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It would be strange to be in Kentucky and not stop at Mammoth Cave National Park, after all it is the world’s largest cave system. Even though it has been mapped at over 350 miles long, all of the known cave fits well within the Park’s 53,000 surface acres. Through the ages, as slightly acidic water dissolved the limestone, the water table has slowly been sinking lower and lower. The cave now has at least six levels that snake under each other. While the vast majority of the cave is dry, a river runs through the lowest levels of the cave system, eroding limestone and enlarging the cave every day.

The water in the bottom of the cave is at the same level as the Green River which runs through the Park. Just as the water in the cave has been eroding its way downward, so too has the Green River cut deeper through the limestone. If you were to hike along the Green River and look at the limestone wall, you would not be above Mammoth Cave, instead the majority of the cave would be above you!

Mammoth Cave and the hundreds of other caves in the area were all formed in the same layer of limestone that was laid down at the bottom of an ocean 350 million years ago. We didn’t see any ourselves—we really didn’t have time to stop and examine the rock during the tours—but we did see some photos of fossils in the walls of the cave. In 70 or so million years the limestone accumulated to a depth of 500 feet. On top of the limestone layer is a thick and relatively impermeable layer of sandstone. The sandstone forms a cap over the limestone that is mostly responsible for keeping water out of the cave system, which makes Mammoth Cave primarily a dry cave.

Mammoth Cave and the surrounding caverns were not carved by slow mineral-laden drops of water but by rushing, underground rivers. Water was diverted by the top layer of sandstone toward cracks or sinks in the rock layer. As these weak areas collapsed they formed funnels down which water would rush, gouging out deep pits through the limestone. A wonderful aerial photo posted in the Visitor Center shows rolling Kentucky farmland punctuated by these “sinks”. The result of all that flowing water is a huge cave system that mostly lacks speleothems. The cave does have some decorative and delicate formations. During our Grand Avenue Tour we passed by gypsum flowers, stalactites, stalagmites, flowstone, draperies, and soda straws.

Since we had two days to explore the park we signed up for a different tour each day. The Park offers over twelve tours which made it hard to choose, but we finally decided to take the Historic Tour and the Grand Avenue Tour. In the early years, the Park offered a boat tour on the underground river in the lowest levels of the cave; now that would’ve been amazing!

For the Historic Tour we walked into the cave through a natural entrance behind the Visitor Center. Mammoth Cave has over 20 entrances scattered throughout the Park, some of them natural and some of them man-made. Our guide was informative and entertaining; he told stories of the cave’s various explorers, from evidence of Native Americans in the cave 4,000 years ago, up to the formation of the Park in 1941. There is no sign that native people lived in the cave but they left behind many clues of their travels. Footprints, cave paintings, woven sandals, the remnants of cane reed torches and even a few skeletons have been found in the cave through the years. The first mention of the cave by European explorers was in 1798, although it is likely people traveling through the area knew of it long before then.

Mammoth Cave was basically left alone until the War of 1812 increased the demand for black gunpowder. Saltpeter mining operations began in earnest in the caves, leaching nitrates from the bat guano in the soil. The back-breaking work of the leaching vats was carried out by slaves. Even with slave labor the mines were not profitable; after the fighting with England saltpeter mining was discontinued. The next commercial use of the cave was much the same as today, tourism. The first tour for a fee was given in 1816; except for a brief interruption caused by the Civil War, tours have been given ever since.

In the hardscrabble economy of rural Kentucky, having access to a cave meant money, and where there is the potential to make money, people will devise ways of doing so. It was during this period of competition, known as the Cave Wars, that many of the artificial entrances to Mammoth Cave were created. The Cave Wars escalated to the point where competitors vandalized cave entrances, destroyed and removed formations, built walls to block cave access, and defended their caves with guns. Finally, one man’s attempt to find an entrance to the cave on his property—so that he could get in on the tourism market—led to the creation of the National Park.

In 1925, Floyd Collins, a skilled spelunker who had spent many years exploring Mammoth Cave, was trapped when a boulder lodged against his leg. The rescue efforts were broadcast across the country by radio. For several days Floyd was kept alive by food and water lowered down to him. A small cave-in ended contact with Floyd though rescue efforts continued. On the twelfth day, Floyd died from exposure and hypothermia (remember, the cave averages 54 degrees F. with 80% humidity). It took workers another two weeks before they could remove Floyd’s body from the cave. Although Floyd died, his predicament brought the story and wonder of Mammoth Cave to the American people who pushed for the preservation of the cave.

Mammoth Cave National Park was authorized in 1926 and officially dedicated in 1941, but due to World War II it did not actually open to visitors until 1946. In 1972 the connection was discovered that made Mammoth Cave the longest in the world. The vastness of the cave system and its delicate environment led to its designation as a World Heritage Site in 1981 and a Biosphere Reserve in 1990.

Much of the park land was purchased with monetary donations but some of the land was acquired through eminent domain; a fact still resented by some families in the area. The creation of the Park put an end to the Cave Wars since in Kentucky when you own land you own the area under the surface—all the way to the center of the earth.

We were pleased at the way our two tours, the Historic and Grand Avenue, complimented each other. Both tours led us through twisting, narrow passages (like Fat Man’s Misery) and past unique formations (like Frozen Niagara). Each emphasized the immenseness of the cave through cavernous rooms (like Mammoth Dome) and the absolute darkness and impossible silence. Both tours highlighted different aspects of the cave’s story through archeology, geology, anthropology and biology. Lucky us—we were treated to a bat sighting and even a cave cricket! The only aspect of the tours that we didn’t enjoy was the large size of the groups. They both had 80 or more people which prevented close inspection and enjoyment of many of the features of the cave and our guides had to rush us along.

Since most of the cave is dry, and there are few formations which could be damaged, we wonder why the Park doesn’t allow self-guided tours like they do at Carlsbad Caverns National Park. Besides, it’s not a pristine environment down there; they have an elevator (service only, not for guest use) and fluorescent lights which have created unnatural blue-green algae growths. Maybe it’s because of the fee structure at the Park: instead of charging upon admission they charge per guided tour. We really did enjoy the cave, plus we had plenty of time to explore the surface above.

In the late afternoon we meandered along the lovely Heritage Trail. Just before sunset we hiked down to the Mammoth Dome Sink, where water rushes into Mammoth Dome after it rains. We also took in the Nature Trail at Sloan’s Crossing and we hiked out to Sand Cave for a peek at the place where Floyd Collins died. We marveled at the surprising speed of chubby groundhogs, watched deer emerge from the forest for their evening feast of grass, stared down a haughty turtle and spied on frogs who pretended to be invisible.

And here’s a strange factoid that we learned on a tour: the fluffing agent used in Twinkies is made from calcium sulfate, which comes from gypsum. I have tried a Twinkie in the past (although they were strictly verboten in my house as a child) and can’t say that I enjoyed it, but I really dig the idea of eating rocks!

Photos: View our photographs from Mammoth Cave National Park.

Notes: We visited Mammoth Cave National Park on 10/19/07 and 10/20/07.