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

gully A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces. Gullies resemble lar ...

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 that can be a few inches across to over 40 feet. Crevasses form as a result of the movement and resulting stress associated with the shear stress generated when two semi-rigid pie ...

in an otherwise solid mountain mass. Though often hemmed in by sheer cliff walls, couloirs may also be less well-defined, and often simply 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. Talus deposits typically ha ...

ascending the mountainside and bordered by trees 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 or alpinism, is a set of outdoor activities that involves ascending tall mountains. Mountaineering-related activities include traditional outdoor climbing, skiing, and traversing via ferratas. Indoor climbing, sport climbing, a ...

and

extreme skiing Extreme skiing is 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 include Swiss skier ...

References

{{reflist Landforms Mountains Montane ecology