What erosional force acts alone to produce an avalanche?

The primary erosional force that acts alone to produce an avalanche is gravity. When the gravitational pull on a mass of snow, ice, or rock exceeds the frictional forces holding it in place, it can lead to a sudden and rapid downhill movement. This process is often triggered by factors such as heavy snowfall, melting temperatures, or disturbances like an earthquake or human activity. Once initiated, gravity drives the material down the slope, resulting in an avalanche.