Abstract 


Powder snow avalanches are gravity currents driven by the increased
density of suspended particles. They usually start as a dense granular
flow down a slope. As the material accelerates down the slope,
turbulent eddies in the ambient fluid entrain particles from the upper
surface and front. If sufficient material becomes suspended the excess
density then provides enough energy to maintain the turbulence and the
suspension can flow down the slope as a gravity current. Experiments
with snow and polystyrene balls on steep chutes are reported, where
this transition occured. Measurements were taken with video cameras
and air pressure sensors and these results will be shown and
explained.


-- 
Dr. Jim McElwaine