The northwest third of Centre County lies in the Appalachian Plateaus physiographic province. The higher altitudes are underlain by the Conemaugh, Allegheny, and Pottsville Groups, which consist of sandstone, shale, and thin limestone and coal beds. The average yield of nondomestic wells in the Allegheny Group is 20 gpm (gallons per minute) and that in the Pottsville Group 100 gpm. Water from wells in these groups commonly has a high concentration of iron. Most of the rest of the Appalachian Plateaus province is underlain by the Burgoon Sandstone. The Burgoon yields soft water, and the average yield of nondomestic wells is 70 gpm.