Sherwins above Mammoth Rock 300ft below ridge
Monday, March 5, 2018 - 3:30pm
This avalanche was triggered remotely while skiing nearby ridge during a major whoomph yesterday (4/5). Accross slope for ~200ft wide cracks opened up, and this small 25'x25" pocket released which was sourounded by rocks and had a convex roll out of the pocket. (see attached photo). Crown varied from 1.5-3ft deep.
Went back today to investigate further, see attached crown profile. 220cm deep snowpack. One upper crack opened up from the surface down 90cm deep (220cm-130cm), and then another deeper crack opened open from 123cm-65cm. The bottom of this deep crack failed to the top of a facet layer just below a 2cm thick ice crust. Multiple ECT, Deep Tap tests, and a modified deep tap extended column tests were done to test the deep facets layer, and all tests failed and propagated in the upper part of the uppermost facet layer (surface facets in old snow previous to major storm end of last week).
Appears that new fractures across a slope occured today low down in the main avalanche path.