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Comment by skummetmaelk | Hacker News Reader

I thought the common advice was to try to swim upwards while you were moving.

That's probably said just to keep you from panicking to give you something to attempt/think about while snow is crushing you. How can a mass of (often wet or frozen in blocks) snow tearing down trees and hurling rocks allow you to swim? Wishful thinking, survival is a question of luck. Maybe in very small avalanches. Many people get their skulls crushed, the forces there are immense... Best way is to avoid avalanche terrain completely. If you walk on a snowfield hearing strange noises a few feet under your legs, run for you life! Abort immediately even if it is your last chance for a climb/ride and would cost you a lot of money.

Avalanches act very much like liquids while they are still moving, swimming upstream is indeed the common advice and it has definitely worked. That is why one of the newest devices to survive one (if you are caught) is basically a life preserver: https://www.scott-sports.com/global/en/page/avalanche-pack

These serve the dual purpose of protecting your head and decreasing your density so you float to the top of the snow pack.

Yes, obviously there are big enough avalanches with huge slabs that will kill you in the ride, especially if you end up going through trees, but most skier involved avalanches are on more open terrain (thus why they slide) and are loose snow while moving.

Avalanche bags work nicely in small slab to medium powder avalanches where you might end up upside down a few feet under the surface and suffocate without these bags. It won't help you with most killer avalanches such as large powder ones (220mph and acting as concrete when they stop, filling your cavities), heavy wet ones in spring taking grass, rocks and tree trunks, and most importantly large frozen slab avalanches that just don't care about any equipment you might have or movements you do (and those often give you acoustic signals before they are ready to go). I've read somewhere that without any special equipment, your avalanche survival rate is that of lightning strike. I guess we see videos only of those survivable ones so we often underestimate the danger.

There are a great many things which are inevitably fatal in the worst case, but for which there are effective measures that can improve your chances of survival otherwise.

There are unsurvivable avalanches (i.e. in the best case you end up dead in one piece):

https://www.youtube.com/watch?v=NDEP15NTMgc

Some avalanches can destroy bridges or change landscape. It's truly just the survivor bias we see on videos making us think the worst cases aren't very common.

> It won't help you with most killer avalanches such as large powder ones

This is tautological. Yes, few people survive killer avalanches, because that's what defines a killer avalanche.

Many avalanches encountered by backcountry skiers especially are not these giant killer ones, and can be survived either by skiing out of them or having the proper equipment and training. Your odds aren't great, but they aren't nothing either or people wouldn't bother carrying the gear. (beacon / shovel / probe / avy bag)

Anyways, this is sufficiently off topic, but your characterization of avalanches is movie-like-stuff. Huge avalanches happen but they aren't the typical case. Most are small / medium slides triggered by humans in the backcountry.

Terrains I usually ski at (black & double black diamonds + yellows) tend to have accidental massive avalanches (i.e. randomly stepping on some 5x5ft patch that causes avalanche to fall), so I need to be prepared for any eventuality and estimate safety of the area. I have seen people diving head first on a steep slope, causing avalanches to roll, and they telling me they couldn't move while in the flow and their lungs being super compressed, making them unable to breathe. Especially in spring you need to be super careful as even a smaller wet avalanche can easily kill you - those are usually slow and stop all the way down in the valley, sometimes taking houses with them, crushing you with weight and without any chance to escape.

When I did avalanche safety training, we were told your chance of surviving an avalanche with (shovel/probe/beacon) is about 50% overall. Roughly 25% of people are killed in the avalanche (before it stops). If you survive the initial avalanche, if you're buried your buddies have about 10 minutes to dig you out. After that, survival rates drop rapidly.

Assuming you have people around that can locate you/dig you out (beacon/shovel/etc. you mentioned), and you manage to have some breathing space (that could allow you to survive for a few hours in the best case). If not, then probably those stats with lightning strike might be comparable, i.e. you rarely survive. There are plenty of "lone wolf" tourists/off-slope skiers. I used to ignore these when I was a reckless teen, now I try to be super careful.

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