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Glacial Erosion

Glacial Erosion. Ch 15: p 277-281. Glaciers:. Enormous masses of moving ice created by the accumulation and compaction of snow. Powerful agents of erosion ~ have carved some of the most spectacular features on Earth’s surface

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Glacial Erosion

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  1. Glacial Erosion Ch 15: p 277-281

  2. Glaciers: Enormous masses of moving ice created by the accumulation and compaction of snow. Powerful agents of erosion ~ have carved some of the most spectacular features on Earth’s surface The growth of a glacier depends on whether the snowfall from winter is greater than the snow melt in summer!

  3. 2 types of Glaciers: Alpine (aka Valley) Continental (ice sheets) • Mountainous areas • long, narrow-wedged mass of ice • Best developed valley glaciers found in Alaska, the Himalayas, the Alps… • Covers large land areas • Found only in Greenland and Antarctica today

  4. Valley Glacier

  5. Continental ice sheet The Antarctic Ice Sheet is 1.5 times the size of the US and in some places more than 4,000 m thick

  6. How Glaciers form:

  7. Step 1: Snow accumulates. More snow falls during the winter than melts in the summer.

  8. Trans-Labrador Highway WOAH! http://tlhwy.com/south/winter/index.html

  9. Step 2: Snow changes to firn. As snow accumulates, its weight compresses the individual snowflakes to form firn.

  10. Step 3: Firn is compressed to form solid glacial ice

  11. Step 4: The ice begins to move. Continental Valley

  12. Some Facts • Glaciers hold 75% of the Earth’s fresh water. • 10% of land is covered by them. • If they all melted the sea level would go up about 70m • Artic ice is over 4,200 m thick in some spots.

  13. 2 types glacial movement: Basal Slip Internal plastic flow • The weight of the ice exerts enough pressure to melt the ice where it contacts the ground • This melt water acts as a lubricant and allows the glacier to slip forward, including over small barriers • The weight of the ice and gravity causes the ice crystals to slip over each other • Speed of this flow is faster nearer the surface and at its center…why?... • friction!

  14. How do glaciers erode the surface? • Plucking –freeze/thaw process lifts particles into ice • Abrasion- like sandpaper-rocks caught up on the bottom scrape the ground under it, making striations

  15. Glaciers pick up lots of sediment as they advance over the land. http://www.geographyjim.org/Newzealandglacier.jpg

  16. Valley glacier features http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/GEO_9/geo_images_9/Fig9.20.gif

  17. Cirque • A bowl-shaped depression located where a glacier begins to form

  18. http://crevassezone.org/Photos/Graphics/4163L-(Cirque).jpg

  19. Horn Kinnerly Peak - Glacier National Park • A tall, pointed rock peak left at the top of a mountain http://www2.nature.nps.gov/geology//parks/glac/car0348.jpg

  20. The most famous horn in the Alps… The Matterhorn • Located on the boundary between Switzerland and Italy, the Matterhorn’s summit is 4478 m above sea level.

  21. Arete – spines or ridges of rock that separate glacial valleys

  22. U-shaped Valley - Yosemite National Park

  23. V-shaped valleys become U-shaped valleys as glaciers move through them… Step 2 Step 1 A typical river valley Over time, running water cuts a deeper V-shape. Step 3 Glacier fills valley, widening and straightening the channel Step 4 Glaciers melt leaving a U-shaped valley

  24. U-Shaped Valley Formation

  25. Hanging Valley • a small valley that has not eroded as deep as the main valley that it is connected to • Waterfalls often form at hanging valleys.

  26. Continental features Striations- parallel scratches made from rocks in ice scraping against bedrock

  27. Kettle Lakes A shallow body of water made from ice blocks

  28. Glacial Deposition: • Drumlins--hills of sediment deposited by the glacier- till

  29. Drumlin Formation

  30. Glacial DEPOSITION • Eskers • Winding ridges of stratified drift • Deposited by meltwater streams • Mined for gravel (aggregate)

  31. Esker Formation

  32. Glacial DEPOSITION • Kames • Cone shaped stratified deposits • Deposited at end of meltwater streams

  33. Kames

  34. MORAINES moraine • MADE OF TILL- unsorted sediment outwash http://www.helsinki.fi/~jhyvonen/PB/M/Cerro%20Tronador%20moraine-pp.JPG

  35. Moraines • Terminal Moraine – Till deposit that marks the furthest advance of the glacier. • Recessional Moraine – Till deposit that marks pauses in the ice fronts retreat Till (moraine)

  36. moraine outwash

  37. Ground Moraine- flat till deposits between recessional moraines Recessional moraine Recessional moraine Ground moraine Terminal moraine outwash

  38. Other Moraines • Lateral Moraines- These are on the sides of valley/mountain glaciers • Medial Moraines – When two glaciers run along one another/collide these moraines form. • Both are composed of till

  39. Glacial DEPOSITION

  40. MORAINES

  41. Types of Glacial sediment: ERRATICS- • Boulders carried great distance by the glacier • Don’t match surrounding rock

  42. Types of Glacial Sediments (drift) • TILL- unsorted; deposited by ice • STRATIFIED DRIFT- layered (sorted into layers by size); deposited by meltwater streams • OUTWASH- sorted sand; deposited by meltwater

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