Video: Self-Lubrication Speeds Avalanches

Credit: Barbara Turnbull/University of Nottingham

In September 2002, roughly 100 million cubic meters of rock and ice crashed down onto the Kolka and Maili glaciers in Russia’s Kazbek Massif, sending both glaciers sliding toward the Genaldon River valley. The avalanche reached blistering speeds of more than 150 miles per hour. How did the ice and rock flow so quickly? In a new study, reported in an upcoming issue of Physical Review Letters, a researcher tested the idea that surface melting in colliding ice particles might be playing a role. She created an avalanche in the laboratory by half-filling a hollow wheel of clear plastic with frozen water droplets and rotating it so that the surface of the ice balls became a slope. As ice bounced and slipped down that slope (shown in video), the amount of water in the mixture increased. Even at -4°C, enough liquid water formed at the surface of the ice particles to enhance the speed of the flow by more than 10%. The water lubricates the ice, and the higher speeds mean more collisions and melting—so the speed of an avalanche is, in part, due to this snowball effect.

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