You’re in the driver’s seat when it comes to seeing Ohio’s geology

OHIO OUTDOOR NOTEBOOK
By Laura Jones, Ohio Department of Natural Resources
Winter 2005

You’re in the driver’s seat when it comes to seeing Ohio’s geology

As we make our daily drives up, down and across Ohio’s highways, it’s easy to become oblivious to the scenery around us. Which is a shame, because many of the natural roadside features we zip past every day provide a window through which we can view millions of years of geologic history.

For example, many of the hills lining the horizon in western Ohio are likely to be vestiges of Ice Age glaciers, while the seemingly ordinary rocky slopes exposed alongside our highways are, in fact, cross sections of an ancient sea bed, chock full of long-ago marine fossils. And there’s no better time than now to begin looking for these formations, while leaves are still off the trees.

The land we call the Buckeye State has lived many different lives, according to Dennis Hull, a geologist with the Ohio Department of Natural Resources. “Several hundred million years ago, this area we now know as Ohio was located near the equator, and from time-to-time was submerged under a shallow tropical sea,” he explains. “As the earth’s temperature cooled 2 million years ago, glaciers repeatedly moved southward out of Canada and into much of Ohio. Today, we see evidence of these ancient events in a variety of ways, from the different layers of stone to the glacially sculpted contours of the earth.”

With the settlement of our state, hillsides were often cut through to create transportation routes. Today, road cuts along Interstate 77 between Marietta and Cleveland reflect remnants of Ohio’s long past tropical days. Fossil-filled shale, deep coal beds and marine limestone are natural records of the last 450 million years of geologic history.

Sandstones – rocks made of sand grains – were originally deposited on the beds of ancient streams and shallow seas, millions of years ago. On either side of I-77, just north of mile marker 40 and before the town of Byesville, are large, undulating sandstones believed to be deposits of an offshore sand bar that developed in the ancient sea.

Drivers heading south from Columbus to Portsmouth on U.S. Route 23 cross a boundary into a part of Ohio untouched by glacial ice – the difference is instantly noticeable. Flat stretches of road and glacially-leveled countryside are now met by hills that seem to suddenly rise from the earth.

On Rout 23, from the I-270 outer belt in Columbus to St. Joseph Cemetery in Lockbourne, glacial deposits known as “kames” can be seen. These cone-shaped hills are made up of sand and gravel deposited by meltwater of Ohio’s last retreating glacier some 14,000 years ago. Farther south, just below Piketon on the east side of the highway, is a broad, hilly area that is an ancient valley through which flowed the prehistoric Teays River.

Those commuting on Interstate 75 through northwestern Ohio would be correct to assume it is the flattest terrain in the state, courtesy of glacial ice and sediments deposited on the bottom of the Ice Age Lake Maumee – an ancestor of modern Lake Erie. Once covered by a great swamp, today evidence of ancient beach ridges and sand dunes along the shoreline of Lake Erie are the most prominent landforms in the region. When the area was a swamp, these ridges and dunes were the only dry ground to be found.

Interstate 70 runs through the heart of western Ohio, which was visited by Ice Age glaciers at least three times during the past 2 million years. In addition to depositing a blanket of finely ground rock over the land, these glaciers blocked and diverted streams.

From our cars, the most visible evidence of this icy era can be seen in the gently rolling or nearly level plains that follow on either side of the highway, such as those near Dayton. Geologists refer to these inconspicuous deposits as ground moraines, which formed at the base of melting glaciers. Mainly made of clay, silt and sand, ground moraines also can contain rocks from pebble to boulder-size.

In Montgomery County, just east of Ohio Route 202, travelers on I-70 can see an interesting glacial feature known as a boulder belt. These formations feature unusually large rounded boulders that were transported by glaciers from rock formations in Canada. Many of these giant stones were cleared from fields decades ago by local farmers and placed in fencerows where the boulders can still be seen today.

Brochures on driving guides to Ohio’s geology as well as other educational materials are available through the ODNR Division of Geological Survey by calling 614-265-6576 or visiting ohiodnr.com

Watch time fly by the next time you’re in the car. Just look out your window and see Ohio’s geologic history written in the rocks and land you pass every day.

Where to See Ohio's Geology