It is an honor to introduce Peter Ulmer, one of the winners of the 2022 Norman L. Bowen Award of the AGU Volcanology, Geochemistry, and Petrology section. Peter’s breadth of approaches spans experimental petrology, field geology, and magma rheology in a truly exceptional way. Peter started as a field petrologist working on hydrous plutonic rocks in the Alps. The difficulty in retrieving petrological system variables in hydrous magmatic systems and understanding the role of water in magmas inspired his groundbreaking experimental studies ever since. Peter is widely known for exploiting fundamental questions by innovative and carefully designed experiments on subduction zone processes and magma generation and differentiation, with a great eye for big problems. His experimental demonstration of serpentine stability to mantle depth shaped research on volatile cycling in subduction zones for the past 25 years. His discovery changed the perception of hydrous arc magmatism and the subduction zone water cycle and inspired the development of novel experimental and analytical techniques on determining the composition of subduction zone fluids and melts around the second critical end point at high pressure. Peter explored the phase relations of multiply saturated primary hydrous basaltic magmas and their intermediate to felsic distillates that form much of the juvenile continental crust. By simulating both equilibrium and fractional crystallization, Peter showed that fractional crystallization provides in many cases a much closer match to natural rocks, most notably for arc lower crust. The full breadth of these results on transcrustal magmatic systems is yet to be explored. Moreover, Peter’s work on the rheology of particle and bubble-bearing magmas experimentally demonstrated the non-Newtonian behavior of crystal-rich magmas, with implications for the quantitative modeling of magma conduit processes, including the important effects on volatile exsolution. In addition, and perhaps even more important, Peter is a brilliant mentor for Ph.D. students and postdocs, and—rare in academia—incredibly modest. He is an inspiration for young scientists and an extraordinary fount of knowledge on all matters experimental. The diversity, rigor, and creativity in Peter’s experimental research are an extraordinary match to Bowen’s legacy.

—Othmar Müntener, University of Lausanne, Lausanne, Switzerlan

Thank you, Othmar, for the kind citation and for more than 20 years of intense and fruitful collaboration and friendship. Thanks to those who supported my nomination and the Volcanology, Geochemistry, and Petrology Award Committee for selecting me. I am truly honored and humbled to receive the Bowen Award. Of course, this is more than honoring an individual but a career based on interaction and collaboration with numerous mentors, peers, and students. Volkmar Trommsdorff, Alan Thompson, and Ezio Callegari, all experts combining field, geochemistry, and petrology, introduced me as a student at ETH Zurich into the challenging world of petrology. Studying the Adamello plutonic complex in the Southern Alps, I realized that unraveling the formation of arc-related rocks requires more than conducting fieldwork and analyzing rocks. Alan nudged me to study The Evolution of Igneous Rocks by Bowen, which I did with limited motivation considering the “ancient” publication date. This, however, completely changed my view on how to tackle igneous rocks based on profound knowledge of phase equilibria representing the thermodynamic control on evolution and composition. Understanding arc petrogenesis requires fundamental understanding of phase relations in hydrous systems from magma generation in the mantle to differentiation and emplacement in the crust. This motivated me to apply for a postdoc at the Geophysical Laboratory, allowing me to learn the trade of experimental petrology from the very experts. Bjorn Mysen, Ikuo Kushiro, Neil Irvine, Hatten Yoder, and Joe Boyd are ultimately responsible for turning a “field guy” into something like an experimental petrologist, both intellectually and technically, and deeply influenced the way I perceive igneous processes. Back at ETH, I had the opportunity to expand the existing experimental petrology lab together with Max Schmidt and Stefano Poli constituting the nucleus of what became an established experimental lab. Thank you for your continuous support and friendship. The generous support by ETH allowed me to conduct research in the most unrestricted way and in close collaboration with great colleagues, postdocs, and motivated students. This included field campaigns to some of the most amazing places such as the Kohistan arc with Jean-Pierre Burg, Patagonia with Othmar and Lukas Baumgartner, and the Sierra Nevada with Tim Grove and Tom Sisson. Keeping a firm grip to the “ground” in the realm of real rocks is essential to identifying crucial processes and unresolved questions in Earth sciences and nourishes my fascination and passion to contribute to resolving the mysteries of continental crust formation. —Peter Ulmer, Institute of Geochemistry and Petrology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland