Avalanche: Turnagain

I skied onto a rocky rib below my partners to photograph. The snow on this rib was noticeably different than everywhere else. Our trailbreaker had started to step onto this pocket while skinning up, felt the change, noted it to the group, and changed direction to avoid the pocket.
I hit several rocks while side slipping down the rib. There was a breakable crust just below new snow, and I was punching into the basal facets below that crust to the ground. This may have been the Thanksgiving or Christmas crust exposed by wind with only this week's snow on top of it -> The thinnest of snowpacks possible over a known layer of concern.

I photographed my group skiing in the deep snow one gully over from my position.
When they were in a safe position below I skied off the rib away from their line. At first I thought the snow moving around me was just the expected sluff, but I saw a propagation crack go out to my left. I skied off the flow and waited for it to clear. I was surprised to see it run all the way to alder line, at least 800' vert. The crown was 6-12" deep.

My group couldn't see me and were concerned by the powder cloud and debris flow they saw. We checked in via radio (radios help so much!) and I skied down to them. After some discussion we decided to keep skiing. We did 3 more laps without incident.