There are commonly two understandings of the Blue Ridge. The first is the geologic Blue Ridge, which is found only in Oconee County, bounded on the west by the Chattooga River and on the east by the Brevard Fault. The second is the geographic Blue Ridge, which includes both the Blue Ridge Mountains and inner Piedmont mountains such as Sassafras, Pinnacle, and Table Rock.
The Blue Ridge in South Carolina forms the smallest of the geological provinces. There are commonly two understandings of the Blue Ridge. The first is the geologic Blue Ridge, which is found only in Oconee County, bounded on the west by the Chattooga River and on the east by the Brevard Fault. The second is the geographic Blue Ridge, which includes both the Blue Ridge Mountains and inner Piedmont mountains such as Sassafras, Pinnacle, and Table Rock. The geologic Blue Ridge refers to the rocks of the region and their histories, and the geographic Blue Ridge refers to the shape of the land. The distinction is important because the two areas have different geologic histories; they were formed at different times and contain different rocks.
The size of the geologic Blue Ridge is so small in South Carolina that only by looking at its continuation into Georgia, North Carolina, and Virginia could geologists form reasonable interpretations of its history. The Blue Ridge appears to lie over an eroded mountain system known as the Greenville Range, which once formed the edge of a much smaller North America. As the east coast of North America rifted apart from another plate during the late Precambrian period, extensive sedimentary deposits and volcanics developed on the continental shelf. Then, in the Ordovician period, a collision occurred with what were perhaps a previously detached continental fragment and an island arc that moved toward and eventually welded onto North America. During the millions of years that the collision developed, the rocks of the continental shelf were shoved upward into what must have been a high mountain range. This became the Blue Ridge. During later continental collisions, lastly with the African plate during the Pennsylvanian to Permian time, the remnants of the eroded Blue Ridge were again thrust upward. In the Great Smoky Mountains of North Carolina and Tennessee, there exist “coves,” such as Cades Cove, which are areas where overlying, older Blue Ridge rock has eroded to form a “window” onto younger Ordovician sediments that lie underneath. Applying this understanding to the Blue Ridge in South Carolina allows geologists to argue that while the Blue Ridge is related to the rocks of the Piedmont by events in the past, it has a different age, structure, and history than they do. The rocks of the Blue Ridge in South Carolina include gneisses, schists, metagreywackes, pegmatites, and amphibolites that were formed from heat and pressure applied to the original sediments and volcanics of the Precambrian continental shelf rocks.
The Blue Ridge contains many interesting geologic features that are clearly visible in particular sites. The Blue Ridge is contained primarily within the boundary of the Sumter National Forest, including the town of Mountain Rest. A popular area to visit and explore the geology is the Chattooga River valley, where rocks can be observed along the many hiking trails in the area. Included between the East Fork of the Chattooga River and Georgia is Ellicott Rock, which marks the intersection of South Carolina, North Carolina, and Georgia. In addition, the Chauga River provides large and clear rock exposures in several areas and flows through a scenic ten-mile gorge.
The Brevard Fault is the geologic boundary between the Blue Ridge and the inner Piedmont belt. It is found from Virginia to Alabama. The Brevard Fault ranges in size from one-third of a mile to two miles wide, forming a valley in places. Geologists believe that it forms the root of the Blue Ridge thrust sheet. The movement of the fault crushed the nearby rock, weakening the surrounding rock, which allowed erosion to carry the rock fragments away easily, creating a valley.
The geographic Blue Ridge includes the land area at and above the Blue Ridge Escarpment, including the geologic Blue Ridge Mountains within South Carolina. This area, located in Oconee, Pickens, and Greenville Counties, includes some of the most scenic highlands and mountains in the state and contains South Carolina’s highest point, Sassafras Mountain, which stands at 3,554 feet above sea level. The geology of the inner Piedmont, like the Blue Ridge, also involves a collision of what is thought to have been a continental fragment, with a much earlier North America during the Ordovician period. Later collisions between continental plates, namely African and possibly South America, created metamorphic conditions that altered the granites to metagranites, or migmatites. Over millions of years the land was uplifted and highly eroded, and these metagranites rose to the surface. The results of this process include mountains such as Table Rock, Caesars Head, and Sassafras, among many others.
Able, Gene. Exploring South Carolina: Wild and Natural Places. Rock Hill, S.C.: Palmetto Byways, 1995.
Kovacik, Charles F., and John J. Winberry. South Carolina: The Making of a Landscape. 1987. Reprint, Columbia: University of South Carolina Press, 1989.
Murphy, Carolyn H. Carolina Rocks! The Geology of South Carolina. Orangeburg, S.C.: Sandlapper, 1995.