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gauge

in meteorology, general term for any device that measures strength of wind, pressure, and other parameters; the most widespread gauges on meteorology are balance snow gauge, barometer gauge, density-of-snow gauge, dew gauge, distance gauge, rain-and snow gauge, rain-intensity gauge, standard gauge, wind gauge, etc..

gelifluction

the slow downslope flow of unfrozen earth materials on a frozen substrate.

general circulation

of the atmosphere; complete statistical description of atmospheric motions over the earth.

general circulation model

numerical representation of the atmosphere and its phenomena over the entire earth, using the equations of motion and including radiation, photochemistry, and the transfer of heat, water vapor, and momentum.

geocryology

the study of earth materials having a temperature below 0 degrees Celsius.

geomagnetic pole

the point of intersection of the Earth's surface with the axis of a simple magnetic dipole that best approximates the Earth's actual, more complex magnetic field; if the Earth's magnetic field were a perfect dipole then the field lines would be vertical at the geomagnetic poles, and they would therefore coincide with the magnetic poles: however, the dipole approximation is in fact far from perfect, so in reality the magnetic and geomagnetic poles lie some distance apart.

geostrophic wind

theoretical wind which results from the equilibrium between horizontal components of the pressure gradient force and the coriolis force (deviating force) above the friction layer; only these two forces (no frictional force) are supposed to act on the moving air; it blows parallel to straight isobars or contours.

the rate of temperature increase with depth in the subsurface.

geothermal heat flux

the amount of heat moving steadily outward from the interior of the earth through a unit area in unit time.

geyser

fountain that develops when water from a conduit is forced up to the surface of a glacier; also called a negative mill.
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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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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, Natural Resources Canada. Copyright Terrain Sciences Division, Geological Survey of Canada.)
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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 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 Photograph Database.)
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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 till

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

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

a phenomenon in which strong reflection of the sun on an icy surface causes a glacier to look like it is on fire.
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glacier flood

a sudden outburst of water released by a glacier.
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glacier flour

a fine powder of silt- and clay-sized particles that a glacier creates as its rock-laden ice scrapes over bedrock; usually flushed out in meltwater streams and causes water to look powdery gray; lakes and oceans that fill with glacier flour may develop a banded appearance; also called rock flour.
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glacier ice

well-bonded ice crystals compacted from snow with a bulk density greater than 860 kilograms per cubic-meter (55 pounds per cubic-foot).
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glacier mill

a nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses.
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glacier pothole

potholes formed at the bottom of glaciers through erosion caused by sand and gravel in melt-water; melt-water seeps through crevasses in the glaciers, sometimes forming whirpools; at the bottom of the glacier, the water is under very high pressure, leading to erosion of underlying rocks.
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glacier remainie

a glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier, then re-adhering; also called reconstituted, reconstructed or regenerated glacier.
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glacier snout

the lowest end of a glacier; also called glacier terminus or toe.
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glacier sole

the bottom of the ice of a glacier.
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glacier table

a rock that resides on a pedestal of ice; formed by differential ablation between the rock-covered ice and surrounding bare ice.
Talefre Glacier on Mont Blanc Massif in the European Alps sported a prominent glacier table when this undated photograph was taken. The rock protected the ice directly below it from melting, resulting in the characteristic pedestal that remains after the surrounding ice melts. For scale, note the man standing behind and to the left of the pedestal. (Photo courtesy of Cairrar, archived at the World Data Center for Glaciology, Boulder, CO.)
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glacier terminus

the lowest end of a glacier; also called glacier snout or toe.
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glacier toe

the lowest end of a glacier; also called glacier snout or terminus.
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glacier tongue

an extension of a glacier or ice stream projecting seaward, usually afloat.

glacier trough

u-shaped valleys transformed from v-shaped stream valleys due to erosion caused by passing glaciers.
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glacier wind

a localized current of air occuring as a result of a glacier's melting processes; when the surface of glacial ice melts, the air above the glacier cools and becomes heavier than the surrounding air and flows down the glacial valley; glacier wind can also be wind that flows out of ice caves; a kind of katabatic wind.

glacieret

a very small glacier.
Arapaho Glacier, located along the Front Range, Colorado, in 1956. Although relatively small in terms of glacier size, the city of Boulder, Colorado, still receives some of its drinking water from Arapaho Glacier runoff. (Photo courtesy of the World Data Center for Glaciology, Boulder, CO.)
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