![]() ![]() Most of the beautiful waterfalls in the park were formed where downcutting streams encountered ledges of very resistant metasandstone that erodes more slowly than the adjacent slate or metasiltstone. Some of these sediments formed our Gulf of Mexico beaches.Īs the mountains were worn down, the layers of rock most resistant to erosion were left to form the highest peaks in the Smokies, such as the hard metasandstone on top of Clingmans Dome. As mountain valleys were carved, tremendous quantities of eroded sediment were transported toward the Atlantic Ocean and Gulf of Mexico by rivers and streams. ![]() The new rugged highlands, the ancient ancestors of the Smokies, were subjected to intense erosion from ice, wind, and water. Huge masses of older, deeply buried rocks were pushed northwestward, up and over younger rocks along a large, nearly flat-lying thrust fault, known as the Great Smoky Fault.įollowing this final episode of Appalachian mountain building, the supercontinent of Pangaea broke apart, and the North American and African tectonic plates gradually moved to their present position. As the African tectonic plate gradually pushed against the edge of the North American plate, the original horizontal layers of the rocks were bent or folded and broken by faults. ![]() These mountains probably were much higher than today, with elevations similar to today's Rockies. The last great episode of mountain building uplifted the entire Appalachian mountain chain from Newfound-land, Canada to Alabama. For example, sandstone became recrystallized to metasandstone or quartzite, and shale became slate. During one of these earlier continental collisions, tremendous pressures and heat were generated, which changed or "metamorphosed" the Smokies sedimentary rocks. Evidence of earlier plate tectonic geologic events are found in rocks of the Great Smoky Mountains, attesting to an incredibly long and active geologic history in this area. Continental collisions take place at a rate of a few inches per year over many millions of years and are the result of continuing global-scale plate tectonics. Fossils found in limestone rocks in Cades Cove are about 450 million years old.īetween about 310 and 245 million years ago, the eastern edge of the North American tectonic plate collided with the African tectonic plate becoming part of a "supercontinent" known as Pangaea. Burrows and trails of worms, as well as small shells of crustaceans that lived in this shallow water along the ancient continental edge, are found in sandstone and shale in the northwestern part of the park. These consist of compacted and cemented sand, silt, and clay deposited in an ancient shallow marine continental margin that existed in what is now the Appalachian region. The younger rocks of sedimentary origin formed during the Paleozoic Era, 450 to about 545 million years ago. The different rock types reflect the range of climatic and topographic conditions that existed during their formation. Today these rocks are known as the Ocoee Supergroup and are subdivided into many smaller divisions of differing rock types. These early sites of ocean bottom deposition were formed along the ancient margin of the North American continent as an older and larger supercontinent broke apart.Īs more and more of these sediments were deposited, they were eventually cemented together and changed into layers of rock over nine miles thick. Rocks of the old highlands were over one billion years old, and were similar to the ancient granite and gneiss found in the southeastern parts of the park. ![]() Vast amounts of unconsolidated clay, silt, sand, and pebbles were washed down into lowland basins from adjacent highlands. The oldest sedimentary rocks were formed during the Proterozoic Era some 800-545 million years ago. Most of the rocks in Great Smoky Mountains National Park are sedimentary and were formed by accumulations of clay, silt, sand, gravel, and minor amounts of calcium carbonate in flat-lying layers. The rocks that form the knife-edged "backbone" of the Chimney Tops are visible beneath lush vegetation. ![]()
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