Ice crevasse

“ Crevasse—A fissure or crack formed in a snow-field or glacier; caused by non-elasticity of the ice when moving down the uneven surface of its rocky bed. Longitudinal crevasses are formed in the direction of the flow ”

“ The depth as well as the length of this glacier remains somewhat problematical, and indeed all the estimates in so cursory a survey must be considered as approximations rather than positive results. The glazed surface of the ice is an impediment to any examination from the upper side. It would be impossible to spring from brink to brink of a crevasse, as is so constantly done by explorers of Alpine glaciers where the edges of the cracks are often snowy or granular. Here the edges of the crevasses are sharp and hard, and to spring across one of any size would be almost certain death. ”

“ MORAINE OF VICTORIA GLACIER
At a sudden descent, where a river would leap as a waterfall, a glacier simply breaks across in what are called “CREVASSES,” fissures which may be several feet wide and hundreds of feet long, going down to blue black depths appalling to the inexperienced climber. As the glacier advances these crevasse are bent out of shape and may be crossed by fresh crevasses, splitting up the ice into wild lumps and pinnacles called “SERACS.” Seen from a distance across some valley such an ice fall looks like a cascade or a violent rapid covered with breakers. ”

“ In the lower part of a glacier the crevasses are open. Above the snow-line they are frequently hidden by arched-over accumulations of winter snow. The detection of hidden crevasses requires care and experience. After a fresh fall of snow they can only be detected by sounding with the pole of the ice-axe, or by looking to right and left where the open extension of a partially hidden crevasse may be obvious. The safeguard against accident is the rope, and no one should ever cross a snow-covered glacier unless roped to one, or better to two, companions. ”

“ Ice, unlike water, is brittle, so it splits up into crevasses whenever the glacier flows over a steep or uneven 10 rocky bed. High up, where snow still lies, these chasms in the ice are often bridged over, and if a person ventures on one of these snow bridges it may break, and he may fall down the crevasse, which may be so deep that no bottom can be found to it. He is then either killed by the fall or frozen to death. If, as I have explained before, several climbers are roped together, they form a long string, like the tail of a kite, and not more than one is likely to break through at a time. ”

“ In this case we had fairly good going, but got into a perfect mass of crevasses into which we all continually fell; mostly one foot, but often two, and occasionally we went down altogether, some to the length of their harness to be hauled out with the Alpine rope. Most of them could be seen by the strip of snow on the blue ice. They were often too wide to jump though, and the only thing was to plant your feet on the bridge and try not to tread heavily. As a rule the centre of a bridged crevasse is the safest place, the rotten places are at the edges. ”

“ Here you must cross it very nearly on a level, and then skirt down its further side between ice and rock for a few feet before you come to a suitable place for the crossing of the big crevasse below you; and then a short slide down old avalanche débris shoots you deliciously into the sun again. The crossing of the glacier in the steps cut by the numerous parties who have passed on previous days is an extremely simple affair. But you must not hurry, for a slip could not be checked, and would probably finish in the before-mentioned crevasse. ”

“ Crevasses are a glacier’s most awesome features and are a constant hazard for climbers. They form where adjacent parts of a glacier are moving at different speeds. Some of Mount Rainier’s glaciers may be flowing at a speed of several thousand feet per year along their centers but at a much slower rate along their margins. This unequal rate of flow produces stresses in the ice that cause it to break. Groups of crevasses often form where the glacier flows over a steep place in its bed. The ice moves faster here, and pulls apart, and a crevasse is formed. ”

“ All the icebergs and floes here had come from latitudes farther north, and, if we may so express it, lived upon the cold they had brought with them. The whole of the southern portion of the Arctic Ocean was most imperfectly frozen, and a warm rain was falling, which hastened the dissolution of what ice there was.
On the 24th November the advance of the travellers was absolutely arrested by a crevasse full of rough water strewn with small icicles-a crevasse not more than a hundred feet wide, it is true, but probably many miles long. ”

“ It appears that water, produced by the thawing of the ice and snow, forms streams on the surface of the glacier, which, having gathered into their courses a certain amount of morainic débris, are finally cast down a crevasse as a swirling cascade or moulin. The sides of the crevasse are abraded, and a vertical shaft is formed in the ice. The erosion may be continued into the bed of the glacier, and, the ice having left the district, the giant’s kettle so formed is seen as an empty shaft, or as a pipe filled with gravel, sand or boulders. ”

“ The deep, irregular crevasses common to most glaciers were bridged by crust formations of the recent autumnal snows. These bridges were so uniform with the general surface of the glacier as to make their detection almost impossible. Although Sonntag moved with great caution and continually tested the snow with his ice-chisel, which replaced the Alpine alpenstock, he broke through one bridge. Most fortunately the fall was at a place where the fissure was only about three feet wide, opening either way into a broad crevasse. ”

“ At best the surface was very bumpy, and I foresaw a bad time coming for the sledges. The ice phenomena would have struck any Alpine climber as curious. Every year there are added, even to the central and crevassed portion of an arctic glacier, accumulations of ice formed by the thawing and re-freezing of the winter snow, and these patchwork additions take the most unexpected forms. For instance, a crevasse that happens to be full of water will be roofed over with ice a few feet thick. If the rest of the water is then drained off a tunnel is formed, across which again crevasses may open. ”

“ As the glacier moves along, it often cracks for a considerable way across its surface, and this crack widens and widens, until at last it becomes a great gaping chasm, or crevasse as it is called, so that you can look down it right to the bottom of the glacier. Into these crevasses large blocks of rock fall, and when the chasm is closed again as the ice presses on, these masses are frozen firmly into the bottom of the glacier, much in the same way as a steel cutter is fixed in the bottom of a plane. ”

“ But since we are on the ice we may as well take advantage of it, and explore it a little. I confess all these crackings and detonations inspire me with some doubt as to its solidity!"
Erik and his adopted father had not gone more than three hundred feet from their depot of provisions before they were stopped short by a gigantic crevasse which lay open at their feet. To cross it would have required long poles, with which they had neglected to supply themselves. They were therefore compelled to walk beside it obliquely toward the west, in order to see how far it reached. ”

“ All around us is snow, either freshly fallen or merging into névé. We begin to walk down, and at first, upon the steeper slopes, cross a few large crevasses and bergschrunds by means of snow bridges; then, as the incline becomes less steep, we walk for six miles or so upon a smooth surface of névé, or perchance knee-deep in fresh snow, and scarcely a crevasse exists. At the beginning of the great turn we gradually leave the névé and find ourselves upon hard, white ice, and soon transverse crevasses appear ”

“ The open crevasses were not the dangerous ones; the whole glacier was crisscrossed by crevasses completely covered with snow. In bright weather it was often possible to detect them by a slight depression in the surface or by a faint, shadowy difference in tint, but in the half-light of cloudy and misty weather these signs failed, and there was no safety but in the ceaseless prodding of the pole. The ice-axe will not serve—one cannot reach far enough forward with it for safety, and the incessant stooping is an unnecessary added fatigue. ”

“ Snow-crystals, the flowers of the mountain clouds, are frail, beautiful things, but terrible when flying on storm-winds in darkening, benumbing swarms, or, when welded together into glaciers full of deadly crevasses. Watching the weather, I sauntered about on the crystal sea. For a mile or two out I found the ice remarkably safe. The marginal crevasses were mostly narrow, while the few wider ones were easily avoided by passing around them, and the clouds began to open here and there.
Thus encouraged, I at last pushed out for the other side; for Nature can make us do anything she likes. ”

“ When one considers the myriads of crevasses which there are in any glacier, and the incessant opening and closing up that goes forward, it is easy to see that a large proportion of the veins of pure ice which constitute the veined structure of glaciers must be considered as the scars of healed crevasses. ”

“ Later in the season I made an excursion far out on the Malaspina glacier from the extreme southern end of the Hitchcock range, and became acquainted with many of its peculiarities. Its surface, instead of being a smooth snow-field, as it appears from a distance, is roughened by thousands of crevasses, many of which are filled with clear, blue water. Over hundreds of square miles the surface appears as if a giant plow had passed over it, leaving the ice furrowed with crevasses. The crevasses are not broad; usually one can cross them at a bound. ”

“ The crevasses, at times all lined with the purest, smoothest snow, open up like great alcoves, hung in clouds of ice with delicate ornaments thrown on them by the wind. They modify and change every spring, when the winter’s accumulation of snow melts under the action of the heat, and the frost of the nights incorporates it with the glacier. ”

“ Crevasses and séracs.—Prominent surface indications of glacier movement are found in the open cracks or crevasses, which are the marks of its yielding to tensional stresses. Crevasses are apt to run either directly across the glacier, wherever there is a steep descent upon its bed, or diagonally, running in from the margin and directed up-glacier (r, r, r, of Fig. 416) , though they occasionally run longitudinally with the glacier when there is a rock terrace at the side of the valley beneath the ice. ”

“ Where a glacier, straight or crooked, has one of its sides unsupported by a rock wall, and is therefore falling away at its own edge, or where its marginal and transverse crevasses have joined hands, a disagreeable system of curving crevasses must be expected. This is difficult to prospect, and dangerous to unravel if it is under snow. To locate the direction of a ‘scimitar’ crevasse at one point, and avoid it or cross it correctly, does not protect us against its later loop of unexpected trespass upon our route. ”

“ As the decades pass, its level is greatly lowered by the melting of the ice. More and more, earth and rocks accumulate upon the surface, as it travels onward, and are scattered over it by the rains and melting snow. At last, in its old age, when far down its canyon, the glacier is completely hidden, save where crevasses reveal the ice. Only at its snout, where it breaks off, as a rule, in a high wall of ice, do we realize how huge a volume and weight it must have, far above toward its sources, or why so many of the crevasses on the upper ice fields seem almost bottomless. ”

“ The crevasses on such slopes generally run at right angles to the direction in which the snow is moving. On looking down on such a surface, the breaks look like long clear-cut gashes which have stretched open in the center, but taper to a sharp point at each end. The ability of the névé ice to stretch to a limited extent is thus clearly shown. ”

“ There are two golden rules for avoiding a drop into a crevasse: firstly, keep off glaciers or of those parts of any glacier where crevasses are known to be numerous, deep, long, and wide; secondly, if called [26] upon to run over a glacier that is crevassed, use the rope, but use it properly—that is, bring its full length into use, take off your ski, and proceed exactly as you would do in summer by sounding the snow and crossing bridged crevasses one after another. It is absurd to mix summer and winter craft; they are distinct. ”

“ Still ascending, avoiding the crevasses by a zigzag path, we at last reach the last one, or what might more properly be called the first crevasse. This crevasse is formed by the first breaking off of the snow as it begins to slide down the mountain. The upper side is often a perpendicular wall of hard snow from ten to fifty feet high. This same crevasse, for it extends half way round the mountain, prevented our further progress on two previous occasions, when attempting to reach the summit from the northeast slope. ”

“ In fact the termination of 203 the glacier resembles somewhat the hoof of a horse, or rather that of a rhinoceros, the divided portions being formed by crevasses, while long thin projections of ice spread out between. It is a very easy matter to get on the glacier, and quite safe to proceed a long way on its smooth surface. We had some fine glimpses of crevasses so deep that it was impossible to see the bottom, while the rich blue color of the ice everywhere revealed to us marvels of colored grottoes and hollow-sounding caverns, their sides dripping with the surface waters. ”