What Causes An Avalanche (And What Doesn't) Might Surprise You

Avalanches claim about 28 lives a year, on average. That's not a huge toll, of course, but it sbould be enough to give you pause next time you're surrounded by snow-covered mountains.

But what exactly triggers avalanches in the first place? Forget what you've seen in the movies. Yelling isn't likely to cause an avalanche. Nor is a sonic boom. But walking in the wrong spot just might.

"Avalanches usually occur when a weak layer of snow deep beneath the main slab fractures, and this usually happens because of the rapid increase in weight," Maddie Moate, host of the BBC's YouTube video series Earth Unplugged, says in a new episode (above).

But what's the biggest cause of snowslides? You might not have guessed it: wind. A powerful gust can pick up snow and dump it down 10 times faster than a snowstorm.

Be careful out there!