Staying Alive in Avalanche Terrain
Format: PDF / Kindle (mobi) / ePub
This new edition of Bruce Tremper's seminal book, regarded as the most authoritative commentary on avalanche matters, is organised according to the structure of the American Avalanche Association classes and all chapters have been updated with the most recent data and techniques, and reviewed by peer experts.
it usually the most important weather factor to consider. Snow behaves viscously when it moves slowly as demonstrated by this roof glide. When strained to its breaking point, it behaves elastically and fractures. (Switzerland) © Juerg Schweizer Finally, let’s deform the snow at an extremely rapid rate. A 90 kilogram (200 pound) rider gets a 200 kilogram (500 pound) snowmobile stuck on a steep slope, and now you can begin to understand why people make such great avalanche triggers. The stress
wet rain crust diffuses upward through the new, low-density snow and it quickly grows faceted snow, especially near the warm crust (Figure 5-12). Even though the snow bonded well initially, after 2 to 4 days under a strong temperature gradient, you suddenly start triggering avalanches on fine-grained faceted snow. Whoa! In this case, we haven’t added any weight to buried weak layers, but instead, we’ve decreased the strength of the buried weak layer—with the same result. Like I say, tricky! Look
Extended Column Test (1 to 2 minutes) This is a wonderful, ingeniously-simple new test invented by Ron Simenhois, an Israeli physicist who currently spends his winters ski patrolling in the U.S. and his summers patrolling in New Zealand. He and Karl Birkeland of the Forest Service National Avalanche Center recently published their work on this test. It was inspired by Ian McCammon and others who illuminated the importance of both initiation and propagation in avalanche fractures. As I discussed
will sometimes hear them referred to as “yellow flags” as well. For instance, someone might say that the weak layer had four lemons, meaning that it had four out of the five critical characteristics. Below are the weak layer characteristics common in human-triggered avalanches: 1) Persistent grain type (depth hoar, faceted snow or surface hoar) 2) Grain size difference between weak layer and surrounding layers greater than 1 mm 3) Hardness difference between weak layer and surrounding layers
back. When all else fails, go underground. Many people have saved themselves during storms by digging a snow cave or creating a snow shelter, which can be surprisingly warm and cozy. Yes, you might be uncomfortable and your loved ones may worry, but at least you will be alive. 6th Commandment: Thou Shalt Start Small and Work Your Way Up Terrain almost always gives you small gifts—small test slopes—that you can jump on to see how they respond. Never pass up a test slope. It’s better to find