The Interior Low Plateaus exist at the southeastern extent of the Central Lowlands, the boundary occurring where the maximum extent of Pleistocene glaciers reached. The Interior Low Plateaus are almost completely horizontal beds of Paleozoic sandstone, shale, and limestone. The entire province is divided northeast-southwest by a fold axis known as the Cincinnati Arch. The area is also home to two structural domes that have been eroded to form basins lined with inward-facing cuestas.