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The Atlantic Plain is one of eight distinct physiographic divisions of the contiguous United States. Using the USGS physiographic classification system, the Atlantic Plain division comprises two provinces and six sections. The Coastal Plain province is differentiated from the Continental Shelf province simply based on the portion of the land mass above and below sea level.
The lands adjacent to the Atlantic coastline are made up of sandy beaches, marshlands, bays, and barrier islands. It is the flattest of the U.S. physiographic divisions and stretches over in length from Cape Cod to the Mexico border and southward an additional to the Yucatán Peninsula. The central and southern Atlantic Coast is characterized by barrier and drowned valley coasts. The coastal Atlantic plain features nearly continuous barriers interrupted by , large embayments with ria, and extensive and . The Atlantic plain slopes gently seaward from the inland highlands in a series of terraces. This gentle slope continues far into the Atlantic and Gulf of Mexico, forming the continental shelf. The relief at the land-sea interface is so low that the boundary between them is often blurry and indistinct, especially along stretches of the Louisiana bayous and the Everglades.
This province consists of the following physiographic sections: the Embayed, Sea Islands, Florida Platform, East Gulf Coastal Plain, Mississippi Alluvial Plain, and the West Gulf Coastal Plain.
The rocks in the province consist, for the most part, of layers of sand and clay which are not yet hardened into sandstone and shale. The Coastal Plain features nearly continuous barrier islands interrupted by inlets, large embayments with drowned river valleys, and extensive wetlands and marshes. The Coastal Plain slopes gently seaward from the inland highlands in a series of terraces.
The province's average elevation is less than 900 meters above sea level and extends some 50 to 100 kilometers inland from the ocean. The coastal plain is normally wet, including many rivers, marsh, and swampland. It is composed primarily of sedimentary rock and Diagenesis and is primarily used for agriculture. Water table management in the eastern coastal plain The Atlantic Coastal Plain includes the Carolina Sandhills regionSwezey, C.S., Fitzwater, B.A., Whittecar, G.R., Mahan, S.A., Garrity, C.P., Aleman Gonzalez, W.B., and Dobbs, K.M., 2016, The Carolina Sandhills: Quaternary eolian sand sheets and dunes along the updip margin of the Atlantic Coastal Plain province, southeastern United States: Quaternary Research, v. 86, p. 271-286; www.cambridge.org/core/journals/quaternary-research as well as the Embayed and Sea Island physiographic provinces. The Atlantic Coastal Plain is sometimes subdivided into northern and southern regions, specifically the Mid-Atlantic and South Atlantic coastal plains.
The Eastern woodlands are the original, predominant ecosystem of the Atlantic coastal plain. The Atlantic coastal plain upland longleaf pine woodland is an endemic plant community found in most of the Atlantic coastal plain, ranging from Virginia to northern Florida. These woodland savannas are reliant on Sandhill and are fire dependent, lest hardwoods start to dominate. Alongside longleaf pine, typically associated flora includes Quercus laevis and Aristida stricta. The Florida longleaf pine sandhill extends the longleaf pine forests into central Florida, with South Florida slash pine flatwoods, Florida scrub and Florida dry prairie stretching into southern Florida. Longleaf pine woodlands also stretch further west, to eastern Texas. These consist of East Gulf and West Gulf longleaf pine flatwoods, bisected by the Mississippi Alluvial Plain.
on the Eastern Shore of Maryland, with flat terrain typical of the Atlantic Plain]]To the north, the Atlantic Coastal Plain also broaches into the mesic hardwood forests of the Middle Atlantic coastal forests, followed by the northern Atlantic coastal pine barrens. The southernmost Atlantic Plain contains the only Neotropical ecoregion of the continental USA, being the Everglades and Florida mangroves.
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