Large collapses in S. Gallatin

From an email: " While skinning...we felt many large collapses in shallow, wind-affected snow. On the ridge crest, we found a ~3cm crust on the surface with massive (~6mm+), striated facets underneath. After skiing down an east-facing, 400', low angle slope, we felt a large collapse that traveled at least 60 feet, but continued rumbling for several seconds and may have propagated back up the slope that we skied. The collapse was triggered in shallow snow in the flats. This weak snow structure near the surface was not present in the next drainage east."