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Geology and Geomorphology of The Great Lakes

Geology and Geomorphology of The Great Lakes. Cassandra Biette. Outline. Introduction Geologic History of the Region Fluvial and Glacial Interactions Post-Glacial and Modern Processes Affecting Great Lakes Shorelines. Introduction. Largest source of freshwater in the world

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Geology and Geomorphology of The Great Lakes

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  1. Geology and Geomorphology of The Great Lakes Cassandra Biette

  2. Outline • Introduction • Geologic History of the Region • Fluvial and Glacial Interactions • Post-Glacial and Modern Processes Affecting Great Lakes Shorelines

  3. Introduction • Largest source of freshwater in the world • Economic & Transportation for Midwestern cities

  4. Geologic History of the Region BEDROCK GEOLOGY • Lake bottom topography • Soft shale and sandstone allow for glacial scour • Sandstone bedding shows lake level fluctuations

  5. Geologic History of the Region RIFTING • Intersection of Midcontinent Rift and Grenville Front • Not tectonically active, but still weak

  6. Geologic History of the Region PRE-EXISTING BASINS • Concentric circles, depression • Scoured by glaciers into lakes

  7. Fluvial and Glacial Interactions GLATIATION: LAURENTIDE ICE SHEET • 6 Major phases • 5 lobes, interact with each other • Erosional (Niagara Falls) • Depositional (Sleeping Bear Dunes)

  8. Fluvial and Glacial Interactions • Current Lakes are determined by drainage pattern • Changes in drainages affect morphology of Lakes

  9. Fluvial and Glacial Interactions NIPPISSING HIGHS

  10. Fluvial and Glacial Interactions CHIPPEWA/STANLEY LOWS

  11. Fluvial and Glacial Interactions GLACIAL LAKE ALGONQUIN

  12. Post-Glacial and Modern Processes Affecting Great Lakes Shorelines UPLIFT AND TILTING • Affect on drainage patterns • Downcutting • Tilting: one area experiences more uplift than another

  13. Post-Glacial and Modern Processes Affecting Great Lakes Shorelines EOLIAN PROCESSES • Wind patterns and direction • Relict dunes show past shorelines

  14. Post-Glacial and Modern Processes Affecting Great Lakes Shorelines MASS WASTING • Bluff Recession: land slides on groundwater surface • Prominent during high water • Could be stopped by pumping out groundwater (not feasible) • 1-2 feet per year • Wave action, slump erosion • Freeze/thaw

  15. Summary • Fluvial processes: changing drainages • Laurentide Ice sheet: Ice dams that change morphology of lakes • Modern changes through erosion (mass wasting, dunes)

  16. Images www.bulletin.geoscienceworld.org (Grenville Front) www.kgs.ku.edu (Midcontinent Rift) www.niagarafallslive.com (Niagara Falls) www.geo.msu.edu, www.nps.gov (Sleeping Bear Dunes) www.picturedrocks.com (Pictured Rocks National Lakeshore) www.ontarioparks.com (Lake Superior Provincial Park)

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