Staying Alive in Avalanche Terrain
My mountain rescue friends say this is the bible of avalanche survival knowledge. Now in its second updated edition, it is a readable, immensely informative dissection of how avalanches happen, and how to avoid them — and what should be done when they aren’t avoided. Neither overly technical, nor dumbed down, the book is near perfect in pitch, telling you important stuff in vivid and interesting ways. It’s generally recognized as the best source on the subject of moving snow. I read almost the entire book even though I am not often in avalanche terrain, just because the information is so clear, insightful, and brilliant in the details. More outdoors fans are winding up in avalanche territory; These insights could save your life.06/12/12
A generalized graph of European avalanche victims who were completely buried and in total contact with the snow (no people in vehicles or houses). After 15 minutes the percent recovered alive drops precipitously. Half of victims are dead within 25 minutes. The graph does not include victims killed by trauma, which account for about a quarter of avalanche deaths in the U.S. and about half of avalanche deaths in Canada.
People are getting slaughtered by avalanches. I don't think slaughter is too strong a word considering that between 1990 and 2007, 423 people have dies in avalanches in the United States, averaging 25 per year and 15 per season in Canada, and the trend is on a steep upward slope that shows no signs of abating.
Almost all avalanche fatalities involve recreationists, most notably snowmobilers, back-country skiers, snowboarders, and climbers, in that order. Almost all are very skilled in their sport, male, fit, educated, intelligent, middle class, and between the ages of 18 and 40. Does this sound anything like you?
There is hope. In 93 percent of avalanche accidents, the avalanche is triggered by the victim or someone in the victim's party. Which is good, because as the Pogo cartoon says, "We have met the enemy and he is us."
The good news is that we have two important things going for us: first, we have a choice, and second, we already know the enemy. The bad news is that the enemy is us, and that is the hardest enemy of all to conquer.
Snow Is Like Silly Putty
Go to nearly any lecture on avalanches and chances are good that you will see the instructor pull out their trusty Silly Putty. (I've also seen people use a mixture of cornstarch and water.) This is the only way I know how to demonstrate the visco-elastic nature of snow. Silly Putty, like snow, exhibits both a viscous and elastic nature. If you roll it in a ball, you can bounce it (elastic energy). But snow (and Silly Putty) also flow viscously; like the proverbial molasses in January.
The most interesting part of the snow-Silly Putty metaphor is that when deformed slowly, it flows like taffy, but when deformed rapidly, it fractures like glass. The take-home point is: Snow is very sensitive to the rate at which it is deformed. This is probably the most important property to remember about snow, and it's the cause of most avalanche fatalities. In other words, snow, just like people, does not like rapid change.
Snow behaves viscously when it moves slowly as demonstrated by this roof glide. When strained to its breaking point, it behaves elastically and fractures.
Cracking snow is an obvious buzz from the avalanche rattlesnake. Don't take another step! Here, a 40-foot crack shoots out from my wife's skis. She was able to crack the fresh wind slab by safely standing on the flat of a ridge and watch the crack propagate below her. Luckily, the slope below is barely 30 degrees and is a good, small, test slope. (Wasatch Range, Utah)
Unless you practice regularly with your beacon, you probably won't be able to find your partners in time to save their lives.