Loose-snow avalanches occur when weak surface snow is on a slope that is steeper than its critical angle of repose. Typically the cohesionless snow is either dry unsintered fresh snow or wet snow formed from melting. These are called dry loose-snow and wet loose-snow avalanches respectively.
When the snow is disturbed , the loose snow undergoes a localized rotational slip and then moves downslope in an inverted V-shape pattern. The initial slip involves very small masses of snow that range in size from one grain of snow to a the size of a large snowball. Typically they contain less than 1 cubic meter of snow. As the avalanche moves downslope, it can set other cohesiveless snow in motion. The avalanche finally comes to rest once the snow reaches its kinetic angle of repose.
Since the speed of a loose-snow avalanche is relatively slow and the initial mass of snow is small, they typically do not cause much destruction. Nonetheless hazards are still involved. Even though the avalanches are small, they are large enough to carry a person downslope breaking bones and on a rare occasion causing death. Large loose-snow avalanches also pose a threat to cars and other facilities. Loose-snow avalanches could potentially trigger devastating slab avalanches. This can happen in two ways. Snow from loose-snow avalanches may build up into large deposits which may be releases as a slab or the loose-snow avalanche may provided enough external loading to cause shear stress collapse which triggers slab avalanches.