(1) head of glacier; (2) firn or névé; (3) region of ground moraine deposition; (4) terminal moraine; (5) drumlin; (6) braided stream; (7) kettle; (8) medial moraine; (9) lateral moraine; (10) U-shaped valley; (11) arête; (12) hanging valley; (13) cirque; (14) tarn; and (15) ice fall.
Bering Glacier, Alaska. Credit: NASA.
A glacier is a large mass of ice that can survive for many years. In most cases, glaciers are heavy enough to flow downhill under their own weight. They are significant agents of erosion. Three main types of glacier are recognized: ice sheets and caps, mountain or valley glaciers, and piedmont glaciers.
Glaciers form wherever conditions are such that annual precipitation of snow, sleet, and hail is greater than the amount that can be lost through evaporation or otherwise. The occurrence of a glacier thus depends on the latitude and also on local topography: there are several glaciers on the equator.
Glaciers account for about 75% of the world's fresh water, and of this the Antarctic ice sheet accounts for about 85%.
Mountain glaciers usually result from snow accumulated in cirques coalescing to form glaciers; and piedmont glaciers occur when such a glacier spreads out of its valley into a contiguous lowland area.
Features associated with glaciers and glaciated landforms
For more information on glaciers and the features associated with them, see: