Geology
The Black Hills are a small range of mountains by most standards, but they do extend from the Great Plains of North American in western South Dakota down into Wyoming. Because they seem to be set off from the main body of the Rocky Mountains, the region is somewhat of a geological anomaly. This area is home to some of the most fascinating and unusual geology in the world. In addition, the Black Hills region is home to some of the most unique caves to be found anywhere. They are most interesting due to their age, evoluntionary history, the rare formations that they contain and their complexity.
The rock formations in the Black Hills began as various layers of limestone deep within the earth. Approximately 40 to 60 million years ago, this quiet layer of limestone was subjected to lifting, cracking and circulating acidic groundwater, as the layer of granite below it rose to the surface. As the years progressed the area was also affected by peirodic episodes of heavy flooding, wind, and winter storms – all of which played a part in the structures that you see today.
A well known geological structure is the Rushmore Cave, located due east of Harney Peak which is the approximate center of the Black Hills. Most of the caves in the area were formed like spokes of a wheel, with the passages running out in a circular pattern. Some of the caves in this area are felt to link to portions of the 320+ million year old Mississippian cave systems.
Local geological conditions have created many unique and fantastic rock formations as well as the extensive cave system. Ongoing exploration and research will expand the current knowledge and understanding of the geological area. Despite its formitable appearrance this area is a very fragile environment which can never be replaced. Come and enjoy, but remember to treat the area with the respect that it deserves.
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South Dakota School of Mines
South Dakota School of Mines and Technology offers undergraduate and graduate programs in Rapid City.
