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Glaciers
Chapter 18 of book EARTH: An Introduction to Physical Geology 9th Edition.
56
Geology
Undergraduate 1
04/28/2010

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Term
ablation
Definition
a general term for the loss of ice and snow from a glacier.
Term
abrasion
Definition
the grinding and scraping of a rock surface by the friction and impact of rock particles carried by water, wind, and ice.
Term
alpine glacier
Definition
a glacier confined to a mountain valley, which in most instances had previously been a stream valley.
Term
arete
Definition
a narrow knifelike ridge separating two adjacent glaciated valleys.
Term
basal slip
Definition
a mechanizm of glacial movement in which the ice mass slides over the surface below.
Term
calving
Definition
wastage of a glacier that occurs when large pieces of ice break into the water.
Term
cirque
Definition
an ampitheater shaped basin at the head of a glaciated valley produced by frost wedging and plucking.
Term
col
Definition
a pass between mountain valleys where the headwalls of two cirques intersect.
Term
crevasse
Definition
a deep crack in the brittle surface of a glacier.
Term
drumlin
Definition
a streamlined symmetrical hill composed of glacial till.

the steep side of the hill faces the direction from which the ice advanced.
Term
end moraine
Definition
a ridge of till marking a former position of the front of a glacier.
Term
esker
Definition
sinous ridge composed largely of sand and gravel deposisted by a stream flowing in a tunnel beneath a glacier near its terminus.
Term
fiord
Definition
a steep sided inlet of the sea formed when a glacial trough was partially submerged.
Term
firn
Definition
granular recrystallized snow.

a transitional stage between snow and glacial ice.
Term
glacial budget
Definition
the balance, or lack of balance, between ice formation at the upper end of a glacier, and ice loss in the zone of wastage.
Term
glacial drift
Definition
an all embracing term for sediments of glacial origin, no matter how, where, or in what shape they were deposited.
Term
glacial erratic
Definition
an ice transported boulder that was not derived from the bedrock near its present site.
Term
glacial striations
Definition
scratches and grooves on bedrock caused by glacial abrasion
Term
glacial trough
Definition
a mountain valley that has been widened, deepened, and straightened by a glacier
Term
glacier
Definition
thick mass of ice originating on land from the compaction and recrystallization of snow that shows evidence of past or present flow.
Term
ground moraine
Definition
an undulating layer of till deposited as the ice front retreats
Term
hanging valley
Definition
a tributary valley that enters a glacial trough at a considerable height above the floor of the trough
Term
horn
Definition
pyramid like peak formed by glacial action in three or more cirques surround a mountain summit.
Term
ice cap
Definition
mass of glacial ice covering a high upland or plateau and spreading out radially.
Term
ice-contact deposit
Definition
an accumulation of stratified drift deposited in contact with supporting mass of ice.
Term
ice sheet
Definition
very large thick mass of glacial ice flowing outward in all directions from one or more accumulation centers.
Term
ice shelf
Definition
forming where glacial ice flows into bays, it is a large, relatively flat mass of floating ice that extends seaward from the coast but remains attached to the land along one or more sides.
Term
kame
Definition
a steep-sided hill composed of sand and gravel originating when sediment collected in openings in stagnant glacial ice.
Term
kame terrace
Definition
a narraow, terracelike mass of stratified drift deposited between a glacier and an adjacent valley wall.
Term
kettle
Definition
depressions created when blocks of ice become lodged in glacial deposits and subsequently melt.
Term
lateral moraine
Definition
a ridge of till along sides of a valley glacier composed primarily of debris that fell to the glacier from the valley walls.
Term
medial moraine
Definition
a ridge of till formed when lateral moraines from two coalescing alpine glaciers join.
Term
outlet glacier
Definition
a tongue of ice normally flowing rapidly outward from an ice cap or ice sheet, usually through mountainous terrain to the sea.
Term
outwash plain
Definition
a relatively flat, gently sloping plain consisting of materials deposited by meltwater streams in front of the margin of an ice sheet.
Term
pater noster lakes
Definition
a chain of small lakes in a glacial trough that occupies basins created by glacial erosion.
Term
piedmont glacier
Definition
a glacier that forms when one or more alpine glaciers emerge from the confining walls of mountain valleys and spread out to create a broad sheet in the lowlands at the base of the mountains.
Term
plastic flow
Definition
a type of glacial movement that occurs within the glacier, below a depth of approximately 50 meters, in which the ice is not fractured.
Term
Pleistocene epoch
Definition
an epoch of the Quaternary period beginning about 1.8 million years ago and ending about 10,000 years ago.

Best known as a time of extensive continental glaciation.
Term
plucking
Definition
the process by which pieces of bedrock are lifted out of place by a glacier.
Term
pluvial lake
Definition
a lake formed during a period of inceased rainfall.
Term
recessional moraine
Definition
an end moraine formed as the ice front stagnated during glacial retreat.
Term
roche moutonnee
Definition
an asymmetrical knob of bedrock formed when glacial abrasion smoothes the gentle slope facing the advancing ice sheet and plucking steepens the opposite side as the ice overrides the knob.
Term
rock flour
Definition
ground up rock produced by the grinding effect of a glacier.
Term
snowline
Definition
the lower limit of perennial snow.
Term
stratified drift
Definition
sediments deposited by glacial meltwater
Term
surge
Definition
a period of rapid glacial advance.

surges are typically sporadic and short-lived.
Term
tarn
Definition
a small lake in a cirque
Term
terminal moraine
Definition
the end moraine marking the farthest advance of a glacier.
Term
till
Definition
unsorted sediment deposited directly by a glaceier
Term
tillite
Definition
a rock formed when glacial till is lithified
Term
truncated spur
Definition
triangular-shaped cliffs produced when spurs of land that extend into a valley are removed by the great erosional force of a valley glacier.
Term
valley glacier
Definition
see Alphine glacier.
Term
valley train
Definition
A relatively narrow body of stratified drift deposited on a valley floor by meltwater streams that issue from the terminus of an alpine glacier.
Term
zone of accumulation
Definition
the part of a glacier characterized by snow accumulation and ice formation.

The outer limit of this zone is the snowline.
Term
zone of fracture
Definition
the upper portion of a glacier consisting of brittle ice.
Term
zone of wastage
Definition
the part of a glacier beyond the snowline where annually there is a net loss of ice.
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