Wind Cave National Park

Wind Cave National Park was the seventh national park to be established and was the first cave to be so designated.  Located in fringe of the Badlands area of  South Dakota it is noted for two specific geological cave formations, boxwork and frostwork.both shown below.

This cave is recognized as  a three dimensional maze cave with a high density of passages. it is now the 6th longest cave in the world with over 105 miles of explored cave and 4 miles of new cave being discovered and explored each year.

This small opening is where the cave was discovered from the wind "blowing" out of the underground area. As barometric pressures differ inside and outside the variation will cause the air to flow in or out of the cave area. Because the cave has a large area but only small openings the velocity of the air will be higher than in similar sized ones with larger openings.

Inside the cave this is where the opening from above terminates

These calcite deposits in rectangular and triangular patterns are examples of boxwork.  95% of the known boxwork deposits in the world are in this cave.

Another photo of the boxwork deposits also showing the needle like deposits called frostwork

Frostwork is the deposit of calcite like these small needles shown here on top of a deposit labeled as popcorn.

Our guide was showing us the structure of the cave pointing out the thick layers of rock that formed the walls and ceiling of the cave....

Then he pointed out how the separation of layers and their own weight can sometimes cause them to collapse.....NOT reassuring when you are 600' below the surface.