Glaciers and ice age
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2% of Earth’s water in ice
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Today 10% Earth’s surface ice cover
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Last ice age- Plestocene Epoch (1.6 to 10,000 yrs. ago) ~ 30% cover
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Important source of fresh water during melting
Glaciers
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Occur at high latitudes and elevations
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Increasing pressure, air is squeezed out: snow – firn – ice.
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Deep in glacier: ice flows like viscous fluid
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Surface of glacier: brittle ice- crevasses
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Contain large amount of rock debris
Glacier types
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Continental: Greenland; Antarctica
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Piedmont: valley glacier at foot of Mt.
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Ice- cap: summit glacier
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Ice-field: extensive Mt. glacier
Glacier budget
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Zone of accumulation (net gain)- head of glacier: more snow in winter than melts in summer
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Zone of Ablation (net loss)- foot of glacier: net loss by melting.
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Slow glaciers: cm/day; fast: m/day
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Glacial surge: 100m/day-meltwater at base

Glacial features
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U-shaped valleys: formed by erosion of valley glacier (not V shaped like river)
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Fiord: flooding of U-shaped valley
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Deposits: Till- sediment produced by melt water (sand, gravel, boulders).
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Moraines: landforms composed of Till.
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End or terminal moraines: farthest extent of ice
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Recessional moraine: retreating glacier
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Esker: linear moraine due to meltwater
Sea-level change
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Pleistocene glaciation: lower sealevel by 100m (300 ft)- land bridge across Bering strait (Alaska-Russia)- migration of humans/animals from Asia 11-8,000 yrs ago.
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Caused flooding of valleys: fiords, estuaries, harbors
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If all polar ice melts today: rise of 40m (130 ft)
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London, L.A. Tokyo, N.Y.C. underwater
Isostaic rebound
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Weight of 3 km (2 mi) of Pleistocene ice loaded down continental crust into Earth’s mantle.
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Melting of ice (10,000 yrs.) resulted in slow (mm/yr) uplift of crust- raised beaches in northern latitudes- Baltic, Hudson Bay, N. Europe. Several meters uplift.
Pleistocene lakes
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Formed by runoff of meltwater- high rainfall, lower evaporation- very large lakes: most dry or smaller now.
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Great Salt Lake (Lake Bonneville)
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Great Lakes, Finger Lakes, NY,
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Pyramid Lake, Nevada,
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Lake Agassiz, Manitoba
Pleistocene ice age
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First recognized by Louis Agassiz, 19 th
cent. geologist.
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Ice c overed northern hemisphere
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Climate zones moved south
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Animal/plants/humans moved south
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Moana Loa (19 deg. N), Hawaii- ice cap