Glaciers
“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
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.
There are 3 Categories of Glaciers1. Valley (Alpine)
Glaciersfound in
mountainous regions
high altitudesEx. Alps (New
Zealand and Europe), Rockies
Valley or Alpine Glacier
Ice Sheets (Continental Glaciers)Much largerFlow direction is
from an area of thick ice to thin ice
Ex. Greenland, Antarctica
3. Tidewater GlacierFlow far
enough to reach out into the ocean
Create icebergs
Ice calving
Glacial Retreat
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
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).
Glacial Erosion
Striations and Grooves
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
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
DrumlinsA drumlin is
tear-shaped ridge showing direction of ice flow
Drumlins
Glacial ErraticsLarge boulder left behind by the glacier
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
Kames
EskersOne of many
eskers running across the northwest of Canada
Muir Glacier 1941 and 2004
Massive melting – Holgate glacier, Alaska 1909 and 2004