Peter Kelemen has integrated geologicobservations with geochemistry, geophysics, thermodynamics and continuum mechanics to reveal unexpected links between the dynamics and evolution of Earth’s crust and upper mantle and unveil a geological solution to carbon sequestration. 

Kelemen’s discoveries are sparked by geologic observations. Early on, dunites caught his eye. He saw them as channels through which large volumes of melt had flowed — and reacted. With a quantitative understanding of how they form, he and his colleagues discovered that the formation of melt channels could explain the composition of mid-ocean ridge basalts, the interpretation of U-series disequilibria and strain localization in the mantle. Kelemen’s ideas regarding melt-rock reaction also provided a possible explanation for why the continental crust is andesitic while most primitive melts are basaltic. While melt-rock reaction is a viable hypothesis for the genesis of some continental rock formed at arcs, he realized that the spectrum of crustal formation mechanisms must include those involving primitive basalts. This led him and his colleagues to explore the role of convective instability of lower crust and diapiric upwelling from slabs. His calculations inspired the community to pursue new field work, geochemical analyses and thermodynamic calculations. He took a similar path to invoke a novel model for the formation of oceanic crust at fast spreading centers, inspired by observations of “sill-like” gabbro layers in the Oman ophiolite. He demonstrated that these sills are geochemically isolated, which led to the bold hypothesis that the entire lower crust formed by the injection of sills. Crustal genesis by sill formation remains a leading hypothesis, largely as a result of Kelemen’s innovative work integrating geophysics, thermomechanical models, fabric analyses and cooling rates. 

While in Oman, Kelemen became fascinated by remarkable structures in sets of carbonate veins. These observations motivated a multidisciplinary analysis of the carbonation process and an assessment of how much carbon dioxide (CO2) the ophiolite sucks out of the atmosphere today; he realized that with a bit of geoengineering, ophiolite bodies around the world could provide a meaningful CO2 sink. 

A hallmark of Kelemen’s work is how he integrates ideas from a broad range of fields, guided by his keen geologic intuition, to relentlessly investigate problems in Earth science. A second hallmark, a willingness to take scientific risks, shows how science can progress in more than incremental steps; as an exemplary recipient of the 2021 Hess Medal, he would make Hess proud.

— Greg Hirth 

Brown University 

Providence, Rhode Island 

— Peter Molnar 

University of Colorado Boulder 

Boulder, Colorado

I thank Greg Hirth and Peter Molnar for their generous words. Honorees always say they couldn’t have succeeded without help. I don’t like predictable phrases, but this is particularly true in my case. I never had the training to address many problems we investigated, I forgot most of the training I had, and I only arrived here because friends were willing to indulge my naive insistence that “there must be a way to make this work” and then help me find it.  Driven by vague ideas about the origin of continental crust, I stumbled into fantastic training in petrology from Bernard Evans and Stu McCallum. I was doubly lucky to find Mark Ghiorso, who had the tools to quantify melt/rock reaction. Jack Whitehead was a role model for understanding feedback in geodynamics and the courage to take simple approaches to complex problems. Greg Hirth was my “second Ph.D. adviser,” teaching me all I know about rock mechanics. We set out to understand melt transport, then viscous earthquakes, shouting back and forth through the ceiling of adjacent offices. My shouts were questions. Greg’s were answers. Marc Spielgelman brought our notions to life in numerical models. Students and postdocs, especially EinatAharonov, Jun Korenaga, Stefan Bernstein, Karen Hanghøj, Matthew Jull, Mark Behn, Lisa Falk, Juan Carlos de Obeso, Noah McQueen, Jill VanTongeren and James Leong, made exceptional, original contributions. Stan Hart and Al Hofmann were generous mentors, Brad Hacker and Craig Manning, supercollaborators. Long ago, freaked out by predicted resource crises, I asked Half Zantop at Dartmouth what to do. He replied, “Focus on geology. Maybe, when you’re 50, you can have a broader impact.” That’s kind of what happened. Years of basic geoscience yielded tools for applied research. The Endless Frontier meets Limits to Growth. As Dihedral Exploration, Geoff Radford and I did “extreme-terrain mineral exploration,” taking big risks for low pay in projects that transcended the notion of a job. I still feel our research is more important than our jobs. Moreover, mineral exploration does not take no for an answer. If you can’t find it here, look over there. . . . There must be a way to make this work.  Stepping back, I thank Rachel Cox. Along the way, there’s been too much deferred gratification, especially for Rachel. It’s been fantastic, and the climate crisis looms, but it’s time for us to slow down and enjoy each day together.  — Peter B. Kelemen  Columbia University New York, New York

Peter B. Kelemen received the Bowen Award, presented by the Volcanology, Geochemistry, and Petrology Section at the 2004 Fall Meeting in San Francisco, California, last December.  

Tonight we are here to honor Peter Kelemen, a leader in our field. Peter has led by the single-minded pursuit of a big idea: Virtually everything in VGP is pertinent to or can be explained by reactions between migrating magma and the rocks through which they pass.

I wondered some time ago from where this passion derived. It seems that as a young man, Peter, like many young searchers, went to India and pondered the meaning of life, in Peter's case while doing geological fieldwork. The vision struck while Peter was sitting on an outcrop of mantle peridotite in the Himalayas. There were all these rocks, tens of kilometers thick, with dikes passing through them. How could the magma possibly traverse such long distances without being fundamentally modified by the materials through which they pass? And how could they then not leave a record of their passage?

Armed with this vision, Peter headed to graduate school. Since that time, Peter has investigated melt-rock interaction with amazing breadth and depth, through a combination of careful fieldwork, quantitative chemical modeling, and investigation of the fluid dynamic instabilities associated with migrating magma. He showed us that the ubiquitous "dunite channels" in exposed peridotites were the remnant tracks of migrating magma. This recognition has led to a wide range of subsequent developments in fields that include ophiolite field studies, the fluid dynamics of melt migration, the chemical consequences of melt migration, and U-series disequilibria.

To investigate these problems, Peter was also walking over the ocean crust, and he decided to turn his attention to the physical aspects of its origin by carefully looking at the structures and chemical compositions of the gabbroic layers. This work led to papers that definitively laid to rest competing models for the physical construction of the ocean crust. Through his highly interactive style, Peter has developed far beyond melt-rock interaction. He has related seismic velocity to chemical compositions and identified the physical aspects of delamination of continental lithosphere. He has emerged as a leader of large field programs on land and at sea.

One of the favorite phrases I remember from graduate school is Gil Hanson's comment that "there are no bad problems, only bad scientists." Peter exemplifies the positive aspects of this perspective. It was not necessarily that his vision of mantle-melt interaction was prescient. But Peter pursued this problem with such vigor that he has in many ways redefined our field. It led him to write papers in geophysics, geochemistry, fluid mechanics, seismology, and tectonics, to lead ambitious field programs, to do experiments, and to direct theses in theoretical geodynamics. Out of all these interactions has come a host of scientific advances, new problems to explore beyond melt/rock interaction, and the need for all of us when interpreting our data to consider the consequences of the inevitable reactions that take place during transport.

Friends and colleagues, please welcome Peter Kelemen, a scientist who has redefined the way we think, and one of the most productive and influential contributors to our field in the past five years.

—Charlie Langmuir, Harvard University, Cambridge, Mass.

As a graduate student, I imagined that I was engaged in a scientific discussion with Norman Bowen, so it feels like the pinnacle of success to be associated with Bowen in this way. I have a habit of seeking out father figures such as Bowen. I have an excellent real father, who is here tonight. A refugee from both Hungarian Nazis and Communists, but a lover of European culture, my father taught me by example never to join any political groups, but to appreciate what the world has to offer. In 1980, mapping in the Himalaya, I saw felsic intrusions cutting peridotite. I was inspired with a vision: Reaction between felsic magmas and the mantle would solve the "andesite problem" posed by Bowen and Fenner! I didn't realize that if there still was an andesite problem in 1980, it was that there were too many solutions. Bernard Evans is The Expert on peridotite metamorphism, so I went to Seattle. There I found many father figures, including Mark Ghiorso and Stu McCallum as well as Bernard. At the University of Washington, I could develop my "andesite inspiration" without confronting other hypotheses directly. When I emerged, I had something of my own. Also in 1980, I joined a company specializing in "extreme terrain mineral exploration." My longstanding business partner, Geoff Radford, lived simply to do every job right. If he said yes to something, he was totally committed. I have tried to emulate this. For brevity, I am now going to thank people in clumps. Including Geoff Radford, the first is the tough clump. Always honest, Peter Molnar and Dan McKenzie were not formal mentors, but have been simultaneously exemplary, terrifying, and encouraging. I once told Dan that I thought most scientists don't live up to their potential. Dan replied, "Not you! You're an overachiever!" Nobu Shimizu belongs here, with Charlie Langmuir. Adolphe Nicolas, who exemplifies the application of field geology to geodynamics, is a fierce but generous critic of my work. Foremost among the supportive clump are Stan Hart and Mike Purdy. Steve Holbrook, Jack Whitehead, Marc Parmentier, Marc Spiegelman, Einat Aharonov, Jun Korenaga, Mike Braun, and Matthew Jull are geophysicists who patiently helped me. Geochemist Ken Sims overlooks my ignorance of what an activity ratio really is. Gene Yogodzinski pretends to forget that I have never actually been to the Aleutians. And Henry Dick—Tough? Supportive? Fratricidal? We are all siblings in Henry's dysfunctional family. Last but not least, I thank Greg Hirth. We've done the best of projects together, deploying the Giant Tripod and BOLO, the Blimp for Onland Oceanography. Greg is neither intimidating nor intimidated. He follows his famous father's footsteps, but doesn't feel overshadowed. There's virtue in exploring new worlds, even if they are thickly inhabited and new only to us. Today Greg and I presented work on earthquakes. Neither of us is burdened with an extensive knowledge of this topic, and there are many specialists. But it's new to us, and perhaps we will find something that is new to them. —Peter Kelemen, Woods Hole Oceanographic Institution, Woods Hole, Mass.