As much as 35 billion tons of the lower grade coal called bituminous has been mined throughout the Appalachian Basin.  Several seams of the Pennsylvanian (307 Ma) Breathitt Formation are exposed along the huge roadcut here.  Coal formed during this period in swamp environments rich in vegetation and animal life which has led to the United States becoming an economic power on the back of its fossil fuels, particularly here in the Kentucky Coal Field.  Many fossils have been found in the deposits.