One of the biggest dangers of winter ski tours away from secured ski runs is definitely snowboards, which can develop into avalanches and sweep people away. According to computer simulations, these avalanches can occur in a similar way to some earthquakes. This is written by Johann Guillaume of the EPFL Lausanne and his working group on “Physics of Nature”.
For their study, the team ran hundreds of simulations over days to model how large blocks of snow would break free and then race through the valley. The focus was on avalanches, which often lead to fatal accidents. A layer of snow on the slope dissolves and quickly begins to slide down, taking other layers of snow with it. Snow plates often break when a load is applied to them from above; The crack can spread along the edge at a speed of up to 300 kilometers per hour.
A thin layer of poorly cohesive and porous snow usually collapses under a heavier, more solid layer, and then slides over this soil. It starts slowly at first, but after a few metres, gravity creates tension in the compact layer of ice, eventually breaking it into smaller pieces: the avalanche picks up speed. Gaume and co compared this simulation to a video of an avalanche shot by skier Mat Schaer, a former student of Gaume. Then the analysis of the simulated movie confirmed.
A similar process also occurs in earthquakes that occur when plates move laterally. Here a daughter fault can form in front of the main fracture front and spread at high velocity while paving the way for the large rock fracturing. Gaume and his team hope their study will help improve avalanche prediction. This can be used to identify areas in the Alps, for example, where these avalanches primarily occur.
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