sharp, narrow ridge formed as a result of glacial erosion from both sides.

alpine glacier

a glacier that is confined by surrounding mountain terrain; also called a mountain glacier.
Muddy River Glacier

Muddy River Glacier carves its way through forested mountains near Frederick Sound in southeast Alaska. Typical of mountain glaciers, it is constrained on all sides by mountainous terrain. (Photo courtesy of U. S. Navy. Archived at the World Data Center for Glaciology, Boulder, CO.)



(1) combined processes (such as sublimation, fusion or melting, evaporation) which remove snow or ice from the surface of a glacier or from a snow-field; also used to express the quantity lost by these processes (2) reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches.

alpine layers

annual accumulations of snow and dust on a glacier.


when a mountain glacier's terminus extends farther downvalley than before; glacial advance occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.

active rock glacier

a mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of present movement.

accumulation zone

area of a glacier where more mass is gained than lost.

accumulation season

period during which a glacier gains more mass than it loses; usually coincides with winter.

accumulation area

area of a glacier where more mass is gained than lost.


all processes by which snow or ice are added to a glacier, this is typically the accumulation of snow, which is slowly transformed into ice; other accumulation processes can include avalanches, wind-deposited snow, and the freezing of rain within the snow pack.


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