Karstic Treasure: Mammoth Cave National Park (Mammoth Cave, KY)


Although our travel plans were going to be largely confined to Tennessee, how could my wife and I not pass up Mammoth Cave National Park in South Central Kentucky? The first I ever heard of it was during a nature program on PBS, described as the largest cave system in the world. Its size is so immense that it would still be larger than the next two largest systems combined by 100 miles.

Odd that the name uses the grammatical singular when in fact Mammoth Cave is comprised of many interconnected spaces in the limestone: sink holes, tubes, passageways, canyons, shafts, fissures as well as caves. This combination of limestone and excavation is characteristic of karst. A geology map shows that almost a quarter of Kentucky is karstic.

Mammoth was our first overnight stop after picking up a car at Nashville Airport and driving two hours north. The park is surrounded by the famous rolling hills of Kentucky. As we got closer, the road cuts in some areas bared telltale limestone layers. The soil has a rusty-reddish color.

We checked in to the Mammoth Cave Hotel, located within the national park boundary. Our accommodation was a standalone cabin, one of ten that form an arc along the property’s edge, which was rustic but comfortable. The hotel was undergoing an extensive renovation and construction until November, so the main building and eating facilities were closed behind chain-link fencing, except for the outlying cabins. In the evening, there was the musical thrum of cicadas and tree frogs. The park’s visitors center is only a short walking distance away.

On our only full day here, we wanted to maximize our cave experience. To that end we decided to take the longest tour called Grand Avenue tour. At almost 400 surveyed miles and counting, Mammoth was not going to feel as if we had trod on it at all. We had a terrific guide in ranger Rick Thomas, who was so knowledgeable about the cave and its history, told interesting stories and cracked bad jokes (“There’s nothing lower than cave humor,” he said proudly). As a federal employee, he was obliged to forewarn everyone on the tour, all 69 of us, that the fast-paced walk of roughly four hours, four miles and almost 700 steps over uneven terrain would be taxing. He also had to mention that in an emergency, it would take a very long time to get anyone to a hospital. No one budged. The last time my wife and I were ‘intimidated’ by a park employee (the Fiery Furnace walk at Arches National Park), we to this day regretted having changed our minds. Not this time.

The usual speleotherms of stalactites, stalagmites and such, of wet cave environments were scarce, but there were plenty of gypsum accumulations (in the form of blisters and flowers) typical of dry caves, compliments of a hard layer of sandstone that acts like an almost impervious cap over the limestone underneath. These gypsum deposits are unimaginably slow growing at a rate of a dime’s thickness per century. One impressive example is Last Rose of Summer along Cleveland Avenue. There are prolific gypsum blisters in The Snowball Room, because they look like snowballs on the ceilings and walls.

Last Rose of Summer on Cleveland Avenue

Last Rose of Summer on Cleveland Avenue

Snowball Room

Snowball Room

The long tour passage was the result of underground streams and rivers that have long since drained into the Green River, which over a period of time has carved ever deeper into the limestone layers, leaving the upper limestone layers dry. Parts of the tour were like walking through a long elliptical tunnel, sometimes bordered by smooth walls or flat ceilings, other times littered with limestone fragments, including huge slabs lying at oblique angles. Other sections were like underground slot canyons, at several points narrow enough that you had to angle your body to get through, an experience not unlike in the Southwest. We had to walk single-file for roughly a mile. There were also cavernous rooms where the group could gather around Ranger Rick to hear another story or lecture. At tour’s end, we got to see the spectacular Frozen Niagara, an unbelievable mass of flowstone deposits that require a steep descent of some forty stairs to see top to bottom. Looking up from the pit gives you a view of why this area was so named. It looks like frozen water cascading over an enormous U-shaped ledge (top image).

Ranger Rick delivering one of his talks

Ranger Rick delivering one of his talks

Ascension

An elaborate stairway and ramp system winds around Frozen Niagara

An elaborate stairway and ramp system winds around Frozen Niagara

As it turned out, the tour really was exhausting like Rick warned. We were bushed by its end, but what an experience!

Mammoth Cave National Park
1 Mammoth Cave Pkwy
Mammoth Cave, KY 42259
270. 758.2180

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Carlsbad Caverns National Park (NM)


Neither of us has ever been to Carlsbad Caverns. We set aside three whole days to explore it since its remoteness in the southeast corner of New Mexico makes it unlikely we’d ever have an opportunity to return. This remoteness is the reason that, although its wonders are many, far fewer visitors show up than at the more popular national parks. It is located in an almost featureless desert, indistinguishable from much of west Texas, but possessing oil deposits underground that supports much of the local economy. You’re more likely to hear a Texas drawl here than not.

The Big Room, Kings Palace, Queen’s Chamber, Papoose Room and others, “rooms” all named by the 16-year-old Jim White who purportedly first discovered the caves, are wondrous to behold. The word cavernous seems to describe The Big Room aptly, an immense chamber big enough to hold six football fields. An almost level, paved walkway allows everyone to enjoy The Big Room. For those so inclined, there are slightly to much-more-strenuous ranger-guided tours that vary from mild climbing, scrambling (sometimes on rocks that seemed coated with candle wax), rope climbing and going through claustrophobic tunnels barely large enough to squeeze through.

Millions of years ago, at a time when the area was more tropical than at present, an ancient reef was transfigured when hydrogen sulfide gas rose from the oil deposits below and mixed with the oxygen in the water from above. The resulting sulfuric acid carved out the caverns in limestone. The decorations we see today—stalactites, stalagmites, draperies, popcorn and the rest (collectively called speleotherms)—are the result of the “normal” process of deposition built up over time by calcium-rich droplets of water. Artfully designed by a Hollywood lighting director many years ago, the major rooms are beautifully illuminated by artificial lights, effects that Jim White never saw that he would likely denounce as removing the “mystery of the caves.” Our favorite tour was the Kings Palace which showcases rooms so elaborately embellished with cave decorations that the word opulence comes to mind.

These typify the speleotherms in Carlsbad

These typify the speleotherms in Carlsbad

The other attraction here are the Mexican free-tail bats that fly out from the so-called Natural Entrance about an hour before sunset. The Park Service has installed some high-tech equipment within the cave that can detect when the bats are ready to emerge; it translates the bats’ echolocation sounds to frequencies that humans can hear. At first, over the amphitheater’s PA system, there was a single click or pop; within seconds, there were so many clicks that it sounded like microwave popcorn. Shortly thereafter, the bats emerged in waves, rather than all at once. No photography (nor turning on of electronic equipment of any kind) was allowed during the bat flight. They disturb the bats as they fly out. The park ranger told us that the more impressive sight is the bats’ return an hour before sunrise, when they swoop back (literally dive bomb) into the cave at about 25 mph or more. On the morning of our departure, we rose early and got to the amphitheater when it was still dark. Try as we might, we couldn’t see the bats, even silhouetted against a lightening sky. But we did hear zipping sounds in the air around us, like bullets whizzing by, which we could only assume were the bats returning so fast that we couldn’t see them. A thickening fog also likely obscured our vision somewhat.

Bats fly in and out of the Natural Entrance

Bats fly in and out of the Natural Entrance

The video below from YouTube shows a much larger swarm emerging from the cave than we witnessed. Bat populations ebb and swell, depending on the season.

The closest town with full amenities is Carlsbad City, some 25 miles away from the park entrance. However, right at the intersection of the park road with Highway 62/180, there is a Rodeway Inn and a few services, including an RV park, gas station, convenience store and restaurant. It’s called White’s City, where we chose to stay, only about 6 miles from the visitors center. It’s much more convenient, but which seems to be on most travel sources’ lists of not-recommended places to stay. Our own experience here was not ideal, but not terrible either. Eating at the same restaurant for breakfast and dinner quickly got old.