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Alleghanian orogeny

Mountain-forming event that formed the Appalachian and Allegheny Mountains / From Wikipedia, the free encyclopedia

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The Alleghanian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 1957.

Location of the Hercynian/Variscan/Alleghanian mountain chains in the Carboniferous period. Large labels are continents that joined during these orogenies. Present day coastlines in gray. Sutures are red.

The Alleghanian orogeny occurred approximately 325 million to 260 million years ago [1] over at least five deformation events [2] in the Carboniferous to Permian period. The orogeny was caused by Africa's collision with North America. At the time, these continents did not exist in their current forms: North America was part of the Euramerica super-continent, while Africa was part of Gondwana. This collision formed the super-continent Pangaea, which contained all major continental land masses. The collision provoked the orogeny: it exerted massive stress on what is today the Eastern Seaboard of North America, forming a wide and high mountain chain.[3] Evidence for the Alleghanian orogeny stretches for many hundreds of miles on the surface from Alabama to New Jersey and can be traced further subsurface to the southwest. In the north, the Alleghanian deformation extends northeast to Newfoundland. Subsequent erosion wore down the mountain chain and spread sediments both to the east and to the west.