glaciers

glacier cave

a cave of ice, usually underneath a glacier and formed by meltwater; cave entrances are often enlarged near a glacier terminus by warm winds; most common on stagnant portions of glaciers.
A small stream flows from the glacier cave at the terminus of Arolla Glacier in the Pennine Alps. Photograph from 1902. (Photo courtesy of H.F. Reid, archived at the World Data Center for Glaciology, Boulder, CO.)
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glacier

a mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer; many believe that a glacier must show some type of movement; others believe that a glacier can show evidence of past or present movement.
Taku Glacier winds through the mountains of southeastern Alaska, calving small icebergs into Taku Inlet. This photograph dates from 1929. (Photo courtesy of the U. S. Navy, archived at the World Data Center for Glaciology, Boulder, CO.)
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glaciated

land covered in the past by any form of glacier is said to be glaciated.
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glacial trough

a large u-shaped valley formed from a v-shaped valley by glacial erosion.
Western Brook glacial trough, Newfoundland, Canada. The sheer walls of this glacial trough soar up to 700 m high, and the glacial basin is 500 m deep in places. (Photo courtesy of Natural Resources Canada. Copyright Terrain Sciences Division, Geological Survey of Canada.)
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glacial till

accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders; the usual composition of a moraine.
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glacial striations

grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial grooves.
Striated Graywackie, Yale Glacier, Alaska. 1997. Parallel striations and bedrock fracture trends (across the left side of the image) are clearly visible in this photo. (Photo courtesy of Tom Lowell, University of Cincinnati.)
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glacial retreat

when the position of a mountain glacier's terminus is farther upvalley than before; occurs when a glacier ablates more material at its terminus than it transports into that region.
Muir Glacier, Glacier Bay National Park and Reserve's White Thunder Ridge as seen on August 13, 1941 (left) and August 31, 2004 (right). (2004 photo courtesy of B. Molnia, USGS; 1941 photo courtesy of W. Field. Archived in the Long-Term Change Photograph Pairs Special Collection in the Glacier...
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glacial grooves

grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial striations.
Striated Graywackie, Yale Glacier, Alaska. 1997. Parallel striations and bedrock fracture trends (across the left side of the image) are clearly visible in this photo. (Photo courtesy of Tom Lowell, University of Cincinnati.)
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glacial erratic

a boulder swept from its place of origin by glacier advance or retreat and deposited elsewhere as the glacier melted; after glacial melt, the boulder might be stranded in a field or forest where no other rocks of its type or size exist.
Erratic boulder, northeastern Manitoba, Canada. A sense of the size of the glacial erratic can be estimated by noting the person standing in front of the boulder, on the left side. This erratic, as well as neighboring ones, were carried by the Keewatian Ice Sheet. (Photo courtesy of Lynda Dredge,...
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glacial advance

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