Wind Cave National Park, the eighth National Park established in 1903 and located in the Black Hills of southwest South Dakota, is the subject this edition of Radio Curious. Our guest is Tom Farrell, Chief of Interpretation at Wind Cave National Park.
Lakota stories speak of a hole in the Black Hills that blows air which is a sacred place for their people. The tipi rings, near the present day elevator building at Wind Cave National Park, indicate that Indians camped in the area and knew about the cave’s small natural entrance. Sitting Bull’s nephew is quoted as saying that “Wind Cave in the Black Hills was the cave from which Wakan Tanka, the Great Mystery, sent the buffalo out into the Sioux hunting grounds.”
One of the stories tell of a beautiful woman, known as the buffalo woman, who came out of the cave and gave the bison to the Lakota people.
In 1881 a couple of non Lakota deer hunters happened on to the cave when one of them was following a wounded deer up a ravine and heard a loud whistling sound. The hunter noticed grass caught in a strong breeze on what otherwise was a calm day. Investigating, he found a small hole blowing with such force that it blew his hat off. Returning to show what he thought was a phenomenon to some friends, one of them put a hat in front of the hole which was sucked into the cave because the wind had switched directions.
The direction of the wind is in fact related to the difference in atmospheric pressure between the cave and the surface. To understand this phenomenon it’s important to understand barometric or atmospheric pressure.
At sea level gravity is strongest and air pressure is greatest. And because gravity weakens as you go up, air pressure is lower at higher altitudes. However, the barometric pressure at any given location on the earth is constantly changing. On the surface, weather is driven by the sun, which heats some areas of the earth more than others. Temperature differences lead to pressure differences which produce winds, bring in clouds, or clear skies. Understanding barometric pressure readings help forecast the weather. A rising barometric pressure often suggests clearing skies and fair weather where falling pressure indicates that wet or stormy weather may be on the way. Areas of very low pressure are associated with severe storms, such as tornadoes or hurricanes.
Because Wind Cave is so large and has a lot of space, it also has an air pressure system. That air pressure system is always working to be equal to the air pressure system on the surface. So if a high pressure system is on the surface, air will be forced into the cave to create a high pressure system in the cave. When there is a low pressure system on the surface, the high pressure in the cave forces air out so the cave will have a low pressure system also. This is referred to as cave breathing.
Barometric airflow through the natural entrance of Wind Cave not only gave the cave its name, but also provides an opportunity for determining the approximate volume or size of the cave passages. Monitoring and recording the barometric airflow through the cave’s natural entrances help us understand the volume of air in the cave and that can be used to calculate the total volume of cave passage. By using the amount of air that comes from the cave we can determine the volume of space in the cave. At this time it has been estimated that than 10% of the caves volume has been found. That does not mean however that the mileage of the cave is identifiably known. There could be many, very small passages or one great huge one. But it does give us an idea of how big the cave could be.
Many caves are big enough to have barometric winds. However, the wind at Wind Cave is noticeable because of its very small, natural entrance. Wind Cave, one of the longest caves in the world, is also one of the most complex caves known. Currently most all of the cave lies beneath about a 1 mile square area of land.
Wind Cave became the eighth National Park in 1903.
When Radio Curious visited Wind Cave National Park on September 23, 2014, we met with Tom Farrell, the Chief of Interpretation, and began our conversation when I asked him to describe the discovery of the Wind Cave.
The book Tom Farrell recommends is “Wind Cave: An Ancient World Beneath the Hills,” by Art Palmer.
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