Cornices

Cornices


Cornices are accumulations of unstable snow and are a danger to walkers


Cornices 

Cornices


Cornices are formed formed from snow, which is blown by the wind and deposited on steep leeward sides of mountain summits and ridges. (The leeward side is the one opposite from which the wind is blowing.)

After sustained build-up, the cornice will extend the area of the summit (or ridge) and it becomes impossible to determine where solid ground stops and the cornice begins, as it looks from the summit the surface is just snow. The overhanging part of the cornice is the most dangerous, but even snow over solid ground can be susceptible to collapse, by being dragged down by the weight of a falling overhang.

It's not uncommon to see cracks form on the summit, so keep wall away from them if seen.

Cornices will become unstable and at risk of collapse as the weather warms, or if walked upon.

The image above (click to expand) is the summit of Cairn Lochan in the Cairngorms. See how the edges of the escarpment are extended by the cornices, and how easy it would be for a walker, particularly in poor visibility, to walk on snow that is in fact a cornice and not solid ground.


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