More than 400 million years ago, a warm, shallow sea covered Ohio. Sand, rocks, silt, mud and minerals, collectively called sediments, made up the seafloor. Sea life including small, shelled animals lived in the water. As the shelled animals died and new sediments washed into the sea, the seafloor became layered — new sediments covering the old. Over time, the increasing mass of sediments compressed the deeper layers to form sedimentary rock.
There are two types of sedimentary rock that make up the bedrock in the park — dolomite from the Silurian Period and Columbus limestone from the Devonian Period. The dolomite is a thicker, stronger layer of rock.
Columbus limestone tells the story of the animals that lived on the ocean floor. In the example of limestone, look for fossils shaped like seashells, called brachiopods. They were one type of shelled animal that lived in the ancient sea.