The Science of Avalanches

[BaalChatzaf]

The science of avalanches. Avalanches are a first cousin to turbulence and chaotic dynamics. One might think avalanches should be pretty straightforward to characterize mathematically and to predict. Not so. Avalanches involve non-linear mechanical dynamics and are akin to turbulence and chaos (in the physical sense). We have a wonderful set of equations that describe turbulence in fluids but there is only one problem: we cannot solve this equations either analytically or by numerical methods in the general case. Only simple solutions to the Navier Stokes equations are known and the Millennium Prize of one million dollars for an extension of the solution methods is still outstanding. Avalanches of snow and sand are even more difficult to characterize because the interplay between gravity and the frictional forces binding the grains together are even more complicated than the case of continuous fluids.

So avalanches are not predictable. In the U.S about 27 people a year die in snow avalanches and even more in rock and mudslides. Colorado leads the nation in avalanche deaths --- 67 since 2005. What is done now is to clear the slopes of skiers and hikers and fire artillery shells at the snow triggering small avalanches. This drains of the gravitational potential energy and makes a big bad avalanche unlikely.

Please see this article in Science: http://tinyurl.com/zkmko3q (tiny URL)

Ba'al Chatzaf

[Brant Gaede]

Avalanches are not specifically predictable. Nor are earthquakes. Some of those suckers are one layer of packed snow sliding off an underlying layer. Say you have a base layer. A skein of ice forms on top. Then another snowstorm puts in another layer. Now you have a gross instability if there's a slope. This doesn't mean, however, that an uncovered base layer won't let go and kill those below. There are so many variable factors affecting the possible dynamics including skiers triggering an avalanche. Mere sound can too.

--Brant

great article--thanks; I read it after I wrote the above (I didn't know I was so ignorant)

[Peter]

We need ski volunteers to test these theories. You know. The guys who sky dive, snow board over too steep slopes, bungie jumpers, etc. Why not risk your life for science and people who must venture close to snowy slopes? And more volunteers are needed to test medical procedures and vaccines. : - )