One of the cruelest avalanche tricks out there is the old “I was just minding my own business skinning up a nice valley when suddenly both sides collapsed thousands of feet above me and I was buried 20′ deep.” It is a mean spirited trick as the skier may be on flat ground far away from the starting zone, and to add insult to injury, it is often fatal. This particular type of avalanche is different from the “wrong place, wrong time” slide where a skier happens to be below a slope when it decides to cut loose, because in this case, the skier is actually triggering the slide remotely from hundreds/thousands of feet away.
From studying Architecture, this phenomena reminds of an architectural arch, where all of the compression forces are balanced and held in place by a keystone at the top. Exhibit A below:
A collapsing valley is basically the same thing, except the arch it turned upside down, and instead of carved stones, you have a cohesive slab of snow. When an unsuspecting skier walks along the base of the valley, he is essentially knocking out the keystone that holds the valley walls up, as illustrated below:
This type of avalanche is very difficult to accurately predict, but not that hard to avoid. If the snowpack has pronounced collapsing (like the Wasatch has had this season), it means that keystone is being punched out and it would be better to stick to the high ground. The chances of getting caught in a slide like this are about a million to one (unless you live in Colorado, where it is more like 50/50) and the best defense is to be forewarned.
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One of the basics of avalanche avoidance and good backcountry travel protocol is to always stop below your partner(s), not above them. The reason for this is two-fold; one is that you might blow your last turn and take out your partners from above, and the other is that the weight of a stopping person may cause the slope to fracture, especially if it is already weighted by another person. If this happens, it often breaks right at the top person’s skis and then takes the lower person for a ride. I had this happen once and it was almost a slow-motion comedy. I had stopped, then my partner skied up behind me, came to a stop, the slope fractured at this edges and I started to get swept away, but not before I said “Thanks.” to which he said “Sorry.” It had a happy ending as I was able to grab onto a tree, but ever since then, I go out of my way to stop in places where my partners will have a hard time stopping above me.
It is a subtle difference (and kind of a bad photo to illustrate the point), but stopping position “A” is much better for the first person than stopping point “B” although both are about the same as far as being protected from an avalanche coming down from above. Position “A” is tucked right up underneath a rock, which doesn’t leave the second skier any other chance BUT to stop below you.
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Whenever possible, I prefer to ski a couloir or avalanche exposed shot in leapfrogging segments. The idea is that one person skis, then tucks out in a safe spot and watches the other person, then they do the same. Ideally, the stopping points will be staggered so that you can see your partner at all times as they are coming towards you and going by.
Polly booting up a couloir in the Atlas Mountains, Morocco. The numbers illustrate the sequence of descent and are probably exaggerated for this particular couloir - it could be done with about half the stops.
This process keeps the ski descent moving along quickly (time is of the essence in avalanche terrain) and allows both people to have clean lines. Another benefit is that you are never very far removed from your partner should they get caught in a slide. Skiing an entire shot all at once is great for minimizing your exposure, but if the following partner gets caught in a slide that buries him/her halfway up the chute, being down at the bottom means a long, slow hike to get back up.
One of the keys to doing this style of skiing is to have the first person only ski a short half-shot to begin with, which then sets the team up for the rest of the descent. It may not be the most social way to ski, but it is safer and efficient. When you are done, you can always talk at the bottom.
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The snowpack is the third major factor and also the trickiest one. Like the weather, its history is more important than its immediate surface conditions. The plot thickens with the snowpack as there are almost always weaknesses in it, but they are difficult to quantify. Snow is the building block of avalanches, but it is these tiny weaknesses between the blocks that actually cause them. Assessing the snowpack is difficult because these paper-thin layers are hard to identify and quantify amidst many feet of snow.
- An avalanche triggered by a very surprised mountain lion in the Wasatch Mountains. No cats were hurt during the making of this photo and the tracks led away from the debris.
Thinking of avalanches in terms of terrain, weather and snowpack simplifies the decision process as you need all or a combination of these elements to have a slide. If the weather and snowpack are unstable, but you are on flat terrain, you won’t have an avalanche. Or, if you are in avalanche terrain, but the weather and snowpack are stable, you probably won’t have an avalanche.
Thinking in terms of this triad also makes it easier to extrapolate decisions when you are unsure of one of the factors. If you are in a) avalanche terrain and know it has been b) storming for the last two days, it’s a safe bet that you will trigger some slides, even if you know nothing about c) the stability of the snowpack.
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You know what an avalanche is, huh? It’s what’ll kill ya.
Gabe – Alta Ski Patrol
The avalanche path and the skier can never truly be friends. In the backcountry, the skier wants what the avalanche path has (steep & deep) but the avalanche could care less about the skier and always has the upper hand. It’s an uneasy relationship at best and it is important not to get too cozy with slide paths as they have a temperament of their own and should never be trusted.
- An early morning avalanche. At the time, avoiding getting swept down in the debris seemed like it was based on skill. 18 years later, I think it had as much to do with luck as anything! Photo by Doug Hall.
As a base concept, avalanches are best avoided to begin with as it’s rare to win a fight with even a small one. If you find yourself thinking that a slope will probably slide, but that it won’t go very big, or you’ll be able to outrun it, that is a classic Red Light. Once you are caught, all bets are off and anything can happen, including terrain traps, shallow burials and stepping down. Avalanches are difficult to accurately forecast in advance, yet painfully obvious in retrospect. For this reason, I prefer to focus on avalanche avoidance instead of prediction. Assume slopes are guilty until proven innocent and always watch your backside.
continued tomorrow…
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