Snow cornice

A snow cornice, often called simply a cornice, is an overhanging edge of snow on a ridge or on the crest of a mountain, and also along the sides of gullies. The word comes from the Italian cornice, meaning ledge. A cornice forms when wind blows snow over a sharp break in the terrain, such as the crest of a mountain, where the snow attaches and builds out horizontally. This build-up is most common on the steeper and leeward sides of mountains. Cornices are dangerous. When one collapses it breaks back from the cornice towards the top of the peak, so even standing on snow above rock can expose a climber to hazard, and the usual mountaineering practice is to stay far enough back from the edge not to see the drop. In avalanche safety, cornices matter because they often break and trigger larger avalanches, and they are especially prone to collapse during periods of strong sunlight.