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Published: January 28th 2012
Astonishing formations in the Frozen Niagara section of Mamouth Cave
I spent most of today in central Kentucky.
This part of Appalachia has unusual geology.
The consequence of this geology on the surface is subtle but unmistakable.
There is no visible water!
Except for the Green River at the center of the region, it has no major streams or lakes.
There are plenty of rolling hills with great views, but no water at all.
The reason lies under the surface.
Central Kentucky contains what geologists call karst terrain
Millions of years ago, the area was a shallow ocean.
Layers and layers of sea creatures and coral were deposited, which hardened into limestone.
An ancient river then dumped tons of sediment into the ocean, which hardened into a layer of shale over the top.
When the land uplifted into the Appalachian Mountains, the shale cracked.
Water, containing carbonic acid, trickled through the cracks and dissolved the limestone to form caves. Central Kentucky
has no surface water because it all drains underground through the caves.
The water ultimately collects into underground rivers, all of which finally drain into the Green River.
New Entrace Chimney
One of several chimneys on the New Entrance Tour descent.
here consist mostly of vertical chimneys carved by water flowing downwards and long horizontal passages carved by the rivers.
As the Green River carves its gorge ever deeper, the underground rivers drop with it, forming ever deeper layers of caves. Mammoth Cave
is the largest of all the caves in this area.
It contains almost four hundred miles of explored passages, making it the longest known cave in the world
The cave is now protected by a National Park
Today I explored a tiny part of it.
I took the New Entrance Tour
, which covers a large number of features in a relatively short amount of time.
It’s led by expert guides, most of whom have worked at the park for years.
It should go without saying that people with a fear of the dark, claustrophobia, or vertigo should probably skip this experience.
The tour starts with a nearly absurd descent.
Before the park, the land above Mammoth Cave was owned by many people.
Kentucky law stated that whoever owned the land also owned the rights to whatever was underneath.
Parts of the cave have been a tourist attraction
Final pit crossing
The final pit to cross on the descent. Welcome to the real life Mines of Moria!
since the 1830s, but people expanded tours greatly in the 1920s.
This led to the Mammoth Cave Wars
, with different groups fighting over who could show what part of the cave (as well as every other cave in the vicinity).
The owner of the land above the New Entrance noticed a large sinkhole on his property.
Water in a sinkhole can only flow to one place, a cave.
Clearing some debris, he found a chimney.
He started exploring, and found the route now used by the tour.
The route goes almost straight down, through a series of vertical chimneys.
The roof of each is called a dome, and the bottom of each is called a pit.
When dry, they look mostly like large cracks.
In the spring when water is flowing, there are thin waterfalls everywhere and the rocks glisten.
I found it all astonishing.
What it took to reach them is another matter.
A long thin staircase wends its way through the chimneys.
In places, it passes through cracks so narrow one needs to walk sideways.
In others, it passes through
Grand Central Station
The Grand Central Station room of Mamouth Cave. The benches are used for a geology presentation.
holes so low one has to duck and descend simultaneously.
In one part, one has to lean to the side to avoid a rock fin.
In several places, the stairs are wet and slippery, and people got dripped on.
Near the end of the descent it crossed a huge pit filled with boulders that seems endless.
This was the one part of the entire tour where I felt I was in Moria (the underground mine from Lord of the Rings
As crazy as the descent is, think of the poor men who built that staircase.
The Park Service had to try three different contractors until they found one that could do the job.
Their normal workday was repairing submarines!
Grand Central Station
At the bottom of the descent, the trail ends at a large open room called Grand Central Station.
It’s one of the passages carved by an underground river.
The guide takes some time at this point to discuss the cave’s geology, pointing out the different rock layers on the walls.
They discuss the history of this part of the cave, and its exploration during the cave
The thin slab of rock in center of the photo is wedged into a crack in the ceiling. It has hung there since this area was first explored a century and a half ago.
The owner was very interested in starting a new cave tour, because his land was closer to the main highway than the existing operators.
The guides also point out the graffiti on the walls, a legacy of the private tours before the park was established (adding one’s own will result in a jail sentence at this point).
From here, we climbed a large pile of boulders at the end of the room.
Rocks fall in caves for two main reasons.
Water seeps in and weakens a ceiling, or two passages occur too close together and the middle rock can’t handle the strain.
The boulder pile here was caused by the latter.
At the top of the climb we entered another room with a perfectly flat ceiling.
In the blue light used here, it almost looked like an upside down lake.
In this room, the guide demonstrated the normal environment of a cave.
After warning people, they turned out the lights.
On the surface, it’s impossible to find a natural environment with no light.
Even at night under cloud cover, a little
The most famous formation in Mamouth Cave, partly because most of the cave has none.
starlight seeps through.
Caves are absolutely dark.
The guides ask people to wave their hands in this environment, and the view did not change in the slightest.
They then asked everyone to stand as still as possible.
Gradually, people perceived a very slight rushing noise, the sound of our breath.
Caves are absolutely silent as well as absolutely dark.
The last part was a demonstration of the limits of human vision.
Human eyes are incredibly sensitive to low levels of light
Some people (including me) are fortunate enough to also be sensitive to low contrasts, so we notice the effect of night shadows against starlight (and a full moon night is like perpetual twilight).
Everyone sees the limits of vision in the absolute darkness of a cave.
The guide pulled out a single match, light it, and held it up.
The entire cave room and the crowd then appeared in the glow.
The effect was less impressive for me than for many people, simply because I see something similar every time I go camping.
After this room, the trail went through a section called
Another room filled with spectacular formations near Frozen Niagra
the New York Subway.
It featured a nearly smooth, oval shaped passage carved by the underground river.
It then passed through another large open room with lots of rocks.
The guide pointed out a hanging rock on the ceiling which has been there since this part of the cave was discovered.
After this room, the view changed dramatically.
The entire cave up to this point featured no formations whatsoever.
The stalactites, stalagmites, and flowstone formations so prevalent in private caves are completely missing in most of Mammoth.
The reason is the shale stone cap.
To create features, water has to drip slowly
for a long period of time.
Each drip deposits a little bit of dissolved limestone, creating the feature.
The shale stone layer means that water in Mammoth cave either flows in large amounts (forming a chimney or a passage) or doesn’t flow at all.
The cap does have places where water filters through, so the last portion of the tour passed through a part of Mammoth that does contain features.
This section is the most visited, and the most
photographed, of the entire cave.
When the original private operator discovered it, he felt like he had found a gold mine.
It’s called Frozen Niagara, because the large walls of flowstone reminded people of a waterfall.
The area surrounds a large deep pit.
A long staircase leads down into the pit, entirely surrounded by formations.
Given all the rain recently, an actual waterfall fell from a crack in the ceiling to the pit’s edge.
After the pit, the wonders kept on coming.
There was a tight passage where one entire wall was covered in stalactites and stalagmites.
Most of these are now protected by a fence.
More decorated rooms came after this.
The urge to stop every yard and take photos is almost irresistible, especially after all the plain rooms before.
This impulse ultimately led to the only bad part of the tour.
Tours of this section of the cave are popular, and the guides keep people to a strict schedule.
That schedule meant that we were hustled out to the exit long before we wanted to leave.
Styx Spring Trail
Styx Spring, where the Styx River surfaces. The water level is high and brown from recent rain.
One of the truisms of Mammoth Cave is that most visitors only get half the experience, the part underground.
Several trails start at the visitor’s center, so I took a quick hike
The trail initially went down a ravine.
The sides of the ravine reveal the different layers in the rock, and signs point them out.
The natural entrance to the cave appeared about halfway down the ravine.
Behind a rope, a set of steps led down, and then the trail disappeared in the darkness.
Continuing down the ravine, the trail eventually reached the Green River.
It ended at an important historic site.
In the early days before the roads were improved, people came to visit Mammoth Cave by steamboat.
The ravine is where they disembarked.
For families who farmed in the area, these visitors were about their only contact with the outside world.
Near the old landing is one of the area’s natural features, Styx Spring.
It was probably inevitable that any underground river would be named after the most famous river of the underworld
from Greek mythology.
Sure enough, one of
Cedar trees on limestone
Dark green trees on white rocks above the Green River, a typical sight hiking around here.
the rivers still carving Mammoth Cave got the name.
Remember that all of them drain to the Green eventually.
Styx Spring is where the Styx River finally surfaces.
The river was high from all the recent rain, so all I got to see was a large brown pool.
Apparently when the water level is lower, the actual cave passage appears.
Leaving the spring, the trail followed the Green River for a while, and then started to climb the hillside.
The rock in this area is all limestone, so both the hill and trail were white instead of the usual black and grey.
In a few spots, it crossed ravines on beautiful old bridges built by the Civilian Conservation Corps.
The trail then entered a grove of red cedar trees.
The trees formed a beautiful contrast with the white rocks all around as the trail passed through them.
Eventually, it reached the top of Green River gorge, overlooking the initial ravine.
From here, a quick walk brought me back to the starting point.
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