Glacières; or, Freezing Caverns

by Edwin Swift Balch

If we look first at the mode of formation of overground perennial ice, that is, of the ice of glaciers and of rock gorges; and then at the evidences of the mode of formation of underground perennial ice, in boulder heaps, wells and caves; we will soon see that the transitions between them are gentle in character and that there is nothing unnatural about the formation of the ice in glacières.

Glaciers.—Everyone now knows the main characteristics of glaciers. They are formed in parts of the earth where the land or the mountains reach to the region of perpetual snow. The snows fall from the sky, and accumulate into a snow cap, which by its own weight and by melting and regelation, gradually changes to ice. This, by the laws of gravitation, descends to lower levels, and in mountain valleys extends sometimes far below the snow line into the region of cultivated fields. These valley prolongations of the perpetual snow caps are the glaciers. The important point to notice here, is that the formation of glaciers is originally entirely due to the precipitation of moisture by cold in the upper portions; while the destruction of glaciers is due to the action of heat melting the ice in the lower portions, where they disappear in the shape of streams of running water. It is, therefore, not surprising that the greatest glaciers are found in the Arctic and Antarctic regions and in the highest mountain ranges; and that in the tropics glaciers are either wanting or exceedingly small.

Gorges and Troughs.—Gorges and gullies, where ice remains over, are a transitional form between glaciers and glacières. In many mountain ravines or canyons, the enduring snow consists principally of the avalanches which have fallen from the heights above during the winter and solidified in the bottom of the ravines. Freezing gorges proper, however, are not dependent on avalanches for their supply, but they receive the accretions to their ice directly from the winter snows. These fall into the gorge itself and by melting and regelation gradually solidify into a mass of ice which, when well sheltered against sun and wind, remains over sometimes till the following winter. By their mode of formation, therefore, it is evident that the ice in these gorges has some of the characteristics of glaciers; that it is due to the same prime causes as the ice of glaciers or the ice on ponds and rivers, namely the cold of winter; and in fact, it is not far wrong to consider these gorges as miniature glaciers.

Freezing gorges, however, show, also, certain degrees of kinship to freezing caverns and taluses, principally in the protection afforded to the ice against external destructive influences. The ice is almost always found in positions where it receives little, if any, of the direct rays of the sun and, also, where it is scarcely, if at all, exposed to any winds. The sides of the fissures and surrounding trees generally afford the necessary protection. Some of the forms which the ice assumes in gorges, such as long pendent icicles, are also more characteristic of underground than of overground ice.

The freezing troughs or basins found in Siberia are evidently closely related to gorges, and the fact that the ice is found in less sheltered places may be explained by the high northerly latitudes of these troughs, in general between fifty-seven and sixty degrees.

The Winter’s Cold Theory.—The places where ice is found underground differ in one important respect from gullies and troughs, and that is, in the fact that above the ice there is rock or soil, which, in true caves, takes the form of a roof. This causes some important distinctions between overground and underground perennial ice. It means that the ice is formed directly in the caves, and that it is genuine subterranean ice, and not, except perhaps near the entrance, solidified snow. The roof, while not admitting the winter snows, is, however, a protection against warm summer rains, and, of course, entirely cuts off radiation from the sky. If, therefore, it keeps out some cold, it also acts as a protector against heat.

That the cold of winter is the source of the cold which produces the ice which forms underground, and that it is through its influence, with the assistance of certain secondary causes, that some caves are converted into what are practically natural ice houses, seems to me the true explanation of the phenomenon of subterranean ice, not only since it is the simple and obvious explanation, but also because all the facts, so far as I have myself observed, are in accord with this theory.[56]

[56] Among those who have written or said that the cold of winter plays a more or less important part in the formation of subterranean ice may be mentioned: Poissenot, 1586; Gollut, 1592; DeBoz, 1726; Nagel, 1747; Cossigny, 1750; Jars, 1774; Hacquet, 1778; Girod-Chantrans, 1783; Hablizl, 1788; Prévost, 1789; Townson, 1797; Humboldt, 1814; Dearborn, 1822; Deluc, 1822; Dewey, 1822; Lee, 1824; Reich, 1834; Hayden, 1843; Guyot, 1856; Rogers, 1856; Petruzzi, 1857; Smyth, 1858; Hager, 1861; Thury, 1861; Browne, 1865; Raymond, 1869; Krenner, 1874; Ritchie, 1879; Benedict, 1881; Schwalbe, 1881; Fugger, 1883; Trouillet, 1885; Girardot, 1886; Russell, 1890; Martel, 1892; Krauss, 1894; Lohmann, 1895; Balch, 1896; Cvijic, 1896; Butler, 1898; Kovarik, 1898; Cranmer, 1899.

To form subterranean ice, just as to form any other ice, two things are necessary: the first is cold, the second is water. Cold is supplied by the cold air of winter, and water must in some manner find its way into the cave while the cold air is there.

The process is as follows: The cold air of winter sinks into and permeates the cave, and in course of time freezes up all the water which, in the shape of melting snow or cold winter rain or spring water, finds its way in; and once ice is formed it remains long after ice in the surrounding open country has melted away, because heat penetrates with difficulty into the cave. The only effect of the heat of summer is to melt the ice.