Stanley Williams, a professor of volcanology at Arizona State University, received his Ph.D. in geology from Dartmouth in 1983. In more than two decades of research, he has worked on dozens of volcanoes on five continents. In 1993, during a conference in Pasto, Colombia, on the threat posed by nearby Galeras, he led fifteen scientists into the dormant volcano's crater to check its vital signs - gas emissions, minute gravity changes, and the like. Galeras's sudden eruption killed several of his colleagues and nearly cost Williams his life. In the wake of the eruption, Williams has requently appeared in national media to discuss his own harrowing experiences and volcanoes in general.