Canadian Alpine Journal/Volume 1/Number 2/The Nature and Activity of Canadian Glaciers

by William Hittell Sherzer

THE NATURE AND ACTIVITY OF CANADIAN GLACIERS.

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By William Hittell Sherzer.

None the less attractive the glacial student than to the mountain climber is that grand array of peaks and snow-fields which stretches poleward through the western part of the Dominion of Canada. Here upon a magnificent scale and in endless variety and profusion one may recognize the various types of glaciers, detect in them every feature known to science and about them every form of geological activity ascribed to these great engines of rock destruction and transportation. About the peaks and ridges and in the higher valleys there accumulates season after season layer upon layer of snow, which, by its own pressure, surface melting and occasional rain or cloud mist is gradually compacted into ice. Indefinite accumulation of this congealed moisture is prevented by one of those beneficent provisions of Nature by which, under the influence of its own weight, this ice in frozen streams, or shorter tongues, moves slowly to lower levels where complete melting may occur and this moisture again be put into general circulation. Were it not for this the Canadian Rockies and Selkirks would be encased in a great ice ridge, extending as high into the atmosphere as it is possible for moisture to be lifted, from the sides of which tremendous avalanches would hurl themselves to the adjacent plains, deeply covering regions now free from snow during a portion of the year.

Although the mechanics of glacial motion are not yet fully understood, these ice-streams appear to move much as would a similar mass of asphaltum, with which they have often been compared. They conform more or less perfectly to the shape of the valley and irregularities of the bed, move more rapidly towards the centre and upper surface than toward the sides and bottom, flow more rapidly down steep slopes than gentle ones, and are more active during the day than at night and in summer than in winter. Where compelled to change their course too suddenly, or when subjected to a certain degree of tensional stress, great cracks are slowly opened at right angles to the direction of such stress. When one portion of the mass begins to lag it may be thrust forward bodily by great pressure from behind, compelled to mount reverse slopes, to scour the bed, detach rock fragments and transport whatever material finds lodgment within or upon the mass.

I. — Conditions Requisite for Glacial Formation.

In order that a certain region may support glaciers four conditions must be fulfilled, no two or three of which alone will suffice. (a) There must first be a degree of cold that will cause some of the precipitation to fall as snow or hail without which a glacier would be impossible, (b) The amount of such precipitation must be sufficiently great so that, in spite of the seasonal melting and evaporation, there will be a remnant to add to the accumulation of previous years. The entire snowfall of any 3'ear, or any short series of years, may be destroyed by melting, but, upon the whole, there must be more or less steady increase in the amount of congealed moisture, (c) There must be a collecting area, which from its shape or slope is capable of retaining the requisite amount of snow and ice. If the slope is too steep the snow will be avalanched from the area before the glacier has time to come into existence, (d) Finally, the local conditions must be of such a nature as

to permit of the inauguration of a movement in which

EASTERN MARGIN OF THE ILLECILLEWAET LOCAL ICE-CAP, SELKIRKS, B.C.

A. O. Wheeler, Photo

EASTERN MARGIN OF THE ILLECILLEWAET LOCAL ICE-CAP, SELKIRKS, B.C.
Note the relatively even character of the surface of the cap and its freedom from crevasses and rock debris.

there is more or less of a horizontal component. The chief factors concerned are the configuration of the collecting area and the weight of the accumulated snow. If movement is not permitted the entire mass remains a snow bank, or heap of stagnant ice which does not possess the essential characteristics of a glacier.

Space does not permit the discussion here of the distribution of modern and ancient glaciers over the face of the earth by which the application of the above conditions might be more readily comprehended by the reader. In general it may be said that when a glacier exists today these four conditions have been satisfactorily met in the past, although one or more of them may be now lacking. If a given area does not support a glacier, one or more of these conditions has been wanting, just which ones being readily determined by an inspection of the region. In the Canadian Rockies and Selkirks we find ideal conditions for glacier formation: broad valleys, basins and gentle slopes; high altitude and latidude; moisture-laden winds from the Pacific, causing heavy snowfall upon the western slopes and about the crests of these great systems.

When exposed to the warm rays of the sun the snowflakes melt into small globules which are subsequently frozen into pellets resembling granular tapioca. The snow in this condition is flnown as firn or névé, and from its consolidation the glaciers take their origin. In some way not yet fully understood the granules of the névé gradually diminish in number and increase in size until they attain the size of hazel-nuts or walnuts, or even the size of the fist in large glaciers like the Yoho and Illecillewaet. So long as the temperature of the ice is well beneath the freezing point these granules are not in evidence, the ice appearing compact and homogeneous. When, however, it begins to feel the effect of a higher temperature, there appears a delicate system of capillary tubes, outlining the granules and extending some distance into the ice mass. As melting proceeds these capillaries develop into narrow fissures separating the granules, and in the final stage a sharp blow will cause the ice to crumble into these component granules. It is in this granular structure that glacial ice is distinguished from that which results from the direct freezing of water, as in lakes, ponds and the pools and crevasses of the glaciers themselves. Such ice, commonly spoken of as "water-ice," consists of appromixately parallel prisms, arranged with their axes perpendicular to the freezing surface. This structure is often strikingly shown in the case of lake and river ice when in the spring it is undergoing disintegration.

2.—Principal Types of Glaciers.

Without attempting to draw any sharp lines of distinction between them there may be recognized four types of glaciers, all but one of which have numerous representatives in the Canadian Rockies and Selkirks. This one, not now represented, occupied the region during the previous geological epoch and its work is much in evidence in and about the mountains. These types may best be described in the order of their simplicity, frequency and development.

(a) Alpine Glaciers. In its simplest from this type originates from the snow which accumulates about a mountain pass, or within an amphitheatre, combined with that precipitated directly into the valley, or avalanched from the adjacent slopes. Having much the appearance of a great frozen river, it slowly winds its way clown the valley to a level determined by a number of factors; chief of which are the latitude, thickness of the ice, exposure to the sun, amount and distribution of rocky debris and the amount of snow and ice urging the glacier forward. Canadian examples are the Victoria, Yoho and the easternmost stream of the Asulkan

THE ASULKAN GLACIER FROM MT. AVALANCHE

THE ASULKAN GLACIER FROM MT. AVALANCHE

The entire series represents a hanging Piedmont glacier in a state of decadence, the four right-hand components having separated into small Alpine glaciers. The three left-hand components are still united, forming the Asulkan Glacier, but have started to separate.

GENERAL VIEW OF VICTORIA GLACIER AND ITS TRIBUTARIES

GENERAL VIEW OF VICTORIA GLACIER AND ITS TRIBUTARIES

Copyright, 1902, by Detroit Photographic Co.

glaciers. The snow line crossing the glacier divides the upper surface into two regions which are designated as the névé, or region of perennial snow, and the dissipator, or that portion ordinarily free from snow during late summer and early autumn. Glaciers of the alpine type may receive tributaries from confluent valleys and these in turn receive tributary ice-streams. If we consider that the Mitre Glacier originates about the Mitre Pass, it receives a short, broad tributary from between Mitre Mountain and Mount Lefroy and together they join the Victoria, being compressed to about one-fifth of their breadth. Not infrequently it happens that the main glacial stream does not fill the valley and it is separated from its tributary streams by a precipice, or very steep slope over which the ice and snow are avalanched. The higher glacier is termed a hanging or cliff glacier, as seen upon the eastern shoulders of Mts. Victoria and Lefroy, and the glacier formed by the recementing of the ice fragments is spoken of as a reconstructed or regenerated. A very interesting example of such a regenerated glacier is formed from the hanging Lefroy, the fragments of which accumulate at the foot of the eastern wall of Mt. Lefroy, upon the upper western margin of the Mitre Glacier. There is piled up there, mainly in the summer, a mass of ice fragments, along with the ground-morainic material manufactured beneath the hanging glacier, which gives rise to a regenerated glacier resting upon the Mitre and which is more or less independent of it. The course of the regenerated Lefroy is across the Mitre, where it dumps upon the opposite side a great heap of ground moraine, while it is at the same time carried bodily toward the Victoria. Such a glacier, of which this is the best example known, has been more or less appropriately called parasitic.

(b) Piedmont Glaciers. When a well-nourished glacier of the alpine type flows from a valley out upon the adjacent plain it has a tendency to spread laterally as soon as the restraint of the rocky walls is removed. In the case of such glaciers derived from a series of neighboring valleys their expanded extremities may coalesce laterally and form a glacier of the piedmont type. The separate alpine glaciers retain their independence so far as nourishment, structure, rate of movement and geological work are concerned and may better be termed commensal streams than tributaries. In their form, size and direction of movement they are more or less affected by their neighbors, gaining in protection and power by the union, so that a piedmont glacier is able to maintain itself at a lower level than could its separate commensals. Such glaciers are peculiarly broad and short and present a relatively great amount of frontage, which is more or less irregular or lobed by the noses of the component streams, some of which may be advancing while others are stationary or in retreat. The Wenkchemna Glacier is an interesting example of this type, having a length of one-half to one mile, a breadth of about three miles and a frontage of over three miles. About a dozen commensal streams may be recognized which originate in the minor depressions upon the protected northern slopes of the Ten Peaks. The Horseshoe Glacier at the head of the neighboring Paradise Valley is of this same type, containing some sixteen alpine, component streams.

A similar although less characteristic type of piedmont glacier may originate upon an elevated mountain slope, which is crossed by a series of sub-parallel depressions, separated by rather low divides. Each depression may at first support a small alpine glacier, which, under favorable conditions for growth, may increase in thickness until it more than fills its bed and unites laterally with its neighbors. If the supply of snow is sufficiently reduced, the loss by wind action, melting and evaporation may uncover again the divides and the piedmont glacier shrinks into its original alpine compon

A. O. Wheeler. Photo

GENERAL VIEW OF THE WENKCHEMNA GLACIER
A PIEDMONT TYPE
Note the peculiar form of the glacier, the very general débris covering and the scanty snow supply of the component streams.

ents; thus attaining its second childhood. Such a glacier would have the position of a hanging or cliff glacier and might nourish another of the alpine type or give rise to a regenerated glacier. Upon the high western slope of the Asulkan Valley there existed such a glacier in recent geological time, which avalanched its ice to the alpine glacier which occupied the valley itself. The Asulkan Glacier, with its three commensal streams, is all that is left to show the piedmont character of the original, the remainder of the glacier having been resolved into its alpine components, lying between the Dome and Mt. Abbott.

(c) Local Ice-Caps. These are extensive fields of stratified ice and snow which are represented in the Rockies by the Waputik and Columbia Ice-fields and in the Selkirks by the smaller Illecillewaet field. They must originate in a system of alpine and piedmont glaciers which have been unable to drain away the ice as fast as it was supplied, and, if the expression may be permitted, the entire region is flooded with snow and ice. Accumulation continues until the lobes of ice which come into existence about the margin of the cap are able to drain away the excess, when an approximate condition of equilibrium is established. These marginal lobes may reach neighboring valleys, or the adjacent plains, and give rise to alpine and piedmont glaciers. The surface of such ice-caps is generally sloping or undulating, strongly ripple-marked by wind action and free from rock debris. Owing to the thickness of the ice and its sluggish conditions, crevasses are not common. Occasionally rocky islands protrude through the frozen sea and are known as nunataks. If the supply of snow is sufficiently reduced the surface of the cap is slowly lowered, the marginal lobes are withdrawn and there may remain only the original piedmont and alpine glaciers from which the cap was developed. The field evidence is that all the existing group of glaciers in the Rockies and Selkirks were, in recent geological time, encased in such deposits of ice and snow, with only the higher peaks and ridges protruding.

(d) Continental Ice-sheets. During the so-called Pleistocene stage of the earth's history conditions were favorable for the formation of glaciers over the entire region between the Rockies and the Pacific and from the International Boundary to Alaska. These conditions resulted from an increased precipitation over the region and a reduction in the mean annual temperature. In the way above noted local ice-caps developed wherever favorable conditions existed and later were completely buried in snow and their outlines obliterated. With the submergence of the higher ridges the filling of the intervening valleys would go on slowly and at one stage the entire western portion of the Dominion was heavily encased in ice. The movement was mainly to the north, west and south, but piedmont glaciers of great magnitude developed along the eastern margin of the Rockies and reached out for many miles over the plains. In our imagination we may apply the same characteristics to this great ice-sheet, with its complex of submerged glaciers, that were noted for the local ice-cap. Climatic conditions finally changed and this continental type of glacier was slowly resolved into its components, only relatively few of which still remain to grace the landscape. Two similar ice-sheets developed further eastward, either simultaneously or subsequently, one centering to the west of Hudson's Bay and the other in Labrador. Existing glaciers of this type are found in Greenland and the Antarctic region.

3.—Geological Work of Glaciers.

Within the sphere of their activity glaciers may become powerful geological agents, destroying or modify

A. O. Wheeler, Photo

MT. BAILFOUR AND BALFOUR GLACIER FROM BOW PEAK

The view is of unusual geological interest, showing the relation of the névé-field to the short, Alpine glacier, the work of the drainage stream in covering the valley floor with gravel, and the formation of an extensive delta at the head of the lake. The left lateral and two medial moraines are well shown, as well as the transverse and marginal crevasses.

W. H. Sherzer, Photo. 1905

EROSIVE ACTION OF GLACIERS SHOWN UPON QUARTZITE NEAR HEAD OF PARADISE VALLEY

Notice the planing and striating of the upper surface, and the disrupting "plucking" of the massive blocks

A. O. Wheeler, Photo, 1902

THE DEVILLE GLACIER, SELKIRKS, B.C. FROM SUMMIT OF MOUNT FOX
SHOWING FORMATION OF FORBES' "DIRT BANDS"

ing former physiographic features and producing others anew. This phase of glacial study may be best presented under three headings.

(a) Glacial Erosion. The eroding action of pure ice upon firm rock, varying in hardness from that of limestone to quartzite, is apparently slight and limited to a smoothing and polishing effect. When the glacier is shod with rock fragments, as is frequently the case, and has considerable thickness, the erosive effect may be great if the action is prolonged. Hard rocks are gouged, scratched and planed and the fragments reduced to pebbles, sand and clay. The glacier's rock tools by which this action is accomplished are bruised, battered, planed and scratched and the edges and corners are more or less rounded in a manner entirely characteristic of glaciers. When a glacier of considerable thickness moves over a jointed, stratified rock, especially if the dip of the strata is in the direction of the movement, masses of rock may be detached bodily, giving rise to what is termed plucking. By this action a glacier may leave its bed rougher than it found it, and furnish the sites for lakelets, such as the exquisite lakes Agnes and Louise. An unusually fine example of this type of glacial erosion may be seen near the head of Paradise Valley, where blocks of quartzite as large as small houses have been disrupted from the parent bed and shifted but a short distance. Standing upon the undisturbed portion of the beautifully glaciated bed and looking down the valley it is difficult to escape the conviction that many feet of strata have been similarly removed. Many valleys in the Rockies and Selkirks appear to have been deepened and given their characteristic U-shape by alpine streams during the maximum period of glaciation. Their side walls, up to a certain height, have been smoothed and mountain spurs uniformly truncated, as well shown upon the Lake Louise side of Mt. Fairview. Glaciers exert this erosive power to their very heads and excavate often a semi-circular amphitheatre, or cirque, which may eat its way into the heart of a mountain and assist the atmospheric agencies in its destruction. A good example of such work is seen in the elevated Lake Agnes Valley, the glacier having nearly or quite disappeared from the region.

(b) Transportation. The loose material which a glacier finds in its path, along with that which it is able to pluck from its bed, is urged forward by sliding and rolling, or it may be incorporated into the base of the ice and transported bodily. Aside from the wind-blown dust which may be more or less evenly distributed throughout the body of the ice, the bulk of the material transported by the local ice-caps and continental ice-sheets lies in the basal layers. In the case of alpine and piedmont glaciers, however, from overtowering cliffs the active atmospheric agents may detach rock fragments which find their way to the surface of the glacier. If they reach the neve they may be incorporated into the body of the glacier, to appear later either at the surface of the dissipator or its extremity. Material carried thus either upon or within the ice suffers little abrasion compared with that at the base, but by means of crevasses and moulins it may work its way down to the lower zone. The transporting power of a glacier differs very markedly from that of a river since it is in no wise dependant upon its velocity. Rocks as large as a city block may be handled quite as easily as a grain of sand.

Owing to its relation to the steep cliffs of the Ten Peaks the Wenkchemna receives rock fragments along its entire breadth. In the case of the Victoria the upper valley is sufficiently narrow so that avalanches from Lefroy and Victoria may reach entirely across the neve, thus distributing rocky debris throughout the glacier there in process of formation. When brought below the snow-line by the forward movement there is a concentration of this material over the entire surface of these two glaciers, forming a thin veneering by which further melting is much retarded. Ordinarily the rock fragments accumulate in a relatively narrow zone along the margin of the glacier where they are moved very slowly forward, protecting from melting the ice upon which they rest until there is produced a sharp-crested ridge upon either side of the glacier—the lateral moraines. When such a moraine towers above the nose of the glacier more than a hundred feet, as is the case with the Illecillewaet, it is difficult for the ordinary observer to believe that it is essentially an ice-ridge with scarcely a foot of rock veneering. For the last few years the left lateral of the Asulkan has been shedding its cover near the lower end and this ice-core is well exposed and is being slowly destroyed.

When a glacier has a tributary, as in the case of the Victoria, the adjacent lateral moraines of the trunk and tributary streams unite and form a medial moraine, which has much the same appearance as the laterals. Under ideal conditions there will be one such medial for each tributary stream. Owing to the more rapid movement of the ice upon which they rest there is not the opportunity for the development found in the laterals. The material which rests upon the surface of the glacier has suffered but little abrasion and is thus readily distinguished from that which has occupied a basal position. Whenever a glacier is nourished, however, by a hanging glacier, as is the Lefroy, Victoria and Yoho, there occurs a mixture of the two types of material in the lateral moraine.

(c) Deposition. While the glacier is still in possession of a region there is being deposited in certain protected places beneath the ice the clay, sand and glaciated boulders, firmly pressed together and typically unassorted. Bluish-gray in color, until it is oxidized, this constitutes the ground-moraine. Owing to the action of sub-glacial streams patches of stratified sand and gravel may occur locally, the clay being carried away by the drainage. On account of the relatively slight grinding action of the present Canadian glaciers and lack of opportunity for lodgment, no extensive deposits of this ground-moraine or till are now forming. In connection with the great continental ice-sheets, however, deposits were formed several hundreds of feet in thickness.

During the process of retreat all the material carried in or upon the ice must be deposited as fast as complete melting proceeds. The rock débris of the lateral and medial moraines will be set down in corresponding lines or ridges, but of surprisingly insignificant proportions when contrasted with the original moraines. Rock fragments distributed over the general surface of the glacier will be somewhat evenly distributed over the bed as it is uncovered, so long as the retreat is fairly uniform. In case the melting at the lower extremity, however, just equals the forward movement, the end of the glacier comes to a halt and its load is dumped in a ridge, forming a terminal moraine, providing we have a glacier of the alpine type, which alone can be considered to have an end. In the case of the three other types of glaciers such moraines, testifying to the stages of halt of the front, but not of the ice itself, are known as frontal moraines. A good example is seen in connection with the Wenkchemna, previously referred to.

A noteworthy type of ancient moraine is found in connection with the five most accessible glaciers along the Canadian Pacific Railway, viz., the Victoria, Horseshoe, Wenkchemna. Illecillewaet and Asulkan Glaciers. In each case its double character can be made out, either through its disposition in separate ridges, or differences in age where heaped together. The moraines consist of massive blocks of quartzite and sandstone heaped tumultuously together without the usual filling

W. H. Sherzer, Photo. 1904

OLDER OF THE TWO "BEAR-DEN" MORAINES, VICTORIA GLACIER, CANADIAN ROCKIES
The coarse character of the blocks and the lack of filling material are believed to have resulted from the loading of the ancient glacier by means of an earthquake shock.

of gravel, sand and clay, differing strikingly from the moraines formed previously and subsequently. Between the great blocks, many of enormous size, spaces permit the entrance of man and other animals, so that Professor Tarr's name of "bear-den moraine" seems appropriate. Space will not permit a detailed discription here of these moraines, nor a full discussion of their probable origin. There is no reason for thinking that the ordinary filling material was originally present and removed by running water, or other agency. The blocks were not pushed along ahead of the ice, nor carried subglacially, but were carried either upon or within the ice. The ordinary proces of weathering would produce as much fine as coarse material and give rise to a terminal moraine of the ordinary type. An inspection of the cliffs from which the blocks were apparently derived shows that in all the five cases the general trend is northwest to southeast and that the bulk of the material was dropped to the eastward. The only plausible explanation which the writer has been able to frame is that these glaciers became loaded with these coarse blocks as the result of a double earthquake disturbance, which probably crossed the Rockies and Selkirks in a northeast-southwest direction. The two shocks were separated by two or three centuries and the first was either the most severe, or else it found more loose material awaiting its arrival. The mountains of the region appear to have served as a gigantic seismograph to record the time, number, relative intensity and direction of the shocks. A very rough estimate based upon the rings of growth of trees, indicates that these disturbances happened from 700 to 1000 years ago, or from the loth to the 13th centuries. Glaciers like the Geikie, whose bounding cliffs extend in a northeast-southwest direction, i.e., in the direction of wave transmission, would be able to secure but a slight load and might reasonably be expected to show no such moraines. Similarly the Yoho glacier, which is not bounded by steep cliffs capable of supplying such blocks no matter how severe the disturbance. Upon the eastern shoulder of Mt. Burgess there lies a mass of coarse blocks, very suggestive of these moraine blocks, which may have been shaken loose at the same time. The members of the Canadian Alpine Club can be of service in extending these observations to the north and south of the railway and in the collection of evidence which might verify or disprove the above hypothesis.

In describing their observations in the Sun Wapta Valley, Stutfield and Collie (Climbs and Exploration in the Canadian Rockies, 1903, page 126) note the occurrence of a similar type of moraine which may date back to the time of those above noted, or may have been due to a purely local rock-slide. In referring to the peaks Woolley and Stutfield, they say: "These two last mountains appeared to have been conducting themselves in a most erratic manner in bygone ages. A tremendous rock-fall had evidently taken place from their ugly, bare, limestone cliffs and the whole valley, nearly half a mile wide, was covered to a depth of some hundreds of feet with boulders and débris. What had happened, apparently, was this. The immense amount of rock that had fallen on the glacier below Peak Stutfield had prevented the ice from melting. Consequently the glacier, filling up the valley to a depth of at least two hundred feet, had moved bodily down; and its snout, a couple of hundred feet high, covered with blocks of stone the size of small houses, was playing havoc with the pine woods before it on either side. In our united experiences, extending over the Alps, the Caucasus, the Himalayas, and other mountain ranges, we had never seen indications of a landslide on so colossal a scale."

It is interesting to note that the Woolley-Stutfield range of cliffs has a northwest-southeast trend and that this rock débris was thrown to the eastward. It will be of much interest to ascertain whether other glaciers, lying between the headwaters of the Athabasca and the railway, which are favorably situated with reference to their cliffs, show such moraines.