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Les diagrammes suivants ii:ustrent la mdthode. 1 2 3 1 2 3 4 5 6 Glaciers of North America, Plate l. Sketcli map showing the distribution of goino of the better-known sUiciors of North America Southern limit of Pleistocene ice sheet intlicateil by a heavy broken line. o • I • •• • I ■ • • • • • • t • • • • . • , • « • • • ' • • • • c • • • • « t t I • • • •••t« • * • • • • I I • • < t t 1 , • • • • • • • I • ■ GLACIERS OF ]^OETH AMEEICA A READING LESSON FOR STUDENTS OF GEOGRAPHY AND GEOLOGY BT ISRAEL C. RUSSELL PROFESSOR OF GEOLOGY, rNIVKRSITY OF MirHIOAK. AUTHOR OW "LAKES OF NORTH AMERICA," ETC. GiNN & 'Compact''/' ' « I' # ■> t . 3 » » I IS J » •• » • . ^ I r • Re Copyright, I897 By ISRAEL O. RUSSELL ALL AIOHTS RESERVED 30.8 • « « • « •:: , ^ GINN' ,V COMfANY . PRO. • •• • • »• • * • « • ■ TO THE EEADER. -*oj»-:o<- Until within the pafit few years, nearly all current knowledge of glaciei-s was based on the study of those of the Alps. Practically all theories of the orrgin, growth, motion, etc., of glaciera were inspired from the same source. An enlargement of the field of study, however, has shown not only that glaciers of the same type as those of Switzerland exist in many other lands, but in numerous instances are larger and present greater divei'sity ; and besides, additional types or " genera " have been discovered that are not represented in Europe or in fact on any of the three continents of the Eastern Hemisphere. As geological and geographical explorations have been extended, it has been found that North America is not only a favorable field for the growth of these twin sciences, but in many ways furnishes the best example of continental development that has as yet been studied. Strange as it may appear in the face of the overshadowing popular interest that centers in the glaciers of the Alps, North America offers more favorable tonditions for the study of existing glaciers and of the records of ancient ice sheets than any other continent. Of each of the three leading tyj^es of glaciers thus far reorganized, namely, the alpine, piedmont, and conti- nental, North America furnishes magnificent examples. In fact there is no other continent, except the little known region about the South Pole, in which other than the alpine type of glaciers exist. Of alpine glaciers representatives occur in North America in abundance and in great variety, ranging from the " pocket editions " about the summits of the High Sierra, California, to the magnificent Seward glacier, Alaska, the largest river of ice flowing from a mountain group that has yet been disco^Aered. Of piedmont glaciera, the type specimen, so to speak, and the only one of the class yet explored, is the great ice sheet that intervenes between IV TO THE UEAUKU. Mount St. Elias ami the Pacific, known as tlie Malaspina glacier. The still larger continental glaciera — of the nature of tlie ice sheet that formerly covered the northern half of North America, and the smaller sheet beneath which northwestern Europe was once buried — are repre- sented in the Northern Hemisphere at the present time by a single example in Greenland. The magnificence of the field for glacial study in North America has only l)e3n appreciated within recent years, and is still unrecognized out- side of a limited circle of special students. By gathering in the book before you the information now available concerning North American glaciera, it has been my aim not only to report the present condition in this country of an important branch of geological and geographical enquiry, but to make you familiar with glacial phenomena in general and stimu- late a (hirst for fresh explorations and renewed study along an almost untrodden path. From what I have seen personally of the glaciers of the United States and Canada, and from glimpses obtained in previous years of thooe of Switzerland and New Zealand, as well as from all that I have read con- cerning the ice fields of other lands, I think I can affirm, without fear of contradiction, that southern Alaska and adjacent portions of Canada offer one of the most promising fields for glacial study that can be found. I shall be more than repaid for the labor expended in writing this little book if it leads even indirectly to a renewal of the explorations now barely begun in that instructive, highly picturesque, and most attractive region. Israel C. Russell. co:n^teis^ts, t CHAI'TEU I. iNTRODt'CTION A typical glacier. — Variations from the type. — The term " glacier " indeflnlte. LkaIMNO ClIAKAtTKlUSTICS OK 'jI-AClERS Mode of nccuimilation. - Hnu- of flow. - Three types of glaciers ; alpine, piedmont, and continental.— Divisions of tin- surface of a glacier, n<5ve and glacier i>roper. - Handed structure.- ({lacier grain. - Moraines : lateral, medial, terminal, and frontal. - Crevasses. — The starting of ercvussfs. — IJergsclirunds. — Ice falls. — Marginal crevasses. — Surface features : glaci.-r tables, sand cones, debris pyramids. — .Melting and drainage ; super- glacial and subglacial streams. — Characteristics of streams Uowing from glaciers. WiiA IS A Glacier ? . . . Glacial Ahrasion Worn and striated rock surfaces. Smoothed and Striated Siriaces not Produced by Glaciers Scorings made by river and lake ice and by ice ttoes. Special Featlres of Glaciated Surfaces Semilunar cracks, chatter marks, disrupted gouges, etc. Glacial Deposits , _ . Lateral moraines. - Perched blocks. - Terminal moraines. - Morainal embankments. — Frontal moraines. - Interlobate moraines. — Till. — Boulder clay. — Drumlins. Glacial Sediments • • • • • • . . , Osars. — Kanies. — Sand and gravel plains. Changes in Topography Produced by Glaciers CHAPTER II. General Distribution of the Glaciers of North America Cordilleran region. — Greenland region. PAGE 1 16 18 19 20 22 28 30 82 CHAPTEU III. Glaciers of the Sierra Nevada ^ 07 The High Sierra „_ Southern limit of glaciers in the United States, Mount Dana Glacier \ „,. Mount Lyell Glacier .... .n ... 40 Parker Creek Glacier ... .,, • • 41 VI CONTENT8. ClUHACTEKISTICS OK TIIK GlaCIKHS OF THE IIuJH SlEHHA Wv.%.-Cr«v««8e«._ Lh, atl.... or rll.lK„.e.l «t,uctur«. -Dirt' b.ui.l..-«iacler 'trfbles' LntV'^'r:,."""^'".'"'"";"'- ""'""•■""'"' ''"■^""*''' '""' """t"'"-'! .ton... -»e Sel-irk mountains. - Observations by W. S Green. - Illecellewaet glacier. - Glacier of the Siiklne Kiver region. - Glaciers of Northwestern Canada described In connection with those of Alaska. 71 CHAPTER VI. Glaciers of Alaska Topographic an.l climatic conditions favoring glaciation. - Height of Mount Login and ot Mount St.EIIa8.-Narrative8 of early voyages. - Belcher, Vancouver, and otlfers- r^rZbTc^VHsr- " "• "*'-^-^' ''■ «• "---«- ---s- Tide-water Glaciers Hutu glacier. — Norris glacier. Taku Glacier . . . **■•••.. Mum Glacier . . Indian names. -Muir's exploration. - Observations by Trofessors Wright and Reid 1 Msit by the present writer. - Glacier bay. _ Thickness of the Ice. - IcebergT two hypotheses concerning. - An ancient forest beneath the ice. - Characteristlcs^f tie glacier's surface. - Dying glacier. - Recent recession. - Vancouver's observa on on he former extent of glacial ice in Glacier bay. o"»ervauon on tne Glaciers on the West Side of Glaciek Bay Pacific glacier. — Glacier of Dundas bay. 74 77 78 80 91 Gt ■i I PAGE 41 1. e- 49 66 66 . 67 71 CONTENTS. VJI I'.VdK Glaciers ok Disenciuntment Bat U2 Turiii-r, Hubbard, and Nuiiatak glaciers. — View from Ua^^nke iiland. — View from Oaier inhind. — Caiio Enciiantiiient. Icy Cai'k ". . . . . . .96 AlI>INE (il.ACIERA 90 Vaiit ik'vi'i region aUxit Momiti! Fiilrweatlier, Lugaii, aiid Ht. Eliai. — View nortliward from Mount St. Kliaa. — 8eward glacier. —ice falls and rapids. — Agassi:^ glacier.— Uuyot glacier. Olacikrs of Lynn Canal 101 Tnya inlet. — Cl.ilkat Inlet. — Davidson glacier. Glaciekh of the Interior 104 (llncitTH of Chilkoot and C'hi'.kat passes. — Observations W>' E. T. Olave. —Glaciers be- tween Yukon luul topper rivers. — Ubservatioi of C. W. lliiyes. — Fredrick Schwntka. — H. T. Allen. AbAENCE of (iLACIEKS IN CENTRAL AND NORTHERN AlAHKA .... 107 Gla( ii;iis OK THE Alaskan Peninsula ano the .ileltian I.'iLANiis . . . 10b Mt. Mukiishin. Piedmont Glaciers • . 100 Characteristics. — Bering glacier. Malaspina Glacier 109 Area. — Lobes. — Characteristics of the uon-moralne-covered surface. — Moraines. — Sur- face of the fringing moraines. — Forests on the moraines. — Character of the outer nuirgin. — Icy cape. — Sitkagi bluifs. — Marginal lakes. — Crater lake. — Lake 'Jastani. — I.akes about the Clialx hills. — Drainage. —Fountain stream. — Vahtse. — Osar, Kame.nnd Kiwik streams. — Sub- and englacial deposits. — (Jsars. — Alluvial cones. — (ilaclal and ocean records. — Kecent advance of the ice. — Fossil shells of living marine species at high elevations. Subsoil Ice . . • 127 Frozen subsoil along the Yukon. — Lieut. CartwcU's explorations on Kowak river. — Ice cliffs of Kschscholtz bay. — Remains of the mammoth. — Character and origin of the tundra. — Deptli of frozen subsoil in Siberia. — Explanations of the origin ()f subsoil ice. — Computations of Prof. K. S. Woodward. — A possible origin of frozen subsoil. 74 CHAPTER VII. 77 78 80 91 Glaciers in the Greenland Region Grinnell Land Observations by members of the Lady Franklin Hay expedition. — Report by Gen. A. W. Greely. — Henrietta Nesndth glacier. — Reports by Lieutenant Lockwootl and Sergeant Brainard. — Mer de Glace Agassiz. — " Chinese Waiy Greenland Extent of continental glacier. — Character of the interior. — Elevation of central part of the ice sheet. — Characteristics of the margins of the Inland ice. — Observations of Lieu- tenant I'eary near Disco island. — Hunil)oldt glacier. — Observations by Dr. Kane on the west coast. — Observations by Dr. Xansen on the east coast. — Reports of Lieutenant Lockwood and Sergeant Brainard concerning glaciers in the north of Greenland. — Cape Britannia. — ExploTations of the interior. — Baron Xordenskiold. — Lieutenant Peary. — Christian Maigaara. — Dr. Nansen. — Importance of the study of Arctic glaciers. — Observations by Chamberlin. 131 131 133 vm CONTENTS. CHAl'TKU VIII. PAOE Climatic Changes iNUiCATKi) in tiik (;i.a. ikiis ok Nohiii AMEmtA . . .140 (;i.«ra.-t.T <.f tlu< ..vl.l,.„,.,.._u.,v,r,lH of n-oei.t reocMloii In tlio glacleri of (•Hllfornla. Or^-go... an.l WiuihlnKt..,,. - HrltlM. (oh.mblfi. - .\la«ka. - y H,.. glaficrn of the NorthtTii llfiiii»i.lierv . THE«>HETI( AI. C'ONSIUEHATIONS ,rQ Influence of dt'brls on the ««lvBn<'.- and retreat of glaciers. * CHAPTEH IX. How AND VVllV Gt.A( IEI18 MoVK . • • • . . The nature of glueial Mow. — (Jl)8erv;.tlons by Koch and Ktocke. IIVI'OTHEHEH OK (il.ACIAI, MoTION The «1I.11„K hypothenlH. _ '• In, SauMure'B theory." - The hypothesis of .Ulatatlon.- The hypothesm o pla«tl.-lty. -The hypotlu-Kin of r-Melation. - The hypotheniH of expannlon an. eontiuetlo..._The hypothe«m of Ihiuefaction un.ler prtxHure. - T!... hypothesis of molecular change. -The hypothesis of granular change. - Observations l.yT. V. Cham- An Eclectic Hvpothesis Summary of the properties of lee. eclectic hypothesis. ■ Sunnnary of glacial »>henoniena. — Authors ot the 100 103 186 CHAPTER X. The LirE History of a Glacieu Periods of growth and decline. - The ano«- line. - Spheroid of 32«. - Birth of a glacier - i)evelopM.ent. - Moraines. - Marginal lakes. - Ice casca.les. - Widening and tlattening of moraines.- Buried forests. - Forest-covered moraines. - Debris pyramids. - Stran.led lateral moraines. - Polished and striated surfaces. - Terminal nu.raines. - .Moralne- damme.1 lakes. - Kock-basin lakes. - l>eath of a glacier. - Climatic cycles. - Pleistocene Ice sheets. Concluding Note Index 190 . 206 . 207 W l-AOK . 1-IU . 160 ili.u8tratio:n^s. -aoJOJoo- 100 103 186 . 100 206 207 P.,ATK 1. it 2. it 3. it 4. tl 5. 4( 0. it 7. H 8. tt it (I SKETcir Mai- of North AMEiiifA Fitioo- CHAPTER I. INTRODUCTION. It iriay be said of glaciei-s in general that, Lhey are bodies of ice formed by the accumulation and consolidation of snow in regions where the snowfall for a series of yeai-s is in excess of the amount melted and that they flow to regions where waste exceeds supply. While a typical glacier is easily recognized, and there is no dissent from what is commonly undei-stood by the name applied to bodies of flow- ing ice, yet the limitations of the term are indefinite. A type may be chosen, as the well-known Mer de Glace, Switzerland, for exam{)le, in which most of the characteristics of glaciei-s are exhibited. Other ice bodies are known, however, equally deserving to be classed as glaciers, that are markedly different from such a typco The vast ice sheet of Greenland exhibits a great departure from the ice streams of Switzerland in certain features ; while the small ice bodies in the Sierra Nevada, California, present minor vacations in other characteristics. In both of these illustrations, and in many others equally at variance with the type chosen, the term glacier is as appropriate as in the case of the ice stream on the border oi the Vale of Chamounix. The difficulties in determining the limitations of the term glacier may be illustrated by the use of the word river. When does a stream cease to be a brook, or a creek, or even a lake, since many lakes are but ♦expan- sions of streams, and reach the dignity of a river? In a similar way, it is difficult to decide when an accumulation of snow acquires sufficient of the characteristics of a typical glacier to be included in the same class ; or again, when a glacier loses motion and becomes a stagnant ice body, when it shall ce?^se to be known by tiie title it ea'-ned when it was au avenue of ice drainage. GLACIERS OF NOIiTH AMKKICA. In instances where the conditions are indefinite or peculiar, only an arbitrary decision can, perhaps, be reached ; but usually the presence or absence of a number of the commonly recognized characteristics of typi- cal glaciers is sutlicientiy pronounced to exclude controversy. I 11' Leading Characteuistics of Glaciers. Mode of Accumulation. — The formation of glaciers in any region depends primarily on climatic conditions. When the climate is such that the amount of snow falling for a term of years is in excess of the amount melted, evaporated, or blown away, perennial snow banks are formed, the more deeply buried portions of whir a become compacted into ice. The change i.om snow to ice is known to r3sult from pressure and from par- tial melting and refreezing. Many observations have been made which show that normal glaciers liave a characteristic flowing motion. The material of which they are composed is drained from regions of accumulation in much the same manner as rivers drain areas where the rainfall exceeds evaporation. This process of ice drainage relieves areas of heavy snowfall from their burdens, and prevents indefinite accumulation. Three Tj'pes of Glaciers. — For convenience of reference the glaciers nov/^ known may be arranged in three classes, namel}', alpine, piedmont^ and continental. These three classes are not always distinct and clearly sejjarable, but typical examples of each may be selected that are well characterized, and dilfer in essential features from typical examples of each of the other classes. In each group there are conspicuous variations which suggest minor or more specific subdivisions. Of the three great classes referred to above, the most widely known is the alpine type, which derives its name from the mountains of central Europe, where it was first studied. Alpine glaciera occur about high peaks and on the summits and flanks of mountain ranges in many parts of the world, but reach their most perfect development in tempernte regions. The Himalayas, the Alps, the mountains of Scandinavia, the Southern Alps of New Zealand, the Cordilleras, etc., furnish well-known examples. Glaciere of this type originate as a rule in am[)hitheatres and cirques, partially surrounded by lofty peaks and oversiiadowing preci- pices, and flow through rugged valleys leading from them as winding ice rivers which carry the excess of snow falling on the mountains to INTUODUCTION. lower regions, where a higher mean annual temperature causes it to melt. They are essentially streams of ice, formed usually by the union of many branches, and end aljruptly when the drainage changes from a solid to a liquid form. (ilaciers of the piedmont type are formed where alpine glaciers leave the rugged defiles through which they flow and expand and unite on an adjacent plain. They may be considered as analogous to lakes, for the reason that they are fed by tributary ice streams. The influx of ice is counterbalanced by melting, especially from the surface and borders of the partially stagnani mass. The chai-acteristics of glaciers of this type are foreshadowed when individual alpine glaciera leave a high-grade gorge and expanil in a lateral valley or on a plain. The expanded terminus of Davidson glacier, on the border of Lynn canal, Alaska, illustrates what may be take, as the first step toward the formation of a piedmont glacier. The semicircular or delta-like ice foot of the Rhone glacier, Switzeiland, v/here it spreads out at the head of the Rhone valley, is a more widely known, although a comparatively diminutive example of the same char- acter. If one fancies a score or more glaciei-s of the Davidson and Rhone type, uniting on a plain and forming a single confluent plateau of ice many square miles in area, he will appreciate the leading characteristics of tlie ice sheets termed piedmont glaciers. A type of the piedmont glacier, and the only one of the class thus far described, is Malaspina glacier, Alaska, situated at the southern base of Mount St. Elias and neighboring mountains, from which it is nourished by many ice streams. This magnificent ice sheet covers an area of 1500 square miles, and is from 1000 to 1500 feet thick. West of Malaspina glacier, and occupying a plain intervening between high mountains and the sea, is another piedmont glacier, knovai as Bering glacier, which is of the same general character as its companion, but has not been explored. Ice bodies of the third class, as their name implies, are of vast extent and may even cover entire continent'^. Existing examples are confined to Greenland and to Antarcti' regions. Others that have now vanished, left unmistakable records over large portions of northeastern North America and northwestern Euroije. The principal characteristics of con- tinental glaciers are their vast extent, their comparatively level surfaces, and the prolongation of portions of tb.eir Iwrdei's into lol>es and even into well-defined streams, where the topographic and other conditions are favorable. 4 GLACIEHS OF NOKTH AMERICA. On comparing the three classes of glaciers just enumerated, one finds that alpine glaciers, when well developed, appear as trunk streams formed by the union of many branches. ^ They usually flow through narrow valleys froii higher to lower regions, and end abruptly in precipitous walls of ice or expand at their extremities and terminate with low frontal slopes, according to local conditions. In many ways they are analogous to rivers. Piedmont glaciers receive many tributaries of the alpine type, are not confined by rocky walls, and do not have the well-defined stream-like flow exhibited by glaciers descending narrow valleys. Tney are only moderately lobed, do not send out well-defined branches, and are in part stagnant, ice masses. Their nearest counterparts in ordinary water drainage, as already mentioned, are found in lakes fed by mountain streams. Continental glaciers are without tributaries, their broad surfaces forming the necessary gathering-ground for snov/ accumulation. Their margins may be strongly lobed, or even send out well-defined tongues of ice, but the area of ice extending beyond the margins of the central snow field is in existing examples comparatively small. Each of the three types of glaciers here enumerated is represented in North America, and their characteristics and distribution will be described in the following chapters. N6v6 and Glacier Proper. — Glaciers of the alpine type, and in a less marked way those of the continental type, have their surfaces divided into two portions, a nev6 or snow region above, and an ice portion below. The lower portion has no specific name, but is frequently desig- nated as the "glacier proper. " The line of demarcation is the snotv line, i.e. the lowest limit of perennial snow. As compacted ice occurs also directly beneath the n^v^ from which it is formed, this division of a glacier into two portions applies only to the surface. Moreover, the position of the dividing line is subject to secular variations. At times, possibly for many consecutive years, in the case of small glaciei-s, the snow may completely cover the true ice, so that one might Avalk over the accumulation and easily mistake it for the snows of a single winter, and be led to conclude that it was not entitled to be considered as a member of the great family of glaciei's. The n4iv6 is composed of str.atified granular snow which is white or grayish white in color. The snow on high mountains is apt to be exceed- ingly fine, light, and dry when first formed ; but by partial melting and ref reccing it acquires a coarae, granular texture, much like compacted hail, INTRODUCTION. and also becomes consolidated and hard. The surface of the n6y6 is many times so softened l)y the warmth between summer storms, that a thin crust of ice is formed when the temperat'ne is again lowered. 1'his crust is buried beneatli the next succeeding snowfall and remains in the growing deposit as a thin stratum of ice. Ndves are almost entirely free from stones or dirt, although even on the highest mountains, the dust borne from naked cliffs is widely spread over their surfaces and diminishes their brilliancy. This general dust-covering is frequently not noticeable until some really clean snow surface is brought in contrast with it. Whcit u lake on the n6y6 is drained and leaves a fresh surface of dazzling whiteness, the surrounding area frequently shows a gray tint by contrast, thus revealing tlie presence of dust which has been sprinkled over it. Sometimes thv. covering of dust, especially on the lower portions of the n(;v(is of alpine glaciers, is sufficiently pronounced to form a definite division plane when buried by subsequent snoAvfalls. Illustrations of such an occurrence may frecpiently be seen in the walls of fissures. In the great open fissures or crevasses that bre'^-k the ndv^s in the region about Mount St. Elias, a dozen more or less distinct strata separated by bands of blue ice, a fraction of an inch thick, or by still more conspicuous dust-stained layers, may be frequently counted. In some instances the layei-s of granular snow are fully fifty leet thick, even after having passed from the light, mealy consistency of freshly fallen snow to the much more compact condition of the granular nf the current. These crevassed banks of snow and ice are common in the St. IClias region, and have been d'scrilxjd by tlie writer.* In the ciise of glaciers that expand on leaving narrow volleys, stresses are produced in other directions than in the cases cited above, and longi- tudinal or more or less regularly radiating breaks are produced. A well- known instance of this nature is furnished by Rhone glacier. It may be judged from this brief sketch that the conditions leading to the fracture of moving ice masses uro exceedingly varied an«l pro(hice diveree results. The series of more regularly arranged fractures, to which special attention has l)een directed, are united by other and less easily explained breaks, so that the detail of the surface of an ice stream, espe- cially when modified by melting, becomes at times wondeifuUy complex. It is only by selecting isolated and well-defined instances for study that the laws governing the behavior of ice under the varied stresses produced in flowing through irregular valleys and over rough surfaces can be at all understood. The ice of glaciers is also broken along planes more or less inclined to their surfaces. Movement takes place along these breaks, and produces thrusts, analogous to the over-thrusts, or under-thrusts, sometimes seen in rocks that have been folded and broken. In fact, the counterpart of many of the structural features observed in rocks, such as faults, folds, joints, contortions, etc., may be observed in the ice of glaciers. Surface Features. — Owing to the presence of crevasses and to unequal melting, the surfaces of glaciei-s are frequently exceedingly rough and irregular. Foreign matter resting on the ice, when sufficiently thick not to be warmed through by the sun's lieat in a single day, protects the ice beneath, while adjacent surfaces not so protected are lowered by melting. Blocks of stone thus shelter the ice beneath and remain on i)illars or ped- estals as the surrounding surface is lowered. A group of such " glacier tables," as they are called, is shown on page 44. Tliese were observed by the writer on a small glacier on the High Sierra of California, and present a fair idea of the character of the mushroom-shaped prominences common on many glaciere. Glacier tables frequently incline southward in north temperate latitudes, owing to the greater melting of their sup- 1 "An Expedition to Mount St. Ellas, Alaska," National Geographic Magazine (Washington, D. C), vol. 3, pp. 127, 128. 13 GLACIERS OF NOKTU AMERICA. poitinp columns on tho Houth side. Eventually, the uprawed block slips off its pedestal in a southerly direction, leaving a stunij) of ice to mark its site. When this happens, the process is renewed and the hlock aj^ain left in relief by the meltinpf of the surrounding surface. 'J'lie boulders and stones carried on the surface of glaciei-s thus receive many falls, and Inicome broken and more or less comminuted. This illustrates the fact that not all of the crushing and commingling of rocks performed by a ghuuer takes place deep within or beneath its mass. Moraines on the surfaces of glaciiei-s are composed in a great measure of blocks of stone, whic^h protect the ice beneath, as stated above, and produce still more marked ineyramids, become detached from time to time, and descend in small avalanches to the depressions below, illustrating, again, the process of breaking and disintegration which takes pLice in the debris covering the surfaces of glaciera. While large rocks or thick masses of dirt and stones resting on ice pro- tect it from melting, the reverse is the case Avith pebbles and other small objects, particularly those of a dark color, which become Avarmed through by the sun's heat during a single day, and lead to the melting of the ice beneath. Such bodies sink into the ice and are commonly found at the bottoms of little water-filled wells five or six inches deep. On glaciers, where there is a scanty covering of pebbles, each individual stone will be found at the bottom of a water-filled depression. Sometimes the holes are so abundant that in walking over the surface one really treads 14 GLACIERS OF NORTH AMERICA. on the summits of thickly set columns of ice, separating the depressions. Leaves are frequently blown far out on glaciers, and becoming warmed by the sun sink into the ice in the same manner as the pebbles already refeiTcd to, and even insects, especially butterflies, are conspicuous in such localities. Op one occasion, when traversing an ice stream tribu- tary to Malaspina glacier, I found a fish, about four inches long, at the bottom of one of these holes. The nearest water in which it could have lived was at least twenty miles away. The most probable supposition is that it had been carried to the place where found by a bird. iijli ill Meltin§r and Drainage. — The silence on broad glaciers when the winds are still and the temperature below freezing is frequently oppressive. This is especially noticeable on summer nights, for after sunset even in summer the teiaperature falls below freezing on the surfaces of large glaciers ; but when the morning sun warms the air, rills and ri v^ulets are formed, a'.id the murmuring of running water is heard on every hand. By midday, brooks and creeks, too deep and rapid to wade and too broad to vault over, are coui'sing along In channels of ice. But their exist- ence is brief. Soon a crevasse is reached, and their floods pour down into the depths of the glacier with a deep roar, telling of caverns far below the surface. The crevasses into which surface streams find their way are frequently enlarged, and become well-like openings, or moulina, as they are termed, which are sometimes several yards in diameter, and of great depth. In many instances, these openings must penetrate to the very bottom of a glacier. When this happens, the bould'^"3 and stones that find their w. into them are washed about, and are given a rotary motion by the descending waters, so as to act as veritable mill- stones, and grind the rocks beneath. The result of this action is the formation of pits and holes in the rocks, resembling kettles, and termed pot holes, in which the stones that made them may frequently be found. These peculiar excavations are Avell known in regions of former glaci- ation. Typical examples in the Glacier garden, near Lucerne, Swit- zerland, are familiar to many. The surface melting of glaciers leads to the formation of broad, shal- low lakes. These appear especially on the neves, and by the intensity of their deep blue color impart an additional charm to the wintry scenes reflected from their surfaces. The chores of such lakos afford favorable camping places for glacier explorei-s, since water, the only necessity of camp life to be found in such regions, can there be had without the UNTKODUCTION. 15 expense of time and fuel necessary to procure it by melting snow. Many times during two expeditions conducted by the writer on the broad n6\e fields of southern Alaska, we had occasion to pitch our tent by the shores of these snow-bound Lakes, and fully appreciated the advantages they afforded. In other instances, when necessity required us to camp on greatly crevassed snow, our water supply was bometimes obtained from the crevasses by means of a bucket attached co a line. tf he water formed on the surfaceii of glaciei-s, and draining from the land surrounded by them, or lying in front and sloping to^^ irds them, finds its way into the ice and escapes by tunnels situated either at the bottom of the glacier or in the ice itself. At the ends of alpine glaciers, and about the margins of both piedmort »rd continental ice sheets, there are ice caverns from which flow turbid streams of ice-cold water. (Fig. B, Plate 17.) The archways are the mouths of tu.^ne^" into which one can sometimes penetrate for a long distance. The sti:.ams issuing from such openings are supplied by both surface and basal melting, and pos- sibly also by subglacial springs. These tunnels appear in all stages of glacier growth, and are kept open even when ice sheets reach great dimen- sions. On Malaspina glaciers, the course of such tunnels csin in some instances be followed for miles, by listening to the muflBed roar of the rivers rushing along through »oe caverns far below the surface. Some of the tunnels, through which the waters formed by the melting of glaciars escape, are known to be situated on the underlying rock, but in other instances the openings traverse the ice itself, perhaps several hundred feet above its bottom. The tunnels through the body of the ice are thought to have originated from crevo,sses which allowed the surface water to escape from one break to another, and maintain a continuous passage-way. But observations proving this to be the true explanation are wanting. In the sides cf deep crevasses in the Malaspina glacier one some- times discover a circular openiug several feet in diameter, which reveals the position of an abandoned tunnel. In traversing the extremely rough outer margin of the glacier leferred to, these openings were at times of great assistance, as they allow an explorer to pass from one deep valley in the ice to another, and thus avoid a steep climb over moraine- covered ice. The drainage of glaciers, particularly those of the piedmont and conti- nental types, is of special geological interest, for the reason that vast quantities of mud, sand, gravel, etc., are carried into the tunnels through which the sub- and engJacial streams flow, and either left on the bottoms of ^^ 16 GLACIERS OP NORTH AMERICA.. i ;i the channels, or swept out at the margins of the ice and deposited in part over the adjacent land. The sediments now forming about the border of Malaspina glacier are of great volume, and of more geological interest than even the abandoned moraines left by the slowly retreating ice mass. As will be described, thousands of acres of dense forest are there being overwhelmed and buiied by the deposits of streams, that pour out from tlie ice, heavily freighted with sediment and even sweeping along large bouldei-s. * The chief characteristic of the streams that emerge from beneath glaciers is their peculiar turbidity or milkiness. In exploring regions where the glaciers are small and hidden in sheltered recesses about high peaks, one is frequently enabled to discover them by noting the character of the waters flowing from the mountains. Upland streams not fed by melting glaciers are usually clear and sparkling, except during stoiTis, while those born in ice caverns are rendered opalescent, and have a pecu- liar greenish-yellow tint, on account of the extremely fine material sus- pended in them. This fine rock flour, as it is termed, is retcined in sus- pension even after the streams emerge from the highlands and flow through adjacent plains. Deposits of fine sediment of peculiar geological interest are formed by such streams, and enable one to interpret similar accumula- tions termed loess, left about the margins of ice sheets that have now passed away, and along the stream channels leading ^'-om them. The bluffs of fine, yellowish, clay-like material along the Mississippi and Missouri are of this character. ' , What is a Glacier? The preceding paragraphs contain, I believe, an enumeration of the principal characteristics of glaciers. Although it is diflicult, and perhaps impossible, to frame a concise definition of a glacier which will embrace all ice bodies that should be properly included, and exclude other accumu- lations of snow and ice to which the name should not be applied, 5^et it seems safe to assert that any considerable mass of snow and ice which presents a number of the characteristics referred to above may with propriety be included in the term. As a provisional definition, it may be said that a glacier is an ice body originating from the consolidation of snow in regions where secular accu- mulation exceeds melting and evaporation, i.e. above the snow line, and flowing to regions where waste exceeds supply, i.e. below the snow line. Accompanying these primary conditions are many secondary phenomena INTRODUCTION. 17 dependent upon environment, such as the grain of the ice, crevasses, melt- ing, laminations, dirt bands, moraines, glacier tables, ice pyramids, sand cones, et(f., which may or may not be present. Glaciers, even of large size, may exist in which few and perhaps none of these details can be dis- covered. We may conceive of a glacier as flowing through a channel so even and so well adjusted to its progress that no crevasses will be formed. So little debris may reach its surface that moraines and all accompanying details will be absent. The most persistent features of an ice stream are, perhaps, the slow movement or downward flow in both the neve and ice regions, the stratification of the neve, and the laminated structure and grain of the glacier proper. Yet even these important characteristics may not be readily discernible, even in ice sheets that are unques- tionably true glaciers. Although the brief definition given above may assist one in obtaining an idea of what constitutes a glacier, it is mani- festly open to qualifications and exceptions. If we consider the snow line as defining the boundary between the neve and the glacier projjcr, it is evident that there must be numerous exceptions to the rule. As before remarked, during certain yeai"s, and at times for many years in succession, the snow line is much lower than at other times, and may even completely conceal the hard ice which usually protrudes below the neve. Again, an ice stream may end in the sea, and be broken off and float away as bergs, before the division into neve and glacier proper is distinguishable on the surface. One of the most characteristic features of glaciers is their slow flowing motion, yet in their old age this may cease, so that the limits between a true ice stream and an inert ice mass may be indefinite, and perhaps impossible to define. From what has been learned concerning glaciers it is evident that they form »ne of the transition phases in the history of drainage in many regions, and that the variations they present, like genera and species in the organic kingdom, cannot be limited by hard and fast lines, but should be classified by means of comparisons with typical examples. From snow, hail, and frozen mists, usually on elevated regions, the granular ice-snow of a neve is formed. By pressure and alternate softening and re freezing the n^ve is changed into compact glacial ice, but the plane of separa- tion is indefinite, and no one can say where in a vertical section, the nev6 ends and the true glacial ice begins. Both the neve and the glacier proper are wasted hy melting when ihe temperature is above 32° of the Fahrenheit scale, and the solid drainage is transformed to a liquid co'^dition. I 18 GLACIERS OF NOUTH AMERICA. '! Ill ;'# Glacial Abrasion. ■Worn and Striated Kock Surfaces. — The movement of glacial ice causes friction and leads to the grinding, smoothing, and scratching of the rocks over which it passes. The intensity of this grinding can be appreciated to some extent by considering the force with which a thick ice mass presses on the rocks beneath. The weight of a cubic foot of ice is about fifty-seven pounds; hence a glacier 1000 feet thick, which is by no means the maximum, would exert a pressure on its bed of twenty-eight tons to the square foot. A movement of ice charged with sand and stones under such a pressure cannot fail to produce abrasion of the rocks beneath. As will be shown in a future chapter devoted to theories of glacial motion, the precise mechanics of glacial flow is not clearly understood. It is well known, however, that the ice is not forced along as a rigid body. If such were the case, the grinding would be far more intense than is now believed to occur. It is, also, known that the flow of glacial ice is at least analogous to the flow of what are commonly considered plastic solids, as pitch, for example. In an ice stream the movement is most rapid at the surface at a distance from its borders, and decreases toward the bottom and sides, where the friction is greatest. Under similar conditions the movement of clear ice is greater than when it is charged with ddbris. The study of glaciers has shown, also, that sometimes the ice is sheared, and a forward movement is accomplished by a thrust of the upper portion of the mass over the lower portion. However accomplished, the fact remains that there is frequently a movement of even the saud-charged layers at the bottom, and that friction does occur between the ice and the underlying rock. The conditions governing the flow of glaciers are so complicated that varying results are to be expected. When the bottom layer is heavily charged with debris, and, especially when containing a large proportion of gravel and stones, the friction is increased, and may possibly become so great that the bottom layer will be practically stagnant and allow the clearer ice above to flow over it ; or a shearing of the mass may result, and the lower portion remain stationary for a time, while the upper portion moves on. Probably the mo&t favorable conditions for rock abrasion are when the bottom of a glacier is lightly charged with sand, and the surface of contact with the rocks beneath is lubricated with water. That glaciers abrade the rocks over which they pass, as already til INTRODUCTION. 19 stated, there is abundant evidence. At the lower end, and along the [sides of many alpine glaciers, the ice charged with sand and stones may be seen in direct contact with the smooth, polished, and striated rock surfaces. Below glaciers that have recently retreated, and where the surface is still bare of vegetation, records similar to those jubt mentioned may be observed in thousands of localities. The same is true, also, over vast regions that are known to have been formerly glaciated ; \*hile on adjacent areas, where the c nditions are similar, excepting that they were not occupied by ice, the peculiar and not easily mistaken evidences of ice abrasion are lacking. vVe have, therefore, both positive and negative evidence pointing to the conclusion that glaciers abrade the rocks over which they flow. Smoothed and Stria teu k Surfaces not Produced by Glaciers. — There are markings that simulate glacial polishing and striation, an '. might be mistaken for them, but are produced by other agencies. River ice, especially when swept along by freshets, sometimes scratches and striates the rocky ledges with which it comes in contact, but this action is confined within narrow vertical limits, and the marks produced are by no means so regular, or so deeply engraved, as those frequently made by glaciers. The abrasion of river ice was observed by the writer under favorable conditions along the Yukon river, but it did not appear as if the smoothing and striation produced in that way, except, perhaps, when only limited exposures were observable, could be easily mistaken for the work of glaciers. The action of floe ice on the shores of lakes and northern oceans, when driven landward by wind pressure, on shelving beaches, makes the nearest approach to glacial abrasion and striation that is known. Except that the action of floe ice is confined to narrow vertical limits, it is difficult to understand how the planing and striation it produces on the rocks bene ith could, in the absence of other data, be distinguished from the work of glaciers. Glaciers smooth and striate vertical walls, Jis well as flat sur- faces, however, and make these and other records at all elevations from the surface of the sea — and to a limited extent even below sea level — up to the summits of lofty mountains. It is to be expected, also, that the records of floe ice would be accompanied by other evidence, such as deposits of clay and sand containing marine or lacustral shells, and topo- graphic features due to the abrasion and deposition produced by waves and currents. When a considerable body of evidenca is in hand in connec- 20 GLACIERS OF NORTH AMERICA. m ' tion with the abrasion of ro( k surfaces in a given locality, there usually remains no room for doubting in what way tlie planing and striation were produced. Special Features of Glaciated Surfaces. — The minor changes produced on rock surfaces by the movement of ice over th^m are so numerous that attention can only Ix- directed at this time to those that are most common and most characteristic. The details of these wonderful inscriptions can only be appreciated by studying the originals. Rock si;rfaces that have been subjected to the grinding of an ice sheet, or crossed by even a small alpine glacier, are frequently found to be worn and the angles and prominences rounded and planed away. All weathered and oxidized portions of the preglacial surface are removed, and the fresh hard ro k exhibits a polish approaching that given by marble-workers to finished monuments. The hardest and finest-grained rocks receive the most brilliant polish. Limestone, granite, and quartzite, especially, are frequently so highly burnis)ied that they glitter in the sunlight with dazzling brilliancy. On such surfaces there are usually scratches and grooves, frequently in long, parallel lines, which show the direction in which the ice moved over them. These markings vary in size from delicate, hair-like lines, such as might be made by a crystal point, to heavy grooves and gouges, a foot and sometimes several feet deep, which frequently run in one general direction for many yards and even several rods, and indicate by their straightness and evenness that the engine which made them was one of great power and m-^ved steadily in a continuous direction. In regions formerly occupied by continental glaciers, particularly, two, and possibly three, well-defined series of parallel striations are sometimes observable on the same sur- face, crossing each other at varying angles. The most probable explana- tion of these double or triple inscriptions is that the direction of the ice current varied with the growth and decline of the glacier which made them, or that the ice flowed in great swirls or eddies, as in the case of the Malaspina glacier, and that the direction of these currents changed with variations in the volume of the glacier, or perhaps with variations in the amount of ddbris in the ice. On small areas the parallel striations appear straight, but if one could examine square miles of surface it would probably be found that the lines are frequently portions of broad curves. INTRODUCTION. 21 3re usually iation were )!• changes thbin are le to those details of iclying the n ice sheet, iind to be away. All e removed, it given by lest-grained d quartzite, tter in the are usually !h show the ngs vary in y a crystal several feet many yards id evenness and m^ved ccupied by well-defined 3 same sur- )le explana- ion of the acier which s, as in the se currents irhaps with areas thr quare miles frequently Occasionally the more strongly marked glacial grooves in resistant i rocks, like hard limestone and quartzite, exhibit curved or semilunar cracks, which cross the furrows from side to side at quite uniform j intervals of a fraction of an inch up to au inch or more, and are con- jvex in the direction of the former ice movement. These "chatter marks" are thought to have been formed by pebbles that were checked in their movement by friction, and when the force became sufficient to carry them onward, were forced forward suddenly, perhaps turning over, land struck the rock with such force as to produce cmcks. A similar [action may be observed in sliding bodies, as wlien the wheels of a car [slide on the track and a jar is felt when they slip and are arrested. [These peculiar semilunar cracks are not confined to bottoms of grooves, however, but appear on flat surfaces, where they are sometimes two or three inches or more in length, and are separated by intervals fully as great. These larger cracks, or " disrupted gouges," as Chamberlin has called them, are concave toward the point of the compass from whicu [the ice came. Another characteristic feature of glaciated surfaces is observed when [hard knobs occur in rock, as, for example, when limestone is charged with small masses of chert, or with silicified shells and corals. In [such instances the hard portions are left in relief by the abrasion of the softer matrix. Starting from each elevation there are frequently [raised ridges, tapering to a point in the direction of the ice movement, land showing the manner in which the soft rock in the lee of the prom- linences was protected. On the opposite side of such knobs, i.e. on [the side from which the ice came, the rock is sometimes worn into a [furrow, which bends around the obstruction, and from its form indi- [cates that the ice behaved as a plastic body and moulded itself to the Isurface over which it flowed. Many other features of ice-worn surfaces might be enumerated, nit in an elementary introduction it is perhaps better not to burden Jthe reader with details.^ 1 In the report on "The Rock Scorings of the Great Ice Invasion," byT. C. Chamber- in, in the 7th Annual Report, U.S. Geological Survey, the reader will find many illustra- lions of ice abrasion, accompanied by clear and concise explanations of the manner of their formation, which will enable him to interpret such inscriptions for himself wherever ifound. 22 GLACIERS OF NORTH AMERICA. 'Ill fi Glacial Deposits. The morainnl material carried by glaciers either on their surfaces or within their mass, is left when they melt, and forms accumulations to which, in part, the term moraine is still applied. The characteristics of such abandoned moraines are frequently well exhibited in mountain valleys from which glaciers have recently retreated. The most common of these deposits are briefly described below. Lateral Moraines. — The debris accumulated on the borders of an ice stream, and constituting the lateral moraines of a living glacier, is left when the ice melts and appears as a ridge or terrace at varying I elevations. Steep-sided mountain valleys are frequently bordered on either side by ridges of this character, which may be situated 1000 feet or more above the bottom of the trough and clearly traceable for miles. On the precipitous sides of such valleys, above the highest of the abandoned moraines, the slopes are usually rough and irregular, and bear evidence of the work of streams and rills descending from higher elevations, as well as other results of atmospheric waste ; while below the horizon referred to the relief is subdued, and the valley has the smooth and flowing contours characteristic of ice work. Moraines of this character are frequently similar to stream terraces, but usually | have a raised outer margin, and besides are composed of angular and unassorted material. Terminal Moraines. — At various stages in the retreat of an ice stream, the lateral moraines on its sides are united by a terminal moraine, which crosses the abandoned bed of the glacier and forms a | somewhat regular and usually crescent-shaped pile of stones, gravel, and | sand, which is convex down stream and in many instances 100 feet or more in thickness. Between successive terminal moraines the bottom of the trough may be deeply filled with morainal material, deposited without special arrangement, and in many instances evidently accumulated J beneath the ice as a "ground moraine." These low spaces between well-defined terminal moraines are frequently occupied by lakes or bv | grassy meadows, and furnish some of the most charming features of mountain scenery. Morainal Embankments. — When a glacier is prolonged bey o] id ^ the entrance of a mountain valley and reaches an adjacent plain, it^P"^'*^' INTUODUCTION. 28 may expand and end in a semicircular ice foot, or preserve its stream- like form and finally melt without expanding laterally. The marked contrast in the behavior of different glaciers in this respect depends on the relative abundance of d<5bris in their lateral and in their ten:iinal moraines. When the debris on the margins of a glacier is small in volume, the ice has freedom to expand on getting Tree from the valley through which it descended, but when the margins of the prolonged stream are more heavily charged with debris than its extremity, lateral exi)ansion is checked, while the clear ice at the extremity flows on. The ice advances between the stagnant bordera of the stream to a greater or less distance, depending upon the supply from the higher mountains ; and when it retreats, the heavy lateral moraines are left as parallel ridges with steep slopes on each side. These ridges frequently resemble great railroad embankments. The best examples of structures of this character that have been described are situated at the east base of the Sierra Nevada, in Mono valley, California.^ Their general appear- ance is shown in Plate 4. Morainal embankments, like lateral moraines on the sides of a valley, may be united by terminal moraines so as to form lake basins. When the terminal moraines are composed of coai-se material and are too open to retain water, or when they have been breached by overflowing streams, grassy meadows and forest-covered parks, frequently of great ; beauty, occupy the spaces between them wliicli were formerly fiUeu by [the retreating ice stream. Frontal Moraines. — Moraines left by piedmont and continental j glaciei"s are of the same general character as those deposited by alpine glaciers, but are frequently of vast extent. The frontal moraines of continental glaciers corresponding to the terminal moraines of local ice streams, are in some instances a score or more of miles broad and not only hundreds but thousands of miles long. Where two lol)es of [a continental glacier come together *heir frontal moraines are united [and form what is known as an interlohate moraine. The best known lexaraples are in the upper Mississippi valley, and mark the junction of Ithe larger marginal extensions, or lobes, of the Pleistocene ice sheet of phat region. 1" Quaternary History of Mono Valley, California," 8th Annual Report, U. S. Geo- logical Survey, pp. 300-368, Pis. 35, 30. f _ "I^W 24 GLACIERS OP NORTH AMERICA. Till. — Besides the irregular piles and ridges of unassorted d^bns composing the moraines formed about the margins of glaciers, there are accumulations of clay, filled at times with stones and boulders, which are deposited l)eneath the ice during its advance, and fortn what are frequently termed ground moraines. This material is widely spread over formerly glaciated regions, and is now generally designated by the Scottish name till, and is less frequently spoken of as boulder clay. The term boulder clay, however, has been given a somewhat different meaning by a few authors. The characteristics of till aro its compactness, due to the pressure to which it was subjected beneath the ice, and the worn and striated condition of many of the pebbles and bouldera scattered irregularly through it. As till was not exposed to the atmosphere during its de- position, and, on account of its compactness, is impervious to surface waters, the material of which it is composed is in an unweathered condition and frequently of a bluish color, owing to the fact that the iron contained in it has not been oxidized. Its unweathered condition is in marked contrast to the surface moraines of many glaciers and to | ancient glacial deposits which have been long exposed to the atmosphere. I Drumliiis. — The abandoned paths of great glaciers are sometimes marked by smooth, oval hills that are lenticular in horizontal sections and have their longer axes parallel to the movement of the ice which formerly covered them. These peculiar and easily recognized emi- nences are, in the case of certain typical examples, about 500 feet in I least diameter, with a length of from 1500 to 2000 fee, and a maxi- mum height of from 50 to 150 feet. They exhibit many variations in tize and shape, however, some being nearly circular, mammillary hilh. and othera lenticular hills, in which the longer axis is two or three times as great as the shorter axis. In some instances they form narrow ridges several miles in length. The beautiful curves formed by their crests when seen from the side, is illustrated by the outline of a typi- ^ cal example near Groton, Mass., here presented. They occur at all elevations from s;a level, and even below that horizon, to 1500 feet or | more above tide, and are found on uneven, rocky ground as well as on smooth plains. They are composed of compact till which is frequently laminated, and seldom exhibit evidences of stratification or other wattr action. Boulders and large angular stones occur within their mass, and scattered over their surfaces. These peculiar hills, for which the Irisli ii INTRODUCTION. 25 term drumlin is now gjiiemlly adopted, have been studied especially near lioston, and occur also in many other parts of New England. They are abundant in the upper portion of the Huflson Kiver valley, in centiul New York, and have been reported from Michigan and Wis- consin. In general they are situated well within the terminal moraine which marks the southern limit of the last ice invasion of northeastern North America. Many diundins in the Connecticut and Hudson val- Pio. 2. — DRUHLnr nbab Groton, Mass. After Frvk. leys, and other similar regions, are partially or wholly buried beneath Champlain clays, which were deposited during a time of land depres- sion immediately after the last recession of the ice. Thus far, drumlins have not been observed in connection with existing glaciers. This is due, perhaps, to the fact that they are not known to originate beneath glaciers of the alpine type, and also because they seem to be a phase of the l)t'havior of the somewhat central portions of large ice sheets, and are only open to view when the ice has withdrawn. The characteristic whahhack shape of drumlins, the compactness and frequent lamination of the till composing them, as well as other facts in connection with their composition and distribution, have led to the generally adopted conclusion that they were formed beneath moving ice sheets. Various hypotheses have been proposed to explain their origin, but thus far opinion is divided in reference to the precise man- ner of their formation. ^ Without attempting to present a review of the various hypotheses that have been advanced in reference to the origin of drumlins, I venture to suggest that the effect of debris on the flow of ice enclosing it may fur- nish the desired explanation. The presence of debris, i.e. boulders, stones, sand, dirt, etc., in glacial ice, increases its resistance to motion, as will be more fully discussed in ^ A discussion of the origin of draralins, by Warren Upham, containing references to pre- vious papers on the same subject, may be found in the Proceedings of the Boston Society of Natural History, vol. 26, 1892, pp. 2-17. Y^ V.6 OLACIKlta OF NORTH AMERICA. ;i I. li ! ; advance. I)6hriH included in ic^e may Ih) said to .stiffen it and to decreiiHe its pljiHticity ; or, in other wonls, increase its reHiHtiince to forces tendinpr to shear it. With this principle in mind, we are led to conclude that if a mass of d^hris is inchuhfd in a fjfhicier, motion in the debris-charged mass will be retarded, ond the adjacent clear ice will flow around it. When the debris reaches a >;!ertain proportion, varying with conditions, motion will cease, and if the rate of flow of the clear ice does not increase, the ddbris- charged niiuss will remain stagnant. If the debris is most abundant about a central nucleus, and becomes less and less abundant in all directions from the nucleus, the flow of the ice will be least in the center, or if the debris is there suthciently abundant, will remain stagnant, while motion in adjacent portions will increase in a definite ratio until the normal flow of clear ice under given conditions is reached. If a nucleus of debris, as above postulated, is situated in the central part of a glacier, with clear ice beneath, it may behave like a boulder and be carried bodily forward ; but if situated at the bottom it will retain its position, and the clear ice will flow over it. If the ice flowing past the stagnant maas has earth and stones scattered through it, the d6bris reaching the nucleus will Ije retarded and the clear ice flow on. The nucleus of debris would thus receive additions and be compacted and moulded by the clear ice, or ice but moderately charged with foreign matter, flowing past it. A shape presenting least resistance to llie flowing ice would thus be acquired, and the longer axis of the stagnant mass would be parallel with the direction of glacial flow. Under this conception of the growth of drumlins, the fact that they frequently, and possibly normally, contain debris that has been derived from lower levels presents no difficulty, since ice under pressure behaves as a viscous fluid, and will flow in the direction of I'^^st resistance. If the resistance at the sides of a stagnant nucleus y^-kf greater than over its summit, the approaching ice would rise and ii-w over the oKstruction, carrying with it the debris contained wilhin its mass. The varying forms of drumlins, the fact that they sometin.es cover a nucleus of rock-in-place, their laminated structure, remarkable compactness, and general flowing outlines, all seem to harmo- nize with the view of their origin here suggested. Certain drumlins of what may be termed the New York type, i.e. those that are greatly elongated, are not symmetric, but their ends in the direc- tion from which the ice came which moulded them into shape are moder- ately broader and more blunt than the opposite extremities. These elon- gated hills may be said to have the shape of half a cigar cut lengthwise. INTUODUCTION. 27 il».e larger end of the cigar pointing in the direction from which the ice ciinie, which formerly covered the region where they occur. The sidcH of these hills, an in common with all elliptical or elongated drumlins, are more precipitous than the terminal .sloj)eH. On the larger or proximal end8,of Heveral cigar-Mhaped drumlins observed by the writer in Wash- ington county, New York, there is a noticeable increase in the nundn'r of l)oulders scattered over the surface, while at their tapering or distal extremities. Hue debris greatly piodominates, and is noticeable Ixjyond, where the slope of the hills is lost. In these' examples, coarae debris seems to haye Ixien deposited on the enlarged proximal ends, while the sides and distal portion suffered erosion, which removed the larger stones. Under the hypothesis here proposed, drumlins are considered to have grown by the accumulation of debris about a centnd nucleus either of solid rock or of ice charged with stones to such a degree as to increase its resistance above the shearing forces brought to bear upon it; the added material being derived from the ice which flowed past it. The location of a drumlin would be determined by the presence of debris sufficiently abundant to cause stagnation in the ice containing it, which would vary with the rate at Avhich the ice moved. When the ice contained but little debris it might all l)e carried forward ; when the debris was in excess, it might be left in a general sheet, without special form. The most favor- able conditions would be when certain threads, so to speak, of the ice current were lightly charged with debris, which on account of changes in the contour of the land over which the ice flowed, or variations in velocity due to other causes, would become sufficiently abundant at cer- tain localities to check the flow of the debris-charged ice and cause it to become stagnant. The ice current would then add fresh debris to the stagnant nucleus, and a drumlin representing the excess of deposition over erosion would result. The hypothesis outlined above has not been subjected to severe tests, and is introduced here in the hope that it v ill stimulate the student to make observations in the field, which will either sustain it or lead to its modification or rejection. In the study of the origin of topographic forms, many trial hypotheses have to be introduced and their value tested, in order to arrive at a true explanation. The above may be considered an example of such a working hypothesis. It is the duty of the compiler to take his reader as far as present knowledge seems to warrant, and to point the way into the unexplored country beyond. ^ww 28 GLACIERS OP NORTH AMERICA. I trust this little excursion beyond generally accepted conclusions will encourage the student to continue the investigation. il I Glacial SEDiMENrs. Deposits made by streams while yet confined by glacial ice, and for some distance after escaping from its borders, may for convenience be termed glacinl sediments^ in distinction from glacial deposits made directly from the ice and classified as moraines, till, drumhns, etc. These fluvio-glacial sediments are characterized by the worn and rounded condition of the aand, pebbles, and boulders composing them, and also by their moie or less perfect stratification ; while glacial deposits are, in the majority of instances, composed of unassorted, angular debris. Glacial sediments are in reality stream deposits made under peculiar conditions, determined by the presence of land ice. For this reason, they are of greatest interest when studied in connection with other glacial phenomena. The deposits here referred to are designated in many geological books, some of them of recent date, as modified drift ; the early supposition on which this term is based being that they consist of glacial deposits that have been worked over and modified by streams. The leading characteristics of some of the bestrdefined deposits made by glacial streams are briefly described below. Osars. — In formerly glaciated regions there are, in certain instances, long, gently curving, and sometimes tortuous ridges, trending with the direction of former ice movement, and composed of water-worn sand and gravel. When their internal structure is exposed, they exhibit more or less well- are barren areas in which the topographic forms peculiar to glacia! i,* re well displayed. In such instances one finds tumultuous piles of eay; " lud stones, now rising into knolls and steep-sided hills, and, again, sinking into dales and sand plains with but little variation in the surface contours. One of the most striking features in these fresh morainal deposits is the presence of many depressions without surface outlets and very frequently containing lakes. The drainage is markedly immature. On old moraine-covered areas the ruggedness is commonly concealed somewhat by vegetation, and many of the lakes that formerly existed in the depressions are transformed into bogs and grassy meadowt. Streams originating in such areas cut channels for themselves and tend still INTRODUCTION. 31 further to drain the land. As time goes on, a well-developed drainage system is established. The lakes disappear, and the work of the streams in reducing the country to base level, i.e. the level of standing water into which they discharge, is carried forward much the same as in regions that have not been affected by glacial action. This task is frequently greatly delayed, on account of the climatic conditions and for the reason, also, that glacial deposits, especially osars, kames, etc., composed of unconsoli- dated gravel and sand, are^ufficiently porous to absorb the rain water that falls upon them and allow it to percolate slowly f^way, thus robbing it of its power to erode. The most prominent relief of glaciated lands is fre- quently such 18 is produced by open, porous deposits of the nature of kames and osars. These retain their primitive form, while mountains of indurated rock yield to the forces of the atmosphere and are sculptured in various ways. The most pronounced topographic evidences of the former presence of an ice sheet are irregular moraines ; undrained basins ; numerous lakes , long, winding gravel ridges, or osars ; tumultous hills of gravel, or kames ; lenticular hills of till with smooth surfaces, or drumlins ; broad and frequently gently sloping gravel plains, sometimes with pitted surfaces ; boulders, occasionally perched on hilltops and mountain sides ; faceted and striated stones ; outcrops with smooth and rounded contoui-s, and polished and striated surfaces. With ihis elementary discussion of the general characteristics of glaciers and of the records they leave when climatic changes lead to their disappearance, we will pass in the following chapters to an account of the glaciers now in existence in North Ambrica. ; i CHAPTER II. GENERAL DISTRIBUTION OP THE GLACIERS OF NORTH AMERICA. The glaciers of North America are confined to the Cordilleran mountain series and to the Greenland region. Cordilleran Reg-ion. — The Cordilleran series is, in fact, a family of mountain systems in most of which there are several independent ranges and multitudes of individual peaks. It is the longest mountain series in the world, extending as it does from Cape Horn to the western extremity of the Aleutian islands, a distance of over 7000 miles. In Central America it is represented by a single system, in Mexico it becomes divided, and in the United States it is definitely separated into the Rocky mountains. Sierra Nevada-Cascade, and Coast systems. In Canada the breadth of the series increases northward, and four well-defined mountain systems are recognized, viz. : the Rocky, Gold, Coast, and Vancouver. What is known as the Coast range in Canada is not a continuation of the Cascade mount- ains, as sometimes stated, but is distinct from them both topographically and geologically. Vancouver system may sound strange to many readers, but is an appropriate designation, proposed by the Geological Survey of Canada, for the great system of uplifts beginning at the south in the Olympic mountains, Washington, and extending northward through Vancouver and Queen Charlo^^te islands, and attaining its greatest development on the coast in southern Alaska, and finally terminating at the west in the Aleutian islands.^ In Canada and Alaska the mountains of the Cordilleran series near the coast become more elevated than those of the interior and bend abruptly westward in the central part of their course. The eastern system in the same series is prolonged northward, and judging from the meagre information at hand, decreases in height and ends indefinitely before reaching the shores of the Arctic ocean. 1 A. R. C. Selwyn and G. M. Dawson, " Descriptive Sketch, Geological and Geographic, of the Dominion of Canada," Montreal, 1884, p. 35. DISTRIBUTION OF THE GLACIERS OF NORTH AMERICA. 83 Several of the great volcanic peaks of Mexico, which belong with the Cordilleran series but are of secondary origin, attain an elevation of from 17,000 to over 18,000 feet, a.*vl leach the horizon of perpetual snow. In some instances true glaciers of small size are ::aid to exist about their summits, but little if dny reliable information is available concerning them, however, and we are obliged to pass them by. The southern limit of glaciers in the United States is in the High Sieri-a, California, in about latitude 39°. The ice bodies of that region are small, but have many of tlie essential features of the most typical ice streams of the alpine type. They are confined to sheltered amphi- theatres about the highest peaks, and do not extend l'>wer than about 13,000 or 12,000 feet above the sea. In most instances they are at the northern base of sheltering precipices, and terminate before reaching the upper limit of timber growth. In northern California, and in Oregon and Washington, glaciers are more numerous, of greater extent, and reach lower limits than in the Sierra Nevada, but are still confined to the higher portions of the more elevated peaks and do not extend to a lower horizon than about 6000 feet above the sea. In many instances they reach the upper limit of forest growth. The best examples cluster about the summits of Mount Shasta, Mount Rainier (Tacoma), Mount Baker, and other volcanic peaks of the same region. In the Rocky mountains, glaciers are foreshadowed at the south by small snow bodies in Colorado, which certain travelers who have examined them consider worthy of being numlgred among glaciers.^ Perennial snow banks increase in number and in extent towards the north, and true glaciers occur in Montana and adjacent portions of Canada. Glaciers are numerous in the Cordilleran series in Canada and furnish some of the most attractive features in the scenery of that Wild and picturesque land, but unfortunately only meagre information concerning them is yet available. The best known examples appear in the Selkirk mountains, one of the loftiest ranges in the Gold system, and in the Coast mountains in the vicinity of the Stikine river. Further north, in the same great mountain series, bodies of perennial ice become more and more numerous, at the same time increasing in size, and reach their Geographic. 1 F. H. Chapin, "The First Ascent of a Glacier in Colorado," Appalachia, vol. 6, 1887, pp. 1-12. An account of the occurrence of typical glaciers near McDonald lake, in northern Montana, by L. W. Chaney, Jr., was published in Science, vol. 2, 1896, pp. 792-706. 84 GLACIERS OF NOlilH AMEUICA. I'^iii m most magnificent development in southern Alaska. The most thoroughly ice-covered region in the Cordiileran series is in tne vicinity of Mounts Fairweather, Logan, and St. Elias, and lies partially in Alaska and partially in Canada. Westward from that stronghold of perennial ice, as previously stated, the mountains decrease in elevation. The effec". of this change, and probably also of accompanying variations in climatic conditions, is seen in the glaciers, which become smaller and more widely separated and are confined to higher and higher regions when traced westward t > the Alaska peninsula and the Aleutian islands. As one follows the great Cordiileran glacial belt northward from its first appearance in the High Sierra, the lower limit of perennial snow, or the "snow line," at first about 12,000 feet above the sea, descends lower and lower, until finally in the vicinity of Mount St. Elias it has an elevation of only 2000 or 2500 feet. Farther west, along the curve made by the mountains about the northern shore of the Pacific, the snow line again rises, and on the Aleutian islands has an elevation of perhaps 8000 or 10,000 feet. The glacial ice everywhere extends below the limit of peren- nial, n6v6 snow, but is most thoroughly exposed in late summer or early autumn, when the true position of the snow line is sharply defined. In the High Sierra, the extension of glacial ice below the neves is but slight, and during seasons of unusual snowfall, or when the summei-s are excep- tionally cool, may not be recognizable. Proceeding northward, the ice extension is more and more pronounced, until the region of maximum glaciation is reached. Thence westward the length of the tongues of ice below the snow fields decreases. In the High Sierra, as already stated, the glaciers do not descend below about 12,000 feet ; farther north they reach lower and lower limits, until in the vicinity of Stikine river, in about latitude 67°, they gain the sea level. Thence northward and westward to beyond Mount St. Elias, a distance along the coast of between 700 and 800 miles, there are hundreds and probably thousands of glaciers that descend practically to sea level, and scores that enter the sea and, breaking off, form bergs. Beyond the Mount St. Elias region their lower limit gradually rises. At the southern end of the crescent-shaped belt of glaciere under consideration, the ice bodies are small and detached, and are sepai'ated from each other by intervening ridges and mountain peaks. Proceeding northward, they increase in area and in frequency, and unite one with another in the neve region. The snow belt broadens and finally becomes a confluent sheet 80 or 100 miles broad in southern Alaska, and narrows DISTKIBUTION OF THE GLACIEUS OF NORTH AMERICA. 35 again westward and is there broken into individual n^v^s of limited extent similar to those of the High Sierra. The most thoroughly snow and ice-cove»ed portion is in the region between Lynn canal and Cook's inlet, Alaska, where not less than 15,000 square miles of mountainous country is almost completely buried beneath a single vast nev6 field from which ice streams of the alpine type flow both north and south through rugged defiles in the flanks of the mountains. The southward flowing glaciers are larger, more numerous, and much longer than those that find their way northward, and, in gaining the low lands adjacent to the ocean, expand and unite one with another, so as to form broad plateaus of ice, known as piedmont glaciers. Could the observer obtain a bird's-eye view of the western portion of North America, he would find that the Cordillera' glaciers form an irreg- ular curve, broadest and reaching sea level in the Mount St. Elias region, and narrowing and becoming more and more elevated at lx)th its southern and western extremities. The attenuated arms of this shining crescent are broken, for the reason that only the more elevated mountains near its extremities -jach the horizon at which perennial snow exists. As in the crescent of light reflected from the surface of the moon, the mountains in the Cordilleran ice crescent where the belt is broadest are white to their bases, while only the peaks of the most lofty elevations at the extremities of the broken circle are brilliant. The length of this crescent of snow and ice is about 3000 miles. Its form is less regular, however, than the comparison made above might lead one to suppose, as its southern prolongation is broader and more broken than its central a^nd western portions. The study of the glaciers of the Cordilleras has only fairly begun, but it is hoped that what has already been accomplished will convince the reader that the subject is not only worthy of consideration, but of fascina- ting interest, and that the work of exploration should be continued. Greenland Region. — In the eastern portion of North America gla- ciere are confined to Greenland, and to the islands adjacent to it on the west. The vast ice sheet covering nearly all of Greenland is of the contin- ental type, and, as is well known, is the largest existing ice body in the northern hemisphere. Its extension northward has not been fully deter- mined, but as nearly as can be judged it terminates in about latitude 82 °. Its a,vei is in the neigLoorhood of 600,000 square miles. If transferred bodily to the eastern portion of the United States, it would WF 86 GLACIERS OF NORTH AMERICA. extend from northern Maine to Georgia, and cover a belt of country 500 miles broad. Vast as this ice 8he,.t is known to be, it takes whit- may be said to be second or third rank when contrasted with the continental glaciers that occupied Canada and a large portion of the United States in Pleistocene times. The exploration of existing glaciers derives one of its principal attractions from the fact that such studies assist in interpreting the records left by ancient glaciers in various parts of the world. This in turn brings one to the consideration of the still broader problems of the cause of climatic changes which favored the growth of vast Pleistocene glaciers in regions now enjoying a temperate climate, and inhabited by the most civilized people of the earth. The glaciers on the islands to the west of Greenland are but imper- fectly known, but from the somewhat meagre reports rendered by Arctic explorers, few of whom, it is to be regretted, have been trained observere in this direction, it appears that they are of the alpine type, although larger, and with broader neve fields in proportion to the extent of true glacial ics, than is found among the s^laciei's of Switzerland or other similar regions. A remarkable feature of the glaciers of the far north is that they frequently terminate in bold precipices of ice. Having this general sketch of the distribution of glaciers in North America in mind, the reader will be enabled to locate in the outline plan the relations of the various ice bodies described in the following chapters. CHAPTER III. GLACIERS OP THE SIERRA NEVADA. ' The Sierra Nevada, in many respects the most attractive mountain system in North America, attains its greatest elevation between hititude 30° and 38° 30', or in a more general way, between Owen's lake and Lake Tahoe, California. The High Sierra. To the more elevated portion of the Sierra Nevada the name " High Sierra " has been applied. Although the boundaries of the region thus designated are indefinite, it is well worthy of especial recognition, as it is a prominent and important topographic feature. Throughout its entire extent it bristles with rugged peaks, narrow crests, and inaccessible cliffs, overshadowing profound chasms, all of which combine to form one of the most rugged and picturesque mountain ranges in North America. The culminating point of this elevated region is near its southern limit, where Mount Whitney rises to an elevation of 14,522 feet above the sea, and is succeeded northward by Mount King, Mount Humphreys, and man}' other elevations scarcely less magnificent. Southward from Mount Whitney the Sierra declines rapidly, and the system is considered as terminating in that direction at Tehichipi pass, a little north of latitude 35°. Northward of Mount Whitney, there is a vast sea of rugged peaks and narrow moun- tain crests, separated by deep valleys, which render the region almost inac- cessible to beings not eqinpped with wings. This is the High Sierra par excellence^ as will be admitted by all who attempt to scale its giddy heights or thread its labyrinth of cations. In the neighborhood of Mono lake a number of the more prominent peaks, of which Mount Lyell, Mount Hitter, Mount Dana, and Tower peaks are examples, exceed 13,000 feet in elevation. The range retains its rugged character all the way to Sonora pass, and even to Lake Tahoe, but northward of that " Gem of the Sierra " the mountains are less elevated. 1 This account of the glaciers of the Sierra Nevada is taken almost entirely from a paper I by the present writer, on the " Existing Glaciers of the United States," 6th Annual Report U. S. Geological Survey, 1883-84. 38 GLACIERS OF NOIITH AMKUICA. vli; Very liirpo portions of tlie Higli Sierni iire c-omijosed of lightrcolored granite, but thinly flotlu'd with vegetation, whieh inii)art8 a monotonous gray tone to the rugged scenery. The peaks and crests overlo(»king Moiu* lake, however, liave been sculptured from metamorphosed sedimentary rocks, and are frequently richly tinted. The landscape in this portion of the range is warm in tone, and presents pleasing and striking contrasts ill comparison with the gray of the western slopes. Hugged and angular precipices rising to narrow crests, hut softened in contour and varied in color on their lower slopes by lichens and al[)ine llowers, dark billowy forests of pine in the valleys, snow-lillcd am[)hitheatres, and hundreds of placid lakelets and rock-rinuncd tarns are there grouped in i)i(,'tures that are as delicate in detail and as pleasing in tone iw they are majestic and far-reaching. ' ' Besides the splendor of their scenery, the mountains to the south- ward of Mono lake present the additional attraction of living glaciers. These, although small, are well worthy the careful attention of every traveler. Existing glaciers on Mount Dana and Mount Lyell were visited by Mr. (t. K. Gilbert and myself during the sununer of 1883. I also exam- ined one at the head of Parker creek, a tributary of Mono lake. Others on Mounts Conness, McClure, and Ritter were explored by Mr. W. D. Johnson, my associate for several years in western explorations, while making a topographical survey of the region draining to Mono lake. Besides the glaciers actually traversed, a number of others were seen from commanding points, and their general nature almost as thoroughly determined as if their surfaces had actually been trodden. Our combined observations show that nine glaciers exist within the southern rim of the Mono lake drainage basin. A somewhat larger number are sheltered by the mountains, of which the dominant peaks are McClure, Lyell, and Hitter. It is in ice caves beneath these glaciers that the Tuolumne, Merced, and San Joaquin rivers have their birth. The glaciers of the High Sierra are located between latitudes 36" 30' and 38°, ana at their lower extremities have an approximate elevation of 11,500 feet above the sea. The lowest seen is on the northern side of Mount Ritter, and terminates in a lakelet that is about 2000 feet below the mountain top, or about 11,000 feet above the sea. The glaciers observed are all small, the most extensive — that on the northern slope of Mount Lyell — being less than a mile in length, with a somewhat gi'eater breadth. Nearly all occur in amphitheatres on the northern side );i,AitKHi« ">K N'liHIII AMKIch.4. I'r. kTK '.'. Fig. a. — mount DANA GLACIER, CALIFORNIA. ( >ii tli<' iiortlicrn «iiU' "f the smiiiiiit-|n'iik of .Ml. I >iiiiii. Fig. B.— mount LYELL GlACIER, CALIFORNIA. The liiKhest peak is the sutnmit of Mt. Lyell. GLACIERS OF THK SIERRA NEVADA. 89 (if lofty peaks, where they are fiheltored from the iiooiulay sun hy liigh cliffs and mountain ridges; and all How northward, with the exception of a few cradled in deep cirques on the eastern side of the Minarets and Mount Hitter. So far iis known, these are the most southern glaciers in the United States. Snow fields are reported hy Mr. Johnson, however, as existing in the mountains to the south of Mount Hitter, at the head of some of the many brandies of Owen's river. If these should pn)ve to 1k3 veritable glaciers, they will extend the southern limits of the existing glaciera of this country a few miles farther southward. Mount Dana Glacier. On the western shore of Mono lake the mountains rise abruptly from the water's edge to an elevation of 5000 to 6600 feet, and have Iweii sculptured by storms and frosts into indei)endent peaks of remarkable giandeur. As seen from Mono lake, the most conspicuous point along the serrate mountain crest outlined against the western sky is Mount Dana, which rises 6600 feet abov«^ the lake, and has an elevation of 12,992 feet above the sea. Although grand proportions, this peak is but one among many prominent points crowning the divide between the drainage of Mono lake and the Pacific. From the southward, Mount Dana presents a somewhat rounded contour and is easy of ascent, but on the north its culminating cliffs form a nearly perpendicular precipice more than a thousand feet high. This northern face descends into a deep, narrow gorge leading northward, known as Glacier cafion. During the glacial epoch the whole extent of this cafion was occupied by ice, and formed a tributary to a still larger glacier flowing into Mono valley. At the head of Glacier cafion, and surrounded on nearly all sides by towering precipices, lies the small ice body represented on Fig. A, Plate 2, to which the name Mount Dana glacier has been given. The picture shows nearly the entire extent of the glacier, and is from a photograph taken on an abandoned terminal moraine now retaining a lake of opalescent water, into which the drainage from the ice discharges. In the illustra- tion the terminal moraine now forming about the border of the ice can be seen, as well as the crevasses, dirt bands, etc., that mark its surface. The glacier is about 2000 feet long in the direction of flow, but appears much foreshortened in the illustration. " Ice tongues " are seen extending uj>- ward from the neve. At the base of the largest of these peculiar ice tributaries a portion of a wide crevasse, or bergschrund, may be recognized. 40 GLACIERS OF NORTH AMERICA. Ill This miniature glacier exhibits many of the essential features of greater ice streams, such as neve and glacier proper, crevasses, dirt bands, morpines, glacier tables, etc., as will be described in connection with simi- lar features on neighboring ice bodies a few pages in advance. Mount Lyell Glacier. In traveling ^rom Mount Dana to Mount Lyell, one finds it most convenient to pass down Dana creek, which flows southward from Mount Dana, to its confluence with Tuolumne river, and then ascend the deep, broad caflon of the latter stream. Tuolumne river has its birth at the extremity of the Mount Lyell glacier. It emerges from u cavern in the ice as an insignificant, dirt-laden brook. The snowy summit of Mount Lvell, as seen from the head of Tuolumne cafion, is shown in Plate 3. The majestic mountain, when viewed from this portion of the vp.Uey, is far more beautiful than any illustration in black and while can suggest. In the soft, gray light of morning, it has all tile solemn grandeur of the Tiernese Oberland. At sunset, when flushed with the rosy light of the afterglow, this shrine of the High Sierra rivals the splendor of Mount Rosa, To the right of Mount Lyell rises Mount McClure, which is scarcely less imposing than its companion; the former attains the height of 13,420 feet above the sea, and the latter is but 150 feet less in elevation. The Tuolumne cailon, when followed still nearer its beginning, is found to lose its gentle grade and become rugged and precipitous. Its bed is crossed at jntervalt^ by irregular cliffs, that must have caused magnifi- cent ice cascades in the great glacier that once flowed over them. Tho top of each steep ascent is usually separated from the base of the next higher one by a comparatively level tract, sometimes holding a grassy meadow or small, rock-enclosed tarn. This succession of cliffs and terraces forms a grand stairway, leading to the opening of the amphi- theatre on the north side of Mount Lyell, where a magn'ficent pano- rama of the entire glacier may be obtained. The view given on Fig. E, Plate 2, is from near the outlet of the amphitheatre, and exhibits nearly the whole extent of the n6ve of the Mount Lyell glacier and ol the small area of compact ice which projects from beneatli it In the panorama the terminal moraine of dirt and stones, now forming' at the foot of the glacier, may be recognized, and also the rounded and worn rock masses that rise as islands in the central portion of the GLACIERS OF THE SIERRA NEVADA. 41 sjlacier. Crevasses, contorted dirt bands, and moraines on the ice, although noticeable features when traversing its surface, are but indif- ferently shown m the illustmtion. Parker Creek Glacier. This glacier is situated at the head of a deep, high-grade caflon, down which Parker creek descentls on its way to Mono lake. It is even smaller than the ice bodies on Mount Dana and Mount Lyell, but is yet a true glacier with a well-defined n^v6 region, from beneath which descends a mass of ice that is crossed by dirt bands and crevasses, and has many minor features that duplicate the details of more extensive ice streams. About the lower margin of the ice there are comparatively large moraines forming concentric ridges, and indicating the rapid disintegration of the surrounding cliffs, since the material of which they are composed was derived entirely from that source. The mass of debris surrounding this glacier appears to exceed the volume of the ice of which it is formed. These moraines are more characteristic examples of tho tumultuous debris piles formed by ice streUms than any other deposits of the same nature now forming in the High Sierra. Like the majority of the glaciers of this region, the one at the head of Parker creek is shel- tered by overshadowing walls, and flows northward. During the glacial epoch, the entire extent of the deep valley through which it flows was occupied by a glacier that descended upon Mono plain, and built huge morainal embankments more than a mile in length. These fine examples of the peculiar parallel embankments built by overloaded glaciera on emerging from mountain gorges are second in interest, however, to similar deposits at the mouth of the neighboring gorge, known as Bloody caflon,! ^nd illustrated on Plate 4. Characteristics of the Glaciers of the High Sierra. That the ice bodies observed in the High Sierra, although small, are yet veritable glaciers, I trust will appear from the following somewhat detailed statement of observations : 1 The instructive records left by Pleistocene glaciers in the nei{,'hborhood of Mono lake are described and illustrated in "Quaternary History of Mono Valley," in the 8th Annual Report of the U. S. Geological Survey, 1886-87, pp. 261-394. ^pp* 42 GLACIERS OF NORTH AMERICA. N^vds. — The distinction between n6v6 and true glacial ice is plainly manifest on nearly all of the glaciers of the High Sierra. This is apparent not only when viewing them from a distance, but also while traversing their surfaces. In the case of the Parker Creek glacier, especially, the change from the granular snow of the neve to the compact ice of tlie glacier proper, can be discerned within the space of a very few feet. The neves, although usually dust-covered, are invariably white as compared with the rest of the glacier, and are composed of granular ice-snow. Their surfaces are almost entirely free from stones and dirt, and are rendered very rough and uneven by crests and spires of compact snow or neve ice, from two to five feet high, that result fvom the unequal melting of the surface. These " ice blades " have been described by Professor Le Conte, who refers their origin to the unequal melting of wind-rippled snow. At their lower limits the n^v^s pass into the glaciers proper, which in part they overlie, and acquire a ribboned or laminated structure, dirt bands, etc., characteristic of true glaciers. Crevasses. — Marginal crevasses were observed in numerous instances, but they occurred in quite limited numbei-s in any individual glacier. In some examples, more especially in the neves, they are convex toward the head of the glacier, while others far down in the same series are straight, or hrtve changed their c irvature so as to be concave up stream. The cre- vasses are largest at the upper margin of the neves, and frequently corre- spond to the bergschrund of Swiss mountaineers. They vary from narrow cracks up to chasms six or eight feet wide, and frequently cross almost the entire breadth of the neve, thus rendering difficult the passage to the rocks above. The depth of the crevasses could seldom be deter- mined, as the irregularities of their sides limited the view, but some were certainly not less than 100 feet deep. The crevasses were frei{uently partially concealed* by arches of snow, hung within with vast numbers of icicles. The walls beneath these treacherous roofs are incrusted with large masses of well-formed ice crystals, with glittering faces half an inch in diameter, resembling the most beautiful transparent spar. The light in the^e fairy-like grottoes is of the most exquisite blue. Lamination, or «« Ribboned Structure." — This structure was seen in all the glaciera closely examined, but appeared most conspicuously near the lower extremity of the ice, where the layers are approximately horizontal. Hand specimens cut from the ice exhibited sections of alter- is plainly apparent ra versing ially, the le glaciei he neves, vk^ith the ? surfaces 3ry rough m two to i. These fers their whicli in ture, dirt nstances, tcier. In >ward the straight, Tho cre- tly cf)rre- n narrow is almost ;Ssage to )e deter- )me were juently miners of til large inch in light in was seen icuously ximately of alter- ■< > UJ 84 3 .a» -J 6=1 2 5 o a " I "f. o z a °= ^ - I >- u w w m n a A1 I il e; tl la A! si Vi ir 1)1 tl tl: at la cl; It fa Cf su ar( ex su or on Fc Sv thi of ha GLACIERS OF THE SIEKKA NEVADA. 43 nating narrow bands of compact blue ice and porous white ice, as plainly as could be desired. Dirt Bands. — These were observed on nearly all of the glaciere, and were frequently jnarked, and even conspicuous, features of their surfaces. It required no peculiar condition of light and shade to make them discern- ihle ; on the contrary, they could be plainly distinguished at a distance of two or three miles. Viewed from a distance, they were seen to sweep entirely across the glacier in a series of graceful curves, concave toward the neve. Sometimes this symmetry was interrupted by irregular undu- lations, or even by contortions, as may be seen in the illustnition of the Mount Lyell glacier. On Parker Creek glacier the dirt bands are about six inches broad over a considerable area, and occur at quite regular inter- vals of four to six feet, with comparativiely clear ice between. In this instance, the dirt producing the bands was not confined to the surface, but could be seen to discolor the ice in well-defined strata, dipping into the glacier at a low angle with the surface. On all of the glaciei-s examined, the dirt bands were observed only below the lower limit of the neve. In the study of the glaciers of Switzerland and Norway, particular attention has been given to the influence of ice cascades in producing lamination and dirt bands. In the Sierra Nevada glaciei-s, both of these characteristics are distinct and well marked, but ice cascades are absent. It seems evident, therefore, that the hypothesis which is apparently satis- factory in Europe does not agree so well with the phenomena observed in California. In viewing many of the Sierra Nevada glaciera at a distance of a few miles, and approximately on the same level, it is appar'^nt that their surfaces frequently have a slope of from 15 to more than 30 degrees, and are, in fact, sections of the ice bodies in which the internal structure is exposed. When seen in this manner the appearance of the glaciers is such as to lead one to suspect that the dirt bands are strata in the ice, or in reality "annual rings"' formed by yearly accumulations of dirt on the n^ves. A similar explanation was long since advanced by Forbes after studying the dirt bands of apparently the same character on Swiss glaciers. Prof. H. W. Brewer has suggested a modification in this explanation to the effect that a year of exceptional melting — one of those years in which the n6v6 is reduced to the minimum — would have the effect of combining the dirt accumulated during several years 44 GLACIERS OF NORTH AMERICA. into a single band, which would represent a climatic cycle rather than a single year. This explanation agrees best with the facts noted above. Glacier Tables. — Blocks of stone perched on columns of ice, and usually designated glacier tables, did not form a marked feature on the ice bodies of the Sierra Nevada in 1883, except in one instance. On Parker Creek glacier they were numerous and in all stages of growth and decadence. Some of the blocks of stone were poised horizontally on pedestals of ice ; others were inclined southward, or had been partially dislodged, and in some instances they had fallen and were lying on the southern side of pinnacles which had formerly supported them. Sketches of some of the more characteristic examples observed, diawn to a scale of about one foot to the inch, are here shown. Fig. 3. — Glacier Tableb, Parkeb Ckeek Glacier, California. The largest glacier table was observed near the cente/ of the Parker Creek glacier, a few hundred feet fro*^.^ its terminus. This is a block of dense volcanic rock measuring 24 X 33 X 10 feet, and was supported by a column of ice eight feet high on its northern and six feet high on its southern side, and six to eight feet thick. The smallest observed blocks that are able to protect the ice beneath sufficiently to form columns as the general surface melts away were found to be about 16x10x10 inches ; when smaller "than this they sink into the surface in a manner that is well known to all alpinists. Small pebbles are frequently seen at the bottom of little ice wells five or six inches deep, but good examples of sand cones and some of the other minor details of glacier surfaces were not observed. GLACIERS OF THE SIERRA NEVADA. 45 Ice Pyramids. — As the forms included under this name f urnisli a detail of glacier surfaces not described before the glaciers of the High Sierra were examined, I shall transcribe my notes concerning them at some length. On the lower portion of the Mount Lyell glacier, more especially than in any other observed instance, the surface .bristles, over large areas in the neve region, with acute pyramids of snow-ice from a few inches to fully tliree feet in height, with bases having a diameter of perhaps one-half tlieir height. At the base of each pyramid on its northern side, there is invariably a stone, sometimes measuring five or six inches in diameter, or a number of loose pebbles, or a handful of dirt, which is usually depressed somewhat below the general surface of the neve. The side of the pyramid rising Fio. 4. — Ice Pyramids, Mount Lyell Glacier, California. above the stone, i.e. the northern face, is usually concave, in horizontal sections, and invariably composed of clear, compact ice, while the remainder of the structure is of the ordinary porous ice forming the glacier surface. Sometimes the nearly horizonttil lamination of the glacier ice can be seen in the pyramids. A direct relation is noticeable, too, between the size and shape of the stones and the height and form of the ice pyramids rising above them. In seeking an explanation of these phenomena, the only hypothesis that seems to satisfy the observed facts, assumes that a stone or jnass of dirt lying on the surface of a glacier becomes heated and melts the porous ice beneath, and that the water thus formed freezes again into compact ice, which resists the sun's heat more thoroughly than the surrounding porous 46 GLACIEUa OF NOltTH AMEKICA. ice, and hence is left as the general surface melts away. In nearly every instance, the stone at the base of the pyramid had been carried northward as it melted its way downward, thus forming the steei), northern slope of the pyramid, and at the same time tending to prevent the formation of a prominence on the northern side of the sunken block. The pyramids alwa^'s point toward the noonday sun, hence the compact ice formed on tiie nortliern side of a pebble is more exposed than the ice on its southern side, and is« therefore, more rapitlly melted. Moraines. — No well-marked medial moraines were noticed on any of the Sierra Nevada glaciers. The reason for their absence is because the glaciei-s are simple ice streams, without tributaries. Lateral moraines resting on and inclosed in the ice at the margins of the glaciers were seen in many instances, and could be traced without difficulty to the cliffs fvom which they came. Terminal moraines, however, are common, and occur at the lower limit of every glacier observed, and owe their existence to the moderate amount of morainal material scattered over the surfaces or contained in the glaciers, without being concentrated into medial moraines. The terminals are remarkable for their size, when compared with the extent of the parent ice streams, indicating that the process now observed has been going on essentially as at present for a long term of years. The terminal moraine now forming at the lower extremity of Mount Dana glacier is approximately 1000 feet long by 30 or 40 feet broad, and api)arently 100 feet or more deep. Below this, and partially united with it, is a second ridge of debris of somewhat greater dirien- sions, which is followed by other similar crescent-shaped piles lower down the gorge. The corresponding moraines at the extremity of Mount Lyell glacier are considerably larger, as are also the still more typical terminals at the foot of the Parker Creek glacier. In some instances these moraines were coated with loose rubbish and dirt that would be swept away by a single storm, indicating that they had received their last addition within a very few months. The bottom of the Dana glacier was seen to be heavily charged with stones, pebbles, and sand, and to rest on a bed of boulders of a consider- able thickness. This subglacial deposit may with propriety be termed a ground mor9,ine. Glaciated Surfaces and Scratched Stones. — The rock surfaces in the immediate neighborhood of the Sierra Nevada glaciers are frequently OLACIEHS OF THK SIEKHA NEVADA. 47 polished and covered with grooves and scratches, bnt it is usually impos- sible to determine whether this is the work of existing ice streams, when somewhat more extended than at present, or whether it is a part of the vast glaciation imposed upon all the High Sierra during the glacial ei»()ch. ill some instances, however, there does not seem room for doubting that the markings were made during the past few years. At the inmiediate foot of Mount Dana glacier, we found a numl)er of. stones that were battered and worn and exhibited planed and scratched surfaces, in many respects similar to the glaciated stones found in the ancient moraines of New England. These occurred but a few feet from the ice foot, and their bruises and scratches are, without question, the work of the present glacier. Glacier Movements. — That the small ice bodies of the Sierra Nevada have a true glacial motion is apparent from the nature of the crevasses and the curved coui-ses of the dirt bands that cross them. Measurements of the movements of these glaciers have been made in only a few instances. The rate of the flow of the glacier on Mount McClure was determined by John Muir, who found that its maximum movement near the center was about 47 inches in 46 days (from August 21 to October 0, 1872). A more extended notice of these interesting observations is given in record- ing "previous observations" a few pages in advance. Glacier Mud. — The Tuolumne river has its source at the foot of Lyell glacier. At its birth it is a rivulet, turbid with silt ground fine by the moving ice from beneath which it issues. At the foot of the Dana g^laoier there is a small lake confined in a rock basin, which has a peculiar greenish-yellow color dlie to silt held in suspension. The water escapes from this lake through a moraine piled on the rim of the basin, and is gathered again into other depressions farther down the caflon. The watei"S are thus filtered of matter in suspension, and the lower lakes are clear and blue, like hundreds of other lakelets and tarns scattered over the surrounding glaciated area. The sediment contributed to these glacial waters is so extremely fine that it requires days and perhaps weeks to settle. Ice Tongues. — In the steep walls of the amphitheatres overlooking the n6vds of the glaciers here considered, there are frequently deep, nar- row clefts leading toward the higher peaks. In many instances they are partially filled with ice, which shoots up above the n^v^s in tapering 48 GLACIERS OF NORTH AMERICa.. tongues some hundreds of feet in height and at so steep an angle that it is impossible to ascend or descend them without cutting steps. These ice tongues are interesting features of the Sierra glaciers and are also known to occur at the heads of similar ice streams in Wyoming. One of them, in the shadow of a precipice, is shown on Fig. A, Plate 2. Whether they have glacial motion or not, has never been deter- mined. They appear to have originated from the freezing of watei-s flowing from adjacent areas, and not to have been formed entirely by the consolidation of n6\6 snows, after the manner of true glacier ice. Red Snow. — While Mr. Gilbert and myself were examining the n^ve portion of the Mount Lyell glacier, we noticed that our foot- prints in the snow had a bright pinkish tint, '.^hile the undisturbed surface appeared white or perhaps grayish white. At the lower border of the nev6 the color became more distinct and could be plainly seen in the untrodden snow, and in som? instances the borders of rills were outlined by delicate pencilings of crimson. In all cases the " red snow " was superficial, or at most only covered by a thin layer of fresh snow. Some of the coloring matter collected was examined under the microscope a number of months later and found to consist of red globules from 150 to 200 millimeters in diameter, which were determined to be the minute algae known as Protococcus. Surface Melting:* — Our examination of Mount Lyell glacier began one August morning before sunrise, when the vast amphitheatre in which the ice is cradled was hushed in the profound stillness peculiar to mountain tops. As the sun rose above the granite spires to the eastward and flushed the snow fields with a ruddy light, little rills started here and there on the glacier, gradually gathering strength as the sun's warmth increased, and by noon brooks of considerable size were rushing down channels of ice, but sooner or later they plunged into crevasses and were lost to sight. At midday the murmur of water was heard everywhere over the glacier. As the chill of evening came on the music of the streams gradually ceased, and by sunset a death- like silence reigned over the frozen region. That this noonday melting has more than counterbalanced the annual additions received during the years previous to our visit, seems evident from accounts of the former extent of the snow fields of the High Sierra. The observations bearing upon this point are given below. From GLACIERS OF THE SIERRA NEVADA. 49 all that has been learn«d concerning the fluctuations of the glaciers of Ciilifornia, it appears that like those of Switzerland, they are subject to periodic changes, due principally to climatic oscillations. Since their dis- covery they have apparently not been increasing. Pioneer Explorations in the High Sierra. Although giving precedence to my own observations in describing the gla(aei's of the High Sierra, it is not my intention to ignore the reports of those who preceded me in the same field. .rolin Muir. — An anonymous article on the " Living Glaciers of Cali- fornia," which appeared in the Overland Monthly for Decemlxjr, 1872, and now known to have been from the pen of John Muir, is, so far as I tan learn, the first announcement of the existence of glaciers on the Sierra Nevada. Mr. Muir states that in October, 1871, he was among the nionntains of the Merced group and found a living glacier, with very- recent moraines at its foot, from beneath which issued a stream of turbid w liter. Furthv'r observatio.i? revealed dirt bands, crevasses, and lateral moraines, thus leaving no doubt that the " snow bank," as it had pre- viously been considered, was an actual glacier. Other similar ice bodies were examined by Mr. Muir, on Mount Lyell and Mount McClure ; and from the- top of the former peak he saw a dozen snow and ice filled cirques on neighboring mountains. In August, 1872, Mr. Muir placed five stakes in the glacier on Mount McClure, for the purpose of demonstrating whether or not it ha