Remainders of a Vast Inland Sea

During the Ordovician Period (500-440 million years ago), the Blue Ridge was first rising as a mountain chain. Sands and mud were washed off the mountains into a vast inland sea that existed to the west. This sea was as near as what is now Damascus, Virginia.

There was a deep trench at the edge of the mountains where life could not exist on the sea floor because of a lack of oxygen. The most common fossils found in the trench's mud's are organic skeletons of floating animals called grapholites. These appear as thin, "V" shaped lines on the slab.

West of the trench the sea floor was shallower, and shelled animals like brachiopods lived on the bottom and, in some places, formed reefs. Corals also lived in the shallow waters west of the Blue Ridge. About 320 million years ago, the continents of Africa and North America collided, pushing up the Appalachians to the height of the Himalayas. The huge volume of sands and mud that were eroded off the mountains as a result of this collision displaced the inland sea westward and it gradually disappeared.