The Nature Of The Barrier Islands

The current set of barrier islands known as the Outer Banks are only one is a series of similar landforms that have existed along the North Carolina coast in the past two million years. In all, sixteen other sets of barrier islands have moved across the ocean to the mainland shore as, far to the north, glaciers ebbed and flowed across the northern latitudes. Most of these earlier landforms are gone now, absorbed into the low-lying mainland or under the rising sea. But remnants do remain. Lower Currituck county near Powell's Point and Roanoke Island are parts of earlier barrier island chains. A line connecting the two is visible on aerial maps, cut in two by Albemarle Sound, the flooded mouth of the Albemarle River, which flowed through the area during the last Ice Age.

There's other evidence of island migration. All along the ocean beaches of the Outer Banks, oysters -- animals that only live in the brackish waters of the sound -- wash up among the other shells in the surf line. The oyster shells are the remains of animals that lived in the same spot when the island was further to the east and the oysters were alive on the sound floor. Covered with sand carried by ocean overwash, the oysters were slowly buried as the island moved over them. As the island continues sliding slowly towards the south and west, the oysters are revealed. Recent estimates say the average age of the oyster shells found on the beaches of the Outer Banks is about eight thousand years old.