An avalanche is a flow of snow, ice or rock down a mountainside. It is a very sudden event, and can move very fast (about up to 200 km per hour).
There are different kinds of avalanches. Some of them are:
Rock avalanches: They consist of the movement of large segments of shattered rocks.
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Ice avalanches: They occur in the vicinity of a glacier, where huge blocks of ice slide.
Debris avalanches: They contain a variety of unconsolidated materials, such as loose stones and soil.
