Terrain
Cornice
A wind-formed overhang of snow that builds up on the lee side of ridges and can collapse without warning.
Cornices form when prevailing winds blow snow over a ridgeline and deposit it on the sheltered side. They can grow several metres past the underlying rock, cantilevered over the drop below.
Standing on one, or dropping onto a slope below one, is a serious hazard - cornice collapses are a common trigger for slab avalanches on the slope below.