 He retired in 2004, but has continued to be active professionally.Ernst's research interests have included the petrology, geochemistry, and plate tectonics of Circumpacific and Alpine mobile belts; ultrahigh-pressure metamorphism in Eurasia; geology of the California Coast Ranges, the central Klamath Mountains, and White-Inyo Range; geobotany and remote sensing of the southwestern United States; and mineralogy and human health.Ernst has been a member of the National Academy of Sciences since 1975.