Dixon Cave EarthCache

Dixon Cave is a natural cave opening formed when a sinkhole eroded and collapsed into the cavern below. Dixon Cave is closed to exploring for the protection of bats.

The region we now call south central Kentucky was 10 degrees south of the equator and submerged beneath a warm and shallow sea. For 70 million years, sediments including calcium carbonate shells from sea creatures accumulated on the ocean floor ultimately depositing 1,200 to 1,400 feet of limestone.

A river, flowing into the ocean from the north, deposited 50 to 100 feet of sand and silt, creating a layer of sandstone and shale over the existing limestone.

The sea level began to drop and the continent began to rise, exposing the layers of limestone and sandstone. Forces within the earth caused the surface to buckle and twist, causing tiny cracks between and across the layers of limestone and sandstone. At the same time, river systems as we know them developed on the surface.

Forces of erosion had left a sandstone-capped ridge (insoluble to water) above the Green River. Beyond this ridge to the south there is a limestone plain called, "Pennyroyal Plateau," filled with sinkholes. When it rained, water seeped through the sinkholes into the tiny cracks and crevices within the limestone. Combining with carbon dioxide (and thus becoming a weak acid), the water slowly made its way through the limestone toward the Green River. Ultimately, on its journey toward the river, the water traveled under the sandstone-capped ridge by dissolving away larger and larger passages from its limestone bed, in the process forming an intricate and interconnected river system.

As the Green River continued to cut deeper into its bed, the water table continued to drop. To keep up, new underground drains formed in the limestone bed, creating new channels beneath the original ones. Water drained from the higher passages, leaving behind air-filled passageways that visitors recognize—Dixon Cave.

At Mammoth Cave National Park in central Kentucky, bat-friendly cave gates have started to rectify a problem that began decades ago when the cave was mined for nitrates and became a tourist attraction.

Discovered by colonists in the 1790s, Dixon Cave's bat guano-enriched sediments provided a valuable source of nitrate, tons of which were removed for use in gunpowder for the War of 1812. About that time, sightseers began touring the cave. An 1810 newspaper article refers to bats being "crowded so close that they resembled a continued black cloud." When Yale biologist Benjamin Silliman, Jr., visited in 1850, he estimated them by the millions. But by June 1996, when park researchers invited BCI's Tuttle to accompany them into Mammoth Cave, evidence was scarce. On cave walls and ceilings, scientists discovered reddish marks where roosting bats had stained the rock. Scientists also found and dated remains in many parts of the cave.

Analysis of bones indicated primary use by hibernating Indiana bats, with some gray bat summer roosts in warmer rooms. Using a formula of 300 Indiana bats per square foot of roosting space, researchers estimated that as many as 20 million Indiana bats could have used these passages in the past.

Dixon Cave’s relationship with Indiana bats is especially important because they, along with gray bats, are endangered. This status means that they are accorded special protection under laws enforced by the U.S. Fish & Wildlife Service and ensures that habitats used by these animals receive protection. Areas occupied by the endangered species may also be seasonally or permanently closed to visitors to prevent disturbance.

USFWS surveys in 1993 showed that Indiana bat populations nationwide had declined 41 percent during the previous decade. Indiana bats inhabit riparian forests in New England and the Midwest in summer, in winter they seek caves with stable temperatures between 37 and 45 degrees Fahrenheit. Individuals often rest in the same place on the same cave wall winter after winter. Most Indiana bat hibernacula are located in Kentucky, Missouri, and Indiana, where only 3 percent of all caves provide suitable conditions. About 85 percent of the Indiana bat population now winters in just seven caves, several of which are located within Mammoth Cave National Park.

As recently as 1947, Dixon Cave sheltered several of thousands wintering Indiana bats. Five years ago, at the urging of BCI and the USFWS, park managers designed and installed bat-friendly gates at the entrances of Dixon Cave. Since then, the wintering populations have increased. Dixon Cave hosts a fairly stable winter population of 5,500 Indiana and 500 gray bats.

Dixon Cave is off limits for caving, exploring, walking inside, etc. You could be charged a fine for entering the cave. Any pictures from inside or near the entrance will be deleted.

To get credit for this EC, post a photo of you on the viewing deck with the cave entrance in the back ground at the listed coordinates just like in the picture above and please answer the following questions.

1. How wide and long is the opening of the cave entrance?

2. Estimate the depth of the cave from the viewing deck.

3. What do you think caused the collapse of the sink hole?

This is a Mammoth Cave National Park approved earthcache. Always ask for permission when setting up any geological site as an earthcache.

This is a Mammoth Caves National Park approved EarthCache site. The information here is from the Mammoth Caves National Park website. Thanks to those who enjoy EarthCaches and keeps Cav Scout placing them.

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Do not log this EC unless you have answered the questions and have a picture ready to post! Logs with no photo of the actual cacher logging the find or failure to answer questions or negative comments will result in a log deletion without notice. Exceptions will be considered if you contact me first (I realize sometimes we forget our cameras or the batteries die). You must post a photo at the time of logging your find. If your picture is not ready then wait until you have a photo.

Sources of information for the EarthCache quoted from the Mamoth Caves National Park website. I have used sources available to me by using google search to get information for this earth cache. I am by no means a geologist.. I use books, internet, and ask questions about geology just like 99.9 percent of the geocachers who create these great Earth Caches. I enjoy Earth Caches and want people to get out and see what I see every time I go and explore this great place we live in.