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I am reading this highly-rated book about avalanches and I was impressed by this sentence, in its beginning.

Over 25 percent of avalanche victims in the U.S. die from trauma from hitting trees and rocks on the way down (about 6 percent of avalanche victims in Europe and as many as 50 percent in Canada)

How can there be such a massive difference? 6 percent of people dying from trauma from hitting trees and rocks in Europe and 50 percent in Canada... with the US being about in the middle of that statistic.

The very first - quite rough - idea that comes to my mind is, there may be much more trees and rocks in the average Canadian ski route compared to European ones.

But, it sounds quite superficial. Still, those numbers differs too much; there must be some reason behind this spread. Does anyone knows what this reason is (or are)?

  • Europeans have thicker skulls? – Olin Lathrop Dec 21 '14 at 23:19
  • Or maybe bigger brains? ;) Nah I think it has to be the terrain the Canadians or Europeans are moving in. Cant think of another reason here. – Wills Dec 22 '14 at 7:05
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    Or also the fact that in canada helicopter-skiing is much more popular/practiced and it's easier to get up a "high risk" peak and ski down. And in Europe you need to first get up this peak, what filters the "unskilled" folks from the "skilled" ones. – ibex Dec 22 '14 at 7:22
  • Please note that we are not talking about how many people is involved in an avalanche. But, among the involved ones, how many die from trauma compared to the ones who die of asphyxia or survive. – Dakatine Dec 22 '14 at 7:31
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    my guess is that skilled folks don't get caught that often in avalanches so also that they don't get swept over rocks/trees. Less alpine-skilled folks get caught more often and then the risk to get swept over rocks is greater. also that a lot of helicopter-skiers go down high risk couloirs with not too much knowledge about avalanches and terrain. There are in Canada and Europe steep mountains, with the same conditions. I think it depends more on the single person rather than the mountains. – ibex Dec 22 '14 at 8:02
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I don't have my copy of How to Survive in Avalanche Terrain in front of me, but one of the things that stood out to me relating to this is the wide variety of avalanche climates that exists not just from country to country but from mountain to mountain.

You've got intermountain, continental, and maritime avalanche climates all with their own habits and characteristics. There are so many variables at play here that Bruce was able to write an entire book about it. Avalanches tend to occur at a specific slope angle in each climate, and that angle can be very different from each other climate, but trees and rocks probably tend to exist in the same type of terrain.

Taking all of that into consideration, what seems to be going on here is that the avalanche terrain in Canada that lures back-country snow-goers must contain slopes that allow for more rocks and trees. There are several types of avalanches in that book that aren't necessarily powerful enough to easily bury you, but still powerful enough to sweep you into a tree. Combine those types of avalanches with slopes rich in trees, and you've got the recipe for the blunt force trauma.

Europe, on the other hand, could very well have mostly terrain that either doesn't promote as many trees and rocks, or does promote larger avalanches that are more likely to bury the victims.

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    Slab avo's pack enough punch to induce fatal injuries without trees/rocks.... – user5330 Dec 24 '14 at 4:21
  • youtube.com/watch?v=UNTjxnlKhUQ - a good example. – user5330 Dec 24 '14 at 4:47
  • Is there also a potential consideration that USA and Canada attract a particular demographic which are much more likely to seek backcountry and avanlanche-prone territory? The majority of the world's extreme ski and snowboarding documentaries are filmed in Canada and the USA. It might be as simple as the avalanche statistics are higher, not because of the terrain but because more snow-sports enthusiasts are seeking that terrain and becoming caught in avalanches. – Venture2099 Jan 2 '15 at 9:35
  • There could certainly be something to that, the risk culture in North America could have an effect. But this question and my answer pertain to the manner in which the victims die, not simply how many die. – Scott Hillson Jan 3 '15 at 5:03
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While it does not account for the difference between Canada and the USA, I'm pretty sure that one reason for the low numbers in Europe is that the latter has a lot of seasonal mountain pastures in active use, so livestock grazing keeps many slopes completely free of trees:

In fact, the word "Alps" for Europe's main mountain range is related to the words for such pastures in German (alm/alpe) and French (alpage).

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I wouldn't read too much into any avalanche statistic. While there may be plausible reasons behind the difference, the data sizes are just too small to make any reliable comparisons.

Avalanches are exceptional events and avalanches that involve injuries that get reported are even more exceptional events. When you look at statistics based on infrequent events the "law of small numbers" applies. This means that you will see wide variation in any statistic simply because the sample size is so small. This in no way means that avalanches are not a serious risk in Canada, but since Canada only accounts for 10% or less of reported fatalities world wide, in a statistical sense you expect to see wide variations in a small sample.

Our brains are built to make coherent stories based on minimal data, and when we see such a striking difference, we want to build a story around it to explain it.

For example: Imagine that I flipped a coin 4 times in Canada and they all came up heads, I then flew to Europe and flipped a coin 4 times and they call came up tails. It would be very tempting to then create some theory around why coins behave differently in different continents, but in reality it's just random chance at work.

Learning to recognize and compensate for the inherent heuristic traps in your thinking is likely the most important skill for long term survival in avalanche terrain. Given the highly random nature of avalanches it's very easy to fall into the trap of confusing luck with skill.

  • I am not that sure that this is such a small sample to be relevant, but that's an interesting perspective to get deeper into. – Dakatine Dec 25 '14 at 20:48
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    Western Canada sees many Avalanches with many injury reports and over ten deaths a year. I would go as far as saying they are a common occurrence and not "rare"...Here is a good resource: old.avalanche.ca/cac/library/incident-report-database/view – AM_Hawk Dec 25 '14 at 23:34
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    More information : metronews.ca/news/edmonton/974676/… – AM_Hawk Dec 25 '14 at 23:42
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    Perhaps rare is the wrong word, but Canada accounts for less than 10% of avalanche deaths in countries that report incidents. It's exactly that kind of small sample in which you'd see wildly varying measurements of any quantity. – Fred the Magic Wonder Dog Dec 28 '14 at 19:39

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