Large Cornices Along the Sierra Crest

We decided to go looking for evidence of other avalanches that may have been triggered by large cornice collapses along the Sierra Crest south of Mt. Lincoln. We chose this area because we could stay well away from the edge of any cornices and still get great views onto the slopes below them. As we skinned out the ridge, we spotted several old cornice collapses and old debris on the steep wind-loaded slopes below the ridge. We also saw a few old and mostly filled in avalanche crowns. We had hoped to be able to get into one of these areas to do a thorough investigation of one of these old crowns, but everywhere we looked we found larger cornices looming over the slopes with plenty of snow still available to release on the slopes. We did find some small wind-loaded test slopes and the small cornices above these were still easy to break. We chose not to hang out on any slopes below or go anywhere near the larger cornices. 

We found a spot on the ridge with a low angle slope that dropped into Cold Stream Canyon and no cornice at the entry point. We descended low angle slopes with ankle-deep soft snow. Since the start of the tour we had noticed surface hoar (even on along the Sierra Crest) and it got larger as we descended into more sheltered terrain. Around 7100 ft. We came across what looked like an old avalanche crown in some complicated terrain that had mostly filled back in. We dug a pit on a nearby low angle slope and found the facets buried 90 to 120 cm (3 to 4 ft) below the surface. The snowpit data we collected indicated that it would be very difficult to get enough force down to this layer to break it, but if the layer does break the resulting fracture could still propagate along the layer. 

We skinned back to Roller Pass paralleling the Sierra Crest and were able to look up at the steep wind-loaded slopes. We saw more evidence of old avalanches and cornice collapses, but we still did not find any that we could safely access to investigate in more detail.  

Photo 1: Very large cornice hanging over a steep slope.

Photo 2: 1 to 2 cm large surface hoar grains.

Photo 3: Old cornice and avalanche debris.

Photo 4: What looked like an old avalanche crown on a steep low elevation slope.