At the River Knobs, the quartzite layer has been "verticalized" by geological forces during the formation of the Appalachians some 230 million years ago.

The River Knobs trace the western wall of this arch, or anticline, where the Tuscarora was turned a full 90 degrees from horizontal to vertical.

The tough quartzite of the western walls resisted this process, leaving the soaring "fins" - narrow vertical plates of exposed rock.

About 2 miles (3.2 km) east, along the top of North Fork Mountain, the horizontal strata of the far slope of the Tuscarora anticline are also visible.

The reason for this is that, during the rise of the Appalachians, the same forces which formed the anticline caused the Tuscarora to fault or rupture, with the upper layer sliding over and overlapping the lower.