Avalanche is a rapid flow of snow down a slope, typically triggered by a large mass of falling snow. Avalanches can occur naturally, or be caused by human activity. Natural avalanches are typically triggered by a large mass of falling snow, or by the sudden release of snow from a high, steep slope. They can also be triggered by earthquakes, volcanoes, or other large-scale events. Human-caused avalanches are typically triggered by skiiers, snowmobilers, or other people who disturb the snowpack.