@AndAnotherThing.., that was compiled from data reported by the rescue services by Bruger et al. It seems to exclude the 20% killed during the slide or within seconds after - impact, crushing. After that you've got about 15 minutes breathing time while your breath condensates in the snow forming a barrier and CO2 builds up in the snow around you. In the next 15 minutes 70% of victims will be dead, the remainder have a larger air pocket and another 20% will die of hypothermia over the next couple of hours leaving 10% who may be found 2, 6 hours or even a couple of days later.
Rescue services are probably taking around 30 minutes to reach an avalanche scene from the time of burial assuming you can get a phone signal due to the introduction of the faster EC145 helicopter in France. Pisteurs perhaps 15 minutes, @idris may have more accurate data so really you are relying on your mates to rescue you alive.
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
davidof wrote:
@AndAnotherThing.., that was compiled from data reported by the rescue services by Bruger et al. It seems to exclude the 20% killed during the slide or within seconds after - impact, crushing. After that you've got about 15 minutes breathing time while your breath condensates in the snow forming a barrier and CO2 builds up in the snow around you. In the next 15 minutes 70% of victims will be dead, the remainder have a larger air pocket and another 20% will die of hypothermia over the next couple of hours leaving 10% who may be found 2, 6 hours or even a couple of days later.
Rescue services are probably taking around 30 minutes to reach an avalanche scene from the time of burial assuming you can get a phone signal due to the introduction of the faster EC145 helicopter in France. Pisteurs perhaps 15 minutes, @idris may have more accurate data so really you are relying on your mates to rescue you alive.
Thanks. I'm putting together a lockdown presentation\training and wanted to highlight why carrying the kit and being able to use it is critical.
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?
rescue in the Belledonne, call went in at 13h45, rescuers arrived on the scene at 14h30. The helicopter had difficulty getting close to the incident. In the end the pilot touched a skid on a rock allow the crew to disembark.
Quite a lot of natural activity at the moment as it has both thawed and rained. An Italian ski instructor was killed in Courchevel touring in what seems to be fairly risk conditions (from the comfort of my computer screen this pm, I wasn't on the ground).
Looking at the various bulletins there is a risk of remote triggering. Also of small slides leading to quite big accumulations, this video from the 12th being an example
if the skier had been taken they may have hit the rocks below and this could also have caused a relatively deep burial for what is a small surface slab.
Looks like no-one hurt fortunately, but extra significant because this is a highly travelled spot with common wacky skin track, appropriately known as "Suicide Skintrack" apparently, right up where all the snow now at the bottom used to be!
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
Lots in Tignes today, regies des pistes reporting 4 avalanches involving skiers. One buried under 3m of snow in Vallon we La Sache. And that's a serious skin to get there.
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
Yes my correspondent in Grindelwald has remarked several times at ridiculous lines folk are skiing.
Makes me wonder if the Swiss situation is simply "hey we have lifts running let's rip it"!
Grindelwald was locally posting a level 4 this morning contrary to the nationaly published level 3.
@Mother hucker, Remote triggering means there is a weak layer from where the trigger is (you) right up the slope to where the slab has enough angle to slide.
@davidof Thanks for some very interesting information in this thread. I have also seen reports of remote triggering of slabs from both above and below recently and I have a question with a view to trying to understand it a little better. Is it really the weak layer that needs to continue to the steeper slope or the slab itself? I'd imagined it was really the slab that had to be continuous so that a crack in it could propagate. As long as there is a weak layer that deforms somewhere (e.g. under a skier), the overlying slab can crack. Once cracked, the propagation of the crack depends on how wide the continuous bonded layer (slab) is and what other forces have been disturbed but I'd have thought that crack, once started, could continue through the slab regardless of the weak layer being present under the whole slab. It may be rather an academic point but I'm taking the view that anything I can understand about this is grist to the mill. Thanks.
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?
@davidof Now I'm thinking maybe the PWL performs a double role. Firstly inadequate support of the slab allowing the slab to crack, secondly a nice slippery surface for the disintegrating slab to move on. Or maybe the PWL is relatively strong in compression but it's granular / ball bearing / slipperyness means the overlying slab is held in place only by it's own bridging/integrity which is easily disturbed by a passing skier. I still think the slab could slide on any slippery base once it's started to crack though. Any input appreciated.
^ an avalanche needs both a weak layer and a slab to start. However once it's going the momentum and energy can dislodge an entire slope.
Goggle the concept of "hot spots". The theory is that if you trigger one of those then entire slope can be triggered.
That's how I'm seeing it but I was interested in @davidof's comment that for an adjacent slab to slide the PWL needed to extend all the way to it
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
^ the weak layer just needs to be large enough to release a slab. If that has enough momentum then it might trigger other parts of slope that could have perhaps otherwise supported weight of skier.
Think of it like a Jenga block. If you remove the wrong piece then entire tower will collapse (taking previously stable blocks with it)
After all it is free
After all it is free
@Ed_sec, as Haggis has already given you an answer I won't add much but just to say that you, as an 70-80kg skier are pretty inconsequential compared to a slab of tens to hundreds of tons of snow. If you look at the videos I've posted previously you will see it really is the weak layer collapse that triggers the slide, not the skier's weight on the slab.
This video from Francois Hivert demonstrates the principal
Francois touches the weak layer, this collapses like a house of cards, or kapla if you like and this gives the slab the momentum to break away. The weak layer is the key. The cracks in the snowpack are a consequence of the weak layer collapsing, not your weight breaking the slab, if I understood you correctly.
To talk about weak layers. Where I was in the Chartreuse yesterday whole slopes were covered in surface hoar crystals. Since then there has been a lot of wind (foehn) from S to N transporting snow. You can just about see it in this picture I took from the Petit Som as the wind blows over the small col depositing snow on the lee (left) side.
and of course today lots of slab activity on, well you guessed it, north sector slopes where those slabs formed.
If we take the Aravis where there were a couple of incidents with burials we see this in the bulletin:
There has been no recent fresh snow but a lot of snow transport. This has lead to temporary instabilities even at lowish altitudes (the fatality in the Jura today was at 1350 meters) with soft slabs on those PWL above 2000 meters. The Jura avalanche buried the victim under 150cm of snow. People probably were not expecting avalanches at this altitude but the second you exited forested trails onto open lee slopes the danger was there.
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A little bonus, this video from avalanche control in the Vosges last Friday in the Hohneck couloirs (there was a fatality on Sunday)
@davidof, Just to clarify the surface hoar situation you described. The weak layer was the surface hoar you described as opposed to a buried depth hoar layer being overloaded wind transported snow ?
I ask as often wind will destroy surface hoar, but on sheltered lea slopes it will be protected and lurk ?
snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
AndAnotherThing.. wrote:
@davidof, Just to clarify the surface hoar situation you described. The weak layer was the surface hoar you described as opposed to a buried depth hoar layer being overloaded wind transported snow ?
I ask as often wind will destroy surface hoar, but on sheltered lea slopes it will be protected and lurk ?
yes surface hoar is very fragile so it creates a lot of spacial variability which makes it hard to judge. However the avalanches yesterday seem to have gone on a temporary weak layer created by the windblown snow itself. This is often the case with fresh snowfall too. The surface should stabilize in a couple of days. I just heard the slope in the lee of the photo I posted above went yesterday - skier triggered windslab. It is a notorious slope for avalanche accidents.
Last week there was a lot of avalanche activity on a weak layer around 30cm under the snowpack, I'm not sure what caused that as it was very widespread around here but I suspect surface hoar as the snow fell without wind.
Yesterday they bomb the hell out of the 7 Laux - probably worried about a big accident as there are lots of people touring there at the moment.
We've been very lucky in France this season, a lot of near misses, CH not so much.
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
@davidof Thanks for all this info. I think I have now (at last) grasped something that was not previously totally clear in my mind. I had understood a weak layer as having so little integrity that it made a good surface for a slab to slide on but had limited capability to propagate fault lines within itself. Now I realise that although the weak layer is fragile it does have some structural integrity and it is when that breaks that everything starts to move.
So although, as you say, a skiers weight may not be enough to break a surface slab the extra weight of the skier on that slab can be enough to overload the PWL underneath. I've seen many vids of people cutting chunks of slabs that, with a little tap, slide off the PWL below but from just looking it's not clear if the tap is just disturbing the delicate friction between the layers or actually causing a structural failure in the PWL. I now understand it to be the latter. Thanks so much for clarifying and please correct me if I still have this wrong. Now back to Bruce Tremper for me!
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
From an FB post by Xavier De Le Rue...
Quote:
The perfect bluebird powder day… the perfect day from hell.
Verbier lost two riders on Monday in separate avalanches, I will tell you the story of one, because I hope in doing so I can make you think twice and prevent another.
I was up riding with a large group, whose ability I didn't know so I took a "safe” option and whilst riding we witnessed a large avalanche coming through “Rock n Roll couloir”.
I went straight to search the debris, seeing someone buried to their waist with their airbag pulled I felt relief that they were not buried and went to check that they were fine before continuing the search.
It was my friend, and he was not fine, through the avalanche he had sustained a head trauma that ended his life. I felt totally useless, overwhelmed, I was meant to be the expert, I have made videos on how to deal with this situation - but it was horrific. I went through the motions, called 112, directed others to search and started CPR, because someone told me I should, but I felt hopeless. I want you to know this so that you think about this before you drop into a line, you take all the precautions, you know your equipment, you turn back or even stay home.
My friends were riding a line that would have been one of my first choices on that day had I not been with the large group. The Couloir they were going into had slid two days before - theoretically making it a safe option- but they had to cross a pocket of snow to get to the entrance. This is what slid, I have never seen it slide on that scale in my whole time in Verbier.
Everything has changed and we have lost a friend.
My thoughts are with the friends and families of my friend and the young instructor who lost his life on Monday, as well as the six other people who lost their lives in avalanches over the weekend.
Photo courtesy of Melody Sky Photography - in loving memory of those we have lost to the mountains.
You know it makes sense.
You know it makes sense.
@ulmerhutte, I read that, food for thought.
I knew a girl that was buried while out skiing with some pisteuers, she was located and dug out very quickly but said it was a truly terrifying experience, she said that once she stopped moving she was completely frozen solid and couldn’t even blink her eyes.
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
This is some scary shite in an area we tour in a lot, I've sent Laurent a map with where I think it was exactly but looks to have come over the Galibier road a route we do about 20 x a season!
This is some scary shite in an area we tour in a lot, I've sent Laurent a map with where I think it was exactly but looks to have come over the Galibier road a route we do about 20 x a season!
@weathercam Thanks for that one. Spectacular indeed and just as well the guy was attached to a kite, it may have got him out of the worst of it. Did I see a tiny figure right at the top of the break who presumably triggered it? Or was it a depart spontané ?
And another about 1m new snow coming for next week. Scary
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
I've noticed a lot of the accidents and fatalities (in Switzerland and elsewhere) have involved experienced people. Guides or experienced locals. Assuming they are not knowingly taking more risks than usual it suggests the conditions are currently unusually tricky for hidden dangers.
I've noticed a lot of the accidents and fatalities (in Switzerland and elsewhere) have involved experienced people. Guides or experienced locals. Assuming they are not knowingly taking more risks than usual it suggests the conditions are currently unusually tricky for hidden dangers.
Nearly all avalanche accidents involve professionals and experienced locals, especially so this year as they are the only people skiing.
As for experienced locals. There are three kinds of experienced locals, those who don't go out or opt for safer lines in sketchy conditions, those who really are just unlucky and those who don't know jack shit.
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
@davidof, is there a role this year for lack of skier compaction of weak layers, due to less skiers?
After all it is free
After all it is free
davidof wrote:
Ed_sec wrote:
I've noticed a lot of the accidents and fatalities (in Switzerland and elsewhere) have involved experienced people. Guides or experienced locals. Assuming they are not knowingly taking more risks than usual it suggests the conditions are currently unusually tricky for hidden dangers.
Nearly all avalanche accidents involve professionals and experienced locals, especially so this year as they are the only people skiing.
As for experienced locals. There are three kinds of experienced locals, those who don't go out or opt for safer lines in sketchy conditions, those who really are just unlucky and those who don't know jack shit.
Thanks for the link. I don't think I read it all the first time. There's a lot of stuff in there which I'll re-read carefully.
It sounds like you don't think conditions are any trickier than usual. Is that right?
I guess it's true that many or most accidents happen with a guide or person familiar with the place but I was wondering if the spate of these PWL avalanches recently is suggesting the conditions are trickier than usual. Most old school locals my way are quite cautious regarding slope angle and obvious wind slabs and loading (which can be very marked near ridges) so I hope they/we manage to keep out of trouble. I also think there are cultural differences between the old school narrow ski guys who climb the same hills summer and winter and the younger more winter focussed, fat ski freeride guys who want steeper slopes.
But anyone can get caught if you're on the wrong slope on the wrong day. We just have to keep learning, observing and practising safe travel as best we can
You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
peanuthead wrote:
@davidof, is there a role this year for lack of skier compaction of weak layers, due to less skiers?
It must have some effect but also frustrated skiers with the repeated lockdowns and I think overconfident airbag users who probably wouldn't be doing what they are doing without an airbag.
Ski the Net with snowHeads
Ski the Net with snowHeads
Ed_sec wrote:
It sounds like you don't think conditions are any trickier than usual. Is that right?
Read my first post in this thread. There is clearly a generalized instability affecting the Alps, Jura, Vosges and Massif Central from quite low altitudes. Currently a time to play it safe.
The thing is, lots of years we warn of a dangerous avalanche situation developing then nada but the stopped clock (me) is right this year.
FAQ
Poster: A snowHead
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