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GLACIERS AND GLACIATION II

GLACIERS AND GLACIATION II. Topics. Glacial landforms Glacial sedimentation Permafrost Glacial lakes Glaciations and global climate. Terminal moraine. Courtesy Gerald Osborn. Other Glacial Landforms . Drumlins- Elongated hills of glacial till Point down-glacier Eskers

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GLACIERS AND GLACIATION II

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  1. GLACIERSAND GLACIATIONII

  2. Topics • Glacial landforms • Glacial sedimentation • Permafrost • Glacial lakes • Glaciations and global climate

  3. Terminal moraine Courtesy Gerald Osborn

  4. Other Glacial Landforms • Drumlins- • Elongated hills of glacial till • Point down-glacier • Eskers • Sinuous ridges of stratified till • Form in tunnels under the ice sheet • Some times 100km long or more

  5. Drumlin field in Wisconsin

  6. Permafrost • Frozen ground • Found in Arctic • North America • Russia • Formed during last ice age • More than 1000 m deep in places • Global warming -> melting of permafrost

  7. Distribution of permafrost in the northern hemisphere Fig. 12.29

  8. Lateral variations in permafrost in Siberia Fig. 12.30

  9. Glacial Lakes • Pluvial Lakes- • Due to wetter climate • Examples: Lake Bonneville, Death Valley • Lake Bonneville flood into Snake River Canyon • Proglacial Lakes • In front of the glacial sheet • Ice dammed lakes • Examples: Great Lakes, Lake Missoula

  10. Lake Bonneville- 14,000 yrs ago- Utah

  11. Lake Bonneville Flood • The lake was up to 1000 feet deep • A ridge on the north side gave way • Peak flow = 33 million cubic feet/second • 33 MCF would fill a tanker train 165 miles long • A raft would move at 75 mph on a wave 300 ft high • Flood left behind giant ripples

  12. Glacial ages • Northern Europe & North America heavily glaciated • Peak of glaciation 18,000 years ago • Ended about 10,000 • We are still in the cold part of the climate cycle • Episodic climate changes • At peak glaciation • Average global temperature only 5 degrees colder

  13. Effects of Past Glaciation • Glacial ages • Direct effects in North America • Scoured much of Canada • Cut Great Lakes • Deposited till & flattened Midwest • Extensive alpine glaciation in mountains • Allowed Natives to walk from Siberia

  14. Effects of Glacial Ages • Indirect effects • Pluvial lakes • Lowering of sea level • Fiord • Crustal rebound

  15. Causes for glaciation • Astronomical • Variations in solar radiation • Atmospheric changes • Tectonic causes

  16. Causes for glaciation • Astronomical (Milankovitch cycles) • Eccentricity of orbit (100,000 yr cycle) • Wobble of rotation axis (41,000 yr cycle) • Precession of equinox (23,000 yr cycle) • Variations in solar radiation

  17. Variations of Earth’s orbit

  18. Tilt of Earth’s Rotation Axis

  19. Wobble of the rotation axis: Precession

  20. Fig. B12.5

  21. Causes for glaciation • Atmospheric changes • CO2 (Greenhouse effect) • Volcanic ash • Tectonic causes • Continents near the poles • Oceanic circulation patterns

  22. Gas Concentrations in Deep ice core-Antartica Fig. 12.34

  23. Causes for glaciation • Tectonic causes • Continents near the poles • Oceanic circulation patterns

  24. Paleozoic (300 Ma) Glaciation

  25. What if the glaciers melt?

  26. Retreating Rhone Glacier S. C. Porter

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