lecture_8 - AMOUNT AND RATE OF GLACIER EROSION • Narrow...

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LECTURE 8 - GLACIAL EROSION AND RESULTANT LANDFORMS TYPES OF GLACIER EROSION A brasion revealed by smoothing, round., scratch., polish. Plucking abrupt, steep, ragged side on protruderance regelation assisted works best in jointed rocks -> quarrying may exceed ablation rate -> char. basal layer FACTORS CONTROLLING EROSION RATES Temperature warm glaciers erode more Debris harder -> more ablation more tools -> more erosion Water lubricates surface -> retards scratching freezing and thawing -> asset to plucking may be responsible for some fluting , grooves mostly where ice thin Thickness and velocity erosion rate vs. o. b. pres. & shear stress increases then decreases decrease due to pressure melting Resistance and structure of bedrock hardness, jointing, permeability
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Unformatted text preview: AMOUNT AND RATE OF GLACIER EROSION • Narrow ice streams (10s km) Yosemite Valley - 450 m Fjord in Norway -> 1000 to 2000 m 900 m basins down at the heels profile • Wide ice streams (100s km) Great Slave Lake -> 600 m Great Bear Lake -> 400 m Lake Michigan -> 300 m; -60 asl • Laurentide ice sheet (1000s km) drift thick -> average of 10 m low due to low relief and hard rocks with clay perhaps as much as 120 m rates of erosion 0.5 to 5.0 mm per year (1.0 mm average) PRODUCTS OF GLACIER EROSION • Small scale striae and striations whalebacks glacial grooves roches moutonnees friction cracks rock drumlins • Large scale U shaped valleys cirques spurs arete s tarns horn paternoster lakes col hanging valleys trimline...
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lecture_8 - AMOUNT AND RATE OF GLACIER EROSION • Narrow...

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