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Section 15.3 Glacial Deposits

Section 15.3 Glacial Deposits. Before. During. Erosional landforms created by alpine glaciers. After. Figure 6.10 C. Glacier acts like a snow plow to scrape and push everything in its path. Plucking and abrasion occur at base of glacier. Plucking - type of glacial erosion

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Section 15.3 Glacial Deposits

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  1. Section 15.3Glacial Deposits

  2. Before

  3. During

  4. Erosional landforms created by alpine glaciers After Figure 6.10 C

  5. Glacier acts like a snow plow to scrape and push everything in its path.

  6. Plucking and abrasion occur at base of glacier. • Plucking- type of glacial erosion • Glacier deposits are left behind as features that alter landscape • Moraines • Drumlins • Outwash • Eskers • Kames • Kettles

  7. Moraine: accumulation of glacial till.Types of moraines: • Lateral moraines: form along sides of a valley • End moraines: form at the end of the glacier • Terminal moraines: are end moraines that mark the farthest advance of a glacier • Recessional moraines: form as the ice front periodically becomes stationary during retreat • Ground moraines: form as the glacier recedes and lays down a layer of till • Medial moraines: form when two valley glaciers come together to form a single ice stream

  8. Outwash Plain: Deposits of sand, gravel, and sediment that is deposited in front of the glacier as it melts

  9. Kamesmall, cone-shaped hills of stratified sand and gravel deposited by streams that were flowing across the top of glaciers

  10. Drumlins are long, smooth canoe-shaped hills • form when an advancing glacier runs over an existing moraine and “smears” it • found in groups • can show the direction that the glacier was moving Direction thatthe glacier was moving.

  11. KettleLakes form in large numbers in the holes left my large blocks of glacier ice

  12. Eskers long, winding ridges that formed when sub-glacial streams filled with sand and gravel sediments deposits

  13. tributaries Medial moraine Ice front / snout Icebergs / calving

  14. 15.4Ice Ages

  15. Ice Ages • There is more than one “ice age.” • There have been about 10 ice ages • As far back as 2 billion years ago, 600 million years ago, 250 million years ago. • The recent cycle seems to be a glacial period about every 250,000 years. • Most recent “Ice Age” began 2 million years ago and ended about 15,000 years ago. • Pleistocene epoch

  16. Causes of the Ice Age (page 331) • Earth’s position (orbit and tilt) • Carbon dioxide (greenhouse effect) • Earth’s landmasses (Pangaea) 4. Mountain building (albedo)

  17. Orbit • Earth is tilted on it’s axis • Varies every 41,000 yrs • Earth “wobbles” as it rotates (precession) • Every 23,000 yrs. • Earth has an elliptical orbit. • Every 100,000 yrs it is extreme So… when the earth is at its extreme tilt and farthest from the sun it its orbit, then we experience extreme “cold spells”

  18. CO2 levels in atmosphere have fluctuated • Increase CO2 causes global warming • Decrease CO2 causes global cooling

  19. Pangaea • Land masses were closer to the poles and farther from the equator at different times • Shifting land masses changed ocean currents • Warm water was prevented from mixing with cool ocean water

  20. Mountain Building • Plate tectonics (convergent plates) create mountains that occupy high elevations producing snow and glaciers. • White snow reflects sunlight (90%), temperatures get colder (Albedo)

  21. Indirect Effects of Ice Age Glaciers • Extinction of some organisms • Changes in some river courses • Sea level fluctuations

  22. The snow and ice first accumulated in central Canada

  23. Ice sheets hundreds feet thick have enormous amount of weight

  24. Earth’s crust “floats” on the asthenosphere.The crust puts pressure on the asthenosphere.

  25. Glacial Rebound Lab

  26. Glacier Quiz! • http://www.funtrivia.com/quizzes/geography/physical_geography/glaciers.html

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