Mammoth Cave

As rainwater falls, it absorbs atmospheric carbon dioxide. Once in the rainwater, the carbon dioxide reacts with water to form an acid known as carbonic acid, H2C03, which, as we discuss in this chapter, makes rainwater naturally acidic. As the rainwater passes through the ground, the carbonic acid reacts with various basic minerals, such as limestone, to form products that are water soluble and thus carried away by the underground flow of water. This washing-away action over the course of millions of years creates caves.The world s most extensive cave system is in western Kentucky in Mammoth Cave National Park, where more than 300 miles of networked caves have been mapped. 

Check these official and unofficial sites for Carlsbad Caverns National Park and Mammoth Cave National Park for details on how these underground landmarks formed Ample travel information is included. 

The effect of pH on the solubility of CaC03 has important environmental consequences. For instance, the formation of limestone caves, such as Mammoth Cave in Kentucky, is due to the slow dissolution of limestone (CaC03) in the slightly acidic natural water of underground streams. Marble, another form of CaC03, also dissolves in acid, which accounts for the deterioration of marble monuments on exposure to acid rain (Interlude, pages 650-651). 

Figure 4. A representative cross-section of channel facies sediment. The Chaperon, a filled side passage on Rose s Pass, Mammoth Cave, Kentucky. From Davies and Chao (1959).

Figure 5. Map of Columbian Avenue, Flint Ridge section of Mammoth Cave showing location of sediment pits. Underlined numbers are elevations in meters above pool stage of Green River. Base map adapted from Brucker and Bums (1964).

Figure 6. Series of stratigraphic columns along Columbian Avenue, Flint Ridge section of Mammoth Cave Kentucky showing lithologic characteristics of channel facies. Columns are keyed to core locations shown in figure 7. Note the total column thickness original columns were drawn to two different scales. Original data from Carwile and Hawkinson (1968).

Logsdon River has been explored upstream from the confluence for more than seven kilometers. It more or less parallels the escarpment at the southern edge of the Mammoth Cave Plateau and is a master drain for the karst as far northeast as Roppel Cave. It is known to receive recharge from valley drains and vertical shafts and also from the sinking streams and sinkhole inputs on the Sinkhole Plain to the southeast. The Logsdon River sediments are mainly silts and fine sands with 40 - 60% of the material smaller than the smallest sieve size used. 

Mammoth Cave provides excellent exposures of slackwater facies (Fig. 4). At the tops of most sediment piles is a layer, seldom more than a few cm thick, of thinly layer clay and very fine silt. Some of these sedimentary layers are varved, apparently representing an annual cycle of flooding with the rise and fall of the ancestral Green... 

Bretz, J H., 1942. Vadose and phreatic features of limestone caverns, J. Geol. 50 675-811 Brucker, R.W. and Bums, D.P., 1964, The Flint Ridge Cave System, Mammoth Cave National Park, Kentucky, Cave Research Foundation, Washington, DC, Folio, 3pp text plus 31 maps. 

Davies, W.E. and Chao, E.C.T., 1959, Report on the sediments in Mammoth Cave, Kentucky, U.S. Geol. Survey Administrative Rpt. to U.S. Natl. Park Service, 117 p. 

Pickle, J.D., 1985, Dynamics of clastic sedimentation and watershed evolution within a low-relief karst drainage basin. Mammoth Cave Region, Kentucky, MS Thesis, University of New Mexico, Albuquerque, 147 pp. 

Quinlan, J.F. and Ewers, R.O., 1989, Subsurface drainage in the Mammoth Cave Area, Chap. 3 in Karst Hydrology - Concepts from the Mammoth Cave Area, W.B. White and E.L. White, eds.. Van Nostrand Reinhold, New York, pp. 65-103. 

Schmidt, V.A., 1982, Magnetostratigraphy of sediments in Mammoth Cave, Kentucky, Science 217 827-829. 

Harmon, R.S., Schwarcz, H.P. and Ford, D.C., 1978c, Stable isotope geochemistry of speleothems and cave waters from the Flint Ridge-Mammoth Cave System, Kentucky Implications for terrestrial climate change during the period 230,000 to 100,000 years B.P., J. Geol. 86 373-384. 

Most analytical techniques require the state of chemical equilibrium. At equilibrium, the rate of a forward process or reaction and that of the reverse process are equal. The photo at left shows the beautiful natural formation called "Frozen Niagra in Mammoth Cave National Park in Kentucky. As water seeps over the limestone surface of the cave, calcium carbonate dissolves in the water according to the chemical equilibrium... 

Vadose water from Lower Carboniferous rocks in Kentucky, U.S.A., was analyzed monthly in Mammoth Cave and in the caves and overlying soil at two other caves. Calcite saturation and equilibrium CO2 pressures of water were calculated after correcting for ion pairing and activity coefficients. Soil gas CO2 concentrations were determined directly. 

Water samples were collected in Mammoth, Cascade and X caves, and water and gas samples were collected from the soil overlying Cascade and X caves. Mammoth Cave is in west-central Kentucky and Cascade and X caves are 300km from Mammoth in northeastern Kentucky. Cascade and X caves are 3 km apart. AU three caves are developed in limestones of Late Mississippian age and are within a few hundred meters of the outcrop of overlying Upper Mississippian and/or Pennsylvanian sandstones and shales. 

The temperatures of both the Mammoth Cave and the Cascade and X caves areas are similar, with a January mean minimum of — 2°C and a July mean maximum of 32°C. The mean annual precipitation is 0.10 m in the Mammoth Cave area and 0.13 m in the Cascade and X caves area and is fairly evenly distributed over the year (Karen and Mather, 1977). 

Diagrammatic cross-sections of the sampled sites are shown in Fig. 3. Comparison of Fig. 2 with Fig. 3 shows that Ca of the vadose seepages in Mammoth Cave (sites 3—6) decrease with depth below the surface, and that site 4, which had the lowest Ca, is beneath a sandstone caprock. Although no study of the soils was undertaken at Mammoth Cave, it is likely that the low Ca of site 4 is due to its being fed from soil water in a non-carbonate soil, and that the progressive increase in Ca in drips underlying the downslope soils reflects a progressive increase in carbonate soil fractions with distance... 

Fig. 3. Index map and cross-sections showing location of sites. Dotted pattern shows capping sandstone and shale at Mammoth Cave and soil at Cascade and X caves.

Appreciation is expressed to M.T. Osolnik, R.H. Postley, and the superintendent and staff of Mammoth Cave National Park for their assistance in the Mammoth Cave study, which was funded by the Office of Water Resources Research (now the Office of Water Research and Technology), U.S. Department of the Interior and to J. Tierney, park naturalist, and the staff of Carter Caves State Resort Park for their cooperation in the study of Cascade and X caves. 

Stalactites and stalagmites in the Drapery Room at Mammoth Cave in Kentucky. These formations are created when carbonate minerals dissolve in groundwater acidified by carbon dioxide and then solidify when the water evaporates. 

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