Shaft within a glacier or ice sheet which water enters from the surface
A hiker peers into a large moulin onSnowbird Glacier, in theTalkeetna Mountains of AlaskaSchematic drawing of glacial features illustrating how moulins transport surface water to the base of the glacierSurface water entering a moulin onAthabasca Glacier
Amoulin (orglacier mill) is a roughly circular, vertical (or nearly vertical) well-like shaft formed where a surface meltstream exploits a weakness in the ice. The term is derived from the French word for mill.[1][2]
They can be up to 10 meters wide and are typically found on ice sheets and flat areas of a glacier in a region of transverse crevasses. Moulins can reach the bottom of the glacier, hundreds of meters deep,[3][4][5] or may only reach the depth of common crevasse formation (about 10–40 m) where the stream flows englacially.[6] They are the most typical cause for the formation of aglacier cave.
Moulins are parts of the internal structure of glaciers, that carrymeltwater from the surface down to wherever it may go.[7] Water from a moulin often exits the glacier at base level, sometimes into the sea, and occasionally the lower end of a moulin may be exposed in the face of a glacier or at the edge of a stagnant block ofice.
Water from moulins may help lubricate the base of the glacier, affectingglacial motion. Given an appropriate relationship between an ice sheet and the terrain, the head of water in a moulin can provide the power and medium with which atunnel valley may be formed. The role of this water in lubricating the base of ice sheets and glaciers is complex and it is implicated inaccelerating the speed of glaciers and thus the rate ofglacial calving.[8]
^Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005)Glossary of Geology (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp.ISBN0-922152-76-4
