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Published byErica Gilmore Modified over 9 years ago
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Glaciers Chapter 17
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Why glaciers? 10% of earth covered by ice 85% Antarctica 11% Greenland 4% elsewhere Glaciers store about 75% of the world's freshwater Distribution: found at various latitudes and climates
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What is a glacier? Mass of moving glacial ice created by the accumulation of snow glaciers always moving forward at terminus
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The Norwegian Arctic Archipelago of Svalbard is 60% covered by glaciers. Arctic
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East Antarctic Ice Sheet Antarctica
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Nev. Piramide, Cordillera Blanca, Peru photo: Michael Hambrey Tropical glaciers
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Mid-latitude glaciers: Nepal Himalaya Photo: A. Racoviteanu
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Glacier birth accumulation snow metamorphism compression
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Air bubbles Glacial Ice formation SNOW: seasonal snow void spaces FIRN (névé): snow that has lasted more than one year less void space density ~ 550 kg/m3 ICE: compacted, air pores not connected density > 860 kg/m 3
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Mass Balance Accumulation Ablation
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Avalanche-fed glaciers Nev. Chacraraju, Cordillera Blanca, Peru
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Melting
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Calving
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Mass balance area where ice accumulates area where ice melts Equilibrium line altitude (ELA) accumulation = ablation balance = 0
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Austin Post photo South Cascade Glacier, Sept 20, 1966 From NSIDC
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Exit Glacier, Alaska
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Bar graph showing winter, summer and net balance at Storbreen during 1949-2004. www.nve.no
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Movement of ICE
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1. Internal deformation ALL glaciers move by deformation Factors controlling rate of deformation: depth of ice slope Stress: Compaction (weight) Strain = amount of deformation
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2. Basal sliding needs liquid water! Warm-based glaciers only glacier slips over the rock surface less friction -water acts as lubricator -sliding What if the glacier encounters a bump????
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Regelation requires pressure-melting, transfer of water around the bump, and transfer of heat through it
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Glacier movement summary 1. Temperature at base of glacier is key WARM glaciers: sliding + deformation COLD glaciers: deformation only 2. Gravity main driving force gh* sin stress strength gravity θ compression
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