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Giant Gulmarg, Kashmir Avalanche - Skier ? Think escaped

 Poster: A snowHead
Poster: A snowHead
Happened behind him, the scale is huge
[url=https://unofficialnetworks.com/2018/03/07/skier-remotely-triggers-large-avalanche-in-gulmarg/][/url]

Oops so sorry, weird this URL did not show up when i use the code for URL
https://unofficialnetworks.com/2018/03/07/skier-remotely-triggers-large-avalanche-in-gulmarg/

And the question I had was why one would think the Skier 'REMOTELY' triggered the avalanche, skier was well under the terrain where this behemoth slide began, the fissures occur way above the skier and to skiers right first and then behind where he came from (don't know if skier is a he or she by the way). Am asking, those who know about avalanches - please elaborate/educate.

And yes, thanks, that TGR story refers to the same avalanche!


Last edited by Poster: A snowHead on Sat 26-05-18 22:42; edited 3 times in total
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
Do you mean this?

https://www.tetongravity.com/video/news/nightmarish-avalanche-in-gulmarg-will-leave-you-speechless
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
@termintermed, maybe a link would be useful?
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I have trigger an avalanche more than 500m from where I was skiing. There was a very weak layer of buried surface hoar that collapsed as I skied along a very flat ridge. The whole slope settled with a distinct boom and then a steeper slope released. It looks like the area just above the skier went then the the ridge line was triggered probably by vibrations from the first release.
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 Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
It's surprising how far you can remotely trigger an avalanche.

http://youtube.com/v/kzjmvn6qrOs

Here's the clip again. Difficult to see where the skier actually triggers the avalanche. Just my take on it but suspect it is when the skier skis over a roll at around the 19 sec mark

http://youtube.com/v/L6tCr4eszQk

For a slab avalanche the snow is typically like a sponge layered cake with sugar like crystals inbetween at least two layers (e.g. burried surface hoar or depth hoar). On undulating terrain the sponge layer is often less deep on the upside of the rollover to the downside, caused by the wind blowing snow around.
There's evidence to suggest the wind has blown over the ridge and down the hill towards the camera depositing snow this side of the ridge while creating the cornice at the top. To me the rollover around the 19 sec mark looks to be where the the skiers weight has punched through and broken the layer. What I find interesting about this avalanche is that while it's normal for a slab avalanche to break above the skier/boarder the whole slope from the skier to the break normaly releases. In this case the surface snow immediately above the skier initialy remains intact.
This might be because there are two bad layers higher up but only the deeper bad layer lower down. From the skiers shadow it looks to be a North to North east facing slope, it's possible that the sun fell on the lower slope with enough intensity to remove a layer of surface hoar but not higher up where the slope is steeper and thus shielded more from the suns rays. This looks to have then released only that shielded section rather than the whole slope right down to the skier. It's also possible the break occured at the 15 sec mark and a crack shot camera left horizontally across the slope. Suspect the avi warning would have been saying not to ski north facing slopes.
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You'll need to Register first of course.
More info on snow layers etc


http://youtube.com/v/O3_DZXS5vI0
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 Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
Some education. That CB crew are on a flat-tish slope lower down, and they see a crack and that propagated up high and released the slab several hundred yards away and a lot higher. Totally new to this viewer, remarkably dangerous Shocked Thanks much.
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 After all it is free Go on u know u want to!
After all it is free Go on u know u want to!
The skier was an experienced heli-guide and veteran of the terrain as per web blogs, so knew terrain and any conditions that day, which were 'considerable' as per Gulmarg Avalanche Advisory: https://www.facebook.com/groups/gulmargavalancheadvisory/

This part is a physics and force propagation question - trying to understand it : @DB noted "What I find interesting about this avalanche is that while it's NORMAL for a slab avalanche to break above the skier/boarder the whole slope from the skier to the break normaly releases. In this case the surface snow immediately above the skier initialy remains intact. " Explain "NORMAL"

and the rest - how the crack propagates and also this 'whumpf' phenomenon...

Reason is also personal as recently my boy skied St Anton in Valluga, with a very experienced guide and on Level 3+ day, no one there really, and slopes looked great but guide was uber-cautious, with distancing rules followed religiously, and he was looking 'UP' and far above all the time before they 'cut' some slopes making their way down the Pazieltal Valley to Zurs. He clearly chose the line skied and it was all basically virgin as there were only 3 other skiers that day , it was around 2pm by then, in the vast expanse. Looking at this Gulmarg video and the others above most educational explanations above, it seems that is what was on guide's mind throughout was this sort of remote release ABOVE THEM - so am interested in learning more! Son is a teen, doing teen things right now naturally Cool
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The 'whumpf' occurs when, for one reason or another, a hitherto bonded layer of snow that has developed a hollow layer beneath it, suddenly gives way. This causes a 'whumpf' sound as the layer drops and air escapes.
Sometimes the lower layer has 'decomposed' to leave the gap but more commonly, the upper layer, on a convex slope has bonded then expanded, causing it to lift slightly from the layer below. Leeward slopes that 'farm' windblown snow are particularly prone to this. For a very small expansion in the snowpack, a huge area can be lifted in this way, creating very long lines of stress.
It may not be the top layer - it often isn't - but the forces are there, beneath the surface. A new layer of snow on top applies force evenly so can increase the size of all the forces in play while not necessarily disrupting the equilibrium of them.
A skier (or 2 or 3) moves onto this raised layer, causing shifts in the lines of force as they go. At some point, their weight is enough to cause it to give way. Unfortunately, one place where their weight is likely to make the greatest difference, is when they're near the middle of the raised slab. Thus, they find an area all around them collapses and the sudden injection of kinetic energy causes it to disintegrate immediately into a fluid state.

As for the 'norm' of causing slides above:
Snow above rests on snow below. Huge layers can be bonded loosely and lines of stress can be hundreds of meters long.
Anyone can conceive that one might disturb just enough loose snow to cause snow a few feet above them to shift. Well if that snow above, itself causes snow above it to shift, and so on, (and it could be as little as half an inch) that could cause a huge shift in the forces which, until that point had held a loosely bonded layer taut. Hence the potential for fracture lines appearing to initiate some way from the skier that caused them.
Think of your car windscreen, covered in snow. The car is cold and so the snow is stuck to it, all over. You remove the snow at the bottom and the rest stays in place. However, run the windscreen heater a little: it all looks outwardly the same but the bond between the snow layer and the windscreen is weakened - now, you remove snow at the bottom and the snow above slides straight down. In this respect, the mountain is basically just a big windscreen Toofy Grin
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termintermed wrote:
This part is a physics and force propagation question - trying to understand it : @DB noted "What I find interesting about this avalanche is that while it's NORMAL for a slab avalanche to break above the skier/boarder the whole slope from the skier to the break normaly releases. In this case the surface snow immediately above the skier initialy remains intact. " Explain "NORMAL"

and the rest - how the crack propagates and also this 'whumpf' phenomenon...


When a slab avalanche occurs the skier is normally below the break point and the whole section of slope releases.


http://youtube.com/v/zp3wB1Xs5bI


A remote trigger that causes a section further up the slope to release can happen but it's less likely.
As Admin says the Whumpf is the bonded layer of snow dropping.


termintermed wrote:
Reason is also personal as recently my boy skied St Anton in Valluga, with a very experienced guide and on Level 3+ day, no one there really, and slopes looked great but guide was uber-cautious, with distancing rules followed religiously, and he was looking 'UP' and far above all the time before they 'cut' some slopes making their way down the Pazieltal Valley to Zurs. He clearly chose the line skied and it was all basically virgin as there were only 3 other skiers that day , it was around 2pm by then, in the vast expanse. Looking at this Gulmarg video and the others above most educational explanations above, it seems that is what was on guide's mind throughout was this sort of remote release ABOVE THEM - so am interested in learning more! Son is a teen, doing teen things right now naturally Cool


Spacing skiers is normal procedure to reduce the localised strain / weight on the snow pack. The more weight then the deeper the skier/ boarder will affect the layers below. Spacing also reduces the chance of a multiple burial.
During a recent avalanche training course we were shown a clip where 3 skiers set off to ski a slope each taking a different route. It was only when the skiers came within close proximity of each other than the avalanche released.

A cornice indicates snow has been blown in and suggests the presence of wind slabs formed by the wind compressing snow onto the leeward side of the ridge.
https://avalanche.org/avalanche-encyclopedia/wind-slab/
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Appreciate the detailed explanations, the videos and breaking down the different forces at play.
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And love to help out and answer questions and of course, read each other's snow reports.
Thereís some good stuff there but a few stray points as wellÖ

admin wrote:
Sometimes the lower layer has 'decomposed' to leave the gap but more commonly, the upper layer, on a convex slope has bonded then expanded, causing it to lift slightly from the layer below. Leeward slopes that 'farm' windblown snow are particularly prone to this. For a very small expansion in the snowpack, a huge area can be lifted in this way, creating very long lines of stress.


If you think more about this I think it will be apparent that anything that expands would tend to get weaker and not stronger. Slab building is about that volume or layer of snow getting stronger. Forcing things together isnít going to expand them (not in newtonian objects at least).

A slab is being built when snow is getting compacted from the large complex crystals that fell from the sky. Those large crystals donít bond very well which we all recognise as the loose powder snow we like to ski. The process of consolidation is about how those crystals change and form strong bonds. There are two main ways that happens. The first is a temperature metamorphosis which I think is self-explanatory (normal consolidation). The other is a mechanical metamorphosis which occurs in a couple of ways. Thereís a mechanical transport caused by wind building the infamous windslabs and a compressive force. The latter tends to a cohesion by sintering, that sounds complex but any schoolchild will be expert in that as they take handfuls of loose snow and pass them from hand-to-hand forcing air out and creating bonds. In these cases, the concept is fairly simple, the smaller metamorphosed crystals just have more contact and form stronger bonds. This is why igloos are built from compressed, windblown snow - itís stronger.

As mentioned, the whumpf is no more than the air being expelled from a layer of snow below a slab.

admin wrote:
A skier (or 2 or 3) moves onto this raised layer, causing shifts in the lines of force as they go. At some point, their weight is enough to cause it to give way. Unfortunately, one place where their weight is likely to make the greatest difference, is when they're near the middle of the raised slab. Thus, they find an area all around them collapses and the sudden injection of kinetic energy causes it to disintegrate immediately into a fluid state.


No, this is bad mechanics. Thereís no reason for that to be true and slabs are far more complex objects than that suggests. I think weíre aware of the idea of spatial variability and that itís a non-uniform surface - if we didnít have those problems to work with then predicting where a slab might fail would be somewhat easier. That said, on simple, lower angled slopes I can generally find that point fairly easily.

admin wrote:
Think of your car windscreen, covered in snow. The car is cold and so the snow is stuck to it, all over. You remove the snow at the bottom and the rest stays in place. However, run the windscreen heater a little: it all looks outwardly the same but the bond between the snow layer and the windscreen is weakened - now, you remove snow at the bottom and the snow above slides straight down. In this respect, the mountain is basically just a big windscreen Toofy Grin


Iím not sure I really understand that but I can say a car canít be a good example as itís freestanding, uniform and a cold object so it wonít behave like a slope at all.

Incidentally, the reason you see the whole slope fail apparently nearly simultaneously in the video is due the how fast failures propagate, tests show thatís around 20m/sec
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 So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
ise wrote:
Incidentally, the reason you see the whole slope fail apparently nearly simultaneously in the video is due the how fast failures propagate, tests show thatís around 20m/sec


The engineer in me started thinking that's approx 45mph, why so fast and why so far?

I'm thinking this could be because of ....

1. The slab being under tension from the hanging weight of the slab itself which increases greatly once the slab is broken and there is little to then support it from underneath. e.g. Ripping like a fabric under tension as it is slashed.
2. The air pressure under the slab. e.g. Popping like a ballon. Not sure if there is a static pressure difference or this is purely due to the slab falling onto the loose layer below and squeezing the air out which in turn causes a whumpf sound and enough pressure to blow itself apart.
3. Structural failure with the crack lines follwing the weakest part of the structure while the structure fails down like a pack of dominoes until the snow runs out or the structure is strong enough not to fail (examples = just over the crest of a slope, less steep section, end of weak layer etc.)


Last edited by So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much on Wed 30-05-18 13:54; edited 2 times in total
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 You know it makes sense.
You know it makes sense.
termintermed wrote:
...And the question I had was why one would think the Skier 'REMOTELY' triggered the avalanche, skier was well under the terrain where this behemoth slide began, the fissures occur way above the skier and to skiers right first and then behind where he came from ....

Although the timing and proximity suggest that this one was skier-triggered, it isn't impossible that it was natural, particularly at this time of year.

termintermed wrote:
...Reason is also personal as recently my boy skied St Anton in Valluga, with a very experienced guide and on Level 3+ day, no one there really, and slopes looked great but guide was uber-cautious, with distancing rules followed religiously, and he was looking 'UP' and far above all the time before they 'cut' some slopes making their way down the Pazieltal Valley to Zurs. He clearly chose the line skied and it was all basically virgin as there were only 3 other skiers that day , it was around 2pm by then, in the vast expanse. Looking at this Gulmarg video and the others above most educational explanations above, it seems that is what was on guide's mind throughout was this sort of remote release ABOVE THEM - so am interested in learning more! Son is a teen, doing teen things right now naturally ....

A big reason for looking up is to check for the presence of others somewhere on the slope, who may trigger a slide onto you.

On a 3+ day there probably WILL be natural slides - somewhere! You can reduce the risk of being caught by careful route selection, observation, spacing, snow tests, local knowledge etc - but unfortunately you can't reduce it to zero.
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 Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
Reading through the explanations above and with the slightly varying perspectives offered on the physics and properties of snow, am still frankly a bit hazy on how skiing way below a slope can trigger an avalanche at quite some distance away and above the skier. Clearly it happens and the guide in the case with my boy was very vigilant (there would be no other skiers above them where they were in the Valluga, almost zero chance, only access was roughly the way they came and Valluga North, which was the other side of that valley sort of area).

I did find this:
http://www.nbcnews.com/id/28439240/ns/technology_and_science-innovation/t/how-deadly-avalanche-can-be-triggered/#.Ww7oOy-ZMcg

and this Thesis study focusing precisely on the question posed about a phenomena not well understood but very real and so dangerous as prevention or mitigation is incredibly difficult if I understand all I have read and see (the videos):
https://schulich.ucalgary.ca/asarc/files/asarc/BCJohnsonThesis.pdf

Fascinating.

One explanation resonated, i.e. propagation of a structural failure in the snow at the skiers feet, which propagates - but 'uphill' , that has to require energy and gravity is acting in the other direction, but so conjecture from all above - crack propagates along weakness in structure along line of least resistance and even uphill and then all hell breaks loose maybe ?
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 Poster: A snowHead
Poster: A snowHead
DB wrote:
ise wrote:
Incidentally, the reason you see the whole slope fail apparently nearly simultaneously in the video is due the how fast failures propagate, tests show thatís around 20m/sec


The engineer in me started thinking that's approx 45mph, why so fast and why so far?


It's a general case figure, tests produce results around the 50m/s as well. In fact, there are outliers that are faster than that. This is quite slow really, in other mediums waves travel much faster.
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person


^^ We 3D Printed an enlarged MRI scan of a layer of buried surface hoar kindly provided by the SLF. What struck me about it was the amount of air space between the large (and fragile) hoar crystals for the top layer to collapse into.





^^ At the other end of the spectrum, in January I came across a section with an 'air gap' caused by depth hoar transformation, despite super deep snowpack else where. My guess is wind action had thinned out the snow pack under a steep North facing ridge causing a localised big temperature gradient. We turned around.

Video - https://flic.kr/p/235M4kN
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
A friend lost a pole down a similar "air gap" while skiing on-piste. It dropped completely through a hole in the snow and disappeared!
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Air gaps are most interesting, I wonder. In our recent Arlberg Trip Report, where the 15 year old was the skier with his WhiteGuides pal Manfred (our mountain guide), after the Valluga West descent in the Pazieltal valley, at some place on one of the smaller hillsides above a pitch, you can see him push his pole in relatively easily all the way to the top of the grip, and it went in with minor resistance and then sank right in, and it was not champagne powder. Powder yes, but relatively firm ankle deep in that zone. Wonder if that was a sample of layers on layers with a gap in between, as shown above.
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