Wind Cave National Park: South Dakota


Wind Cave National Park is located in the southern area of the Black Hills.  The cave is thought to be about 300 million years old.  This means that Wind Cave is one of the worlds oldest caves in existence.  The geology of this cave is very interesting and complex.  You would never think that a sea would have once existed in southwestern South Dakota.  Whats interesting is that there actually was at one time a warm shallow sea which existed in the exact region of southwestern South Dakota.  The sea is estimated to be about 350 Million years old.


The cave began to form off a huge bedrock which was comprised of madison limestone.  There were organisms living in the sea which once existed in South Dakota, the shells of the living organisms in the sea formed into what is not the madison limestone.  After the madison limestone was formed and the foundation for the cave was set there was then a chemical change in the groundwater which is the reason for the caves formation.  As the ocean started to dry up sulfer was released into the water which formed sulfuric acid.  The sulfuric acid is the reason for eating away at the rock and forming the cave.  The first passage ways of the cave are about 320 million years old.  Over the next 200 million years the ocean continued to come back and dry up again until the water began draining for the cave about 45 million years ago.


The slow moving water that sat in the cave for millions of years was the reason for these intricate opening to be formed within the limestone.  Today water still continues to sit 500 feet below the surface.  This water still continues to make changes to the cave today.  The slow seepage of water continues to produce ‘frostwork’ and ‘cave popcorn’ on the walls and ceilings of Wind Cave.  Frostwork is the growth of calcite or other minerals that grow out of cave popcorn.  Cave popcorn is knobby growths of calcite found of cave walls which is formed by slow seeping water.


This is a photo of cave popcorn with frostwork growing out of it.  The cave popcorn is the small knobby white bumps and the frostwork is the crystal like formation growing out of it.


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