Has worked for the U.S. Geological Survey for 40 years. His research interests and primary expertise are stratigraphy, mineral chemistry, geochemistry, and petrology of arc volcanic rocks and the origin and evolution of magmatic systems. The majority of his geologic experience is in the study of young volcanic rocks, primarily in the Cascade Range, at the Lassen Volcanic Center, and Mount St. Helens. In 2010 he completed a geologic map of Lassen Volcanic National Park and vicinity. His map, published at 1:50,000 scale includes 2000 km squared of young volcanic terrane. He served as an associate editor for Bulletin of Volcanology, performed outreach and consultation on geologic matters for the National Park Service, and continues to collaborate with university colleagues on Lassen and Mount St. Helens research topics. He holds degrees in Earth Science: BS from the University of California at Santa Cruz (1976), MA from California State University-San Jose (1983), and a PhD from University of California at Santa Cruz (1993).