![](https://images.prismic.io/avalancheca/0177276b7e296c9319ede4e00b2cfe422550f54c_cornices---martina-halik---small.jpg?auto=compress,format)
![](https://images.prismic.io/avalancheca/89c460a6f687aba112152a125b5032a11bda63c2_cornice-diagram.jpg?auto=compress,format)
A cornice is an overhanging ledge or shelf of snow that usually forms over the lee side of ridges. A cornice forms as loose snow is transported over a ridge, where it collects and grows. Cornices have an unstable structure and they grow more unstable with loading or warming. When a cornice breaks, the resulting fall is usually powerful enough to trigger an avalanche.
Photos
Above: Cornices along a ridge. By Martina Halik
Below: It's important to stay far back from the edge as cornices can break surprisingly far in from the edge. By Avalanche Canada
See also: