Geological History of Cuyahoga Valley National Park
Cuyahoga Valley National Park is a very special place . . . unlike many of the other national parks in the United States, this is not a forbidden wilderness, it’s not somewhere in the middle of nowhere where you can pit your wits against nature and hike without seeing a living soul for days on end, for many people it’s close, it’s comfortable, it’s welcoming . . . it’s “just down the street . . . at the end of the sidewalk”. It’s so accessible yet offers an oasis of tranquility so close to it’s urban surroundings.
Situated between Cleveland and Akron, the Cuyahoga Valley National Park offers 32,000 glorious and peaceful acres, stretching along 22 miles of the Cuyahoga River, so what’s the story?
The Cuyahoga River Valley has been sculpted over time by weather, water, ice and shifting continents. It’s really the latest chapter in a very long story, the story of how Ohio, well, northeast Ohio, came to be. It’s taken millions of years of rushing rivers, soaking seas, glaciers forming and retreating to shape the wonderful landscape filled with waterfalls, gorges, rock ledges, as well as, of course the snaking Cuyahoga River. This river was named centuries ago by the native Indians . . . . “ka-ih-ogh-ha” – or “crooked” . . . not a bad description is it?
Cuyahoga Valley Rocks
Yes, well, I know it does, it’s a great place to visit, but that isn’t really what I meant, I meant, let’s take a closer look at the rocks you can find (if you know where to look) in the Cuyahoga Valley, and what they can tell us about the geological history of the area.
The thing you’ve gotta’ remember about rocks, is that the deeper they are, the older they are. Some great clues about rocks and the geological history of Cuyahoga Valley National Park can be found in some of the prettiest and most popular sites, places like Tinker’s Creek Gorge and Brandywine Falls. In these areas there are rocks in plain sight which were once (not so long ago, geologically speaking) buried far beneath the surface. The rushing water and the relentless weather has gradually eroded the rocks leaving the layers exposed for us to see very easily. Remember that rock layers grow from the bottom up (a bit like my cousin Gillian actually, her bottom seemed to grow rather large before the rest of her caught up), so the buried layers of rock are very old, but the stuff you’re walking on is relatively young. Bedrock gets older as it gets deeper. Some of the bedrock in Cuyahoga Valley National Park which is now visible is around 400 million years old . . . that’s older than dinosaurs, it’s older than any sorts of reptiles, it’s definitely older than my old English professor.
A Tale of Long, Long Ago
What is now northeast Ohio was once covered by an ancient sea, long, long ago, around 400 million years ago in fact. There were big fish, sharks, you name it, they swam there, and lots of mud, silt and sediments settled on the sea floor. Eventually the weight of these stacked sediment layers squeezed them and crushed them, transforming them into shale, a dark, gray rock. You can find fossils from these ancient sea creatures in the shale layers at Cuyahoga Valley National Park.
After the shale came the sandstone, which is why it lies just above the shale layers. The sandstone was made from the billions of grains of sand which were deposited along the deltas, this sandstone is a common bedrock particularly in the uplands of the valley.
Next comes the youngest of the bedrocks, conglomerate which is made up of loads of different types of sedimentary rock all stuck together, pebbles and sand forming one layer of bedrock, 300 million year old bedrock. This is the most showy of all the rocks of Cuyahoga Valley National Park, the giant blocks of orange and yellow which round, worn holes like honeycomb. These holes are formed by the water as it filters into the rock loosening the pebbles which are eventually washed out.
Okay, so we’ve gathered that there are some pretty old rocks at Cuyahoga Valley National Park, 400 million years old, 350 million years old, but there isn’t much evidence of younger rocks, those younger than 50 million years old for example. There are no rocks from the days when dinosaurs roamed the area, for example . . . that doesn’t mean that they were never there, bit just means that they have been eroded and have now disappeared. The ancient river which carved out the original Cuyahoga Valley washed them away before the Ice Age even arrived, around 2 million years ago.
During the Ice Age the great glaciers bull dozed across the land a minimum of four times in northeastern Ohio, before the last Ice Age ended around 10,000 years ago. These giant moving ice mountains pushed up tons of rock, clay, sand, everything went before it like a giant bulldozer, burying the landscape and filling in those ancient valleys. The original Cuyahoga Valley was buried beneath sand, rock and clay.
As the glaciers melted, lakes were formed (Lake Erie, for example), in fact, Peninsula was once a great lake, around 50,000 years ago. Once the glaciers left the Cuyahoga Valley which we love and recognize to this day was formed, once it was freed from the giant ice sheets the Cuyahoga River was able to really get to work re-carving old valleys and cutting through ancient bedrock forming many of the splendid waterfalls and amazing gorges which are such an important part of the landscape in Cuyahoga Valley National Park.