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Glaciers

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?.

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Glaciers

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  1. Glaciers Chapter 17

  2. 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

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

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

  5. Antarctica East Antarctic Ice Sheet

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

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

  8. Glacier birth • accumulation • snow metamorphism • compression

  9. 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 Air bubbles density > 860 kg/m3

  10. Mass Balance • Accumulation • Ablation

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

  12. Melting

  13. Calving

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

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

  16. Exit Glacier, Alaska

  17. Bar graph showing winter, summer and net balance at Storbreen during 1949-2004. www.nve.no

  18. Movement of ICE

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

  20. 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????

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

  22. Glacier movement summary 1. Temperature at base of glacier is key WARM glaciers: sliding + deformation COLD glaciers: deformation only strength 2. Gravity main driving force s = rgh*sina stress θ compression gravity

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