America's Volcanic Past
South Carolina

The Appalachians:³
The Appalachians are old. A look at rocks exposed in today's Appalachian mountains reveals elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks and slivers of ancient ocean floor. Strong evidence that these rocks were deformed during plate collision. The birth of the Appalachian ranges, some 480 million years ago, marks the first of several mountain building plate collisions that culminated in the construction of the supercontinent Pangea with the Appalachians near the center.

East Coast Volcanoes:⁴
During the early part of the expansion of the continental crust (about 750 million years ago), a deep basin, known as the Ocoee basin, formed on the margin of the supercontinent what is now the western Carolinas, eastern Tennessee, and Georgia. Seawater filled the basin. Rivers from the surrounding countryside carried clay, silt, sand, and gravel to the basin, much as rivers today carry sediment from the midcontinent to the Gulf of Mexico. The sediment spread out in layers on basin floor. The basin continued to subside, and over a long of time, probably millions of years, a great thickness of sediment accumulated. The sediments of the Ocoee basin now form the bedrock of the Great Smoky, Unicoi, and Plott Balsam Mountains. At the time that sediments were being deposited and mineral deposits were forming in the Ocoee basin, volcanoes were erupting in areas that are now Virginia, the Carolinas, and Georgia. Lava from some volcanoes flowed in slow-moving sheets like lava from the Hawaiian volcanoes, but other eruptions were explosive, like Mount St. Helens. Although volcanic activity ended hundreds of millions of years ago, rocks that formed from these ancient volcanoes are still visible. Fragments that erupted from ancient volcanoes and minerals that filled holes where gas bubbles had escaped can be seen in some rocks at White Top Mountain in the Mount Rogers National Recreation Area of southern Virginia.

North Central South Carolina:¹
570 million years go (Cambrian), deposition of volcanic and sedimentary rocks found in the Charlotte Slate Belt. Outcrops of granite and gabbro.