The Buffalo Creek Watershed is located in the ridge and valley province of Pennsylvania which is characterized by folded, faulted and fractured sedimentary rocks. Buffalo Creek lies in a broad valley between folded ridges to the northwest and southeast, and flows mostly on easily-eroded rocks. The underlying geology has been found to have a dramatic impact on water quality. The North Branch and Spruce Run originate in rock that contains limestone and dolomite, which provide a natural buffering capacity to acid, but underlying rock at the Buffalo Creek headwaters is mostly sandstone, which does not. All three branches are subject to acid precipitation, but only in the headwaters of the main branch does the unbuffered acid cause a problem for fish and wildlife.