Uplift and folding of the land. In the formation of the Appalachian Mountains, there was a chain of high volcanoes that eroded. Several hundred million years later, the American and African plates collided (the Appalachian Orogeny), resulting in the Appalachian Mountains. The Appalachians first formed roughly 480 million years ago during the Ordovician Period.
- The Appalachian chain is a barrier to east-west travel as it forms a series of alternating ridgelines and valleys oriented in opposition to any road running east-west.
- The term Appalachian refers to several regions associated with the mountain range.
- The Ouachita Mountains in Arkansas and Oklahoma were originally part of the Appalachians but became disconnected through geologic history.