Snow under pressure: Study provides new insights into avalanches
Keystone-SDA
More pressure does not make a snowpack more stable, but in fact more susceptible to avalanches. This is according to experiments by researchers at the WSL Institute for Snow and Avalanche Research (SLF).
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The new data could help to further improve avalanche forecasting in the long term, as the SLF announced on Wednesday.
Weak layers in the snowpack are often the cause of slab avalanches. However, according to the SLF, the forces that cause these weak layers to break and thus lead to avalanches are still disputed in avalanche research.
Since the 1970s, two opinions have clashed on this issue: according to one theory, additional pressure from above, for example from a thicker or heavier snowpack, makes the weak layer more stable. According to this theory, more pressure from above requires stronger so-called shear forces, which pull the snow down the slope to cause a fracture.
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According to the other theory, it is precisely this additional pressure from above that brings the fragile layer closer to collapse, so that even a lower shear load is sufficient to trigger a fracture. The new experiments now support this theory.
Snow samples from Davos
For the study, the researchers analysed 63 samples of natural weak layers in the cold laboratory. The snow samples came from the Davos, Graubünden region and were subjected to combined compressive and shear forces using a specially developed test apparatus.
The samples consisted of snow-covered surface frost. In the laboratory, the researchers simulated the forces acting on the snow cover on a slope: the vertical normal force and the parallel shear force. A high-speed camera recorded the exact moment at which the layers broke.
The results were published in the scientific journal Geophysical Research Letters.
Translated from German by AI/jdp
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