! LIBRARY UNIVERSITY OF CALIFORNIA EARTH SCIENCES LIBRARY PLATE 1. Frontispiece CHARACTERISTICS OF EXISTING GLACIERS , WILLIAM HERBERT HOBBS // PROFESSOR OF GEOLOGY IN THE UNIVERSITY OF MICHIGAN " The present is the key to the past." SIR CHARLES LYELL !Nefo gorfe THE MACMILLAN COMPANY 1911 All rights reserved COPYRIGHT, 1911, BY THE MACMILLAN COMPANY. Set up and electrotyped. Published May, 191 1. J. S. Gushing Co. Berwick & Smith Co. Norwood, Mass., U.S.A. EARTH SCIENCES LIBRARY Co PROFESSOR VICTOR GOLDSCHMIDT OF THE UNIVERSITY OF HEIDELBERG A LEADER IN SCIENTIFIC RESEARCH A GIFTED AND INSPIRING TEACHER AND A NOBLE AND GENEROUS FRIEND THIS BOOK IS AFFECTIONATELY DEDICATED BY THE AUTHOR 334627 PREFACE IT has been the common practice to treat the subject of glaciation as if all ice masses having inherent motion of whatever nature were governed by the same laws. Thus the most recent and authoritative work upon the subject has treated the glaciers of Greenland and Switzer- land together. The aim of the present w^ork has been rather to emphasize the wide differences in other than dimensional respects which separate such bodies, and to show that the laws which govern their nourishment and depletion, and their reaction with the lithosphere as well, are by no means identical. The broad line of cleavage is found to lie between those glaciers which completely cover a considerable portion of the rock surface, and have the form of a flat dome or shield, and the remaining types. These latter glaciers being all restricted to mountain districts have been desig- nated mountain glaciers, and they have been found to bear very simple relations to each other, dependent upon the measure of their nourishment and waste. Alimenta- tion being in turn dependent upon climatic conditions, all are brought in order within the cycle of changes which correspond to a period of increasingly rigorous climate followed in turn by more genial conditions the cycle of glaciation. Throughout the attempt has been to emphasize the broader physiographic elements of the problem and to show the relations to alimentation and depletion. vii viii PREFACE No attempt has here been made to set forth the views of that school of British geologists particularly which holds that the denudational effect of glacier ice is nega- tive, because it protects the basement from the process of weathering. As will appear from the text, the writer believes that protection from weathering on the cirque floor combined with effective w r eathering at the base of the cirque wall, explains the lateral migration of the glacial amphitheatre. The doctrine of protection by ice has been given so recent an exposition by an eminent prophet of this school with the expressed approval of his colleagues, that it is believed more is gained from setting forth the evidence from one's own viewpoint than by entering into controversy. Even the names "glacial protection " and " glacial erosion " as applied to the two schools to-day seem inappropriate. The materials of this volume are three papers which have been published at London, Philadelphia, and Berlin during the year 1910. The first of the series appeared in the Geographical Journal under the title " The Cycle of Mountain Glaciation." In a greatly expanded form it is Part I of the present volume. The remaining parts, though originally published in technical journals, were written with a view to their republication in book form, and have in consequence been less altered. Of these the earlier appeared in the Proceedings of the American Philo- sophical Society under the title, " Characteristics of the Inland-ice of the Arctic Regions" ; while the concluding part was published a few months later at Berlin in the international journal of glaciology bearing the title, " The Ice Masses on and about the Antarctic Continent." To the Royal Geographical Society of London, the American Philosophical Society of Philadelphia, and the editor of the Zeitschrift fur Gletscherkunde, the author is under PREFACE ix obligation for permission to republish the papers in their present form. Although they contain original material and of necessity make use of technical terms, it is thought that the language will in the main be intelligible to the general reader as well as to the specialist in glaciology. ANN ARBOR, MICHIGAN, November 2, 1910. CONTENTS INTRODUCTION PAGK The ancestry of glacial theories The factor of air temperature Mountain versus continental glaciers Low level versus high level sculpture References . 1 PART I MOUNTAIN GLACIERS CHAPTER I THE CIRQUE AND ITS RECESSION The glacial amphitheatre in literature Relation of cirque to berg- schrund The schrundline Initiation of the cirque, nivation References 12 CHAPTER II HIGH LEVEL SCULPTURING OF THE UPLAND The upland dissected Modification in the plan of the cirque as maturity is approached Grooved and fretted uplands Charac- teristic high relief forms of the fretted upland The col and its significance The advancing hemicycle References ... 25 CHAPTER III CLASSIFICATION OF GLACIERS BASED UPON COMPARATIVE ALIMENTATION Relation of glacier to its bed Ice-cap type Piedmont type Transection type Expanded-f oot type Dendritic or valley type Inherited basin type Tide-water type Radiating (Alpine) type Horseshoe type References 41 xi xii CONTENTS CHAPTER IV Low LEVEL GLACIAL SCULPTURE IN MODERATE LATITUDES PAGB The cascade stairway Mechanics of the process which produces the cascade stairway The U-shaped glacier valley The hanging side valley References ......... 59 CHAPTER V HIGH LATITUDE GLACIAL SCULPTURE Variations in glacial sculpture dependent upon latitude Surface features of Northern Lapland The flatly grooved valleys and the scattered knobs The fjords of Western Norway The rock pedestals bounded by fjords The Norwegian find References . 70 CHAPTER VI GLACIAL FEATURES DUE MAINLY TO DEPOSITION Abandoned moraines of mountain glaciers The tongue-like basin before the mountain front Border lakes Stream action on the mountain foreland The outwash apron Eskers and recessional moraines Stream action within the valley during retirement of the glacier Landslides and rock streams within the vacated valley Rock flows from abandoned cirques References . . 81 PART II ARCTIC GLACIERS CHAPTER VII THE ARCTIC GLACIER TYPE Introduction North and south polar areas contrasted The fixed areas of atmospheric depression Ice-caps of Norway Ice-caps of Iceland Ice-covered archipelago of Franz Josef Land The smaller areas of inland-ice within the Arctic regions The inland- ice of Spitzbergen The inland-ice of Grinnell, Ellesmere, and Baffin lands References 97 CHAPTER VIII PHYSIOGRAPHY OF THE CONTINENTAL GLACIER OF GREENLAND General form and outlines The ice face or front Features within the marginal zone Dimples or basins of exudation above the CONTENTS xiii PAGE marginal tongues Scape colks and surface moraines Marginal moraines Fluvio-glacial deposits References .... 119 CHAPTER IX NOURISHMENT OF THE GREENLAND INLAND-ICE Few and inexact data Snowfall in the interior of Greenland The circulation of air over the isblink Foehn winds within the coastal belt Wind transportation of snow over the desert of inland-ice Fringing glaciers formed from wind drift Nature of the sur- face snow of the inland-ice Snowdrift forms of deposition and erosion, sastrugi Source of the snow in cirrus clouds Refer- ences . . 143 CHAPTER X DEPLETION OF THE GREENLAND ICE FROM SURFACE MELTING Eastern and western slopes compared Effect of the warm season within the marginal zones of the inland-ice Differential surface melting of the ice Moats between rock and ice masses Engla- cial and subglacial drainage of the inland-ice The marginal lakes Ice dams in extraglacial drainage Submarine wells in fjord heads References 1(52 CHAPTER XI DISCHARGE OF BERGS FROM THE ICE FRONT The ice cliff at fjord heads Manner of birth of bergs from studies in Alaska Studies of bergs born of the inland-ice of Greenland References 178 PART III ANTARCTIC GLACIERS CHAPTER XII THE ANTARCTIC CONTINENT AND ITS SEA-ICE GIRDLE General uniformity of conditions in contrast with the north polar region Antarctic temperatures Geographical results of ex- ploration The submerged continental platform The zone of sea and pack ice The ice islands and ice-foot glaciers Refer- ences 186 xiv CONTENTS CHAPTER XIII THE MARGINAL SHELF ICE PAGE Its nature and distribution The " Great Ross Barrier," Victoria Land The " higher " and " lower " ice terraces off King Oscar Land The u west-ice " of Kaiser Wilhelrn Land The ice barrier tongues of Victoria Land The rectangular table berg of Antarctic waters References 214 CHAPTER XIV THE ANTARCTIC CONTINENTAL GLACIER WHERE UNCONFINED The inland-ice margin on Kaiser Wilhelm Land The blue icebergs of Antarctica Origin of the West-ice References . . . 245 CHAPTER XV THE ANTARCTIC CONTINENTAL GLACIER WHERE BEHIND A MOUNTAIN RAMPART The inland-ice of Victoria Land Marginal sections along the outlets Dimples of the ice surface above the outlets Ice aprons below outlets Moats surrounding rock masses Mountain glaciers on outer slope of the retaining ranges Ice slabs References . 253 CHAPTER XVI THE NOURISHMENT OF ANTARCTIC ICE MASSES The Greenland ice in its relation to the Antarctic continental glacier Air temperatures, humidity, and isolation Nature of the snow precipitated in Antarctica Winds upon the continental margins The Antarctic continental (glacial) anticyclone Wind direc- tion determined by snow-ice slope The southerly f oehn-blizzard of the ice plateau Wind transportation of snow High level cirrus clouds the source of the snow in the interior of Antarctica Former extent of Antarctic glaciation References. . . 261 AFTERWORD The two contrasted glacier types Physiographic form Denuding processes Alimentation Marginal contours .... 285 LIST OF PLATES 1. The Bishops Glacier in the Bishops Range of the Selkirks, with the Purity Range beyond Frontispiece FACING PAGE 2. A. Summer snow bank surrounded by a brown border of finely comminuted rock, Quadrant Mountain, Y. N. P. . . . 20 B. Snow bank lying in a depression largely of its own construc- tion, Quadrant Mountain, Y. N. P. 3. A. View of the Yoho Glacier at the head of the Yoho Valley, Canadian Rockies 26 B. Pre-glacial upland on Quadrant Mountain, invaded by the cirque known as the " Pocket " 4. Maps to illustrate progressive dissection of an upland ... 28 i. Early stage of glaciation 2. Further investment of the upland to produce a grooved upland. 3. Early maturity. 4. Complete dissection at maturity producing a fretted upland. 5. Multiple secondary cirques on the west face of the Wannehorn seen across the Great Aletsch Glacier ....... 28 6. A. a. A grooved upland in the Bighorn Mountains, Wyoming; b. A fretted upland, Alaska 30 B. Multiple cirque of the Dawson Glacier seen from the Asulkan Pass, Selkirks 7. A. Fretted upland of the Alps as seen from the summit of Mont Blanc 30 B. Map of a portion of one of the Lofoten Islands, showing a fretted surface in part submerged and emphasizing the approximate accordance of summit levels 8. A karling in North Wales 32 9. A. The Matterhorn from the Gorner Grat, near the Riffelhorn . 34 B. Col of the Overlook looking across the foot of the Illecillewaet Glacier, Selkirks 10. A. Expanded forefoot of the Foster Glacier, Alaska ... 44 B. Type of piedmont glacier 11. Types of mountain glaciers ........ 48 12. A hanging glacieret, the Triest Glacier above the Great Aletsch Glacier of Switzerland . 50 13. A. A hanging tributary valley meeting a trunk glacier valley above the present water level on the " inside passage " to Alaska . . .52 B. Irregularly bounded nves upon the volcanic cone of Mt. Ranier xvi LIST OF PLATES PLATE FACING PAGK 14. A. Series of hanging glacierets which extend the Asulkan Glacier in the Selkirks 54 B. View of the Wenkchemna Glacier in the Canadian Rockies 15. Surface moulded by mountain glaciers near the ancient Lake Mono in the Sierra Nevadas of California 60 16. A. The Little Cottonwood Canyon in the Wasatch Range trans- formed at the bottom into the characteristic U -section . 64 B. Striated surface of glaciated valley floor near Loch Coriusk, Skye 17. A. The Hardangerjb'kull and the Kongsnut nunatak ... 76 B. Upland glaciated by mountain glaciers and partially sub- merged through depression 18. A. Development of tinds on the margin of the Jostedalsbraen . 78 B. Typical tinds on the margin of a fjord 19. A. Rock stream in a cirque of Greenhalgh Mountain, Silverton quadrangle, Colorado 96 B. Rock stream at head of a cirque, in the silver basin, Silver- ton quadrangle, Colorado 20. Map of a portion of the Jostedalsbraen ...... 102 21. Map of the margin of an Icelandic ice-cap 104 22. A. Fretted upland carved by mountain glaciers about King Oscar's Fjord, Eastern Greenland 124 B. Front of the Bryant glacier tongue, showing the vertical wall and the stratification of the ice 23. A. Portion of the southeast face of the Tuktoo glacier tongue, showing the projection of the upper layers apparently as a result of overthrust 128 B. Ice face at eastern margin of the inland-ice of Greenland in latitude 77 30' N. 24. A. Normal slope of the inland-ice at the land margin near the Cornell tongue 130 B. Hummocky moraine on the margin of the Cornell glacier tongue 25. A. Lateral glacial stream flowing between ice and rock, Benedict glacier tongue, Greenland ....... 170 B. The ice-dammed Lake Argentine in Patagonia 26. A. Ice-dammed lakes on the margin of the Cornell tongue of the inland-ice .......... 174 B. Delta in one of the marginal lakes of the Cornell glacier tongue 27. A. The fringing glaciers about Sturge Island, Balleny Group . 208 B. An ice-foot, with boat party landing 28. A. The ice-sheathed Bouvet Island, latitude 54 26' S., longitude 3 24' E. (after Chun) 208 B. Neve stratification in ice island (after Arctowski) LIST OF PLATES Xv ii PLATE FACING PAGE 29. A. The margin of the Great Ross Barrier 216 B. Near view of the Great Ross Barrier where highest 280 feet 30. A. Surface of the great shelf ice to the south of Minna Bluff . 220 B. Surface of the great shelf ice viewed from a balloon and show- ing sastrugi 31. A. A new ice-face on the Great Barrier ...... 222 B. An old ice-face on the Great Barrier 32. View of the inland-ice of Kaiser Wilhelm Land from the top of the Gaussberg 246 33. A. View of the Gaussberg surrounded by inland-ice in a depressed zone 258 B. Moat surrounding rock which projects from the ice surface 34. A. View of the high surfaces of the Jotemheim from the Galdha, Norway (after Fritz Machacek) 286 B. The Maelkevoldsbrae of the Jostef jeld, showing the develop- ment of tinds about the borders of a Norwegian plateau glacier (after Fritz Machacek) ILLUSTRATIONS IN THE TEXT FIG. 1. Ideal section across inland-ice ........ 7 2. Section across a mountain upland occupied by glaciers ... 7 3. View/of the ice-cap of the Eyriksjokull, Iceland .... 7 4. A glacial cirque excavated from the Pleistocene glaciated surface of Norway . . . . . . . . . .14 5. Bergschruud below cirque wall on a glacier of the Sierra Neyadas, California ........... 16 6. Schrundline near Mt. McClure, Sierra Nevadas of California . 18 7. Cross-section of a steep snowdrift site, showing recession by niva- tion ............ 19 8. Characteristic form of drift sites on hillsides in Swedish Lapland . 21 9. Pre-glacial upland invaded by cirques, " biscuit cutting " effect, Bighorn Mountains ......... 26 10. View of the scalloped tableland within the Uinta Range . . 27 11. Map of Quadrant Mountain, a remnant of the pre-glacial upland on the flanks of the Gallatin Range, Y. N. P ..... 27 12. Series of semicircular glacial amphitheatres whose scalloped crest forms part of the divide of the North American continent . 28 13. Diagram to illustrate the manner of dissection of an upland by mountain glaciers . . . . . . . . .31 14. Position of the Aletschhorn and Dreieckhorn between the Upper, Middle, and Great Aletsch neves ....... 33 15. Illustration of the formation of cols through the intersection of cirques ............ 34 16. Map of a transection glacier ........ 45 17. The Baird glacier, a typical expanded-foot glacier . . .46 18. Outline map of the Hi spar glacier, Himalayas . . . .47 19. Outline map of the Tasman glacier, New Zealand . . 48 20. Outline map of an inherited basin glacier ..... 49 21. Outline map of a reconstructed glacier ...... 50 22. Outline plan of a radiating glacier ....... 53 23. Outline map of the Asulkan Glacier in the Selkirks ... 54 24. Outline map of the Wenkchemna Glacier in the Canadian Rockies 55 25. Longitudinal section along a glaciated mountain valley, showing reverse grades and rock basin lakes in series .... 60 26. Rock bar with basin showing above ...... 62 27. Ideal cross-section of a U-shaped valley once occupied by a moun- tain glacier . . . . . . . . . . .64 xix XX ILLUSTRATIONS IN THE TEXT FIG. 28. View in the glaciated Sierra Nevadas of California, showing the sharp line which sometimes separates the zone of erosion from that of sapping 65 29. Normal valleys from sub-aerial erosion 66 30. Glaciated and non-glaciated valleys tributary to a glaciated main valley hanging valleys . . ... .07 31. Comparison of the longitudinal profile of a mature stream-cut valley and its tributaries with a glacier-carved Alpine valley and its tributaries . ., . t . v : . . . 68 32. Surface in Swedish Lapland moulded by continental glaciers and subsequently grooved by sluggish mountain glaciers ... 71 33. Map of area in Swedish Lapland, showing cirques and kar- lings . . . . . ... . ; 72 34. Map of area in Swedish Lapland moulded by sluggish glaciers which succeeded continental glaciation . . . . . 73 35. Characteristic features due to glacial sculpture in Scandinavia . 74 36. Map of the vicinity of the Storf jord, showing the regular arrange- ment of fjords and submerged valleys . . . . 75 36 a. Nunataks rising out of the surface of a Norwegian ice-cap near its margin . . . . . . . . .76 37. Erosional surface due to ice-cap glaciation within the marginal zone . . . . . . . ...... 76 38. The Seven Sisters, sharpened ice-cap nunataks in Northwestern Norway due to overflow of glacier streams at margins /. . 77 39. Broad glacial trough overdeepened through uplift and subsequent glaciation .... . .77 40. Circular tind with acute apex from the Lofoten Islands . . 78 41. Successive diagrams to illustrate a theory of the shaping of acute circular tinds through exfoliation 79 42. Terminal and lateral moraines remaining from earlier mountain glaciers . . . . . *. . . . .81 43. Sketch map of the morainic ridges near the mouth of Little Cot- tonwood Canyon in the Wasatch Range 82 44. Convict Lake, a lake behind a morainal dam in a glaciated valley of the Sierra Nevadas of California 82 45. Map of the moraines and drurnlins within and about the apron of the piedmont glacier of the Upper Rhine . . . . . 83 46. Lake Garda in the southern gateway to the Alpine highland on the apron site of the earlier piedmont glacier . . ... 84 47. Outline map of the northern border of the Alps, showing the basins of former lakes 85 48. A braided stream flowing from the margin of a glacier ... 86 49. Ideal form of tongue-like basin remaining on the site of the apron of a piedmont glacier 88 50. Gorge of the Albula river near Berkun in the Engadine . . 90 ILLUSTRATIONS IN THE TEXT xxi FTG. 51. Ideal section showing successive slides from a canyon wall so as to produce a staircase effect ........ 92 52. View of the succession of rock slides from the north rock wall of the Upper Rhine near the town of Flims ..... 93 53. Map of two high glacial cirques now partially occupied by rock streams ............ 95 54. Map showing the areas of fixed low barometric pressure and of heavy glaciation in the Northern Hemisphere .... 100 55. Idealized section showing the form of "fjeld" and "brae" in Norwegian ice-cap ......... 101 56. Maps of the Hofs Jokull and the Lang Jokull . . . .102 57. Map of the Vatna Jokull ......... 103 58. Cross-section of the Vatna Jokull from north to south . . . 104 59. Map of the ice-capped islands in the eastern part of the Franz Josef Archipelago ......... 107 60. Typical ice cliff of the coast of Prince Rudolph Island, Franz Josef Land ............ 108 61. Map of Nova Zembla, showing the supposed area covered by inland-ice ........... 109 62. Map of Spitzbergen, showing the supposed glacier areas . .110 63. Inland-ice of New Friesland as viewed from Hinloopen Strait . Ill 64. Map of the southwestern margin of an extension of the inland- ice of New Friesland ......... 112 65. Camping place in one of the "canals" upon the surface of the inland-ice of North East Land ....... 114 66. Hypothetical cross-section of a glacial canal upon the inland-ice of North East Land ......... 115 67. Map showing the supposed area of inland-ice upon Grinnell and Ellesmere Lands ... ..... 115 68. View of the "Chinese Wall" on Grinnell Land . . . .116 69. Map showing the supposed area of inland-ice upon Baffin Land . 11? 70. Map of Greenland, showing the outlines of the inland-ice and the routes of explorers . . . . . . . .120 71. Route of Garde across the margin of the inland-ice of South Greenland ........... 121 72. Sketch of the east coast of Greenland, showing the inland-ice and the work of marginal mountain glaciers ..... 122 73. Section across the inland-ice of Greenland near the 64th parallel of latitude ........... 122 74. Comparison of the several profiles across the margin of the inland- ice of Greenland . ....... 123 75. Map of the region about King Oscar's and Kaiser Franz Josef Fjords, eastern Greenland ........ 124 76. Map of a glacier tongue which extends from the inland-dee of Greenland down the Umanak Fjord .... 125 xxii ILLUSTRATIONS IN THE TEXT FIG. PAGE 77. Tongues of ice which descend from the Foetal glacier . . . 126 78. Map of the Greenland shore in the vicinity of the Northeast Foreland 127 79. A series of parallel crevasses on the inland-ice of South Green- land 129 80. Rectangular network of crevasses on the surface of the inland- ice of South Greenland 130 81. Map showing routes of sledge journeys in North Greenland . 133 82. a. Closure of the Neu-Haufen Dyke, Schiittau ; b. Scape colks near Dalager's Nunataks ........ 136 83. Diagram to show the effect of a basal obstruction in the path of the ice near its margin 139 84. Surface marginal moraines of the inland-ice of Greenland . . 139 85. Diagram to illustrate the air circulation over the isblink of Greenland ........... 147 86. On the Sahara of snow ......... 151 87. Sastrugi on the inland-ice of North Greenland .... 155 88. Barchans in snow 156 89. Diagrams showing the distribution of temperatures within the surface zones of the inland-ice . . . . . . .164 90. Map showing the superglacial streams within the marginal zone of the inland-ice 165 91. Diagrams to show the effects on differential melting on the ice surface '. 166 92. Fragments of rock of different sizes to show their effect upon melting ........... 167 93. Section showing the so-called " cryoconite holes " upon the surface of an ice hummock 168 94. Map showing the margin of the Frederikshaab ice apron extend- ing from the inland-ice of Greenland, and showing the position of ice-dammed marginal lakes ....... 171 95. Diagram showing arrangement of shore lines from marginal lakes to the northward of the Frederikshaab ice tongue if its front should be retired ......... 172 96. Sections from the inland-ice through the Great and Little Kara- jak tongues to the Karajak Fjord 179 97. Origin of bergs as a result especially of wave erosion . . .180 98. Supposed successive forms of a tide-water glacier front . .181 99. Large berg floating in Melville Bay and surrounded by sea-ice . 182 100. Map of Antarctica, showing the principal points which have been reached by exploring expeditions .194 101. Map of the Antarctic region, giving the tracks of vessels and the margins of the continent , 195 102. Soundings over the continental platform to the westward of West Antarctica . . . ... v 197 ILLUSTRATIONS IN THE TEXT xxiii r &wi 103. Cracks formed on the free surface of an elastic block when crushed in a testing machine 201 104. Open lane of water within the Antarctic pack-ice, showing the minor elements of similar form which by separating yield * 909 zigzag margins ..... ^ u ^ 105. Lozenge-shaped lakes within the Antarctic pack arranged en echelon ....... 20- 106. Sastrugi on pack-ice off Kaiser Wilhelm Land as seen from a balloon 204 107. Pressure lines upon the surface of sea-ice 204 108. Pressure ridge formed on the shore of Victoria Land . . . 205 109. The Antarctica sinking after being crushed in the pack . . 205 110. Domed ice island off King Edward Land . . . . . . 209 111. King Edward Land with ice shelf in front 215 112. View of the shelf-ice of Coats Land 216 113. Map of the Ross Barrier edge 217 114. Section along the Ross Barrier edge, showing submerged portion and the underlying water layer 217 115. a. Low margin of Ross Barrier on Balloon Inlet ; b. Relatively high margin of the Barrier on Balloon Inlet .... 219 116. Outline map of the known portions of the Great Ross Barrier . 220 117. Map of the shelf -ice near King Oscar Land 225 118. West-ice seen from the " Gauss " off Kaiser Wilhelm Land . 228 119. Junction of the " West-ice " and the " sea-ice " 228 120. Diagram showing manner of formation of " West-ice " mass . 230 121. Map of the glaciers and shelf-ice tongues about the head of Robertson Bay, Victoria Land 230 122. Map showing the shelf-ice tongues on the west of Ross Sea with the glacier outlets above them 232 123. Ideal section through a shelf -ice tongue 233 124. The ice barrier breaking away to form a tabular and rectangular berg 235 125. Rectangular and tabular berg of Antarctic waters . . . 236 126. Tabular Antarctic iceberg, showing perpendicular and rectangu- lar jointing 236 127. View of a tilted tabular berg, showing the rectangular lines in the plan 237 128. The inland-ice of Kaiser Wilhelm Land seen from the sea . . 246 129. Intersecting series of fissures in the surface of the inland-ice of Kaiser Wilhelm Land 247 130. Section across the margin of the inland-ice of Victoria Land to the westward of McMurdo Sound 253 131. a, b. Section across the Great Ross Barrier and up the Beardmore Outlet to the ice plateau ; c. Section across the Drygalski ice- barrier tongue and up the Backstairs Passage to the inland-ice 254 xxiv ILLUSTRATIONS IN THE TEXT 132. A comparison of sections across the margin of the Greenland and Antarctic continental glaciers ...... 255 133. View from above the Ferrar Outlet, showing the dip of the sur- face from indraught of the ice ....... 256 134. Map of the Beardmore Outlet 258 135. Map showing sastrugi on David's route to the south magnetic pole 267 136. Lee side of a sand dune, showing curve of profile . , '..*' . 273 137. Profile across the ice-cap of the Vatna Jokuli .... 274 138. Section of one of the irregular ice grains enveloped in water which was precipitated together with snowflakes upon inland- ice of Northeast Land .. .. .. . 277 139. Sketch map showing glaciated and higher non-glaciated surfaces of the rock masses which protrude through the ice in the vicinity of McMurdo Sound 279 140. Diagram to illustrate the growth of an inland-ice mass through the rhythmic action of the anti-cyclonic air-engine . . . 288 CHARACTEEISTICS OF EXISTING GLACIERS CHARACTERISTICS OF EXISTING GLACIERS INTRODUCTION The Ancestry of Glacial Theories. If we are to gauge the generally accepted hypotheses of any science and arrive at individual conclusions respecting their value, we must be prepared to inquire into the ancestry of each we must trace out the route by which each has come to its present position of eminence. It is a Scriptural saying that " we see through a glass darkly ," and scientific reasoning, we know, makes a demand upon the imagination. To a solid basis of observation, which at best but half discloses the truth, inductive reasoning is to be added if science is to advance. Psychological processes and the tendencies of scientific thought are thus to be well considered by the more thought- ful student of science in forming his opinions. Experience has shown that whenever a new and more advanced view- point has been gained to take the place of an earlier one, and its superiority has come to be acknowledged, the ten- dency has always been to sketch in from that one standpoint even the more distant objects, rather than to move forward to new and independent positions. This has been no less true of glacier study than of the broader divisions of science. This general fact is, perhaps, in part to be explained by the optimism inherent in human nature; but account must also be taken of the authority of a great name in science. 2 CHARACTERISTICS OF EXISTING GLACIERS With the multiplication of workers which is characteristic of present-day science, the number of authorities increases and the servile attitude within the profession toward its great leaders will gradually disappear. The student of geology would, however, do well to take note of the early dominant influence of Werner or von Buch in Germany, of de Beaumont in France, of Murchison in England, or of Agassiz, the " Pope of American Science." It is a truism that the influence of things seen is more potent than that of things merely heard of or read about. The unconscious effect of the immediate environment, of oft present scenes, in directing the trend of thought, and of determining convictions, is an unwritten chapter in the philosophy of science. It would be easy to show how all the accepted views of geological processes would have been different had the seats of learning been located either in the tropics or in polar, rather than temperate, latitudes. More- over, it has not always been easy to say what observed phe- nomena are of general and what are of only local importance. Environment is, therefore, of the utmost importance in the evolution of the " body of doctrine " of any science. To apply these considerations to glacial theories, we find that whereas existing glaciers are found in all latitudes, but with the largest and most important types in polar and sub-polar regions; the earliest and by far the largest number of studies have been made in the Alps, where a single type of small glacier is found. The reason is not far to seek. The Alps have now for a good many years been the play- ground of Europe easily reached and explored by her scien- tific men. Until the close of the eighteenth century there existed a popular belief that the mountain highlands were bewitched. The Alps were the montagnes maudits and in consequence a terra incognita. It was de Saussure who both by precept INTRODUCTION 3 and example as well as by offering a generous prize, stimu- lated interest in exploring the Alps and thus dispelled the illusions which had so long clung to them. We may here pass over his scientific conclusions, as we may over those of Scheuchzer, Hugi, Venetz, and other early workers, impor- tant as they were; for it was not until the early forties of the nineteenth century when Agassiz l and Charpentier 2 published their important monographs upon the physiog- raphy, the structure, the mechanical work, and the former extensions of the Alpine glaciers, that a lively interest was excited in them. This sudden interest in glaciers on the part of geologists arose, not so much because of an interest in the Alpine glaciers themselves, as for the reason that on the basis of these studies Agassiz soon founded his theory of the ice age, and was thus for the first time able satisfactorily to explain the origin of the erratic blocks which are found strewn over the Alpine foreland, the North German plain, the British Isles, and Northern North America. The great continental glaciers which he thus hypothecated were from a thousand to a millionfold greater than those ice masses which had been seen and studied, from which ice masses they must have differed most widely. This is particularly true, as we now know, as concerns their physiographic development and their alimentation. No continental glaciers being then known, it was but natural that the attributes of Alpine glaciers should have been carried over to the continental type thus reconstructed in imagination upon the basis merely of its carvings, its gravings, and its deposits. It is one of the strange coincidences of science that almost at the moment when the epoch-making studies of Agassiz were being made upon Swiss glaciers, three great scientific explor- ing expeditions were independently discovering the greatest of existing continental glaciers, that of Antarctica, but with- 4 CHARACTERISTICS OF EXISTING GLACIERS out being able to set foot upon it or to learn aught of its characters. Thus it happened that the views concerning continental glaciers took shape before any had been visited, and one result is that even to-day in university and college texts we find the attributes of continental, Alpine, and other glacier types classified together as though all were necessarily identical in origin. The first attempt to arrive at observational knowledge of " inland-ice " was the expedition of Otto Torell to Spitz- bergen in 1858. It was the unsuccess of the Swedish polar expedition of 1872-1873 which made the journey by Norden- skiold and Palander across Northeast Land (Spitzbergen) the first successful, comprehensive attempt to observe any considerable area of inland-ice. It will, however, hardly be claimed that the results of this expedition are well known, or that they have in any important way influenced glacial theories. The later discoveries of Nordenskiold, Nansen, and above all Peary on the great continental glacier of Greenland, rich as they are in results, are, moreover, not as well known as they should be, and are only beginning to modify the views held concerning continental glaciers. In fact, it is only toward the beginning of the twentieth century that former continental glaciers have begun to be studied on the basis of any other model than the Alps. The Factor of Air Temperature. With the advance of knowledge concerning the sequence of conditions affecting glaciers, it has come to be quite generally recognized that for any given district the factor of supreme importance in initiating glaciation is temperature; a very moderate change in the average annual temperature being sufficient to trans- form a district, the aspect of which is temperate, and to furnish it with snow-fields and mountain glaciers. Thus it has recently been estimated that a fall of but 3 F. in the average annual temperature of Scotland would result in the INTRODUCTION 5 formation of small glaciers within the area of the Western Highlands, while a like fall of 12 F. within the Laurentian Lake district of North America would be sufficient to bring on a period of glaciation. It is further of interest that such temperature changes affect the distribution of air pressure over the continents and in this or in other ways directly modify the precipitation of moisture. Statistics have shown that cold periods corre- spond to high precipitation and warm periods to smaller falls of snow and rain. 3 It is further found that the larger cli- matic changes are common to very large areas of the earth 4 and are probably world wide in their extent. 5 In climates such as now prevail on the borders of Ant- arctica, it is true that most of the snow falls in the warmer season. Gourdon has apparently been misled by this into believing that warm rather than cold climates promote glaciation. 6 As we shall see, glaciers are under these condi- tions nourished by a different process, which is in a large measure independent of local evaporation. With the probability that such progressive climatic changes would be initiated slowly, 7 the first visual evidence of the changing condition within all districts of accentuated relief would probably be a longer persistence of winter snows in the more elevated tracts; which accumulation of snow would eventually contribute a remnant to those of the suc- ceeding winters, and so bring on a period of glaciation. Such a change of air temperatures with resultant changes in snow precipitation may be otherwise expressed as a depression of the snow-line of the district. All are familiar with the fact that as we ascend in the atmosphere we pass into succes- sively colder strata. Mountains which even in tropical regions push up their heads to great altitudes, are in conse- quence capped with snow throughout the year. The snow- line is the lower limit of this " perpetual " snow, and it is 6 CHARACTERISTICS OF EXISTING GLACIERS evident that any refrigeration of the atmosphere will cause the line to descend toward the lower levels. 8 From this beginning the process is an advancing one until a culmination of glaciation is attained corresponding to the most rigorous of the climatic conditions. A resumption of a more genial climate would bring about a reverse series of changes, a waning of the glaciers setting in so soon as the winter's fall of snow is insufficient to contribute a remnant to succeeding seasons. It is, therefore, proper to speak of advancing and receding hemicycles of glaciation. 8o This use of the expression cycle of glaciation carries with it no idea of lapse of time except such as is implied in the completion of a progressive series of climatic changes, and a return to the initial condition. In any given district the time may have been insufficient to accomplish the complete normal series of denudational results indicated in neighboring districts which were more favored in respect to glacier nour- ishment. The term " cycle of glaciation " is, therefore, not the equivalent of " glacial cycle " used by Professor Davis, 9 since in our use the cycle is measured in climatic changes rather than in the attainment of certain denudational effects within the glaciated valleys. Russell's earlier discus- sion of the " Life History of a Glacier " 10 takes account of this alternation of sequential climatic changes a climatic episode with resultant changes in the size and physio- graphic forms of glaciers. Mountain versus Continental Glaciers. Those glaciers which are developed in mountain districts differ from the ice masses of the interiors of continents or islands in several important particulars. As respects their physiographic forms, they are as different as possible. 11 Inland-ice assumes a form the visible surface of which is largely independent of the basement upon which it rests, while there is no definite model to which the glaciers of mountains conform, they INTRODUCTION 7 being moulded with reference to the irregularities of their beds. It is characteristic of inland-ice that no portion of the lithosphere is exposed above its higher levels. The glaciers of mountains, on the contrary, always have rock exposed above FIG. 1. Ideal section across inland-ice. their highest levels. The physiographic form assumed by inland-ice is invariably that of a flat dome or shield, and all visible projections of the lithosphere within the area of the ice are restricted to the marginal zone (see Fig. 1). The glaciers of mountains, as already stated, conform to no definite model, and rock projections may appear at any level, but are always to be seen above the highest levels (see Fig. 2 and pi. 1). FIG. 2. Section across a mountain upland occupied by glaciers with the glaciers in black (after Hess). The unique exception to this law is the small ice-cap or plat- eau glacier which is transitional between inland-ice and mountain glaciers (see Fig. 3). In size more nearly allied FIG. 3. View of the ice-cap of the Eyriksjokull, Iceland, seen from the West (after Grossman 12 ). to the glaciers of mountains, in form the ice-cap resembles the masses of inland-ice it is developed as a flat dome or g CHARACTERISTICS OF EXISTING GLACIERS shield. As regards the processes by which they are nour- ished, ice-caps are, however, as will be seen, quite different from true inland-ice; and they should in consequence be considered separately and in order between the others, so as to call attention to their intermediate position. Their size is usually a direct consequence of the limitations of the circumscribed area of the rock platform upon which they rest usually either a small island or a limited portion of a high plain or plateau. The regular surface form common to inland-ice and ice-caps is due to the fact that the irregularities of the base are small when compared with the dimensions of the ice mass. The ice-caps of Norway or Iceland have in common with the glaciers of mountains, a considerable elevation above the sea, but the variations of their base from a horizontal plane are small by comparison with the other dimensions. Curiously enough there is to this rule a single exception, and here it is not the flatness of the base but the precipitousness of platform slope which is the determining factor. This special case is of ice-caps on the high volcanic peaks of low latitudes, which on excessively steep slopes push their summits far into the upper atmospheric strata. Low Level versus High Level Sculpture. In part the failure to note the essential difference between mountain glaciers and inland-ice is due to the peculiar evolution of glacier studies which has been outlined in the introduction, but in part it is to be explained by a rather general tendency to treat the subject of erosion by glaciers in mountains from studies made especially in the lower altitudes. 13 A quite general neglect of those special conditions of denudation which are operative in high-level areas of glaciers is, it is believed, responsible for an over-emphasis laid upon the U-shaped trunk valley and the hanging tributary valley, important as these features are. 14 This over-emphasis can, perhaps, be best illustrated by reference to a series of three INTRODUCTION ! 9 successive idealistic sketches, executed with great skill by an eminent American geographer, and intended to develop especially the erosion forms which result from mountain glaciers. 15 The low-level sculpturing expressed by these sketches is, in the opinion of the writer admirable and a true rendering of nature. It is the failure to recognize any additional process of erosion operative in higher altitudes which destroys the value of the high-level sculpturing dis- played. So far as low-level mountain glaciation is concerned, the erosive processes are pretty well understood to be identical with those of continental glaciers, namely, abrasion and plucking. The former process is a wearing away of the rock surface which is in every way analogous to the abrasion of a facet upon a gem by a lapidary, the stones frozen into the mass of the ice corresponding to the diamond dust imbedded in the lap. The product of glacial abrasion is rock flour. The plucking process, on the other hand, is a removal of the rock in larger masses aided often by the fracture planes already present, which so often bound the dislodged masses. In parts of a glacier bed recently uncovered near the glacier foot, the dislodged blacks may sometimes be fitted into the rock floor from which they have been extracted. 16 With respect to the direction of movement of the ice, abrasion is particularly developed on obstructing rock masses on the side from which the ice comes stoss side, and plucking upon the side away from which it moves the lee side. The two sides of an obstruction in the bed have therefore been called the " scour " side and the " pluck" side. 17 The plucking process is no doubt in some cases much facilitated by a ready separation of the rock along planes parallel to the surface, these planes being due to the strains set up in the rock parallel to its free surface. To these processes of abrasion and plucking there is in the 10 CHARACTERISTICS OF EXISTING GLACIERS case of mountain glaciers a third important denuding process which may locally be more important than both the others acting together. It is this process of head-wall erosion which as regards reaction with the lithosphere differentiates all types of mountain glaciers from continental ones. This distinguishing process is responsible for the development of the cirque (Ger. cirkus), which is known by a variety of names in different glacier districts. In Scotland it has been generally referred to as the come, in Wales as the cwnij and in Scandinavia as the botn or kjedel (kessel). In the scientific literature of the subject the Bavarian- Austrian word "kahr" has been used with increasing frequency for the same topographic feature. In view of this diversity in resultant topography, and despite their close genetic relationships, we would do well to sharply separate in our discussions continental glaciers from the other types, which latter we may include under the broad term of " mountain glaciers." REFERENCES 1 L. Agassiz, "Etudes sur les glaciers," Neuchatel, 1840, pp. 1-346. Accompanied by an atlas of 32 plates. An even more comprehensive monograph Agassiz published in 1847 under the title, "Nouvelles etudes et experiences sur les glaciers actuels, leur structure, leur progression, et leur action physique sur le sol," Paris, 1847, pp. 1-598. With an atlas of 3 maps and 9 plates (generally referred to as "System Glaciare"). 2 Jean de Charpentier, " Essai sur les glaciers et sur le terrain erratique du bassin du Rhone," Lausanne, 1841, pp. 1-363. Map and plates. 3 Eduard Bruckner, " Klimaschwankungen und Volkerwanderungen im xix. Jahrhundert," I tern. Wochensch. f. Wissenschaft, Kunst und Technik, March 5, 1910, p. 6. 4 Siegfried Passage, "Die Kalihari," Berlin, 1904, p. 662. A. Penck, "Climatic Features of the Ice Age," Geogr. Jour., vol. 22, 1906, pp. 185- 186. Ellsworth Huntington, "Some Characteristics of the Glacial Period in Non-glaciated Regions," Bull. Geol. Soc. Am., vol. 18, 1907, pp. 351- 388, pis. 31-35. Ellsworth Huntington, "The Pulse of Asia," New York and Boston, 1907, pp. i-xxi, 1-415. Ellsworth Huntington, "The Libyan Oasis of Kharga," Bull. Am. Geogr. Soc., vol. 42, 1910, pp. 660-661. 5 Frank Leverett, "Comparison of North American and European glacial deposits," Zeitsch. f. Gletscherk, vol. 4, 1910, pp. 241-316. INTRODUCTION 11 6 "It is in fact the proportion of water vapor in the air which con- trols the greater or less abundance of snow precipitation, so that, as Tyndall has remarked, it is the solar action which is necessary to bring on the initial condition; the conclusion, which appears paradoxical at first, is the following, that the warmest periods determine more active evaporation of the ocean water ; it is to them that the greatest extensions of glaciation correspond. Cold plays the merely passive role of condenser." (Gourdon, Exped. Ant. Frang., 1903-1905, Glaciologie, 1908, p. 70.) 7 1. C. Russell, "Climatic Changes indicated by the Glaciers of North America," Am. Geol., vol. 9, 1892, p. 336. 8 A. Penck, "Climatic Features of the Pleistocene Ice Age," Geogr. Jour., vol. 27, 1906, pp. 182-187. 8a William Herbert Hobbs, " The Cycle of Mountain Glaciation," Geogr. Jour., vol. 36, 1910, pp. 146-163, 268-284, 36 figs. 9 W. M. Davis, "Glacial Erosion in France, Switzerland, and Norway," Proc. Bos. Soc. Nat. Hist., vol. 29, 1900, pp. 294-300. 10 1. C. Russell, "Glaciers of North America," 1897, pp. 190-206. 11 E. v. Drygalski says : "The difference between glaciers and inland ice is essentially a quantitative one. Glacier forms are small, inland ice masses great glaciations. . . . Inland ice masses are ice overflows of entire earth surfaces, glaciers are branching outflow systems for snow deposits guided by the features of the earth's surface." In Keilhack's "Lehrbuch der praktischen Geologie," 1908, p. 269. 12 Karl Grossmann, "Observations on the glaciation of Iceland," Gla- cialists' Magazine, vol. 1, No. 2, 1893, pi. 3, fig. 2. 13 "The visitor replied that he was a valley climber, not a mountain climber. He found sufficient pleasure at the mountain base, and such was my case also. Mountain tops are indeed worthy objects of a climb- er's ambition, but if one wishes to get at the bottom facts, let him ex- amine the valleys." (W. M. Davis, "Glacier Erosion in the Valley of the Ticino," Appalachia, vol. 9, 1901, p. 137.) 14 On hanging valleys, see especially W. M. Davis, Proc. Bos. Soc. Nat. Hist., vol. 29, 1901, pp. 273-322; and G. K. Gilbert, "Glaciers," Harri- man Alaska Expedition, vol. 3. 15 W. M. Davis, "The Sculpture of Mountains by Glaciers," Scot. Geogr. Mag., vol. 22, 1906, figs. 1-3. 16 Ed. Bruckner, " Die Glacialen Ziige im Antlitz der Alpen," Naturw. Wochensch., N. F., vol. 8, 1909, p. 792. 17 Penck, "Glacial Features in the Surface of the Alps," Jour. GeoL, vol. 13, 1905, p. 6. PART I MOUNTAIN GLACIERS CHAPTER I THE CIRQUE AND ITS RECESSION The Glacial Amphitheatre in Literature. It is safe to say that no topographic feature is more characteristic of the mountains which have been occupied by glaciers than is the cirque. Approaching a range from a considerable distance, there is certainly no feature which so quickly forces itself upon the attention. The U-shaped valley and the hanging side valley, important as these are, are here decidedly less im- pressive. Yet the great majority of works upon the subject, by ignoring the significance of the cirque, allow the reader to assume that the glaciers discovered the cirques ready formed to gather in the snows for their nourishment. Even the standard work of Chamberlin and Salisbury is open to this objection. 1 Despite the attitude of the general texts, which so largely determine what might be called the accepted body of doc- trine of a science, there are a number of papers dealing with the origin of the cirque. One of the first to recognize the cirque as a product of glacial erosion was Tyndall, whose keen mind has so illumined the page of mountain glaciation. 2 In opposition to his view, Bonney published in 1871 a somewhat elaborate article, in which the line of argument was : (1) that the Alpine cirques must have been produced by the agency 12 THE CIRQUE AND ITS RECESSION 13 which shaped the valleys below them; (2) that the valleys were not moulded by glaciers; and hence, (3) the cirques must have been retained from the pre-glacial land surface. 3 The published discussion of this paper developed no oppo- sition to the view, though Doctor, now Sir Archibald, Geikie stated that he could not see his way to account for the vertical walls surrounding the cirque. On the other hand, the Italian Professor Gastaldi recognized the work of the ice in the shap- ing of cirques in the Italian Alps, 4 as Helland did in those of Norway. The latter believed that excessive weathering in the rock above the neve played an important role, though ab- rasion by the ice upon the floor was the larger factor. 5 Later Russell in America, 6 Wallace in England, 7 and de Martonne upon the continent, 8 further advocated the glacial origin of cirques. Penck has explained the development of cirques as the result of sub-glacial weathering alternate thawing and freezing beneath glaciers during the incipient stage particularly (" hanging glaciers "). 9 This eroding process, he considered, would be greatest toward the middle of the glacier, so that the original concavity of the slope beneath it would be more and more deepened. It must be evident that this explanation does not properly account for the steep- ness of the cirque walls, which it will be remembered could not be accounted for by Geikie. Attention was again directed to the process of cirque shap- ing by an important paper of Richter's published in 1896. 10 His studies having been made in Norway, where a country rounded and polished by the continental glacier had been only partly invested by mountain glaciers, the cirques from the latter formed individual " niches " in the uplands. Fol- lowing Gastaldi, the form of these niches was happily likened to that of an armchair (see Fig. 4). 11 Richter observed that the steep walls of the cirque were the only surfaces ungla- ciated, and hence he concluded that they were not to be 14 CHARACTERISTICS OF EXISTING GLACIERS ascribed to ice-abrasion, but to weathering. The moulding of the cirque floor he ascribed to abrasion, and, referring to the cirque walls, said - The material loosened by weathering is removed by the gla- cier or slides off over the neve to form either actual moraines, or, at least, neve moraines. These walls do not bury themselves in their own debris, and in consequence continually offer fresh surfaces for attack. Finally, the wearing away of the cirque floor by the glacier cooperates to keep the cirque walls on a steep angle and facilitates avalanching. FIG. 4. Cirque excavated in the glaciated surface of Norway, Northern Kjedel on Galdhopig (after E. Richter). In a more extended and later paper, 12 treating especially the formation of cirques, Richter has explained that his view differs from that of Helland only in ascribing greater impor- tance to weathering upon the cirque walls and less to abrasion upon the cirque floor. Inasmuch as the excessive weather- ing of cirque walls, as maintained by Richter, is above the sur- face of the neve, a horizontal plane of denudation should develop at that level. No evidence of this plane being dis- covered, its absence is explained by Richter through abra- sion from the snowbank which would collect upon it so soon as formed. This is the fatal weakness of the Richter hypothesis. Relation of Cirque to Bergschrund. Up to the beginning of the twentieth century, as we have seen, few geologists had THE CIRQUE AND ITS RECESSION 15 greatly concerned themselves with the erosion conditions at high levels, the work of Richter being on the whole the most comprehensive. The whole subject of cirque erosion was rather generally ignored, as it is, indeed, to-day. Sir Archi- bald Geikie, referring to the corries of the Scottish High- lands, 13 wrote The process of excavation seems to have been mainly carried on by small convergent torrents, aided, of course, by the power- ful cooperation of the frosts that are so frequent and so potent at these altitudes. Snow and glacier ice may possibly have had also a share in the task. Writing in the same year, Reusch ascribed the Norwegian cirques to the action of surface water descending through the crevasses over falls in the continental glacier which, in Pleis- tocene times, overrode the country ; 14 and the following year Bonney reiterated his view that cirques were the product of water-erosion. 15 Only a few years before, Gannett had curi- ously explained the origin of cirques through the wear of avalanched snow and ice upon the cirque floor, likening the erosive process to that which takes place beneath a water- fall. 16 The discovery of the method by which the glacier exca- vates its amphitheatre must be credited to a keen American topographer-geologist, Mr. Willard D. Johnson of the United States Geological Survey. 17 In fact, to him and to another American topographer, Mr. Francois E. Matthes, we owe the most of what is known from observation concerning the initiation and developme^fof the glacier cirque. Reasoning that abrasion was incompetent to shape the amphitheatre, Johnson early surmised thatVthe great gaping crevasse which so generally parallels the cirque wall and is termed the Bergschrund (Fr., rimaye) went down to the rock beneath the neve, and that it was no accident that glaciated moun- tains alone " abound in forms peculiarly favorable to snow- 16 CHARACTERISTICS OF EXISTING GLACIERS drift accumulation " (see Fig. 5). These observations were made as early as 1883, and in order to test his theory, John- FIG. 5. Bergschrund below cirque wall on a glacier of the Sierra Nevada, Cali- fornia (after Gilbert). THE CIRQUE AND ITS RECESSION 17 son allowed himself to be lowered at the end of a rope 150 feet into the Bergschrund of the Mount Lyell glacier until he reached the bottom. He found a rock floor to stand upon, and rock extended up for 20 feet upon the cliff side. We may here quote his terse sentences, since too little attention has been accorded this important observation. 18 The glacier side of the crevasse presented the more clearly defined wall. The rock face, though hard and undecayed, was much riven, the fracture planes outlining sharply angular masses in all stages of displacement and dislodgment. Several blocks were tipped forward and rested against the opposite wall of ice ; others quite removed across the gap were incorporated in the glacier mass at its base. Everywhere in the crevasse there was melting, and thin scales of ice could be removed from the seams in the rock. The bed of the glacier, elsewhere protected from frostwork, was here subjected to exceptionally rapid weathering. By maintaining the rock wall continually wet, and by admitting the warm air from the surface during the day, diurnal changes of temperature here resulted in very appreciable mechanical effects, whereas above the neve only the seasonal effects were important. This observation of Johnson is, it will be observed, in con- trast with the suppositions of Richter, who believed that the maximum sapping upon the cirque wall occurred above the surface of the neve. The function of the Bergschrund, which separates the stationary from the moving snow and ice within the neve, is thus found to be of paramount importance in the shaping of the amphitheatre. With the coming of winter this process halts and the Bergschrund fills with snow, but the following spring it again opens, though always a little higher up and nearer to the cirque wall. In this way the blocks excavated from the base of the wall are the more easily transferred to the moving portions of the glacier. 19 18 CHARACTERISTICS OF EXISTING GLACIERS The Schrundline. That a sharp line is observable in aban- doned cirques separating the accessible from the non-scal- able portions of the wall, has been pointed out by Gilbert, who has given his support to the view of Johnson, and con- firmed it by observations of his own 20 (see Fig. 6). Penck, on FIG. 6. Schrundline near Mt. McClure in the Sierra Nevadas of California. Above the Schrundline it is too steep for snow to rest, and the drifts are ac- cordingly below this level (after Gilbert). the other hand, the following year revived the view of Richter that excessive sapping occurs upon the cirque walls above the neve surface, 21 though he calls in the Bergschrund in order to gather in and remove the rock fragments which fall from the cliff. 22 Initiation of the Cirque, Nivation. Johnson's studies upon the processes of cirque shaping, had shown how a nearly perpendicular cirque wall is steadily cut backward through basal sapping at the bottom of the Bergschrund. The prob- lem of how the snowbank, which was the inevitable forerun- ner of the glacier, had transformed the relatively shallow THE CIRQUE AND ITS RECESSION 19 depression which it presumably discovered into the steep- walled amphitheatre, he did not attempt to solve. Yet the nourishing catchment basin is a prerequisite to the existence of the normal glacier. The solution of this problem has been suggested by another American topographer, Mr. F. E. Matthes. 23 In the Bighorn mountains of Wyoming he has found exceptional opportunities for this study. Owing to the low precipitation within the region and the consequently inadequate nourishment of glaciers, a large part of the pre-glacial surface still remains. There is, therefore, repre- sented within the district every gradation from valleys which were occupied by snow during a portion only of the year to those which were the beds of glaciers many miles in length. Both small glaciers and high-level drifts of snow still remain in a number of places. Mr. Matthes has demonstrated that the snowbanks with- out movement steadily deepen the often slight depressions within which they lie by a process which he has called "niva- tion " - excessive frost-work about the receding mar- gins of the drifts during the sum- mer season. The ground being con- tinually moist in this belt due to the melting Of the FIG. 7. Cross section of a snowdrift site on a slope cnnw tVi<=> wafpr showing formation of niche by nivation (after LOW > Matthes). penetrates into every crevice of the underlying rock, so that it is rent dur- ing the nightly freezing. Rock material thus broken up and eventually comminuted, is removed by the rills of water from the melting snow. 24 By this process the original 20 CHARACTERISTICS OF EXISTING GLACIERS depression is deepened, and, if upon a steep slope, its wall becomes recessed (see Fig. 7). The occupation of a V-shaped valley by snow, as Matthes has further shown, tends through the operation of this process to transform it into one of U -sect ion, since the weath- ered rock material upon the slopes is transported by the rills and deposited upon the floor. All gradations from nivated to glaciated forms are to be found in the Bighorn range. During the field season of 1909 the writer took the oppor- tunity to examine neve regions and high-level snowbanks in a number of districts, with the result of confirming the im- portance of the nivation process as outlined by Matthes. In plate 2 A and B are shown two snowbanks which were photographed on July 25 near the summit of Quadrant mountain, in the Gallatin range of the Yellowstone National Park. The gently sloping surface of this mountain repre- sents the pre-glacial upland unmodified by Pleistocene gla- ciation. Though between 9000 and 10,000 feet above sea, it supports a rich herbage, and is a favorite grazing-ground of the elk. In A of plate 2 the snow bank is seen surrounded by a wide zone within which no grass is growing, but where a finely comminuted brown soil is becoming a prey to the mov- ing water. B of plate 2 exhibits another bank lying in the depression which it has largely hollowed. At its lower end (at the left) is seen an apron of fine brown mud deposited by the overburdened stream as it issues from beneath the drift. Later the writer has had in Swedish Lapland opportunity to observe the results of the nivation process under excep- tionally favorable circumstances. Here in place of a pre- glacial surface, such as has been dissected in the American mountain districts already described, the surface of the country has been planed down to softly rounded knobs of rather large scale under the influence of the mantling con- PLATE 2. A. Summer snowbank surrounded by brown border of finely comminuted rock. Quadrant Mountain, Y.N.P. B. Snowbank lying in a depression largely of its own construction. Note stream, outwash of fine mud at the left. Quadrant Mountain, Y.N.P. THE CIRQUE AND ITS RECESSION 21 tinental glacier of Pleistocene time. Subsequent to this gen- eral planation the higher areas have in favorable situations been occupied either by mountain glaciers or by more or less persistent snow-drifts. The drift sites are found upon the hillsides as distinct niches in which the characteristic " arm- chair " form of the incipient cirque is already apparent. It is the scale particularly which distinguishes them from glacial amphitheatres (see Fig. 8). It is of great interest to find FIG. 8. The characteristic form of drift sites on hillsides in Swedish Lapland. The form of the cirque is already discernible. On the floor a division into hexa- gons indicates that the process of solifluction has played an important part. (After a photograph by G. W. v. Zahn.) 26 that the quite remarkable but as yet little understood pro- cess of rock flow (solifluction) has here played an impor- tant part in shaping the incipient cirque. The floors of the drift sites are in some instances at least divided into the hexagonal pattern so characteristic of soil flow on relatively 22 CHARACTERISTICS OF EXISTING GLACIERS flat surfaces. 26 Inasmuch as it is now recognized that melt- ing snow is the immediate requisite for effective solifluction, it is apparent that this process in some of its phases at least is clearly allied to the process of nivation. An interesting question is at what point the snow-field or neve will, by taking on a motion of translation, assume the functions of a glacier. At this stage of transition the Berg- schrund should first make its appearance. Comparison of nivated and glaciated slopes in the Bighorn mountains led Matthes to think that upon a 12 per cent, grade the neve must attain a thickness of at least 125 feet before motion is possible. Another possible method of approaching this problem has suggested itself to the writer. In mountains like the Selkirks, with steep slopes terraced by the flatly dip- ping layers in the rock, a peculiar type of small cliff glacier is nourished high above the larger snow-fields of the range and avalanched upon the lower shelves so as to leave vertical sections open to study (see plate 3 A). Perhaps because of their small size these cliff glaciers have not developed cirques, though a Bergschrund parallels the generally straight head- wall. Examined through a powerful glass, the snow in the lower layers can be seen to have lost its brilliant whiteness, though it does not yet appear as ice. A number were ex- amined with a view to determine the approximate minimum thickness of the glacier, but all exceed the minimum estimate of Matthes by at least 100 feet. This is not regarded as in any way discrediting his figure, but rather as suggesting the possibility of more thorough examination along the same line. REFERENCES 1 "Geology," vol. 1 : "Processes and their Results," 1904, pp. 272-276, and especially fig. 250. See also "College Geology," by the same authors, 1909, p. 256. 2 John Tyndall, "On the Conformation of the Alps," Phil. Mag., Ser. 4, vol. 24, 1862, pp. 169-173. THE CIRQUE AND ITS RECESSION 23 * T. G. Bonney, "On the Formation of 'Cirques,' with their Bearing upon Theories attributing the Excavation of Mountain Valleys mainly to the Action of Glaciers," Quart. Jour. Geol. Soc., vol. 27, 1871, pp. 312- 324. 4 B. Gastaldi, "On the Effects of Glacier-erosion in Alpine Valleys," ibid., vol. 29, 1873, pp. 396-401. 6 Amund Helland, "Ueber die Vergletscherung der Faroer, sowie der Shetland und Orkney Inseln," Zeitsch. d. Deutsch. Geol. Gesellsch., vol. 31, 1878, pp. 716-755, especially pp. 731-733. 6 1. C. Russell, "Quarternary History of Mono Valley, California," 8th Ann. Rept. U. S. Geol. Surv., 1889, pp. 352-355. 7 A. R. Wallace, "The Ice Age and its Work," Fortnightly Review, vol. 60, 1893, especially p. 757. 8 E. de Martonne, "Sur la periode glaciaire dans les Karpates meri- dionales," C. R. Acad. Sci. Paris, vol. 129, 1899, pp. 894-897 ; ibid., vol. 132, 1901, p. 362. 9 Albrecht Penck, "Morphologic der Erdoberflache," vol. 2, 1894, pp. 307-308, figs. 17-20. 10 E. Richter, " Geomorphologische Beobachtungen aus Norwegen," Sitzungsber. Wiener Akad., Math.-Naturw. KL, vol. 106, 1896, Abt. I., pp. 152-164, 2 pis. and 2 figs. 11 See topographic definition of the cirque by De Martonne ("La periode glaciaire dans les Karpates meridionales," C.R., 9 e Cong. Geol. Intern., Vienna, 1903, pp. 694, 695). 12 E. Richter, "Geomorphologische Untersuchungen in den Hochalpen," Pet. Mitt., Erganzungsheft 132, 1900, pp. 1-103, pis. 1-6. 13 "Scenery of Scotland," p. 183 (revised in 1901). 14 H. Reusch, Norges Geol giske Undersogelse, No. 32, Aarbog for 1900, 1901, pp. 259, 260. 15 "Alpine Valleys in Relation to Glaciers," Quart. Jour. Geol. Soc., vol. 68, 1902, p. 699. 16 "The effect is precisely like a waterfall. The falling snow and ice dig a hollow depression at the foot of the steep descent just as water does." (Nat. Geogr. Mag., vol. 9, 1898, p. 419.) 17 W. D. Johnson, "An Unrecognized Process in Glacial Erosion" (read before the Eleventh Annual Meeting of the Geological Society of America), Science, N.S., vol. 9, 1899, p. 106; also "The Work of Glaciers in High Mountains" (lecture before the National Geographic Society), ibid., pp. 112, 113. The first public formulation of the doctrine by Mr. Johnson was in an address before the Geological Section of the Science Associa- tion of the University of California, delivered September 27, 1892. 18 W. D. Johnson, " Maturity in Alpine Glacial Erosion," Jour. Geol., vol. 12, 1904, pp. 569-578 (read at Intern. Congr. Arts and Sciences, St. Louis, 1904). 19 1. C. Russell, "Glaciers of North America," 1897, p. 193. 20 G. K. Gilbert, "Systematic Asymmetry of Crest-lines in the High Sierras of California," Jour. Geol., vol. 13, 1905, pp. 579-588. See also E. C. Andrews, ibid., vol. 14, 1906, p. 44. 24 CHARACTERISTICS OF EXISTING GLACIERS 21 Many European glacialists and among them apparently Garwood (Geogr. Jour., vol. 36, 1910, p. 313), have failed clearly to understand that the basal sapping occurs at and near the base of the Bergschrund. 22 Albrecht Penck, "Glacial Features in the Surface of the Alps," Jour. Geol., vol. 13, 1905, pp. 15-17. 23 Francois E. Matthes, "Glacial Sculpture of the Bighorn Mountains, Wyoming," 21st Ann. Rept. U. S. Geol. Surv., 1899-1900, pp. 167-190. 24 Mainly in later seasons. 25 The structure of the pavement in the foreground has been added from another photograph. 26 See H. W. Feilden, "Notes on the Glacial Geology of Arctic Europe and its Islands," Quart. Jour. Geol. Soc., vol. 62, 1896, p. 738 ; also O. Nordenskiold, "On the Geology and Physical Geography of East-Green- land," Meddelelser om Gronland, vol. 28, 1908, p. 273; also O. Nordenskiold, *'Die Polarwelt und ihre Nachbarlander," Leipzig and Berlin, 1909, p. 63 ; also W. H. Hobbs, "Soil Stripes in Cold Humid Regions," 12th Report Mich. Acad. Sci., 1910, pp. 51-53. CHAPTER II HIGH LEVEL SCULPTURING OF THE UPLAND The Upland 1 dissected. Having obtained a clear concep- tion of the process of head-wall erosion through basal sap- ping, Johnson was in a position to account for the topography which he encountered in the High Sierras of California. This topography is best described in his own words : 2 In ground plan the canyon heads crowded upon the summit upland, frequently intersecting. They scalloped its borders, producing remnantal table effects. In plan as in profile, the inset arcs of the amphitheatres were vigorously suggestive of basal sapping and recession. The summit upland the pre- glacial upland beyond a doubt was recognizable only in patches, long and narrow and irregular in plan, detached and variously disposed as to orientation, but always in sharp tabu- lar relief and always scalloped. I likened it then, and by way of illustration I can best do so now, to the irregular remnants of a sheet of dough on the biscuit board after the biscuit tin has done its work. In a portion of the region where Johnson's studies were made, his views have received verification by Lawson in a beautifully illustrated paper. 3 Davis has furnished an ex- cellent example from the Tian Shan mountains of the opera- tion of the same cirque-cutting process, recording his adhe- sion to the Johnson doctrine, 4 though many of his later papers would indicate that he did not ascribe large importance to 25 26 CHARACTERISTICS OF EXISTING GLACIERS the discovery. 5 In 1909 two papers from his pen give, how- ever, larger prominence to the process. 6 With little doubt the failure to generally recognize the im- portance of this process of cirque recession, clearly here a more effective agent than abrasion, is to be explained by the fact that in parts of Europe and in the Alps in particular, one looks in vain for evidences of the ear- lier and more signifi- cant stages of the process. Glaciation was here so vigorous as to cause the re- moval of all summit upland. Within the arid regions of the western United States, a more fruit- ful field for study is to be found. Here the work of Johnson has been supple- mented by that of Gilbert 7 and Matthes. 8 Perhaps no- where are the early stages of the process so clearly revealed as in the Bighorn Mountains of Wyoming (see Fig. 9). A somewhat more advanced stage of the same process is to be found in the Uinta mountains of Wyoming, recently de- scribed in a valuable monograph by Atwood, though here without consideration of the cirque-cutting process in ac- counting for the present topography. 9 Yet nowhere, so far as the present writer is aware, has a view been reproduced which so well illustrates the remnantal tableland and the "biscuit-cutting" process of cirque recession (see Fig. 10). 10 The present writer has photographed other examples of the FIG. 9. Pre-glacial upland invaded by cirques "biscuit-cutting" effect; Bighorn Mountains, Wyoming. PLATE 3. A. View of the Yoho Glacier at the head of the Yoho Valley, showing to the right a series of three small cliff glaciers. Canadian Rockies. B. Pre-glacial upland on Quadrant Mountain, Y.N.P., invaded by the cirque known as the "Pocket." HIGH LEVEL SCULPTURING OF THE UPLAND 27 same type in the Yellowstone National Park (see plate 3 B and Fig. 11). Remnants of the pre-glacial surface will, in FIG. 10. View of the scalloped tableland within the Uinta range and near the head of the west fork of Sheep Creek (after Atwood). any given district, be large or small according as nourishment of the glaciers has been insufficient or the reverse. The Uinta range, which extends in an east-west direction, and, FIG. 11. Map of Quadrant Mountain, a remnant of the pre-glacial upland on the flanks of the Gallatin Range, Y. N. P. 28 CHARACTERISTICS OF EXISTING GLACIERS like the Bighorn mountains, has a core of homogeneous granitic rock, displays this fact. An examination of At- wood's map n shows that to the eastward, where the precipi- tation has been least, the remnants of the original upland are more considerable. This qualifying condition of glacier nourishment will be subject to some modification because of peculiarities in snow distribution. As shown by Gilbert, the FIG. 12. Series of semicircular glacial amphitheatres whose scalloped crest forma part of the divide of the North American continent. first glaciers within any mountain district will probably appear upon that side of the divide which is in the lee of the prevailing winds. This fact is particularly well brought out in Fig. 12. Such a condition as is here represented, gives a most de- cisive answer to the question concerning the protective or denuding action of glacier ice. To the west of the divide the snow has been swept clear, and these sweepings lodg- ing in the lee have produced the glaciers on this side only. PLATE 4. K g *| ^ |1 a IS I H ii 2 M S C8 'C e J2 W) 2 'S o c fi-l I5I& nil s!fl '^3 *0 T3 "S ^ S >, all II c ^ -c a O 1-1