John Valley is a geochemist recognized for his work on evolution of the Earth’s crust. He is particularly known for stable isotope studies of igneous, metamorphic, and sedimentary rocks with applications to the formation of mountain belts and to changes in Earth’s climate from 4.4 billion years ago until today. Valley was born in Winchester, Massachusetts and grew up in Lexington, Massachusetts. He graduated from Dartmouth College in geology and from The University of Michigan with a Ph.D. in geochemistry in 1980. He taught at Rice University before joining the faculty at the University of Wisconsin, Madison in 1983. He has been president of the Mineralogical Society of America, is a Fellow of seven professional societies and is a member of the National Academy of Sciences. The mineral, valleyite (Ca4Fe6O13), is named in his honor.

Research Interests

John Valley's earliest research concerned high-grade metamorphism and Precambrian geology with fieldwork in many areas of Asia, Australia, Europe, and N. America. More recently, he has investigated isotope geochemistry of magmas of known age from 4.4 billion years to Recent. His studies of zircons from the Earth's earliest crust have shown that the planet's surface cooled more quickly than previously thought, that hot "Hadean" conditions lasted less than 100 million years after the formation of the Earth and Moon, and that habitable conditions and oceans existed on Earth over 800 million years before the earliest known microfossils. He has also shown that these ancient fossils lived in complex communities of microbial life 3,465 million years ago, indicating that the first life came earlier. His other interests include mineralogy, paleoclimatology, and astrobiology. In 2005, he established the WiscSIMS Laboratory at The University of Wisconsin, which is dedicated to developing procedures for measurement of isotope ratios at nm- to mm-scale in minerals and novel applications of stable isotope geochemistry.

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Primary Section

Section 15: Geology

Secondary Section

Section 16: Geophysics