Ice cap

“ 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. ”

“ Land Ice Ice of land origin is formed on land by the freezing of freshwater or the compacting of snow as layer upon layer adds to the pressure on that beneath. Under great pressure, ice becomes slightly plastic, and is forced downward along an inclined surface. If a large area is relatively flat, as on the Antarctic plateau, or if the outward flow is obstructed, as on Greenland, an ice cap forms and remains essentially permanent. ”

“ Water-transported material, he argued, would not cause straight furrows and scratches, and the theory that such might be due to drifting icebergs was rejected on the ground that existing bergs were insufficient, and to produce such as were would necessitate a period of cold sufficient for his hypothetical polar ice-cap. He pointed out that the northern erratics were rounded and widespread; that the highest hills were scratched and polished to their summits, while to the south the mountain tops had protruded above the ice-sheet and supplied the glaciers with their load of angular boulders. ”

“ It has been demonstrated that an ice-cap resting several thousand years over any considerable portion of the surface would so reduce the subjacent temperature of the earth that for many centuries after the disappearance of the ice, a decrease of temperature would be discovered in penetrating downward. Even centuries later, so much cold would still remain within the earth, that the rate of increase of temperature would be less than if the ice-cap had not existed ”

“ In fact deluded, as scientific men often are, by language, they embraced the thought of a “returning Ice Cap,” which would successfully force its way from the Baltic to the Mediterranean. They nervously began measurements of the Alpine glaciers, took temperatures, wandered up in the higher regions of the atmosphere in balloons, sounded the floor of the ocean, established meteorological stations everywhere, and became so excited and convinced that they were happily on hand at a critical geological juncture, that they succeeded in supplying a technical ground for panic. ”

“ No one now believes in the former existence of a polar ice cap, and possibly when the irresistible force of ice-dammed rivers has been fully realized, the estimated area of glaciation may be considerably reduced. ”

“ In the interior the surface of the inland ice is composed of dry snow which never melts, and is constantly packed and worked smooth by the winds. It extends as a completely even plain of snow, with long, almost imperceptible, undulations or waves, at a height of 7000 to 10,000 ft., obliterating the features of the underlying land, the mountains and valleys of which are completely interred. Over the deepest valleys of the land in the interior this ice-cap must be at least 6000 or 7000 ft. ”

“ Recent studies by Canadian geologists have shown that one of the highest summits of the ice cap must have been located some distance west of Hudson Bay, and that another, the one which glaciated the lake region, was in Labrador, to the east of the same body of water. From these points the ice moved in spreading fans both northward toward the Arctic Ocean and southward toward the States, and always approached the margins at the moraines in a direction at right angles to their extent. ”

“ The ice rises steadily from the edge to the center. At that center it cannot be less than twelve miles in thickness—twice as thick as Mount Everest is high. Southern latitudes are growing warmer, and this ice cap is known to be cracking. Suppose it splits. Imagine the gigantic mass of water and ice that will come sweeping up north over the oceans and continents of the earth! Where, then, will the last man breathe his final gasp? ”

“ Nothing is more likely than that, as the great Laurentian ice-cap of America was deeper and extended further than the Scandinavian ice-cap of Europe, it may have taken longer to melt the larger accumulation of ice, and thus postponed the establishment of post-glacial conditions and river-drainage to a later period than in the warmer and more insular climate of Europe. It is a matter of everyday observation, that the larger a snowball is the longer it takes to melt, and that when the mass is large it requires a long time to make it disappear even after mild weather has set in. ”

“ It so happens, however, that the fluctuating polar ice cap hovers over the single narrow bridge to the New World and the part it has played in the story of the primates is truly wonderful. The reader familiar with the recent literature on Paleolithic man need not be told that the pulsation of this ice cap is proving the only reliable time clock for human culture. At four intervals, at least, this ice field crept down into North America and into the Old World, each time greatly modifying the distribution of mammalian life. ”

“ Before I resorted to this, my cap was full of frozen water, stiff and uncomfortable, all the condensation turning to ice the moment I uncovered. When the weather is very cold, I up hood; when colder, say -40°, with a middling breeze—quite cold enough, I assure you—I wear an elastic silk night-cap in addition, one of a pair forced on me by a certain brother of mine as I was leaving New York, drawn over my head and face, and lined with a mask of wolf-skin. ”

“ It has been estimated from the great size and abundance of these icebergs, that in the interior of the great Antarctic continent the ice may be twenty miles or more thick, and in Greenland the great interior ice-cap rises in a dome to at least 9000 or 10,000 feet above the sea-level, a great part of which is solid ice, while during the great glacial period it was certainly very much thicker. ”

“ The Antarctic ice-cap was discovered and explored by Captain Scott, who penetrated into its solitudes for two hundred miles from the mountain range. Dr Mawson has also examined it from another direction. There is little or no interest in travelling over its monotonous surface, but numerous borings would reveal its depth and507 solid contents, as suggested by the late Sir John Murray. The greatest interest connected with the Antarctic ice-cap is to be found in the study of its glaciers, and of its edges, possibly mighty cliffs like the Ross piedmont, whence the vast icebergs are discharged. ”

“ Supposing the average land surface under the ice to rise to 2000 ft., the thickness of the ice-cap would be nearly 7000 ft. The excavating power of the glaciers is enormous, and the pressure causing the melting of the snow and the discharge of an enormous quantity of water into the sea, counteracts any increase above caused by the excessive precipitation occurring from the warm winds blowing from the sea. ”

“ In consequence, the moist air which reaches the south frigid zone is greatly in excess of that which reaches the northern zone of cold, and the snow-fall there must be very much more considerable. It is estimated that the south polar ice-cap can not be less than three miles and may be twelve miles in height. The thrust of this vast ice mountain upon the viscid material beneath it is necessarily enormous, and a lofty ice-cliff is pushed off the land at a rate of not less than a quarter of a mile annually, and this around a circle of great extent. ”

“ I have always limited my parties to the number absolutely necessary for the work I had laid out, believing that every addition means an element of danger and failure. My reconnaissance of the Greenland inland ice in 1886, resulting in the penetration of the ice-cap to a greater distance than ever before by a white man, and the attainment of the greatest elevation on the ice-cap, was made with only one companion. ”

“ The most recent idea is, that the land about the pole consists of a cluster of low islands, rising but little above the sea-level, but united by masses of ice. The gradual accumulation of snow for centuries has raised a cap, as before stated, seven miles thick, and from this cap the ice flows away in all directions, forced onward by the pressure of the enormous mass behind. ”

“ These ice-caps covering great regions are by far the most important types. Between these “polar” or “continental glaciers” and the “alpine” type there are many grades. Smaller detached ice-caps may rest upon high plateaus as in Iceland, or several tongues of ice coming down neighbouring valleys may splay out into convergent lobes on lower ground and form a “piedmont glacier” such as the Malaspina Glacier in Alaska. When the snow-field lies in a small depression the glacier may remain suspended in the hollow and advance no farther than the edge of the snow-field. ”

“ Under these conditions, all the ice in the zone of constant temperature, except that at its bottom, must be permanently below the melting-point, but it is perhaps worthy of especial note that much of it is but little below. In alpine glaciers the part of the ice affected by this constant low temperature (below freezing) is presumed to be chiefly that which lies beneath the snow-fields. In polar glaciers the low temperature probably prevails beneath the surface, not only throughout the great ice-caps, but also in the marginal glaciers which descend from them. ”

“ Standing on our little deck, and looking out on the floe, we had the strange spectacle of an undulating solidity, a propagated wave borne in swell-like ridges, as if our ice was a carpet shaken by Titans. I can not convey the effect of this sublime spectacle. The ice, broken into polyhedric masses, gave at a few hundred yards no indications to the eye of the lines of separation; besides which, the infiltration of salt water had no doubt increased the plasticity of the material. ”

“ The strong floe of ice-table under ice-table, and hummock upon hummock, makes our position one of nearly complete solidity. We are glued up in ice; and to liberate us, some fearful disruption must take place. Twenty-five feet of solid ice is no feeble matrix, for a brig drawing but ten. Yet the water is wider, and still widening around us; so that now we hold on—that is, our floe holds on, to the great mass to the north of us, like a little peninsular cape.
“To the south every thing is in drifting motion—water, sludge, frost-smoke—but no seals. ”

“ In the course of a tramp to-day about noon, the thermometer standing at -18°, I came across a wonderful instance of the yielding elasticity of ice under intense pressure. About two hundred yards from the brig, on her starboard quarter, was an unbroken plain of level ice, which before our recent break-up used to form one of my daily walks. It measured one hundred and thirty paces in its longer diameter and eighty-five in its shorter, and its thickness I ascertained this morning was over five feet. ”

“ After sailing along the Siberian coast for a short distance, the Jeannette bade farewell to land and started on her perilous journey.
In the Arctic regions the ice is divided into what is known as young ice and the pack. Young ice is that which is forming all the time. It is thin at first, and vessels can usually cut their way through. The pack is the old ice which has been formed for many years, and is composed of large pieces, called floes, which are often thirty or forty feet thick and extend over a great surface both above and below the water. ”

“ Daily the sun got lower; so did the mercury in the thermometer; and often for days there was no sight of the former because of flying snow and the deep haze of frost-fog. The ice set more and more firmly about the Bowhead, and the pack which ground and crushed against the edge of the shore ice outside the headland no longer made any answering movement in the frozen stretch about her. The winter was upon them, and there were times when their ice igloo was put to severe tests as a frost defender. ”

“ Tempted by the overarching beauty of the sky, I started off this morning with Captain De Haven on a walk of inspection shoreward. The open water, frozen since October 2d, is now nearly two feet thick, and at this low temperature (-15°) it becomes hard and brittle as glass. Wherever the nipping has caught two of the floes, they have been driven with a force inconceivable one above the other, rising and falling until they now form a ridge fifteen or twenty feet high.
“The tension of the great field of ice over « 138 » which we passed must have been enormous. It had a sensible curvature. ”

“ A floe is a detached portion of a field; a large area of floes, closely compact together, is known as pack-ice; while drift-ice is loose ice in motion, and not so firmly welded as to prevent a ship from forcing her way through the yielding fragments.
IN AN ICE-PACK, MELVILLE BAY.
This “pack-ice,” however, is the great obstacle to Arctic exploration; and frequently it presents a barrier which no human enterprise or skill can overpass. At times, it has been found possible to cut a channel through it, or it breaks up and opens a water-way through which the bold adventurer steers. ”