Fossil Butte National Monument

Fossil Butte National Monument, fossil-rich area of buttes and ridges in southwestern Wyoming, U.S. It is located just west of Kemmerer, about 100 miles (160 km) west-northwest of Rock Springs. The 13-square-mile (34-square-km) monument was established in 1972. The monument preserves Fossil Butte, a flat-topped sedimentary rock formation. The butte comprises a small portion of what was once Fossil Lake, which existed some 50 million years ago during the early Eocene Epoch. The Green River...