The massive grooves cut into rock on Kelleys Island at least 17,000 years ago by giant glaciers that carved out the Great Lakes region are believed to be the largest preserved glacial grooves in the world.
Each year, more than 100,000 people visit the
Glacial Grooves Geological Preserve on Kelleys Island to witness the evidence of the glaciers' sheer power to scour the limestone of the island and see the ancient fossil embedded in the rock.
Although the site is probably the best-known and largest example of glacial grooves in the Lake Erie region, there are other sites around the Lake Erie islands and some on the mainland that have glacial grooves and striations, or scratches in the rock, left from the Ice Age.
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Kristina SmithGibraltar Island glacial grooves“Small grooves and glacial striations can be found all over the vicinity of Lake Erie,” says J.D. Stucker, Assistant Chief of the
Ohio Geological Survey, which is part of the
Ohio Department of Natural Resources. “The limestone of the area is hard enough to resist long-term erosion but soft enough that it was able to be scraped and carved. The whole area is far enough north that glacial ice from the north was still thick/heavy enough to form these features.”
Many of the notable glacial grooves and striations in this region have the same direction or orientation, so they likely were formed around the same time, although it’s hard to know precisely.
The glacial ice that formed these grooves and striations may have been 3,000 to 5,000 feet thick. In addition to the scraping of the mass of ice, meltwater from the glaciers also likely helped shape and cut the rock.
“You don’t see it initially when you’re looking at the grooves, but the thing that gets the biggest wow when we’re talking to people is how much ice and water it took to carve that much rock,” Stucker says.
The islands and mainland each have places where this can be seen.
Kelleys Island Glacial Grooves Preserve
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Kristina SmithMiddle Bass Island glacial groovesThe
largest example of grooves received a $2.7 million upgrade that was unveiled in 2023 and now has handicapped-accessible walkways, observation decks and interpretive signs.
Carbon-dating shows the grooves are likely 17,000 to 25,000 years old. Embedded inside them are fossils of marine animals that lived 400 million years ago and were deposited into mud and fossilized when the rock, which is Columbus limestone, was being formed at that time. The fossils became exposed when the glaciers cut the grooves into the rock.
“Another interesting fact is that there are grooves within grooves at
Kelleys Island,” Stucker says. “Not only is there one large channel, but the smaller channels each contain even smaller grooves or striations. These features have helped scientists determine that it wasn’t only the scraping, erosive weight of the glacial ice that formed the grooves, but also high-pressure meltwater beneath the glacier.”
Stone quarry workers discovered the grooves in the early 1870s. There was a much larger section than what is preserved today that was destroyed. But the quarry operation saved the nearly 400-foot that is open to the public today.
“They recognized this was something special and had the foresight to preserve the portion that they did,” Stucker says.
The Kelleys Island Lime and Transport Company and
Cleveland Museum of Natural History donated the grooves to the state of Ohio in 1932, he says. They remained covered until the 1970s, when the
Ohio History Connection (then known as the Ohio Historical Society) and
Ohio State University began to expose them.
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Kristina SmithMiddle Bass Island fossilThe glacial grooves are located at 739 Division St., Kelleys Island. The island is accessible by ferry boats, the Kelleys Island Ferry Boat Line and the Jet Express.
East Harbor State Park, Marblehead
In the campground area of
East Harbor State Park, there is a rock area with small grooves and glacial striations.
“Right now, those grooves are at the surfaces, but when they were being formed, they might have been under thousands of feet of ice,” Stucker says. “You think about how much that really is and you kind of put that in perspective, imagine standing on the grooves and you have 3,500 hundred feet of ice above you.”
In addition to seeing the grooves, the park nature center has a display with educational information regarding them.
“East Harbor is so close so if you’re in the area and you’re interested in geology, East Harbor is definitely worth the trip,” he says.
East Harbor State Park is located at 1169 N. Buck Road, Lakeside-Marblehead.
Middle Bass Island State Park
In recent years, the glacial grooves at
Middle Bass Island State Park had been under water. This spring, the water receded, exposing the grooves. Fossils can be seen embedded in the rock.
The grooves are located between the
Lonz Winery pavilion,
Lonz Mansion and Middle Bass State Park Marina.
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Kristina SmithMiddle Bass Island glacial groovesMiddle Bass Island State Park is next to the ferry dock on Middle Bass Island. It is accessible by the Miller Boat Line and Sonny-S Boat Line.
South Bass Island State Park
These grooves are located in
South Bass Island State Park, home of popular tourist destination the village of Put-in-Bay.
South Bass Island/Put-in-Bay is accessible via the Miller Boat Line and Jet Express ferry.
Gibraltar Island
A small area of grooves can be seen at the tip of tiny
Gibraltar Island, which is part of Ohio State University and home of the
Franz Theodore Stone Laboratory. The island is located in Put-in-Bay Harbor just off South Bass Island and is open for tours on certain days of the week. While there, visitors can tour Stone Lab and learn about the research and education done there, as well as interesting historical features.
Gibraltar Island can be accessed by going to Put-in-Bay via the Miller Boat Line or Jet Express ferry and then taking a water taxi from The Boardwalk to the island.
Permission is required to visit the island, or visitors can attend open houses available on certain days.
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Kristina SmithMiddle Bass Island fossilCastalia Quarry MetroPark
Like the Kelleys Island grooves,
Castalia Quarry Metropark’s glacial grooves were found during stone quarrying. In 1965, the quarrying work ended, and today the area is one of the parks in the Erie Metroparks system. Fossils and glacial grooves, many still buried, can be seen at the park.
Castalia Quarry MetroPark is located at 8404 State Route 101, Castalia.
Marblehead Lighthouse State Park
This state park is known for its historic lighthouse, but the rock around it shows glacial striations and fossils, as well.
Marblehead Lighthouse State Park is located at 110 Lighthouse Drive, Marblehead.
Blue Creek Metropark
Housed in a former stone quarry on the edge of the Oak Openings region, Blue Creek Metropark is part of
Metroparks Toledo. This park includes glacial grooves, a quarry pond, native plant nursery and more.
Blue Creek Metropark is located at 7035 Providence St., Whitehouse.