DEPARTMENT OF THE INTERIOR 
 
 JOHN BARTON PAYNE. SECRETARY 
 
 NATIONAL PARK SERVICE 
 
 STEPHEN T. MATHER. DIRECTOR 
 
 EOLOGICAL HISTORY 
 yf THE YELLOWSTONE 
 NATIONAL PARK 
 
 WASHINGTON 
 
 GOVERNMENT PRINTING OFFICE 
 1920 
 

 THE NATIONAL PARKS AT A GLANCE. 
 
 [Number, 19; total area, 10,859 square miles.] 
 
 National parks in 
 order of creation. 
 
 Location. 
 
 Area in 
 square 
 miles. 
 
 Distinctive characteristics. 
 
 Hot Springs 
 
 Middle Arkansas 
 
 H 
 
 
 1S32 
 Yellowstone 
 
 Northwestern Wyo- 
 
 3,348 
 
 Many hotels and boarding houses 20 bath- 
 houses under public control. 
 
 More geysers than in all rest of world together 
 
 1872 
 Sequoia 
 
 ming. 
 Middle eastern Cali- 
 
 252 
 
 Boiling springs Mud volcanoes Petrified for- 
 ests Grand Canyon of the Yellowstone, re- 
 markable for gorgeous coloring Large lakes 
 Many large streams and waterfalls Vast wil- 
 derness, greatest wild bird and animal preserve 
 in world Exceptional trout fishing. 
 
 The Big Tree National Park 12 000 sequoia trees 
 
 1890 
 Yosemite 
 
 fornia. 
 Middle eastern Cali- 
 
 1,125 
 
 over 10 feet in diameter, some 25 to 36 feet in 
 diameter Towering mountain ranges Start- 
 ling precipices Cave of considerable size. 
 
 Valley of world-famed beautv Lofty cliffs Ro- 
 
 1890 
 General Grant 
 
 fornia. 
 
 Middle eastern Cali- 
 
 4 
 
 mantic vistas Many waterfalls of extraor- 
 dinary height 3 groves of big trees High 
 Sierra Waterwheel falls Good trout fishing. 
 
 Created to preserve the celebrated General Grant 
 
 1890 
 Mount Rainier 
 
 fornia. 
 West central Wash- 
 
 324 
 
 Tree, 35 feet in diameter 6 miles from Sequoia 
 National Park. 
 
 Largest accessible single peak glacier system 28 
 
 1899 
 Crater Lake 
 
 ington. 
 Southwestern Oregon 
 
 249 
 
 glaciers, some of large size 48 square miles of 
 glacier, 50 to 500 feet thick Wonderful sub- 
 alpine wild flower fields. 
 
 Lake of extraordinary blue in crater of extinct 
 
 1902 
 Wind Cave 
 
 South Dakota 
 
 17 
 
 volcano Sides 1,000 feet high Interesting lava 
 formations Fine fishing. 
 
 Cavern having many miles of galleries and 
 
 1903 
 Platt... 
 
 Southern Oklahoma 
 
 
 numerous chambers containing peculiar forma- 
 tions. 
 
 Many sulphur and other springs possessing 
 
 1904 
 Sullys Hill 
 
 North Dakota 
 
 u 
 
 medicinal value. 
 Small park with woods, streams, and a lake Is 
 
 1904 
 Mesa Verde 
 
 Southwestern Colo- 
 
 77 
 
 an important wild-animal preserve. 
 Most notable and best preserved prehistoric cliff 
 
 1906 
 Glacier 
 
 rado. 
 Northwestern Mon- 
 
 1 534 
 
 dwellings in United States, if not in the world. 
 Rugged mountain region of unsurpassed Alpine 
 
 1910 
 
 Rocky Mountain. . . 
 1915 
 
 Hawaii. 
 
 tana. 
 
 North middle Colo- 
 rado. 
 
 Hawaii 
 
 397J 
 
 118 
 
 character 250 glacier-fed lakes of romantic 
 beauty 60 small glaciers Precipices thou- 
 sands of feet deep Almost sensational scenery 
 of marked individuality Fine trout fishing. 
 
 Heart of the Rockies Snowy range, peaks 11,000 
 to 14,250 feet altitude Remarkable records of 
 glacial period. 
 
 Three separate areas Kilauea and Mauna Loa 
 
 1916 
 
 Lassen Volcanic... 
 1916 
 
 Mount McKinley . . . 
 1917 
 
 Grand Canyon 
 1919 
 
 Lafayette.. 
 
 Northern California. . . 
 South central Alaska.. 
 
 North central Arizona. 
 Maine coast 
 
 124 
 2,200 
 
 958 
 
 8 
 
 on Hawaii, Haleakala on Maui. 
 
 Only active volcano in United States proper 
 Lassen Peak 10,465 feet Cinder Cone 6,870 
 feet Hot springs Mud geysers. 
 
 Highest mountain in North America Rises 
 higher above surrounding country than any 
 other mountain in the world. 
 
 The greatest example of erosion and the most 
 sublime spectacle in the world. 
 
 The group of granite mountains upon Mount 
 
 1919 
 Zion... 
 
 Southwestern Utah. . . 
 
 120 
 
 Desert Island. 
 Magnificent gorge (Zion Canyon) depth frum 800 
 
 1919 
 
 
 
 to 2,000 feet, with precipitous walls Of great 
 beauty and scenic interest. 
 
Bancroft Li 
 
 
 GEOLOGICAL HISTORY OF THE YELLOWSTONE 
 NATIONAL PARK. 
 
 By ARNOLD HAGUE, 
 
 United States Geological Survey. 
 
 The purpose of this paper is not so much to elucidate any special 
 problem connected with the many interesting geological questions to 
 be found in the Yellowstone Park, as to offer such a general view of 
 the region as will enable the tourist to understand clearly something of 
 its physical geography and geology. 
 
 The Yellowstone Park is situated in the extreme northwestern portion 
 of Wyoming. At the time of the enactment of the law establishing this 
 national reservation the region had been little explored, and its relation 
 to the physical features of the adjacent country was little understood. 
 Since that time surveys have shown that only a narrow strip about 2 
 miles in width is situated in Montana and that a still narrower strip 
 extends westward into Idaho. 
 
 The area of the park as at present defined is somewhat more than 
 3,300 square miles. 
 
 The Central Plateau, with the adjacent mountains, presents a sharply 
 defined region, in strong contrast with the rest of the northern Rocky 
 Mountains. It stands out boldly, is unique in topographical structure, 
 and complete as a geological problem. 
 
 The central portion of the Yellowstone Park is essentially a broad, 
 elevated, volcanic plateau, between 7,000 and 8,500 feet above sea level, 
 and with an average elevation of about 8,000 feet. Surrounding it on 
 the south, east, north, and northwest are mountain ranges with culmi- 
 nating peaks and ridges rising from 2,000 to 4,000 feet above the general 
 level of the inclosed table-land. 
 
 For present purposes it is needless to confine ourselves strictly to legal 
 boundaries, but rather to consider the entire region in its broader physical 
 features. 
 
 South of the park the Tetons stand out prominently above the sur- 
 rounding country, the highest, grandest peaks in the northern Rocky 
 Mountains. The eastern face of this mountain mass rises with unri- 
 valled boldness for nearly 7,000 feet above Jackson Lake. Northward 
 
 3 
 
4 GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 
 
 the ridges fall away abruptly beneath the lavas of the park, only the 
 outlying spurs coming within the limits of the reservation. For the 
 most part the mountains are made up of coarse crystalline gneisses and 
 schists, probably of Archean age, flanked on the northern spurs by 
 upturned Paleozoic strata. To the east of the Tetons, across the broad 
 valley of the Upper Snake, generally known as Jackson Hole, lies the 
 well-known Wind River Range, famous from the earliest days of the 
 Rocky Mountain trappers. The northern end of this range is largely 
 composed of Mesozoic strata, single ridges of Cretaceous sandstone pene- 
 trating still farther northward into the regions of the park and protruding 
 above the great flows of lava. 
 
 THE ABSAROKA RANGE ALONG THE EASTERN EDGE OF THE PARK. 
 
 Along the entire eastern side of the park stretches the Absaroka 
 Range so called from the Indian name of the Crow Nation. The Absa- 
 roka Range is intimately connected with the Wind River Range, the two 
 being so closely related that any line of separation must be drawn more 
 or less arbitrarily, based more upon geological structures and forms of 
 erosion than upon physical limitations. 
 
 The Absarokas offer for more than 80 miles a bold, unbroken barrier; 
 a rough, rugged country, dominated by high peaks and crags from 10,000 
 to 11,000 feet in height. The early trappers found it a forbidding land; 
 prospectors who followed them, a barren one. 
 
 At the northeast corner of the park a confused mass of mountains con- 
 nects the Absarokas with the Snowy Range. This Snowy Range shuts 
 in the park on the north and is an equally rough region of country, with 
 
GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 5 
 
 elevated mountain masses covered \\ith snow the greater part of the 
 year, as tin- name would indicate. Only the southern slopes, which rim 
 in tlu- park region, come within the limit of our investigation. Here the 
 rocks arc mainly granites, gneisses, and schists, the sedimentary beds, 
 for the most part, referable to the pre-Cambrian series. 
 
 The Gallatin Range incloses the park on the north and northwest. 
 It lies directly west of the Snowy, only separated by the broad valley 
 of the Yellowstone River. It is a range of great beauty, of diversified 
 forms, and varied geological problems. Electric IVak, in the northwest- 
 ern corner of the park, is the culminating point in the range, and affords 
 one of the most extended views to be found in this part of the country. 
 
 II IK GALLATIN RANGE IN THE NORTHEASTERN PORTION OF 
 
 THE PARK. 
 
 Archean gneisses form a prominent mass in the range, over which occur 
 ; ies of sandstones, limestones, and shales, of Paleozoic and Mesozoic 
 age, representing Cambrian, Silurian, Devonian, Carboniferous, Trias, 
 Jura, and Cretaceous. Immediately associated with these sedimentary 
 beds, are large masses of intrusive rocks, which have- played an impor- 
 tant part in bringing about the present structural features of the range. 
 They are all of the andesitic type, but show considerable range in 
 mineral composition, including pyroxene, hornblende, and hornblende- 
 mica varieties. These intrusive masses are found in narrow dikes, in 
 immense interbedded sheets forced between the different strata, and as 
 laccolites, a mode of occurrence first described from the Henry Mountains 
 in Utah, by Mr. G. K. Gilbert, but now well recognized elsewhere in the 
 northern Cordillera. 
 
6 GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 
 
 We see then that the Absarokas rise as a formidable barrier on the east- 
 ern side of the park, the Gallatins as a steep mural face on the west side, 
 while the other ranges terminate abruptly, rimming in the park on the 
 north and south, and leaving a depressed region not unlike the parks of 
 Colorado, only covering a more extended area with a relatively deeper 
 basin. The region has been one of profound dynamic action, and the 
 center of mountain building on a grand scale. 
 
 It is not my purpose at the present time to enter upon the details of 
 geological structure of these ranges, each offering its own special study 
 and field of investigation. My desire is simply to call attention to their 
 general features and mutual relations. So far as their age is concerned, 
 evidence goes to show that the action of upheaval was contemporaneous 
 in all of them, and coincident with the powerful dynamic movements 
 which uplifted the north and south ranges, stretching across Colorado, 
 Wyoming, and Montana. This dynamic movement blocked out, for 
 the most part, the Rocky Mountains, near the close of the Cretaceous, 
 although there is good reason to believe that in this region profound 
 faulting and displacement continued the work of mountain building well 
 into the Middle Tertiary period. 
 
 Throughout Tertiary time in the park area, geological history was char- 
 acterized by great volcanic activity, enormous volumes of erupted mate- 
 rial being poured out in the Eocene and Middle Tertiary, continuing with 
 less force through the Pliocene, and extending into Quaternary time. 
 Within very recent times there is no evidence of any considerable out- 
 burst; indeed the region may be considered long since extinct. These 
 volcanic rocks present a wide range in chemical and mineral composi- 
 tion and physical structure. They may all, however, be classed under 
 three great groups andesites with basalts, rhyolites, and basalts fol- 
 lowing each other in the order named. In general, the relative age 
 of each group is clearly and sharply defined, the distribution and mode 
 of occurrence of each presenting characteristics and salient features fre- 
 quently marked by periods of erosion. 
 
 Andesites are the only volcanic rocks which have played an important 
 part in producing the present structural features of the mountains sur- 
 rounding the park. As already mentioned, they occur in large masses in 
 the Gallatin Range, while most of the culminating peaks in the Absarokas 
 are composed of compact andesites and andesitic breccias. On the other 
 hand, the andesites are not confined to the mountains, but played an 
 active role in filling up the interior basin. That the duration of the 
 andesitic eruptions was long continued is made evident by the plant 
 remains found in ash and lava beds through 2,000 feet of volcanic 
 material. 
 
 In early Tertiary times, a volcano burst forth in the northeast corner 
 of this depressed area not far from the junction of the Absaroka and 
 Snowy Ranges. While not to be compared in size and grandeur with the 
 
GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 7 
 
 volcanoes of California and the Cascade Range, it is, for the Rocky 
 Mountains, one of no mean proportions. It rises from a base about 
 6,500 feet above sea level, the culminating peak attaining an elevation of 
 10,000 feet. This gives a height to the volcano of 3,5<x> iVrt from base- 
 to summit, measuring from the Archean rocks of the Yellowstone Valley 
 to the top of Mount Washburn. The average height of the crater rim is 
 about 9,000 feet above sea level, the volcano measuring 15 miles across 
 the base. The eruptive origin of Mount Washburn has long been recog- 
 nized, and it is frequently referred to as a volcano. It is however simply 
 the highest peak among several others, and represents a later outburst 
 which destroyed in a measure the original rim and form of an older 
 crater. The eruptions for the most part were basic andesites. Erosion 
 has so worn away the earlier rocks, and enormous masses of more recent 
 lavas have so obscured the original form of lava flows, that it is not easy 
 for an inexperienced eye to recognize a volcano and the surrounding peaks 
 as the more elevated points in a grand crater wall. By following around 
 on the ancient andesitic rim, and studying the outline of the old crater, 
 together with the composition of its lavas, its true origin and history may 
 readily be made out. It has been named the Sherman volcano. This 
 old volcano of early Tertiary time occupies a prominent place in the 
 geological development of the park, and dates back to the earliest out- 
 bursts of lava which have in this region changed a depressed basin into 
 an elevated plateau. We have here a volcano situated far inland, in an 
 elevated region, in the heart of the Rocky Mountains. It lies on the 
 eastern side of the continent, only a few miles from the great Continental 
 Divide, which sends its waters to both the Atlantic and Pacific. 
 
 After the dying out of the andesitic and basaltic lavas, followed by a 
 period of erosion, immense volumes of rhyolite were erupted, which not 
 only threatened to fill the crater but to bury the outer walls of the vol- 
 cano itself. On all sides the andesitic slopes were submerged beneath the 
 rhyolite to a height of from 8,000 to 8,500 feet. This enormous mass of 
 rhyolite, poured out after the close of the andesitic period, did more than 
 anything else to bring about the present physical features of the park table- 
 land. A tourist visiting all the prominent geyser basins, hot springs, Yel- 
 lowstone Lake, and the Grand Canyon and Falls of the Yellowstone, is not 
 likilv to come upon any other rock than rhyolite, excepting, of course, 
 deposits from the hot springs, unless he ascends Mount Washbuni, A 
 description of the rhyolite region is essentially one of the Central Plateau. 
 Taking the bottom of the basin at 6,500 feet above sea level, these acidic 
 lavas were piled up until the accumulated mass measured 2,000 fee t in 
 thickness. It completely encircled the Gallatin Range, burying its lower 
 slopes on both the east and west sides; it banked up all along the \YI-M 
 flanks of the Absarokas, and buried the outlying spurs of the Teton and 
 the Wind River Plateaus. 
 
8 GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 
 
 The Central Plateau covers an area approximately 50 by 40 miles, with 
 a mean altitude of 8,000 feet. It is accidented by undulating basins of 
 varied outline and scored by deep canyons and gorges. Strictly speak- 
 ing, it is not a plateau ; at least it is by no means a level area, but a rugged 
 country, characterized by bold escarpments and abrupt edges of mesa- 
 like ridges. But few large vents or centers of volcanic activity for the 
 rhyolite have been recognized, the two principal sources being the vol- 
 cano to which reference has already been made and Mount Sheridan in 
 the southern end of the park. Mount Sheridan is the most commanding 
 peak on the plateau, with an elevation 10,385 feet above sea level and 
 2,600 feet above Heart Lake. From the summit of the peak on a clear 
 day one may overlook the entire plateau country and the mountains 
 which shut it in, while almost at the base of the peak lie the magnificent 
 lakes which add so much to the quiet beauty of the region, in contrast 
 to the rugged scenery of the mountains. From no point is the magni- 
 tude and grandeur of the volcanic region so impressive. The lava flows 
 bounded on the east by the Absarokas extend westward not only across 
 the park, but across the Madison Plateau, and out on to the great plains of 
 Snake River, stretching far westward almost without a break in the con- 
 tinuity of eruptive flows. Over the central portion of the park, where 
 the rhyolites are thickest, erosion has failed to penetrate to the under- 
 lying rock. Even such deep gorges as the Yellowstone, Gibbon, and 
 Madison Canyons have nowhere worn through these rhyolite flows. In 
 the Grand Canyon of the Yellowstone the andesitic breccias are found 
 beneath the rhyolites, but the deepest cuts fail to reveal the underlying 
 sedimentary beds. Although the rocks of the plateau for the most part 
 belong to one group of acidic lavas, they by no means present the 
 great uniformity and monotony in field appearance that might be ex- 
 pected. These 2.000 square miles offer as grand a field for the study of 
 structural forms, development of crystallization, and mode of occur- 
 rence of acidic lavas as can be found anywhere in the world. They 
 vary from a nearly holocrystalline rock to one of pure volcanic glass. 
 Obsidian, pumice, pitchstone, ash, breccia, and an endless development 
 of transition forms alternate with the more compact lithoidal lavas 
 which make i'r> the great mass of the rhyolite, and which in colors, 
 texture, and structural developments present an equally varied aspect. 
 In mineral composition these rocks are simple enough. The essential 
 minerals are orthoclase and quartz, with more or less plagioclase. 
 Sanidine is the prevailing feldspar, although in many cases plagioclase 
 forms occur nearly as abundantly as orthoclase. Chemical analyses, 
 whether we consider the rocks from the crater of Mount Sheridan, the 
 summit of the plateau, or the volcanic glass of the world-renowned 
 Obsidian Cliff, present comparatively slight differences in ultimate com- 
 position. 
 
GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 9 
 
 I have dwelt SOUK what in detail upon the nature of these rocks for 
 two reasons: First, because of the difficulty met with by the scientific 
 traveler in recognizing the uniformity and simplicity of chemical com- 
 position of the rhynlite magma over the entire plateau, owing to its 
 great diversity in superficial habit; second, on account of their geolog- 
 ical importance in connection with the unrivaled display of the gey- 
 sers and hot springs. That the energy of the steam and thermal 
 waters dates well back into the period of volcanic action, there is in 
 my opinion very little reason to doubt. As the energy of this under- 
 ground heat is to-day one of the most impressive features of the 
 country, I will defer commenting upon the .geysers and hot springs 
 until speaking of the present condition of the park. 
 
 OBSIDIAN CLIFF. 
 
 Although the rhyolite eruptions were probably of long duration and 
 died out slowly, there is, I think, evidence to show that they occupied 
 a clearly and sharply defined period between the andesites and late basalt 
 eruptions. Since the outpouring of this enormous mass of rhyolite 
 and building up of the plateau, the region has undergone faulting and 
 displacement; immense blocks of lava have been lifted bodily, and the 
 surface features of the country have been modified. Following the rhy- 
 olite came the period of late basalt eruptions, which, in comparison with 
 the andesite and rhyolite eras, was, so far as the park was con- 
 cerned, insignificant, both as regards the area covered by the basalt 
 and its influence in modifying the physical aspect of the region. The 
 basalt occurs as thin sheets overlying the rhyolite and in some 
 937 20 2 
 
10 GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 
 
 instances as dikes cutting the more acidic rocks. It has broken out 
 near the edge of the rhyolite body and occurs most frequently along the 
 Yellowstone Valley, along the western foothills of the Gallatin Range 
 and Madison Plateau, and again south of the Falls River Basin. 
 
 After the greater part of the basalt had been poured out came the 
 glacial ice, which widened and deepened the preexisting drainage 
 channels, cut profound gorges through the rhyolite lavas and modeled 
 the two volcanoes into their present form. Over the greater part of the 
 Cordillera of the central and northern Rocky Mountains, wherever the 
 peaks attain a sufficiently high altitude to attract the moisture-laden 
 clouds, evidences of the former existence of local glaciers are to be 
 found. In the Teton Efange several well-defined characteristic glaciers 
 still exist upon the abrupt slopes of Mount Hay den and Mount Moran. 
 They are the remnants of a much larger system of glaciers. The park 
 region presents so broad a mass of elevated country that the entire 
 plateau was, in glacial times, covered with a heavy capping of ice. 
 Evidences of glacial action are everywhere to be seen. 
 
 Over the Absaroka Range glaciers were forced down into the Lamar 
 and Yellowstone Valleys, thence westward over the top of Mount Everts 
 to the Mammoth Hot Springs Basin. On the opposite side of the park 
 the ice from the summit of the Gallatin Range moved eastward across 
 Swan Valley and passing over the top of Terrace Mountain joined the 
 ice field coming from the east. The united ice sheet plowed its way 
 northward down the valley of the Gardiner to the Lower Yellowstone, 
 where the broad valley may be seen strewn with the material trans- 
 ported from both the east and west rims of the park. 
 
 Since the dying out of the rhyolite eruptions erosion has greatly modi- 
 fied the entire surface features of the park. Some idea of the extent 
 of this action may be realized when it is recalled that the deep canyons 
 of the Yellowstone, Gibbon, and Madison Rivers canyons in the strictest 
 use of the word have all been carved out since that time. To-day 
 these gorges measure several miles in length and from i ,000 to i ,500 feet 
 in depth. 
 
 To the geologist one of the most impressive objects on the park pla- 
 teau is a transported bowlder of granite which rests directly upon the 
 rhyolite near the brink of the Grand Canyon, about 3 miles below the 
 falls of the Yellowstone. It stands alone in the forest, a long way from 
 the nearest glacial bowlder. Glacial detritus carrying granitic material 
 may be traced upon both sides of the canyon wall. This massive block, 
 although irregular in shape and somewhat pointed toward the top, 
 measures 24 feet in length by 20 feet in breadth and stands 18 feet above 
 the base. The nearest point from which it could have been transported 
 is distant 30 or 40 miles. Coming upon it in the solitude of the forest 
 with all its strange surroundings it tells a most impressive story. In 
 
GEOLOGICAL HISTORY OF YELLOWSTONE PARK. II 
 
 no place are tin evidences of frost and fire brought so forcibly together 
 as in tlu Yellowstone National Park. 
 
 Since the close of the ice period no geological events of any moment 
 have brought about any changes in the physical history of the region 
 other than those produced by the direct action of steam and thermal 
 waters. A few insignificant eruptions have probably occurred, but they 
 failed to modify the broad outlines of topographical structure and pre- 
 sent but little of general interest beyond the evidence of the continu- 
 ance of volcanic action into quaternary times. Volcanic activity in the 
 park may be considered as long since extinct. At all events indications 
 of fresh lava flows within historical times are wholly wanting. This 
 
 GLACIAL BOWLDER NEAR GRAND CANYON. 
 
 is not without ink-rest, as evidence of underground heat may be ob- 
 served everywhere throughout the park in the waters of the geysers 
 and hot springs. All our observations point in one direction and lead 
 to the theory that the cause of the high temperatures of these waters 
 must be found in the heated rocks below, and that the origin of the 
 heat is in some way associated with the source of volcanic energy. It 
 by no means follows that the waters themselves are derived from any 
 deep-seated source; on the contrary, investigation tends to show that 
 the waters brought up by the geysers and hot springs are mainly sur- 
 face waters which have percolated downward a sufficient distance to 
 become heated by large volumes of steam ascending through fissures 
 and vents from much greater depths. If this theory is correct it is but 
 
12 GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 
 
 fair to demand that evidence of long-continued action of hot waters 
 and superheated steam should be apparent upon the rocks through 
 which they passed on their way to the surface. This is precisely what 
 one sees in innumerable places on the Central Plateau. Indeed, the 
 decomposition of the lavas of the rhyolite plateau has proceeded, on a 
 most gigantic scale, and could only have taken place after the lapse of 
 an enormous period of time and the giving off of vast quantities of heat, 
 if we are to judge at all by what we see going on around us to-day. The 
 ascending currents of steam and hot water have been powerful geo- 
 logical agents, and have left an indelible impression upon the surface 
 of the country. The most striking example of this action is found in 
 the Grand Canyon of the Yellowstone. From the Lower Falls for 3 miles 
 down the river abrupt walls upon both sides of the canyon, a thousand 
 feet in depth, present a brilliancy and mingling of color beyond the 
 power of description. From the brink of the canyon to the water's 
 edge the walls are sheer bodies of decomposed rhyolite. Varied hues 
 of orange, red, purple, and sulphur-yellow are irregularly blended in one 
 confused mass. There is scarcely a piece of unaltered rock in place. 
 Much of it is changed into kaolin; but from rhyolite, still easily re- 
 cognized, occur transition products of every possible kind to good porce- 
 lain clay. This is the result of the long-continued action of steam and 
 vapors upon the rhyolite lavas. Through this mass of decomposed 
 rhyolite the course of ancient steam vents in their upward passage may 
 still be traced, while at the bottom of the canyon hot springs, fumaroles, 
 and steam vents are still more or less active, but probably with dimin- 
 ished power. 
 
 Still other areas are quite as convincing, if not on so grand a scale, 
 as the Yellowstone Canyon. Josephs Coat Basin, on the east side of 
 the canyon, and Brimstone Hills, on the east side of the Yellowstone 
 Lake, an extensive area on the slopes of the Absaroka Range, both 
 present evidences of the same chemical processes brought about in the 
 same manner. It is not too strong a statement to make to say that the 
 plateau on the east side of the Grand Canyon, from Broad Creek to 
 Pelican Creek, is completely undermined by the action of superheated 
 steam and alkaline waters on the rhyolite lava. Similar processes may 
 be seen going on to-day in all the geyser basins. A long period of time 
 must have been necessary to accomplish these changes. The study of 
 comparatively fresh vents shows almost no change from year to year, 
 although careful scrutiny during a period of five years detects a certain 
 amount of disintegration, but infinitely small in comparison with the 
 great bodies of altered rock. This is well shown in a locality like the 
 Monarch Geyser in the Norris Geyser Basin, where the water is thrown 
 out at regular intervals through a narrow fissure in the rock. 
 
 The Grand Canyon of the Yellowstone offers one of the most impres- 
 sive examples of erosion on a grand scale within recent geological times. 
 
GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 13 
 
 It is self-evident that the deep canyon must be of much later origin than 
 UK- rock through which it has been worn, and it seems quite clear that 
 the course and outlines of the canyon were in great part determined by 
 the easily eroded decomposed material forming the canyon walls, and 
 this in turn was brought about by the slow processes just described. 
 
 The evidence of the antiquity of the hot spring deposits is, perhaps, 
 shown in an equally striking manner and by a wholly different process 
 of geological reasoning. Terrace Mountain is an outlying ridge of the 
 rhyolite plateau just west of the Mammoth Hot Springs. It is covered 
 on the summit with thick beds of travertine, among the oldest portions 
 of the Mammoth Hot Springs deposits. It is the mode of occurrence 
 of these calcareous deposits from the hot waters which has given the 
 name to the mountain. Lying upon the surface of this travertiqe on 
 the top of the mountain are found glacial bowlders brought from the 
 summit of the Gallatin Range, 15 miles away, and transported on the 
 ice sheet across Swan Valley and deposited on the top of the mountain, 
 700 feet above the intervening valley. It offers the strongest possible 
 evidence that the travertine is older than the glacier which has strewn 
 the country with transported material. How much' travertine was 
 eroded by the ice is, of course, impossible to say, but so friable a material 
 would yield readily to glacial movement. 
 
 Still another method of arriving at the great antiquity of the thermal 
 energy and the age of the hot spring formation is by determining the 
 rate of deposition and measuring the thickness of the accumulated sinter. 
 This method, although the one which would perhaps first suggest itself, 
 is, in my opinion, by no means as satisfactory as the geological reasoning 
 already given. It is unsatisfactory because no uniform rate of deposi- 
 tion can be ascertained for even a single area, like the Upper Geyser 
 Basin, and it is still more difficult to arrive at any conclusion as to the 
 growth of the sinter in the past. Moreover, it is quite possible that 
 heavy deposits may have suffered erosion before the present sinter was 
 laid down. It however corroborates other methods and possesses the 
 advantage of being a direct way. 
 
 It may be well to add that there exists the greatest contrast between 
 the deposits of the Mammoth Hot Springs and those found upon the 
 plateau. At the Mammoth Springs they are nearly pure travertin*., 
 with only a trace of silica, analyses showing from 95 to 99 per cent of 
 calcium carbonate. On the plateau, the deposits consist for the most 
 part of siliceous sinter, locally termed "geyserite." The reason for the 
 difference is this: At the Mammoth Hot Springs the steam, although 
 ascending from fissures in the igneous rock, comes in contact with i he- 
 waters found in the Mcsozoic strata, which here form the surface rocks. 
 The Jura or Cretaceous limestones have furnished the lime held in solu- 
 tion and precipitated on the surface as travertine. On the other hand, 
 the mineral constituents of the plateau waters are derived almost 
 
GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 15 
 
 exclusively from the highly acidic lavas, which carry but a small 
 amount of lime. 
 
 Deposition of sinter from the hot waters of the geyser basins depends 
 in a great measure on the amount of silica held in solution, which varies 
 considerably at the different localities and may have varied still more 
 in past time. The silica, as determined by analyses, ranges from 0.22 
 to 0.60 grammes per kilogram of water, the former being the amount 
 found in the water of the caldron of the Excelsior Geyser and the latter 
 at the Coral Spring in the Norris Basin. Analysis shows that from 
 one-fifth to one-third of the mineral matter held in solution consists of 
 silica, the remaining constituents being readily soluble salts carried off 
 by surface drainage. A few springs highly charged with silica, like the 
 Coral, deposit it on the cooling of the waters; but such springs are 
 exceptional. At most springs and geysers it results after evaporation, 
 and not from mere cooling of the water. It seems probable that the 
 nature and amount of alkaline chlorides and carbonates present influ- 
 ence the separation of silica. Temperature also may in some degree 
 influence the deposition. My friend, Mr. Elwood Hofer, has called my 
 attention to an observation of his made in midwinter, while on one of 
 his snowshoe trips through the park. He noticed that certain over- 
 flow pools of spring water, upon being frozen, deposited a considerable 
 amount of mineral matter. He has sent me specimens of this material, 
 which, upon examination, proved to be identical with the silica depos- 
 ited from the Coral Spring upon the cooling of the water. Demijohns of 
 geyser water which have been standing for one or two years have failed 
 to precipitate any silica. Quite recently, in experimenting upon these 
 waters in the laboratory, it was noticed that on reducing them nearly 
 to the freezing point no change took place, but upon freezing the waters 
 there was an abundant separation of free silica. The waters frozen in 
 this way were collected from the Coral Spring. Xorris I'.asin. and the 
 Taurus Geyser, Shoshone Basin. 
 
 Again, there is no doubt that the algous growths flourishing in the hot 
 waters of the park favor the secretion of silica and calcic carbonate and 
 exert a potent influence in building up both the sinter and travertine 
 deposits far greater than one might at first be led to suppose. These 
 processes of assimilation are steadily taking place without interruption, 
 as all algae act as geological agents. The silica and lime brought to the 
 surface by hot springs is, upon the death of the algae, transformed into 
 sinter and travertiiu-. becoming rock masses, which later show scarcrlv 
 any sign of their origin from plant life. Tourists are seldom aware that 
 the harmonious and brilliant tints are due to vegetable growths. 
 <U -velop equally \\vll in the waters of all basins and upon the 
 
 Urnuvs of Mammoth Hot Springs. \VaU-r boils in tin- t'pjx i G 
 r..sin at 198 F., and rudimentary organisms appear at about 185 F., 
 although no definite line can be drawn beyond which all life ceases. 
 
i6 
 
 GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 
 
 These low vegetable organisms occur in nearly all pools, springs, and 
 running water upon the plateau. Wherever boiling waters cool to the 
 latter temperature algae make their appearance, and with the lowering of 
 temperature on exposure to air still more highly organized forms gradually 
 come in. It is believed that at about 140 F. conditions are favorable 
 for a rapid development of numerous species. Many forms of algae 
 flourish within restricted ranges of temperature, and the different species 
 possess characteristic colors and habits of growth dependent upon such 
 changes of temperature. After a little experience it is quite possible, 
 upon noting the nature of the plant life, to make a sure guess as to the 
 temperature of the water in which the species grow. As water in the 
 geyser pools and caldrons frequently stands at or near the boiling point, 
 no life exists at the centers of discharge, but with a rapid lowering of 
 
 ALGAE BASINS. 
 
 temperature algae appear, with corresponding changes of color, in the 
 shallow pools and overflow channels. In the geyser basins the first 
 evidence of vegetation in an overflow stream consists of creamy white 
 filamentary threads, passing into light flesh tints, then to deep salmon. 
 With distance from the source of heat the prevailing colors pass from 
 bright orange to yellow, yellowish green, and emerald, and in the still 
 cooler waters various shades of brown. This, of course, is a simple stats- 
 ment of phenomena which really display highly complex conditions. 
 No two pools or overflow channels are quite alike in their occurrence 
 either as regards flow of water or development of algae. 
 
 Several methods have been devised for ascertaining the growth of 
 deposition of the geyserite. One way is by allowing the water to trickle 
 over twigs, dried grasses, or almost anything exposing considerable 
 
GEOLOGICAL HISTORY OF YELLOWSTONE PARK. I/ 
 
 surface, and noting the amount of incrustation. This way gives the most 
 rapid results, but is far from satisfactory and by no means reproduces 
 the conditions existing in nature. Other methods employed are placing 
 objects on the surface of the water or, still better, partially submerging 
 them in the hot pools, or again by allowing the water to run down an 
 inclined plane with frequent intervals for evaporation and concentration. 
 The vandals who delight to inscribe their names in public places have 
 invaded the geyser basins in large numbers and left their addresses upon 
 the geyserite in various places. It is interesting to note how quickly 
 these inscriptions become indelible by the deposition of the merest film 
 of silica upon the lead-pencil marks, and, at the same time, how slowly 
 they build up. Names and dates known to be 6 and 8 years old remain 
 
 BOWL OF GREAT FOUNTAIN GEYSER, LOWER GEYSER BASIN. 
 
 perfectly legible, and still retain the color and luster of the graphite. 
 That there is some increase in the thickness of the incrustation is evident, 
 although it grows with incredible slowness. Mr. Weed tells me that he 
 has been able, in at least one instance, to chip off this siliceous film and 
 reproduce the writing with all its original distinctness, showing conclu- 
 sively that a slow deposition has taken place. Pencil inscriptions upon 
 the siliceous sinter at Rotomahana Lake, in New Zealand, are said to be 
 legible after the lapse of 20 or 30 years. It is easy to see that various 
 ingenious devices might be planned to estimate- the rate of deposition, 
 but in my opinion none of them equal a close study of the conditions 
 found in nature, especially where investigations of this kind can be 
 watched from year to year. All observations show an rxcrnlin^lv slow 
 building up of the geyserite formation. This is well seen in the repair 
 
i8 
 
 GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 
 
 going on where the rims surrounding the hot pools have been broken 
 down, and where it might be supposed that the building-up process was 
 under the most favorable conditions; yet, in a number of instances, I can 
 see no appreciable change in three or four years. Revisiting hot springs 
 in out-of-the-way places after several years' absence, I am surprised to see 
 that objects that I had noted carefully at the time remain unchanged. 
 Taking the entire area of the Upper Geyser Basin covered by sinter, I 
 believe that the development of the deposit does not exceed one-thirtieth 
 of an inch a year, and this estimate I believe to be much nearer the 
 maximum than the minimum rate of growth. Supposing the deposit 
 around Castle Geyser to have been built up with the same slowness as 
 
 CONE OF CASTLE GEYSER, UPPER GEYSER BASIN. 
 
 observed to-day, and assuming it to grow at the rate given one-thirtieth 
 of an inch a year it would require over 25,000 years to reach its present 
 development. This gives us a great antiquity for the geyserite, but I 
 believe that the deposition of the siliceous sinter in the park has been 
 going on for a still longer period of time. It is certain that the decom- 
 position of the rhyolite of the plateau dates still further back. 
 
 From a geological point of view, there is abundant evidence that ther- 
 mal energy is gradually becoming extinct. Tourists revisiting the park 
 after an absence of two or three years occasionally allude to the springs 
 and geysers as being less active -than formerly and as showing indica- 
 tions of rapidly dying out. It is true that slight changes are constantly 
 taking place, that certain springs become extinct or discharge less water, 
 
GEOLOGICAL HISTORY OF YELLOWSTONE I'AKK. 
 
 but this action is fully counterbalanced by increased activity in other 
 localities. Close examination of the source of the thermal waters fails 
 to detect any diminution in the supply. Moreover, it stands to reason 
 that if the flow of these waters dated geologically speaking far back 
 into the past, the few years embraced within the historical records of 
 the park would be unable to indicate any perceptible change based upon 
 a gradual diminution of the heat. 
 
 The number of geysers, hot springs, mudpots, and paintpots scat- 
 tered over the park exceeds 3,000, and if to these be added the fumaroles 
 and solfataras, from which issue in the aggregate enormous volumes of 
 steam and acid and sulphur vapors, the number of active vents would 
 in all probability be doubled. Each one of these vents is a center of 
 decomposition of the acid lavas. The following list comprises the prin- 
 cipal geysers known in the Norris, Lower, and Upper Geyser Basins. 
 
 NORRIS GEYSER BASIN 15. ' 
 
 Bathtub, 
 Black Growler, 
 Constant, 
 Echinus, 
 
 Bead, 
 
 Clepsystra, 
 
 Cliff, 
 
 Excelsior, 
 
 Fountain, 
 
 Fearless, 
 Hurricane, 
 Minute Man, 
 Monarch , 
 
 New Crater, 
 Pearl, 
 Pebble, 
 Valentine, 
 
 \\teran, 
 
 Vixen, 
 
 Whirligig. 
 
 LOWER GEYSER BASIN 17. 
 
 Fitful, 
 Flood, 
 Great Fountain, 
 
 Kaleidoscope, 
 Narcissus, 
 Pink Cone, 
 
 White Dome, 
 Young Hopeful. 
 
 Jelly, 
 Jet, 
 
 Steady, 
 Surprise, 
 
 
 UPPER GEYSER BASIN 42. 
 
 Artemesia, 
 
 Bee Hive, 
 
 Bijou, 
 
 Brilliant, 
 
 Bulger, 
 
 Cascade, 
 
 Castle, 
 
 Catfish, 
 
 Chimney, 
 
 Churn, 
 
 Comet, 
 
 A comparative study of the analyses of the fresh rhyolite, the various 
 transition products, and the thermal waters points clearly to the fact 
 that the solid contents of these waters are derived for the most part from 
 the volcanic rocks of the plateau. During the progress of tin \\ork of 
 the Geological Survey in the Yellowstone Park tin-re have been collected 
 from many of the more important localities samples of the waters, which 
 have been subjected to searching chemical analyses in the laboratory of 
 the survey, by Messrs. F. A. Gooch and J. E. Whittle 11 
 
 Cub (Big), 
 
 Lioness, 
 
 Spanker, 
 
 Cub (Little), 
 
 Mastiff, 
 
 Splendid, 
 
 Daisy, 
 
 Mortar, 
 
 Sponge, 
 
 Economic, 
 
 Oblong, 
 
 Spouter, 
 
 Fan, 
 
 Old Faithful, 
 
 Sprinkler, 
 
 Giant, 
 
 Restless, 
 
 Sprite, 
 
 Giantess, 
 
 Riverside, 
 
 Tardy, 
 
 Grand, 
 
 Rocket, 
 
 Triplets, 
 
 Grotto, 
 
 Sawmill, 
 
 Turban. 
 
 Jewel, 
 
 Sentinel, 
 
 
 Lion, 
 
 Spasmodic, 
 
 
20 GEOLOGICAL, HISTORY OF YELLOWSTONE PARK. * 
 
 They are all siliceous alkaline waters holding the same mineral con- 
 stituents, but in varying qualities. Silica forms the principal deposit, 
 not only immediately around the springs but over the entire floor of 
 the basins. The carbonates, sulphates, chlorides, and traces of other 
 easily soluble salts are carried off in the waters. Oxides of iron and 
 manganese and occasionally some calcite occur under certain conditions 
 in the caldrons of the hot springs or immediately around their vents. 
 Concentrations from large quantites of these waters fail to show the 
 presence of even a trace of copper, silver, tin, or other metal. Nearly 
 all the waters carry arsenic, the amount present, according to Messrs. 
 Gooch and Whitfield, varying from 0.02 to 0.25 per cent of the mineral 
 matter in solution. 
 
 Among the incrustations found at several of the hot springs and geysers 
 is a leek-green amorphous mineral, which proves on investigation to be 
 scorodite, a hydrous arseniate of iron. The best occurrence observed is 
 at Josephs Coat Springs, on the east side of the Grand Canyon of the 
 Yellowstone, where it occurs as a coating upon the siliceous sinter lining 
 the caldron of a boiling spring. Analysis shows a nearly pure scoro- 
 dite, agreeing closely with the theoretical composition: 
 
 Ferric oxide 34-94 
 
 Arsenic acid 48. 79 
 
 Water 16. 27 
 
 TOO. OO 
 
 Alteration of the scorodite into limonite takes place readily, which in 
 turn undergoes disintegration by the wearing of the water, and is mechani- 
 cally carried away. So far as I know, this is the only occurrence where 
 scorodite has been recognized as deposited from the waters of thermal 
 springs. Although pure scorodite is only sparingly preserved at a few 
 localities in the Yellowstone Park, it is easily recognized by its charac- 
 teristic green color, in strong contrast with the white geyserite and yellow 
 and red oxides of iron. After a little practice the mineral green of scoro- 
 dite is not easily mistaken for the vegetable green of the algeous growths. 
 The latter is associated everywhere with the hot waters, while the former, 
 a rare mineral, is obtained only in small quantities after diligent search. 
 In America traces of arsenic have been reported from several springs in 
 Virginia, and quite recently sodium arseniate has been detected in the 
 hot springs of Ashe County, N. C. Arsenical waters of sufficient strength 
 to be beneficial for remedial purposes and not otherwise deleterious are 
 of rare occurrence. In France the curative properties of arsenical waters 
 have been long recognized, and the famous sanitarium of La Bourboule, 
 in the volcanic district of the Auvergne, has achieved a wide reputation 
 for the efficacy of its waters in certain forms of nervous diseases. Hy- 
 geia Springs carries 0.3 of a grain of sodium arseniate to the gallon. The 
 Yellowstone Park waters, while they carry somewhat less arsenic than 
 those of La Bourboule, greatly exceed the latter in their enormous 
 
GEOLOGICAL HISTORY OF YELLOWSTONE PARK. 21 
 
 overflow. . It is stated that the entire discharge from the springs of La 
 Bourboule amounts to 1,500 gallons per minute. The amount of hot 
 water brought to the surface by the hot springs throughout the park is by 
 no means easily determined, although during the progress of investigations 
 I hope to make an approximate estimate. According to the most accu- 
 rate measurements which could be made, the discharge from the caldron 
 of the Excelsior Geyser amounted to 4,400 gallons of boiling water per 
 minute. The sample of the Excelsior Geyser water collected August 
 25, 1884, yielded 0.19 grain of sodium arsenate to the gallon. It is 
 impossible to say as yet what curative pioperties these park waters may 
 possess in alleviating the ills of mankind. Nothing but an extended 
 experience under proper medical supervision can determine. 
 
 Changes modifying the surface features of the park in recent times are 
 mainly those resulting from the filling up with detrital matenal of the 
 valleys and depressions worn out by glacial ice, and those produced by 
 the prevailing climatic conditions. Between the park country and what 
 is known as the arid regions of the West there is the greatest possible con- 
 trast. Across the Central Plateau and the Absaroka Range the country 
 presents a continuous mountain mass 75 miles in width, with an average 
 elevation unsurpassed by any area of equal extent in the northern Rocky 
 Mountains. It is exceptionally situated to collect the moisture-laden 
 clouds, which coming from the southwest precipitate immense quantities 
 of snow and rain upon the cooled tableland and neighboring mountains. 
 The climate in many respects is quite unlike that found in the adjacent 
 country, as is shown by the meteorological records, the amount of snow 
 and rainfall being higher, and the mean annual temperature lower. 
 Rainstorms occur frequently throughout the summer, while snow is quite 
 likely to fall any time between September and May. Protected by the 
 forests the deep snows of winter lie upon the plateau well into midsum- 
 mer, while at still higher altitudes, in sheltered places, it remains through- 
 out the year. By its topographical structure the park is designed by 
 nature as a reservoir for receiving, storing, and distributing an excep- 
 tional water supply, not exceded by any area near the headwaters of the 
 great continental rivers. The Continental Divide, separating the waters 
 of the Atlantic from those of the Pacific, crosses the park plateau from 
 southeast to northwest. On both sides of this divide lie several large 
 bodies of water, which form so marked a feature in the scenery of the 
 plateau that the region has been designated the lake country of the park. 
 Yellowstone Lake, the largest lake in North America at this altitude 
 (7,740 feet) and one of the largest in the world at so high an elevation 
 above sea level, presents a superficial area of 139 square miles, and a 
 shore line of nearly 100 miles. From measurements made near the 
 outlet of the lake in September, 1886, the driest period of the year, the 
 discharge was found to be i ,525 cubic feet per second, or about 34,000,000 
 imperial gallons per hour. 
 
PUBLICATIONS ON YELLOWSTONE NATIONAL PARK. 
 
 DISTRIBUTED FREE BY THE NATIONAL PARK SERVICE. 
 
 The following publication may be obtained free on written application 
 to the Director of the National Park Service: 
 
 Rules and Regulations, Yellowstone National Park (issued yearly). This pamphlet 
 contains general information of interest to the tourist. 
 
 SOLD BY THE SUPERINTENDENT OF DOCUMENTS. 
 
 The following publications may be obtained from the Superintendent 
 of Documents, Government Printing Office, Washington, D. C., at the 
 prices given. Remittances should be made by money order or in 
 cash: 
 
 National Parks Portfolio, by Robert Sterling Yard. 260 pages, including 270 illus- 
 trations. Pamphlet edition, loose in flexible cover, 35 cents; book edition, con- 
 taining same material securely bound in cloth, 55 cents. 
 
 Contains nine sections, each descriptive of a national park and one larger section devoted to 
 other national parks and monuments. 
 
 Geological History of Yellowstone National Park, by Arnold Hague, 22 pages, 
 including 10 illustrations, 10 cents. (This publication.) 
 
 This pamphlet contains a general resume of the geologic forces that have been active in the 
 Yellowstone National Park. 
 
 Geysers, by Walter Harvey Weed, 32 pages, including 23 illustrations, 10 cents. 
 
 In this pamphlet is a description of the forces which have produced the geysers, and the geysers 
 of the Yellowstone are compared with those in Iceland and New Zealand. 
 
 Fossil Forests of the Yellowstone National Park, by F. H. Knowlton, 32 pages, includ- 
 ing 15 illustrations, 10 cents. 
 
 This pamphlet contains descriptions of the fossil forests of the Yellowstone National Park and 
 an account of their origin. 
 
 MAP. 
 
 A topographic map of the park may be purchased from the Director 
 of the Geological Survey, Washington, D. C., at the price given. Remit- 
 tances should be made by cash or money order. 
 
 Map of Yellowstone National Park, size 28^ by 3 2 inches; scale, 2 miles to the 
 inch. Price, 25 cents. 
 
 The roads, trails, and names are put in black, the streams and lakes in blue, and the relief is 
 indicated by brown contour lines. 
 
 O