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What Triggers an Avalanche?

avalanche, avalanches, snow, what, why, how, trigger, triggers, noise, loud noise, loud noises
The typical avalanche, traveling at 80 mph, is anything but fluffy and rarely triggered by noise. (Image credit: Mariordo Mario Roberto Duran Ortiz, Wikimedia Commons)

The most common and deadly type of avalanche is called a "slab avalanche," in which a cohesive plate of snow shatters like a pane of glass and slides as a unit off the mountainside, according to the Utah Avalanche Center.

The event is typically triggered not by loud noise, as is sometimes believed, but when snow accumulates very rapidly. The sudden addition of weight can fracture a weak area below. The condition is sometimes a lot like snow sliding in slabs off the windshield of a car as the temperature warms up.

A person's weight can trigger an avalanche, too. In fact, some 90 percent of avalanche accidents involving people were triggered by the victim or someone in the victim’s party, according to the Avalanche Center.

A typical avalanche travels at about 80 mph in one dense slab. Rarely are they loose and fluffy.

Since 1950, about 235 people in the U.S. have been killed in slab avalanches, according to the National Snow and Ice Data Center.

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Robert Roy Britt
Rob was a writer and editor at starting in 1999. He served as managing editor of Live Science at its launch in 2004. He is now Chief Content Officer overseeing media properties for the sites’ parent company, Purch. Prior to joining the company, Rob was an editor at The Star-Ledger in New Jersey, and in 1998 he was founder and editor of the science news website ExploreZone. He has a journalism degree from Humboldt State University in California.