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American Association for the Advancement of Science

The makings of an avalanche

An example of slab avalanche showing the area of release. The snow in this area starts moving as one piece.

One of the most serious dangers you could face in the mountains is an avalanche of snow coming towards you. These destructive forces of nature present a serious risk to both life and property, often demolishing everything in their path. Unfortunately, there is no sure way to predict an avalanche before it happens, but recent research by Joachim Heierli and colleagues in the United Kingdom and Germany shed light onto exactly how avalanches form and their findings are somewhat surprising.

Previously, most researchers believed that avalanches generally occurred when a layer of snow became loose from a pile and slid off of other layers. They thought the pull of gravity on the layers of snow to be one of the most important factors in an avalanche. But Heierli’s studies took a closer look at the physical properties of the snow itself to find that under the surface, the layers of snow on the ground crack and shift inside.

The researchers now say that something called anticracks, which cause the snow to loosen and come apart, play a much larger role in the formation of avalanches than previously thought. When these anticracks occur in the layers of snow, the snow is no longer held together by itself and becomes very easy to move. This phenomenon, combined with the downward pull of gravity, determines if an avalanche will occur and how severe it will be.

These findings are startling because they suggest that even small layers of snow may come apart more easily that researchers once thought, and that even skiers moving over flat ground or on very small slopes cannot consider themselves entirely safe. However, these new findings could also be used to help in predicting where an avalanche might happen. In the future, this information might even save someone’s life.

The related article was published in the 11 July issue of the journal Science.