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Geo 1 Glacial environments
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Geo 1 Glacial environments

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geography 1 ES1A and ES1B

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  • 1. Glacial environments
  • 2. Sweden after the last ice age around 10,000 years ago Above sea-level Under sea-level
  • 3. A glacier is a system• Inputs: accumulation of snow and debris• Storage: ice and debris• Outputs: melt, vapour and sediment
  • 4. Glacial systems• When accumulation is greater a glacier advances• When ablation (loss) is greater a glacier retreats• If accumulation = ablation a glacier is steady
  • 5. Glaciers move byinner deformation
  • 6. Alpine glaciers that ablate on land• Ablation leaves lakes and/or deposition
  • 7. Coastal glaciers that ablate into the ocean• Ablation causes calving = icebergs
  • 8. Glacial erosion• Glaciers carry abrasive material• Rate of erosion = geology + velocity + weight + load• Crushing (weight)• Plucking (freezing)• Abrasion (by debris)
  • 9. Landforms and erosive features Evidence of glaciation
  • 10. Roche moutonnée (sheepbacks)• Tear-shaped rock formations shaped by ice• Blunt, broken end away from direction of ice flow, caused by plucking
  • 11. Roche moutonnée (sheepbacks)Lee side Stoss side Ice flow
  • 12. Roche moutonnée - Farsta
  • 13. Visible on roche-moutonnées• Small details reveal ice movement
  • 14. Striations (scratches)
  • 15. Localstriations in Farsta
  • 16. Glacial groove? at Orhem –near Flaten (p-form)
  • 17. Chatter marksDirection of movement
  • 18. Hälsingland
  • 19. Large scale glacial forms – features oferosion
  • 20. Cirques/corries• A short alpine glacier that forms in a hollow depression called a cirque (also known as a corrie)
  • 21. Cirque formation
  • 22. Arêtes and pyramidal peaks• An arête is a sharp ridge formed when two cirques cut back• A pyramidal peak is formed by 3 or more cirques cutting back
  • 23. A glacial u-shaped valley (trough)• Misfit river – seems too small
  • 24. Fjord (drowned glacial valley)with a hanging valley• A hanging valley is a cut-off tributary glacier
  • 25. Ribbon lakes• Filled glacial valleys (rock basins)
  • 26. Glacial valley with rock basin forming a ribbon lake
  • 27. Glacial deposition• Post-glacial landscapes contain many features “left behind” after glaciation• Formed of till and moraines – Unsorted and unstratified “soils” composed of different particle sizes – boulders, pebbles, clay
  • 28. Deposition: erratics• Erratics are large “foreign” boulders transported by glaciers
  • 29. Erratics – transported boulders Orhem – near Flaten
  • 30. Coastal erratic Hälsingland
  • 31. Deposition: drumlins• Streamlined, teardrop shaped hills & hillocks• Formed of till left by glaciation• Blunt end facing opposite ice flow• Often found in “shoals”
  • 32. DrumlinsIce flow
  • 33. Deposition: moraines• Deposits of material left by retreating glaciers• Consist of unsorted till and erratics• Terminal/end moraine – Deposited by retreating glacier at its point of farthest reach – May create a dam holding a proglacial lake• Lateral moraines – Deposited along the sides of retreating glaciers
  • 34. Moraines
  • 35. Lateral moraine Terminal moraine
  • 36. Eskers – gravel ridges• Meltwater forms a tunnel under a • After retreat of the ice, material glacial ice sheet collected in the tunnel is left to• Tunnel fills with rocks, sand and form a ridge gravel
  • 37. Near SiljanAfter glacial retreat this sharp-ridged eskerWould have been above sea level
  • 38. Eskers – economic benefits• Traditionally used as roads• Used for natural water filtration• Mined for materials – sand, gravel and stones for construction
  • 39. Living in glaciated regions Description of landscape:• Most sedimentary rocks have been removed• Granites and gneiss rocks are less porous so the landscape tends to hold a lot of water• Makes the ground swampy, many lakes and soils are in general thinner• Glacial soils (clay) collects in valleys
  • 40. Living in glaciated regions• Soils generally less fertile (soil is a resource)• There is less agricultural land – too much rock• Ground needs draining• High latitudes means shorter growing season• Wheat and grasses, forestry, livesto ck are more common
  • 41. Making new land• The agricultural land shortage in Sweden during the 1800s was so acute that during the period 1880 – 1950 over 20,000 lakes were sunk to create new farmland
  • 42. Alpine regions• Glaciation produces steep mountains with deep valleys• Difficult communications (roads etc)• Limited land for building• Snow for much of the year• High altitiudes lowers biodiversity and growing season• Greatest risks are from landslides (rock, mud, soil) and avalanches (snow)
  • 43. Alpine regions• Advantage is the availability of hydropower• Modern communities turning to winter sports for as an economic resource