An avalanche (also called a snowslide) is a rapid flow of snow down a slope, such as a hill or mountain. Avalanches can be set off spontaneously, by such factors as increased precipitation or snowpack weakening, or by external means such as humans, animals, and earthquakes. Primarily composed of flowing snow and air, large avalanches have the capability to capture and move ice, rocks, and trees. Though they share similarities at first, avalanches are distinct from slushflows, mudslides, rock slides, and serac collapses. They are also different from large scale movements of ice.