Glaciers

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arete

a knife edged ridge formed by two cirques that have eroded towards one another

horn

a pointed mountain peak formed by 3+ cirques that surround a peak

glacial abrasion

a sandpaper effect on substrate striations run parallel to direction of ice movements

zone of ablation

area of net ice loss

zone of accumulation

area of net snow addition

how do glaciers move?

basal sliding: meltwater forms at base of glacier, water decreases friction and ice slides plastic deformation: occurs below about 60m depth, grains of ice slowly change shape, new grains form while old grains disappear, crevasses form at surface, upper zone too brittle to flow

erratics

boulders dropped by glacial ice

cirques

bowl shaped basins high on a mountain

types of mountain glaciers

cirque glaciers:fill mountain top bowls valley glaciers: flow like rivers down valleys mountain ice caps: cover peaks and ridges piedmont glaciers: spread out at the end of a valley

glacier-forming conditions

cold local climate (summer wont melt snow) abundant snow (more fall than melt) snow not removed by avalanche or wind

depositional landforms

end moraines: form at toe of glacier terminal moraines: farthest edge of flow grounds moraine: till left behind by rapid ice retreat kettle lakes: formed from stranded blocks of ice eskers: long channels of gravel and sand

glacial drift

glacial till, erratics, loess

major ice sheets on earth

greenland and antarctica

mountain glaciers

high to low elevation in mountain setting

glacial consequences

ice loading and glacial rebound sea level rise and fall pluvial features- large lakes formed during ice age

causes of glaciation

plate tectonics, atmospheric chemistry, changes in orbital geometry

glacial till

sediment dropped by glacial ice all grain sizes, unsorted, unstratified

how a glacier forms

snow is transformed into ice, buried by later falls, compresses, melts and recrystallizes, interlocks can form over tens or thousands of years

toe

the leading edge of a glacier

why do glaciers flow?

the pull of gravity is strong enough to make ice flow;glaciers move in the direction of its surface slope

glaciers

thick masses of recrystallized ice that last all year long, flow via gravity, and are both mountain and continental presently cover 10% of earth

moraines

unsorted debris deposited by a glacier lateral: forms along flank of a valley glacier medial: mid ice moraines from merging of lateral moraines

continental glaciers

vast ice sheets covering large land areas ice flows outwards from thickest part of sheet

equilibrium line

where the zone of accumulation and zone of ablation meet

loess

wind-transported silt unstratified deposits


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