From scenic Tennessee, the Goddard hurtled northward in the summer of 2022 – destination: Michigan, to visit Nancy’s sisters and their families. On the way, we stopped to visit a couple of national parks in Kentucky and Indiana. We’d visited Mammoth Cave, located in central-west Kentucky, some years ago (Nancy’s way into caves – like, way), but it was time for a return visit. We made not one, but two trips underground to visit different parts of the cave; on another day, Gunther also joined us for a fun hike above the surface of the earth.
Mammoth Cave’s story begins, as do so many of the tales recounted in this blog, 350 million years ago when this part of present-day Kentucky (and most of the rest of the current United States) was covered by a vast inland sea. Corals and shell-bearing organisms produced calcium carbonate (CaCO3), which precipitated out of the seawater to fall on the seabed below. There were a lot of corals and shellfish: the CaCO3 their bodies created gradually accumulated to develop a 450-feet-deep layer of sedimentary limestone at the bottom of the sea.
In the ensuing hundreds of millions of years, the sea retreated and the limestone was covered by more layers of shale and sandstone. Mammoth Cave is the world’s biggest example of a solution cave, meaning that it was created when rainwater percolated downward and picked up naturally occurring carbon dioxide in the air and soil to became very weakly acidic. Ten to 15 million years ago, the percolation dissolved enough of the limestone to allow greater volumes of water to flow through the crevices. The force of the Green River took it from there, cutting through the highly erosional limestone using both water pressure as well as a mild acidity present in the river. The passages of the cave closest to the surface are the youngest in the system: only about 2 million years old. While the protective layer of harder shale and sandstone is keeping the brakes on vertical erosion from rainwater, the Green River is still creating more Mammoth Cave under the earth today.
Our guide, National Park Service Ranger Matthew, a retired schoolteacher, welcomes the Star Chamber Tour group to the Historic Entrance of Mammoth Cave. Matthew is a retired schoolteacher. The tour, which started at 6 PM, allowed us to visit the cave as those who entered the cave a hundred years ago did: with oil lanterns. The Star Chamber tour is two miles long and lasted 2 1/2 hours; it was nearly full dark when we emerged from the cave. Ranger Quentin is behind the shrub in the center of the photograph; we talked with him a bit during the tour and he shared that he’d just been informed that he’d been named a full-time NPS ranger. As anyone who has spent time in national parks can imagine, it’s a very competitive position; Quentin is a native of the Cave City area, so it had to be especially rewarding.
Native Americans lived in the area around Mammoth Cave for thousands of years, exploring the cave and using it for mineral extraction. They entered the cave through what is now known as the Historic Entrance, and explored at least 14 miles of the system using only the flame from burning torches for light. Evidence shows that Native Americans stopped using the cave about 2,000 years ago, and the caverns were unknown for more than 200 years.
This is the Historic Entrance to the cave, accessed by a long stairway (the stairs seen at the right of the image above). There are about 30 entrances to the cave system, some of which are just small holes barely large enough to squeeze through.
Local history holds that the first European-American entered the cave in the late 1790s. A young boy named John Houchins was hunting black bear (no longer found in the area) and inadvertently came across the huge hole in the ground that is now the Historic Entrance.
During the War of 1812, the cave’s … significant … deposits of guano (there are 13 known bat species in the park, but not all use the cave) served our nation as a source of saltpeter, a component of gunpowder. Some of the wooden assets used in the guano mining operations are still to be observed in the cave, thanks to its cool and humid environment (54 degrees and 87 percent humidity, all day, every day, all the year round).
The site became a local tourist attraction but, because of the area’s remoteness, didn’t see much out-of-state visitors for many decades until the automobile was developed and popularized. The property was privately owned by different interests through the years, all of which conducted tours of the underground passages, until concern about preserving the caverns’ natural resources resulted in Mammoth Cave National Park being established on July 1, 1941. It is the country’s 26th national park. In its first year as a national park, Mammoth Cave saw about 58,000 visitors; we were two of about 663,000 people to visit the park in 2022.
True to its name, Mammoth Cave is pretty big: in fact, it’s the longest cave system in the world and fully twice as long as the next-longest system. Mammoth Cave is currently mapped to include more than 400 miles of caverns (the entire state of Colorado is 380 miles wide), and the scientists believe that as many as 600 miles of caverns remain to be discovered and mapped. The system has been likened to a bowl of spaghetti, with passages intersecting and moving up and down multiple levels .
Understandably so, flashlights and flash photography were forbidden on the cave tours so the photos I was able to take are terrible because the only light available came from lanterns (on the Star Chamber Tour) or electric lights along the cave passages (on the River Styx Tour). However, some of the photos give a sense of scale to the caverns. Much of the present-day caverns are completely dry – the river water that carved them disappeared quickly into deeper caverns many years ago – so there’s no dripping water to create stalagmites and stalactites, along with other formations familiar to spelunkers. To be honest, although there are some beautiful formations to enjoy, for me most of Mammoth’s impressiveness – and there is plenty of that – comes from its sheer size. Mammoth Cave is big, and it’s dark. I remember a ranger’s tale from the first time we visited the national park: in the mid-1930s, before the park was managed by the NPS, the mummified body of a Native American (who’d lived before Columbus reached the New World and was killed when he was struck by a large falling rock) was discovered on a ledge in one of the caverns. By that time, hundreds of guided tours had passed by the body and all of the people – numbering in the thousands, at least – in all of the tours were unaware that they were passing by the mummy, which was only a few feet above their heads. It was just too big, and too dark, in Mammoth Cave to know about the mummy until someone happened to come across it.
The pandemic limited the number of tours available; some of the tours that Nancy and I went on during our first visit weren’t available at the time of our visit in July (mostly because of a shortage of National Park Service rangers trained to lead the tours). However, we enjoyed the Star Chamber Lanternlight Tour one evening, as well as the daytime River Styx Tour on another day.
The cave’s corridors vary greatly in size: some passages require visitors to walk sideways in order to pass through, and other caverns are wide enough to accommodate a Boeing 747 jet (I didn’t see any aircraft on either tour, but it was pretty dark).
We saw this formation, called the Giant’s Coffin, on both of our tours (which shared a bit of the same trail). Located 175 feet below the surface, the Giant’s Coffin is a limestone nugget measuring nearly 50 feet long and 20 feet tall, and weighing a thousand tons. The rock separated from the limestone wall behind it sometime in the distant past; imagine the sound it made when it fell. Our NPS ranger guide is in the shadows at the left of the photo; if I remember right, she’s standing perhaps 50 feet in front of the Giant’s Coffin.At one point on the Star Chamber Tour, Ranger Matthew asked us to place our oil lanterns in a row on the cave floor. He and Ranger Quentin then extinguished all of the lamps and used a flashlight to guide their way behind a rock wall, leaving us in total darkness (he’d mentioned they’d do this beforehand; they didn’t just sneak off and leave us). If you’ve never been in a completely darkened cave, you’ve never known true darkness: the absence of all light. Even being outside on a moonless night, well removed from city lights, isn’t the same because there’s still starlight to provide some illumination, however feeble. It’s a common occurrence on cave tours, this extinguishing of all artificial light, but it never fails to strike some primeval chord – to not be able to see your hand in an inch in front of your face, let alone across the room. It also gives one a better appreciation for those early explorers: modern spelunkers carry all sorts of redundant sources of light – there are only so many torches or lanterns one can carry.This picture is from the River Styx tour, which was illuminated by electric lighting for most of the 2 1/2-mile trail. The tour includes a visit to the River Styx, an underground tributary of the Green River, but flooding in the cave in 2010 destroyed the electrical system along that part of the tour. We needed battery-powered lanterns to continue. (Incidentally, as of this writing in August 2023, the River Styx tour isn’t being offered – I wonder if the electrical system is being repaired.) Notice the scallop-shaped carvings in the rock ceiling above: those indicate the direction and velocity of the flow of water eroding the rock. Larger scalloped features (a meter or more wide) mean that the water was moving only a few centimeters per second, and smaller scallops indicate that the water was flowing in meters per second.This is a pool known as the Dead Sea, created by the Green River. It’s about 15 feet below the point at which this picture was taken. Artificial lighting next to the river shows some details of the water erosion. The occasional blind cave fish or blind crayfish can be observed in these waters; alas, they were not to be observed on this occasion.And here is the River Styx, which looks a lot like the previous photo of the Dead Sea. Bur remember, friends, that the River Styx is but a tributary of the Dead Sea’s Green River.Here was another highlight of the River Styx Tour: seeing the incredible Mammoth Dome. Known in spelunking terms as a “vertical shaft,” Mammoth Dome was created when water followed the law of gravity to flow straight down vertical crevices in the limestone. The erosional activity results in shafts that, at Mammoth Cave, measure 30 feet or more. In Mammoth Dome’s case, that resulted in a vertical shaft measuring 190 feet in height. An impressive metal staircase provided a lot of viewpoints to see the dome (there’s still a lot of climbing to do; see the top of the staircase at the top of the photo).
River Styx Spring Trail
While there are a number of different tours available for anyone wanting to explore the bowels of the earth at Mammoth Cave National Park, it also features more than 80 miles of above-ground trails. Gunther joined Nancy and me for a hike on the River Styx Spring trail, which provided for some great views of the Kentucky countryside.
Because we spent most of our lives in Colorado, neither Nancy nor I are familiar with vistas like this: hardwood forests as far as the eye can see. Mammoth Cave National Park currently encompasses 53,000 acres, or about 80 square miles; while it’s justifiably most famous for its subterranean caverns, there are plenty of opportunities for above-ground adventures.We encountered this whitetail fawn near the trailhead of the River Styx Spring trail. Its mom was less than 10 feet away. It must be pretty used to seeing humans; I don’t think I’ve knowingly ever been this close to a young fawn before. The speckled pattern on a very young deer’s sides act as a kind of camouflage, helping it to blend in with the sun-dappled undergrowth in forests. I would think that fawns would also be predominantly grass-green instead of brown, but I suppose evolution knows what it’s doing.The River Styx Spring Trail passes by a historic cemetery that is the final resting place of Stephen Bishop, one of the first non-Native-American explorers of the cave system. Bishop’s story is very interesting: in 1839, the Mammoth Cave estate, along with several Black slaves including Bishop, were sold to Dr. John Croghan for the amount of $10,000 (about $275,000 today). Croghan began to explore making improvements to the property’s tourism assets, like the hotel, and Bishop began to explore the underground caverns. A gifted spelunker and popular guide, Bishop also named many features within the cave – including the River Styx. In 1844, he published a detailed map of the cave system; the map would remain the primary guide to the cave for 40 years. The map contained about 10 miles of passages within Mammoth Cave, half of which Bishop discovered himself. Croghan envisioned using part of the interior of the cave as a tuberculosis treatment facility – some of the stone housing built for tuberculosis patients in 1841 is still standing along present-day tours of the cave – thinking that the cave’s environment would provide helpful results, but the treatment failed. In fact, all 10 of the tuberculosis patients either died in the cave or later after they exited the cavern. Further, the widespread disease would claim the lives of both Croghan and Bishop: Croghan died in 1849, and had stipulated in his will that Bishop would be declared a free man seven years after Croghan’s death. Bishop did enjoy a few months of freedom beginning in 1856, but tuberculosis claimed his life in the summer of 1857. He was buried on the Mammoth Cave grounds but his grave remained marked only by a cedar tree until 1881, when a second-hand tombstone (it was originally intended for a Civil War veteran’s grave but the family never claimed it – explaining the appearance of a sword and flag on the headstone) was inscribed and placed at Bishop’s gravesite. The date of his death is incorrect on the headstone.Look at this rock Gunther found on the hike! Look at it! In addition to seemingly endless hardwood forest vistas, neither Nancy nor me nor Gunther were used to the high temperatures combined with the high humidity of central Kentucky in July. This part of central Kentucky gets about 50 inches of rain each year.Here is the terminus of the River Styx Spring hike: a view of the water feature we’d seen only underground. Presumably any fish or crayfish in this part of the river have the gift of sight.
A couple of birds
I’ll close with a couple of bird photos from our campground in Cave City, which is a little more than 10 miles from the Mammoth Cave National Park visitor center. This is, of course, an American robin (Turdus migratorius) that lit upon one of our campground’s picnic tables. They’re common birds but always fun to watch. They’re found throughout the United States but breed in Canada.Here was a new bird to me: an indigo bunting (Passerina cyanea). They’re found in the eastern United States and the southern part of the country. The scientists discovered that indigo buntings, which, like many other species migrate at night, and navigate using the stars. The experiment involved placing some of the birds in a planetarium. The birds adjusted their orientation in the room as the projected stars above changed position. Their remarkable blue color is due to microscopic structures in their feathers that reflect and refract blue light – very similarly to why the sky above the bunting looks blue.
There are a number of NPS sites that prominently feature caves including a couple, perhaps improbably, in South Dakota, which we visited a number of years ago (did I mention that Nancy likes caves?) However, none are bigger than Mammoth Cave in Kentucky, and, thanks to the Green River, it’s getting bigger every day.
Thank goodness we were done with caves for the year.*
Tales of The Goddard 
The bird pictures here and in your previous post from McDougal Park are amazing
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Thanks very much — I really appreciate your kind words!
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