Avalanches

Avalanches (Fr., from avalier, 'to descend') are masses of snow or ice that slide or roll down the declivities of high mountains, and often occasion great devastation. They have various names, according to their nature. Drift or powder avalanches (Ger. Staub-lawinen) consist of snow, which, loose and dry from strong frost, once set in motion by the wind, accumulates in its descent, and comes suddenly into the valley in an overwhelming dust-cloud. Avalanches of this kind occur chiefly in winter, and are dangerous on account of their suddenness, suffocating men and animals, and overturning houses by the compression of the air which they cause. Another kind of avalanche resembles a landslide. When the snow begins to melt in spring, the soil beneath becomes loose and slippery; and the snow slides down the declivity by its own weight, carrying with it soil, trees, and rocks. The greatest danger is where elevated tracts of moderate declivity are separated from the valleys by precipitous walls of rock; the softened snow of spring beginning to roll or slide on these slopes, is hurled over the precipices with fearful force into the valleys. The very wind caused by them prostrates forests and houses. Ice avalanches are those that are seen and heard in summer thundering down the steep—e.g. of the Jungfrau. They consist of masses of ice that detach themselves from the glaciers in the upper regions. They are most common in July, August, and September. Nine great Alpine avalanches, which cost 447 lives, are on record between 1518 and 1879, the most destructive being one of 1827, which swept away half the village of Biel, in the Upper Valais, with 88 inhabitants. Sudden avalanches, larger or smaller, constitute one of the special dangers of Alpine climbing. See Coaz, Die Lawinen der Schweizeralpen (Bern, 1881). See GLACIER, ICE, ALPINE CLUB.