“rivers of ice” mass movement of frozen ice on land form at high latitude or high elevation last...
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Glaciers
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“RIVERS OF ICE”Mass movement of frozen ice on landForm at high latitude or high elevationLast extension of ice here began 20,000 years
ago and receded about 10,000 years ago.Today only covers 10% of land surface
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Ice Flow
Glaciers are not static they are dynamicFormation:A steady accumulation of snow piles up
and compresses layers beneath – these compressed layers turn into ice
Force of gravity continuously pulls ice downward
Movement:Fastest ice is found on the surface at
center of valleyRate varies from a few cm to meters per
day.
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There are 3 Categories of Glaciers1. Valley (Alpine)
Glaciersfound in
mountainous regions
high altitudesEx. Alps (New
Zealand and Europe), Rockies
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Valley or Alpine Glacier
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Ice Sheets (Continental Glaciers)Much largerFlow direction is
from an area of thick ice to thin ice
Ex. Greenland, Antarctica
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3. Tidewater GlacierFlow far
enough to reach out into the ocean
Create icebergs
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Ice calving
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Glacial Retreat
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Budget of a GlacierGlacier accummulation = snow adds to
the weight of a glacierGlacier Wastage (ablation) = melting and
calving.When accummulation is greater than
wastage = glacier advancesWhen accummulation is less than wastage
= glacier retreatsIf accummulation = Wastage = glacier
remains stationary
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Glacial Erosion – Two Key MethodsPlucking and Abrasion
Features of Glacial Erosion:U-shaped valleys, sharp ridges (Aretes),
pyramid peaks (Horns), water-filled valleys (Fjiords), and bowl shaped valleys (Cirques).
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Glacial Erosion
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Striations and Grooves
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Depositional Features of Glaciersaka Glacial Dump Drift = any sediment deposited by moving
ice2 Types:1. Stratified Drift = well-sorted sediments
deposited by streams (meltwater)2. Till = unsorted sediment, deposited by
moving ice
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Deposits of Till
lateral moraines form along valley walls
medial moraines form where 2 lateral moraines meet
end moraine left at terminus of glacier where it retreats
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DrumlinsA drumlin is
tear-shaped ridge showing direction of ice flow
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Drumlins
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Glacial ErraticsLarge boulder left behind by the glacier
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Deposits of Stratified DriftKame : a small hill
forms where sediments accumulate beneath ice.Esker: forms from under-glacial streamsKettle: a depression that can be water-filled
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Kames
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EskersOne of many
eskers running across the northwest of Canada
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Muir Glacier 1941 and 2004
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Massive melting – Holgate glacier, Alaska 1909 and 2004