Kettle lakes legacy of Ice Age that visited Ohio around 20,000 years ago

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COLUMBUS (WCMH) — About 20,000 years ago, much of central and all of northwestern Ohio were under a blanket of ice several thousand feet thick (Laurentide Ice Sheet).

The ancient Ohio landscape resembled today’s Greenland Ice Sheet, and the climate would be classified as a tundra, with long, cold and stormy winters followed by short summers.

Here is video of the Russell Glacier, from Ohio State’s Glacial Dynamics Research Group at the Byrd Polar and Climate Research Center.

The ice in northern and western Ohio began to retreat about 17,000 years ago as the weather warmed, particularly in the spring and summer months. The glaciers scraped the surface and dumped sediment (small rocks, gravel, sand, soil) on the front and sides of the ice sheet that piled as unconsolidated glacial till, forming hills and low ridges.

On the margin (terminus), the glaciers randomly deposited boulders (erratics). Meltwater streams carried a fine, stratified mixture of sand, gravel, silt and clay. Blocks of ice broke off and became mired in the softer earth, melting in place and leaving a depression that filled with water and covered by sediment. Rainwater continued to fill the “kettles” after the ice disappeared, leaving behind marshes and swamps teeming with diverse biology.

Pickerington Ponds Metro Park, which covers 1,608 acres on the southeast edge of Franklin County and the northwest corner of Fairfield County, offers a scenic view of a restored kettle lake. The wetlands are home to shore and land birds, deer, beaver and fox, and visited by migrating waterfowl. Birdwatchers have recorded more than 260 species of birds.

Andy Nash, a geologist with the Ohio Department of Resources (ODNR), Division of Geological Survey, compared the last Ice Age to the Greenland Ice Sheet.

“The ice sheet is thickest at the ice center near the center of the continent and spreads/thins towards the margins, as gravity pulls and moves ice outward. Ohio’s climate during the ice age would have been very different than today. On average the temperature would have been about 6° C (10° F) colder about 20,000 years ago,” Nash said.

“Natural changes in Earth’s orbital cycles around the sun created conditions where less energy from the sun was able to heat the Earth,” Nash said. “During this time glaciers and ice sheets were able to grow to such large sizes because of the colder and longer winters created by Earth’s orbit around the sun (Milankovitch cycles).”

Nash explained that geologists have verified past temperature by studying natural archives of climatic data buried in ice cores drilled deep into glaciers and analyzed in a laboratory. “Air bubbles trapped in miles this glacial ice, speleothems growing in caves, and even tree rings from trees that are thousands are years old serve as proxy records for what the atmospheric conditions would have been like in the past,” said Nash.

This NASA link provides a description of the paleoclimate: https://earthobservatory.nasa.gov/features/GlobalWarming/page3.php#:~:text=As%20the%20Earth%20moved%20out,ice%2Dage%2Drecovery%20warming.

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