Centre County is located in the Appalachian Plateaus and the Valley and Ridge physiographic provinces. The provinces are separated by the Allegheny Front, which is just north of the northeast-southwest trending Bald Eagle Valley. The Appalachian Plateaus in the northwestern third of the county, are subdivided into the Allegheny High Plateau, Pittsburgh Plateau, and Allegheny Mountain sections. The Appalachian Mountain section, in the eastern and southern parts of the county, is part of the Valley and Ridge province. Each province has distinct and different topographic and geologic features that have influenced soil formation and accepted land use in Centre County.

Geology
The bedrock geology of the Appalachian Plateaus is represented by Devonian, Mississippian, and Pennsylvanian rocks consisting primarily of sandstone, shale, limestone, and conglomerate formations. In the northern part of the county, coal is present in the Allegheny and Pottsville Group of Pennsylvanian age.

The formation of the Appalachian Plateaus began after Paleozoic marine and nonmarine deposition. During the late Paleozoic Era regional uplift from the southeast caused this area to rise uniformly, without much disturbance, to bedrock altitudes. The topography of today is a result of dissection of this plateau by streams that gave the areas the appearance of rolling hills. Several unnamed hills reach elevations of about 2,500 feet in the southeast corner of the county. The bedrock geology of the Valley and Ridge province is represented by Cambrian, Ordovician, Silurian, and Devonian rocks consisting primarily of dolomite, limestone, sandstone, quartzite, conglomerate, and shale formations.

The Paleozoic beds of the Valley and Ridge province underwent lateral compression from the southeast that formed many deeply folded anticlinal and synclinal features. The final stage of erosion followed the last period of compressional uplift. Different bedrock lithology and exposure in this complex network of folds has resulted in the development of broad and narrow valleys and ridges. The ridges formed because the sandstone and quartzite formations capping the ridges resist erosion while the valleys formed in less resistant limestone and dolomite. Many of the valleys are karst limestone valleys where caverns, sinkholes, and poorly defined drainage are prominent. Both valleys and ridges in the county are oriented northeast-southwest. Some of the high ridges in the county are Mount Nittany (2,345 feet) and Tussey Mountain (2,407 feet). In order of decreasing value, the mineral resources in Centre County are lime, stone, coal, sand and gravel, and clay (11). Centre County is the leading producer of lime (quicklime and hydrated lime) in the state. Stone production ranks high and represents about 5 percent of the total value of Pennsylvania's stone production. Bituminous coal mining ranks less than 1 percent of the total bituminous coal mining in the state.

Drainage
Centre County lies in the Susquehanna River basin. About three-quarters of the county lies in the West Branch of the Susquehanna River drainage area. The major tributaries contributing to the West Branch are the northeast-flowing Moshannon and Beech Creeks. The remaining part of the county is drained by Spruce Creek, which is in the southwest corner of the county and is a tributary of the Juniata River, and Penns Creek, which is in the southeast corner and flows east into the Susquehanna River.

3/4/99