The Atlantic Coastal Plain is a distinctive physiographic region in North America with low-lying topography. This expansive landform runs parallel to the Atlantic Ocean, a broad, gently sloping expanse. It is one of the flattest physiographic divisions in the United States. Its terrain gradually descends towards the sea.
Geographic Boundaries
The Atlantic Coastal Plain extends from north to south along the eastern seaboard of the United States. Its northern reaches begin around southeastern Massachusetts, including areas like Cape Cod, and stretch southward through New Jersey. The plain continues through Delaware, Maryland, and Virginia, encompassing portions of North Carolina, South Carolina, and Georgia. Further south, it covers nearly all of Florida, ultimately reaching the Florida Keys. This vast stretch makes it one of the longest continuous plains in the country.
The eastern edge of the Atlantic Coastal Plain is defined by the Atlantic Ocean, where its low elevation meets the sea. Inland, its western boundary is marked by the Fall Line, a geological transition zone separating it from the higher elevation Piedmont region. This Fall Line is characterized by a series of rapids and waterfalls on rivers that flow from the Piedmont onto the softer sediments of the Coastal Plain. The plain’s width varies, extending between 50 to 100 kilometers (approximately 30 to 62 miles) inland from the coast.
Geological and Topographical Profile
The physical characteristics of the Atlantic Coastal Plain stem from its geological composition. It is primarily formed from unconsolidated sediments, including layers of sand, silt, and clay. These materials have not yet hardened into solid rock formations like sandstone or shale. The accumulation of these sediments occurred over millions of years, deposited by ancient seas as sea levels fluctuated.
Topographically, it is flat and low in elevation, with an average height less than 900 meters (about 3,000 feet) above sea level. The terrain exhibits a gentle slope, gradually descending towards the Atlantic Ocean.
Key Waterways and Ecosystems
The Atlantic Coastal Plain is crisscrossed by numerous waterways that drain into the Atlantic Ocean. Significant rivers such as the Hudson, Delaware, Savannah, and St. Johns traverse the plain. The region is also home to large embayments like the Chesapeake Bay, which are essentially drowned river valleys.
Characteristic natural features include extensive wetlands, estuaries, and barrier islands. These areas support diverse ecosystems, ranging from pine forests in more elevated sections to vast salt marshes along the coastal margins. The combination of freshwater and saltwater influences in estuaries provides unique habitats for various aquatic species.