The Appalachian Orogeny is responsible for the creation of the mountains themselves and is not responsible for the topography that now typifies the Piedmont and coastal plain regions east of the mountain chain. The heavily-eroded hills of Piedmont are remnants of the sizeable mountain chain, while the coastal plain is made up of the material that was washed away in that process. Thus, the coastal plain and Piedmont are largely the byproducts of erosion that took place from 150+ million years ago to the present.
Evidence for the Appalachian 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 it enters a region of confused topography associated with earlier orogenies, but clearly the Applachian deformation extends northeast to Newfoundland.
The mountains were once rugged and high, but in our time are now eroded into only a small remnant. Sediments that were carried eastward form part of the continental shelf. Sediments that were carried westward form the Allegheny and Cumberland Plateau, which in some areas are popularly called mountains, but are actually simply uplifted and eroded plateaus. Carbonates and fine sediments from these mountains were carried farther to form limey rocks in a shallow sea that was later uplifted and forms the bulk of Tennessee, Kentucky, Ohio, and Indiana.
A portion of the Alleghenian mountain system departed with Africa when Pangaea broke up and the Atlantic Ocean began to form. Today, this forms the Anti-Atlas mountains of Morocco. The Anti-Atlas have been geologically uplifted in relatively recent times, and are today much more rugged than their Alleghenian relatives.
The origin of the Variscan upper allochthons in the Ortegal Complex, northwestern Iberia: Sm-Nd isotopic constraints on the closure of the Rheic Ocean.
Jun 01, 2008; Introduction The Rheic Ocean originated in the Late Cambrian--Early Ordovician when a number of terranes (collectively known as...