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Atlantic Plain Province

clickable province index map Atlantic Coastal Plain Pacific Mountains Colorado Plateau Ozark/Ouachita Interior Highlands Appalachian Highlands Laurentian Upland Columbia Plateau Interior Plains Basin and Range Rocky Mountains

spacer image This is the flattest of the provinces. It stretches over 2200 miles in length from Cape Cod to the Mexican border and southward another 1000 miles to the Yucatan Peninsula.
spacer image 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.
spacer image 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 Florida Everglades.

Mangrove swamps obscure the shoreline. Everglades National Park. Photo by ©Marli Miller

The break up of a supercontinent

Pangea in the Early Triassic
spacer image This region was born during the breakup of the supercontinent Pangea in the early Mesozoic Era. From about 280-230 million years ago, (Late Paleozoic Era until the Late Triassic) the continent we now know as North America was continuous with Africa, South America, and Europe.
spacer image Pangea first began to be torn apart when a three-pronged fissure grew between Africa, South America, and North America. Rifting began as magma welled up through the weakness in the crust, creating a volcanic rift zone. Volcanic eruptions spewed ash and volcanic debris across the landscape as these severed continent-sized fragments of Pangea diverged.
spacer image The gash between the spreading continents gradually grew to form a new ocean basin, the Atlantic. The rift zone known as the mid-Atlantic ridge continues to provide the raw volcanic materials for the still expanding ocean basin. In plate tectonic terms, the Atlantic Plain is known as a classic example of a passive continental margin.
Mid-Atlanic Ridge labeled
Click here to view unlabeled map. Image adapted from NOAA.

Meanwhile, back at the edge...

spacer image North America was slowly pulled westward away from the rift zone. The thick continental crust that made up the new east coast collapsed into a series of down-dropped fault blocks that roughly parallel today's coastline. At first, the hot, faulted edge of the continent was high and buoyant relative to the new ocean basin. As the edge of North America moved away from the hot rift zone, it began to cool and subside beneath the new Atlantic Ocean. This once-active divergent plate boundary became the passive, trailing edge of westward moving North America.
spacer image Sediments eroded from the Appalachian and other inland highlands were carried east and southward by streams and gradually covered the faulted continental margin, burying it under a wedge, thousands of feet thick, of layered sedimentary and volcanic debris.
spacer image Today the Mesozoic and Cenozoic sedimentary rock layers that lie beneath much of the coastal plain and fringing continental shelf remain nearly horizontal.

Dig deeper
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Maps and illustrations
Shaded relief with National Park locations
Shaded relief with major and subprovince boundaries
Shaded relief
Atlantic coast and mid-Atlantic ridge
Atlantic coast and mid-Atlantic ridge-labeled
Image gallery
Everglades National Park

| Pacific Mountain System| Columbia Plateau | Basin and Range |
| Colorado Plateau | Rocky Mountain System | Laurentian Upland| Interior Plains |
| Interior Highlands | Appalachian Highlands | Atlantic Plain |
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This page was last updated on 10/10/00