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Geology 12 Presents

Geology 12 Presents. Outline: Chp 14 Mass Wasting (Landslides) Chp 15 Running Water Chp 16 Groundwater Chp 17 Glaciers and Glaciation Chp 18 Wind and Deserts. Glaciers and Glaciation. A: Introduction B: Glacial Erosion and Transport C: Glacial Deposits. Glaciers.

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Geology 12 Presents

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  1. Geology 12Presents

  2. Outline: • Chp 14 Mass Wasting (Landslides) • Chp 15 Running Water • Chp 16 Groundwater • Chp 17 Glaciers and Glaciation • Chp 18 Wind and Deserts

  3. Glaciers and Glaciation A: Introduction B: Glacial Erosion and Transport C: Glacial Deposits

  4. Glaciers

  5. A: Introduction/Glaciers • Glacier: mass of ice composed of compacted snow and recrystallized snow flowing under its own weight under the force of gravity. • Move via: • plastic deformation below 40m just from the shear weight of ice. 2. basal slip: sometimes with the presence of melt water the glacier may slide.

  6. Glacier Movement

  7. Glacier Movement

  8. Copy diagram Crevasse Total surface movement 40m Plastic deformation Basal slip

  9. Types of Glaciers 1. Valley/Alpine Glaciers: confined to mountain valleys (yoodle leh) • Flow down hill • Few km wide by 10’s of km long by several 100 m thick • Ex: Alaskan Alpine Glaciers 2 km wide x 120 km long x 400 m thick ice

  10. 1. Valley/Alpine Glaciers

  11. Types of Glaciers 2. Ice Sheets: BIG • Flow out horizontally in every direction from where the snow accumulates the most a) Continental Glaciers: • Largest: 100s of km long/wide by 3-5 km thick • Ex: Greenland, Antarctica (now) and N. Amer’ during the last ice age 25,000 yrs ago (most of Canada)

  12. Ice Sheets: Continental Glaciers

  13. Types of Glaciers 2. Ice Sheets: b) Ice Caps • <50,000 km2 • Ex: Penny Ice Cap (Baffin Isld), Iceland, Spitsberg Isld. ice crust isostacy

  14. Ice Sheets: Ice Caps

  15. Isostasy

  16. Zone of accumulation • Glacial Movement Firn limit snow Zone of wastage Ice front ice Firn: pebbles of ice; intermediate stage between snow and ice

  17. Glacial Movement • Firn: Pebbles of ice • Intermediate stage between snow and ice

  18. Firn

  19. Glacial Movement Glacial advance: when accumulation > wastage Glacial Retreat: when accumulation < wastage

  20. Glacial Movement Glacial advance: when accumulation > wastage Glacial Retreat: when accumulation < wastage

  21. Calving: process of producing icebergs. glacier ocean

  22. Calving: process of producing icebergs.

  23. Icebergs

  24. Icebergs

  25. B: Glacial Erosion & Transport

  26. B: Glacial Erosion & Transport • Weathering: a glacier is a combination of ice and rock (silt,sand, pebbles, boulders). The primary weathering is mechanical; ice/frost wedging (plucking or quarrying)

  27. Handout WS 17.1 NoteHelper

  28. Glacial Eroded Landforms • Erosion: glaciers carry the sediment within the ice AND grind/polish bedrock via abrasion (rock within the ice grinds below the glacier). • The plucking and grinding creates the following landforms (become visible after the ice is gone):

  29. 1. Glacial Polish: smooth (shines in reflected light) bedrock.

  30. 2. Glacial Striations: hard rocks projecting below the ice cut grooves.

  31. 2. Glacial Grooves

  32. 2. Big Grooves = Finger Lakes New York State

  33. 3. Roche Mountinee: (sheep rock) ice bedrock plucking

  34. 3. Roche Mountinee

  35. 4. Crag and Tail

  36. 4. Crag and Tail

  37. Crag and Tail

  38. 5. Cirques: spoon shaped basin at head of glacial valley.

  39. 5. Cirques

  40. 5. Cirque Lake = Tarn

  41. 5. Cirque Lake = Tarn

  42. 6. Arete: sharp ridge formed by 2 cirques Stop right there, thank you very much….”

  43. 6. Arete

  44. 6. Aretes

  45. 7. Horn: pyramid mountain peak formed by 3 or 4 cirques.

  46. 7. Horn

  47. 7. Horn Arete Arete Arete cirque cirque

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