Avalanches can begin when an unstable mass of snow breaks away from a mountainside and moves downhill.
This mass of snow can contain ice, soil, rocks, and uprooted trees.
The three things that help determine the likelihood of an avalanche are the height of the mountain, the steepness of its slope, and the type of snow on the surface.
As the growing mass of snow moves down the mountainside it quickly picks up speed and has been known to reach speeds of 245 miles an hour (394 kilometers per hour).
As the avalanche slides downhill it leaves a path of destruction down the side of the mountain.