Numerous warm springs have been discovered issuing from the folded and thrust-faulted rocks of the Appalachian Mountain system between Massachusetts and Georgia; however, the highest temperatures in Virginia are only about 41°C. There is no longer much speculation that the source of the heat might originate from relatively young, still-cooling plutonic rocks. Most workers who have studied these springs believe that the source of the heat is simply deep meteoric circulation of meteoric water to depths of 2-3 km along fracture zones and permeable bedding planes. On its way down, the water is heated in the earth's normal geothermal gradient, which is about 10ºC/km over the first 300 m in the Knox dolomite in the Warm Springs, VA area. It appears that relatively resistant quartzites such as the Tuscarora quartzite play an important role in the occurrence of the springs. In the Virginia area of warm springs area where the relatively thin (50-200 ft) Tuscarora Quartzite is near-vertical or steeply dipping, the structural relief of the steep limb of anticlines can extend to depths of about 2-3 km. Water entering the steeply-dipping recharge areas along ridges can extend to depths of 2-3 km (see Figure below). The geologic model for the origin of the warm springs in Virginia (and the entire eastern United States) is thus one of deep meteoric circulation, as shown in the figures below.
It is well known from a thermodynamic standpoint that a lot of warm water at a lower temperature is considerably better from the standpoint of geothermal resource potential than a little water of considerably higher temperature. In the Warm Springs, VA, area, there is a relatively small volume of water available at a temperature of 41°C, but there is considerably more available at lower temperatures. Indeed, the warm water here is an actively exploited geothermal resource, and is being used for space heating at The Homestead resort complex at Warm Springs, VA.
Costain, J.K., Keller, G.V., and Crewdson, R.A., 1976, Geological and geophysical study of the origin of the warm springs in Bath County, Virginia, Final Report TID-28271 to the U.S. Department of Energy, 184 pp.
Muffler, L.J.P., 1979, Assessment of Geothermal Resources of the United States--1978, U.S. Geological Survey Circular 790, 163 pp.
Perry, L.D., Costain, J.K., and Geiser, P.A., 1979, Heat flow in western Virginia and a model for the origin of thermal springs in the Appalachians, J. Geophysical Research, v. 84, No. B12, p. 6875-6883.
Reed, M.J., 1983, Introduction, in M.J. Reed, ed., Assessment of low-temperature geothermal resources of the United States -- 1982, U.S. Geological Survey Circular 892.
Reed, Marshall J., Mariner, Robert H., Brook, Charles A., and Sorey, Michael L., 1983, Selected Data for Low-Temperature (less than 90oC) Geothermal Systems in the United States; Reference Data for U.S. Geological Survey Circular 892, U.S. Geological Survey Open-File Report 83-250, 129 pp.
Sorey, M.L., Reed, M.J., Foley, D., and Renner, J.L., 1983, Low-temperature geothermal resources in the central and eastern United States, in Reed, M.J., ed., Assessment of low-temperature geothermal resources of the United States -- 1982, U.S. Geological Survey Circular 892.
|Return to:||Geothermal Homepage||Geological Sciences||Virginia Tech|