Glacière

“ A high altitude above the sea; a decided drop into the interior of the mountain; absence of all draught; protection against all warm and moist winds, therefore the opening to north and east. He also says about the glacière on the Pograca: that it is in shadow; that the thick forest round the mouth keeps the temperature down; that it begins to freeze below when it does above; that the cold remains there into the spring; and that the water from rain or other sources, which flows into the cave, must freeze there, and the ice form in greater quantities than the heat of summer can melt away. ”

“ It was now getting rather late, considering the journey one of us had yet to perform, and we walked quickly away from the glacière, agreeing that it was not improbable that in that part of the Jura there might be many hidden caves containing more or less ice, with no entrance from the world outside, except the fissures which afford a way for the water. The entrance to this cave was so small, that the same physical effect might well be produced by one or two cracks in the rock, such as every one is well acquainted with who has walked on the fissured limestone summits of the lower mountains ”

“ See B. Schwalbe, Ueber Eishöhlen und Eislöcher, page 56.
There are many facts, however, which militate against the compressed air theory as applied to caves. Almost all caves receive some drip through fissures, and yet there are many thousands of caves which never contain ice, and whose temperature scarcely varies the year round. Especially against the theory is the fact that glacière caves are never known in hot countries. If the theory were correct we should, for instance, sometimes find ice in such caves as those of Yucatan described by Mr. ”

“ Glaciers are formed by thawing of the exposed snow on top of the huge deposits, the water trickling down through the moss, and freezing solidly. Gradually, through continued thawing and freezing, the whole drift is changed into a field of ice. The first sign of movement comes when the mass of ice breaks away from the cliffs at its upper edges. There is an infinitesimal downward sagging, as with incredible deliberation it moves on with its cargo of rock and sand. But, slowly as it moves, its power is overawing. A glacier is the embodiment of irresistible force. ”

“ 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. ”

“ The surface of the glacier above is not smooth and glassy like the ice of a freshly-frozen river or pond; but is white, like a field of snow. [Pg 183] This appearance is produced in part by the snow which falls upon the glacier, and in part by the melting of the surface of the ice by the sun. From this latter cause, too, the surface of the glacier is covered, in a summer's day, with streams of water, which flow, like little brooks, in long and winding channels which they themselves have worn, until at length they reach some fissure, or crevasse, into which they fall and disappear. ”

“ 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. ”

“ These are driven onwards by the irresistible stream of solid ice; and when they arrive at a declivity of the mountain, sufficiently rapid, roll down, scattering ruin. I saw one of these rocks which had descended in the spring, (winter here is the season of silence and safety) which measured forty feet in every direction.
The verge of a glacier, like that of Boisson, presents the most vivid image of desolation that it is possible to conceive. No one dares to approach it; for the enormous pinnacles of ice which perpetually fall, are perpetually reproduced. ”

“ 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. ”

“ Waves are formed in the surface ice of the glacier because surface ice moves faster than the main mass beneath. On the bordering mountain walls the ice rises into still greater waves "foaming about the feet of the dark central crests like the surf of enormous breakers." And this great, still image of the parent sea, from which the air currents carried the moisture that made it, has eddies and whirlpools, and like the troubled sea, "whose waters cast up mire and dirt," the glacier, where it swirls along its shores, works pebbles and dirt to the surface. ”

“ GLACIER STREAM.
Pulling around to the west side of the glacier, I clambered up a steep declivity over a pile of mud and rock, which the expanding and moving ice had pushed out from its bed. Once at the top of this yielding slope, the eye was met by a perfect forest of spires; but it was not easy to get on the glacier itself. Along its margin, half in mud and rock and half in ice, a torrent of dirty water came tearing along at a furious pace, disclosing the laminated structure of the ice in a very beautiful manner ”

“ I found it impossible to distinguish the glacial ice from perpetual snow; the larger beds of snow where presenting a flat surface, being generally drifts collected in hollows, or accumulations that have fallen from above: when these accumulations rest on slopes they become converted into ice, and obeying the laws of fluidity, flow downwards as glaciers. I boiled water at the most advantageous position I could select, and obtained an elevation of 16,522 feet.* [Temperature of boiling water, 183 degrees, air 35 degrees.] ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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 ”

“ 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. ”

“ Among the snowfields, however, the pressure is immensely greater than yours; the air is more and more pressed out, and at last the snow becomes clear transparent ice.
A glacier, then, is a river, not of water, but of ice, coming down from the snow-fields. It descends sometimes a long way below the snow-line, creeping down very slowly along the valley which it covers from side to side. Its surface all the time is melting during the day in summer, and streams of clear water are gushing along the ice, though, when night comes, these streams freeze. ”

“ 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. ”

“ Well, many glaciers, after quitting the snow-beds by which they are fed, suddenly find themselves at the top of a precipice. Under these circumstances, as they are unable to stand still, there is but one thing for them to do, viz., go over; and as ice, though plastic, is by no means so to the extent that treacle—to which glacier ice has so often been likened—is, it is obvious that a slice will break off the advancing [Pg 88] tongue of the glacier, and come thundering down the rocks, to form material for another glacier below, or, if the quantity is insufficient, to melt gradually away. ”

“ More than once I have seen extremely steeply sloping glaciers, which were terminated abruptly by a lofty precipice, at the bottom of which huge piles of boulders and occasional icy fragments sufficiently indicated the forward motion of the ice; at other times, the slope of the valley in which the glacier lies again becoming gentle, the ice ceases to be fissured and rugged, and is capable of being walked on without difficulty. ”

“ The deposits from floating ice may contain marine shells. Those of glaciers cannot, except where, as in Greenland and Spitzbergen, glaciers push their moraines out into the sea.
6. It is of the nature of glaciers to flow in the deepest ravines they can find, and such ravines drain the ice of extensive areas of mountain land. Floating ice, on the contrary, acts with greatest ease on flat surfaces or slight elevations in the sea bottom.
7. Glaciers must descend slopes and must be backed by large supplies of perennial snow. ”

“ The features of a glacier trough depend much on the length of time the preexisting valley was occupied with ice. During the infancy of a glacier, we may believe, the spurs of the valley which it fills are but little blunted and its bed is but little broken by steps. In youth the glacier develops icefalls, as a [141] river in youth develops waterfalls, and its bed becomes terraced with great stairs. The mature glacier, like the mature river, has effaced its falls and smoothed its bed to grade. ”

“ 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. ”

“ 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. ”

“ 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. ”