The Black Hills region of South Dakota includes high ridges and deep caverns, the remains of a several-hundred-million-year period of intense pressure from the earth's molten crust. Over time, wind and water have eroded the landscape, a process still under way.
(Photograph shot on assignment for, but not published in, "Scenic Drive: South Dakota Badlands and Black Hills," May/June 1996, National Geographic Traveler magazine)
