Atlantic-Gulf Coastal Plain:
Atlantic Coastal Plain

The Coastal Plain is the youngest of Virginia's physiographic provinces, its rocks having been deposited after the Atlantic Ocean began to form early in the Mesozoic. Sediments eroded from the Appalachian Highlands were deposited offshore and later consolidated into sedimentary rock. Uplift of the North American continent tilted these beds so that today they dip gently seaward.

Where the softer sedimentary rocks of the Coastal Plain abut the more resistant metamorphic rocks of the Piedmont, a low escarpment is visible on the landscape. (See geologic cross-section.) This is the Fall Line, so named because where rivers cross there are rapids or falls. On the Potomac a fairly broad "fall zone" extends from Great Falls downstream nearly to Alexandria. The falls were barriers to ocean-going vessels even in the Colonial Period and hence were to have a major influence on early European settlement patterns in Virginia.

The tilted beds of the Coastal Plain extend offshore some 50 to 75 miles to the edge of the North American continent. Distinction may thus be made between that part of the Coastal Plain that is submerged, the continental shelf, and that that is exposed above sea level, merely known as the coastal plain. The continental shelf reaches from sea level (0') to 600 feet below sea level. At that depth the the margin of the continent is abrupt and the "continental slope" plunges down to the ocean floor. The continental shelf has not always been submerged. During the ice ages of the Pleistocene sea level was lowered, exposing the shelf. Streams flowed across the shelf and carved their valleys into it. One such large valley became Chesapeake Bay when sea levels rose again and flooded the shelf.

The Coastal Plain proper extends from sea level inland to the Fall Line, where at about 200 feet above sea level it meets the Piedmont Plateau. Although the Coastal Plain is characterized by very low relief, it is not featureless. Several low, wave-cut terraces punctuate the landscape for the careful observer.

Other Subregions of the Coastal Plain

The stream-cutting of the Pleistocene that created Chesapeake Bay also led to the dissection of the Coastal Plain into several peninsulas. These are known by the names applied by Virginia's European settlers. Early settlement focused on the James River area; for a number of years The Peninsula was Virginia. Salt and cattle were produced on the Eastern Shore of the Chesapeake. The Northern Neck was given by royal grant to the Cavaliers and it was henceforth a bit different than rest of Virginia. Between the Cavaliers and The Peninsula, logically, lay the Middle Peninsula. The Coastal Plain South of the James was a different place, too. There were the Great Dismal Swamp and rivers flowing to the Carolinas rather than to the Chesapeake to discourage settlement for much of the 17th century.

Other names have been and are today applied to parts of the Coastal Plain. For example, "Tidewater" once referred to all of the coastal plain, but today designates the Norfolk area. Hampton Roads, strictly speaking a body of water, is more commonly used to refer to all the port cities surrounding the mouth of the James River. What other common-use regional names do you know of?

Created by SLW, January 1997. Last updated August 10, 1999 by slw.