Glacial Grooves State Memorial
Deep Grooves Scoured into Limestone about 18,000 Years Ago

A mile-thick sheet of ice once covered the northern half of North America. It left behind a number of geologic relics, such as the hundreds of named erratics (huge stones found in isolation and that differ from the types of rocks that are native to the surrounding area), such as the Great White Rock of British Columbia, the many drumlins that form the hills of Seattle, and grooves in hard rock, formed where ice pulled stones across the landscape.

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Great White Rock near the shoreline at White Rock, British Columbia. (Photo by Hailey G. Pinto)

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Glacial Grooves State Memorial on Kelleys Island, Ohio. (Photos by James St. John)

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Among the deepest and widest glacial grooves found anywhere in the world are those on Kelleys Island along the southern shoreline of Lake Erie. These include troughs 400 feet long, 35 feet wide and up to ten feet deep.