of fresh rock and makes study of the area a matter of much difficulty. The volcanoes from which these gray lavas were erupted are believed to have been active in Pliocene time, though the evidence is rather meager. Medicine Lake Highland About 35 miles east of Mount Shasta and somewhat to the south of the Lava Beds National Monument is the Medicine Lake Highland, a volcanic center roughly 20 miles in diameter which marks the eastern boundary of the Cascade Range in this section of California. On the north, east, and south, the highland is surrounded by the undulating surface of the Modoc Lava Plateau which in part is broken into small, fault block mountains. The highland is described as "converging upward to a roughly elliptical rampart of cones and domes," 4 by 6 miles across, on which the highest point is Mount Hoffman, 7,928 feet. This rampart enclosed an elongated basin, the western side of which is occupied by shallow Medicine liake whose surface stands about 6,500 feet above sea level. The lake has no outlet, but its water is fresh probably because of sufficient seepage into the rocks below to prevent concentration of salts brought into it by feeding streams. The basement rocks of the highland are basaltic and andesitic lavas like those of the Modoc Plateau immediately adjacent. The growth of the Medicine Lake eminence was started by eruption of rather fluid andesitic lavas which built a broad sliield volcano about 20 miles in diameter. It is believed that the central part of the shiehi later col- lapsed forming a basin or caldcra about 6 miles long and 4 miles in width. As this was going on, more viscous lava was forced up along the fractures forming rim volcanoes. Eruptions continued pouring lava into the caldcra until the cones were high enough to discharge flows down the side of the original shield volcano. As a result the fractures were .sealed, the walls of the caldera were hidden, and the basin was surrounded by the rampart of cones. Fio. 90. Panoramic sketch from the top of Medicine Mountain, showing part of the elliptical rampart enclosing Medicine Lake basin. 1, Recent lava flow between Medicine Lake and the northern ridge; 2, Mt. Hoffman; 3, Glass Mountain. After C. A. Anderson. New vents then opened giving forth sticky, lighter colored lavas of composition similar to or approaching that of granite. The floor of the summit basin is partly covered by a quite recent flow of this t>-pe. During this late cycle, more openings were developed on the lower flanks of the old shield volcano, flooding all but the western side with flows of basalt. Many small cinder cones also were formed by mild explosions. On the southeastern side of the shield, a number of cinder cones have coalesced to form a broad ridge. The Modoc Lava Beds are the northermost expression of the basaltic flows discharged from the fissures along that flank of the Medicine Lake shield volcano. ■ Recent faulting has developed small scarps and some of the recent volcanic activity has centered along these fractures forming cinder cones and lava cones. The number of small cinder cones scattered over the highland exceeds a hundred and the latest of them probably have been formed within the last 500 years. The last basalt flows are very differently distributed for none of them are present in the summit basin or the elliptical rampart sur- rounding it, AU came from vents on the northern, eastern, and south- ern sides of the shield volcano mostly located between 5,000 and 6.000 feet above sea level. Soils are poorly developed, showing the recency of the eruptions which probably ranged from culmination of the last glacial stage to the last few centuries. Flows of composition approaching that of granite are limited with exception of those of Little Glass Mountain on the west side to the 130 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 center and the rampart of Medicine Lake Highland ; some are partly glassy while others are obsidian, the latter representing some of the most recent eruptions in this area. In addition there was considerable explosive eruption of pumice. At both Glass Mountain and Little Glass Mountain, the volcanic cycle was initiated by outbursts of pumice which built up steep sided cones, while later much obsidian was erupted at both volcanoes. Pumice and obsidian also were erupted at still other centers. Lassen Volcanic National Park Very close to the soutliern end of the Cascade Mountains where they adjoin the Sierra Nevada lies a most interesting area which has been set apart as Lassen Volcanic National Park. The best approach is Highway 47 which goes from Red Bluff in the Sacramento Valley to Mineral and Chester and eventually across the Sierra Nevada. At Mineral a road turns north which gives the traveler a splendid view of Fig. 91. Cross-section illustrating the origin of Medicine Lake caltlera and rim volcanoes, a, Shield volcano made of flows of andesite lava. 6, Collapse of central block along faults. Lava was squeezed up along fractures and poured out on caldera floor. Solid black area is lava chamber, c, Continued growth of rim volcanoes dis- charging lavas down outer slopes of original shield volcano as well as into caldera. d, Cross section of present highland showing basaltic cinder cones (stippled) and basalt flows (vertical lines) on outer flanks of shield volcano. Black area in central basin is a recent lava flow. After C. A. Anderaon. the principal scenic features of the Lassen Park. Highway 47 from Redding and 37, taking off from the Redding-Alturas road (No. 299) about 5 miles east of Burney, enter the Park at Manzanita Lake on the north side. Unpaved roads lead from immediately west of Chester and reach sections of the park not accessible by the paved highway; one goes up Warner Valley into a region of hot springs, including the 1952) CASCADE RANGE 131 ,v ■ Ku;. '.<2. rain.raiu;i ..1 I.illle G;a>.- .M..uTit;.iii. Si^ki.\...u r...uii(.i . ^l...»illK twu tlaws. uf rbyolite .-.el.... ..:. .. .... ;: L in c'ntr:il p:irt of pholi.sraph. Pressure ridges that developed as flow advanced show on left side. White bill in background is a cinder cone older than the flows. Kocks surrounding flow are older basalt of the Modoc Plateau. Photo by C. W. Cheaterman. Geysers, Boiling Lake, and the Devil 's Kitchen, centered near Drakes- bad, the seeond passes along the eastern side of Harkness Volcano to Juniper Lake. Features to be seen along the principal highway through Lassen Park are many. This road leads through Mill Valley, across the ancient, much faulted crater of Brokeoff Volcano which is dotted with hot springs. Then, after passing close to the fumaroles (hot gas springs) and boiling springs of Bumpass Hell and glacial lakes Emerald and Helen, it ascends the southeast shoulder of Lassen Peak, where good views of the manj- volcanic domes, principal features of the Park, and of earlier flows from the original Lassen crater may be obtained. Following the upper part of Kings Creek Valley, the highway goes around the side of bold, talus-mantled White Mountain, and crosses the valleys of Hat and Lost creeks where the mud-flows of 1915 caused much devastation. The Lassen region for a long time has been a center of volcanic action, older lavas and explosion products showing at many places. As one phase of this activity, a great volcano was built in the southwest corner of the Park, eventually reaching a height of about 11.000 feet above sea level and a diameter of about 15 miles. Since its completion, this cone has been so much destroyed by faulting and erosion that it is appropriately known as Jlount Brokeoff. In the later history of the construction of the Brokeoff Volcano, there also occurred the building of four shield volcanoes of Hawaiian type, one situated at each corner of the Central Plateau of the Park; these are Raker and Prospect 132 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 peaks, Red Mountain and Mount Harkness. Each of these mountains is surmounted by well-preserved explosion or cinder cones which rise within the more or less nearly circular fault basins called calderas at the tops of the mountains. Fig. 93. Section across the BrokeofF Volcano showing by dashed line the approxi- mate original form. Present surface is indicated by solid line. The top of the moun- tain collapsed ulonp faults, producing caldera in the top. The Boy Scout Hills are plug domes erupted through conduits opened in the lower southern flank of the vol- cano. After Hoicel Williams. The eruption of Red Mountain had ceased when an irregular body of rhyolite was intruded into the cone at its northern base. Also after the completion of Raker Peak, a steep-sided dome of lava was pro- truded through its southern flank. About the same time, a new orifice opened on the northeast slope of the Brokeoff volcano, probably close to if not immediately beneath the present Lassen Peak. Prom this crater streams of fluid lava flowed radially though principally to the north piling up to a greatest thickness of 1,.500 feet. These flows are the black, glassy, beautifully columnar streams that completely encircle the base of Lassen Peak. Lassen Peak represents a crater filling of the volcano just described. Gas-rich lava had poured out as flows making the mountain just described. Then partly solid, partly liquid gas-poor lava rose to form the Lassen volcanic dome ; its sides were abraded as they ground against the walls of the vent and its surface broke apart into blocks which slid down the slopes forming great piles of talus. Smaller domes rose to the south of Lassen Peak forming Bumpass Mountain, Mount Helen, Eagle Peak, and Vulcan's Castle, and some of these were connected by short, thick flows of evidently sticky lava. Possibly at about the same time the domes forming Morgan and Boy Scout Ilills were forced through the southern base of the Brokeoff volcano and that of Wlaite Mountain was elevated through vents from which lavas had been poured long before. The domes that border Lost Creek may also belong to this episode. It is evident that all of the domes were rapidly constructed as compared with the much slower building of the older volcanoes from layers of lava and exploded fragments. This phase of the volcanic action was followed by the collapse of the summit of Mount Brokeoff along a series of nearly vertical faults producing a caldera having an area of about 2} square miles. Its origin is similar to tliat of the Crater Lake Basin in Oregon and many other basins in volcanic mountains. The cause of collapse may have been the large amount of withdrawal of lava from below the area in the formation of the domes above described though very likely under- ground migration of lava also played a part. Lassen Peak appears to have risen to about its present height when a vent. Crescent Crater, opened on its northeastern side and erupted flows of lava. Then, about 200 years ago, a line of cones developed at the northwest base of Lassen throwing out clouds of tuff and pumice. Two rather cylindrical domes of highly viscous lava were elevated through these cones to form the Chaos Crags. The latter and northern of the two domes had risen about 1,800 feet when steam explosions burst from its northern base causing that side to collapse and sending a great avalanche of angular blocks over about 2i square miles imme- diately adjacent forming the wilderness of boulders called Chaos Jumbles. In the northeastern part of Lassen Park is Cinder Cone, a finely preserved, very young explosion cone built perhaps about 500 A.D. Not only was the cone formed by the explosions, but the area round- about, more than 30 square miles in extent, was mantled with the 61.C Lo.P v.c. PP !•? cp KlG. tl-t. View north from Hnik.'uff .Mi.unkiiii :nruss Ihi- di)\vnf:a]lti'.i i':ildiTn to Mt. Oilier (M.D.) and Pilot Pinnacle (P.P.). Jl.L.C.. Blue Lake Canyon: I.o.l:, Loonii-! Peak ; C.C., Chaos Crags ; V.C. Vulcan's Casllc : L.l'., Las.seu Peak ; K.I'.. Eagle Peak. Dark Tongue on Lassen Peak is the 1915 lava flow. After llotcel Wiltiams. 1952] CASCADE RANGE 133 I^assen IVak. Las»en Volcanic National Park, durini; an artificial eruption, part of the cpremony of (lpept. Geol. Sci. Bull., vol. 21, pp. 51-146, 1932. Williams, Howel, Geology of the Lassen Volcanic National Park, California : fniv. California Dept. Geol. Sci. Bull., vol. 21, pp. 195-385, 1932. Williams. Howel, Mount Shasta, a Cascade volcano: Jour. Geol., vol. 40, pp. 417-429, 1932. Williams, Howel, GeoloRV of the Macdoel quadrangle, California : California Div. Mines Bull. 151, 1949. Flo. 98. ^1..;;^. L.i.^sen V of the Chaos Ju Fig. 99. Raker Peak, Lassen ^'oU■anic Xntiona is plug dome ; right siile is a lava cone capped by a ci is part of the 1915 mud flow. After Iloirel Williani 1 Park. Left s nder cone. In ide of the peak the foreground KLAMATH MOUNTAINS KLAMATH MOUNTAINS The Klamath Mountains include a rugged though not particularly high region lying west of the Cascade Mountains, south of the Oregon Coast Ranges, and north of the California Coast Ranges, being divided between the southwestern part of Oregon and the northwestern part of California. Many local names are applied to various ranges such as Siskiyou. Klamath, Marble, Scott Bar, Trinity Alps, and others, but in the ensuing description the term Klamath is applied to the entire area. Within the California section there are many magnificent scenic areas, both along the coast and within the mountains themselves. Much of the coast is boldly cliffed, the canyons are deep and narrow in most places, and the peaks and ridges rise boldly above. The higher mountains have been glaciated giving them particularly bold contours and in these areas are beautiful rock basin lakes. Fortunatelj- the Klamath country has not been so extensively penetrated by roads as have some other mountainous sections of the state so that the primitive character of the region is largely preserved. Some of the high points are Condrey Mountain (7,116 feet). Red Mountain (8,317 feet). China Mountain (8,551 feet) and Russian Peak (8,163 feet) in Siskiyou County ; Thompson Peak (8,936 feet), Caibour MounUin (8,563 feet) and Gibson Peak (8,378 feet) in Trinity County; and South YoUa BoUy (8,083 feet) in Tehama County. The principal drainage system is the Klamath River which starts east of the mountains in the Modoc Plateau and Cascade Range, even- tually flowing into the ocean about 15 miles south of Crescent City or 30 miles south of the Oregon border. At the settlement of Weitchpec between 30 and 35 miles from its mouth, the Klamath is joined by its principal tributary the Trinity, the South Fork of which flows for a long distance through a great structural depression whose origin has not yet been worked out. Some other minor streams drain west into the Pacific and some eastward into the Sacramento River which has its source in a small lake on the eastern side of the Klamath region. The Sacramento River, together with the Pit and McCloud Rivers, which flo'v through the area, are the principal drainage lines in the eastern part of the Klamath Mountains. The picture has been altered some- what by the construction of Shasta Dam located on the Sacramento River a short distance below its junction with the Pit. This giant concrete barrier, principal element in the great Central Valley Project for flood control, irrigation, and other purposes, impounds a large reservoir extending up the canyons of the Sacramento, the Pit, and the McCloud. The last two rivers now enter this large artificial lake. Geologically tUf Klamath Mountains are sharply contrasted with the bordering ranges, for they are comprised largely of pre-Paleozoic and Paleozoic sedimentary rocks, volcanic rocks, and many intrusive bodies. Along the eastern side Tria.ssic and Jurassic strata are exposed and the intrusive masses may be partly or largely Mesozoic. The Klamath formations have been greatly deformed and many of them considerably metamorphosed. In contrast, the California section of the Cascade Range is comprised largely of Cenozoic volcanics while the California Coast Ranges consist almost entirely of Mesozoic and Fig. KM). Emerald and Sii|i|>liirc I,:ikes. Trinii.v Alps. Tin- two lakes occupy rock basins excavated by a glacier. Photo by Eattman Studio. ( 139) 140 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 KiG. 101. Castlp ('ra;js, a stuck of Kninitnid rock intruded about I'M) million years iico and uncovered by erosion. Mt. Shasta is in the backsround. Photo courtesy ('. S. Army Air Corps. 1952) KLAMATH MOUNTAINS 141 Cenozoic sediments and volcanics, with the oldest Mesozoic formations belonfrinpr to the late part of the Jurassic period. The ixreat bulk of Coast Ran-ie formations are Cretaueous and Cenozoic. On the south- west side of the Klamath Mountains, the natural boundary with the Coast Ranges would appear to be the South Fork of the Trinity River, but the South Fork Ranjre on its southwest side is comprised of Klamath formations and therefore must be included in that province. The Klamath Mountains are sharply distinguished also from the Coast Ranges in the character of their drainage systems. Fold-faulting of the Klamath area probably occurred in the late Jurassic when the Sierra Nevada and various other California ranges were created. The Coast Ranges are infant mountains now in process of development by fold-faulting which started in very late Pliocene and Pleistocene time. In the Klamath region, because of erosion which has gone on since Jurassic time, control of drainage by folded and faulted features evolved when the mountains first appeared has long since been wiped out. hence the streams do not follow structural trends. In the Coast Ranges, on the other hand, folded and faulted ridges, troughs, and basins are conspicuous, and the streams to a notable extent are directed by them. The Klamath Mountains lie in the path of the moisture laden winds which sweep eastward from the Pacific. Along the coast rather equable climate prevails, though the extremes are greater than in the Coast Range belt and farther south. Precipitation along the coast is moderately heavy, averaging 39 inches annually at both Eureka and Crescent City, a few miles north. Within the mountains at Monumental (2.550 feet) there is an aston- ishing increase to 109.4 inches, but at other stations at the same or even higher elevations, the figures are much lower ranging between 28 and 52 inches with the higher figures at higher elevations. Measure- ments are made at so few places that a very incomplete picture of precipitation over the Klamath area is -available. Undoubtedly over the higher ridges particularly in the western part precipitation ap- proaches or may exceed that at Monumental. Along the eastern base of the mountains there is sharp decrease, with annual averages of 17 to 26 inches at three stations, Hornbrook, Treka, and Edgewood whose elevations range from 2.154 to 2,933 feet. At equivalent eleva- tions somewhat farther west, average annual precipitation ranges between 36 and 52 inches. Snowfall in the winter months in places is heaw reaching a measured maximum of 126 inches at Monumental and 108 inches at Gilta (3..300 feet). 60 miles to the southwest. At Yreka on the eastern border, the annual average decreases to 16 inches. The abundance of rain and snow gives many permanent streams through the region though there is material fluctuation in their volume because of the hea^•J' concentration of precipitation during the winter months. When viewed from higher peaks or ridges, the ruggedness of the region so impressive from canyon bottoms or in climbing the steep slopes in a measure departs, for most of the ridge tops have con- siderable similarity in elevation which increa.ses from the coast inland and from south to north. By imagining the canyons to be filled in. one gains the impression of a former advanced landscape characterized by broad valleys separated by ridges of moderate height. Near the coast the elevation of the ridge tops ranges from 1.700 to 2.500 feet increasing to 4..500 feet 50 miles inland ; in places, as in the South Fork, Salmon, and Yolla Bolly Mountains, the elevation increases to 6.000 or 7.000 feet. The ancient landscape evidently was warped and prob- ably faulted during elevation and has been very deeply dissected by the invigorated streams. Above the general level made by most of the ridges certain residual peaks rise for 1.000 to 5,000 feet and lower ones from 100 to 600 feet in height are common. Some of the higher areas undoubtedly represent erosion remnants but others may have reached their present position because of movements along faults. Among the highest sections in the California part of the Klamath Mountains are the Siskiyou Mountains between the Klamath and Rogue river basins, the Scott. Salmon, and Trinity Mountains which make the headward parts of divides between three large forks of the Klamath River flowing into it from the northeast. The Bullychoop Mountains in Shasta County marks the divide between the Trinit.v and the Sacramento rivers and the Yolla Bolly Mountains between the Sacramento and the streams of the California Coast Ranges. When the oldest and highest erosion surface was being developed at an elevation much lower than its remnants now possess, the streams ran transverse to the dominant structural trends of the region just as they do now. Apparently the Jurassic mountains had been sufficiently worn down so that the control of stream direction by folded and faulted ridges and depressions and other parallel structures had been largely wiped out. This surface must have been evolved by Miocene or early Pliocene time. Since then there have been various rejuvena- tions with streams returning to youth, later advancing to maturity and developing terraces below the level of the oldest landscape. Various terrace levels have been recognized, but they do not represent so continuous a landscape as that represented by the high level rem- nants. In late Pliocene and Pleistocene time, the principal uplift of the Klamath region occurred and with it the great amount of erosion which has evolved the rugged landscape of today. In the higher mountains moderate ice attack occurred during the glacial stages, both from permanent ice fields and from true glaciers. The usual cirques, U-shaped valleys, hanging valleys, rocks basins, and moraines are present, though on a relatively limited scale. The 142 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Hull. 158 f ^:,^> _ 'Wi ^-•t. ^^. ^^>. -^ ' '. ->-^*.> \ Flu. lie Klaiuutli .MouutuiiKs near \\'fa\ cr\ iUe. I'liuto by J. 11, Eastman. history and extent of the ■rlaciatioii has not been worked out, but it definitely was no match for that in the Sierra Nevada. One of the best known sections of the Klamath Mountains is the Castle Cra?s west of Duiismuir. The rafrtred spires and pinnacles have been eroded into a much jointed stock of };ray firanitoid rock which was probably intruded at the time of the Jurassic foldinpr which built the first mountains in this region. The stock has been exposed by the deep erosion which has followed the fold-faultinp; of this distant time. Another much more scenic area is the Trinity Alps, one of the highest and most rugped parts of this province, located about 15 miles north of Weaverville. The peaks and valleys in part have been moderately glaciated and conseipiently their contours are bolder than the average for the region. A number of beautiful little lakes lie high up in the deep, narrow canyons. In a number of places in the Klamath Mountains such as near Weaverville and Hyampom there are basins containing moderate thicknesses of sediments and some volcanic rocks principally of Eocene age. These deposits are notable, as Tertiary sediments are rare in the entire province. Probably the basins have been evolved by faulting which very likely occurred after the deposits were laid do^vn, protecting them from extensive erosion. At various places along the coast there are elevated shore features — battered wave-cut cliffs, erosion and deposition terraces and eminences that once were islands. One terrace has been reported at an elevation of 1,5(10 feet, another prominent one at least a mile wide in jilaccs at 1,000 feet, and a third at 500 feet. There are others less sharply defined. Unfortunately studies of the coast line in this part of <'ali- fornia go back many years and future investigations undoiditcdly will alter the picture we now have of the uplift and erosion that produced these features. Whether the highest staiuling surfaces mentioned above actually are marine terraces remains to be con- firmed; that there are some at lower elevations is certain. Prominent clitfs with the usual attendant features are now being eroded along most of the coast in the Klamath region giving a bold shore landscape which in places is magnificent. A notable man-made feature is the huge, three-pronged artificial lake impounded behind the huge Shasta dam which has been con- structed on the upper Sacramento River near the site of the former copper smelting and mining town of Kennet some 16 miles north of the city of Redding. This immense concrete barrier is 5G0 feet high and .3,500 feet long across the crest. When the water is in the reservoir the vast lake is a beautiful sight, but when it falls there is an ugl.v strip along the shore littered with sediment and dead vegetation. The reservoir is part of the giant Central Valley Project, a combined flood control, water supply, and power generating system which will be of growing importance to the Great Valley as agriculture and industry of that region develop. Oiled road access to the Klamath Mountains is limited and even dirt roads are none too numerous. Highway 101 runs along the coa.st and 299 leads from Eureka, principal city of the northern California coast, to Ivedding at the north end of the Sacramento Valley. A branch taking off at Willow Creek goes into Iloopa Valley. Highway 199 leaves 101 at Crescent City and crosses the northwest part of Cali- fornia's Klamath Jlountains on its way to Grants Pass in Oregon. An oiled road follows the Klamath River for many miles, and another also branching from Highway 99 goes to Etna. On the eastern side Highway 99 traverses the Klamath Mountains from the Oregon border to their junction with the Sacramento Valley. By bridge this highway twice crosses the immense reservoir behind Shasta Dam. REFERENCES Diller, J. S., Tfrtiar.v revolution in the topogruphy of the Pacific Coast: U. S. Geol. Surve.v Fourteenth Annual Report, 1802. Diller, J. S., TopoKraphic development of the Klamath Mountains: U. S. Geo]. Survey Bull. 196, 1902. I GREAT VALLEY GREAT VALLEY Almost completely enclosed by mountains is one of the most notable structural depressions in the world, the Great Valley of California more than 400 miles long and avera-jin*; 50 miles in width. Most of the valley lies close to sea level in elevation, but along the margins in places it rises somewhat higher, the maximum being about 1,700 feet at the tops of steep alluvial fan slopes which rest against the mountains at the southern end. Most of the eastern boundary is not much more than 500 feet high but the western is lower, ranging from 50 to 350 feet along the greater part. The basin has a single outlet, Carquinez Strait, crossing a section of the Coast Ranges through which the Sacramento River flows into San Francisco Bay. In the part of the Sacramento Valley near Carquinez Strait there is considerable land standing below sea level now protected from flooding by natural levees and artificial dikes. Bordering the Great Valley are the Tehachapi, Sierra Nevada, Cascade, Coast and Klamath Mountain Ranges. The basin has existed for a long time; record of it is found from the folding which elevated the Sierra Nevada, the Klamath, and other California mountains in the late part of Jurassic time. During the Cretaceous period and much of the Cenozoic era, the basin extended over most of the area now occupied by the Coast Ranges and had its western margin along the base of the old land, Cascadia, which has since disappeared. At times, such as in the late Jurassic and Cretaceous periods, the lowland was under water. In the land now occupied by the Coast Ranges local deformations and volcanic activity altered the topography of different sections, particularly during the Cenozoic era, and in the present valley area there were oscillations above and below sea level. Late in the Pliocene epoch the compression forming the Coa.st Ranges started and continued throughout the Pleistocene generating a fold-fault mountain system of moderate height. The elevation of this moun- tainous belt materially narrowed the width of the basin, developing the present outline of the western margin late in geological time. Into the Great Valley flowed the drainage from the surrounding mountains, most of the water coming from the Sierra Nevada, the Cascade and Klamath Mountains. These streams have deposited im- mense quantities of sediment forming a great flood plain with alluvial fans around the mountain base. Most of the streams joined two trunk rivers, the Sacramento in the north and the San Joaquin to the south. The Kings River which enters the Great Valley from the Sierra Nevada south of the San Joaquin has formed a huge alluvial fan that projects across the valley, joining one formed by a Coast Range stream, Los Gatos Creek, shutting off the part of the valley to the south as an interior basin. Formerly this section was occupied by shallow lakes, 10— 6045S ( but most of the water has been drained to increase agricultural area. The largest of the lakes was called Tulare which gave its name to the basin, though actually the area contained others as well. Sacramento Valley The term Sacramento Valley commonly is used for most of the low countrj- through which the Sacramento River flows. However, there is a considerable range of low hills north of Red Bluff developed in a broad anticline that separates the section still farther north from the much larger stretch to the south. This northern division includes a number of minor valleys which deserve separate names. The Sacramento River has its source in a small lake on Mount Eddy, one of the peaks of the Klamath Mountains, about 50 miles south of the northern boundary of California. After flowing eastward for about 12 miles, it turns to the south for 370 miles to the head of Suisun Bay, 50 miles northeast of San Francisco, where it unites with the San Joaquin River. North of Redding the Sacramento was joined by the Pit River which flows from Goose Lake on the east side of the Warner ilountains in Modoc County across the great stretch of lava beds into which it has cut a deep, narrow gorge. A few miles east of its junction with the Sacramento, the Pit received the waters of the McCloud River whieli comes from the Jlount Shasta section of the Cascade Mountains. Many other tributaries are added farther south, mostly coming from the Sierra Nevada. The main part of the Sacramento Valley is about 150 miles long. Its greatest width is about 40 miles and its elevations range from slightly below sea level to about 300 feet above in the main section. Most of the surface is quite flat and monotonous, a product of the long time during which sediment has been deposited in this great trough. In places, some folding and faulting have occurred, raising these sections above the general level and making it possible for streams to develop hilly or gently rolling topography quite sharply contrasted with the normal landscape. In the middle of the valley, quite discordant with its even contour, are the prominent Marysville or Sutter Buttes. The two principal eminences. North Butte and South Butte, are 1.863 and 2,132 feet respectively above sea level, the highest points in the entire basin. Five natural divisions are recognized in the Sacramento Valley — the red lands standing more or less conspicuously above the present flood plain which is comprised of low plains, river lands, flood basins, and islands. Red Lands. The red lands are belts of hilly or gently undulating country found in places along both sides of the Sacramento River, and generally sloping toward the axis of the valley. These areas once were almost as even surfaced as the lower parts of the valley today, having 145) 146 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 15S been constructed by the various streams coming from adjacent moun- tains and representing a flood plain and alluvial fan level higher than the present one. Later this plain was deformed by gentle folding or faulting which made it possible for the streams that built them to erode instead of deposit. In the northern part of the Sacramento Valley, the red lands extend almost to the middle of the valley and the Sacramento River flows through a wide, shallow trench bordered by discontinuous bluffs which it has eroded through them. On the east side of the river, the red lands are narrow and not sharply separated from the low plains in the vicinity of Red Bluff, but farther south their width and definiteness increase until at Vina thej' are about 4 miles wide and are separated from the low plains by bluffs about 50 feet high. In this section they are cut by streams coming from the Cascade Mountains which have eroded narrow, terraced valleys. South of Vina, the red lands are lower and disappear before reaching Chico. West of the Sacramento River, the border of the red lands is a con- spicuous bluff which extends from Red Bluff southward to Tehama, while south of that city to the Glenn County line, the boundary is poorly defined with more or less detached hills and knobs extending down to the river. Prom Chico southward to the Yuba River, the red lands occupy a considerable area on each side of the deep, terraced gorge of the Peather River. From Chico southward and from the Yuba River northward, the red lands increase from scattered higher patches sur- rounded by the low plains to wider and wider tracts of highland, until on each side of the Peather River they form broad bench lands stand- ing from 325 to 425 feet above sea level. In the region south of the Yuba River, east of the Peather River and the American basin, the red lands are only slightly elevated above the present level of the streams. They rise gradually to an elevation of 100 to 300 feet but merge into the low plains so that a definite boundary cannot be drawn between the two. On the west side of the Sacramento River, the red lands are less extensive than on the east, but are much more sharply defined, because uplift has made a sharper break between them and the low plains and because the soil in the low plain is yellowish. This color difference is not so conspicuous on the east side of the Sacramento River, as the reddisli color of the upland areas is not strongly developed. The red- dish color has been produced by oxidation of iron molecules contained in the sediment. Prom Stony Creek south to Williams, the red lands occupy small areas flanking the foothills of the Coast Ranges and rise about 100 to 200 feet above the streams flowing through them. Their much dissected surface slopes abruptly from the foothills to the low plains. Between Willows and Williams the red lands increase in width and ruggedness. The most extensive area on the west side of the Sacramento River runs from Williams southeastward to Cache Creek. The southern part is called the Hungry Hollow Hills but this terra is applied by some to the wliole area. This section is a plateau 100 to 450 feet above sea level, bounded on the northeast by a remarkably straight and uniform though somewliat eroded fault scarp. The southern part has been greatly dissected into hill-valley landscape, but farther north there are remnants of the flat-topped plateau. South of Cache Creek, but offset to the west, is another tract of red lands also apparently bounded by a fault scarp, which fringes the foothills increasing in width until near Winters it is a half mile to 2 miles across. On the north end of the narrow throat through which the San Joaquin and Sacramento Rivers find their way to Suisun Bay arc the Montezuma Hills, circular in groundplan and about 12 miles in diameter with their west side joining somewhat detached foothills of the Coast Ranges. This is a much eroded remnant of red lands sloping from elevations of 250 to 300 feet above sea level on the southwest to only 25 feet on the northeast where it merges with the surface of the low plains and of the Yolo Basin. On the south and southwest, the Montezuma Hills are bounded by sharp bluffs rising above the Sacra- mento River or above narrow plains bordering the salt marshes of Suisun Bay. River Terraces. Streams tributary to the Sacramento River have terraced valleys in the edges of the foothills and in the red lands. The terraces vary in width and height in different valleys, but in a given valley, they are constant in their relative position above the stream ; they generally are detached remnants along the valley sides. There are two principal terrace levels, the upper level being 20 to .50 feet below the general surface of the red lands, the lower 10 to 20 feet below that and 5 to 20 feet above the flood plains now in process of development. Only streams rising in the mountains and crossing the valley border have terraces. Their history indicates three stages of valley cutting, widening, and filling with sediment, the last being now in process. Causes of the evolution of the terraces include intermittent uplift with consequent limited downeutting by the streams until their down- cutting power became so small that they began to widen the valleys producing erosion terraces later covered with flood sediment. The known climatic changes of the Pleistocene also may have played a part. The history of the region is not sufl3ciently well known to determine the factors involved. Loiv Plains. The low plains lie between the red lands and the river lands, but where the red lands are absent they stretch to the ba.se of the mountains. They stand somewhat lower than the red lands and their surface is almost level. The plains have been built by the streams 1952 GREAT VALLEY 147 coming from the mountains wliich have eroded the red lands and the evenness of their surface results from sedimentation which is still goinpr on. They are the highest portion of the flood deposits being formed by the streams. The low plains are comprised partly of alluvial fan and partlj' of ordinary flood plain deposits. The fans are characteristic of the mouths of intermittent streams which have carried large quantities of debris from the mountains, depositing very rapidly as they emerge from canyon mouths. The two most notable examples are the fans of Stony and Chico Creeks, both broad and rather gently sloping. In some places closely spaced fans have coalesced into alluvial aprons as at the foot of Hungry Hollow Hills in the vicinity of Arbuckle. On the west side of the Sacramento Valley from Williams south to the Montezuma Hills, intermittent streams issuing from the hills carrying fine setliment have developed raised banks on either side which are natural levees rather than fans; they stand from 3 to 20 feet above the bottoms of the channels and range in width on each side of the channel from 500 yards to 3 miles depending on the size of the stream which has produced them. The streams forming these levees not only build up their banks but also deposit silt in their channels, thus raising their level and lowering the slope over which they flow. Bed and banks together slowly gain in elevation forming inconspicuous double crested ridges standing 10 to 25 feet above the lowland on either side. They show prin- cipally at time of flood since the lower adjacent areas are under water while the long sinuous ridges stand above. \ot infrequently flood waters burst through a levee starting a new channel with banks built up along it similar to the old, leaving abandoned channels below the point of diversion and giving a series of forking ridges. The levees along these intermittent streams are similar in character to those along the permanent rivers like the Sacramento, but are much smaller. Toward the sides of the Sacramento Valley the low plains merge into and are represented by the more actively forming flood plains of tributary rivers, which are of two types — those of permanent and those of intermittent streams. In the first group are the flood plains of the Mokelumne, the Cosumnes. and the American Rivers, which are a half mile to 2 miles wide and rise from a few feet to 20 feet above the rivers. Through the plains the rivers run with sinuous but not strongly meandering courses. Human activities have so changed conditions along the Bear and Yuba Rivers that they no longer have their original appearance. River Lands. The river lands are quite narrow belts rising 5 to 20 feet above adjacent land and extending along both sides of the two principal streams in this portion of the valley, the Sacramento and the Feather. They are natural levees which have very gentle slopes toward the flood basins or adjacent low plains, and have been built in recent time by overflow from the rivers. The levees do not stand very high above their surroundings, but their elevation is enough to make them habitable, their soil arable, and thus to separate them from the swampy and frequently submerged lands through which they run for many miles. Flood Basins. On both sides of the Sacramento River between the natural levees or river lands and the low plains are broad, shallow basins locally known as tides because of the hea^y growth of tules or rushes which they formerly supported. There are five principal basins — Butte, Colusa, Sutter, American, Yolo, and two smaller ones — Marysville and Sacramento. These areas are dry most of the year or sometimes for whole sea.sons, but, during major floods, they are inundated forming shallow lakes. Before reclamation had been undertaken along the river, about 60 percent of the valley was subject to overflow, including the basins, the river lands, and a considerable portion of the low plains. The flood basins are broad, shallow troughs filled during floods by the side streams which sweep across the low plains in broad sheets and by rivers discharging into them through definite channels, or overtopping the natural levees and the river lands. Deposition in the basins comes primarily from standing rather than from running water, hence their surfaces are almost ideally even, though there is a gentle slope toward the center and the downstream end of the basin. The soils are hea\y, less satisfactory for ordinary agriculture, but successfully used for growing of rice. Islands. At Clarksburg, minor channels break away from the Sac- ramento River, flowing for a distance, then joining other channels or the main river. These many channels therefore are interconnected and also are connected with similar channels of the San Joaquin River. Both the Sacramento and the San Joaquin enter Suisun Bay by separate courses in a gap about 4 miles wide between the Monte- zuma Hills and the Diablo section of the Coast Ranges. On account of the various channels above the river mouths part of the discharge of the Sacramento may enter Suisun Bay through the San Joaquin River and vice versa. Between the channels are islands bounded by natural levees formed by these minor branches of the Sacramento and therefore basin shaped. Tiuler natural conditions the islands were partly covered with water during much of the year and were almost completely overwhelmed dur- ing high floods. The tide raised and lowered the level of water over large areas, thus helping to scour out and keep open the minor channels. The natural levees therefore are composed of silt and loam deposited during the overflow while the central part of the islands contain peaty material formed from decaying vegetation which grew in them when covered by water. Artificial levees have been built on top of the 148 EVOLUTION OP THE CALIFORNIA LANDSCAPE I Bull. i:. Flo. lO.'i. liike alniip SiicrannMitn KiviT. WondliiiKl Ishinil in foreKroiind. Material usetl to build dike was obtained by dredging the river. Photo hy Mary Rae llill. Fig. 104. ^ '*■*', Victoria Island in Sarranionto Uiver. Asparagus fields in background. Photo by Mary lioi Ilili. natural prcventiufj tlie floodiiiji of former years. Rainwater aud spcpase from the river are drained by a oanal cut tliroufih the central flat of oaeh island leading to its lower part, and pumping stations are maintained to lift the water over the river banks. During the dry- season, water is pumped from the river for irrigation and the surplus runs to the lowest end of the island where it is pumped back into the river. Marysville or Sutter Buttes Kising Conspicuously above the almost level floor of the Sacramento Valley about ay.'miles northwest of the city of Marysville are the Marysville Buttes or as they are locally known the Sutter Buttes. Occupying an almost circular area about 10 miles in diameter, their liighest point stands 2,132 feet above sea level and almost that amount above the surrounding lowland. In any view from a distance two distinct features stand out — peripheral slopes extending in a long, gentle curve to a height of 600 or 700 feet and tlie abrupt and ragged peaks and domes making the central part of the ma.ss. With almost featureless plains extending for miles round about, the buttes make a startling landmark visible for long distances. The Marysville Buttes are a volcanic mass, principally a laccolithic intrusion which is a roughly mushroom-sbaped body of small size that deformed the covering strata into an anticlinal dome as it wits being emplaced bi>low the surface. Dtiring and after the intrtision of the igneous mass, the overlying layers were largely stripped away. Then steam explosions develoiied a central crater by blasting through the core of the laccolith and constructed a volcanic cone. Other minor volcanic eruptions also occurred. Prior to the intrusion of the laccolith, the present site of the buttes seems to have been a plain like the rest of the Sacramento Valley and I-'ic. 10.1. View of Mar.vsvillc (Sutter) Buttes from near Williams, 20 mile."* St. South Butte is high i>eak on right ; West Butte is central peak. ,l//cr llotrcl Williams. i;)52] GREAT VALLEY 149 ^^mmmm was underlain by nearly flat-lying sediments such as are being laid down in many places today by the streams which flow through the valley. The rise of the magma was forceful enough to arch the strata above it until the cover could yield no further to this type of defor- mation ; it then was broken apart by a series of faults part of which are radial to and part concentric with the margin of the laccolith. The blocks thus produced were tilted outward at various angles. The intrusive body apparently has steep sides toward the top and flattens out irregularly near the margins. The top of the body was covered by an uneven blanket of sediments; how much rock has been eroded from the blanket and intrusion is uncertain but evidence rather strongly indicates that the tops of the buttes are not far below the original surface of the body. Also how high a dome was originally produced cannot be determined because the roof was being eroded while deformation was proceeding under the impetus of the rising magma. Field evidence indicates that when the later volcanic explo- sions occurred, the sedimentary cover had been stripped off about as it is today, showing that it has only recently been denuded of the cover of volcanic debris imposed upon it. Following emplacement of the laccolith but before most of the explosive eruptions occurred, necks or stocks of rhyolitic composition were intruded both into the margin laccolith and the surrounding sediments. TVhen the sedimentary cover had been largely removed from the laccolith, violent steam explosions evolved a central crater and minor craters near the margins. \o fresh magma was erupted, the products being fragments of previously consolidated rocks erupted at relatively low temperatures. The first outbursts were vigorous, indicating long accumulation of gas pressure under the mountain, but the intensity decreased and intervals between the various explosive cycles were long enough to permit deep erosion of debris which had been pre- viously blasted out. This would indicate that magma, still being intruded at depth, was crystallizing and expelling gas which accumu- lated until the explosions began. Fio. 106. Stages in the development of Marysville (Sutter) Buttes. /, Original structure of sediments under Saeraroento Valley. 2. Intrusion of laccolith and dom- ing of sediments. 3, Erosion of the sedimentary cover and laccolith. ^, Intrusion of rbyolite domes. 5. Further intrusion of rhyolite and explosions forming volcanic cone over eroded surface of laccolith, domes, and sedimentary ring left from erosion of original cover of laccolith. 6, Production of existing topography by erosion. After Hoteel Wiiliami. Fio. 107. Generalized section across the Marysvillc (Sutter) Buttes showing by solid line the present topography, by the lower dashed line the surface of the laccolith believed to have been stripped of its sedimentary cover before the explosive cycle started, and by the upper dashed line the ijossible form of the principal cooe built by explosions. .4/(er Iloirel WilliamM. 150 EVOLUTION OP THE CALIFORNIA LANDSCAPE I Bull. 158 Before the explosive phase commenced, tlie mountain was a more or less cone-shaped eminence with high points standing about 3,000 feet above sea level. The explosions opened a roughly cylindrical vent in the central part of the laccolith which is now filled with the products of the last eruptions. The violence of the eruptions varied, for some threw out angular boulders up to 15 feet long while others emitted only fine-textured debris. The more forceful outbursts erupted great masses of coarse as well as fine fragments which apparently swept down the sides of the cones in avalanche fashion. When the eruptions were less intense, the prod- ucts were finer and formed well-bedded deposits which contrast with the chaotic nature of the avalanche debris. Also there are other deposits formed by streams which flowed down the slopes of the volcano both during the explosive phases and episodes of quiescence. The cone which was formed above the laccolith probably had an ele- vation of about 5,000 feet. Besides the major eruptions, there were many minor ones from the principal crater and from smaller openings along and near the margins of the laccolith. The explosions of the subsidiary vents doubtless built small cones. The final explosive products are fine tuffs which seem to have filled the crater of the volcano ; in some exposures they are more than 1 ,000 feet thick. From their field relations it appears that they were erupted from a long, narrow fissure located near a crescentic valley in the southwestern crater wall. For a time, the volcanic cone must have been an imposing edifice in this very flat region, but now most of it has been removed so that the resistant rock of the laccolith now makes up the principal mass of the buttes. San Joaquin Valley The larger part of the Great Valley, extending southward from the Cosumnes River and Suisun Bay is called the San Joaquin Valley, although its entire area is not drained by the San Joaquin River and its tributaries. The southern, more arid third, extending from the Kings River to the base of the Tehaehapi Mountains, has no surface outlet under normal conditions, and the surface waters accumulate in Tulare Lake and Buena Vista Reservoir. Tulare Lake formerly received a portion of the excess flow of the Kern River, but by means of a restraining dike, water is kept out except when floods break through. The original lake bottom has been converted principally to wheat-growing land. The streams draining from the Sierra Nevada bring practically all of the water reaching the San Joaquin Valley, hence their volume is many times greater than that of streams coming from the other bordering highlands and their flow is much less erratic. This strong dominance of drainage from the eastern side has given the valley an unsymmetrical form, for the axis or line of lowest elevation is much closer to the Coast Ranges than to the Sierra Nevada. In places the axis even lies along the base of the western ranges, but in other localities the western slopes may reach half the width of the eastern as between Los Gatos and Cantua creeks. The slopes of the western side are somewhat steeper than those of the eastern. This unsj-mmetrical cross section, which in most places is not char- acteristic of the Sacramento section, results from the greater aridity of climate. The streams, overloaded with sediment because of decreas- ing volume as they reach the lower, drier mountain slopes have formed conspicuous alluvial fans, the larger, of course, growing at the mouths of the eastern streams. Over the fans the streams discharge in numerous channels flowing from the apes at the mouth of the canyon in different directions down the slope. Most of these distributaries as they are called travel out- ward on the sediment of the fan into which they have cut fairly deep trenches, but some from the San Joaquin River northward have eroded into the bed rock below the fan to a depth not exceeding 100 feet, the result either of recent elevation of the Sierra block or change in stream volume, the actual cause not yet being known. Tlie west side fans, particularly near the middle and southern parts, are steep and symmetrical, features characteristic of areas of slight rainfall quite unevenly distributed where the streams are smaller and have greater fluctuations in volume. The eastern fans, on the other hand, are much larger, more gently sloping, and less clearly defined. On the eastern side the Kern River fan has gro^\Ti westward against the McKittrick Hills isolating the Buena Vista basin south of it. Originally shallow Buena Vista Lake occupied part of the basin and during unusually rainy seasons there was overflow northward into Tulare Lake. Later on dams were built changing the natural condi- tions, impounding the waters of Buena Vista reservoir. Northward, the effect of aridity has been expressed by the building of the great Kings River fan which has joined one from Los Gatos Creek flowing from the Coast Ranges forming a low ridge behind which is the Tulare basin. Part of the water from the streams south of the barrier was impounded to form Tulare Lake which, when present, was very shal- low. Because of this and the fluctuating water supply, the lake varied notably in extent from year to year. There is no evidence that overflow from Tulare Lake ever went northward into the San Joaquin drainage. North of Tulare basin, discharge from the streams is great and con- stant enough to prevent formation of .such dams and an open channel is maintained by the San Joaquin River to Suisun Bay. The trunk river meanders sluggishly through its flood plain. Along the lower course of the San Joaquin, the topographic picture in general is similar to that along the Sacramento as it is developed 1952] GREAT VALLEY 151 Fig. lOS. Meanders of the San Joaquin alone its flooi •f« I Fig. 118. Closer view of scar and earthflow jumble near tiilri>>. Vhoto by Clyde Sundeilnml, fhiklund. California. 104 EVOLUTION OF THE CALIFORNIA LANDSCAPE (Bull. 158 it has had little influence on structure or toiioH-rapliy developed by the intense mid-Pleistocene fold-faultin?. at least in the central |)art of the Coast Ranges. Valleys eroded in llie crushed rock aloii"; the San Andreas rift are aniontr the youngest land forms in the province. San Francisco Bay Region The liills and mountains lyin^ west of San Francisco Bay are divided into a northern and a southern section by the Golden Gate: to the south is San Francisco peninsula; to the north is JIarin penin- sula with its crowninjjr point. Blount Tamalpais, whose two summits West Peak (2,604 feet) and East Peak (2.586 feet) may be seen for a lonjr di.stance. North of the Golden Gate and the bay, the Coast Kanfres consist of various ridfres oriented somewhat west of north. There is little agree- ment on the names of most of these rau<;es or the area to which the better recoprnized names apply. Between lie Petaluma or Sonoma. Napa, Clear Lake, and Berryessa valleys, named from west to east ; each is a ma,jor structural depression sharply contrasted with the lesser canyons and valleys carved into the raiifres by streams. About 50 miles north of the bay. all but the Sonoma Kan^c merpe into a much dis.sected ui)land called the Mendocino Plateau which has an average elevation of 1,600 feet on the western side and 2.100 feet on the eastern where hifrher residual peaks of the Jlendocino Raufre are seen. The ni)land without question is a subdued erosion surface developed at lower elevation in past time, later raised, and now in process of destruction. Of the ma.ior structural depressions, only the Petaluma and its extension along the Russian River project as far north as the Mendocino Plateau. South of San Francisco Bay. the Santa Clara Valley, which is much larger than any on the northern side, .separates the Coast Ranges into an eastern division often called collectively the Diablo Range and a western termed the Santa Cruz Mountains. The Santa Clara Valley is the largest structural depression of the central section of the Coast Ranges, having a length of about 100 miles and a width of 15 miles where it is flooded by the .southern part of .San Francisco Bay. The lower 75 miles of this valley are drained by Coyote Creek into the bay ; whereas the upper 25 miles, isolated from the rest by a large alluvial fan, sends its waters first into Llago Creek and thence into the Pajaro River which empties into Jlonterey Bay. The Diablo Range, the mountainous belt ea.st of San Francisco Bay and south of the Sacramento River, is divided into several smaller northwest-trending ridges .separated by valleys largely controlled by prominent faidts. The highest peak in the northern part is the promi- nent Mount Diablo, ea.st of Walnut Creek, which rises :i.849 feet above sea level. South of the Livermore Valley, the Diablo Range, locally known as the Mount Hamilton Range, has a width of more than 30 miles and some jieaks exceeding 4,000 feet high. The Berkeley Hills, immediately east of San Francisco Bay, considered by some as a unit distinct from the Diablo Range, form a moderately rugged belt about 15 miles long and 10 miles wide with a prominent western-facing scarp. Between the main portion of the Berkeley Hills and the main portion of the Diablo Range lies San Ramon Valley, a structural depression. West of San Francisco Bay, the Santa Cruz Mountains exten.T,ity of California, in tlie Bcrliele) Hills. The Hayward fault system lies s at base of the hills passing under stadium. I'liolo courtesy V . S. Army Mr Corps. 1952] COAST RANGES 175 *r,^t^' m^ ¥ m \ Kiti. 127. Mount St. Helena at the corner uf Napa. Souom:i. aixi iiuuiio, 1^ (.-'■lin" i-tiUil kolcaiiio ruck. Photo by i'lyde . >.i4...jnd, Calijornia. 17G EVOLUTION OF THE CALIFOKXIA LANDSCAPE I Bull, ir V between those more resistant or into crusheil rock alon^' faults. Tlie lii-;!] points on the main ridjies are Bahl Peak (l,!):iO feet), Grizzly I'eak (1,769 feet). Koiiiul Top (1,750 feet) and Redwood Peak (1,608 feet). The Berkeley Hills block is bounded on the southwest by a zone of intense deformation in which the principal feature is the active Hay- ward fault. It is quite certain that the zone of weakness considerably antedates in ori<;in the fault just referred to, a situation comparable to that found alonp part of the San Andreas rift. It is possible that the Ilayward and San Andreas systems join southward near Hollister, thoujrh this has not been positively demonstrated. Along: the Ilayward fault there are basins and buttes similar to tliose alonp: the San Andreas rift. One particularly well developed basin contains the southernmost jrreen of the Berkeley Country Club; this may be .seen just east of Ardmore Road whidi leads from Berkeley to Richmond. Perhaps the most striking feature alon4, pp. SrilOO. I'.l.'il. Lawson, A. C, The geology of Carmelo Bay ; Univ. California Dept. Geol. Sci. Bull., vol. 1, pp. 1-59, 1893. Lawson, A. C, U. S. Gcol. Survey Geol. Atlas, San Francisco folio (no. 193), 1914. Lawson, A. C, and Palache, Charles, The Berkeley Hills, a detail of Coast Range geology : Univ. California Dept. Geol. Sci. Bull., vol. 2, pp. 348-450, 1902. Louderback, G. D., Characteristics of active faults in the central Coast Ranges of California with application to the safety of dams : Seismol. Soc. America Bull., vol. 27, pp. 1-27, 1937. Louderback, G. D., Geologic history of San Francisco Bav : California Div. Mines Bull. 154, pp. 7.5-94, 1951. ^Taliaferro, X. L.. Geologic history and structure of the central Coast Ranges of California: California Div. Mines Bull. 118, pp. 119-16:!, 1943. Weaver, C. E., Geology and mineral deposits of an area north of San Francisco ^j, California : California Div. Mines Bull. 149, 1949. TRANSVERSE RANGES TRANSVERSE RANGES Within the Transverse Ranges, an east-west system in southern Ciiliforiiia. is a structural depression extendinp eastward from the coast and reaching south of the Mexican border. The basin is the most heavily populated section of California containing such cities as Los Angeles, Long Beach, San Diego, Pasadena, San Bernardino, River- side, Redlands, and many others. It is a great agricultural region and is becoming increasingly industrialized. The Transverse Ranges con- sist of the Santa Ynez and other low mountain groups and intervening valleys such as the Ojai and that of the Ventura River and the Santa Monica Mountains farther south which extend from Los Angeles to the coast. Separated structurally but a part of the transverse system and undoubtedly once connected with it above sea level are the Channel Islands — Anacapa, which has been .set apart as a National Monument — Santa Cruz, Santa Rosa, and San Miguel, named in order from east to west. Farther east and rising very abruptly above the plains are the San Gabriel Mountains which extend as far as Cajon Pass where the San Bernardino Range, the second high member of the Transverse system starts. The southern front of the San Gabriel Mountains forms the northern boundary of San Fernando, San Gabriel, and Santa Ana valleys, all of which lie to the west of Cajon Pass. The Vottura district, about 70 miles northwest of Los Angeles, is chiefly hilly and mountainous. It is comprised of a number of sections, the highlands being the Santa Ynez Range, an east-west trending chain on the north side ; the Sulphur Mountain Upland, a discon- tinuous highland in the central part formed by Sulphur, Red, and Rincon mountains ; and the Coastal Hills, a low hilly region adjacent to the coast and extending inland parallel to the Santa Clara River east of Santa Paula. The chief lowlands are the Ojai Basin between the Santa Yn^z Mountains and the Sulphur Mountain Upland, the Ventura River Valley, and the Santa Clara Valley along the south boundary of the district. In the area is a nearly complete record of Cenozoic history of coastal southern California, for an immense thickness of deposits, about 47,000 feet, were accumulated partly when the land lay below sea level and partly when it stood above. The latest of the sediments belong to the uppermost Pleistocene, the earliest go back to the Eocene. Dur- ing the middle part of Pleistocene time, the entire mass was folded and faulted, then was beveled off with the evolution of a rather ad- vanced landscape. Still later, differential vertical uplift has invigo- rated the streams, developing the present erosion c.vcle. The older landscape, best preserved on the summit of Sulphur Mountain, is called the Sulphur Mountain erosion surface. It was characterized by broad valleys with hills and low mountains rising above. Because in nio.st places later erosion has destroyed this land- scape, its character has to be inferred from such remnants as are left. Part of the present drainage pattern of the district is inherited from the Sulphur Mountain cycle, but part is recently initiated. Most of the recent changes have been accomplished by licadward erosion and by diversion or capture of east-west streams by .soutliward flowing streams. As a result, a few large through-flowing streams have courses roughly at right angles to the fold and fault trends of the area. This east-west range rises about fi.OOO feet, making a prominent barrier along the north side of the Ventura di.strict. The streams of the southern part of this range are tributary to the Ventura River or to Santa Paula Creek. They flow down steep grades and have incised deep, narrow gorges into the mountain flanks. Since these principal tributaries flow nearly at right angles to the trend of the folds and faults, minor branches have excavated valleys into the weaker beds and hence parallel the structural trends. These lesser streams, having reached maturity, broadened their valleys and developed an almost continuous lowland paralleling the front of the Santa Ynez Mountains. This lowland, eroded in shale between two resistant sandstone ridges, shows mo.st prominently north of Ojai Valley and west of the Ventura River in Kennedy Canyon. The Ojai lowland is divisible into three parts, the Santa Ana Valle.v or western section, Long Valley in the center, and the eastern part which does not have a name. Tlie Santa Ana Valley is principally a bedrock surface covered with thin residual soil, while in Long Valley, this bedrock is covered by river terraces. The eastern part of the Ojai lowland is filled with alluvium and at the eastern end are the two large alluvial fans of Sennor and Horn Canyons. In the Santa Ana section, the two principal streams are Santa Ana and Coyote Creeks. The Santa Ana may have been inherited from the Sulphur Mountain erosion cycle, but its present valley was started during the period of uplift initiating the late erosion cycle during which the Sulphur Mountain surface has been largely cut to pieces. In an epoch of relative stability in the later cycle, the stream broadened its valley by the erosion of a wide terrace and then incised a narrow arroyo 50 feet deep below the terrace in consequence of a very recent uplift invigorating the power of the stream. Coyote Creek was established later than Santa Ana Creek by head- ward erosion and diversion of east-flowing tributaries of the Santa Ana drainage. East of Santa Ana Creek, the history of the valley is uncertain. The valley is divided into two nearly equal sections by a low ridge crossed both by Santa Ana and Coyote Creeks. The two halves of the valley ( 185) 186 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 in the area east of the Santa Ana Creek may have been excavated by tributaries of the Ventura River when it flowed at a considerably higher level than at present. The upper Ojai Valley is a small, lens-shaped basin about 5 miles long and 1 mile wide, ranging in altitude from 1,250 feet at the west to 1,550 feet at the ca.st and separated from the main part of Ojai Valley by a ridge 50 to 150 feet high at the southern end and 300 to 500 feet high farther north. Westward the same ridge rises to 1,035 feet at Lion Mountain. The difference in elevation between the two parts of Ojai Valley probably results from erosion by San Antonio Creek along the eastern part of the Santa Ana fault which crosses the northern base of the dividing ridge. Because the south side of the fault has moved upward bringing resistant and less resistant rocks in contact, erosion has been slower on the southern, more resistant side, which now stands higher. This nearly continuous ridge, convex to the south, runs through the center of the Ventura district and is breached by only two streams, the Ventura River and Santa Paula Creek. It consists of Sulphur Mountain east of the Ventura River and Red and Rincon mountains to the west. The conspicuous feature of Sulphur Mountain is the sharp contrast between the advanced mature landscape of the summit, the elevated erosion surface of earlier time, and the bold southern face. Some have interpreted this declivity as a fault scarp, but actually it has been evolved by rapid stream removal of easily eroded shale. Red Mountain, west of the Ventura River, is an elongate dome. In the weak rocks exposed during erosion of the dome, valleys have been evolved parallel to the structure and are separated by ridges of more resistant strata. These valleys are tributary to the drainage flow- ing down the slopes of the dome. Such a circular or elliptical valley and ridge pattern is often called race-track or annular topography. On the summit of Red Mountain are numerous undrained depres- sions formed by movement of masses of sandstone down the slope. The hollows range from 100 to 400 feet long and 20 to 60 feet deep. Many contain permanent ponds while others are partly filled or converted to grassy flats. Most of the undrained hollows are at the east end of the mountain north of a large, now inactive slide at the head of Canada del Diablo. A large slide in Padre Juan Canyon has projected the amphitheater-shaped head of this valley through the original crest, so that its stream is now attacking the north side of the mountain where it has beheaded several northward flowing streams. As is common, the slide blocks have rotated backward as they have moved, and the undrained depressions lie between the rotated blocks and the scar left on the hillside as the masses broke away. Rincon Mountain resembles Sulphur Mountain in its general topo- graphic form and much of its geology. The crest is a rounded ridge falling off abruptly to the north and south, but rising gradually east- ward to the domelike summit overlooking Los Sauces Creek. This rounded crest is a remnant of the Sulphur Mountain erosion surface and is the most prominent feature in the coastal area, standing 2.165 feet above sea level. On the south side of Rincon Mountain are 9 levels of marine terraces, the highest being between 1.250 and 1,300 feet above sea level. The terraces have been warped in process of elevation and increase in altitude ea.stward. All of the terrace surfaces are buried by later detritus which obscures a thin layer of older fossiliferous marine sand and gravel overlying wave-cut platform. The Coastal Hills include the area between Sulphur Mountain and the Santa Clara Valley and inland from the coast to the eastern boundary of the region. The hills range in elevation from 1.000 to 1.950 feet. Tlie Sulphur Mountain erosion surface undoubtedly extended across this section, but has been almost completely destroyed, being replaced by a hill and valley topography. Landslides are abundant and even more so are masses of debris called earthflows that were water-logged when they started to slide. The landslides have moved down favorable surfaces of resistant strata while earthflows have occurred generally throughout the hilly belt. The Ventura River flows from the Santa Ynez Mountains for 12 miles before entering the Pacific Ocean a mile west of the city of Ventura. It has a narrow flood plain in no place reaching a mile in width and in few places more than half a mile. In the lower part of its course the river meanders slightly, but in most places has an anastomosing channel, especially north of Ojai Valley. The last 2 miles of the valley seem to be underlain by deep alluvium, indicating that there was excavation in this section probably when the sea stood lower during the glacial stages of Pleistocene time. Along the Ventura River are terraces which provide important information regarding the extent and nature of deformation since erosion of the Sulphur Mountain surface. The highest terrace stands at 1,180 feet on the west end of Sulphur Mountain where it merges with the Sulphur Mountain erosion surface, indicating that the Ven- tura River had evolved before the late Pleistocene uplift while the erosion of Sulphur Mountain surface was going on. The river prob- ably established its course by headward growth and capture of an earlier drainage system, much as Santa Paula Creek has done in divert- ing west-flowing drainage of the upper Ojai Valley. Deepening of the Ventura Valley kept pace with uplift, going on most actively when elevation was most vigorous. Then during episodes of greater stability, the valley widened out by the development of a lower terrace. This process has been repeated giving a succession of 1952] TRANSVERSE RANGES 187 terraces. As the deformation progressed, the terraces were bent into a broad arch which reached its maximum elevation at the Red Moun- tain fault. Marine Terraces At the base of the modern sea cliffs along the coast, there is a low wave-cut platform. Elevated terraces are restricted to two sections, I lie fii-st extending from Pitas Point 7 miles west to the Carpinteria Plain and the second from Ventura east to the Santa Clara River. West of Pitas Point, terraces are prominent and best developed on Hincon Mountain where they have been recognized as high as 1,300 feet above sea level. Elsewhere their number and altitude are difficult to ascertain. Near Rincon Mountain the terraces have been tilted so that they slope toward the Carpinteria Plain ; almost all of them have I'lTii t-ut by faults wl'.icli prcdrce small offsets in their surfaces, these reaching a maximum of about 30 feet. Fig. 132. Wave-cut terraces covered by veneer of marine deposits and then buried or partially buried by nonmarine cover of .sediment after elevation of the terraces. A, Nonmarine cover concealing cliff between successive terraces. B, Non- marine cover over terraces but not concealine cliff between them. After U. S. Oeolog- icat Survey. Behind Ventura, marine terraces have been eroded but are difficult to recognize because the bedrock and the terrace gravels are quite similar. Terrace form is best preserved on the lower ones and virtually disappears above 500 feet ; evidence for their presence above this elevation is principally gravel remnants which may or may not be correctly identified as having been formed on a wave-cut surface. The best preserved terraces near Ventura are on the ridge immediately east of the Ventura flood plain. Practically the entire business district of Ventura is built on the lowest one which stands 15 to 20 feet above the ocean and measures about 2,100 feet wide. Eight feet above sea level there is a second conspicuous bench at the east margin of the Ventura River Valley, but farther east this and the lower one are largely buried by an alluvial fan which has formed at the mouth of the first canyon west of Hall Canyon. At 350 or 400 feet above .sea level is ihe flattened ridge, also a marine terrace, on which stands the Serra Cross. Between this and a lower terrace at 200 feet, conspicuously shown near a large excavation behind the Ventura County Courthouse, are four minor ones indicating that the emergence of the land was broken by intervals of relative stability, some longer, as that when the main terraces were cut, and others shorter, such as those responsible for the lesser notches. As the land was elevated, there was some fracturing with displacements of a few feet showing in some of the terraces. The evolution of the present shore line has been controlled by the direction of prevailing winds and currents and by inequalities in the resistance of rocks under attack by the waves. The unsymmetrical major headlands have a long northern side and are separated by short northeast-trending embayments. The sea breezes are generally strong- est in the summer when the Santa Clara and Ventura valleys connect highly heated inland with the coast. Ocean currents flow eastward as a result ; the waves associated with them parallel the longer stretches of the beach and approach the shorter side of each headland obliquely, the angle between the headland shore and wave front being between 20 and 30 degrees. Active erosion goes on along those parts of the shore attacked by this oblique wave approach. Between Rincon Point and the Ventura River, the beach is a thin veneer of sand with bedrock cropping out for considerable distances. The widest beach is at Picrpont Bay southeast of the Ventura River, a shallow embai,Tnent between the Ventura and Santa Clara Rivers supplied with sand principally by the Ventura River. The beach is not being built outward, the shoreline in places standing as much as 2,500 feet from the base of the seadiffs, a result of the northward migration of the Santa Clara River over its flood and delta plain. The last event in the history of this section of the coast has been slight emergence, shown by a wave-cut terrace exposed along the highway north of Pitas Point, where it stands 15 to 16 feet above sea level ; this increases to 21 feet a mile and a half southeast of Seadiff station showing that tilting has occurred during emergence. Projec- tion of the terrace landward beneath the cover of non-marine debris deposited on it indicates an elevation of about 45 feet at the base of the former sea cliffs which are 115 to 120 feet high. The terrace rem- nant is about 300 feet across at Pitas Point but increases to 1,200 feet at Seacliff station. 188 EVOLUTION OF THE CALIFORNIA LANDSCAPE r [Bull. 158 1 Flo. 133. The San Oaliriel Mountains near San Diuias. I'hoto by Spence Air Photos. 1952] TRANSVERSE RANGES 189 The San Oahriel and San Bernardino Mountains are of about equal size and form an imposinfr barrier extending many miles north and east of Pasadena and Glendale. Both ranges are composed of a series of faulted blocks thrust upward from a region of rather low relief and elevated to their present height during Pleistocene time. The southern front of the San Gabriel Range is a bold, considerably dissected slope marked by a complex sj^stem of faults whose base forms a sharp but irregular line separating the low alluvial plain to the south from the mountain block. West of San Antonio Canyon near Clare- mont and south of east-west Tujunga and San Gabriel Canyons, the summits of the range are from 3.000 to 6.000 feet in elevation, while north of this area, they rise to 8.000 and 10,000 feet, the highest point being Mount San Antonio or Old Baldy (10.080 feet). The ridges of this portion of the Transverse Ranges are sharp and the canyons deep, hence there are few remnants of the advanced landscape which was elevated as this fault block rose. Like the San Gabriel, the San Bernardino Mountains are about 60 miles long in an east-west direction; they widen from a point at the summit of Cajon Pass (elevation 4,250 feet) to nearly 30 miles at their eastern end. The crest line of the western section is remarkably even and forms the drainage divide between the Mojave desert, which is part of the Basin-and-Range Pro\-ince, and the coast. The crest begins near the summit of Cajon Pass at an elevation of about 5,000 feet and rises gradually for about 25 miles to the southeast where it reaches 7.500 feet above sea level. Then it is broken by Bear Creek Canyon. Beyond this narrow gorge, which is more than 3,000 feet deep, the crest again rises for more than 12 miles to 9.500 feet, but is no longer the drainage divide ; it culminates in Sugarloaf Mountain, 9,500 feet high. Southeast of the Santa Ana River into which Bear Creek empties, the range is most rugged and reaches its highest elevation, with San Gorgonio Peak, 11,485 feet above sea level, as its supreme summit. In the vicinity of San Bernardino, the south front of the San Ber- nardino Mountains is a steep, battered fault scarp that faces the Santa Ana valley and makes a clearly defined straight boundary with this alluvial plain. The summit region to the north of the crestline referred to above is a gently rolling plateau whose high points do not rise more than 1,500 feet above the bottoms of the valleys between them. The plateau is a remnant of the same advanced erosion surface that is much more damaged by later erosion in the San Gabriel Mountains. Prior to the uplift of these blocks, this flat surface seems to have occupied a large part of southern California, though its limits cannot be determined because of the great amount of later deformation. The features of this older topography in the San Bernardino Mountains are sharply con- trasted with the much more rugged topography developed as the range has been rising. This new landscape consists of deep narrow canyons which are eating headward into the plateau and gradually destroying it. Between the recently cut gorges are sharp crested, narrow ridges. The western part of the plateau drains into the Mojave River and the eastern part into the Santa Ana River. There appear to be two principal fracture belts on the southern side of the San Gabriel section along which this mass has risen, one lying at the foot of the range and the other somewhat farther back within it. The fault system along the front of the mountains is called the Sierra Madre ; the total displacement which has occurred along this fracture zone is probably about 5,000 feet, judging by the position of the bed- rock floor at the base of the range and the elevation at the top of the scarp. East of Dalton Canyon, this fault zone diverges from the range front and runs along the base of foothills south of the main scarp ; this section is called the Cucamonga fault, along which displacement ranges from a few feet to 1,000 feet west of San Antonio Canyon. The fault zone within the range is called the San Gabriel ; north of it. the range rises in elevation nearly 3.000 feet, a change that may be due to movements along the fault. Other fractures that have caused less displacement include the San Andreas, which cuts the San Gabriel Range near its northeast margin, and has moved horizontally. Most of the southwest margin of the San Bernardino Mountains is bounded by the great San Andreas fault, the major fracture system in California. The several faults that diverge from the San Andreas zone, swinging eastward into the range, are probably responsible for most of the uplift along the south and west sides. The western San Bernardino Mountains appear to be a succession of fault blocks, each tilted to the north. North of the San Andreas zone, five important faults run eastward into the range and appear to have been the zones along which the southwestern part of the mass has been elevated. The cumulative effect of the uplift which has taken place along the ea.st-west faults in the San Bernardino Mountains is partly offset by the tilting of the blocks northward as they have risen. However, the old erosion surface, represented by the even crest line, is 5.000 to 7,000 feet above the bedrock south of the San Andreas fault where the same surface shows. The Santa Monica Mountains that start about 5 miles northwest of the City of Los Angeles and the four Santa Barbara Islands — Anacapa, Santa Cruz. Santa Rosa, and San Miguel — in the not very distant past were a continuous chain. The islands which are smaller units have been isolated by erustal movements while the main mass, the Santa Monica Mountains, is locked to the land by the Ventura Basin which EVOLUTION OF TUB CALIFORNIA LANDSCAPE [Bull. 158 •^i'W- w<^''J %W- ■■/■■■'■■ wV-i' . ^^ v> f--t - --■ --" Fio. 1S4. ^ ■ ■ ^^'*^ '™~*' *' ■ „ barrenness of the slopes „llows speedy rnnoff of heavy rains and conse- Oeep. narrow canyons "o-U . .,.e_Sa„ Ua.r.;^— ...s^^^ ,. ,. ,,„„ ,, .„.,,. 1952] TRANSVERSE RANGES 191 Kni. l-'t.*. San GorKOiiio Penk, hijcli puint i 11.4.Vi f.-t-t i m tUv San Bernardino Range, a member of the Transverse prou|). Uivers have cut deep canyons into the ranfje. pxteasively deMroying an erosion surface of relatively gentle relief which extended across the mountain block prior to its uplift. Photo by Fairchild Aerial Surveys. 192 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 Fio. 136. Santa Monica Mountains (background), the slightly dissected Santa Monica alluvial plain (foreground), and sea cliflfs now being cut into the plain (left foreground) . Photo by S pence Air Photos. 1952] TRANSVERSE RANGES 193 abuts against them on the northern side. Several kinds of evidence, partii-ularly elephant remains in Pleistocene rocks on the Santa Bar- bara Islands comparable with types found in rocks of the same ajre on the mainland, indicate stronply that the chain was formerly con- nected. The islands, an east-trending group, are now separated by deep submarine troughs, a plan characteristic of the rather broad continental shelf off.-ihore from the Los Angeles Basin. Studies sug- gest that the varied contour of the .shelf in this section, which con- trasts with the normal rather smooth seaward slope, has resulted from faulting which developed a number of small, nearly rectangular blocks which have moved upward and downward, giving a rather hetero- geneous arrangement of islands, submarine basins, and higher stand- ing underwater areas. This faulting is assigned to the late part of Pleistocene time. The Santa ilonica Range is about 45 miles long, has an average width of 10 to 15 miles, and rises from 1.000 to .3.000 feet above sea level, the higher parts being in the western section. The western 30 miles front on the Pacific Ocean, where strong wave erosion has developed a prominent sea cliff 175 to "200 feet high. Highway 101 runs along the base of this cliff and Highway 27 crosses the mountains from Topanga Beach west of Santa Jlonica. The eastern part of the Santa Monica Mountains has quite sub- dued contours, making them a hilly rather than a mountainous belt. The crests of the hills rise 1.300 to 2.100 feet above sea level or 800 to 1,.')00 feet above the adjacent plains. There is some increase in eleva- tion westward. The crest of the mountains is a series of flat-toppeil ridges of about the same elevation. The Hat tops appear to be remnants of an old erosion surface which transgressed the iliocene strata of the earlier Santa Monica anticline. This advanced landscape, probably belonging to old age of the erosion cycle, seems to have been developed in the earlier part of Pleistocene time after a vigorous deformation in the later part of the Pliocene epoch. During the later part of the Pleistocene, the surface has been brought to its present elevation and has been materially dis.sected by streams. Some of the streams, like those in Topanga and other major .south- ward directetl canyons, are fed by springs and therefore permanent : the rest flow only during the heavier rains. The Los Angeles River, major stream of the area, flows from the Simi Hills and Santa Susana Mountains across the San Fernando Valley and around the eastern end of the Santa Monica Mountains. Generally drj-, the drainage sys- tem often carries wild torrents during heavy rains. The main drainage divide of the Santa Monica Mountains lies near the northern side and not in the central part as might be expected. This very likely results from the higher elevation of the plain to the north against the base of the mountains and the longer distance which the streams must flow to reach their lowest level of erosion. Although the Santa Monica Mountains, particularly the ea.stern part, are relatively subdued in contour and remarkably uniform in eleva- tion over considerable areas, yet there are some higher and more abrupt topographic features which appear to have been cau.sed by late faulting. The Vicente Mountain area west of upper .Sepulvetia Canyon and a wedge-shaped, fault-boundeil granite mass west of upper Laurel Canyon are examples. It also seems probable that the steep granite front of the mountains north and west of Hollywof5-/;'/////|- se« LEVEL r-r^XV'V //// -500 _ <.^>^ — ^^■^>S:^_'>/'////////-iOOO b I 2 3 4 S S 7 S 9 10 II 12 13 14 15 16 17 IS 19 MILES Fig. 139. Diacrammatic section across Ibp Santa Fe Springs-Co.vote and Beverly-Newport uplifts. The Quaternary alluvium is very late Pleistocene, .l/fcr ifo/lin Eckit. vation of the Peninsular Range. Examples of these little damaged remnants may be seen south of Alpine at 2,000 feet, south and south- west of Guatay Mountain at 4.000 feet, and the rather large area of the McCains Plateau between Jacumba and La Posta valleys also at about 4,000 feet. Below this advanced erosion .surface lies deep residual soil and weathered but still coherent rock through which project masses of much fresher material. The old landscape had been evolved by long erosion prior to eleva- tion of the range. It seems to be similar in its topography and may once liave been continuous with that in the uplands of tlie San Ber- nardino and San Gabriel Mountain:?, and in many remnants scattered through the Mojave Desert. This Furface has not been studied in much detail hence its history is not well knowni. Whether it exhibits the multiple features so tinely showii on the western side of the Sierra Nevada has not been determined, but such evidences of recurrent uplift and associated dissection are to be expected. Ill the Peninsular Range there is a considerable number of basins; one of the largest is the Valle San Jose between Palomar, Volcan, and Agua Calieiite mountains whose crests rise from 2,500 to 3,500 feet above a flattish floor of considerable extent. Others are Viejas, Cotton- wood, and Morena valleys. Some of the basin floors exhibit the ancient landscape little modified by erosion while others have stood sufficiently low relative to their surroundings so that they have received consider- able deposits of alluvium or have harbored lakes in which sediment accumulated. Field study indicates that these basins actually are grabens which either sank as the Peninsular block was being elevated or failed to rise as far as their surrouiulings. Thus they are features comparable to those found in the Sierra Nevada (Tahoe and Sierra basins and various others), to be expected in a great mass which is being elevated along major faults. The deformation of such a block is complex and it yields to the deforming forces by bending an;l minor fracturing, the latter finding more expression in relief features than the former. At various places in the range there are a number of long, narrow depressions which appear to have resulted from erosion in the crushed zone of larger faults. The recency of uplift of the Peninsular block is testified to by tlie boldness and small amount of erosion of the eastern scarp and the depth and narrowiiess of canyons cutting both it and the western slope. Some have held that the great eastern face is an erosion product, though its evolution by this mechanism has not been very clearly brought out. However, comparison of its features with those of the eastern face of the Sierra Nevada and the clear evidence of a major fracture system along the base of the Peninsular block indicate beyond much doubt that this scarp is the product of great dislocations which have caused elevation of the range and sinking of the adjacent Imperial-Coachella graben. The eastern Peninsular scarp is highest and most abrupt at the northern end. Farther south in places there is a series of parallel northwest trending mountainous ridges, clearly fault-block mountains, between which are sharply outlined sunken blocks like Collins, Borego, and Clark Lake valleys. The Santa Rosa Mountains is the principal of these ridges, with a long, .straight scarp a few thousand feet high on the southwest side, above whicli there is a slope (tlie old erosion surface) descending to the northea.st from 8,000 to about 6,000 feet above sea level. Beyond is the great ea.stern scarp. In other places the eastern front is less simple indicating paralle' faulting with distribution of the dislocation along the various fractures giving step-fault topograpliy. Between the nortlicrnmost part of the San Jacinto section of the Peninsular Range and the San Bernardino section of the Transverse 1952] PENINSULAR RANGES 201 ^ ' .it % Fig. 140. San Jacinto section of the IVninsular RongeR west of Palm Springs, showing abrupt front which is controlled by recent elevation along faults. Discontinuous nlluviiil fans at mouths of canyontj in the range and the relatively flat floor of the Coachella section of the Imperial Valley graben make the foreground. Photo bjf Fairchtld Aerial Surreya. 202 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 1 ^ '■ I » * >i !Mj «> MjH lSfc»^K Fio. 141. Marine terrace and recenUy eroded sea di«E along Palos Verdes HiUs, a one lime isli and which bus been joined t„ .he shore, rko,.. Uy F.uchM .Ur.aJ .Sur...,, 1952] PENINSULAR RANGES 203 system is San Gorgonio Pass whose crest is about 2,600 feet above sea level. Ilifih points on the ranges immediately adjacent rise from 8,000 to 9,000 feet. Prom its summit, the pass slopes gently eastward where it merges imperceptibly with the northern end of the Coachella valley. On the western side, the slope is quite as gentle toward the Beaumont Plain, but the margin between the pass and this plain, while not prominent, is more conspicuous than that on the eastern side. The main part of the San Gorgonio depression is a lowland 2 to 3 miles wide and about 18 miles long; it is a narrow fault trough or graben filled to a great depth with sediment of quite recent depo- sition. Bedrock comparable with that exposed in the adjacent San Jacinto and San Bernardino ranges therefore must stand a consider- able distance below the surface of the trough. The southern boundary of San Gorgonio Pass is the spectacular, battered fault scarp of the San Jacinto Range. At the eastern end "of the pass, the sheer mountain front bends from east-west to more nearly north-south, and in this angle lies the famous desert resort of Palm Springs. The northern margin of the pass is not so conspicuous, partly because the high peaks of the San Bernardino Range lie farther from its base than those of the San Jacinto Mountains and partly because of a foothill belt which lies between the pass and the former range. In the narrow fault trough between the two ranges there has been greater deposition of sediment from the northern range than from the southern, hence the northern side of the pass stands 300 to 500 feet higher than the southern. Although the San Andreas fault passes diagonally along the foot- hill belt of the San Bernardino Range, other faults are responsible for the difference in elevation between the pa.ss and the summit of the mountains. The Banning fault makes a group of scarps along the northern side of San Gorgonio Pass, some of the movements being so late that they have tilted recently formed alluvial fans. Wind blowing over sedimentary deposits in the pass have swept sand into drifts that are found on both windward and leeward sides of ridges projecting from the San Jacinto Mountains. Excellent ex- amples of sand blasting, the erosive effect of the wind, are found near some of the drifts. Roughly paralleling the southern California coast and lying about 20 miles inland are the Santa Ana Mountains which run for some distance southeast of the Santa Ana River. The mountains are a fault block of rather complex structure which has been elevated on the northeastern side along the great Elsinore fault system and tilted southwestward toward the ocean. The crest, lying along the northeast side of the block, is rather uneven, increases in elevation southeast from the Santa Ana River, and culminates in Santiago Peak (eleva- tion 5,680 feet). On the northeastern side of the block, the range front is a steep, battered fault scarp, drained by short streams that run into Temescal Wash at its base. In contrast, to the southwest of the crest, long ridges slope toward the ocean. Santiago Creek is the principal stream on this side and drains practically all of it. The Santa Ana Mountains, like the nearby San Gabriel and San Bernardino ranges, have been uplifted during Plei.stocene time. The Elsinore fault along which the uplift has occurred is an extremely complex system, no single fault running continuously through the entire length of the zone. The northern side of the range is terminated by the Whittier fault which runs westward from the Elsinore zone. Northeast of the Santa Ana River, this mountainous belt is continued by the Puente Hills. The Puente Hills are relatively low and inconspicuous as compared with the Santa Ana block. The Palos Verdes Hills are an isolated upland peninsula projecting into the ocean along the western side of the south Coastal Plain west of the city of Long Beach. The general features of this upland resemble those of the islands off the coast of southern California and it is evident that during parts of Pleistocene time it. too, was separated from the mainland. Northwest of the Palos Verdes Hills a belt of irregular sand dunes extends inland from the coast, overlapping the lowland and the northwestern border of the hills. The peninsula is small, measuring about 9i miles long and 4 to 5 miles wide; its highest point, San Pedro Hill, stands only 1.480 feet above sea level. The crest and most of the upper slopes of the area are a rolling upland comprised of smoothly rounded hills and wide, gently sloping valleys. Along the lower slopes is a series of marine terraces which are being indented by deep canyons that are working inland and gradually destroying the rolling upland. The west and south coasts of the peninsula terminate in a sea cliff ranging from 50 feet high at Long Point to 200 feet at Malaga Cove and 300 feet at Bluff Cove. It averages between 100 and 150 feet. Along the east coast at the city of San Pedro, the cliff is about 50 feet high. The Palos Verdes Hills form a conspicuous uplift along the coast where deformation during the late Pliocene, middle Pleistocene, and late Pleistocene can be recognized. The boundary between the hills and lowland is thought to be a fault, but such does not show at the surface. However, this northern boundary has been the most mobile section of the entire Palos Verdes area. The strata composing the hills have been thro^vn into mostly broad, gentle folds, though in a few- places they are steeply dipping and locally overturnetl. The rolling upland is believed to be part of an old erosion surface developed over a much wider area before the isolation of the Palos Verdes Hills as an island. It is characterized by widely flaring valleys separated by round crested ridges, the maximum relief preserved being about 700 feet. These valleys are sharply contrasted with the narrow gorges advancing into the lower slopes from the shoreline. 204 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. 158 When the upland topography was evolved eaiinot be exactly deter- mined, but probably it had been eonipleted by early or middle Pleis- tocene time. A number of undrained depressions are present in the upland area, being most numerous at the northwest end. They are thought to have been formed by solution of parts of the thin limestone beds that are known to underlie the area with consequent settling of overlying strata into the voids which were left, though drainage changes also may be responsible for some of them. Tlie most striking features of the Palos Verdes Hills are the ele- vated marine terraces of which 13 have been recognized. The terraces range in height above sea level from about 100 to 1,300 feet. The gentle slopes on San Pedro Hill above an altitude of 1,425 feet may repre- sent a still higher terrace formed wlien the island was completely submerged, but this has not yet been proved. The lower and therefore younger terraces naturally are best preserved and most easily identi- fied ; they are most clearly visible on the windward west coast and the southwest coast from San Pedro Ilill to Point Fermin where they have been eroded into the most resistant rock. Between the two areas the continuity is broken by erosion of the steep slope and by land- sliding. On the leeward slopes where waves cut into weak rock, terraces are exceptionally wide, but, where the rock is more resistant, the weaker wave action developed less well-defined terraces. In places the terraces appear to merge, probably because of accumulation of non-marine debris after emergence. Locally this non-marine cover is at least 100 feet thick. In some places it seems to have spread onto still lower terraces concealing the sea cliffs between. The height of sea clilTs between the different terraces is not uniform, but actually meas- urement is not possible because of later erosion and deposition. The terraces indicate that the elevation of the Palos Verdes Hills followed the normal pattern, taking place more rapidly during cer- tain intervals and then perhaps almost ceasing for a time. The cutting of the terraces occurred during the episodes of stability. Along the northern border of the Palos Verdes Hills the lowest terrace was deformed following emergence and deposition of the non- marine cover. Along most of the west coast and almost all the south coast, the lowest elevated terrace has been destroyed by erosion de- veloping the present terrace at sea level. The valley now occupied by GafFey Street in San Pedro was cut across the warped lower terrace by an antecedent stream or by a stream which breached the Gaffey anticline, running through this section, and captured a stream for- merly draining southeastward north of the anticline. It seems prob- able that recent slight growth of the Gaffey anticline has caused impounding of the water of Bixby slough north of the anticline. There are numerous landslides at various places. One extensive area forms the hummocky area inland from Portuguese Point and Inspiration Point and is explained by movement along a slipping plane formed by a water-soaked bed (if tuft'.' A large slump of difl'erent type took place in 1929 about a quarter of a mile ea.st of Point Fermin. A semi-elliptical area extending for 1,000 feet along the sea cliff and 400 feet inland moved seaward as a body, leaving a main fissure f) to 10 feet wide in an irregularly fissured zone ')() to 100 feet wide. This slide was attributed to sliding on the slippery surface of a shale bed inclined seaward in an anticlinal fold. Soon after it was formed the main fissure was filled with fossiliferous marine sand from Second and Beacon Streets. Movement took place again in 1940 suggesting that the slumped mass rotated upward as it moved toward the ocean. Exceptionally hea\'y rains in 1941 caused the slide to become active again indicating that stability has not yet been reached. San Gabriel Valley This plain, like the San Fernando, is about 20 miles long, 7 to 10 miles wide for most of its length, but narrows to little more than 2 miles at its eastern end. The gentle slope of its surface is to the south. Rising abruptly to the north are the high San Gabriel Mountains. The debris cone being formed by the San Gabriel River occupies the central part of the valley extending from the mouth of the moun- tain canyon across the plain and through the Whittier Narrows to the Coa.stal Plain. This area of active deposition is extended ea.st and west of the cone by accumulations of smaller streams coming from the San Gabriel Mountains. Dissected older alluvium covers most of the east and west parts of the valley and is found elsewhere, and its soil zone is reddish-brown, whereas this coloration is not present in areas of active deposition. Uplift of the San Gabriel Mountains has been responsible for dissection of the cones on that side of the valley where there are many high remnants of old cones fringing the mountain front between the canyon mouths. The head of San Dimas cone which covers the floor of the narrow eastern part of the valley has been cut by streams to a depth of 125 feet. Toward the central part of San Gabriel Valley, this older dissected surface gradually merges into the surface where depo- sition is going on. Steep-sided bedrock hills project here and there through the allu- vium and contrast strikingly with the general topography of the valley. All are near the sides of the valley and around them the alluvial deposits are comparatively thin. Wells in the central part of the valley show a thickness of 1,000 to at least 2,000 feet for the alluvial fill; this can only be accounted for by substantial subsidence of the bed- rock, since the deposits extend more than a thousand feet below sea level. At the east end of the San Gabriel Valley in the vicinity of La Verne, the alluvial plain narrows to a width of about 2 miles and then widens • Tuft is a volcanic rocl< made of small fragments of lava developed during volcanic explosions. 1952 PENINSULAR RANGES 205 into tlie iipper Santa Ana Valloy. wliii'li is about 40 miles lonfj from west to east. The wicUli of its western part is about 20 miles, and tleereases almost to a point at the eastern end. Under tlie compara- tively even surface of the valley is an irre^'ular bedrock floor covered in places by more than 1,000 feet of alluvium which has come prin- cipally from the San Gabriel and San Bernardino mountains. The greater part of the upper Santa Ana Valley is covered with undissected, recently deposited alluvium, but around the mar^'ins, particularly the southern, and at places farther within the basin there are eroded remnants of hifiher deposition surfaces with their char- acteristic reddish-brown soil zones. The Santa Ana River, below the San Jacinto fault at San Ber- nardino, has cut throu-rh the older alluvial deposits to depths of 50 to 100 feet aiul flows on a narrow flood plain which it has formed between these hifrh banks. The river lies south of the present area of active accumulation of sediment from the San Gabriel Mountains. The two facts just presented suprj-'cst that the central part of the Santa Ana Valley has been recently .subsidinfr. The Coastal Plain extends alon;; the ocean south of the Santa Monica Mountains for about 50 miles and extends inland for 12 to 20 miles. Except for the San Pedro Hills, which are an isolated prroup risinjr about 1,500 feet above sea level near the coast line, the plain has a relatively even surface broken here and there by low hills and mesas. The ea.stern part has been built up from the shallow sea floor durinkptl saml bar stiindinE snmf distance off shore. Peninsular Ranjres in backf:riiund. Photo by Spenre Air Photot. 210 EVOLUTION OP THE CALIFORNIA LANDSCAPE [Bull. ir)S diameter of 10 to 20 feet, calletl prairie mounds. It is thouplit that these small eminenees may represent both tlie accumulation of sand about and the irrej;ular removal of sand between bushes or otlu'r clumps of ve{;etation. .Since the hillocks are present not only over the top of the mesa but alonfj its marjrinal slope, the probability is that they were formed as the land rose and the ocean cut terraces below the San Diejro level. Duriiifr such an epoch, there probably was plenty of available sand which the wind drifted inland and piled wherever an obstacle was present. The beach ridges previously referred to are numerous north of the San Diego River where they have caused the partial develoi)ment of a trellis drainage by the streams eroding Tecolote Canyon and smaller canyons east of La Jolla. Elsewhere in the mesa section the drainage is the normal dendritic or treelike type. The beach ridges are composed largely of sand which either shows poor stratification or none at all. The San Diego Mesa is but little damaged by stream erosion and therefore is in the youthful stage. The northern portion, especially the section immediately adjacent to the .south rim of Mesa Valley and Linda Vista terrace to the north is less dissected than the part to the south, probably because of the harder rock in the Linda Vista area and the closer spacing of valleys south of Choyas Valley. Many of the canyons cutting the mesa have quite steep slopes and their tops meet the mesa surface in a sharp angle. The San Diego Mesa probably is also represented by parts of the upper surface of Point Loma though faulting in that area has tilted some of the remnants, and also by a much less evident surface about half-way up the southern and western slopes of Soledad Mountain where again tilting has occurred. The western sides of the San Diego Mesa and the sides of some of the larger valleys exhibit well-preserved remnants of lower, younger terraces, of which there are four principal levels and others much less well developed. The principal ones are the Avondale, standing 200 to 250 feet above sea level ; the Chula Vista (100 to 130 feet) ; the Nestor (25 to 100 feet) ; the Tia Juana (20 to 50 feet). Southward from Otay Valley these terraces, like the San Diego Mesa, stand at progressively higher elevations and are separated by greater vertical distances. Since the terraces represent surfaces of marine erosion covered by a thin veneer of deposits, it is evident that uplift has been greater and more rapid toward the Mexican border than farther north. All of the terraces are probably younger than middle Pleistocene ; they testify to dominant vertical elevation in the San Diego region while farther north there was considerable compressional deformation dur- ing the same epoch. In the older rocks of the Peninsular Range east of the coastal mesa belt, remnants of a much older surface can be distinguished clearly which has been called the Poway Terrace because of its conspicuous development in the hilltops south of Poway Valley. East of Linda Vista Mesa it can be seen at the tops of hills 800 to 900 feet above sea level at the west but slo|)iiig u|>ward to elevations of 1,100 to 2,100 feet 5 to 20 miles eastward. The terrace was not developed by wave action, as were those previously described, but represents a surface evolved principally by rivers which had reached advanced maturity or possibly old age. Many eminences rose above the general level, but it is uncertain which of these were developed by erosioTi and which by faulting. The same surface is preserved in parts of the vipper drainage basin of the San Diego River as a rolling upland only partly destroyed by canyons evolved during a late cycle of uplift. Also in parts of the region aromid Potrero and extending with interruptions far to the east of Carpo and for an unknown distance into Lower California, there is an ancient erosion surface which may well be the equivalent of that just described. Some have considered this elevated surface as an ancient, nuich dissected and warped marine terrace evolved during the Eocene epoch, but it seems much more probable that it was a surface developed above .sea level primarily by rivers not earlier than Pliocene time. Differences in geologic structure aiul rock resistance have caused various irregularities in the shoreline of the San Diego region. Resist- ant masses of rock form promontories because waves cannot so easily destroy them as they can weaker materials. The embayments or coves between the headlands have been partially filled by streams emptying into them and by sand driven in bj' waves. North of La Jolla, the San Diego Mesa has been quite evenly attacked by wave erosion with the formation of a long .stretch of cliffs at the ba.se of which there is a narrow beach. The land appears to be sinking slowly so that during storms the waves are able to attack the base of the cliffs, undercutting them with resultant landslides. In this section the rate of cliff retreat is fairly rapid. About a mile south of Scripps Institute near La Jolla, where there is a mass of resistant rock, the coast projects about a mile into the ocean. Because of differences in resistance of various parts of the rock to erosion, waves have sculptured caves, .small arches, and irregular stacks. A few feet above high tide is a narrow bench or terrace which some have believed to represent recent uplift; on the other hand it may be the product of erosion during especially severe storms. South of La Jolla the coast is irregular for about 3 miles to the beginning of Pacific Beach, where weaker rocks and other factors have made easier wave erosion. In this section is a terrace upon which the community of Pacific Beach is located. Debris evolved in erosion of this terrace and also that brought in by streams has been shifted southward by 19521 PENINSULAR RANGES 211 waves and coastwise currents to be deposited almost completely across the mouth of Mission Bay wliich was formerly known as False Bay and by the Spanish as Puerto Falso. A long spit with a narrow tidal opening at the south is called Mission Beach. Mission Bay appears to be a structural depression, which may be the southern downwarped part of Soledad Mountain. Mission Bay is very sliallow and is being gradually filled by the encroaching delta plain of the San Diego River. Intermittent streams from various canyons also are adding to this deposit. A broad point, known as Bay or Crown Point, is an extension of La Jolla Terrace projecting into Mission Bay from Pacific Beach. Its surface is largely covered with windblown sand. When the sea cut the Crown Point section of La Jolla Terrace, it must have swept up the low ground between Mission Bay and San Diego Bay isolating Point Loma as an island. The low flat land between Old Town and the northeast margin of Point Loma is part of the delta plain of the San Diego Kiver. As the delta plain has growni, the river and its tributaries have occupied many different positions in traversing it, as is shown by earlier maps of the area. Like most streams in this region, the San Diego River has infrequent floods, but when they come a large amount of sediment is brought down to be added to the delta plain and the submarine delta section to the seaward. Some shoals and small islands have been formed in Mission Bay by tidal currents and waves. Point Loma is a long promontory extending from the tidal flats of Mission Bay for 6 miles southward, where it landlocks the western portion of San Diego Bay. This peninsula is about 3 miles wide at the north, narrows to a little more than a mile and a half at the south and stands about 300 feet above sea level. Its flattish top is possibly the equivalent of the San Diego Mesa, from which it may have been isolated by subsidence of the land round about in late Pleistocene time. Parts of the eastern and western side of Point Loma have a narrow terrace standing 2.) or more feet above sea level. The western shoreline is quite irregular owing to variations in resistance of the rocks. San Diego Bay is a long, roughly crescentic, landlocked arm of the ocean with which it is connected by a narrow channel on the ea.st side of Point Loma. The south and southwestern shore of the bay con- sists of North and South islands and a sand spit connecting them and attaching both to the mainland. The two islands may be remnants of the Nestor Terrace (elevation in this part of the San Diego region about 25 feet), but their connection with the mainland resulted from the construction of a long crescentic sand spit by the northward drift- ing of debris brought to the sea by the Tia Juana River which enters the ocean near the Mexican border. Spanish Bight is a small, shallow re-entrant of San Diego Bav between North Island and Coronado. San Diego Bay is relatively shallow except where dredging has maintained a navigable channel. Tidal scour at the entrance has been aided by the building of a jetty which may eventually have important effect upon wave and current action along Coronado and South Island. Shortly after it was built, violent storm waves eroded a large part of Ocean Boulevard west of Hotel del Coronado. A small stone jetty or breakwater was constructed .southeast of the hotel in 1897 and 189S to protect it from wave erosion, and a sea-wall of quarrj' stone was built westward along Ocean Boulevard in 1906 and 1907, and was repaired in 1911 and 1912 because of heavy damage by storm waves. The mainland shore of San Diego Bay is mainly salt marshes and tidal flats except where the Nestor terrace produces a small bluff just above high tide line. Intermittent streams from Las Choyas, Sweet- water, and Otay Valleys have constructed small, marshy delta plains. There is no delta at the mouth of Tia Juana River which flows into the ocean south of San Diego Bay near the Mexican border because waves and currents sweeping along the shore remove debris about as fast is it was deposited. The Nestor Terrace is continuous from the foot of San Diego Mesa — or Otay Mesa as it is calle. Eckis, Rollin, South coastal basin invpstigation — geolopy and ^ound water capacity of valley fill : California Div. Water Resources Bull. 45, 1934. Ellis, A. J., and I^e. C. H.. <_fe<»logy and cround waters of the western part of San Diego County, California : U. S. Geol. Survey Water-Supply Paper 446, 1919. Hertlein. Ij. G., and Grant. I'. S. HI, Geology and paleontology of the marine l*liiK-ene "f San Diego, California : San Diego Soc. Xat. Uist.. vol. 2. 1944. Miller, W. J., Geomorphology of the southern Peninsular Range of California : Geol. Soc. America Bull., vol. 46. pp. LlrW-lSea. 1930. Russell, R. J-. I^and forms of San Gorgonio Pa-ss, southern California : I'niv. California Pub. in Geography, vol. 6. pp. 23121. 1932. Sauer, Carl, Land forms in the Peninsular Range of California as developed about Warner's Hot Springs and Mesa (trande : Univ. California Pub. iu Geog- raphy, Vol. 3. pp. 199-290, 1929. SEA FLOOR SEA FLOOR Knowleiljie of the contour of the ocean floor has been grreatly increased in recent time because of the development of instruments with which rapid determinations of depth can be made. Formerly depths had to be measured by weighted lines let down to the bottom, a time consuming process particularly in the deeper waters. Measure- ments obtained in this way were fairly numerous in places where navigation made them necessary but were widely scattered elsewhere, consequently our concept of submarine landscape was extremely sketchy. In the last two or three decades instruments called fathometers have been perfected which measure depth by reflection of sound waves from the sea bottom, a much more rapid method. In many places, especially in the shallow waters, the topography has been quite accurately worked out and good maps have been made of the suboceanic floor. In deeper waters, although depth measurements are still too few, they are numerous enough so that our concept of the relief has been materially revised. Materials from the ocean floor are obtained by dredging and coring, but of course these operations can extend only to very shallow depths. A moderately complete knowledge of surface materials on the ocean floor has been obtained at shallow depths and even from the deep ocean, but nothing is kno\vii of what lies below. Most of the floor of the ocean is covered with sediment and the lower layers undoubtedly have been consolidated into rock. In a few places in shallow waters there are indications of the thickness of deposits but nothing is known for the deeper. Practically everywhere around continental and island coasts there is the flattish continental shelf sloping gently out to sea from the shore line as much as a few tens to a few hundreds of miles. Beyond this is the continintal slope which descends somewhat more or much more abruptly to the great depths of the ocean. However, off the southern California coast, the picture is quite unique for there is a series of ranges and basins extending for about 160 miles that is much more closely related in structure and topography to the land than to the deep ocean. The continental shelf is very narrow; beyond it is the zone of irregular topography termed the continental borderland. The nor- mal landscape of the shelf is quite different from that of the land as the contours are much simpler ; farther out in the ocean the basins extend deeper below their surroundings than basins on the land and the tops of mountains called submarine banks are much flatter. Because of the basins in the continental borderland off the coa.st of southern California, withdrawal of the sea from this area would leave a_group of large lakes, some up to 1,000 square miles in area, and comparable with many of those now existing within the continent. In depth these imaginary water bodies could exceed any in the United States, the Santa Cruz Basin being 2,880 feet below its rim and the St. Nicholas basin 2,370 feet. Crater Lake in Oregon, deepest in North America is about 2,000 feet while the deepest spot in Lake Tahoe in the Sierra Nevada is more than 1,600 feet below the surface. On the other hand, there are basins not containing lakes deeper than any mentioned ; for example. Saline Valley, which lies between Owens Lake and Death Valley, has its lowest outlet 3,900 feet above it.s base. The area of the submarine basins off the coast of southern California is about 6,300 miles, approximately a fourth of the total extent of the continental borderland in that .section. The basins are roughly elliptical and are elongated northwest and southeast. Submarine find- ings indicate that their walls are long, steep slopes broken by a few val- leys, though there are abrupt changes in the direction of the walls SAN CLEMENTE IS swX - SCA LEVEL- SAN DIEGO S TBOUSH . -SEA LCVEL- catalina is. 'he CATALINA BASIN -SEA LEVEL- SAN NICOLAS BASIN , SEA LEVEL- TELESCOPE PEAK I i,oeo e.ooi SANTA CRUZ BASIN^ FUNERAL PEAK 6,400 DEATH VALLEY> SCALE IN STATUTE MILES VERTICAL X 5 1/2 Fio. 147. Sections across the basins and trouRhs off the coast of southern Cnlifornia. Depths by U. S. Coast and Geodetic Survey and the E. \V. Soripps Institute of Oceanography, After F. P. Shepard and K. O. Emery. (219) 220 EVOLUTION OF THE CALIFORNIA LANDSCAPE [Bull. 158 Basins off the soutbprn California coast which would hold lakes if the sea were withdrawn. After F. P. Shrpard und K. O. Kiitery. apparently controlled by folds or faults. Soundings taken across the basins indicate relatively flat floors broken by moderate irregularities. The rims of the basins which would represent outlets of the lakes if the sea were withdrawn become deeper below sea level toward the .southeast, and most of the basin floors deepen in the same direction. Such islands as are present rise from the northern part of the shelf. All of this suggests that there may have been downwarping in a southeasterly direction, a submergence which would account for the notable widening between the upper margin of the continental slope and the shore line which so sharply contrasts this region with the rest of the California borderland. The relief of this borderland is diverse. At least one peak, probably conical in shape, is present southwest of the Coronados Islands and a few of the banks are elliptical in plan. Most of the eminences are long, relatively narrow ridges, small portions of some of them rising above sea level to form the islands off the southern California coast. The higher parts of the borderland are comparable in size to the short mountain ranges of the adjacent lands. The San Bernardino Ranges rise about 9,000 feet above adjacent basins, while the submarine San Juan Seamount stands roughly 10,000 feet above neighboring Hats. Santa Cruz Island has an elevation of about 9,000 feet above the floor of the Santa Cruz submarine basin, while Cafalina Island comjiares with the Santa Ana Mountains, each about G.OOO feet above surroinid- ing territory. In contrast with the highly sculptured contours of the mountains above sea level, the submarine slopes even where steep in general are relatively smooth. However, there are exceptions, as for example the man.v small canyons in the bank on which San Nicolas Island is located, distinct valleys around" Cortes and Tanner Banks, and one off Catalina Island. Even on the land, some mountains are much more intricately dissected than others. Conspicuous features of this submarine region are the flattish tops characteristic of the submarine banks, features yet unex|)lained. The sea floor in this southern California section compares with the adjacent land in showing more than one direction of trend of ridges, the prevailing being northwest-southeast, like those of the Santa Ana and San Jacinto moinitains on the land. On the north, an ea.st-we.st trend cuts across the other, probably a continuation of structures of the east-west Santa Ynez, Santa Monica, San Gabriel, and San Ber- nardino Ranges. Below sea level there is also a north-.south trend, showni in a ridge southeast of San Clemente Island. This island to- gether with Catalina and the Palos Verdes Hills on the land line up in a north-south direction. A few oval submerged areas are northeast- southwest and thus are at right angles to the dominant trend. Many of the steep slopes in this borderland area in all probability arc fault scarps, as for example otf San Clemente, Catalina. and Coro- nados Islands and ott'shore from the Palos Verdes Hills which now are attached to the land but formerly were one of the islands. The basin between Santa Catalina and San Clemente islands appar- ently is bounded by fault scarps and if so is a graben. There are certain complexities in the scarp on the San Clemente side which have not been explained. In many places the trends of the submarine fault scarps are broken by offsets in fashion quite similar to that observed in .scarps of like origin on the land. Under the ocean marring the normal smoothness of the continental shelf and frequently extending far down the continental slope are deep, narrow gorges very closely simulating those eroded by rivers. That many of them are branching further increases the likeness. Some are confined largely to the continental slope into which they break to depths of many thousands of feet while others project back into the shelf, virtually to the shore line. Some are located olTshore from the mouths of rivers running on the land while others do not have this 1952] SEA FLOOR 221 • S END SANTA CATALINA I SANTA ANA MTS DIABLO RANGE 2000 3. HI Aifua i'niienlr. 107. 200 Springs. 107 Alaliiuna Hills. (H. I") .Mnine«lii I'reek. 17-. 170 Alani.. River. 10.3. KM. IftS Alaska. l.">. 27 .\lralr;il Islanil. 170 Aliler Creek Caiiyon, 121 Aiex.m.ler Valle.v. 2:» Alkali I.:ike. SI All--\meriran Canal, 107 Alnmiinr. ."» Alpine. 20i> County. 14 Alluras lll.ll:t Connty. 80, 81 Aniboy. .sn Anieriean. 15. If* liasin. no. 147 Canvon. 2.% Kiver. 4:i. r.-2. W 147 .Vini>s. no Anacapa. l.*^> .\ncel Islanil. 170 Anlart-rii-. 27 Anticline l{i4 AshfonlMill. 7:t Avawiitz Mountains. SO Avenal tiap. I. "2 Avontlale. 2U> Awahnee Il.ilel. :!l) B Itailwater. 72 Itasilail. .' Kallnrat. 74 Kail Mountain. 11!> Italloon IVinie. :!0 Hanner Canyon. 107 i'eak. ." Ranninc. !>!► fault. 2ai Rarnarrl. 4(1 Barstow. !>1 Basin. Ranees province. 0. l.'j, 10. 27. (B. 04. 70. SO. IS!! Bencn Sliwt. 204 Bear Butte. 127. 12s Creek Canyon, ISli foot Cave. 113 paw Cave, 11.3 River. 147 Beaumont Plain. 20.3 Benton-BtMlie. 70 Station. 76 Berkeley Country Club, 176 Hills. 164. 170, 172, 176 Berryessa Valley. 104 Beverly Hills. 20,-.. 213 Newport, 205 Bighorn Plateau. 30 Bigpine. IfS. M. 66. 6S. 69 Creek. 30 Sulphur Creek. 230 Tujunga River. KM Bullyehoop Mountains. 141 Birch Mountain. 19 Bishop. 1.3. t« Creek. Kt. 57 Bixbv slough. 2fM Black Butte. 122. 127 Mountains. 72 Range. (H. 71,72 Blue Ijike. Xi\. 177 Bluff Cove. LtM Blythe. '.M Riiling Lake. 131 Holani. 120. 127 Creek. 12.S Bnlinns Bay. 170 I.ngmm. 166 Borax Lake. 170. ISO Borego, no. 2tm Valley. 107 Boy Scout Hill. 132 British Columbia, 1.5 Brokeoff voUiino, 131. 132 Brown Mountain. 74 Buckingham Peak. 177, ISO Buena Vista, 1,52 basin. 150 Reservoir. 150 Bullion Motintains, 80 Bumpass Mountain, 132 Huribnri Ridge. 164 Burney Mountain, lift, 1,30, 1.^5 Burnt ljiva.S2. Ill Butte County. 147 Creek. 121 Vollev, 110,120 Cache Creek. 146. 177. 170. ISO Canyon. 177 Caibour Mountain, 13ft Cajon Pass. 185. 187 Calaveras Reservoir, 55 Caldera, 80 Caldwell Cave, 115 California, 113. 185, 189, 206, 219, 220, 225, 229 Coast, 27, 170, 172, 180, 194, 197, 219, 223 Ranges. 13, 139. 141, 152, 157. 177, 180 Development Company, 103 Callahan, 111 Camp Curry, 30 Canada, 10 Canada del Diablo, 186 Canadian border, 119 Canby, 111 Cantua Creek. 150 Cape Mendocino. 225 San Martin. 223 Captain Jack. 113 Cargo Muchacho Mountains. 99 Carmel Canyon, 223. 229 Carpinteria plain. 1S7 CaiTio, 210 Carquinez Canyon, 172 Strait. 14. 145, 172 Carson Range. 18. 21 Valley, 18 Carriio, 99 Creek, 99, 107 Gorge, 107 Ca.scnde Gulch, 128 I-akes. 41. 4.3. .V. Mountains. 122. 128. 1.30. 139. 145, 146 Range, 9, 111, 119, 120, 121, 129, 1.39, 145 volcanoes. 122 Cascadia, 15, 145. 157 Castle Crags, 142 Catalina. KM Island. 220 Cathedral Rocks, 38 Spires, 40 Cedarville, 80. Ki. 85 Cenoioic, 10, 152, 157 deiwsits, 7.3 era. 17. 181 Tertiary. 18 time. 16 Tolcanics. 139, 141. 145 Central Plateau. 131 Valley Project. 55. 1.39, 142 Chagoopa Plateau, .50 Chalk Mountain. 180 Chalone Creek, ISO. 181 Valley. ISO Channel Islands. KM Chaos Crags. 132. 1.34 Jumbles. 132, 1.34. 1.^5 Chester. 130 Chic.1. 146 Creek. 147 China Mountains, 139 I 233 I 234 Cliiquito Crepk, 14 rho(t>Inte MinintJiins. 107 Chovas Vallf.v. '.'lO Chiiln Vistii.21(l CiiKler Cone. 127. 1S2. 1S4. 13."j Cirquo Ppjik. 4i> siiiniiiit. 47 rinromont. is;) Crii-k. 17r. riiirk Uikci;(ia]iui;n, l.'>2 Coast UaiiBC belt. 141, l."i<) Uimces. n. 22, 47. 141. 14.".. 140. I.". ItiO. 1&4, 170, 2») Coast Hills, IK.-. I'laiii, 203, 204. 20.'), 200 Cocopa Mtmntains. lO.S Cold Creek. 177 Collins, 2(H) \alle.v, 107 Colorado, 1(«, KM, lOrt Aiiuediut, 04 riesert.O, N!t, 00 Uivcr. !I0. 103. 107. 108.223 Valley. 04 Colimiliiii plateau. 03, 111 Coliis,T t^ounty. 147 Condrey Mountain. 130 Cop<'o r)ant. 121 Lake. 121 Cordell Bank. 220 Cordoiiiees Creek. 170 Cnn.nado. 200. 21 1 Coronados Islands. 220 Cortes. 220 Coso Mountains. 00 Rnnjie. 71 Costa Mesa. 20.^> Cosumnes Hiver. 147. I'^O Cottonwood. 200 Pass. 4r. Uance. 107 Coyote Canyon. 107 Creek. IIU. 1S.-1 Hills. 20.- Wash, 2(«i Cowles, 107 Cracked Craps. 43 Crater Lake. 210 Basin. 132 Mountain.04, OS. on, 119 Crescent City. 130. 141 Crater. 132 INDEX Cretaceous. 10. 17. 141 period, 22. 145, 157 seas, 2.^ time. 63, 157 Crowu Point, 211 Crystal Cave, ll,-> Springs. 164 Cucnmouga fault, 189 Cuyamaca. 197 CuyaniHcns, 200 D DaKcett, 89 Dalton Canyon. ISO Darwin. 47 Hills. 71 Wash. 71 I>avin Creek. 69 Dumineuez. 21.3 Hills. 205 Donner I>ake. 5.3. 55 Pa.ss. 29 Dos Palmas, 107 Double Head, 111 Drakesbad, 131 Duck Flat, S3 Dnme Canyon, 229 Point, 229 Dunsmuir, 142 Dwinnel Resen-oir, 121 E Eagle I^ke. 86 Peak, 31, 132 range, 107 Rock. 119 Mountain. 119 Kagleville. 85 Lake, 85 East Peak, 104 Echo Lakes hasin, 4,3 ' glacier, 43 valleys, 43 Edgewood, 141 Eel River, 225 El Capitan, 31, 32, 38 I'errito Hill, 172 Elk Valley. 100. 172 El I*asu Mountains, 80 Portal. 31. 32 Prado. 152 Elsinore fault. 203 Emerald Bay. 41, 43 Eocene, 10, IK, 185 epoch, 22, 23, 210 Etna, 142 Eureka. 141.142. 225 F Full Creek Mountain. .'>2 Fallen Leaf. 41 l>ake, 55 Fall River, 113 Fandango Valley, 80 FalseBay, 206. 211 Farallon Islands. 172. 229, 225 Feather River, 15, .52. 145 Fish Creek. 57 Lake Valley, 69 Mountain, 107 Springs, 103 School, 69 Fort Bidwell, ,S5 Friant Dam. -"m Frink Spring. 103 Fryxell. Fritiof. 19 Funeral Ranges, 64, 71 Furnace Creek, 72 Inn, 72, 73 riabilnn Mountains. I.SO (laffey anticline. 204 Street. 204 Garlock fault. 7.5. 89 (Jarner Mountains, 129 Peak. 130 riarnet I^ike, ,52 Genoa Peak, 21 Geysers, 1.31 Gibson Peak, 1.39 Gila River. 04 Valley. 'M Gilbert. G. K..63 Gilta. 141 Glacial epoch, 18, 25, 26, 27, 29. .30, 57 Glacier Peak. 122 Point, 31 Glen Alpine, 43 Glendale, 18!» Glenn County. 146 Godel Creek. ,57 Golden Gate, 27. 164. 170, 172, 229 Canyon, 172 International Exposition, 170 Strait, 172 Gold Lake, .52 Goler Well, 89 INDEX 235 Goosp Lake. 63. 145 Vallex, 82 (.iiHJseiu'sl. 119 volcano, 120 Gorda. 225 Graben. 19 Granada Ranch, 121 Grand Canyon. 223 Granite Oreek, 14 Grant I-ake. 78, 79 Grapevine Canyon. 107 Ranges. 64, 71 Grass Lake, 43 Gray Butte. 122. 128 Great Basin. 89 Plains. 13 Viillev. 9. 13. 14. 22, 25. 47. 142. 145, 150, 152, 157. 170, 172 Western Divide, 45. 51 Greenlnnd. 27 Grilzly Peak. 129. 130. 176 ItroundhoR Cone. 57 Guatay Mountains. 200 Guerneville. 230 Gulf of Ivower California, 99, 103, 108 Gull Lake. 78. 79 Guyot Flat. 49 H Haicht Mountain. 129, 130 Half Dome, 30. 31.40 Moon Lake. 43 Valley, 43 Hall Canyon. 1.S7 Harkness volcano. 131 Hat Creek. 131. 134. 135, 136 Hays Canyon Range, 82. 85, 111 Hayward. 176 fault. 170, 176 rift, 176 system, 176 Healdsbunt. 2.30 Heather Lake. 43 Hemet Valley. 107 Hetch Helchy Reservoir. 55 Valley. 40 High Rooky Uke, 83 Valley. 179 Hitchc, VU) Kern ctliiyoiis, 57 Merced fHiiyuii, ;10 Red Cones, r»7 Sbnst.l Vulley. 120 TiijunKH liiver, IIM Wbitney ('reek, Ij7 Meadow, 57 Yosemite canyon, lis, 55 Valley, 32. 40 Livermore, 170 Valley, 164 Lingo Creek, 104 Llano de .Santa Uosa, 230 Lone Pine. 13, 47. IKl. 07 Peak. 1.3. 49 Long Beach, 1S5. 203, 213 Harbor. 213, 215 Point. 204 Valley. 82, 83, 185 Loon I^ke, .52 Los Angeles, 9, 16, 76. 185, 189, 197, 200, 213 aqueduct, 63 basin, 193 region, 94 River, 193 -Santa Barbara region, 229 GntoB Creek, 145, 150 Lost Hills, 1.52 Creek, 131, 132, 134 Lake, 86 River. 113 Lover's I^ap, 43 Lower Califuriiia, l.~> Klamath Lake. Ill, 113 I^ke, 85 M Madeline Plains, 80 Magee Mountain, 135 Malaga Cove, 204 Mammoth crest, 52 Mountain, 62, 57 Pass. 57 Manitoba, 10 Manix. 91 Manly Lake. 73 Manzanita Lake. VH) Marble. 139 Fork, ■Ml Maria Mountain rungCH. 94, 107 Marin Blork, l*i6 County, 170, 176 peninsula, 1((4, 160, 170 Marysville. 145. 148 basin. 147 Mason \'alley. 107 Mattbes. Dr. F. E.. 13. 19 Matlole River. 225 Mayacnias Mountains. 230 Me«n Hills. 99. 107 Medicine Lake Highland, 111. 113. 128. 129. 130 INDEX Melrose Avenue. 21.^ Mendocino Mountains. 230 Plateau. 164. 230 Range. 1IV4 Merced Canyon. 40 River, 32 canyon, 30 Valley. 101 Mesa Valley. 210 Mesozoic. 10. 139. 141 Mexican border. 99. 104. 107, 185, 197, 206, 210 Mexico. 96. !I9. 103 Middle Creek. 177 dome. 1.52 Farallon. 229 Fork. 14. 1.5. 30. 52 Canyon, 00 Kern River. 57 Ijike. 63. Sii. 85 Mid-Pleistocene, 157, 160, 104, 170, 204, 210 Mill Creek Canyon, 86 Millerton Lake. 55 Miller Mountain. 119 Road. 119 Mill Valley. 131 .Mineral. 130 King. 45 Miocene, 10, 18, 23, 113, 205 epoch, 157 late. 25 -Pliocene. 21 strata, 93 time, 19. 23. 50. 141. 157. 181 valley, 25 Miramontes, 166 Mirror I^ke, 32, 55 Mission Bay, '206, 211 Beach, 211 Modoc, 111 County, 80, 82 Indians, 113, 145 Modoc Lava Beds, 82 Plateau, 1.35. 139 Plateau. 9, 111, 113, 11.5. 129 section. O^i Mojave Desert, 9. 27, 63, 71, 89, 91, 99, 107, 189, 200 River, 89, 91, 189 Mokelumne, 15, 55, 147 Mono, 14 Basin, 76 Cones, 181 ( 'raters, 79. 80 -Inyo craters, 70 Lake. 13. 14. 18. 27. 29, 52, 55, 57, 63, 70, 78. 79, SO Range, .57. .80 Montara block. 16t>. 170 fault. 106; Mountain. 164, 166 Montezuma Hills, 146, 147 Monterey Bay, 104, 170, 223 Canyon. 223, 2-29 Peninsula, 225 Monument, 115 .Monumental, 141 .Morena valley, 200 .Morgan Hill, 132 Mormon Point, 73 Mosquito Pass, 4.i Mossbrne Falls. 1'28 Mount Baker. 122 Bnikei.fr. 131 Buckingham, 177 l>ana, 47 Diablo, 176 E.ldy, 145 (iibbs, 47 Ouyot, .50 Hamilton. 176 Range, 164 Harkness, 132 Helen, 132 Hitchcock. 51 Hoffman. 129 King. 52 Konocti. 177. 180 Langley, 13. 47 Le Conte, 51 Lyell. 30 Mallory, 51 McAdie, 51 McClure, 30 Montgomery, 60 Parker, 78 Rainier, 122 Ritter, 57 Rose, 21 Russell, 51 San Antonio. 189 Jacinto. 107 Shasta. 9. 119. 120, 121, 122, 128, 129. 130, 181 Tallac, 13, 21 Tamalpais, 164 Willinm.son, 13. 19 Wbitney, 13, 19, 25, 43, 45, 47. 49, 50, 51, 52. 65 Wood, 7S Young, 49 Mud Creek, 122 volcanoes, 107 Muir, 4.5. 46. 47 Crest. 51 McCain Spring. 100 Cains Plateau, 197. 200 Cloud. 113. 127. I'JS Rivers. \XI. 145 Coy Mountains, 107 CJavin Peak. 119 (lee Canyon, 18 KitlrickHills, 150 Napa, 104 .Navarro River, 2.10 Mc INDEX 237 Nrslor. 210 Terrnc*. 211 NVvu.la. 71.S2. IM.IU lH>nlfr. IC. Hi K.ills. 3S. -m Ncwi.rk. 172 NewjMtrt Ut'ju-b. 205 Canyon. 22.'i -Inel*'w**IMih llancfs, .SO Noriliii Stiili.in. 14 North AiniTi.-n. 13. 119.219 Itutte. 14.S Chnlonp IVak. ISO Home, ir>2 Karallon. 220 Fork. 1.".. 29. 52. 179. 180 Inland. 20C. 211 Oak Creek. .".7 ° <*oe.Tn Boulevanl. 211 Ojai. 1S."> Basin. ISO Valley. 1S6 (till Dail Mountains. SO Biil.ly. ISO Station. 130 Town. 211 Olicocene. 10 epoch. 23 ( >lvni]>ic Mount.-iins. 14 ( ireson. 1.-.. Nl. s-.>. 111. 113. 119. 128, !.■», 219. 225 lM.rder. i:ffl.l42 Coast Uaoges, 130 Otay. 2f« Mesa. 211 Mountains. 197 Owens Ijjke. 14. IS. 19. 29, 63. 64, 67. 75 Kiver. 14. tS<. 75 \\illev. 13. IS. 19, 27. 4C. .57. 63, 64. 05, 66. 67. 6.S. CO. 75, 70. 107. 206. 211 p Pacific basin, IG Beach. 211 Coast. IC. ( icean. IS. 1.57. 170. 172. ISC. 193. 197 shi>reline.'2nt Bay. 1S7 Pillar Point. ICt! Pilot Knob. 94, 00, ia3 Valley, 75 Pinnacles, 75 National Monument, ISO, ISl Itanger Station. 181 Pitas Point. 187 Pit Biver. SO. 113. 1.30. 1,39, 145 Valley. 82 Pla.va del Bey. 21.3, 215 Pleasant I^nke, ,52 PleistiK^ne. 10. l.S. 57. 110. IGO, 229 deformation, 157 eiK>ch. 71.82, 205 lakes. ISO lava. 177 mountain. 170 rocks. 103 sen. 2t>5 time. 22. ,S0. 119. 127. 141. 145. 185. 193, 203. 204. 205. 211 Pliocene, 10, 71. 72. 205 •early Pleistocene, 19 epoch, IS. S2. i:iO. 1.57. 193 late. 25. 170. 204 time. IH. 110. 12elgadn.225 Dunie, 193 Kerniin, 2. 1.30. 142, 14.'>, 146, 147, 148 Saline Valley. U'.l. 210 Salmon. 141 Mountain. 141 Salton Rasin, 103. 104, 107, lOS Sea, 00. 1(K», 103. KM, 107. lOS Salt WelKs (*anyon. 7.% Vallev, 7.'> San Andreas. 5.'). .SO. 107. 100. 164. 180, 225 fault.170.lSl, 203, 225 rift. 100. 170.176 Sprinss, 164 system. 176 zone, ISO Antonio Canyon, ISO Creek. 180 Bernardino, 185. 200. 205. 220 Conntv. 74 Mountains. 71. SO, 00, 189, 200, 205 Uange, 185, 203, 220 Borja, 107 I4runo fault, 104. 170 Hills, IW Mountain, 164 Clemente, 104 Island, 220 Sand Hills, 04, 00, 100 San Dieijo. 04. lS.->. 200. 210 Bay. 211 Mesa, 206, 210, 211 region, 206 Kiver. 206, 210,211 Dimas cove, 204 Felipe, 107 Creek. 107 Valley. KKI Fernando. 1S5. 204 Valley, 103 Francisco, l.">7, 160, 164, 170, 176 Francisco area. 224 bay, 14. 27. 5.5, 76. 145. 157, Iftl, 166, 170. 172. 220, 230 ■Marin block. 170, 176 Peninsula, 106 Gabriel, 180. 205 Canyon, 189 Mountains, 80, 185, 189, 204. 205 Uange, 180, 203, 2.H0 River. 204 Vallev. 204 INDEX San Gorgonio Pass, 99, 100, 107. 20.3 Peak. 189 Jacinto. 90. KJO. 107. 107. 200 fault, 205 Mountain, 197, 203, 220 ranges, 203 Santa Rosa mass, 107 Joaquin, 145. 140. 147, 152 drainage. .51 Mountain, 7-8 Uiver, 14. 15. 20. 30. 45, 52, 53, .57, 1.50 Valley. 14, 22, 55. 1,50, 152 Jose-Mount Hamilton, 2.30 Juan Seamount, 220, 224 Mateo Point, 172 Miguel, 185, ISO, 104, 107 Nicolas. 104 Island. 220 Pedro. 16(1. 204 Hill. 204. 205, 206 Martir. 107 Quentin Point. 1(M> Rafael Mountains. 157 Ramon. 176. 104 Valley, 176 Santa Ana. 205 Creek, 18,5, 186 Mountains, 197, 203, 220 Uiver, 189, 203, 205 Valley, 185, 205 Barbara, l.SO, 194 County, 157 Island, 193, 104 Catalina, 220 Clara Uiver, 18.5, 187 Valley, 104, 170, 185, 186, 187 ("ruz. ISO Basin. 210, 220 Island, 220 Mountains, 164 Fe Springs, 205, 206 ■Coyote uplift, 206 Inez, 185, 200 •Mountains, 185, 186 Monicii, 103, 205 anticline, 103 Mountains, 185, 189, 193, 194, 205, 213 Plain, 193 Range, 103. 230 region, 229 Paula, 185 Creek, 18.5, 186 Rosa, 185, 180. 197 Mountains, 99, 107, 197, 200 Susana Mountains, 193 Ynez Uange, 185 Santiago Peak, 203 Sawmill Creek. 6S, 09 Mountains, 89 Scott, 139 Creek, 177 Market, 141 Scripps Institute. 210 Seacliff station. 187 Seal Beach. 213 UtK-ks. 160 Searles I.dike. 75 Valley. 7I> Valley. 89 Secret Spring Mountain. 119 Sedimentary rocks, 17 Sennor Canyon. 185 Sentinel Home. 31 Rock. 3S Sepulvetla Cany(Ui. 193 Sequoia Natioual Forest. 52 Park, 45 Serra Cross. 187 Seventeen Palms. 00 Shasta, 121, 122, 127, 128 County. 111. 141 Dam. 55. 139, 142 glaciers, 120 Uiver, 120 Valley. 119. 120, 121, 128 Shastan activity, 127 Sbastina, 121. 122, 128 Sheep Hole Mountains, 89 Sheller Cove, 224, 225 Shepherd Pa.ss. 45 Shore Line Butte, 73 Siberia, 27 Sierra, 52. 150 Buttes, 52 ■Cascade, 18 Madre, 189 Nevada. 9. 10, 13. 14. 1.5, 16. 17. 18. 10. 21, 22, 23, 24, 25, 27, 29, 30. 43. 44. 45. 47. 50. 51. 52. 54. 63. 64, 65, 07, tl8. 69. 71. 75. 76. 78. 79. 89. 110. 128, 130, 141. 142, 145, 1.50. 1.57, 181, 107, 200, 219 Sierran bedrock. 78 canyons. 32, 55 crest, 25 fronts, 65 geology, 13 lakes, 55 landscape, 23 region, 19, 46, 51 scarp, 19 slope, 18 Sierra Pelonn, 89 San Juan de Dios, 197 Valley, 21 SignalHill, 205, 213,215 Silurian Ijake, 80 SilverLake,.52. 78, 79,80 Strand. 2(X( Simi Hills. 103 Siskiyou. 139 County. 111.113 INDEX 23'J Sixty-I^ike basin, 52 SInip Kjilice. 7-1,75,89 S.Hla Ijikc, S!> Basin, 1)1 Soledail Mouutain, L>06, 211 Suiioiiia, lt>4 RniiRe, 164 lUuk. 2.'J0 Soulf Butte. I'.'O Han.h. 120. 121 South Hulte, 14.") Chnlnue. 181 dome. 152 Southeru Oaliforuia, 1S5. 2ftl, 229 I'liiitii- Uailroae Peak, 75 Tetnescal, 193 Wash, 201 Tenaya Canyon. ;«), ;tJ, 38, 55 Tennessee Cove, 106 Terrace, 2tMJ Tertiary, 10,63 deposits, 74 material, 225 rocks, 72, 193 sediments, 142 The Gardens, 82 Incomparable A'alley. 19 Minarets, 57 Thompson Peak. l."!9 Thousand Island Lake, .52 Three Brothers, 31 Thurston Lake, 177, 180 Tia .Juana.210, 211 'J'ibur4>n Peninsula, 166 Timber Mountain. Ill Tionn, 78 Pas-s, 29, 63. 70 road, 78 Tokopah Valley, ;i0 Toawa UanKe. 57 Valley, 57 Tomales Bay, l(i(i, 170 Tiipnuga Beach, 193 Transverse Uanjie. 157, 18.5, 189, 194, 197, 200 Ranges, 9, 10, 15, 16, 99 Treasure Island. 170 Triassic, 10 strata, 139 volcanics, 64 Trinity Alps. 1,39 County. 139 Mountain. 141 River. 141 Trolleyway, 213 Trout Creek, 57 Truckee. 21 Meadows, 19 River, 14. 19. 21,43,63 Canyon, 43 Valley, 43 Tueeulala Falls. 40 Tuff. 204 Tujunca Canyon, 189 Tulare. 1,52 Lake, 1.50 Tule Lake. 111. 113 basin. 111 Tunjtsten Hills. 04 Tunio'l, 57 Tuolunuie Canyon, 2!) Meadows, .5.5 River, 1.5 Twin Lakes, .55 TynibiH. 46 Creek,. 50 U TTbehebe.Croters, 73 Union Pacific Railroad, .89 United States, 13, 14, 27. 72. 99, 100, 219, 224 Coast and Geodetic Survey, 213 Guard, 229 (Jeologieal Survey, 13, 63, 213 \nvy,215 Weather Bureau, 1.3 Upper Lake, 8.3, 85 Merced (.'anyon, 32 Uppermost IMeistocene. 185 V Vallecito, 107 \alley. 107 Valle San Jose, 200 Venice, 213, 215 Ventura, 186 County Courthouse, 187 district. 185 River. 185, 186, 187 YaWey. 186. 187 Vernal Falls. 38 Vicente Mountains, 193 Viejas, 200 Vina, 146 Volcan. 200 Mountain. 213 Volcano Creek, 57 Vulcan's Castle, 132 W Walker River, 55 Walnut Creek, 164 Wallace Canyon, 51 Creek, 50 Warner block, 82 Canvon, 82 Mountains, 63, SO, 81, 82, 85, 86, 111, 145 Range, SO, 82, S3, 85, 86 \aUev, 80, 107, 130 Washington, 14, 15, 82, 111, 119, 122 Column, 32, 38 Weaverville, 142 Weitchpec, 1.39 Westnaard Pass, 69 Westmorland. UK\ West Peak, 164 Whaleback, 119, 120 240 INDEX Wbitf-lnj-o Mountains, 71 Rungr, (Kt.tU. 66. 60 Mountain. i:n.l3-.2 I'dik, 61) Mountains front. 6.^ Whitney, 4li, 47. 127 C'anvon. SI Creel!. 51. 128 cliu'ier. 1-1 Hill, 47, 50 Puss, .')1 reuion. 51 Whittier. 2()4. 2I)."> Wildrose Canyon. 71 Williams. ]4(i. 147 -Clear Lake. 180 Williamson. 46 Willow Creek. 142 Mountain, WJ Willows. 146 Wilson (irove. 2:iO Wilson's Cove. in4 Winyato I'ass, 74, 75 Wiiitel-s, 147 Wintun f;la<-i('r, 12S Y Yule University, 27 Yellow Rutte. 120 Yerha Huena Ishniil. 170 Ytnacio \'alley, 17(> Yolo Basin. 14(1. 147. 177 YoUn Holly Mountains. 141 Yorkville, 230 Yosemite Canyon. 32 Falls, 40 Klnciers. 29. 30 landscape. 40 National Park. 13, 2!>, 47, 76 region, liO. 51 -Tahoe repion. .30 Valley. 2."i. 31. 32, 3S. 40. 52, 55 Young summit. 47 Yreka. 141 Yulia Canyon. '27i Hiver. 1.-). .>S, 146, 147 Yuma. Arizona, »!, 99, 103, 107 tttfj in CALIPOBNIi STATE PRINTINC OFFICE 60455 4-52 lOM m^' DIVISION OF MINES OLAF P. JENKINS, CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES C i LIBRARY tS S' UNIVEIISITY OF CALIFORNIA DAVIS BULLETIN 158 PLATE 2 GREAT VALLEY OF CALIFORNIA Central alluvial plain, about 50 miles wide by 400 miles long, Ivlng between Coast Ranges and Sierra Nevada and containing a basin of inteiior d'ai lage at Its souttiem end Drained by Sacramento and San Joaouin Rivers, which |0in and enter San Francisco Bay, Eastern border (ormed by west-sloping Sierran bedroci* surface, which continues westward beneath alluvium and older sediments. Western border underlain by east-dipping Cretaceous and Cenozoic strata which form a deeply buried synclinal trough, lying beneath Great Valley along its western side. To the south, great oil fields follow anticlinal uplifts which mark the southwestern border of San Joaquin Valley and its southern basin. To the north, Sacramento Valley plain interrupted by Marysville Buttes, remnants of an isolated ancient volcano, SIERRA NEVADA A singular tilted tault-block ot great magnitude, nearly 400 miles long, presenting high, fugged multiple scarp face on eastern front, in contrast to gentle western slope (about 2'-) which disappears under sediments of Great Valley. Deep nver-cut canyons down western slope, their upper courses, especially in mas- sive granites ot higher Sierra, modified by gtactal sculpturing, forming such scenic features as Yosemite Valley. High continuous crest-line culminating in Mt. Whitney (elevation, 14.495.81 1 feet above sea level, highest point m United States) near eastern scarp. Glacial moraines and alluvial tans spreading over fault ntts and dropped blocks along eastern base of range. Metamorphic bedrock (still partly capped by Tertiary volcamcs), containing gold-bearing veins, with north-south structural trend, predominant in western flank and northern end ot Sierra. Northern Sierra boundary definitely marked where bedrock disappears under Cenozoic volcanic cover of Cascade Range, Southern Sierra terminated by Garlock fault, whicti forms northern border of Mojave Desert, and by San Andreas fault on the west where Sierra loins Southern Coast Ranges. Cham of volcanic cones, southern entension ot province which passes through Oregon and Washington. Dominatad by Mt- Shasta, glacier-mantled volcanic cone, elevation 14,152 feet above sea level. Terminated on the south by Lassen Peak, the only active volcano in the United States. Transected by deep canyons of Pit River which flows through range between these two major volcanic cones, after winding across interior Modoc Plateau on way to Sacramento River. SALIENT FEATURES OF THE GEOMORPHIC PROVINCES Interior platform (elevation 4000-6000 feet above sea level), southern extension of Oregon lava plateau, consisting of thick accumulation ot lava tlows and tutf beds with many small volcanic cones. Occasional lakes, marshes, and sluggishly flowing streams- North -south faults m evidence. Province bounded indefinitely by Cascade Range on west and by Basin-Ranges on east and south. STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES DIVISION OF MINES Accompanying Geologic Map CALIFORNIA 1938 .^V^fStfe .-V KLAMATH MOUNTAINS Complex rugged topography. Prominent peaks and ridges 6000-8000 feet above sea level- Drainage transverse and irregular, developed on uplifted plateau. Entire mountain mass cut througn by Klamath River Successive benches with gold-bearmg gravels on sides ot canyons. Province more closely allied to Sierra Nevada than to Coast Ranges, with hard pre-Cretaceous rocks ejiposed by dis- section. Province continues into Oregon. VolcaniQ rocks of Cascade Range on east boundary; Cretaceous sediments on southelast; Franciscan and younger Coast Range formations, traversed by longitudinal faults, on southwest. COAST RANGES System of longitudinal mountain-ranges (2000 to 4000, occasionally 6000 feet elevation above sea level) and valleys. Trend, N. 30" to 40° W,, controlled by folding and faulting. Province terminated on east where strata dip beneath alluvium of Great Valley; on west by Pacific Ocean with mountains rising sharply from uplifted and terraced, wave-cut coast; on north by South Fork Mountains, which possess characteristic trend ot Coast f?anges, but geology of Klamath Moun- tains ; on south, by Transverse Ranges, differing distinctly in structural trend, but containing thick series of late MesoJOic and Cenozoic sedimentary strata in common with Southern Coast Ranges. Continuity of coastal mountain-trend cut off obliquely by open embayments and by change in general direction of coast line, especially to the north. Northern and southern ranges separated by depression of San Francisco Bay area. Continental shelf transected by many submarine can- yons (Mendocino submarine scarp, probably produced by faulting; Monterey submarine canyon, 10,000 feet deep, apparently a submerged river canyon). Northern Coast Ranges dominated by irregular, knobby, landslide-topography of Franciscan formation. Contains fault valleys as yet unmapped. Eastern border characleri2ed by strike-ridges and valleys m Upper Mesozoic strata. Volcanic cones and flows south of Clear Lake. San Francisco Bay area and southern Coast Ranges more diversified and complex, largely controlled by structure of Cenozoic, Cretaceous, and Franciscan sediments. Dominated by ritt of active San Andreas fau't, trend slightly oblique to adjacent ranges, total length over 600 miles from Pt. Arena to Gulf of California idisplacement during 1906 earthquake horizontal, with coast side moving northward]. Coast Range granitic core, extending from southern extremity of Coast Ranges to Farallon Islands, bounded by San Andreas fault on east and by Nacimiento fault zone on west. TRANSVERSE RANGES Complex series of mountain ranges and valleys distinguished by dominant east-west trend m contrast to NW-SE direction o! Coast Ranges and Peninsular Ranges which the Transverse Ranges separate. Structural trends (NW-SE and NE-SW) sub- ordinate to maior east-west direction, significant m the formation of important oil field structures. Cenozoic sedimentary section one of the thickest in the world. Western limit ol province, island group t San Miguel, Santa Rosa, and Santa Cruz Islands); eastern limit, within Mojave Desert, including San Bernardino Mts., ilying on east side of San Andreas fault (trend of fault. N.60°W., a change of 20° 'in direction from its alignment in the Coast Ranges). PENINSULAR RANGES *A series of ranges separatea by longitudinal vaiieys, trending NW-SE. conditioned by erosion along faults, representing active branches of San Andreas system Trend of topography like that of Coast Ranges, but geology more like that of Sierra Nevada, dominating rocks bemg granitic, intruded into older metamorphic series. Province continuous into Lower California, Bounded on east by Colorado Desert in series of right-angle ]ogs due to interruption of fault traces. Los Angeles Basin, and the island group (Santa Catalina, Santa Barbara, and the distinctly terraced ^an Clemente and San Nicolas Islands), together with surrounding continental shelf (cut by deep submarine fault troughs) included in this province. COLORADO DESERT A low-lying barren desert basin, in part (about 245 feet) below sea level, dominated by Salton Sea. Province a depressed block between active branches of alluvium- covered San Andreas fault with southern extension of Mojave Desert on east. Characterized by ancient beach lines and silt deposits of extinct Lake Cahuilla. MOJAVE DESERT Broad interior region of isolated mountain ranges separated by expanses of desert plains. Inclosed drainage with playas, except for Colorado River bordering province on east. Two important fault trends: NW-SE, more prominent; east-west. secondary (apparent alignment with Transverse Ranges significant). Province wedged in sharp angle between Garlock fault (southern boundary Sierra Nevada) and San Andreas fault, where it bends east from major trend. Separated from prominent Basin-Ranges by eastern extension of Garlock fault. BASIN-RANGES Distinctly a Nevada province lying wholly within the Great Basin. Interior drainage with lakes and playas. Typical fault-block structure, made up of roughly parallel ranges alternating with basins or troughs. Death Valley, lowest area m United States I 280 leet below sea leveM. one of these troughs or graben Another, Owens Valley, lying between bold eastern fault-scarp of Sierra Nevada and Inyo Mountains. To the north.Modoc Plateau lying between Basin-Ranges and Cascade Range. m '*. GEOMORPHIC MAP CALIFORNIA PREPARED BY OLAF P. JENKINS 1938 Surface contour interval 2000 feet (lOOOfoot contour stiown witfi dasties). Submarine contour interval 250 fatficms (100-fathom line indicating limit of continental sfielf, sfiown witti dasfies). Acknowledgments. Submarine contours by F. P. Sfiepard (Geol Soc Am) after data of U, S C, & G. S. and U. S G S Faults after new state geologic map Definition of geomorptiic provinces compiled from many sources, publistied and un- publislied. DIVISION OF MINES OLAF P^ JENKINS. CHIEF 7 STATE OF CALIFORNIA DEPARTMENT OF N/TURAL RESOURCES m.isy Lil.iv. W^ Y UNIVERSITY OF CALIFORNIA DAVIS BULLETIN 158 PLATE I OREGON 120° ^-I\ G^ STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES DIVISION OF MINES CLAF P JENKINS, CHIEF SHADED RELIEF MAP OF CALIFORNIA CHIEF ARTIST HAL SHELTON COPYRIGHT BV JEPPESEN & COMPAN ■' DENVER, COLORADO ivH:^e ^^r&--To \ \ i \ o %^^ 'llfv ' r r' '\ V (^ , -^ ' If / j-i^^^f^P <^ Prepared by a ipecial technique o( shading a toposraphic nup, scale 11, 000 ,000. m color, and reducing il pholographicaliy lo (he scale 1 2,000,000 Plate names, county bounda- ries, elevations, contours fault lines, and physiographic data appwi on the accompanying Geomorphic Mop of Co/ifoinio, scale 1:2,000,000, originally published on Sheet III of the Gec/og.t Mop ol Calilnmio. 1 938, by Olaf P. Jenkins. •y ^ 80 160 MILES y ^ IV— M E ^ 1 C id I THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW IPI FEB 3 RECEWHD FEB - 7 2000 PSL MAft - 6 2000!;: received] MAR I 2 Z000| Physical Sciences! '' w S[P 23 12 lU l» K JM 88 -BS m 6 % LIBRARY. UNIVERSITY OF CALIFORNIA, DAVIS hnp7/libnte.ucdav,s.edu/PatronRenew,htm Automated Phons Renewal ,24.hou0-. (530,762-1132 D4613 (4«9)M '^^^^fla^Sjr COLLATE 165882 California. Division of Mines. Bulletin. [1 ::.^^s) Call Number: TN24 C3 A3 no. 158 c.2 165882 TN24 California. Division C3 of Mines. A3 Bulletin. no. 158 c.2 •pHVSlCM COLLATE SCIENCES (2 maps) -rriOo^, io-ai-2-. UBRW L I BR ARV UNIVERSITY OF CALIFORNIA DAVIS ^ JK J- ^t .^...- ^ .-' Vi-'"^ _,^N- > \ e «r ¥r « t