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51 terms

Geology Chapter 11

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why glaciers are part of water cycle
made of frozen water; melt water is freed
why glaciers are part of rock cycle
erosional agents that accumulate, transport, and deposit sediment
glacier
a thick ice mass that forms over hundred or thousands of years
alpine/valley glacier
a glacier confined to a mountain valley, which in most instances had previously been a stream valley
ice sheet
a very large thick mass of glacial ice flowing outward in all directions from one or more accumulation centers
ice caps
a mass of glacial ice covering a high upland or plateau and spreading out radially
piedmont glaciers
a glacier that forms when one or more valley 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
plastic flow
a type of glacial movement that occurs within the glacier below a depth of approximately 50 meters in which the ice is not fractured
slippage
the entire ice mass slipping along the ground; basal slip
zone of fracture
the upper portion of a glacier consisting of brittle ice
crevasse
a deep crack in the brittle surface of a glacier
surge
a period of rapid glacial advance typically sporadic and short-lived
zone of accumulation
the part of the glacier characterized by snow accumulation and ice formation
zone of wastage
lies below the snowline there is a net loss to the glacier as all of the snow from the previous winter melts so does some of the glacial ice
calving
wastage of a glacier that occurs when large pieces of ice break of into water
ablation
a general term for the loss of ice and snow from a glacier
frost wedging
the mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices
plucking
the process by which pieces of bedrock are lifted out of place by a glacier
abrasion
the grinding and scraping of a rock surface by the friction and impact of rock particles carried by water, wind or ice
striations
scratches or grooves in a bedrock surface caused by the grinding action of a glacier and its load of sediment
polishing
when abrasive actions don't produce striations but polishes the rock
glacial valleys
valley created by a glacier
truncated spurs
Blunt-ended ridge of rock jutting from the side of a glacial trough, or valley.
hanging valleys
a tributary valley that enters a glacial trough at a considerable height above the floor of the trough
pater noster lakes
a chain of small lakes in a glacial trough that occupy basins created by glacial erosion
cirque
an amphitheater-shaped basin at the head of a glaciated valley
glacial trough
a mountain valley that has been widened, deepened, and straightened by a glacier
fiord
a steep-sided inlet of the sea formed when a glacial trough was partially submerged
arete
a narrow knifelike ridge separating two adjacent glaciated valleys
horn
a pyramid-like peak formed by glacial action in three or more cirques surrounding a mountain summit
roche mountonnee
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
inselberg
an isolated mountain remnant characteristic of the late stage of erosion in a mountainous region
glacial drift
an all-embracing term for sediments of glacial origin no matter how, where, or in what shape they were deposited
stratified drift
sediments deposited by glacial meltwater
till
unsorted sediment deposited directly by a glacier
glacial erratic
an ice-transported boulder that was not derived from the bedrock near its present site
lateral moraine
a ridge of till along the sides of a valley glacier composed primarily of debris that fell to the glacier from the valley walls
medial moraine
a ridge of till formed when lateral moraines from two coalescing valley glaciers join
end moraine
a ridge of till marking a former position of the front of a glacier
ground moraine
an undulating layer of till deposited as the ice front retreats
outwash plain
a relatively flat gently sloping plain consisting of materials deposited by melting-water streams in front of the margin of an ice sheet
valley trains
a relatively narrow body of stratified drift deposited on a valley floor by melting-water streams that issue from the terminus of a valley glacier
terminal moraine
the end moraine marking the farthest advance of a glacier
kettle hole
depressions created when blocks of ice become lodged in glacial deposits and subsequently melt
drumlin
a streamlined asymmetrical hill composed of glacial till
esker
sinuous ridge composed largely of sand gravel deposited by a stream flowing in a tunnel beneath a glacier near its terminus
kame
a steep-sided hill composed of sand and gravel originating when sediment collected in openings in stagnant glacial ice
ice age
a time when ice sheets and alpine glaciers were far more extensive than they are today
causes of glaciation
-plate tectonics
-environment/climate changes
-variations in earth's orbit
milankovitch's model for glaciation and the earth's orbit
1. variation in the shape of earth's orbit
2. changes in the angle of the axis
3. wobbling of the axis
consequences of glaciation
-erosional and depositional work
-migration of organisms
-changes in stream courses
-adjustment of the crust
-climate changes
-change in sea level