Checking out YouTube videos of landslides I came across this slide on Johannesburg Mountain. Not a spectacular slide, but likely fatal if you were on the avalanche deposits at the base of the slide. This site is in the North Cascades at the end of the South Cascade River Road. It is also in my thesis area. Ned Brown and I traversed the cone of ice where the slide in the video ended. A few small rocks flew past us while we were there. We did not spend a lot of time in the middle of the ice pile at the base of the slope. Fast walking with a constant eye looking up the slope and helmets on.
The bedrock consists of highly metamorphosed Cascade River Schist. The rocks at the base of Johannesburg got an added cooking from the intrusion of the Cascade Pass Dike approximately 15 million years ago. This later cooking obscured what I was really looking for - a metamorphic signature of the deep burial of the area. That find came a year later and a few miles to the north.