Member of AGU since 1973. Professor of Geology at the Massachusetts Institute of Technology. Major interest is understanding the chemical differentiation processes that have led to the formation of the crust and mantle of the Earth and similar processes in other planets, including the Moon, Mars, and meteorite parent bodies. B.A. (Phi Betta Kappa), 1971, University of Colorado, Boulder; A.M., 1975, and Ph.D., 1976, Harvard University. Research Associate, State University of New York at Stony Brook, 1975-1979; Visiting Assistant Professor, California Institute of Technology, 1979; Faculty member at MIT since 1979; Visiting Scientist at University of Cape Town, 1993-1994; Research Scientist, Physics Department, University of Zimbabwe, Harare, 1997-2001; Visiting Professor, ETH, Zürich, 2002. Member of the Geological Society of America, the Geochemical Society, National Speleological Society, Sigma Xi, Fellow of the Mineralogical Society of America and MSA Councilor from 1994 to 1997. Author of 135 publications, 19 in AGU journals. Most important publications include open system behavior in crustal magma reservoirs (1982), mantle melting processes that generate mid-ocean ridge basalts (1992), the role of H2O in subduction zone magmatism (1993), thermal evolution of the Earth's mantle during the Archean (1997). Received the 1993 N. L. Bowen Award of the VGP section, AGU Fellow in 2001, Highly Cited Researcher, ISI, Thomson Scientific, 2002. AGU service as Associate Editor of Geophysical Research Letters (1979-1982); Secretary of VGP section (1988-1990), member of Harry H. Hess Medal committee, President-elect and President of the VGP section (1996-2000), and chair of the Meetings Committee (2000-2004).