The geology of the Appalachians dates back more than 1.2 billion years to the Mesoproterozoic era[1] when two continental cratons collided to form the supercontinent Rodinia, 500 million years prior to the development of the range during the formation of Pangea. The rocks exposed in today's Appalachian Mountains reveal elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks, and slivers of ancient ocean floor—strong evidences that these rocks were deformed during plate collision. The birth of the Appalachian ranges marks the first of several mountain building plate collisions that culminated in the construction of Pangea with the Appalachians and neighboring Anti-Atlas mountains (now in Morocco) near the center. These mountain ranges likely once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded.[2][3]
The foundations of the Appalachian-Ouachita orogen were laid when the assembly of supercontinent Rodinia was completed. The collisional events were accompanied by high-grade metamorphism and magmatism during the Grenville orogeny in the time span of 1300–950 Ma.