A couloir (, "passage" or "corridor") is a narrow gully 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 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 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 and
extreme skiing.
