Region 3: Soils of the Inland Basin

The Inland Basin is the only area not extensively influenced by the numerous glacial advances. The region is geologically referred to as a basin because of its bedrock type, but geographically it is a plateau formed during mountain building to the east. This plateau (the major portion of which is known as the Allegheny Plateau) occupies most of western Pennsylvania, part of eastern Ohio, more than half of West Virginia, the western tip of Maryland, the upland southern portion of New York, and a marginal portion of southern Indiana and Illinois. The Allegheny Plateau has been greatly eroded by swift rivers and streams that have cut deep valleys, leaving behind steep hills as remnants of the former surface. For the most part, elevations range from about 370 to 760 meters (1200 to 2500 feet) above sea level. The valleys and gentler slopes of the Alleghenies are dotted with farms on which grain is grown and dairy and beef cattle are raised. The area is rich in bituminous coal, especially in Pennsylvania, West Virginia, and Ohio. There are deposits of petroleum and natural gas, and lumbering is also an important industry in this area. The plateau is divided into unglaciated and glaciated regions.

Unglaciated Allegheny Plateau

The Unglaciated Allegheny Plateau is located in an arc around southeastern Ohio that extends into western Pennsylvania and West Virginia. This area is a dissected plateau, characterized by sandstone, shale, and coal seams that are Mississippian through Permian in age. A good example of the dissected nature of this area, and a spectacular scenic location, is the Hocking Hills in southeast Ohio. This area is dominated by Inceptisols of suborder Ochrepeds (Figure 8.5). These soils have thin, light-colored surface horizons. The bedrock is mostly composed of shales, limestones, and sandstones that are Devonian through Permian in age but still have only thinly developed soils.

Glaciated Allegheny Plateau

The Glaciated Allegheny Plateau lies within the area covered by the last glacial maximum. As a result, this area of the Allegheny Plateau has lower relief and gentler slopes than does the relatively rugged Unglaciated Allegheny Plateau. In general, the glaciated portion lies to the north and west of the unglaciated portion, and it forms an arc from northeastern to southeastern Ohio. This area—only a few hundred square kilometers owing to the blockage that the steep relief of the mountains provides at the edge of the ice sheet—contains only old drift now buried by long periods of soil development. The dominant soil type of this area is an Alfisol of suborder Udalf.