Glaciers Chapter 17. Why glaciers? 10% of earth covered by ice 85% Antarctica 11% Greenland 4% elsewhere Glaciers store about 75% of the world's freshwater.

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Presentation transcript:

Glaciers Chapter 17

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

What is a glacier? Mass of moving glacial ice created by the accumulation of snow glaciers always moving forward at terminus

The Norwegian Arctic Archipelago of Svalbard is 60% covered by glaciers. Arctic

East Antarctic Ice Sheet Antarctica

Nev. Piramide, Cordillera Blanca, Peru photo: Michael Hambrey Tropical glaciers

Mid-latitude glaciers: Nepal Himalaya Photo: A. Racoviteanu

Glacier birth accumulation snow metamorphism compression

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

Mass Balance Accumulation Ablation

Avalanche-fed glaciers Nev. Chacraraju, Cordillera Blanca, Peru

Melting

Calving

Mass balance area where ice accumulates area where ice melts Equilibrium line altitude (ELA) accumulation = ablation balance = 0

Austin Post photo South Cascade Glacier, Sept 20, 1966 From NSIDC

Exit Glacier, Alaska

Bar graph showing winter, summer and net balance at Storbreen during

Movement of ICE

1. Internal deformation ALL glaciers move by deformation Factors controlling rate of deformation: depth of ice slope Stress: Compaction (weight) Strain = amount of deformation

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????

Regelation requires pressure-melting, transfer of water around the bump, and transfer of heat through it

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