Appalachian orogeny

The Appalachian orogeny is a series of mountain-building events that assembled the Appalachian region through collisions among ancient continents and island arcs.

Iapetus Ocean: An ancient ocean that separated Laurentia from several neighboring continents before the formation of Pangaea. Its closure brought the continental blocks and island arcs that collided along eastern Laurentia.
Laurentia: An ancient continental core that forms much of present-day North America. Its eastern margin was the site of successive Appalachian collisions.
Blue Ridge Mountains: A mountain range along the eastern edge of the Appalachian highlands, underlain by ancient crystalline rocks. Its rocks preserve deep crustal deformation associated with Appalachian mountain building.
Alleghenian deformation: Late Paleozoic folding, faulting, and metamorphism in the Appalachian region associated with continental collision. It captures the structural effects of the Appalachian orogeny’s final major phase.
Subduction: The descent of one tectonic plate beneath another into the mantle. Subduction consumed oceanic crust before and during the collisions that built the Appalachians.
Gondwana: A southern supercontinent that included Africa, South America, Antarctica, Australia, and India. A portion of Gondwana collided with Laurentia during the Alleghanian phase.
Piedmont (United States): A physiographic region of rolling uplands between the Appalachian Mountains and the Atlantic Coastal Plain. Its varied metamorphic and igneous rocks include remnants of terranes accreted during the orogeny.
Appalachian Plateau: A dissected upland west of the Valley and Ridge, underlain largely by gently deformed sedimentary rocks. Its position and structure reflect the westward reach of Appalachian compression and basin development.
Taconic orogeny: An Ordovician mountain-building episode caused chiefly by island-arc collision with eastern Laurentia. It records an early collision in the broader Appalachian mountain-building sequence.
Avalonia: A peri-Gondwanan continental fragment that formed part of the northern Appalachian region. Its arrival at Laurentia is central to accounts of the Acadian orogeny.

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