Introduction Karst in Indiana

Indiana Geological and Water Survey | Indiana University 420 N. Walnut St., Bloomington, IN 47404 | 812.855.7636 Home / Indiana Geology / General Geology / Bedrock Geology Karst Features in Indiana by Nancy R. Hasenmueller and Drew M. Packman Introduction Karst is a distinctive type of landscape or topography that commonly occurs where carbonate strata (limestones and dolostones) are at the surface. Slightly acidic rainwater and water in the soil slowly percolate through fractures, dissolving the rock and creating sinkholes, caves, and many other features that characterize karst. In arid locations, karst features can develop on soluble bedrock units such as gypsum or salt deposits (White, 1988). Karst in Indiana Southern Indiana has several well-developed areas of karst landscape. The Mitchell Plateau is a broad carbonate karst plateau dissected by a few major stream systems (Malott, 1922; Gray, 2000) (fig. 1). This plateau is developed on Mississippian carbonates and extends from the eastern part of Owen County southward to the Ohio River in Harrison County and into Kentucky. To the west, the Crawford Upland is characterized by ridges and valleys developed on shale, sandstone, and carbonate strata of Mississippian age. Sinkholes, karst valleys, and caves are common along the eastern margin of this physiographic division where carbonate units are present (Gray, 2000). Some karst Figure 1. Physiographic divisions of Indiana features are also developed in carbonate strata along (Gray, 2000). Click on the map to view the western margin of the Norman Upland to the east of enlarged map showing the physiographic the Mitchell Plateau. divisions of southern Indiana. In south-central Indiana, karst features are present in the Other physiographic divisions that exhibit karst Mitchell Plateau and parts of the Crawford features are located in southeastern Indiana and are and Norman Uplands. In southeastern known as the Muscatatuck Plateau and the Indiana, karst is present in the Muscatatuck Charlestown Hills (Gray, 2000). These areas are Plateau and Charlestown Hills physiographic developed on carbonate strata of Silurian and Devonian divisions. age. Much of the northern two-thirds of Indiana is covered by unconsolidated Pleistocene glacial materials of varying thickness. In most areas of northern Indiana where carbonate rocks constitute the bedrock, karst features are not exposed at the surface but are buried. However, in some areas along the Wabash River the glacial materials are thin or absent and karst features are exposed at the surface. Karst solution features When carbonate rocks dissolve, distinctive solution features develop that are characteristic of karst terrains; the more common features are springs, sinkholes, caves, and sinking or disappearing streams (fig. 2) (Hasenmueller and Powell, 2005). Springs are places where subsurface water flows from rock or soil onto the land surface. Sinkholes form where the carbonates are dissolved and the soil layer on top falls into the resulting depression. Sinkholes may or may not Figure 2. Solution features characteristic of have an apparent opening to underground drainage. karst terrains (Hasenmueller and Powell, Sinking or disappearing streams are surface streams 2005). in karst areas that flow directly into the groundwater system at a feature called a "swallow hole." Underground drainage systems, composed of solution-enlarged features, conduits, and caverns dissolved in the strata through which water may flow are common to karst areas. Surface streams in a karst area are generally short and lose their water during dry periods, but some sinking streams drain many square miles. Karst hazards Groundwater contamination: The uppermost or shallow groundwater in karst terrains can easily be contaminated because surface waters can move rapidly and flow directly into the subsurface at sinkholes and swallow holes (Hasenmueller and Powell, 2005). This water flows underground without the benefit of filtration by soil and bedrock or exposure to sunlight that might remove some organic contaminants. We can protect the karst environment by not disposing of trash in sinkholes. Also, we need to be aware of the proper use of insecticides, herbicides, and fertilizer to prevent contamination of the groundwater (Hasenmueller and Powell, 2005). Figure 3. Extensive karst flooding was caused by a lack of surface drainage near Bellevue, Drainage problems: Drainage problems can arise when Ohio. Surface and near-surface geologic the karst landscape is altered by building and conditions, combined with increases in development (Veni and others, 2006). Erosion caused precipitation, resulted in groundwater rising by construction and the resulting transport of soil may to the surface; flowing from existing clog sinkholes that normally drain surface waters. sinkholes; and filling closed basins and Subsequently, even smaller storms are capable of sinkholes, caverns, and underground flooding the sinkholes and surrounding areas (fig. 3). drainage passageways (Pavey and others, The construction of impermeable surfaces, such as 2012). (Photograph courtesy of Douglas J. buildings and pavement, also increases the amount of Aden.) water that flows on the surface. This can result in temporary flooding in the vicinity of a sinkhole that would normally be able to accept the entire discharge (Veni and others, 2006). Collapse features: A sinkhole is a collapse feature. Scientists define a sinkhole as a closed or bowl-shaped depression that develops in karst. The term "sinkhole" has been incorrectly used by some to describe collapse features that are not karst in origin, such as depressions caused by subsidence over an abandoned underground coal mine or a washout of unconsolidated material caused by a broken water or sewer line. Several incidents of sinkhole collapse in Florida recently were reported in the news. People wonder if something similar could happen in Indiana; however, there are some geologic and hydrologic differences between the karst and cavernous regions of Indiana and those of Florida. Many of the collapse sinkholes in Florida that effect buildings are in urban or suburban areas and were caused by leakage from water and sewer lines, swimming pools, and ponds. The drainage of this water through a semiconsolidated or poorly cemented sand formation overlying a cavernous carbonate unit results in the formation of sinkholes. Another issue in Florida is an extreme lowering of the water table related to drought conditions and excessive agricultural pumping; this results in the sediment in the sinkhole no longer being supported underneath. Rainfalls have collapsed these unsupported sediments. The karst sinkhole areas in Indiana are developed on relatively well-cemented, dense carbonate formations. Most of the sinkholes in Indiana are obvious (fig. 4) and are not problems for construction unless a structure is sited on too steep a slope, or a sinkhole has been filled in without the builder's knowledge. Exploring karst features in Indiana A number of karst features in Indiana are easily accessed and can be explored. Spring Mill State Park near Mitchell is near the type locality of the Mitchell Plateau (Malott, 1922, p. 127). Caves, springs, and numerous sinkholes are some of the karst features that can be seen within the park. In 2009, all caves and sinkholes on Indiana Department of Natural Resources (DNR) property, with the exception of Twin Caves at Spring Mill, and on federal property were closed to the public to curtail the spread Figure 4. A sinkhole developed in of white-nosed syndrome, a fungus that has killed bats Mississippian carbonate rock in Lawrence in large numbers in the northeastern, southeastern, County, Indiana. (Photograph courtesy of and midwestern United States. In 2014, the Indiana Samuel S. Frushour.) DNR initiated a pilot program to allow limited access to select caves at Spring Mill State Park and Cave River Valley Natural Area. The program, in partnership with the Indiana Karst Conservancy, allows for recreational caving by groups on an interim basis. McCormick's Creek State Park in Owen County is near the northern extent of the Mitchell Plateau. This park has several karst features including Wolf Cave, natural bridges, and a number of deep sinkholes (Frushour, 2012). Cave River Valley Natural Area in Washington County is another karst area in the Mitchell Plateau physiographic division of Indiana. Its most noteworthy feature is its caves, some of which are bat hibernacula. Wyandotte Cave in Crawford County was designated a National Natural Landmark in 1972 and is now part of O'Bannon Woods State Park. The cave, located within the Harrison-Crawford State Forest, has more than 9 miles of explored passageways, huge rooms, vertical shafts, cave breakdowns, and speleothems. As of June 2010, Wyandotte Cave was closed indefinitely in an effort to protect the bat population against white-nose syndrome. Privately owned show caves such as Marengo Cave, Bluespring Caverns, and Squire Boone Caverns remain open to the public for tours. More information about these caves can be found in A Guide to Caves and Karst of Indiana (Frushour, 2012). When visiting caves and other karst features always follow safety precautions. For more information about cave safety, visit the Figure 5. Wesley Chapel Gulf in Orange website "Caves–visiting caves and cave safety" County, Indiana; sketch map originally drawn (Frushour, n.d.). by Clyde A. Malott in 1931 (Malott, 1932). The largest spring in Indiana, Harrison Spring in Harrison County is

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