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Glossary
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Below you will find key words and concepts that you should remember from this chapter.
ablation (wastage)  The loss of the glacial ice or snow by melting, evaporation, or breaking off into icebergs. (Also called wastage).
(See page(s) 479)
advancing glacier  Glacier with a positive budget, so that accumulation results in the lower edges being pushed outward and downward.
(See page(s) 480)
alpine glaciation  Glaciation of a mountainous area.
(See page(s) 476)
arête  A sharp ridge that separates adjacent glacially carved valleys.
(See page(s) 489)
basal sliding  Movement in which the entire glacier slides along as a single body on its base over the underlying rock.
(See page(s) 480)
cirque  A steep-sided, amphitheater-like hollow carved into a mountain at the head of a glacial valley.
(See page(s) 488)
continental glaciation  The covering of a large region of a continent by a sheet of glacial ice.
(See page(s) 476)
crevasse  Open fissure in a glacier.
(See page(s) 483)
drumlin  A long, streamlined hill made of till.
(See page(s) 493)
end moraine  A ridge of till piled up along the front edge of a glacier.
(See page(s) 491)
equilibrium line  An irregular line marking the highest level to which the winter snow cover on a glacier is lost during a melt season. (Also called snow line.)
(See page(s) 480)
erratic  An ice-transported boulder that does not derive from bedrock near its present site.
(See page(s) 490)
esker  A long, sinuous ridge of sediment deposited by glacial meltwater.
(See page(s) 494)
fiord  A coastal inlet that is a glacially carved valley, the base of which is submerged.
(See page(s) 499)
glacier  A large, long-lasting mass of ice, formed on land by the compaction and recrystallization of snow, which moves because of its own weight.
(See page(s) 476)
ground moraine  A blanket of till deposited by a glacier or released as glacier ice melted.
(See page(s) 493)
hanging valley  A smaller valley that terminates abruptly high above a main valley.
(See page(s) 487)
horn  A sharp peak formed where cirques cut back into a mountain on several sides.
(See page(s) 489)
iceberg  Block of glacier-derived ice floating in water.
(See page(s) 479)
ice cap  A glacier covering a relatively small area of land but not restricted to a valley.
(See page(s) 478)
ice sheet  A glacier covering a large area (more than 50,000 square kilometers) of land.
(See page(s) 478)
kettle  A depression caused by the melting of a stagnant block of ice that was surrounded by sediment.
(See page(s) 494)
lateral moraine  A low ridgelike pile of till along the side of a glacier.
(See page(s) 491)
medial moraine  A single long ridge of till on a glacier, formed by adjacent lateral moraines joining and being carried downglacier.
(See page(s) 491)
moraine  A body of till either being carried on a glacier or left behind after a glacier has receded.
(See page(s) 491)
outwash  Material deposited by debris-laden meltwater from a glacier.
(See page(s) 493)
plastic flow  Movement within a glacier in which the ice is not fractured.
(See page(s) 483)
pluvial lake  A lake formed during an earlier time of abundant rainfall.
(See page(s) 498)
receding glacier  A glacier with a negative budget, which causes the glacier to grow smaller as its edges melt back.
(See page(s) 480)
rigid zone  Upper part of a glacier in which there is no plastic flow.
(See page(s) 483)
rock-basin lake  A lake occupying a depression caused by glacial erosion of bedrock.
(See page(s) 487)
rock flour  A powder of fine fragments of rock produced by glacial abrasion.
(See page(s) 486)
tarns  See rock-basin lake.
(See page(s) 487)
terminus  The lower edge of a glacier.
(See page(s) 480)
theory of glacial ages  At times in the past, colder climates prevailed during which significantly more of the land surface of Earth was glaciated than at present.
(See page(s) 476)
till  Unsorted and unlayered rock debris carried by a glacier.
(See page(s) 490)
tillite  Lithified till.
(See page(s) 499)
truncated spur  Triangular facet where the lower end of a ridge has been eroded by glacial ice.
(See page(s) 487)
U-shaped valley  Characteristic cross-profile of a valley carved by glacial erosion.
(See page(s) 486)
valley glacier  A glacier confined to a valley. The ice flows from a higher to a lower elevation.
(See page(s) 477)
varve  Two thin layers of sediment, one dark and the other light in color, representing one year’s deposition in a lake.
(See page(s) 494)
zone of ablation  That portion of a glacier in which ice is lost.
(See page(s) 480)
zone of accumulation  That portion of a glacier with a perennial snow cover.
(See page(s) 480)







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