Robert van der Hilst

1997 James B. Macelwane Medal Winner

Massachusetts Institute of Technology

Robert D. van der Hilst was awarded the James B. Macelwane Medal, at the AGU Fall Meeting Honors Ceremony, which was held on December 10, 1997, in San Francisco, California. The Macelwane Medal recognizes significant contributions to the geophysical sciences by a young scientist of outstanding ability. The citation and response are given here.


It is my great pleasure to present Robert Dirk van der Hilst as the 1997 recipient of the James B. Macelwane Medal of the American Geophysical Union. By virtue of his significant scientific contributions, Rob has established himself as an outstanding young scientist of great potential.

“My collaboration with Rob began in 1987 when Guust Nolet and I successfully applied for a NATO grant to support joint research on problems in seismic tomography. As a result of this collaboration, Rob produced, largely by his own efforts, a series of enormously important research papers that advanced our understanding of a fundamental problem in solid earth geophysics: Do the upper and lower mantles function as independent convective systems or does large-scale material flux occur between them? This issue is a long-standing one, with major implications for the thermal and chemical evolution of the planet. For years, there were few real constraints on this problem, but Rob’s elegant studies using seismic tomography to see how cold, and therefore higher velocity, slabs behave near the boundary between the upper and lower mantle at 670-km provided a breakthrough in this important area of research. His results showed that some slabs penetrate this discontinuity, whereas others deform in a variety of fascinating and complex ways. These results have become crucial to all discussions of mantle dynamics and deep earthquakes. Rob’s beautiful color images are thus standard parts of talks and papers by almost any researcher on these topics.

“Rob’s recent paper, “Evidence for deep mantle circulation from global tomography,” published in Nature, can be seen as the culmination of years of effort and may have finally put to rest the debate about layered versus whole mantle convection. His development of high-resolution results for the entire mantle provides convincing evidence of features in the lower mantle related to past subduction, i.e., the 660-km discontinuity is not a barrier to flow. He has been able to interpret these results using mantle flow simulations and reconstructions of past plate motion that are derived from paleomagnetic data.

“Rob’s education at the University of Utrecht gave him a solid background in geology and theoretical geophysics, with applications to seismology, tectonophysics, and geodynamics, that prepared him well for a broad range of research. While working as a Postdoctoral Research Fellow with David Gubbins at the University of Leeds, Rob’s budding career did not go unnoticed. Among several posts offered to him at that time was one in Australia to work with Brian Kennett, where he initiated a new study of the seismic structure of the lithosphere and mantle beneath Australia. The SKIPPY seismometry experiment was really Rob’s brainchild and satisfied his tectonic interests while employing new and complicated interpretation techniques. The rest is history, as a sequence of successful SKIPPY deployments resulted in new data that has not only revolutionized our understanding of the geodynamic evolution of that continent, but has also profoundly influenced our general understanding of continental assemblage. It is not surprising, therefore, that after this solid beginning as a research scientist Rob was only recently heavily recruited and accepted for a post on the faculty of the Massachusetts Institute of Technology.

“Rob is diligent and thorough in all aspects of his work. I believe he stands out among peers in his age group because of his unique combination of versatility, intelligence, pleasant personality, and solid background in both physics and geology. His leadership and experience in field work also give him a dimension that is often lacking in young seismologists, but which is needed in the upcoming generation of research scientists in our field. Rob is also remarkably mature in his scientific and personal development. He typically puts the scientific question first and will then search for the best means to answer it. If he decides he has to learn a new technique, or even a new field, he will do so—and he is one of the few who have sufficient background to be able to adopt this style of work with success.

“I am proud to present Robert Dirk van der Hilst as recipient of the James B. Macelwane Medal. As no one else, he has made the important discoveries about the fate of subducting slabs and brought profound new insight to the problem of global circulation. He is truly one of those rare individuals whose work in the few years following his Ph.D. has made an immediate and lasting impact of major proportions. These qualities—together with the breadth of his scientific activities are the material from which medalists are made.”

—E. R. ENGDAHL, U.S. Geological Survey, Denver, Colo.


“Thank you very much, Bob Engdahl, for your generous citation. It is a tremendous honor to receive the James B. Macelwane Medal, and I am particularly pleased to share this moment with you. I am very grateful for the American Geophysical Union and its James B. Macelwane Medal Committee for their confidence and for bestowing this honor on me. I am proud to be one of the few Dutchmen to receive this award, but I realize that many before me would also have been deserving recipients.

“I first learned about geophysics when my tenth-grade geography teacher showed a video on earthquake seismology and plate tectonics. Fascinated by the subject, I asked him after class for more information and he referred me to work by Vening Meinesz and others. (Promoting our science at high schools works!) That was it. A couple of years later I went to Utrecht University—an excellent breeding ground for geophysicists—to learn more about Earth sciences. I did both my graduate and undergraduate work in Utrecht in an exciting period of expansion of the geophysics program under leadership of Nico Vlaar, and later, Guust Nolet and Rinus Wortel. In addition to deciphering the signals from Earth’s fascinating deep interior, I loved working “hands-on” with rocks at the surface, and I thank Reinoud Vissers for sharing his enthusiasm for structural geology during many field hours together in southern Africa and Spain.

“Under the supervision of Nico and Rinus, I began a graduate research project that aimed to study the tectonic evolution of the Caribbean region. We wanted to understand the relationship between plate kinematics at the Earth’s surface and the structure of (and driving forces in) the underlying mantle. This put me on the seismic imaging track that I would follow for many years to come. I was very fortunate to be able to work with Wim Spakman. A graduate student at the time, Wim quickly became the “de facto” advisor for most of my Ph.D. work and by standing on his shoulders I could see further and make the discoveries for which I am honored today.

“Both in Utrecht and later in Princeton, Guust Nolet has been a continuous source of inspiration. His pioneering use of an array of (semi-) portable broadband seismometers (NARS) for continental imaging was a prime example for the seismometry project that I would later run in Australia. Following Guust’s advice, in 1987 I attended a summer school that would change both my personal and professional life. The introduction to Bob Engdahl of the U.S. Geological Survey initiated a decade of immensely rewarding and enjoyable collaboration. The meeting was also the start of my relationship with Alet Zielhuis, who has remained my dearest companion in life and research ever since.

“I first visited Bob at the survey in the winter of 1987 & 1988; I am sure I gained more from that first visit than Bob did (other than him having good laughs about funny Dutch expressions), but we were both excited about the potential for improving seismic imaging by exploiting different types of seismic data. In 1990 we started the challenging task of reprocessing the vast amount of existing catalog data with the objective of improving source location estimates and associated travel times. In the past five years we have used subsets of this developing data set for inversions of mantle structure of selected subduction systems, but the global data set has now also been used in investigations of aspherical structure of the entire Earth’s mantle. I thank Bob for the many years of friendship and unselfish collaboration.

“Working at different institutes in different countries presented me with opportunities to venture out, try new approaches, and look at previous work with a fresh look. I left Utrecht to work as a postdoctoral fellow with David Gubbins at the University of Leeds. I thank him for giving me the freedom to do what I wanted to do, for involving me in the seismometry project he had just initiated in New Zealand, and for introducing me to the truly fascinating world of geomagnetism. In Leeds I studied the fate of subducting slabs of lithosphere beneath the northwest Pacific island arcs, which formed the foundation for my later studies of the influence of relative plate motion on the interaction of downwellings (slabs) with mantle stratification.

“After two years in Leeds, Kurt Lambeck and Brian Kennett persuaded Alet and me to move down under to join the faculty of the Research School of Earth Sciences of the Australian National University. I am indebted to Brian for offering me the opportunity to execute my ambitious ideas for a seismometry project to study the Australian continent and underlying mantle. He gave me the responsibility of managing what is now known as the SKIPPY project and I am proud to say that over the years we pulled off a project that is now in the process of changing our understanding of the continental lithosphere of Australia. The Australian National University proved to be an ideal base for such a study, in particular because of its field-oriented research and outstanding technical staff. Special thanks go to Doug Christie and John Grant, with whom I spent many pleasant weeks on endless roads in the Australian Outback. Among many other friends and collaborators, I want to thank Kurt and Meg Lambeck, Jean and Myriam Braun, Malcolm Sambridge, Geoff Davies, Ross Griffiths, Widi and Lika for the good time we had in Canberra.

“Delighted and proud, I joined the faculty of the Massachusetts Institute of Technology two years ago. MIT is an amazing place for scientific endeavor. It is a privilege and thrill to be here and to work with such gifted students. I thank my Head of Department, Tom Jordan, as well as my other colleagues for the confidence, support, and for creating such a stimulating academic environment. At MIT I hope to continue the use of seismological studies along with other geophysical observables and geological data to address pertinent geodynamical issues. With world leaders in many Earth science disciplines, MIT is the outstanding place for such an integrated approach.

“One of the pleasures of academic life is working with students. At ANU, Sri Widiyantoro (“Widi”) and I worked on mantle structure beneath Indonesia, and Widi was instrumental in the construction of the first global tomography models based on the new data set that Bob, Ray Buland, and I had produced. Widi graduated in 1997 and is now back at his lectureship at Bandung Institute of Technology, Indonesia. Geoff Clitheroe and I used SKIPPY data to show that the seismic anisotropy of the Australian continent is more complex than in many other continents. In continued collaboration with my Australian colleagues, at MIT I investigate continental structure and evolution with Frederik Simons (from Leuven University, Belgium). Hrafnkell Karason (from the University of Iceland, Reykjavik), and I use improved tomographic models to further our understanding of global geodynamical processes.

“Finally, I wish to acknowledge my family. I thank my parents for their love and support and for trying to understand life in academia. (A “classic” by my father many years ago: “How much does a journal like Nature pay you to publish your article?”) Most important, I thank Alet. Her love has enabled me to carry on in trying times and to make the career moves that I made; I know that some of them were not in her interest and that living far away from her family in the Netherlands has been hard for her. I am very grateful for everything she is for me and for our two wonderful children, Marije and Jelle, who bring perspective and joy to our lives. With them I celebrate this award.”

—ROBERT VAN DER HILST, Massachusetts Institute of Technology, Cambridge, Mass.