Another side trip that we took this summer on our way to Montana, was a visit to the Mammoth Caves in Kentucky. First of all, the drive across the southern region of Kentucky is picture book perfect. The red barns, grassy hills, and livestock is surrounded by mountains. Then as you approach the Mammoth Cave National Park the place starts to look more like the Piedmont and less like a place that would have one of the largest caves in the world. As we drove down the long driveway towards the park’s campground, we couldn’t help but wonder if the ground below us had tourists walking in the cave system. Of course my wife wondered if there was a chance that we may fall into a sink hole. We checked into the campground and once again I noticed that the place looked nothing like a cave place should look like. But at the entrance everything began to change. We walked down a steep hill along side a creek that led to a hard right hand turn into a giant hole in the ground that was lined with stairs. I would say the entrance is probably 30-40 feet high and 70 feet wide. A guide awaited our group at the entrance. Many people have gotten lost and died in these caves. The guide took us through a corridor that led to an enormous open room that resembled a coliseum. From there we walked down many other caves that led to some tight areas like “Fat Man’s Misery” and “Tall Man’s Agony”. The kids imaginations got ahold of them and the oldest actually got a little scared. A tall staircase led up an inverted cave or dome that led back to the beginning. We hiked about 3 miles total during our “taste” of the caves.
The formation of the caves started 30 million years ago when the Green River started carving a valley through the Mammoth Cave plateau. The sandstone rock layer that covered the top of the plateau was eventually eroded away in some areas, and the water found it’s way down into the limestone layer underneath. The water dissolved the limestone rock away at a much higher rate than the sandstone. Due to glacial action on other parts of North America, the Green River cut an even deeper valley that also helped speed up the cave process. As the river eroded a deeper valley, the cave’s water table would drop which opened up another limestone layer to a higher rate of erosion. Basically in a nut shell, the water seeped through the tougher top sandstone layer and made it’s way to the softer limestone layer. The limestone layer eroded away in an underground river formation which formed dry caves when the water table dropped. Inside the caves there are waterfalls, lakes, and streams just as there would be above the surface. The limestone was laid down millions of years ago by a large sea, and a river delta probably laid down the sandstone cap layer. There are also stalagmites and stalagmites in some sections, but we did not get a chance to see these. In all there are a confirmed 360 miles of navigable caves.