Couloir

A couloir (a French word meaning "passage" or "corridor"), is a narrow gully with a steep gradient in a mountainous terrain.

A couloir may be a seam, scar, or fissure, or vertical crevasse in an otherwise solid mountain mass. Though often hemmed-in by sheer cliff walls, couloirs may also be less well-defined, often simply being a line of broken talus or scree 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, becoming much more noticeable than in warmer months when the majority of the snow and ice may recede. These physical features make the use of couloirs popular for both skiing and mountaineering.