The Brazil Nut Effect — How To Survive an Avalanche

The amount of knowledge we have about snow avalanches has increased immensely over the past several decades. Using this information, experts are constantly reformulating survival techniques and devising improved safety gear. The Avalung came out of knowledge that avalanche victims are frequently poisoned to death by their own exhalations. Beacon improvements come from knowing how important things like reliability and ease-of-use are to a quick search. Knowing how violent being ‘lanched is, experts now recommend keeping your backpack tightly strapped when in avalanche terrain so it’ll protect your spine if you take a ride.

More, experts are re-thinking what you need to do while you’re caught in a snow slide. The recommended plan used to be fight and swim — do anything to stay on top or escape to the side. This appears to be changing. Dale Atkins, who investigated avalanche accidents for years while working with the Colorado Avalanche Information Center, is promulgating a new way of looking at survival. In an excellent presentation, he recommends one thing when you’re caught: Don’t bother with attempts to swim or fight. Instead, get your hands in front of your face, keep them there, and if you’re buried do anything to make an air pocket when the slide stops. (Or if you have an Avalung, concentrate on getting it in your mouth and keeping it there.)

Beyond the importance of a breathing space, the key concept Atkins covers is that while a snow avalanche behaves somewhat like a river or waterfall, it is actually a “granular flow,” meaning a snow avalanche is a bunch of solid particles falling down a mountain. Such behavior is similar to dumping sand out of a wheelbarrow down a hillside. In a granular flow, larger or less dense objects tend to rise to the surface. For example, snowmobiles are twice as likely to stay on the surface of an avalanche than a human. And humans tend to rise to the top as well, hence the large percentage of people avalanched who end up unburied. He calls this the “Brazil nut effect,” as when you shake a can of mixed nuts and all the larger nuts rise to the top. As for swimming versus concentrating on an air pocket, the point of this concept is that swimming and struggling have less to do with ending up unburied than simple physics. Thus, working to create an air pocket may be more important than things (like swimming) that keep your hands away from your face.

As for gear, the reality of the Brazil nut effect means that avalanche airbags are quite possibly as effective as their makers claim they are, and truly worth developing as a viable avalanche safety device. I’m certain we’ll see this happen — it’ll be interesting.

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