หิมะถล่ม

thumb|upright=1.25|A powder snow avalanche in the Himalayas near [[Mount Everest]] An avalanche is a rapid flow of snow down a slope, such as a hill or mountain. Avalanches can be triggered spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, other animals, and earthquakes. Primarily composed of flowing snow and air, large avalanches have the capability to capture and move ice, rocks, and trees.