An avalanche is when a mass of snow quickly or rapidly slides down a slope of a mountain. It happens most of the time by natural causes such as precipitation/snow and wind drifting snow. They are caused by the pulling gravity and or from a skier applying force on a weak layer of the snow cover, triggering the avalanche.  Most avalanches happen on the backsides of mountains where snowboarders and skiers are not allowed to go. Also on timberlines that face away from prevailing winds.

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