A mass of snow (perhaps containing ice and rocks) moving rapidly down a steep mountain slope.
Avalanches may be characterized as loose and turbulent, or slab; either type may be dry or wet according to the nature of the snow forming it, although dry snow usually forms loose avalanches and wet snow forms slabs. A large avalanche sweeps a current of air along with and in front of it as an avalanche wind, which supplements its already tremendous destructive force.
A mass of earth material (soil, rock, etc.) moving rapidly down a steep slope.