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Avalanches and predisposing conditions

post #1 of 13
Thread Starter 
While reading the numerous threads surrounding the recent avalanches I've noticed that frequently the snow pack instability was blamed on a deep layer of rain crust and/or a layer of "rotten snow" (depth hoar?).

What are the thoughts on snow (in)stability for the weeks and months to come?

Have the slides taken down the bad layers?

Under what conditions can such layers bond and become more stable?
post #2 of 13
Quote:
Originally Posted by kawo View Post
What are the thoughts on snow (in)stability for the weeks and months to come?
Those layers are going nowhere, fast.
post #3 of 13
Quote:
Originally Posted by kawo View Post
While reading the numerous threads surrounding the recent avalanches I've noticed that frequently the snow pack instability was blamed on a deep layer of rain crust and/or a layer of "rotten snow" (depth hoar?).

What are the thoughts on snow (in)stability for the weeks and months to come?

Have the slides taken down the bad layers?

Under what conditions can such layers bond and become more stable?
I basically an armchair quarterback this year, but slightly better informed than the other arm chair quarterbacks.

the bad layers are still there, they arent moving from any control work.

thats how thick the jackson hole rain crust is its almost impenetrable as long as that crust remains its will still be dangerous.

the conditions that would make it stable are warmth. This isnt 100 percent and nothing is in snow science. sun light and warmth will pack down the snowpack in laymans terms. Jackson Hole crappy exposure will actually help getting more sunlight on the slopes than say snowbird.

The wasatch range in utah is only high danger(down from extreme) now but its like playing russian roulette with very large bombs. The snow pack above the rain crust would be very stable stand alone. In fact if it didnt snow till the first big storm December 8th and then just just kept dumping like it did this year. It would be a very stable snowpack. there would be no depth hoar there would be no rain crust. the snow pack would be homogeneous top to bottom which is the safest kinda of snow pack there is.

Id hate to say but in my very amateur opinion I think something north facing in utah or wyoming will go while open post controlled towards the end of the season IF it doesnt heat up at all and break that rain crust down.
post #4 of 13
Tahoe area is experiencing about a week of warm temps, 33-40. hope it will fuse the depth hoar to the now warming and settling snow pack. anyone care to comment? we have had years whre certain slopes never held new snow due to rain crust/ice layers.
post #5 of 13
I have been too busy to dig any holes lately, but it is possible that areas that slid cleared out the ice and a lot of the buried hoar. I did see a lot of dirt in the slide paths. This is good if the new snow that fills these areas in comes in fairly homogenous. It is a good year to know where the slides have happened. Short of these old layers sliding away, I think they will be with us for a very long time.
post #6 of 13
When I studied this matter as a climber, I was told that the deepest layer is much more resistant to sliding, as it's anchored to the porous rock and soil of the mountain.
Some places will have avalanches every time snow accumulates to a certain depth and weight, and the bottom layer will remain untouched until next summer. These places will never be safe to ski this season.
post #7 of 13
Quote:
Originally Posted by Phlogiston View Post
When I studied this matter as a climber, I was told that the deepest layer is much more resistant to sliding, as it's anchored to the porous rock and soil of the mountain.
Some places will have avalanches every time snow accumulates to a certain depth and weight, and the bottom layer will remain untouched until next summer. These places will never be safe to ski this season.
It's not anchored to the porous rock and soil. You can often find mud at the bottom of a pit because the ground stays warm, ussually right around freezing. The anchoring is more of a function of a strong snow layer being wrapped around an object that projects up from the ground like a tree trunk or a rock outcropping. The bad news is that these same things act as stress risers as the snow pack creeps down hill and these anchors are held in place. Also rock outcroppings bring ground heat closer to the surface and thus increase the temp gradient in their immeadiate area. This can act as a trigger point when crossed. Weak faceted snow around these areas can transmit the propogation energy down into deeper layers that would otherwise be below the level typically affected by a skier. Hoar that forms near the ground tends to be weaker, larger, and form faster than surface or mid-pack hoars, because the metamorphic processes, both rounding and faceting, occur faster in warmer layers.
post #8 of 13
Actually, the mud and soil are frozen too, saturated with water, which froze. If the surface is smooth, forget about climbing or skiing there this season.
In springtime you can find chunks of soil and small stones that were ripped out as one piece when an avalanche encountered a projection, and instead of sliding over it, ripped it, and the attached frozen soil, from the slope.
post #9 of 13
Whistler lost two yesterday in bounds on closed trails.
Leaves a bad feeling in the pit of my stomach.
post #10 of 13
I was at Castle Mountain earlier this week awaiting the last measures of Avi control prior to opening the "Red" Chair. Mountain Safety set of an explosive and triggered a slide which was larger and ran longer than expected. I was literally waiting in the lift line with the chair running. About 15 seconds after the first slide stopped, the whole face of the bowl fractured (the crown was about 5-6 feet). This face slid down to the rocks. It will be very unstable for a while to come.
post #11 of 13
predisposing conditions...

Ignorance, Arrogance and Stupidity

normally at least one of the above come in to play
post #12 of 13
Thread Starter 
Quote:
Originally Posted by CEM View Post
predisposing conditions...

Ignorance, Arrogance and Stupidity

normally at least one of the above come in to play

Or just plain lack of luck.
Many reports of people showing the above and getting away with it.
And yet skiing on open IB terrain took lives at Snowbird and JH.
post #13 of 13
Quote:
Originally Posted by CEM View Post
predisposing conditions...

Ignorance, Arrogance and Stupidity

normally at least one of the above come in to play
don't forget desire
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