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Colchuck avalanche
- mikerolfs
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www.facebook.com/banzaimf/videos/10154393776449181/
colchuck avalanche
It's a video of an avalanche taken by someone at Lake Colchuck looking up at the glacier. It was probably raining. I was north in Spider Meadows and there was a soaking rain that grew and decreased in intensity. Probably similar at Coluchuck.
Makes me shiver. I generally operate under the assumption that summer snow is safe. Clearly that isn't true.
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- mikerolfs
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- T. Eastman
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Lots of water to lube up the systems.
Stay smart!
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- glowbug
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- mikerolfs
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and here is a video from the climbers as the avalanche approached them. Would you have time to get out of the way? I don't know.
www.facebook.com/shane.flynn.3323/videos/533711566826926/
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- Charlie Hagedorn
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- jaronheard
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"A rock fall the size of a pickup truck is what caused the slide. The snow was not wet, it was firm."
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- mikerolfs
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1. Rock falls from above (off Colchuck) and pierces snowpack
2. Snow at bed surface is rotted and provides inadequate resistance to stop the rock. Rock slides below the snow surface down glacial ice and then down the polished granite slope like a wedge or chisel. Rock goes fast and plows beneath competent surface snow, pulverizing it. Pulverized snow falls back to bed surface (behind rock) and slowly starts to slide down the slope inside the channel
3. Rock stops. Pulverized snow in channel slides downhill, hits rock, jumps out of channel and fans out.
If this was the mechanism, I'd bet that almost no surface snow below the channel was entrained, and that the entire debris pile consists of the snow from the channel. Also, I expect to find the big rock wedged in the snow pack at the end of the clean channel.
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- ddavis
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- mikerolfs
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I'll stamp them "the rock-mole hypothesis"Will you please stamp the sketches.
I plan to go look at it later this week. I'll report back what we find.
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- kamtron
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Have you guys seen the pictures of the Boulder glacier debris flow that occured this year on Baker/Sherman peak? That one also ran an impressive distance. I went and camped on Boulder ridge a couple weeks back and saw debris from that event below the toe of the glacier, near where the trail reaches the fixed rope up onto Boulder ridge. And the starting point for that flow was the top of Sherman peak.
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- T. Eastman
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- Charlie Hagedorn
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- Norseman
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This event was after/during a rain saturation period, right? Full-pack wet-slab-on-rock release somewhere high up?
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- MattT
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GLOFs: en.wikipedia.org/wiki/Glacial_lake_outburst_flood
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- jtack
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He is require to submit a new "stamped" drawing to explained the new discovery.
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- T. Eastman
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- mikerolfs
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I was way off. Here is we found:Mikes mole rock theory has been debunked!
The trigger was a huge rock fall from the shoulder of Colchuck.
colchuck col is at the left on the skyline. The green line is what I believe to be the event boundary. It's possible that the gap in the skyline did not exist before this event. I wonder if someone has a photo for comparison?
All the snow slid off the glacier on the steep pitch near the top. The bed surface is glacier ice. On the left side in this photo, the snow depth at the skyline was just more than a ski pole, and near the bottom of the slope the sidewall was just over 300cm deep. There was a weak layer between 155cm and 195cm from the surface where my probe met very little resistance. I don't think the weak layer played any part in this event. The snow depth tapered on the right, at one point to zero where glacier ice is exposed at the surface (right of center in the photo)
The debris pile was truly impressive. It filled a large portion of the flat above the terminal moraine. 15 feet (estimated) deep at the lowest edge.
I re-watched the videos. The woman from the lake mentioned hearing something and then a few minutes later seeing the avalanche. Her video shows white snow. The climbers videos both show white snow, especially the debris flow into the moraine basin which was snow chunks with an occasional large rock. What Jamie and I found in the debris pile was a mix of rock and snow with sand over the top.
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- ddavis
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- Charlie Hagedorn
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