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Transverse crevasses (glacial crevasses)
Glacial ice, similar to a very viscous fluid, flows slowly downhill. Depending on the composition of the glacier bed and the steepness of the slope, the ice flows faster or slower. In the transitions from slower to higher flow velocities, such forces are generated in the ice that the ice breaks and crevasses (= transverse crevasses) are formed at right angles to the direction of flow.
Narrow transverse crevasses in Tälligletscher (Binntal).
The ice flows from left to right. On the right the terrain becomes a bit steeper. The ice flows faster in this area than in the flatter area on the left. Photo from 25.7.2015.
In the photo above, it is easy to see when crevasses are dangerous for alpinists. The crevasses in the foreground are well visible and only partly filled with snow. For alpinists these crevasses are no problem.
At the upper right of the photo the crevasses disappear in a snow-covered part of the glacier. In this case the alpinists cannot see anymore where under the snow a crevasse is. If the snow bridge (= snow layer covering the crevasse) is too thin/weak, it cannot bear the weight of an alpinist and collapses. The mountaineer then falls into the crevasse. For this reason, a snow-covered glacier may only be climbed by roped parties. In this way, the alpinists can secure each other and in an emergency limit a crevasse fall and rescue the fallen one from the crevasse.
Transverse crevasses in the Allalin glacier (Saas Valley).
The ice flows from left to right. Photo from 7.8.2015.
Transverse crevasses in alpine glaciers can have a width of 10cm to four or more metres. The depth can range from a few metres to 50 metres and more.
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Published:
04.04.2020
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