Natural Bridge Caverns

The Natural Bridge

On Friday we had one of our first "fun" days - up until this point it'd just been driving and driving and sleeping and resting and more driving.  (It's really depressing to cross into Texas on I-10 and see the mile markers start at 800+)  Our activity for the day was a visit to Natural Bridge Caverns.  I was excited about this because as a kid growing up in Indiana, I took tours at Wyandotte Caves (now closed) and Bluespring Caverns.  The tour at Florida's Caverns was disappointing - the cave was really beat up.  I had high hopes for this trip, and I was not disappointed.

Entrance tunnel into the cave

As we drove up, the geology started changing.  It wasn't the typical Karst terrain I'm used to in Northern Florida cave country - mostly flat with some surprise rolling hills.  It was basically large hills entirely - not a flat spot to be found.  There were some large road cuts along the way, and I wish I'd gotten a picture of them.   The road cuts showed some amazing distinct layers of limestone, with different colored layers. (interesting - what caused this?  most likely climate changes or receding of an inland sea for a period of time?)  Also, some of the cuts showed "tortured" limestone - not flat layers.  Some places were really bent and in places directed up at nearly 45 degrees.  I told Sarah that I thought this area was geologically active at some point in time.  As it turns out, an earthquake a long time ago fractured the limestone which caused cracks and allowed water to intrude and dissolve the limestone to form the caverns.

The cave was simply amazing.  I was really happy that despite being a heavily traveled privately owned show cave open since the 60s, it was clean and well taken care of.  Not a lot of black on formations from people touching the cave, no garbage, very little algae on the walls.

We had an amazing tour guide, and we were the only ones on the tour, so it was a great experience.  We got to move at our own pace and ask a ton of questions.

The explorer's entrance.

Picture taking was difficult - lighting was low and I basically refuse to use either a flash or a tripod - this simply takes too long and seems to create "posed" pictures which I'm not a fan of.  I'll hand-hold the camera or prop it up on something to get a picture, take 5-10 shots, and one will typically turn out.  I find that I get more pictures I like this way.  I'll try to use a nearby guide rail if possible.  All of the cave shots are between 1/3 and 2 second exposure times, none with fill-in flash.

Broomsticks

This cave had some really amazing formations I hadn't seen before - broomsticks.  These are stalagmites (growing from the floor) which are long and thin.  The typical formations I've seen have been more cone shaped - larger at the bottom than at the top.

More broomstick formations

Halfway through the cave a man-made bridge crossed a crevasse nearly 40 feet below.

The bridge at the lower section of the cave

 This led to what I would call a "sump" which we could bypass with a new walkway.  Apparently before the walkway, the passageway would fill completely with water, making the back half of the cave inaccessible.

The tour was punctuated by a large room - the length of a football field, sloping upward to end at a large dome.

View of the dome at the back end of the cave

View from the dome, looking down into the cave

Here's the most amazing thing I learned while on the tour...



About a year after the cave was opened in the 60's to tours, the operators discovered that they had a hard time getting tour groups through if they had to walk all the way in and then all the way back out - a 1 hour tour turned into a two and a half hour tour.  It took longer to get people to walk back up the stairs on the way out apparently, and groups would be climbing over each other in the small passages.  So, they blasted a tunnel from the back of the cave (near the dome shown in the picture above) up to the surface. 

Here's the kicker - on the way up to the surface, they discovered several smaller caves and pockets of formations.  One of the pockets was big enough to fit several small cars in, and had passageways going off in various different directions. 

One of the pockets of formations in the tunnel to the surface

One can conclude from this that in a region with active karst topology and some geologic activity causing cracks in the limestone, the rock is probably littered with small caves and caverns.  It just doesn't seem like it could be any other way based on the size of the tunnel they blasted and the number of "cave pockets" they ran into.  It really makes you wonder how many caves and caverns exist out there that don't hit the surface, and are just waiting to be discovered by some technology that can find pockets in the earth.