The history of the earth is written in the rocks. In Ohio, nearly 500 million years of time are recorded in our bedrocks, reflecting the coming of inland seas, the upheaval of mountain ranges and the birth and death of vast swamps. By reading these rocks, geologists can piece together our ancient history. No matter where you walk, geology in some form awaits discovery. In this park, though, its influence and impact is obvious.
Ohio's bedrock is all sedimentary. It was laid down upon the floors of the ancient oceans which periodically inundated the state. Conditions changed over the eons in these waters, dictating the different types of sediments that we now see bedrock. Compaction, over subsequent millions of years, compressed the materials into rock.
Ohio's general bedrock types include sandstone, shale and limestone. The first two are formed from sediments washing into the sea from nearby land masses. Sandstones and conglomerates represent periods when coarse-grained and larger materials were introduced from relatively swift flowing rivers. Shales are formed from finer sediments such as mud. Limestone usually represents an area where the sea was deeper and clearer. Lime precipitates out of the water, accumulating as a mud with many shell fragments on the sea floor.
As seas receded and the resultant lowlands grew lush with swamp vegetation, the coal measures of eastern Ohio were formed. As seas alternately flooded and withdrew from the region, salt waters killed the vegetation and brought in the sand and mud seen today as layers of coal interspersed with sandstone and shale.
Ohio's sedimentary rocks form layers with the oldest strata at the bottom. These layers dip slightly to the southeast and northwest in those corners of the state while they are fairly level from Cincinnati north to Toledo. This dome or arch is a feature of the bedrock itself while surface erosion has cut evenly across the state. Therefore, different layers are exposed across Ohio with the oldest at the center of the arch and the younger layers in the southeast and northwest.
The Little Beaver Creek cuts down through 300 million year old bedrock of the Pennsylvania period. During this time, the seas rose and fell so deposits vary greatly in their composition, including both marine and swamp sediments. South of here lies Ohio's wealth in coal.
The Pleistocene Ice Age included several major advances of glacial ice. In most of Ohio, older deposits lay buried beneath those of the last advance known as the Wisconsinan. Columbiana county and this area are interesting, however, in that a fringe of older Illinoian deposits extends southward beyond those of the Wisconsinan.
South of the park, the ridges roll toward the horizon in unending succession to the mountains. This park is part of the Appalachian plateau where the bedrock has been uplifted yet the layers still remain fairly level. Streams have cut deep valleys, but the more rugged terrain is found closer to the mountains where the actual bedrock strata have been twisted and folded. It is awesome to think of the ancient mountains that have been thrust up and worn down by erosion. Their remains deposited in a prehistoric sea and are preserved here as sandstone and shales.