Quick report
- Cracking
- isolated
I caused and observed a cornice break and subsequent avalanche on earthquake dome.
Avalanche
Early this morning I unintentionally triggered a cornice fall and subsequent avalanche on earthquake dome. Nobody was caught. The volume of the cornice break was at least 8 ft x 6 ft x 50 ft (H x W x L). My partners and I observed the break and fall. The cornice was the largest I have seen on earthquake dome in the last few years. The cornice was developed atop a steep NE-facing, slightly bowl-shaped slope at approximately 9330 elev. The cornice broke as I was skinning about six feet off the edge of the cornice. The cornice broke with a loud crack/boom and I was able to skin away from the fracture line. The cornice block tilted downhill and crashed onto trees and the underlying slope. Several blocks near the fracture were hung up on trees; others smashed onto the slope, broke into bits, and scoured and entrained material from the slope. The debris funneled downhill within an approximately 25ft wide gully feature. I estimate the avalanche translated at least 80 vertical feet downhill -- beyond which I could not see. I estimate D2 avalanche. I was surprised by the cornice fall. We had observed no indications of instability, and the drifts and cornices I had been interacting with seemed stout and robust. I was unable to get anything to move until the cornice fell. I made a mistake. And am embarrassed by my mistake. I overestimated the strength of the cornice and thought I had sufficient setback from the edge. It failed under my outside ski. I was fortunate that I was able to move off. Because going with that cornice and entrained debris would have been decisively bad. Red Flags New Snow BIG winds Obviously over-sized cornice