East Coast Mags: November 8 = Eastern Snow & Avalanche Workshop

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Originally Posted by Jonathan S.

^ Great discussion, thanks!

So before April 25 of 2009, when all three avalanches in Tux were caught on video, only one avalanche in the Presidentials had been captured in action -- this is from March 19, 2005:


https://lh5.googleusercontent.com/-w...th%2Bskier.jpg



Re trees in the crown for the GoS avy, I was focusing on the top left here -- do you think that's more just a coincidence than a factor in the initial fracture?


https://lh6.googleusercontent.com/-o...2Btrees%29.jpg

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i suppose it's possible, but in this case i really think coincidence. reason being is that there was no daytime heating issues at the time of the slide. trees and rocks tend to create weaknesses to point of failure when things are heating up and snow melts causing bonds to breakdown and water percolates down from those features to cause further weakening of the new snow/bed surface interface. sound reasonable? the slope failed a fair bit lookers right, like middle right of the crown line pictured, then shot across both left and right from there. i skied down from the mid crown area of the ridge and pulled the "winning" card from that brittle house of cards quite a ways down from the crown. i'll never that feeling of great snow feeling so very bad.

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Originally Posted by bern43

The accomplished skier thing was said by the guy with his arm in a sling. Could've sworn he mentioned that he had guiding experience. Not sure if he's certified. Either way, a bit of a strange panel. I guess I was just surprised that the people on the panel at an avalanche education event seemed to not understand such a basic concept. The moderator tried to bring it back at the end by mentioning how important it was to be searchable again.

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That was Mark Ritchie. He also said he usually doesn't bring a rope to climb Huntington. Climbers just seem to think that avalanches are far down the list of things that can kill them and usually asphyxiation isn't the cause of death. Which they do kinda have a point - however, to Dale's point, rescuers are going to come try to rescue you, and you owe it to them to be rescueable. I would have liked more discussion among the group, especially when they disagreed on things.

Was wondering if you made it up Bern - was looking around the crowd but its hard to recognize people by their TGR name.

The slab studies presented were the most interesting to me. They also kinda complimented the summit cone avy explanation. As Frank had shown, the facets weren't exceptional, just small facets that had been there for months. However, something changed on that day at that moment and triggered a collapse, which propagated over a wide area. I would guess that there are commonly facets on that slope, the snow never gets that deep, it has prolonged cold periods, etc. If facets are common, the pitch is 32 degrees, and it doesn't avalanche frequently, it must be the slab that keeps it in place.

32 is the slope angle I remember Frank giving. Also, trees, rocks and other objects create weaknesses in dry avalanches too. They create facets, weaknesses in the slab, thinner slabs, etc.

Edit - I was wrong about the 32 degrees. The steepest part measured was 37 degrees, and the bed surface below the crown was 34 degrees.

only 32 on the slope that failed? mid-upper 30's for sure on that face. with all of the wind up high day to day, that slope and others around the cone get tamped down into mostly stable.

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Originally Posted by thewon

i suppose it's possible, but in this case i really think coincidence. reason being is that there was no daytime heating issues at the time of the slide. trees and rocks tend to create weaknesses to point of failure when things are heating up and snow melts causing bonds to breakdown and water percolates down from those features to cause further weakening of the new snow/bed surface interface. sound reasonable? the slope failed a fair bit lookers right, like middle right of the crown line pictured, then shot across both left and right from there. i skied down from the mid crown area of the ridge and pulled the "winning" card from that brittle house of cards quite a ways down from the crown. i'll never that feeling of great snow feeling so very bad.

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Makes sense, and thanks for the detailed analysis.

received some info regarding the summit cone avy tonight via email.

"A friend pointed me to the TGR thread about ESAW. Just for clarification…the steepest part of the summit cone avy bed surface and slab above I measured was 37 degrees, just below and south of the apex of the crown. On the whole, the bed below the crown measured around 34 degree. That’s the number Frank referenced at ESAW. My pit down and north of the apex (~5700, 34 degrees) was dug to 1.9 meters deep, then my probe sank another 2.1m before hitting bottom. Given the underlying surfaces, I would not expect a uniform 400cm snowpack. In fact, my money is on the triggering party, being the ones hiking through the rocks on lookers left, probably punching through the slab into the rock garden less than a meter below the surface. That’s just my speculation though, after going there on Tuesday."

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Originally Posted by Jonathan S.

Makes sense, and thanks for the detailed analysis.

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you're most welcome. you may be spot on about those small trees that you thought may have contributed to the slope failure in my incident.

same email:

"Rog-rocks and trees do create weaknesses, and heating issues/percolation can contribute to natural releases (or human triggering being easier), but that’s not to say they can’t also contribute to unstable cold slabs. Looking at that picture, and how the crown runs toward the trees then jogs down through them, it looks to me like there was a minefield of weak points in those trees. The collapsing weak layer likely arrested in those trees. Imagine if they weren’t there and it was just grassy underneath. One, you might not have had an avalanche. Two, if you did, it probably would have kept propagating farther than it did."

^ Good stuff, thanks.
(I especially like the GoS analysis along the lines of on-the-one-hand/on-the-other-hand, which in this context is kind of damned-if-you-do/damned-if-you-don't. Tremper has lots of that in his book, which underscores so much of the inherent uncertainty in all this.)

Getting back to the specifics of all this, I had a three-page essay from an avy student this fall who had been in one of the two parties that was on the edge of it.
Shortly beforehand, the scene up there was even crazier:
"At the top of lobster claw (approximately 12:30 p.m.), we observed significant activity on the SE slope of the summit cone. What appeared to be a family on sleds, several skiers, a man on a kite board, and a man who appeared to be digging a snow pit in the exact center of the slope (confirmed with binoculars)."
Made for quite the interesting class discussion!

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Originally Posted by Jonathan S.

^ Good stuff, thanks.
(I especially like the GoS analysis along the lines of on-the-one-hand/on-the-other-hand, which in this context is kind of damned-if-you-do/damned-if-you-don't. Tremper has lots of that in his book, which underscores so much of the inherent uncertainty in all this.)

Getting back to the specifics of all this, I had a three-page essay from an avy student this fall who had been in one of the two parties that was on the edge of it.
Shortly beforehand, the scene up there was even crazier:
"At the top of lobster claw (approximately 12:30 p.m.), we observed significant activity on the SE slope of the summit cone. What appeared to be a family on sleds, several skiers, a man on a kite board, and a man who appeared to be digging a snow pit in the exact center of the slope (confirmed with binoculars)."
Made for quite the interesting class discussion!

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musta been quite the scene!:eek:

For anyone who might be subscribed via email to this old thread yet spending your August more productively than checking TGR constantly, here is a link to the preliminary info I just posted now for ESAW 2015:
http://www.tetongravity.com/forums/s...*-Nov-6-8-2015