7 O'Clock Mtn

had taversed ridgeline of 7oclock mtn with snow mobile to park and ski North face, but as soon as I reached the summit and was coming to a stop I noticed cornice fracture 10m in front of where I was parking sled. Fracture line seemed to propagate down from summit in both directions. Pressure from weight of myself and sled remotely triggered. Immediately backed away from the edge and instructed other members of group to stop. We backtracked down to the runout zone and witnessed the aftermath of what was aprox sz 3-3.5 avalanche triggered by cornice drop. The North face of mountain had slid to rock so an entire season snowpack let loos. I'm guess at least 3-4m deep, and probably deeper in concave lee side deposit right below cornice. Large truck size chunks of cornice debris travelled the full distance of slide path. We looked for signs of invovlement from below and felt confident there was none, so left the area.