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Karst Topography in Missouri Karst is a landscape characterized by the presence of caves, springs, sinkholes and losing streams known as karst features. Karst got its name after the kras region in the Dinaric Alps of Slovenia; a region underlain by soluble limestone which has been dissolved by water to form a porous topography. The processes of karst formation were first studied by geologists and geographers in this area and karst has become a general term applied to any area where such processes have been at work. The word karst (karst in German and carso in Italian) originates from a pre-Indo-European word karra meaning stony. Fifty-nine percent of Missouri is underlain by thick, carbonate rock units that host a wide variety of karst features. Because of this karst topography, Missouri has plentiful groundwater resources. Karst is a term used to denote areas where the topography is mostly formed by the dissolving of soluble rock such as limestone and dolomite. Rainwater passing through the atmosphere absorbs carbon dioxide and becomes slightly acidic. Acidity increases as the water moves through the soil materials absorbing more carbon dioxide and organic acids. The water dissolves the limestone and dolomite as it moves through fractures, bedding planes, and pores in the carbonate bedrock; each drop of water removing a minute quantity of rock. The more rainfall that can be recharged, the larger the openings grow, and the deeper the circulation. Over time, karst features develop.

Karst Features Some of Missouri’s most stunning natural features are the result of this Karst topography at work. Mysterious natural

bridges, gaping caverns, and brilliant blue-green springs pepper the state of Missouri. Our State Parks, like Ha Ha

Tonka State Park, Onondaga Cave State Park, Grand Gulf State Park, Meramec State Park and more have an amazing

variety of these karst features.

Grand Gulf State Park displays the karst fea-

tures of a collapsed cave system, sinkholes

and a natural bridge.

Ha Ha Tonka State Park is Missouri's premiere showcase of karst geology. The park features a

spectacular gorge with sheer cliffs nearly 250 feet high, a natural bridge, the “Colosseum” sinkhole,

Ha Ha Tonka Spring and several caves.

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Karst Aquifers Are Vulnerable to Pollution Water recharge to karst aquifers occurs directly, either through swallow holes and sinkholes, or indirectly through the macropores in the soil overlying the limestone bedrock. Although the soil overlying a karst aquifer provides some filtration of contaminants from in-flowing water, almost none takes place between swallow holes and springs. Groundwater flows through conduits so that there is little opportunity for filtration or sorption of contaminants into aquifer material. The movement of pollutants cannot be directly observed as in a surface-flowing stream. Flow paths may take routes that are not apparent from the topography or slope of the land. Flow velocities in karst aquifers are fast compared to velocities in granular aquifers, allowing little time to warn downstream users if a chemical spill is reported.

Dye Tracing Ground water in karst topography is particularly vulnerable to contamination from poor agricultural practices, land development, chemical spills or intentional dumping into sinkholes. Dye tracing is a useful tool that uses non-toxic fluorescent tracer dye and scanning technology equipment to provide a safe and effective method for water investigations and protection of water supplies. The procedure can determine the direction of ground-water flow and the location of natural discharge points for the karst aquifer system that drains a spill or dump site. Dye tracing also makes possible a good approximation of the time of travel, peak concentration, and flow duration of harmful contaminants accidentally spilled into karst aquifers and flowing to a spring or well. Along with groundwater investigations, dye traces are also performed for cave exploration and determining if septic systems are working properly to name just a few.

Conducting a groundwater dye

trace originating from a trash-filled

sinkhole.

The flow of water from surface runoff into a sinkhole provides almost

no filtration prior to entering the groundwater of a karst aquifer.

Missouri’s karst topography is underlain by soluble carbonate rock such as limestone and dolomite.

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For more information: DNR Youth Education and Interpretation P.O. Box 176 Jefferson City, MO 65102-0176 1-800-361-4827 or (573) 522-2656 office e-mail: naturalresources.ed@dnr.mo.gov http://dnr.mo.gov/education

Glossary of Terms Bedding plane: The area that separates two rock strata of differing characteristics.

Carbonate rocks: A class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone and dolomite. Karst topography and caves develop in carbonate rocks because of their solubility in di-lute acidic groundwater.

Granular aquifer: An aquifer composed of granular materials such as loose sand and gravel or weakly cemented bed-rock. Groundwater flow through the pores or spaces between the grains of sand and gravel or through narrow frac-tures in solid bedrock is usually very slow.

Macropore: A pore or space in soil of such size that water drains from it by gravity and is not held by capillary action.

Sorption: A physical and chemical process by which one substance becomes attached to another .

Swallow hole: A depression in the ground connecting with an underground passage in karst topography and formed by solution or by collapse of a cavern roof. Also referred to as a sinkhole.

Topography: The shape of an area of land, including its hills, valleys and streams.