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Gifts of the Glaciers

Gifts of the Glaciers. Glacial Landforms. Gifts of the Glaciers. Moving ice of glacier was responsible for water, landforms, and soil characteristics and patterns of today Sculpturing of bedrock materials Erosion of bedrock Deposition of glacial drift. Glacial Landforms.

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Gifts of the Glaciers

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  1. Gifts of the Glaciers Glacial Landforms

  2. Gifts of the Glaciers • Moving ice of glacier was responsible for water, landforms, and soil characteristics and patterns of today • Sculpturing of bedrock materials • Erosion of bedrock • Deposition of glacial drift

  3. Glacial Landforms • Glacial landforms dominate the Great Lakes region • Northeastern Illinois • Northwest Indiana • Most of WI, MI, MN, and Ontario

  4. Glacial Landforms • Effects of moving ice: • Leveled off the existing hills • Filled in valleys • Blocked the drainage of the rivers • Gouged out major basins (ex: GLB) • Processes involved: grinding, erosion, leveling, and depositing.

  5. Glaciers perform, in many ways, like an excavator.  Although they can push weak material, like gravel, like a bulldozer blade, they are far more likely to lift material out of place, like a backhoe, or scratch it in place, like a ripper.  And, like a bulldozer, glaciers are poor at eroding rock unless it is already weakened.

  6. Glacial Erosion • Rock Failure: • The first step in glacial erosion is rock failure. • Water, ice causes cracks in rocks

  7. Glacial Erosion • Two main types of glacial erosion • Plucking (analagous to a backhoe). • Abrasion • Plucked debris in basal ice grinds into the bedrock, just like sandpaper across wood

  8. Plucking

  9. Abrasion

  10. Glacial Erosion • Glacial / Fluvial Processes: At the bed of warm-based glaciers, water is present in it’s fluid state. • This water flows underneath the glacier and assists erosion by removing erosional products, especially silt.  • When water collects into subglacial channels, it can be sufficiently powerful to erode by itself

  11. Subglacial view of basal debris

  12. Glacial Outwash Stream

  13. Glacial Outwash Stream

  14. Glacial Landforms • Material deposited by glaciers is called drift • Till is deposited directly from glacier • Outwash is deposited by meltwater • In summer, meltwater carried along “rock flour sediments • In winter these were blown by wind • Left thick beds of loess downwind from major river valleys

  15. Glacial Drift

  16. Till that has melted out from the dark striped basal ice layer.

  17. Glacial Till – North Shore L. Superior

  18. Outwash plain and braided streams Outwash plain

  19. Outwashsediments

  20. Till exposure (dark tan) located above outwash sediments (light tan)

  21. Glacial Grooves on Kelleys Island, Ohio

  22. Glacial Striations on Canadian Shield Bedrock

  23. Large Glacial Erratic

  24. Large Glacial Erratic

  25. Glacial Landforms • Rock, gravel, sand, and silt left behind by melting glaciers formed mounds, ridges, and thick windblown deposits. • Moraines mark re-advances of glacier and when glacier stalled as it retreated • Accumulated drift is pushed into higher mounds by ice

  26. Glacial Landforms • End Moraines — During periods when the rate of ice advance nearly equaled that of melting, huge mounds of sand and gravel piled up in curved ridges along the glacier's edge.

  27. EndMoraine Ground Moraine

  28. End Moraines

  29. Valparaiso morainic system Marseilles morainic system The end moraines from the Wisconsin glaciation can be seen in Northeastern Illinois.

  30. Illinois Moraines

  31. Glacial Landforms • Ground Moraines - Ground moraines are formed as till is deposited directly beneath a glacier; between the ice and the underlying rock. • Ground moraines arelocated behind end moraines. • Form gently rolling to flat countryside.

  32. EndMoraine Ground Moraine

  33. Ground Moraine

  34. Ground Moraine

  35. Ground Moraine with Kettles

  36. Moraines • End moraines - western suburbs of Chicago • Form at melting end of glacier as till piles up • Belts of rolling or rugged hills with intervening swales, swamps and lakes • Ground moraines - DeKalb county • Form as ice front retreats and leaves a flatter deposit • Gently undulating lands

  37. EndMoraine Ground Moraine

  38. Moraines • Recessional moraines are formed when the ice stands still and melts.

  39. Recessional Moraines

  40. Moraines • Push Moraine - A ridge or pile of unstratified glacial sediment that is formed in front of the ice margin by the terminus of an advancing glacier, bulldozing sediment in its path.

  41. Kettles • Kettles — Depressions formed when ice broke into chunks that became buried in sediment. • When the ice block melted, it left a depression, which sometimes filled with water to form kettle lakes. • Kettle lakes are common in northern and central Illinois.

  42. Ice Block/Kettle Hole Lakes • Kettle Hole Lakes • These are usually deep lakes • Many still have water • Steep sides • Most Great Lakes region lakes are kettle hole lakes • Minnesota = Land of 10,000 Lakes • Volo Bog formed in a kettle

  43. Volo Bog

  44. Iceland – Kettle forming with ice block still in place.

  45. Kettle within Morainal Ridges

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