EXAM 4 (FINAL) Flashcards
what is a hanging trough?
where tributary glacier intersects primary alpine glacier
what is a tarn?
lake left in a cirque after glacial retreat
what is a valley train?
debris left in the alley as the glacier retreated
(often leads to braided stream)
what are fiords?
where troughs open to the sea with glacial retreat
what are landslides?
when failure steep sided trough walls
what is a trough lake?
elongated lakes left in glacial trough after glacial retreat
what is a col?
gap or opening in the glacial trough wall
what is a crevasse?
deep open crack in glacial ice surface
what are three causes of environmental impact?
disrupted drainage
disrupted soils
some hydropower production
what is disrupted drainage?
- disruption of a drainage pattern
- alters flow
what are ice shelves?
floating sheet of ice permanently attached to a landmass (enormous and may be several hundred feet thick)
what are the two continental ice sheets today?
Antarctica & Greenland
how big is Antarctica?
5.4 million sq miles
[ice – up to 13,000 ft thick]
how big is Greenland?
656,000 sq miles (3 times size Texas)
[ice – up to 10,000 ft thick]
for Greenland, what percentage of icebergs are below sea level?
90%
how is Greenland set up structurally?
- many outlet glaciers that extend to the sea
- tongues break off creating calving (icebergs)
how is Antarctica set up structurally?
- ice in interior extends well below sea level
- thus, at sea interface creates large ‘ice-shelves’
- ice shelves are enormous and may be several hundred ft thick (largest is ross ice shelf)
when did the Pleistocene Glaciation occur?
approximately 2.5 million to 11,700 years ago
what was the Pleistocene Glaciation?
over 20 glacial events occurring during this time period with periods of glacial retreat
what causes these cycles of glaciation?
variations in…
- the earth’s tilt
- Earth’s eccentricity in its orbit about the sun
- the arrangement of the continents through plate tectonics
- the ocean-air systems
what were some impacts of the Pleistocene Glaciation?
1) temperature change – 5 to 10 degrees cooler
2) isostatic adjustment – ice weight forced continents down 300m
3) change in sea level – off Atlantic decrease 137 meters
4) modified drainage systems (Missouri river once flowed north into Lancaster Sound)
what are striations?
abrasion marks
(trend in direction of ice movements)
what are stratified drift/tills?
glacially sorted debris at edge of glacier
what are glacial erratics?
rock derived from poleward locations but carried south by glacial ice