The Appalachian-Ouachita Orogeny was a period of time around 280 million years ago when Gondwana (South America and Africa and Antarctica) moved north and pushed up against Laurentia (North America) and Baltica (Europe), closing the ocean that separated them (the Rheic Ocean), and causing the Appalachian and Ozark-Ouachita mountains to form. They were at that time very much like the Himalayan mountains today (formed in a similar way, as the Indian sub-continent moves north into Asia). It is interesting to note that the Appalachian mountains have formed a few times. They formed about a billion years ago during the Grenville Orogeny, and then again 480-440 million years ago during the middle-Ordovician Period (the Taconic orogeny). This Taconic orogeny pushed up the Appalachian mountains as an oceanic plate (the Iapetus) subducted under the Laurentia’s (North American’s) east (southeast, at that time) coast. An example of mountains formed by an oceanic plate moving under a continent would be the Cascade and Sierra Nevada of the American West Coast. About 150 million years after the Taconic orogeny, around 300 to 280 million years ago, the continents started to drift together, and as Africa and South America (Gondwana) moved up against North America (Laurentia) to form Pangea. The Appalachian mountains were raised again in the Appalachian-Ouachita Orogeny, leaving a great mountain chain in the middle of Pangea (with possibly a diminished Rheic Ocean adjacent to the mountain in the middle of Pangea). By the late Triassic, Pangea was breaking up and South America and Africa were again moving away from North America. Thus, during the Jurassic and Cretaceous Periods (the rest of the Mesozoic), the Appalachian and Ozark and Ouachita mountains eroded away. But then in the late Cenozoic (perhaps as recently as 12-8 million years ago) a the mantle underneath the Appalachian Mountains started to bulge up like a big blister, and this raised the Appalachian Mountains again (causing many of the waterfalls and deep valleys you can find in the Appalachian mountains).

The Appalachian Mountains are shown above; the Ozark highlands are shown below.

1. The North Carolina Museum of Natural Sciences has a good blog post about the recent Cenozoic uplift of the Appalachian Mountains (perhaps 8 million years ago)
2. Sandra H. B. Clark wrote the U.S. Geological Survey guide: Birth of the Mountains: The Geologic Story of the Southern Appalachian Mountains [pdf].
3. A very brief description of the Ouachita-Ozark Interior Highlands geological history from the U.S. Geological Survey.
4. Tracey Peake has a short news item about the Cenozoic uplift.
5. The Open Access journal Geoscience Frontiers published in Volume 3, Issue 2 (March 2012) an article by R. Damian Nance and associates “A Brief History of the Rheic Ocean” that gives an overview of theories of tectonic movement concerning the Appalachian-Ouachita orogeny.

Back to the Biological Timeline: terrestrial animals, trilobite, prokaryote, oxygen catastrophe, Metazoa, eukaryote.

Back to the World History Timeline in English

This work by Eric & Chun-Chih Hadley-Ives is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.