An avalanche is the rapid flow of snow down a sloped surface. There are two general types of avalanches: slab avalanches and loose snow avalanches. Both begin when there is a mechanical failure in the layers of snow caused by when forces acting on the snow are greater than its strength. For slab avalanches, this leads to a cohesive layer of snow sliding down a slope. For loose snow avalanches, unconsolidated snow falls and gathers as it moves down the slope. Colorado, as a mountainous state, has an active avalanche environment.