avalanche

Fall or flow of a mass of snow and ice down a steep slope under the force of gravity. Avalanches occur because of the unstable nature of snow masses in mountain areas.

Changes of temperature, sudden sound, or earth-borne vibrations may trigger an avalanche, particularly on slopes of more than 35°. The snow compacts into ice as it moves, and rocks may be carried along, adding to the damage caused.

Avalanches leave slide tracks, long gouges down the mountainside that can be up to 1 km/0.6 mi long and 100 m/330 ft wide. These slides have a similar beneficial effect on biodiversity as do forest fires, clearing the land of snow and mature mountain forest and so enabling plants and shrubs that cannot grow in shade, to recolonize and creating wildlife corridors.

There were at least 30 deaths caused through avalanches in the USA and Canada in 1998.

Avalanches are particularly hazardous to people in ski resort areas such as the French Alps. In 1991 a massive avalanche considerably altered the shape of Mount Cook in New Zealand.

Avalanche

In World War II, codename for the Allied landings at Salerno, Italy, September 1943.