Surveyor, U.S. Forest Service (1968 - 1971) Field Geologist, Denver, U.S. Geological Survey (1972 - 1972) Postdoctoral Research Fellow, Department of Geosciences, University of Arizona (1978 - 1980) Lecturer, Department of Geosciences, University of Arizona (1980 - 1981) Research Associate, Department of Geosciences, University of Arizona (1981 - 1982) Assistant Professor of Geology, Stanford University (1982 - 1989) Associate Professor of Geology, Stanford University (1989 - 1993) Associate Professor of Geological & Environmental Sciences, Stanford University (1993 - 1998) Professor of Geological & Environmental Sciences, Stanford University (1998 - Present)