avalanche

The sudden fall or slide of a large mass of material down the side of a mountain. Avalanches may contain snow, ice, rock, soil, or a mixture of these materials. Avalanches can be triggered by changes in temperature, by sound vibrations, or by vibrations in the earth itself.

A process resulting in the production of large numbers of ionized particles, in which electrons or ions collide with molecules, with each collision itself producing an additional electron or ion that in turn collides with other molecules. Avalanches are what generate the pulses of electric current that are registered by Geiger counters.