By John Paul Lilly
Associate Professor Emeritus, Dept Soil Science
North Carolina State University
Washington County is very flat and not very high above sea level. The county is, in fact, a seabed that is temporarily not covered by the ocean. In the past, the county has been covered and uncovered by the ocean many times. Some of the rise and fall in sea level has been due to changes in the ocean volume, but most has been caused by continental glaciers, vast ice sheets a mile or more thick that covered much of North America. For millions of years, the earth has undergone cycles of glacier formation followed by periods of glacier melting. Sea level becomes lower when the glaciers form and sea level rises when the glaciers melt.

In eastern North Carolina, the western advance of the sea during each melting of the glaciers is marked by a sand ridge called a "scarp". The land to the east of each scarp is called a "terrace". The scarps and terraces occur at lower elevations and are younger from west to east. Most of Washington County is on the youngest marine terrace, called the Pamlico Terrace. The western boundary of the Pamlico Terrace is the Suffolk Scarp, a sand ridge complex that extends from Suffolk, Virginia, through Washington County, to near Morehead City. There are two scarps in Washington County. The older scarp is called the Walterboro Scarp. Long Ridge Road follows the Walterboro Scarp sand ridge from Plymouth to Pinetown. The elevation at the foot of this scarp is about 40 feet above sea level, and the ocean most likely reached here several hundred thousand years ago.

The Suffolk Scarp is the youngest scarp in the county. Highway 32 follows it from Plymouth to Acre Station. The elevation at the foot of the Suffolk Scarp is about 20 feet above sea level. During the last warming period between glaciers, about 70,000 years ago, the oceanfront was at the Suffolk Scarp. The Outer Banks ran through Washington County 70,000 years ago. At that time, Van Swamp was a back-dune flats area behind the barrier islands. There was an inlet where Van Swamp drains across highway 32. The climate was warm and the vegetation was tropical.

While the ocean was at the Suffolk Scarp, the glaciers again began to grow and there was another ice age (called the Wisconsin glacial age) which reached its peak about 18,000 years ago. Continental glaciers covered North America as far south as Pennsylvania. Sea level fell as water was tied up in the glaciers, and present-day Washington County found itself 400 feet above sea level. The ocean shoreline was many miles further east of its present location. The Roanoke River ran to the sea through a broad river valley that is now Albemarle Sound, and most of Pamlico Sound was dry land. The climate was cold and the vegetation was similar to present-day Canada. Strange animals such as the mammoth, musk ox, and mastodon (Beyer, 1991) roamed the area. Again the glaciers began to melt and sea level began to rise. The coastline has been migrating westward ever since. Rising sea level has filled the Roanoke River valley with water and formed the Albemarle Sound.

Sea level is still rising, causing shoreline erosion along the sound and river and increasing drainage problems in the eastern part of the county. Sea level is now estimated to be rising about one foot each 50-100 years. Counties to the east of us are struggling to cope with saltwater intrusion and poor drainage. In Washington County, the town of Creswell and some farmland along the Scuppernong River require pump-assisted drainage. Unless the melting of the glaciers stops, Washington County will one day be reclaimed by the sea.