Powder snow avalanche

Such flows dissipate when the turbulence can no longer hold the particles in suspension and they are deposited on the lower boundary.

When the turbulence is strong enough to suspend new material from the bed or the underlying dense flow then current is said to be auto-suspending.

[4] In powder snow avalanches, even at these low concentrations, the extra density of the suspended particles is large relative to that of air, so the Boussinesq approximation, where density differences are considered negligible in inertia terms, is invalid, so that the snow grains carry most of the flows momentum.

This is in contrast to turbidity currents and laboratory experiments in water where the extra inertia of the particles can usually be neglected.

Nonetheless, due to the extreme difficulty in estimating particle concentrations in natural flows there remains considerable uncertainty—and debate—concerning the particle loading in large submarine turbidity currents and the validity of the Boussinesq approximation.