Inside Yellowstone - Sheepeater Cliff
Sheepeater Cliff Photos - Earths Extremophiles Website
Basalt - Wikipedia
Basalt - About.com
Columnar Basalt Photos - Centripetal Notion
Did You Know?
Prior to the establishment of the National Park Service, the U.S. Army protected Yellowstone between 1886 and 1918. Fort Yellowstone was established at Mammoth Hot Springs for that purpose.