Climbing a short 33-34 degree, NE-facing slope at 10,800' towards the Heart of Darkness (just north of Monte Cristo). I felt a significant collapse accompanied by a whumph. My partner and I, who had been spread out ~50' to manage the potential for loose avalanches or small storm slabs, increased our spacing and quickly moved to a safe zone. Following my booter, my partner also felt a second collapse under him. In our safe zone we dug a pit, and observed a sudden planar fracture while isolating out CT block. It failed 18" down on 1-2mm facets on top of a sun crust from out dry spell before this most recent storm cycle. Collapsing, failure on isolation, 5 lemons... Yikes! We bailed from our objective and decided to spend the rest of our tour weak layer-sleuthing. This facet layer was not present anywhere else that we dug (NW and E facing slopes at 10,600 on either side of Cardiac Pass, and an E facing slope at 10,500 at the north end of Cardiac Bowl). It seems to be a very isolated problem. However, I would speculate that some of the bigger avalanches triggered yesterday failed on that layer. Our take: there is a chance a person could trigger a persistent slab avalanche in isolated areas where this structure exists. These isolated areas may also be prone to producing wet slabs with additional warming the next couple days.
