Appalachian Orogeny



The Appalachian Orogeny is an excellent example of a mountain building event resulting from tectonics. The Appalachian Orogeny resulted from three separate continental collisions formed the Appalachian Mountains and Allegheny Mountains at the end of the Paleozoic. The combined continents of Europe and Africa (Gondwana) collided with North America to form the supercontinent of Pangaea approximately 350 million to 300 million years ago during the Carboniferous period. The collision exerted enormous stress on what today is eastern North America, an causing an enormous upward thrusting of the entire region. The tectonic stresses also metamorphosized of the rock from igneous and sedimentary rock into metamorphic rock. These stresses concurrently caused faults (mostly thrust faults and some strike-slip faults) as well as folding. It is believed that the Appalachians once could have risen as high as or even higher than the Himalaya (i.e., more than 4 ½ miles high). These mountains, while still impressive in places, are mere remnants of their glory days during the Paleozoic. They have been worm away by the relentless forces of erosion, forming vast amount of sediments in the process. Carbonates and sediments from mountains formed in the Appalachian Orogeny were away to form limey rocks in a shallow sea that was later uplifted and now forms the majority of Tennessee, Kentucky, Indiana and Ohio.