The Brazil Nut Effect — How To Survive an Avalanche

[mntlion]

hacksaw just set this to me,

http://www.wildsnow.com/?p=520

The amount of knowledge we have about snow avalanches has increased immensely over the past several decades. Using this information, experts are constantly reformulating survival techniques and devising improved safety gear. The Avalung came out of knowledge that avalanche victims are frequently poisoned to death by their own exhalations. Beacon improvements come from knowing how important things like reliability and ease-of-use are to a quick search. Knowing how violent being ‘lanched is, experts now recommend keeping your backpack tightly strapped when in avalanche terrain so it’ll protect your spine if you take a ride.

More, experts are re-thinking what you need to do while you’re caught in a snow slide. The recommended plan used to be fight and swim — do anything to stay on top or escape to the side. This appears to be changing. Dale Atkins, who investigated avalanche accidents for years while working with the Colorado Avalanche Information Center, is promulgating a new way of looking at survival. In an excellent presentation, he recommends one thing when you’re caught: Don’t bother with attempts to swim or fight. Instead, get your hands in front of your face, keep them there, and if you’re buried do anything to make an air pocket when the slide stops. (Or if you have an Avalung, concentrate on getting it in your mouth and keeping it there.)

Beyond the importance of a breathing space, the key concept Atkins covers is that while a snow avalanche behaves somewhat like a river or waterfall, it is actually a “granular flow,” meaning a snow avalanche is a bunch of solid particles falling down a mountain. Such behavior is similar to dumping sand out of a wheelbarrow down a hillside. In a granular flow, larger or less dense objects tend to rise to the surface. For example, snowmobiles are twice as likely to stay on the surface of an avalanche than a human. And humans tend to rise to the top as well, hence the large percentage of people avalanched who end up unburied. He calls this the “Brazil nut effect,” as when you shake a can of mixed nuts and all the larger nuts rise to the top. As for swimming versus concentrating on an air pocket, the point of this concept is that swimming and struggling have less to do with ending up unburied than simple physics. Thus, working to create an air pocket may be more important than things (like swimming) that keep your hands away from your face.

As for gear, the reality of the Brazil nut effect means that avalanche airbags are quite possibly as effective as their makers claim they are, and truly worth developing as a viable avalanche safety device. I’m certain we’ll see this happen — it’ll be interesting.

[IrieRon]

As the natural survival instinct might cause a person to fight and swim, it sounds like keeping your avalung in your mouth and your hands in front of your face could be a "better" response.

It could be like the counter-intuitive move you do while caught in the washing machine while surfing. You can't immediately fight your way to the surface, so you kind of relax and roll with it for a little while.

I posted this slow, clunky link in another forum previously: http://www.abssystem.com/ but you can click on the "How It Works" tab, then 1/3 of the way down you can click the hypertext "See the Statistics."

There is a comprehensive list there, including times the bags didn't inflate, and what happened to the people. It seems fairly unbiased, because they actually list when people were killed while wearing their product.

[summit]

I heard Atkins speak about this... it was a convincing case.

However... if I have my avalung mouthpiece in I'll swim.

[keksie]

a known swiss mountain guide / avalanche expert werner munter also seems to recommend keeping hands near your face over trying to swim in slab avalanches / bigger avalanches. he also states that almost never should you try to ski out of a self-triggered slab avy, because the chances of succesfully doing that are slim and if you try and fail you'll only end up "deeper" in the avalanche. instead he recommends to immediately get rid of skis & poles.

[summit]

he also states that almost never should you try to ski out of a self-triggered slab avy, because the chances of succesfully doing that are slim and if you try and fail you'll only end up "deeper" in the avalanche. instead he recommends to immediately get rid of skis & poles.

shouldn't that depend on the skier's velocity and location on the slab? i would think that if a skier had enough speed in the right direction and was close enough to the slab edge they could stand a chance of escape... but i have no first hand knowledge here.

[keksie]

shouldn't that depend on the skier's velocity and location on the slab? i would think that if a skier had enough speed in the right direction and was close enough to the slab edge they could stand a chance of escape... but i have no first hand knowledge here.

yea.. well he goes through it very briefly, i'll quote from the book.. neither german or english are my native languages so bear with me, i tried to translate it:

"The often recommended is "try to ski away -method" is not only in the most cases pointless, but also an additive risk. Because the blanket of snow moves and breaks into blocks, a fall is very likely. In that case ( = after fall) it is practically impossible to get rid of skis and poles. In most cases it is impossible to cover the whole extent of the slab in just a few fractions of second. Under circumstances you don't ski "out of" it (the avalanche) but "in it". Furthermore the slabs reach a speed of 50km/h already just after the avalanche cuts loose. [...] Letting go of poles and getting rid of skis is the most succesful method in staying on top of self-triggered slab avalanche! My personal and close experiences in slab avalanches have showed me that without skis and poles you have a real chance of not getting buried or getting buried closer to the surface."

so he doesnt speak of "all cases" but "most cases", i'll take that as if you're near the edge of slab and have a chance to ski out then you should go for it. i guess trying to calculate whether to try to ski out or get rid of your skis while already being on a moving slab is, uhh, interesting, and in that point you'll probably end up doing what your instincts tell you.. so i'll quote what lou wrote on wildsnow

And perhaps it’s all kind of ludicrous, as the things are incredibly likely to take your life no matter what. Sort of like talking about what to do if you see you’re heading into a headon crash with a loaded cement truck.

edit: heres what he writes about swimming/not swimming:

"The often recommended swimming motions are only possible in small snowslides - in a grown slab avalanche with very heavy blocks no man can do such arm movements. The "swimming" also disables the last important reaction of the buried: Putting arms in front of his/her face to form an air pocket. After getting rid of skis and poles raise your arms in front of your face and hold them at this position with all your strength: This enables you to form the air pocket, which is needed for survival"

[IrieRon]

.. neither german or english are my native languages so bear with me, i tried to translate it:

Dude, your third-language translation is better than a lot of my friends' native-language English.

[couloirman]

get rid of skis? try doing that while skiing down a slope that just tore away. I just hope your din setting is low enough itll do it for you, but i mean com one, what are you really going to do? reach down with your hands while moving and push with your fist? sounds like a recipe for cartwheeling and not being able to control anything that happens right after to me.

[keksie]

get rid of skis? try doing that while skiing down a slope that just tore away. I just hope your din setting is low enough itll do it for you, but i mean com one, what are you really going to do? reach down with your hands while moving and push with your fist? sounds like a recipe for cartwheeling and not being able to control anything that happens right after to me.

well personally i would just step on the heelpiece with the tail of my ski and then step with boot on the other heelpiece.. thats what i normally do too, and its quite a lot faster than using poles/hands.

[summit]

well personally i would just step on the heelpiece with the tail of my ski and then step with boot on the other heelpiece.. thats what i normally do too, and its quite a lot faster than using poles/hands.

ever tried doing that while skiing at speed on a collapsing snowpack??

i've never tried kicking off my skis or removing them while i'm moving (at least not on purpose )

[keksie]

ever tried doing that while skiing at speed on a collapsing snowpack??

oh well, i guess every plan has it flaws

[AltaPowderDaze]

get rid of skis? try doing that while skiing down a slope that just tore away. I just hope your din setting is low enough itll do it for you, but i mean com one, what are you really going to do? reach down with your hands while moving and push with your fist? sounds like a recipe for cartwheeling and not being able to control anything that happens right after to me.

i'd assume he's talking about the euro technique where they roll to release from the toe. this assumes you did it while you still had some control and your din is low enough. for tele w/o releasables, i'd try to flip the heel bail before i got moving too fast. but don't kid yourself, once that snow starts moving you're along for the ride and have very little control even in small slides.

[hutash]

The only way I can see ditching your skis as practical is if you are skinning and start a slide, or if you are below a slide and see it coming. There was a thread today that mentioned a slide is Wash. that hit a group having a break. They were all out of their skis (lost all their gear, but none buried). I have never been in a slide, so I am talking out my ass, but how many times in ski porn have you seen them start slides and still ski out of them. That seems the best way to go, if you are skiing and can manage to stay upright. Even if you do get caught, by staying in the upper part of the slide there is less snow to get buried with.

[mtnbikerskierchick]

so he doesnt speak of "all cases" but "most cases", i'll take that as if you're near the edge of slab and have a chance to ski out then you should go for it. i guess trying to calculate whether to try to ski out or get rid of your skis while already being on a moving slab is, uhh, interesting, and in that point you'll probably end up doing what your instincts tell you.. so i'll quote what lou wrote on wildsnow

Here's an example of where skiing out was probably a good idea.
http://www.tetongravity.com/forums/s...ad.php?t=63690
Goldenboy would probably have not even become a maggot had he not found an escape route out of this avy.

[AltaPowderDaze]

how many times in ski porn have you seen them start slides and still ski out of them. That seems the best way to go, if you are skiing and can manage to stay upright. Even if you do get caught, by staying in the upper part of the slide there is less snow to get buried with.

if your momentum is greater than and stays greater than the fracturing slope, then that's a good idea. for those of us who don't ski 50+ mph in the bc it might not always be practical. if you try to ski out and fail, you just put yourself lower on the track with more snow above you. when it breaks you have only a couple of seconds to get off or ahead of the fracturing snow. after those 2-3 seconds the snow is in control and you are going for a ride. keep in mind that it is rare for a good skier to be able to ski off a fracturing hard slab.

[Camel Toad]

for tele w/o releasables, i'd try to flip the heel bail before i got moving too fast. but don't kid yourself, once that snow starts moving you're along for the ride and have very little control even in small slides.

i got caught in a slide with non-releasable tele bindings on. i did just what you stated, bent down to flip the heel bails, which then put my torso deeper into the flowing snow, which then flipped me upside down, never did get to the heel bails. won't be doing that again, but then i don't tele anymore.

swimming definitely helped in this instance, as it "kept me up" but it was a soft slab. haven't been in a big hard slab/violent avy so can't comment - but if that day comes (shudder to think) i'll be trying all i can to keep an avylung in my mouth, with swimming secondary.

[eirikainersharp]

As I understand it - the brazil nut effect would need a turbulent component of avalanche flow to really work. There is still alot of debate as to whether there is a turbulet compomonent to dry avalanche flow (I'm not talking about the turbulence of the dust cloud). Vollemy first proposed it back in the 50's but there is no scientific evidence that actually confirms his idea. Summit - did Atkins mention anything about that when you heard him talk?

[summit]

Eirik - That is a very good point. You are testing my memory here. It was over a month ago. He showed modeling of turbulent flows but I cannot recall wether he specifically said there was a turbulent component in dry avalanches.

I would presume a dry avalanche is more laminar but that portion is hardly something I posess scientific expertise in.

I think part of the problem is that the victim won't have a whole lot of time to analyze the avalanche coming at them and then decide whether to do one thing or the other... they ought to have something ingrained in their head before hand... just speculating...

[goldenboy]

I think part of the problem is that the victim won't have a whole lot of time to analyze the avalanche coming at them and then decide whether to do one thing or the other... they ought to have something ingrained in their head before hand... just speculating...

Exactly. In my one avalanche experience, I was in such a white room washing maching that I couldn't have kept my hands near my face, or dealt with an avalung, or tried swimming, and I certainly couldn't have tried to take my skis off (in fact, I think it would be difficult to take my skis off on a low-angled groomer while going 20mph). It was really more like tomahawking down a steep slope than anything else. In the avalanche I was in, or the couple of times that I have really tomahawked down a slope, my main concern was protecting my head and torso from injury until I started slowing down, at which point you can try to dig an edge in or swim or whatever.

Which was the main point of the story that MBSC linked to- after that experience I almost always have a couple of options unconsciously lined up in my head if things were to go wrong, because there's basically no time to think about it once shit happens. Anyway, those are my thoughts...

[AbsolutStoli]

i can understand trying to get rid of your skis, as those would probably act as an anchor, but why get rid of poles? if they are on your wrists and you are getting your hands in front of your face, if you can get the poles under your arms cant you use them to try and ID your position (if youre shallow enough)? i mean, every little bit helps, right? ive never been in an avalanche so i have absolutely no idea how restricted your movement would be even if your hands are in front of your face...so i dont know.

do avalanche victims typically know which way is up vs down by sensing the effects of gravity in the head? or is the blood pumping so hard at that point that you really cant tell which way youre facing?

what about your position if caught in a slide? should a person try to stay upright and vertical or horizontal and flat? either way you are suspended in snow, but if you are flat arent you a bigger target for a probe to hit you than you would be if youre vertical?

sorry if these are all stupid questions...

[Camel Toad]

i can understand trying to get rid of your skis, as those would probably act as an anchor, but why get rid of poles?

Poles or skis can and will act like levers that can apply more torque to your body. Not as much of a problem with poles, but I always ski with the straps off, I would rather lose a pole than wrench my shoulder or have my hand pulled away from my face in an avy/fall because of one.

do avalanche victims typically know which way is up vs down by sensing the effects of gravity in the head? or is the blood pumping so hard at that point that you really cant tell which way youre facing?

depends on the size/violence of the slide, if it is big with drops etc in it you will have no idea which way is up until you stop and you sort out what has happened. have you ever gone over the lip while surfing, which way is up?

what about your position if caught in a slide? should a person try to stay upright and vertical or horizontal and flat? either way you are suspended in snow, but if you are flat arent you a bigger target for a probe to hit you than you would be if youre vertical?

sorry if these are all stupid questions...

If you are carried by a big slide odds are you have no control over this (swimming may help a bit, but that is the debate of this thread) I would want my head as high as possible, less to dig out to get to air that way. Once the snow stops and hardens you may not be able to move at all.