Glacis

“ But glaciers, back in their cold solitudes, work apart from men, exerting their tremendous energies in silence and darkness. Coming in vapor from the sea, flying invisible on the wind, descending in snow, changing to ice, white, spiritlike, they brood outspread over the predestined landscapes, working on unwearied through unmeasured ages, until in the fullness of time the mountains and valleys are brought forth, channels furrowed for the rivers, basins made for meadows and lakes, and soil beds spread for the forests and fields that man and beast may be fed. ”

“ In many parts, magnificent glaciers extend from the mountain side to the water's edge. It is scarcely possible to imagine anything more beautiful than the beryl-like blue of these glaciers, and especially as contrasted with the dead white of the upper expanse of snow. The fragments which had fallen from the glacier into the water were floating away, and the channel with its icebergs presented, for the space of a mile, a miniature likeness of the Polar Sea. ”

“ I may as well stop here, and explain to you, once for all, what a glacier is. You see before you, as in this case, say thirty or forty mountain peaks, and between these peaks what seem to you frozen rivers. The snow from time to time melting, and dripping down the sides of the mountain, and congealing in the elevated hollows between the peaks, forms a half-fluid mass—a river of ice—which is called a glacier.
As it lies upon the slanting surface, and is not entirely solid throughout, the whole mass is continually pushing, with a gradual but imperceptible motion, down into the valleys below. ”

“ The water that escapes from a glacier is either black, like ink, or green, like absinthe, or white, like milk; it is always troubled, and charged with mud or earth full of fertilizing matter. So, while the glaciers make the higher valleys into a land of desolation and misery, lower down on the slopes that drink life from its flood, it is a garden, an orchard, a rich vine country, smiling hill-sides, shaded with trees and crowned with flowers. While a glacier is a stream of ice, it is not formed of frozen water, but of frozen snow. ”

“ The glacier, starting in its infant purity from some white, unsullied peak, loses, before many years have past, its spotless character. The wintry frosts, gathering [Pg 70] into iron bonds the streams which trickle down the mountain-sides, expand the water in freezing, and shatter the rocks with a force that the most solid cliffs cannot resist. Broken and weathered fragments are washed down from the slopes on every fall of rain, and dropping on to the once unspotted bosom of the glacier, swell the burden which is gradually laid upon it with advancing years. ”

“ When on my boat-voyage up the bay in the previous fall, this great glacier of Kingaite heaved heavenward its hoary head, supported by a body of crystal blue: on my return the same was covered with its winter dress. Before the cold weather sets in, all the crevices in the glacier are charged with water, which, congealing, is caused to expand; and the ice explodes with a sound like loud thunder, rending the mountains and shooting off icebergs and smaller fragments at the various points where the glacier has its arms reaching down to the sea. ”

“ Glaciers are streams of ice slowly descending from mountains and hanging on the slopes of those mountains from century to century. The white mass gradually descends, but so slowly that its progress is imperceptible to the eye. But as it descends and the lower parts melt, fresh ice forms in the upper part, and the great mass, therefore, remains the same in hulk. The slow and eternal descent of these hard fields of ice crushes the rocks beneath, and the glacier water, therefore, is mingled with powdered rocks and is whiter than the blue sea-water. ”

“ Glaciation, as we have seen, was developed in the same directions and over the same areas as we should expect it to be were the snow-line to be generally depressed. To put it in another way, were the snow-line by some means or other to be lowered over Europe, Asia, and North America, then, with sufficient precipitation, great ice-fields and glaciers would reappear in the very regions which they visited during Pleistocene times. Neither elevation nor depression of the land would be required to bring about such a result. ”

“ A glacier is one of the natural wonders of the [Pg 260] world and well might every one pay a visit to one of these great earth-sculpturers. The time to visit a glacier is during late summer, when the snows of the preceding winter are most completely removed from the surface. With the snows removed, the beauty of the ice and its almost stratified make-up are revealed. The snow, too, conceals the yawning bergschlunds and the dangerous, splendid crevasses. ”

“ The glaciers left by the last ice age naturally melted first in the lower reaches, and as those that now cap the peaks and flow down between ridges like the arms of a starfish, melt in their turn, they will leave their icy, green-blue crystal pools higher and higher up the mountainsides. ”

“ The widest crevasse that I could jump he would leap without so much as halting to take a look at it. The weather was now making quick changes, scattering bits of dazzling brightness through the wintry gloom; at rare intervals, when the sun broke forth wholly free, the glacier was seen from shore to shore with a bright array of encompassing mountains partly revealed, wearing the clouds as garments, while the prairie bloomed and sparkled with irised light from myriads of washed crystals. ”

“ In such remodelled moraines, the glacier-mud has, of course, been more or less washed away. We have here a blending of the action of water with that of the glacier; and, indeed, how could it be otherwise, when the colossal glaciers of past ages gradually disappeared or retreated to the mountain-heights? The wasting ice must have occasioned immense freshets, the action of which we shall trace hereafter, when examining the formation of our drift-ponds, of our river-beds and estuaries, as well as the river-terraces standing far above the present water-level. ”

“ Thus advancing, crevassed, convulsed, and rent into gaping chasms, loaded with blocks of stone, the glaciers are grinding down the everlasting hills and lowering the proud summits of their birthplace to the plain. Imagine half a hemisphere covered by a universal glacier whose powers of abrasion and transportation are proportionately enlarged: will not the appearances we are attempting to explain be adequately accounted for by so tremendous an agent? Let us turn to contemporaneous glaciers of the Alps and elsewhere for an answer. ”

“ Compressed by the immense weight of the superior strata, that lower portion of the névé which feeds the glacier is, at the very start, transformed into a solid ice, whose particles are cemented by the alternate melting and freezing which go on through all but the coldest weather of the year. Whether it is the pressure of the névé, or the irresistible expansion caused by the action of cold upon the water pervading its great mass, that drives off the glacier, is a question respecting which the most intelligent observers are by no means unanimous. ”

“ The winds and storms, too, contribute their share of dust and sand, and as the glacier still flows on, shrunken in size and laden with heaps of earth and rocks, at length it lays itself to rest, a mass of dirty ice and stones, in the valley towards which it has been ceaselessly progressing. ”

“ At a distance these glaciers, as I have said before, look like frozen rivers; when one approaches nearer, or where they press downward into the valley, like this Glacier de Boisson, they look like immense crystals and pillars of ice piled together in every conceivable form. ”

“ The glaciers perpetually move onward, at the rate of a foot each day, with a motion that commences at the spot where, on the boundaries of perpetual congelation, they are produced by the freezing 159of the waters which arise from the partial melting of the eternal snows. They drag with them from the regions whence they derive their origin, all the ruins of the mountain, enormous rocks, and immense accumulations of sand and stones. These are driven onwards by the irresistible stream of solid ice ”

“ A glacier tears away and carries away quantities of rock and earth that form the walls of its bed. As the valley narrows, tremendous pressure crowds the ice against the sides, tearing trees out by the roots and causing rock masses to fall on the top of the glacier, or to be dragged along frozen solidly into its sides. The weight of the ice bears on the bed of the glacier, and its progress crowds irresistibly against all loose rock material. The glacier's tools are the rocks it carries frozen into its icy walls and bottom. ”

“ The presence in the midst of forests and meadows and cultivated fields of these tongues of ice, ever melting and yet from year to year losing none of their bulk, proves that their loss is made good in the only possible way. They are fed by snow fields above, whose surplus of snow they drain away in the form of ice. The presence of glaciers below the snow line is a clear proof that, rigid and motionless as they appear, glaciers really are in constant motion down valley. ”

“ We know already what a hand the glaciers had in the Ice Age in shaping the course and conduct of rivers, and - 74 - you may be sure they have something to do with the making of rivers to-day. The under side of a glacier gets warmed from three sources: (1) its own pressure; (2) the friction as it moves; and (3) the heat from the inside of the earth which, on account of this thick ice blanket, can't get away into the air as it does elsewhere. This heat melts the ice and, as we know, there is water melting also on the surface of glaciers and in the crevasses. ”

“ All these facts have such a marked and intimate connection with the glaciers that still linger on the mountain-side, that no one—who had traversed those valleys, or traced the streams up to the ice-caves, from which many of them spring, turbid and overloaded with silt, at the foot of the glaciers—could doubt that these valleys, with all their peculiar features, owe their existence to the great extension of the glaciers, which in past time flowed from the mountains in great rivers of ice, and carved out those grand valleys to a depth of many thousands of feet in the solid rock. ”

“ Nature, in making a glacier, takes much longer, so that what was snow one year is only partly ice the next—it is known as nevé—and it is not until after several seasons that it becomes the pure ice we see in the lower part of a glacier. ”

“ Glacier ice is formed by snow accumulating at a given point more rapidly than it melts. This is due chiefly to wind, snow [Pg 353] slides, and heavy snowfall. The glacier, heavy and powerful, planes, polishes, and reshapes the surface over which it travels, or the walls with which it comes in contact. Most of the lake-basins were gouged out by glaciers. Mountain-ranges have been worn down to hills or plains; cañons and depressions have been filled, and extensive areas overlaid with ground-up rocky material. The gentle snowflake has been the earth's chief maker of scenery and soil. ”

“ The glaciers of a region do not by any means end at a uniform height above sea level. Each terminates where its supply is balanced by melting. Those therefore which are fed by the largest and deepest névés and those also which are best protected from the sun by a northward exposure or by the depth of their inclosing valleys flow to lower levels than those whose supply is less and whose exposure to the sun is greater. ”

“ Instances are known where glaciers have advanced over deposits of sand and gravel without disturbing them to any notable degree. Like a river, a glacier does not everywhere erode. In places it leaves its bed undisturbed and in places aggrades it by deposits of the ground moraine.
CIRQUES. Valley glaciers commonly head as we have seen, in broad amphitheaters deeply filled with snow and ice. On mountains now destitute of glaciers, but whose glaciation shows that they have supported glaciers in the past, there are found similar crescentic hollows with high, precipitous walls and glaciated floors. ”

“ Conditions of glacier formation. The condition of the great accumulation of snow to which glaciers are due—that more or less of each winter’s snow should be left over unmelted and unevaporated to the next—is fully met in the Alps. There is abundant moisture brought by the winds from neighboring seas. The currents of moist air driven up the mountain slopes are cooled by their own expansion as they rise, and the moisture which they contain is condensed at a temperature at or below 32° F., and therefore is precipitated in the form of snow. ”

“ Showing the rough texture of the surface of a Glacier below the Snow-line.
Many thousands of years ago there were glaciers in Scotland and England. We are certain of this, as glaciers scratch and polish the rocks they pass 13 over as does nothing else. Stones are frozen into the ice, and it holds them and uses them as we might hold and use a sharply-pointed instrument, scratching the rock over which the mighty mass is slowly passing. In addition to the scratches, the ice polishes the rock till it is quite smooth, writing upon it in characters never to be effaced the history of past events. ”