Prairies stretch across much of Oklahoma, but the state also holds mountain ranges, including the Ouachita mountains in the south-eastern corner. Formed over 300m years ago, these mountains are a highly eroded remnant of a much larger range, one that may have stretched from Texas into south-eastern Canada. Long before the first dinosaur evolved, what is now the southern-central US sat at the bottom of an ancient sea. From roughly 550-340m years ago, the area collected sediment eroding off nearby continents, as well as detritus of sea life. Starting around 340m years ago, a tectonic plate that had previously been attached to Africa and South America collided with the North American plate. The process helped form the supercontinent of Pangaea, and it thrust the ancient sea floor skyward. The similarities between rock layers of the Ouachita Mountains and the Appalachian Mountains indicate that they were part of a massive mountain chain formed by this collision
Photograph: ASTER/Terra/Nasa
The Guardian
Comments