Colchuck avalanche

From the comments from the poster of the Instagram video:
"A rock fall the size of a pickup truck is what caused the slide. The snow was not wet, it was firm."

Here is my hypothesis.

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. 

Mike, Great theory; which is very likely the scenario that happened. Nice "engineering" sketches. It makes total sense to me and hope that is what happened and not a new normal because, if it was a rock induced event, it would be a rarer occurrence. Like others have said, the videos posted also put a "shiver" in my groin and your theory may let me breath a little easier. Will you please stamp the sketches.

Will you please stamp the sketches. 

I'll stamp them "the rock-mole hypothesis"
I plan to go look at it later this week. I'll report back what we find.

In the video, it looks a lot like I'd imagine a lahar to be. Rock gets mixed up with snow and ice chunks, which flow downhill in a slurry. It's impressive the amount of material moving down the Colchuck.

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.

Mike, add free flowing water into the mix...