The terrain of Cuyahoga Valley National Park is diverse and rugged. Ravines with exposed rock, waterfalls, and rock ledges give texture to the valley. Ice decorates the rocks in winter, adding interest. This article introduces the rocks and where to enjoy them.
Local bedrock is made up of layers of sedimentary rocks, formed from materials left by ancient waterways. The oldest layers sit at the bottom, with successively younger layers on top. In some places in the world, mountain building has scrambled layers of rock. Here the layers remain in the order they were laid down millions of years ago. Research by geologists date the valley’s rocks to the Paleozoic Era. They range in age from 410 to 286 million years old. This is the era when fish, amphibians, and reptiles appeared, but dinosaurs had not yet entered the scene.
In imagining the past, it is tempting to use our understanding of the land today. Two factors are somewhat similar. This area was inland on a continent, and the Appalachian Mountains were relatively nearby. However, major differences existed. Imagine time-lapse photography of the earth across time. Continents do not stay in one place. They continually move around, merge together, break apart, and change shape. During the Paleozoic, present day Ohio sat much closer to the equator. The Appalachians were forming through a series of mountain building episodes. Today, the Appalachians are old mountains and have been rounded by millions of years of erosion. The young Appalachians of the past would have been much taller and more rugged.
In your imagined time-lapse photography of the past, also imagine inland seas expanding and shrinking over the continent. Oceans occur between continents. Inland seas cover continents. One of the challenges in imagining inland seas is that there aren’t many today. The Hudson Bay in Canada is the largest. Avoid using the Great Lakes to imagine these ancient seas. The Great Lakes are freshwater products of recent glaciers. The ancient seas were saltwater results of high ocean levels.
The inland seas and growing Appalachian Mountains influenced the valley’s exposed bedrock. The bottom, oldest layers are shales. They are soft rocks formed from the mud and silt on the floor of the inland seas. Today, waterfalls such as Brandywine Falls are places to view shale. Their fine layering gives waterfalls a bridal veil appearance. Shales of different ages exist in the park and region. Describing their differences is outside the scope of the article. However, look for variation in the shales you encounter. Darker shales, for example, had more organic material mixed in with the mud and silt.
Berea Sandstone sits on top of the shales. You can often see it as the harder layer that forms the protective cap at the top of many waterfalls in the area, including Brandywine Falls. Its fine grains of quartz sand are apparent on closer look. When these sands were deposited, this area was closer to the shoreline of an ancient sea. A river flowing from the growing Appalachians into the sea dropped the sand here.
Sharon Conglomerate is the youngest bedrock in the park. You’ll find it along the Ledges Trail, as well as at other named ledges in Northeastern Ohio. A close look will show you that it contains sand and pebbles. High energy streams flowed from the rising Appalachian Mountains, carrying them here. Instead of having a main channel that meanders in a sinuous pattern like the Cuyahoga River, they would have had a network of diverging and converging shallow channels that resembled a braid.
The National Park Service is a preservation agency. At Cuyahoga Valley National Park, we help people access and enjoy natural features like the rock outcroppings. We also work to protect them. We ask that visitors help by having a low-impact visit. Look closely at the rocks and discover their details, but please resist the temptation to break apart the rocks. There is plenty to enjoy on their surfaces.
Brandywine Falls is located at 8176 Brandywine Road in Sagamore Hills. Access the Ledges from the Ledges Trailhead, located at 405 Truxell Road in Peninsula.
Vasarhelyi is Chief of Interpretation, Education & Visitor Services for Cuyahoga Valley National Park.