2019 Arthur L. Day Medal

Presented to John W. Valley

John W. Valley

John W. Valley
University of Wisconsin-Madison


Citation by Brad Singer, University of Wisconsin-Madison

John W. Valley is not only among the most distinguished geochemists of his generation, he is actively developing new methods using the chemistry and physics of isotopes to explore earth history. He pioneered research in three principal directions: (1) the origin of lower crustal granulites, (2) development of novel techniques for microanalysis of stable isotopes in minerals, and (3) using isotopes in zircon to explore earth's earliest surface conditions.  John’s findings are prolific, wide-reaching, and of exceptional impact, thus he is most deserving to receive the Day Medal. The discovery of heavy isotopes of oxygen in a 4.4 Ga zircon from western Australia comprises evidence that Earth's early crust formed in the presence of liquid water. John’s hypothesis of a "cool early Earth"—suggesting that life may have existed 800 million years earlier than the oldest microfossils—was at odds with the long-held view of Earth covered by an incandescent magma ocean.  It has been poked at and refined by other groups and now features in many introductory geology textbooks. It is a wonderful example of how technological advances in chemistry and physics, harnessed by an imaginative and unconventional thinker like John, propel revolutions in our science.  Subsequently, John established the WiscSIMS laboratory that has been used by hundreds of researchers and students worldwide. John continues to pursue technological advances, for example his 2014 Nature Geoscience paper is the first geological application of Atom Probe Tomography (APT) and shows that the spatial distribution of lead atoms in the zircon which gave rise to the cool early earth hypothesis indeed reflect the formation of this crystal 4.4 Ga.  The APT methods emerging from John’s current students are opening new avenues of discovery at the sub-nanometer scale. Moreover, John's rigorous approach to mentoring dozens of graduate students and post-docs has created a generation of highly capable, broadly-trained, earth scientists who themselves are now leading our society and nation forward.


Response by John W. Valley

I am honored to receive the Arthur L. Day Medal and grateful to GSA and many people who have helped me. Indeed, an award like this reflects a community effort. I have been fortunate in my mentors, my colleagues and my students.

Joining the pantheon of Day medalists is a daunting prospect and causes me to reflect how lucky I have been. My parents instilled an early sense of wonder for the natural world and encouraged me to find my passion. It could have been any passion, but I started collecting rocks when I was 4 and haven’t stopped. Dick Stoiber introduced me to volcanoes as an undergraduate at Dartmouth. Eric Essene introduced me to metamorphic rocks and the rigor of research at Michigan. I still hear Eric’s voice today when I try to write something. Nobody I have ever known could make critical thought so much fun. This is where I learned that if something doesn’t make sense, you just need to look more closely, often at higher magnification. Eric and John Bowman, encouraged me to write Jim O’Neil who agreed to let me work with him at the USGS as part of my PhD. Jim introduced me to isotopes, the third dimension of the periodic table. He taught me the value of selecting an important subject and making really good measurements. This combination, better measurements and higher magnification, has been important in my career.

I would love to tell you tales about former graduate students, post-docs and colleagues, but they are too numerous and you know many of them already.  I’ll end by thanking my wife, Andrée. She is a professional sculpture and fills my life with color. I would not be standing before you today without her assistance in so many different ways.