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Cornice (climbing)
Encyclopedia
Snow
Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
on a ridge or the crest of a mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
. They form by wind blowing snow over the crest of the mountain, so they often form on the leeward sides of mountains. Cornices are extremely dangerous and travelling above or below them should be avoided.
When a cornice collapses, it breaks in from the cornice to the top of the peak; even being on the snow on top of rock exposes the alpinist to hazard in this situation. The best practice in mountaineering
Mountaineering
Mountaineering or mountain climbing is the sport, hobby or profession of hiking, skiing, and climbing mountains. While mountaineering began as attempts to reach the highest point of unclimbed mountains it has branched into specialisations that address different aspects of the mountain and consists...
is to stay far enough back from the edge so as not to be able to see the drop, as an approximate metric of exposure. Of course, this is not always possible. A good test for safety (in sunny weather) is to insert an ice axe
Ice axe
An ice axe, is a multi-purpose ice and snow tool used by mountaineers both in the ascent and descent of routes which involve frozen conditions. It can be held and employed in a number of different ways, depending on the terrain encountered...
and see if a blue glow comes out of the hole. This indicates the ice is being lit from underneath, and that the climber should retreat to a safer location.
In avalanche
Avalanche
An avalanche is a sudden rapid flow of snow down a slope, occurring when either natural triggers or human activity causes a critical escalating transition from the slow equilibrium evolution of the snow pack. Typically occurring in mountainous terrain, an avalanche can mix air and water with the...
safety, cornices are a high avalanche danger as they often break and trigger larger avalanches that permeate several snow layers. Cornices are particularly vulnerable to collapse during periods of solar warming.