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

5. East Antarctic Ice Sheet Antarctica

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

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

9. Glacier birth accumulation snow metamorphism compression

10. 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

11. Mass Balance Accumulation Ablation

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

13. Melting

14. Calving

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

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

19. Exit Glacier, Alaska

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

21. Movement of ICE

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

24. 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????

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

26. 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