Beautiful Rushmore Cave
Beautiful Rushmore Cave in South Dakota is the cave situated closest to Mt. Rushmore, hence the name. It is the area's largest stalactite cave, and home of the "Big Room," a jaw dropping room within the cave that contains a large number of stalactites hanging from the ceiling and protruding from the walls.
Beautiful Rushmore Cave is famous for the "Big Room," which contains fabulous displays of stalactites, large columns, stalagmites, and huge flowstones, as well as amazing examples of ribbons, draperies, and helicites.
The cave is five miles east of Keystone on Hwy 40 and is open from May until October.
The caves of the Black Hills are also an interesting sight to see. They have similar origins as Rushmore Cave. You'll find these caves in a band of limestone rock called the pahasapa limestone. The caves encircle the Black Hills' central granite core. The limestone you find here was formed during the Mississippian Period on the bottom of an ancient sea - 360 to 330 million years ago. The caves you see today were created by five events that occurred in the region's geologic past.
During the first event the limestone rock was modified through several chemical processes. Second, an early cave and karst system formed out of the young limestone rock.
The third step involved the limestone and early caves being buried by more layers of sedimentary rock. Fourth, the central granite of the Black Hills slowly moved upward about 60 to 40 million years ago. The limestone that had sat dormant for so long then underwent lifting, cracking, and was exposed to circulating acidic groundwater. At this time cave building occurred again. The caves we see today were developed during this era.
The final stage involved ongoing episodes of flooding and draining, which modified the caves even more until the water table lowered enough for them to drain. Before and after the draining, decorative cave formations called speleothems were deposited above and below the water table. Visiting these caves is definitely a worthwhile excursion, especially if you enjoy taking in the natural beauty of cave formations crafted in the ancient past.
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