Clingmans Dome
       7 ½’ quadrangle: Clingmans Dome, NC-TN
       Sevier County
       Great Smoky Mountains National Park
       Appalachian Trail
       Great Smoky Mountains

Metamorphic (metamorphosed sedimentary)
6,643 ft (2,025 m)

Bedrock: Thunderhead Sandstone, Great Smoky Group

Late Proterozoic

Gray, thick-bedded, coarse- to fine-grained metamorphosed sandstone and conglomerate. Clasts are quartz (often bluish), K-feldspar, plagioclase, granite, and quartzite. Graded beds are common. The sediments were likely deposited in rift basins during continental extension. There are faults in the quadrangle, but not on the mountain. The Oconaluftee fault passes through Newfound Gap, and the Greenbriar thrust fault lies along the northwest foothills, placing the Great Smoky Group on top of the (also Precambrian) Snowbird Group. The rocks of the Great Smoky Group have been folded and metamorphosed, but the sandstones and conglomerates are too quartz-rich to show much evidence of metamorphism. Garnet and biotite occur only in the most clay-rich layers (now schist). A Paleozoic diorite sill intrudes the sandstones on the north slopes of Clingmans Dome. The diorite is conspicuous as red saprolite along the road to the summit.

Surficial Geology: Saprolite (residual weathered bedrock) can be seen in some steep bank cuts. Rock structures such as bedding are preserved even though the saprolite is no longer solid. Unweathered grains of quartz and muscovite can be distinguished in the clay-rich matrix. Southworth and others’ map (2003) shows Pleistocene boulder fields in the upper parts of several ravines on Clingmans Dome, and rounded boulder debris fans in valley bottoms below 1250 m. The summit lies along the border with North Carolina, which here is a watershed boundary between the Little River (north) and the Tuckaseegee River (south), both tributaries of the Little Tennessee River.

Soil Series: Ramsey stony fine sand loam, excessively well drained. The dark gray O horizon is only a few inches thick, overlying a pale-brown to yellowish brown leached A horizon and a brownish yellow subsoil. Parent material is deeply weathered bedrock. Dense mixed conifer and deciduous forests cover the mountain. On steeper slopes, evidence can be seen for severe mass wasting during glacial epochs, when vegetation was sparse. The Ramsey soils are poorly suited to crops or pasture, being deficient in lime, phosphorous, nitrogen and potassium. They are best suited for forestry, though not highly productive.

Environmental Geology:: Clingmans Dome lies in a national park, and so issues related to development and logging are not relevant. However, road building and maintenance might introduce sediment to streams if precautions are not taken. Creep is an important process, since most of the land is steeply sloping. Soils are susceptible to gullying where not vegetated. The Great Smoky Mountains receive some of the highest precipitation levels in the country, and as a result are famous for their biological diversity.

Air quality is probably the most significant environmental issue affecting the park. Haze has always been a factor in the scenery of the Great Smokies (hence the name), but anthropogenic haze is now greatly limiting views even in clear weather. Acid rain has been a problem because the mountains intercept moisture-laden clouds from the west, where coal-fired power plants, traffic, and industries emit sulfur and nitrogen oxides. Rain pH averages 4.5 and has even been recorded as low as 2.0 in clouds on mountaintops. Some plants are affected by acid rain more than others, but conifers at higher elevations seem to suffer the most. Elevated nitrate levels in soils prevent proper uptake of some nutrients by plants, and elevated nitrate levels in creeks can lead to algal blooms. Ground-level ozone has become more of a problem in the Great Smokies in recent years, among the highest levels in the eastern United States and two times the levels in nearby Knoxville. Ozone directly causes damage to plant leaves, especially at higher elevations.

Selected References:

• Hubbard, E. M. and others, 1945 (issued 1956), Soil Survey of Sevier County, Tennessee . U.S. Soil Conservation Service.
• Hadley, J.B and Goldsmith, R., 1963, Geology of the eastern Great Smoky Mountains, North Carolina and Tennessee . U.S. Geological Survey Professional Paper 349-B. 1:62,500
• King, P.B., Neuman, R. B., and Hadley, J.B., 1968, Geology of the Great Smoky Mountains National Park, Tennessee and North Carolina . U. S. Geological Survey Professional Paper 587, 24p, 1:125,000.
• Southworth, S., Schutz, A., Denenny, D., and Triplett, J., 2003, Surficial geologic map of the Great Smoky Mountains National Park region, Tennessee and North Carolina , U.S. Geological Survey Open File Report OF-03-381 (on line). 1:100,000.

Other suggested sources of information:

• Glossary: http://www2.nature.nps.gov/geology/usgsnps/misc/glossaryAtoC.html
• Time scale: http://www.ucmp.berkeley.edu/help/timeform.html
• Tennessee Division of Geology: http://www.state.tn.us/environment/
• Great Smokies National Park: http://www.nps.gov/grsm/