Gary L. Prost has been working as a geologist for more than fifty years, specializing in mineral and oil exploration. He studied geology at the Colorado School of Mines, obtaining his PhD there in 1986. His employers have included the United States Geological Survey and several oil companies, and his work has taken him to more than thirty countries. Now retired, he leads field trips and does public outreach on topics of geological interest. His books include The Geology Companion, The United Kingdom’s Natural Wonders, South America’s Natural Wonders, and the two-volume North America’s Natural Wonders. He lives in El Cerrito, California.