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Glacial legacies

Northeast Ohio was shaped by mountains of ice, and the impacts on land, water and plant communities linger today.

Glacial evidence<br />The Glacial Grooves, a National Natural Landmark site on Kelleys Island, are the finest example of glacial scouring/scoring in North America and probably the world. The grooves were scoured into the soft limestone of western Ohio by rocks and boulders pushed under the weight of the last glacial ice sheet. (Photo by JM Semroc)Striations<br />While the Glacial Grooves are the most impressive evidence of glacial scouring on Kellys Island, ice sheets also grouged out smaller striations in the bedrock. (Photo by JM Semroc)Boulders left behind<br />Rocks of different size and composition than surrounding rocks, like these boulders on a beach at Kellys Island, were moved and deposited by glaciers. (Photo by JM Semroc)Glacial erratic<br />It might have been placed by a landscaper, but chances are this unusual boulder is a glacial erratic, a boulder moved to Ohio by glaciers thousands of years ago. (Photo by JM Semroc)Kettle lake<br />Punderson Lake in Geauga County, Ohio's largest kettle hole lake, was formed when a block of ice broke off a retreating glacier and made a depression that filled with meltwater.Kames<br />This hummocky landscape of kames in Summit County was formed by sediment deposits from melting glaciers. Kames and kettle hole lakes are often found together in a kettle and kame topography.
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Starting about 300,000 years ago, Northeast Ohio was covered several times by massive sheets of glacial ice that expanded from the north. The most recent advance of ice, the Wisconsinan, arrived from Canada about 24,000 years ago and lasted until about 14,000 years ago. 

The ice sheets may have been a mile thick over the Erie basin, and they extended over northern, central and western portions of Ohio. They bulldozed the land and blanketed it with a layer of glacial deposits—rocks, sand, silt and clay that had been scraped up by the ice on its way southward. This glacial topography is well preserved today because, from a geological perspective, so little time has passed for erosion and weathering to occur.

The glaciers changed the course of rivers and shaped Lake Erie. They also changed the ecology of Northeast Ohio, bringing plants of the northern boreal forest—spruce, fir, tamarack, cedar, hemlock—to this region. When the last glacier retreated and the climate warmed, species quickly migrated from the south and established the deciduous forest we see today.

These great transformations occured just a few thousand years ago. Thus, on the surface we have a very young landscape. 

Glacial resources

Ohioans have made great use of resources deposited or created by the glaciers, including:

  • Rich agricultural soils
  • Surface waterways and groundwater stored in aquifers of glacial sediments
  • Sand and gravel for construction
  • Peat for use as a mulch and soil conditioner
  • Clays for making bricks and pottery

For more on glacial history, see "The Ice Age in Ohio" by Michael C. Hansen of the Ohio Division of Geological Survey.

 

 

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