Ice slope

“ The inclination of a hanging slope of snow always appears still more exaggerated as seen from in front if it lies on the face of what is mainly a rock peak. We have in such case to discover if the snow is lying on ice, or only forms a coating to the rock. If it is on ice, the lower edge of the slopes, where the snow runs out on to the rock, will generally betray a rim or broken wall of ice. To judge of the quality of such a snow surface, and of the strength of its attachment to its ice or rock sub-surface, the slopes below it must be examined, and snow, stone or water furrows looked for. ”

“ At the upper termination of nearly all highly situated ice slopes there almost invariably occurs between the rocks above, or between the ice slope and the permanent clinging ice above, a large gap or crevasse, partially filled or bridged with new snow during the winter months, but more open as the warmth of spring and summer causes the snow to melt and the ice to shrink away. ”

“ If the ice-field rests on a steeply inclined surface, like a mountain slope, the movement becomes one-sided in conformity to the slope. If the surface, otherwise plane, be affected by valleys parallel to the direction of movement, the ice in the valleys will be deeper than that on the divides between them, and its movement stronger. In the valleys, therefore, the ice will advance farther than elsewhere before being melted, and the outline of the ice will become lobate, the lobes occupying the depressions. ”

“ 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. ”

“ On the upper glacier where the slope becomes steep, the ascent is made over fields of ice and snow and ledges of glaciated rock to vantage points along- side and above the rugged and picturesque ice-fall. ”

“ There is nothing more characteristic than the ice-hill.
Imagine a slope as steep as a roof, paved with solid blocks of ice, which are subsequently frozen together by flooding with water; imagine a sledge with steel runners polished like a knife ”

“ When this river of ice comes to the edge of a precipice, or tries to crawl down a very steep cliff, it splits across and forms tottering crags of ice, which lean over more and more till they lose their balance and go crashing down the slope. Some of the ice is crushed to powder by its fall, yet many blocks generally survive, and are occasionally heaped up in such huge masses below that they form another glacier on a small scale. ”

“ As we gathered speed on our downward course, and the chisel edge of the ice-axe bit deeper into the hard névé, it sprayed our faces and necks with a miniature shower of ice. The temperature was low, and whenever the steel of the ice-axe touched one’s bare skin, it seemed to burn it like a hot iron. We all reached the bottom of the slope safely, and fired with the success of our first glissade, and finding an almost endless succession of snow slopes below us, we let ourselves go again and again, in a series of wild rushes towards the foot of the main cone. ”

“ As far as the eye can reach nothing is to be seen but snow. Now this snow must gradually accumulate, and solidify into ice, until it attains such a slope that it will move forward as a glacier. The enormous Icebergs of the Southern Ocean, moreover, show that it does so, and that the snow of the extreme south, after condensing into ice, moves slowly outward and at length forms a wall of ice, from which Icebergs, from time to time, break away. ”

“ Conditions affecting rate of movement.—The rate of glacier movement appears to depend on (1) the depth of the moving ice; (2) the slope of the surface over which it moves; (3) the slope of the upper surface of the ice; (4) the topography of the bed over which it passes; (5) the temperature; and (6) the amount of water which falls upon it or is carried to it by the drainage of its surroundings, in addition to that produced by the melting of the glacier itself. Great thickness, a steep slope, much water, smoothness of bed, and a high (for ice) temperature favor rapid movement. ”

“ With a given thickness of ice, the greater the decline of its lower surface in the direction of motion, the more rapid its progress. A rough bed, or a crooked course retards the motion of a glacier, while a smooth bottom and a straight course facilitate it.
Slope, roughness of bed, and volume affect the movement of glaciers somewhat as they affect the movement of rivers. The temperature of the water, on the other hand, has little effect on the flow of a river so long as it remains unfrozen; but the effect of temperature on the motion of ice is most important. ”

“ But returning to the point at which we started, on the subject of ice, viz., its Alpine accumulation above the snow-line. If the snow-fall there exceeds the amount that373 is thawed and evaporated, it must either go on growing upward until it reaches the highest atmospheric region from which it falls, or is formed, or it must descend somehow.
If ice can be squirted through a syringe by mere hand-pressure, we are justified in expecting that it would be forced down a hill slope, or through a gully, or across a plain, by the pressure of its own weight when the accumulation is great. ”

“ The fragments resulting from this rending process fall upon the glacier surface and are carried forward as passengers in the direction of the ice margin. They are either visible as long and narrow ridges or trains following the directions of the steepest slope (Fig. 302) , or they become buried under fresh falls of snow and only again become visible where summer melting has lowered the glacier surface in the vicinity of its margin. ”

“ It is evident that this decrease will be less rapid where the slope of ascent is gradual, from such considerations as the angle at which the sun's rays strike the slope, and the larger amount of surface which is in contact with a stratum of atmosphere of any given thickness. ”

“ As the hard snow slopes were mostly much too steep to climb, without resorting to the tedious expedient of cutting steps with an ice-axe, we kept as much as possible to the rocky arêtes. Occasionally, however, the arête would terminate upwards in a large snow slope, and in such cases we cut steps across the névé to any arête which seemed to persist for some length in an upward direction. ”

“ Where the supply of snow exceeds the loss by evaporation the surplus descends the mountain sides, slowly in the form of glaciers, or suddenly in ice-falls or in avalanches. A mass of snow may accumulate upon a steep slope and become compacted into ice by pressure, or remain loosely aggregated. ”

“ Not only do the glaciers on the Alps, in Iceland, and other mountain regions, polish and striate surfaces over which they move, but even the ice-covering of an extensive area of land with a gentle slope, such as Greenland, produces similar effects by slowly moving down to the sea shore; and it is probable, too, that the great icebergs, some of which are 4 miles in circumference, and 1800 feet high, would, when grounding and moving along the sea bottom, also polish and striate rock surfaces. The love of simplicity has, perhaps, led theorists to attribute too much to one cause. ”

“ The loose snow was shovelled away and the steps dug in the hard snow beneath, and the creepers upon our feet gave good grip in it. Thus, slowly, step by step, we descended the ridge and in an hour and a half had reached the cleavage, [Pg 124] the most critical place in the whole descent. With the least possible motion of the feet, setting them exactly in the shovelled steps, we crept like cats across this slope, thrusting the points of our axes into the holes that had been made in the ice-wall above, moving all together, the rope always taut, no one speaking a word. ”

“ Indeed, if you will look closely at the line of the retreating snow—not a straight line but a billowy one, here receding into a big bay, here stubbornly holding out a promontory of white—you will note that the crevellated edge of the vanishing snow mass is not joined to the earth at all, but forms a little overhanging cliff of ice. The melting warmth is coming up from the ground rather than from the sun in the last stage of the snow-field's flight, and underneath this tiny cliff the vegetation can be seen already pushing up to life. ”

“ Then we have the struggle and confusion which attend the encounter of the young glacier with the first obstacles. An irresistible impulse urges the still half-formed ice over the edge, and it is transformed in a moment into a maze 343 of towers and blue abysses, of walls of marble-like snow seamed with the soft veins which mark each year's fall, of crystal-roofed and fretted vaults hung with pendant icicles. ”

“ On the smooth plain of the interior no rock waste relieves the snow's dazzling whiteness; no streams of running water are seen; the silence is broken only by howling storm winds and the rustle of the surface snow which they drive before them. Sounding with long poles, explorers find that below the powdery snow of the latest snowfall lie successive layers of earlier snows, which grow more and more compact downward, and at last have altered to impenetrable ice. The ice cap formed by the accumulated snows of uncounted centuries may well be more than a mile in depth. ”

“ 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. ”

“ Occasional glimpses unfold the polish, the colors, and the graceful winding of sea-shells. A strong current in connection with the wind forces us, I am glad to say, to a more safe and comfortable distance. The last ten minutes has given us a startling illustration of the dangers of which we have been forewarned: a crack like a field-piece was followed by the falling of ice, on the opposite side of the berg, attended with a sullen roar.
We round to, and take the breeze in our faces. The ice is up the wind, square before us, and we must after it by a tack or two. ”

“ Some of the short laterals of the glaciers that drew their fountain snows from the jagged recesses of the summit are from one to two hundred feet in height, and scarce at all wasted as yet, notwithstanding the countless storms that have fallen upon them, while cool rills flow between them, watering charming gardens of arctic plants—saxifrages, larkspurs, dwarf birch, ribes, and parnassia, etc.—beautiful memories of the Ice Age, representing a once greatly extended flora. ”

“ 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. ”

“ On the glacier, a broad track, littered with blocks of ice, stretched upward in a straight line from the upper lip of the crevasse to the great ice-fall on the sky-line where the huge slabs and pinnacles of ice, twisted into monstrous shapes, like a sea suddenly frozen when a tempest was at its height, stood marshaled in serried rows. ”

“ The boulders are detached fragments, which fell from various rocky heights overhanging the ice-stream, rested on the surface of the ice-sheet, were borne along by it through hundreds of miles, and when, in the course of ages untold, the climate became milder, and the glaciers gradually shrunk and eventually disappeared, these fragments, often bearing the marks of ice-scraping, and oftener rounded by ice-action, fell to the soil beneath, and remain to this day, to bear their silent witness to the course once taken by the giant ice-stream. ”

“ But in ordinary times layers from six to eight feet deep are regularly added annually to the accumulation of snow in the higher regions,—not taking into account, of course, the heavy drifts heaped up in particular localities, but estimating the uniform average increase over wide fields. This snow is gradually transformed into more or less compact ice, passing through an intermediate condition analogous to the slosh of our roads, and in that condition chiefly occupies the upper part of the extensive troughs into which these masses descend from the loftier heights. ”

“ Icebergs are merely the broken-off ends of glaciers, which descend to the sea, or the detached fragments of icy cliffs generated on the coasts of circum-polar regions. When liberated they are carried by oceanic currents through various and often great distances, till, melted, overthrown, or stranded, they yield up the stony masses, which glaciers had brought down, or shore ice had raised up, and thus encumber the sea bed with the spoils of distant lands. ”