Most of the Smoky Mountains in the national park are sedimentary and were formed by accumulations of clay, silt, sand, gravel minor amount of calcium carbonate. The oldest of the sedimentary rock were formed during the Proterozoic Era about 800-545 million years ago. About 310-245 million years ago, the eastern edge of the North American tectonic plat collided with the African plate becoming part of a supercontinent. During one of earlier collisions, tremendous heat and pressure were generated. This changed the Smoky sedimentary rocks. For example, sandstone became recrystallized into quartzite and shale became slate.
The last great episode of the mountain building uplifted the entire Appalachian mountain chain from Newfoundland, Canada to Alabama. The mountains then were much higher than they are today. As the African tectonic plate gradually pushed against the edge of the North American plate, the original layers of the rocks were bent, broken and folded by faults. Huge masses of older, deeply buried rock were pushed up and over younger rocks. This is known as the Great Smoky Fault.
Following the final episode, the North American and the African tectonic plates broke apart and moved in to their present position. The ancient ancestors of the Smoky Mountains were subjected to intense erosion from ice, wind, and water. As the mountain valleys were carved, tremendous quantities of the eroded material were transported to the Atlantic Ocean and the Gulf of Mexico. Some of these form the beaches in the Gulf of Mexico.
As the mountains were worn down, the layers of rock resistant to the erosion were left to for the highest peaks of the Smoky Mountains. Today geologist estimate that the mountains are being eroded about two inches every thousand years.