Indiana Caverns is part of the Binkley Cave system near

Corydon, Indiana Corydon is a town in Harrison Township, Harrison County, Indiana, Harrison Township and the county seat of Harrison County, Indiana, located north of the Ohio River in the extreme southern part of the state. Corydon was founded in 1808 and serve ...

History

In 1918, an 81.5 acre farm less than a mile south of Corydon was purchased by Arvel H. Miles. A

sinkhole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are also known as shakeholes, and to openings where surface water ...

entrance to Binkley Cave opened on the farm at some point prior to a set of explorations in the 1930s. In 1944, the farm was purchased by Harvey Binkley, for whom the cave is now named. Most of the exploration of the cave has been done by the Indiana Speleological Survey. In 2010, Shane Myles and Tim Pride discovered an area now called Blowing Hole Boulevard. Blowing Hole Boulevard's west end is an eighty-five-foot tall room called Big Bone Mountain, named for several sets of animal bones found in the room. Subsequent excavations by the

Indiana State Museum The Indiana State Museum is a museum located in Downtown Indianapolis, downtown Indianapolis, Indiana, United States. The museum houses exhibits on the science, art, culture, and history of Indiana from prehistoric times to the present day. His ...

have determined the bones to originate from

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

Ice Age animals. In 2012, the Indiana Speleological Survey began investigating a possible connection between Binkley Cave and nearby Blowing Hole Cave. A passageway thought to connect the two caves was partially blocked by breakdown rock, but dye testing and smoke bombs showed an air and water exchange between the two caves. Digging on both sides allowed cavers in both caves to shake hands through the rocks. This disproved the idea that the two caves were separate; they are now proved to be one cave. This connection made the Binkley Cave system thirty-five miles long - solidifying it, perhaps permanently, as the longest cave in

Indiana Indiana ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Michigan to the northwest, Michigan to the north and northeast, Ohio to the east, the Ohio River and Kentucky to the s ...

. Development of Indiana Caverns began on June 1, 2012; the cave opened to the public on June 15, 2013. The Indiana Speleological Survey continues to explore Binkley Cave. Through the use of color dye in waterways, two local springs have been identified as the final destination of two yet unexplored cave passageways. Exploration of these waterways would add several miles to the cave's explored length. As of the end of 2015, the surveyed cave length was 42.57 miles with the potential for at least ten miles to be discovered in the distant future.

Geology

The Indiana Caverns portion of Binkley Cave is almost entirely located in

St. Louis Limestone The St. Louis Limestone is a large geologic formation covering a wide area of the midwest of the United States. It is named after an exposure at St. Louis, Missouri. It consists of sedimentary limestone with scattered chert beds, including the ...

, which is a thinly bedded

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

of Mississippian origin. St. Louis Limestone includes beds of

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...

and

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

(the chert is showcased on the tour).

Brachiopods Brachiopods (), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the fron ...

and

coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...

are apparent in the rock on the show tour. Binkley Cave is a

solutional cave A solutional cave, solution cave, or karst cave is a cave usually formed in a soluble rock like limestone (Calcium carbonate, with chemical formula ''CaCO3''). It is the most frequently occurring type of cave. It can also form in other rocks, incl ...

formed from the dissolution of limestone by underground streams containing

carbonic acid Carbonic acid is a chemical compound with the chemical formula . The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion ...

. The water takes the path of least resistance by running along the faults, fractures, and bedding planes of the limestone. The thinly bedded St. Louis limestone can be quite

fissile In nuclear engineering, fissile material is material that can undergo nuclear fission when struck by a neutron of low energy. A self-sustaining thermal Nuclear chain reaction#Fission chain reaction, chain reaction can only be achieved with fissil ...

, meaning it is weakest along straight planes. This weakness along the planes helped lead to breakdown events after the cave's initial formation, leaving behind flat surfaces on the ceilings and walls.

Calcium bicarbonate Calcium bicarbonate, also called calcium hydrogencarbonate, has the chemical formula Ca(HCO3)2. The term does not refer to a known solid compound; it exists only in aqueous solution containing calcium (Ca2+), bicarbonate (), and carbonate () io ...

is carried into the cave by drips of water. When the slightly pressurized calcium bicarbonate hits the air of the cave, the

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

is released, and the

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

precipitates out of the water. The

, in the form of the mineral

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

, a solid, crystallizes onto the bottoms and sides of existing

stalactites A stalactite (, ; , ) is a mineral formation that hangs from the ceiling of caves, hot springs, or man-made structures such as bridges and mines. Any material that is soluble and that can be deposited as a colloid, or is in suspension, or is ca ...

stalagmites A stalagmite (, ; ; ) is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically composed of calcium carbonate, but may consist o ...

, helictites, and sheets of

flowstone Flowstones are sheetlike deposits of calcite or other carbonate minerals, formed where water flows down the walls or along the floors of a cave. They are typically found in "solution caves", in limestone, where they are the most common speleothe ...

to grow the formations over time. Other minerals are brought into the cave by flowing of water to create white, red, tan, and gray colors on the formations and walls. St. Louis Limestone is primarily made of calcite, but is also known to contain

magnesium sulfate Magnesium sulfate or magnesium sulphate is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, soluble in water but not in ethanol. Magnesi ...

manganese dioxide Manganese dioxide is the inorganic compound with the formula . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for is for dry-cel ...

ferric oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula . It occurs in nature as the mineral hematite, which serves as the primary source of iron for the steel industry. It is also known as red iron oxide, especially when us ...

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...

, dolomite, and

aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...

. On the show tour, deposits of

, and

are apparent. The top portion of the St. Louis Limestone layer through which the tour goes includes the Lost River Chert Bed, a layer of rock containing sheets of

, a

siliceous Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant ...

rock, which is also apparent on the cave tour.

Ice Age

Because of the presence of

fauna bones in the cave, it is believed that the top of the Big Bone Mountain room once featured a large natural opening that both opened and closed during the

era.

Carbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was ...

on three sets of bones in the cave indicate that the animals entered the cave circa 38,000 years BP, which would have been 17,000 years prior to the last glacial maximum. During the last

glacial maximum An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

, the glaciers of the

Wisconsin glaciation The Wisconsin glaciation, also called the Wisconsin glacial episode, was the most recent glacial period of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the Cordilleran Ice Sheet, which nucleated ...

extended past present-day

Indianapolis Indianapolis ( ), colloquially known as Indy, is the List of capitals in the United States, capital and List of municipalities in Indiana, most populous city of the U.S. state of Indiana and the county seat of Marion County, Indiana, Marion ...

. The earlier Illinoian glaciation extended glaciers all the way to the Ohio River, but stopped short of the Crawford Upland as the Mitchell Plain, in which Indiana Caverns sits. Almost all of Indiana's caves exist along a thin area between Bloomington and Harrison County, which was never glaciated. This information is based on private correspondence between Indiana Caverns and the Indiana State Museum.

Species

The species identified by the Indiana State Museum so far are: * Flat-headed peccary, which is shown on the tour and are found in the cave in very large numbers. * The first known case of

northern flying squirrel The northern flying squirrel (''Glaucomys sabrinus'') is one of three species of the genus '' Glaucomys'', the only flying squirrels found in North America.Walker EP, Paradiso JL. 1975. ''Mammals of the World''. Baltimore: Johns Hopkins Universit ...

in the state *

Southern flying squirrel The southern flying squirrel (''Glaucomys volans''), also known commonly as the assapan, is a species of squirrel in the family Sciuridae. ''G. volans'' is one of three species of flying squirrels found in North America. It is found in deciduou ...

Porcupine Porcupines are large rodents with coats of sharp Spine (zoology), spines, or quills, that protect them against predation. The term covers two Family (biology), families of animals: the Old World porcupines of the family Hystricidae, and the New ...

Passenger pigeon The passenger pigeon or wild pigeon (''Ectopistes migratorius'') is an bird extinction, extinct species of Columbidae, pigeon that was endemic to North America. Its common name is derived from the French word ''passager'', meaning "passing by" ...

Barred owl The barred owl (''Strix varia''), also known as the northern barred owl, striped owl or, more informally, hoot owl or eight-hooter owl, is a North American large species of owl. A member of the true owl family, Strigidae, they belong to the genus ...

Vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...

Garter snake Garter snake is the common name for small to medium-sized snakes belonging to the genus ''Thamnophis'' in the Family (biology), family Colubridae. They are native to North America, North and Central America, ranging from central Canada in the no ...

* Southern red-backed vole * Black bear There are also bones of unknown species from a bird, a frog, a fish, and a shrew.

References

External links