From Ohio History Central
The surface of Ohio includes bedrock from two of the major North American regions. The eastern part of the state lies within the hilly, Appalachian region. The western part of the state is part of the flatter Central Lowlands. The ancient glaciers that bulldozed their way over approximately two-thirds of Ohio had a tremendous effect on the state's bedrock surface. Because of that, the state has five, distinct natural regions.
Glaiciated Appalachian Plateau
Soils in much of the Glaciated Appalachian Plateau region are low in richness, acidic and poorly drained. Limited areas with organic soils are more productive in agriculture. Unlike the unglaciated to the south, the terrain is characterized by smoothly rolling hills and broad, flat valleys.
Much of the Till Plains of western Ohio is characterized by soils that generally are deep and fertile. Drainage, however, is poor in some areas. Soils in the southern part of this area often are thin and can be less fertile. The more level ground promotes use of heavier agricultural equipment. Crops include corn and soybeans. Material dropped by glaciers in this region is as deep as 400 feet. In some places these deep beds of sand, gravel and small rocks support important sources of water. The most conspicuous area of glacial material is Campbell Hill in Logan County, the highest point in Ohio (1549 feet above sea level). Also in this region is the lowest point in the state (455 feet above sea level), which occurs along the banks of the Ohio River near Cincinnati.
Ohio's flattest lands are in the Lake Plains of the northwestern part of the state, and along the southern shore of Lake Erie. These plains, with their accompanying sandy beach ridges, were made by several large, glacial-age lakes in the area where Lake Erie is today. All of the soils in this region come from deposits laid down in the ancient lakes. Soils in the western portion of this region, particularly in the so-called "Black Swamp" area, are highly fertile but very poorly drained.
Unglaciated Appalachian Plateau
The Unglaciated Appalachian Plateau makes up most of southeastern Ohio. Soils in this area often are low in fertility and acidic. The hilly nature of the area results in many problems with erode, and limits the use of modern agricultural equipment.
The Lexington Plain is the other unglaciated area in Ohio. Unlike the Unglaciated Appalachian Plateau to the northeast, the more fertile soils of this region are based on limestone and shale. Nevertheless, as in the Unglaciated Plateau the hilly terrain leads to problems with erosion.
- Lafferty, Michael B., ed. Ohio's Natural Heritage. The Ohio Academy of Science, Columbus, 1979.