1. Glaciers Geog 3251 Mountain Geography summer 2006 Adina Racoviteanu

2. Glaciers 1. Glacier formation, type and motion 2. Glacial landforms 3. Glacier-related hazards 4. Glaciers and climate (Friday & Monday)

3. 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

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

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

6. East Antarctic Ice Sheet Antarctica Photo: MH

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

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

9. Is this a glacier? No- Icebergs are NOT glaciers

10. What climatic conditions are needed for glaciers to form? cool summer temperatures in (< 0 deg. C) high winter precipitation Why don’t we have glaciers in Siberia or parts of Antarctica?

11. The glacier story: 1.glacier birth accumulation of snow compression of snow by weight of layers snow metamorphism: snow grains squashed together--> conversion to ice

12. 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

13. The glacier story: 2. glacier growth Accumulation: snowfall avalanches : e.g. Karakoram, Andes wind re-deposition superimposed ice (rain freezing)

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

15. Wind (re)deposition Nev. Huascaran, Cordillera Blanca, Peru photo:Jürg Alean

16. The glacier story (cont’d): 3. glacier decay Ablation: melting evaporation/sublimation (only cold arid areas) calving wind erosion

18. Calving Hubbard glacier, Alaska photo:Jürg Alean

19. Thermodynamic classification of glaciers: warm based thawed from their bed 1) Warm glaciers

20. Qori Kalis, Quelcaya Ice Cap, Peru Warm glaciers

21. 2) “Cold” glaciers –frozen to their beds –ice below pressure melting point –remain well frozen; melting only at surface

22. Cold glaciers: Antarctica Hughes Glacier, Dry Valley, Antarctica photo: MH

23. Glacier movement When glacier gets >20m thick, flow occurs has to do with behavior of ice under pressure Ice is solid but it flows!

24. Glaciers flow!! East Greenland

25. False-colour Landsat image Malaspina Glacier, Alaska (NASA, 31.8.2000). Compression

26. Two types of glacier movement 1) PLASTIC DEFORMATION 2) BASAL SLIDING

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

28. 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????

29. Glacier flow Steady-state flow rates 5-500m/a Fastest flow in upper/central parts ( less friction)

30. 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

31. Benefits of glaciers provide a reliable water supply for hydro-electric power generation & agriculture Cordillera Blanca, Peru

32. Canals Agricultural terraces Technological advances of the Incas Agricultural terraces Inca roads and trails Architecture

33. Benefits of glaciers recreation (climbing) Scenic value Pastoruri, Peru -major tourist attraction

34. Glacier hazards Glacier surges Glacier lake outburst floods (GLOF) Ice avalanches Falling ice

35. Glacier surges Glacier surges = short-lived episodes involving a sudden increase in ice movement by at least one order of magnitude Glacier surge areas:  Alaska, and theYukon Territory, Canada;  Svalbard; Iceland; Greenland;  the Russian High Arctic;  Asia (the Pamirs, theTien Shan and the Karakoram)

36. Variegated glacier, Alaska velocities of 100m/day dramatic increase in flow rate, 10-100 hundred times faster than its normal rate

37. Himalayas: morraine-dammed lakes

38. After the glacier lake outburst….

39. Ice avalanches: May 30, 1970 Peru disaster A large mass of ice and rock slid from a vertical face on Nevado Huascaran Debris reached a velocity of 280 km/hr Buried 2 towns death toll: 20,000.

40. Questions? Glaciers online NSIDC: All about glaciers NSIDC: All about glaciers