Underneath the rolling hills and glistening streams of Southern Indiana lies an extraordinary world practically unknown to humankind. The mysterious underground world of caves with their intricate passageways and dramatic formations is a whole new world just waiting to be explored. This one of a kind natural community is known as karst.
What is Karst & Where is it in Indiana?
Karst topography is a distinctive type of landscape largely shaped by the dissolving action of groundwater on carbonate bedrock, usually limestone. This geological process, which will take thousands of years, is characterized by unique features such as sinkholes, fissures, caves, disappearing streams, springs, rolling topography, and underground drainage systems.
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The karst formation process involves what scientists refer to as "the carbon dioxide cascade." As rain falls, it picks up CO2 which dissipates in the droplets. When the rain seeps into the soil, it picks up more carbon dioxide and forms a weak solution of carbonic acid (H2O + CO2 = H2CO3). Over long periods of time, a continuous flow of this acidic water will dissolve carbonate bedrock and create larger openings in cracks and crevices already in the rock. An underground drainage system will eventually form, allowing more water to pass and will lead to the development of caves and other karst formations.
There are two areas of karst landscape in Indiana – the Mitchell Plateau and the Muscatatuck Plateau. Mitchell is located in southern Indiana, extending from eastern Owen County southward towards the Ohio River in Harrison County. Muscatatuck is found in southeastern Indiana. Both were developed by limestone with Mitchell created by Mississippian limestone and Muscatatuck on Silurian and Devonian age bedrock.
Check out the Indiana Geological Society’s map on the Physiographic Divisions of Indiana to see where they lie.
Why Does Karst Matter?
Caves provide essential habitat for unique plants and animals, some of which spend their entire lives in complete darkness - many of them that would not be able to survive otherwise. With our biodiversity at risk, it is important to be careful above and below our karst regions.
Another important reason to be concerned is due to the fact that these systems carry water from the surface to the underground aquifers where most of our drinking water originates. Almost 25% of the groundwater is located in caves and karst regions. The protection and management of these vital water resources are critical to public health and to sustainable economic development. Once a cave is damaged, its formations and the creatures that live within it cannot be recovered.
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Karst systems are critical environmental resources. In fact, 40% of our drinking water passes through cave and karst systems. According the USGS's Ground Water Resources Program, "the importance of ground-water in complex geologic environments can no longer be overlooked." Karst regions have unique features that control the movement and access to ground water and watersheds. Development in these areas is vulnerable to increased chances of contamination and lack of availability of quality drinking water in the future.
What is The Nature Conservancy Doing?
In 2003, TNC’s Indiana Chapter purchased 213 acres of land above the Lost River cave system in Orange County. The Lost River flows down the cave drains 48 square miles of watershed above ground. Chemical pollution, soil run-off and failing septic systems from the area could easily contaminate the water unless the area was protected. The Conservancy hopes that they – along with the U.S. Forest Service and the Indiana Karst Conservancy – will be able to reduce pollutants by protecting what’s on top by limiting access to the property and not allowing new septic systems to be installed. In doing so, The Nature Conservancy will be able to better protect viable populations of cave restricted species and maintain water quality and quantity supplying the karst system.
Interesting Facts and Maps
• Karst habitats comprise 20% of the Earth's land surface.
• One-quarter of the world gets its freshwater from karst aquifers.
• Scientists estimate 60,000 species of cave-dwelling animals worldwide, with 10% in North America.
• An estimated 90% of subterranean life has not yet been described.
• Deforestation, land developments and vandalism are just a few threats to subterranean species.
From TNC’s Subterranean Conservation website
•Caves formed by the "carbon dioxide cascade" are also called solutional caves.
•Troglobites have developed unique characteristics so they can devote their time to finding food. Most are white or pink in color as they lack pigments and many are “blind” as they have no or poorly developed eyes. Troglobites are usually long in length (compared to their above ground relatives) and can go without food for extreme periods of time
•Speleothem is the general term for any mineral deposit or formation found in caves. The most common are stalactites (which hang from the ceiling) and stalagmites (that grow up from the ground).
Cave Ethics & Safety Tips
Karst landscapes and caverns are wondrous but delicate ecosystems. While visitors and cavers are encouraged, special consideration must be taken when down below. The Leave No Trace organization offers some great advice as does the American Cave Conservation Association.