A couloir (, "passage" or "corridor") is a narrow

gully A gully is a landform A landform is a land feature on the solid surface of the Earth or other planetary body. They may be natural or may be anthropogenic (caused or influenced by human activity). Landforms together make up a given ter ...

with a steep gradient in a mountainous terrain.Whittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, p. 121. .

Geology

A couloir may be a seam, scar, or fissure, or vertical

crevasse A crevasse is a deep crack that forms in a glacier or ice sheet. Crevasses form as a result of the movement and resulting stress associated with the shear stress generated when two semi-rigid pieces above a plastic substrate have different rate ...

in an otherwise solid mountain mass. Though often hemmed in by sheer cliff walls, couloirs may also be less well-defined, and may often simply be a line of broken talus or

scree Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. The term ''scree'' is ap ...

ascending the mountainside and bordered by trees, rocks or other natural features. Couloirs are especially significant in winter months when they may be filled in with snow or ice, and become much more noticeable than in warmer months when most of the snow and ice may recede. These physical features make the use of couloirs popular for both

mountaineering Mountaineering, mountain climbing, or alpinism is a set of outdoor activities that involves ascending mountains. Mountaineering-related activities include traditional outdoor climbing, skiing, and traversing via ferratas that have become mounta ...

and

extreme skiing Extreme skiing is a form of skiing performed on long, steep (typically from 45 to 60+ degrees, or grades of 100 to 170 percent) slopes in mountainous terrain. The French coined the term 'Le Ski Extreme' in the 1970s. The first practitioners incl ...

References

{{reflist Landforms Mountains Montane ecology Geographical terminology in mountaineering