Came accross a pretty big natural avalanche in West Porter Fork. Looked like it started as a storm slab triggered by a cornice falling along the upper headwall. At about 9,300ft in elevation the slide stepped down to the facets at the ground. I couldn't see the entire crown line, but it looked to be at least 500ft wide and ran about 600-700ft vertical. One of the debris piles was easily 10+ feet deep. I included an image of the topo map with a blue line showing the crown.