Today we explore Wind Cave.
The Lakota Indians told ancient stories about a sacred hole in the ground that blew air in an out, like the lungs of some living creature. But the first recorded discovery of Wind Cave wasn't until 1881 by Tom and Jesse Bingham. The story goes that one of the brothers stuck his head in the hole, and it blew his hat off. When he came back later to show his friends, the wind had reversed direction and sucked his hat in.
There's a simple meteorological explanation for the "breath" of Wind Cave. If the barometric pressure outside the cave is high, air gets sucked in. If it is lower, air is blown out. The velocity of the wind gives testament to the enormous volume of empty cave space that lies beneath the surface. By one estimate, the surveyed portion of the cave accounts for just 2% of the airflow. That means 98% of the cave is yet to be discovered.
Right now, it ranks as the fifth largest cave system in the world. I presume it will move up in the standings as more surveying trips are made.
If Wind Cave contained only the typical cave formations, it would be interesting but probably not worthy of becoming our nation's seventh National Park. Fortunately, Wind Cave has one key variable that makes it unique. It's dry. There's not a lot of seepage. The air is not very humid. There are no bats. There are no insects or worms either. With the exception of extremophiles (microbial organisms which live in extreme conditions), its ecosystem is barren.
Wind Cave is distinctive because it contains formations called "boxwork".
Boxwork is hard for me to describe. It looks a little like burnt potato chips hanging in complex interwoven sheets from the ceiling and walls. It's as delicate as it looks. Wind Cave is one of the few places on earth where boxwork exists. Some estimates say that 95 percent of the world's boxwork is contained inside Wind Cave.
How was boxwork formed? One theory says that millions of years ago, Wind Cave was a solid mass of bedrock. The bedrock fractured for some reason, and the cracks got filled in with calcite (probably by a water-deposit process). Then a layer of limestone formed on the surface above. Limestone and water produce a weak acid: calcium carbonate. So, as water leeched down through this new layer, it became slightly acidic. Over a long, long time, the water inundated the area, stagnated, and slowly ate away the bedrock. The calcite remained intact. Thus boxwork is what was left behind after the water drained away.
Ma and I took the "Garden of Eden" tour. The "Garden of Eden" is a large room with excellent acoustics deep inside the cave. The tour starts in an elevator. At the bottom, you exit a pressure-sealed lobby. You emerge into a strange world that is perpetually 53 degrees and pitch black. Thankfully, they've installed lights to lead the way for tourists.
Part of the Garden of Eden tour includes a segment where the ranger turns off the lights, and everyone gets to experience the cave in its natural state. On our tour, the ranger was unable to get the lights to turn off. So, we moved on. Moments later, as we were ascending a staircase, the lights decided to heed her earlier attempt. The whole place went utterly dark. Ma and I were prepared. We happened to be carrying our head lamps with us. Between the ranger's flashlight, our head lamps, and several cell phone screens, we made it safely back to the elevator. What an interesting experience!
Fun fact: even in the depths of the cave, you're still at quite a high elevation. The Garden of Eden is 3,940 feet above sea level.
The Lakota Indians told ancient stories about a sacred hole in the ground that blew air in an out, like the lungs of some living creature. But the first recorded discovery of Wind Cave wasn't until 1881 by Tom and Jesse Bingham. The story goes that one of the brothers stuck his head in the hole, and it blew his hat off. When he came back later to show his friends, the wind had reversed direction and sucked his hat in.
There's a simple meteorological explanation for the "breath" of Wind Cave. If the barometric pressure outside the cave is high, air gets sucked in. If it is lower, air is blown out. The velocity of the wind gives testament to the enormous volume of empty cave space that lies beneath the surface. By one estimate, the surveyed portion of the cave accounts for just 2% of the airflow. That means 98% of the cave is yet to be discovered.
Right now, it ranks as the fifth largest cave system in the world. I presume it will move up in the standings as more surveying trips are made.
If Wind Cave contained only the typical cave formations, it would be interesting but probably not worthy of becoming our nation's seventh National Park. Fortunately, Wind Cave has one key variable that makes it unique. It's dry. There's not a lot of seepage. The air is not very humid. There are no bats. There are no insects or worms either. With the exception of extremophiles (microbial organisms which live in extreme conditions), its ecosystem is barren.
Wind Cave is distinctive because it contains formations called "boxwork".
Boxwork is hard for me to describe. It looks a little like burnt potato chips hanging in complex interwoven sheets from the ceiling and walls. It's as delicate as it looks. Wind Cave is one of the few places on earth where boxwork exists. Some estimates say that 95 percent of the world's boxwork is contained inside Wind Cave.
How was boxwork formed? One theory says that millions of years ago, Wind Cave was a solid mass of bedrock. The bedrock fractured for some reason, and the cracks got filled in with calcite (probably by a water-deposit process). Then a layer of limestone formed on the surface above. Limestone and water produce a weak acid: calcium carbonate. So, as water leeched down through this new layer, it became slightly acidic. Over a long, long time, the water inundated the area, stagnated, and slowly ate away the bedrock. The calcite remained intact. Thus boxwork is what was left behind after the water drained away.
Ma and I took the "Garden of Eden" tour. The "Garden of Eden" is a large room with excellent acoustics deep inside the cave. The tour starts in an elevator. At the bottom, you exit a pressure-sealed lobby. You emerge into a strange world that is perpetually 53 degrees and pitch black. Thankfully, they've installed lights to lead the way for tourists.
Part of the Garden of Eden tour includes a segment where the ranger turns off the lights, and everyone gets to experience the cave in its natural state. On our tour, the ranger was unable to get the lights to turn off. So, we moved on. Moments later, as we were ascending a staircase, the lights decided to heed her earlier attempt. The whole place went utterly dark. Ma and I were prepared. We happened to be carrying our head lamps with us. Between the ranger's flashlight, our head lamps, and several cell phone screens, we made it safely back to the elevator. What an interesting experience!
Fun fact: even in the depths of the cave, you're still at quite a high elevation. The Garden of Eden is 3,940 feet above sea level.
Here's another example of boxwork. This "pod" was corrugated like cardboard.
The calcite deposits shown above are known as "frostwork". The moist air of a cave contains tiny particles of calcium carbonate. As the moist air hits a cool surface, the calcium carbonate coagulates and forms a crystal. If you shine a light on frostwork just right, it sparkles like diamonds. Wind Cave has a few moist areas where frostwork has formed.
Speaking of moisture, this formation is called "flowstone". (I would have named it "gravy-stone".) Flowstone forms when seepage creeps down a slightly inclined shelf like this one. The seepage contains dissolved minerals. The water is only capable of holding those minerals whilst it contains carbon dioxide. When the water hits the open air, it loses its carbon dioxide, and the minerals slowly get deposited. Layer upon layer builds up and causes the shelf to get coated with calcium, gypsum, and other minerals.
Don't touch! Oils from our skin would cause the water to avoid the areas where we made contact. The flowstone would cease to form.
Flowstone and frostwork are common in other caves. But Wind Cave exhibits very few other typical cave formations. For example, there's a noticeable dearth of stalactites and stalagmites. (These are the fang-like spikes that riddle most caves.)
Fun tip: There's an easy way to remember the difference between stalactites and stalagmites. Stalactites come from the ceiling. Stalagmites come from the ground.
The Bingham brothers may have been the ones to discover the cave, but they didn't do much exploring. Sixteen-year-old Alvin McDonald gets the credit for mapping out the majority of the early cave. From 1889 to 1893 he spent almost every day here. With just a candle lantern and a ball of string he explored hundreds of passages, recording everything he found. Alvin was the son of a miner who was hired to extract riches from the cave. Alas, mining proved futile. There's no gold or gems down there. So, they switched enterprises and turned it into a tourist attraction. Alvin served as a guide. Since conservation was unheard of in those days, visitors were encouraged to leave their mark on the cave. The message shown above was left on August 17, 1892.