GLACIATION LECTURE NOTES

VOCABULARY: glacier; alpine; cirque; valley; piedmont; continental ice sheet; Pleistocene epoch; Nebraskan; Kansan; Illinoian; Wisconsin; pluvial lake; interglacial period; snowline; zones of a glacier; zone of accumulation; firn; zone of ablation; meltwater; movement of glacier; front; advance; retreat; stationary; stagnant; crevasses; load; frost wedging; glacial plucking; abrasion; cirque; trough; U-shaped valley; tarn; trough lake; finger lakes; paternoster lakes; fiord (fjord); arête; col; horn; hanging valley; hanging trough; till; moraine; drift; ground moraine; terminal moraine; (end moraine); recessional moraine; lateral moraine; medial moraine; drumlin; erratic; stratified; outwash deposits; outwash plains; valley trains; ice contact stratified drift; kame; esker; kettle; loess

agent--glacier; process--glaciation

In areas of colder climate, ice may accumulate to such a depth that it begins to behave as a plastic and flows--GLACIER

2 types

alpine--occur on mountains; occupy valleys previously made by stream; start as cirque glacier, become valley glacier; may grow to piedmont glacier--on plain at base of mountain range; fed by one or more alpine glaciers

continental ice sheet--broad glacier, irregular shape, blanket terrain

10-11% of earth (6 million sq. miles) covered by glaciers

2 chief requirements

snow accumulation builds the glacier

Pleistocene epoch

glaciations interglacials
Wisconsin

Sangamon
Illinoian

Yarmouth
Kansan

Aftonian
Nebraskan

pluvial lakes--lakes formed in Pleistocene when area had more rain

2 zones of a glacier MELTWATER--results from melting of glacial ice

front, terminus, or snout--leading or outer edge of ice

•advance--covering more territory

•retreat--covering less territory

•stationary--not changing the area of coverage

stagnant--dead--no longer a real glacier

position occurs at lowest or farthest extent of the ice

glacial movement--PRESSURE AND GRAVITY

posts in ice

sides and bottom friction slows, center moves fastest

CREVASSES--cracks in brittle upper surface of the glaciers, form as move over irregular surface, drop

LOAD--material is carried on top, sides, and bottom and body

can carry much larger particles than wind, running water

concentrated on base and sides

erodes and deposits

erodes

direction of movement indicated by upstream side-abraded, striated, gentle slope, downstream side predominantly plucking, steeper slope

glacial landforms--erosional

alpine--

cirque--head of valley formed by glacier, a steep blunt, bowl shaped valley head in a mountain side at a high elevation

tarn--a lake in a cirque

trough--U-shaped glacial valley--valley cross section from erosion on base and sides of glacier

U-shaped valley--cross section of trough

trough lake--lake formed in a trough (depression in trough)

finger lakes--behind recessional moraines

paternoster lakes--chain of small round lakes

fiord (fjord)--ocean flooded glacial valley

arête--a narrow-jagged knife-edged (saw-toothed) ridge created by two cirques that have eaten into ridge from both sides

col--a saddle on a divide or pass (gap) through an arête

horn--sharp, hornlike or pyramid shaped mountain peak formed by glacial erosion on each side

hanging valley--stream valley where stream drops into trough; floor is notably higher than the floor of the trunk valley into which it leads

hanging trough--smaller tributary glacial valley, higher up, did not have as much erosional power

NOTE: The text improperly defines hanging valley!

continental

scours land out, leaves lots of lakes

depositional--mainly in downstream portions or as retreats

drift--ALL GLACIAL DEPOSITS--water and/or ice deposits

till--non-sorted material (size, weight) where released DIRECTLY FROM ICE

moraines--landforms made of concentrated till

ALL TILL IS DRIFT BUT NOT ALL DRIFT IS TILL

types of moraines

other till deposits

drumlins--streamlined hills molded by flowing ice; see text page 499

direction of flow


erratics--pieces of rock different from bedrock beneath brought to an area by a glacier

other deposits--made of drift

meltwaters erode, transport, and deposit--sort and stratify

3 types
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