Will Thomas

Salt Lake » Big Cottonwood Canyon » Mill B South » Monte Cristo

Upper Mill B South (Backside of Heart of Darkness)

10,800'

Northeast

38°

Skier

Intentionally Triggered

Soft Slab

Wind Drifted Snow

New Snow

6"

450'

400'

1

My partner and I were descending from Monte Cristo to ski Heart of Darkness this morning. Just above the entrance, I made a ski cut which triggered a shallow wind slab on the backside. The slab, which had been sloughing slightly below my feet on a slow, low pressure traverse, unexpectedly broke two feet above me as I gained speed and propagated about 40 ft between 2 and 6 inches deep. I was able to immediately self-arrest with a whippet, but the slide (while staying shallow) carried over a midslope cliff and propagated far wider in the lower bowl from the force of the drop. Because we were separated by 100 feet of similarly exposed terrain which hadn't slid, neither of us felt comfortable traversing to meet on top. After confirming our plan by radio, I descended the bed surface (which was still quite slabby) mostly side stepping above the cliffs until I could cut out towards lower consequence terrain. I then spotted my partner as he descended an adjacent lower angled bowl which did not slide. Once reunited, we debriefed and skied out to the S Turns.

Take Aways: 1) Manageable slabs are not manageable in extreme terrain. Use a rope or turn around even if you think it will probably be fine. I knew it was a high-consequence situation but thought I could manage my way alone through the red flags. The slides I have intentionally triggered have always broken near my feet, so I assumed that with so little snow above me that would be the case this time as well. 2) Risk/Communication drift while in exploring mode: My partner and I did not research the beta well enough to know that HOD was the second chute down the ridge. When we came to the first chute, we were confused by the lack of anchors. Becuase I was faster and in charge of setting the rappel, I moved ahead focusing on problem-solving and finding our entrance rather than communicating deeply about our new uncertainty. Because I assumed I could manage the slab risk on the traverse and the ski map indicated that our chute was close, I moved out to scout even though my partner was still transitioning from a downclimb. Although I communicated my plan, I was moving too fast for the situation and if I had taken a ride this lack of preparation could have been deadly. Ultimately, I was still in an uphill mountaineering mindset even though we had started to descend avalanche terrain: "How can I make this work" vs. "how to we mitigate what might go wrong." In the future, I plan to consciously slow down and do a group risk assessment whenever something unexpected happens. This incident was an exceptionally cheap lesson.