The Alleghanian Orogeny: Building Of The Appalachian Mountains In North America

The Alleghanian Orogeny was the building of the Appalachian Mountains in North America. Around 250 to 300 million years ago, the Alleghanian Orogeny was the last mountain building period for North America. The sediment from the Iapetus Ocean Basin was pushed up as Africa and North America collided head on. Same like the three other building periods, the crust was pushed upwards while being compressed and squeezed. The Appalachian Mountains stretched from Alabama to Canada. The evidence that this orogeny actually happened are the mountains found on the east coast of North America and the mountains on the North western side of Africa. The erosion of these mountains eroded into the western inland sea raising the the Appalachian basin and the inland sea itself. The Iapetus Ocean had closed earlier during other orogenies. The Iapetus Ocean became a basin. When Africa and North America collided, the Iapetus Ocean sediment was pushed up and built the Appalachian Mountains. This around when Pangea was created.
When North America started moving away, rift lines were created. In the Connecticut River Valley, the rift created there had the potential of breaking apart and creating the Atlantic Ocean. The River Valley didn’t break apart but it got deeper because of the failed rifting. The Iapetus Ocean Basin was the rift that opened up instead of the Connecticut River Valley. The rift in this basin created the Atlantic Ocean. Today, most of the coastline is similar to the rifts created when all the continents were separating. While this was happening, sandstone and shale were being deposited in some of the rift basins. During the Jurassic, North America completely broke away from all other continents and began floating to the present day position. North America never again felt that strong tectonic