One of the great rewards of academic life is the association with students who stimulate, challenge, and blur the roles of teacher and student. David Bercovici, a James B. Macelwane medalist, was one of those rare students during his years in graduate study at the University of California at Los Angeles. It is even more satisfying when a student like David becomes a respected colleague and close friend. Accordingly, it is a special honor and privilege for me to present the citation for David's Macelwane award. David received his Ph.D. in geophysics and space physics from UCLA in 1989. His dissertation, A Numerical Investigation of Thermal Convection in Highly Viscous Spherical Shells with Applications to Mantle Dynamics in the Earth and Other Terrestrial Planets, constituted David's first major contribution to geodynamics. By adapting a numerical code developed by Gary Glatzmaier to study convective processes in the Sun so that it could simulate convection in the interiors of planets like the Earth, David was able to present a picture of what convection might look like in the Earth's mantle. This was the first time anyone had produced a realistic model of mantle convection, one that accounted for the highly nonlinear and fully three-dimensional nature of convective motions in spherical geometry. Few of us have done breakthrough research as a graduate student and even fewer have had the covers of Science, Nature, and Geophysical Research Letters to our credit even before we received the Ph.D. degree. David Bercovici has done all these things. Believing that he had a good thing going, I tried to persuade David to continue his numerical studies of mantle convection, but he had another agenda; upon receiving his Ph.D., he accepted a postdoctoral appointment at Woods Hole Oceanographic Institution and began a new phase of his career. David apparently did the wise thing by ignoring my advice; after all, he has received the Macelwane Medal. While at Woods Hole and later at the University of Hawaii, where he has been a professor since 1990, David has taken a different approach to studying geodynamics, one that has relied more on simple analytical models and laboratory experiments rather than on large numerical calculations. In these more recent studies, David has displayed unusual intuition and physical insights that probe directly the basic causes and consequences of geodynamical phenomena. One of his recent focuses has been on those elusive yet captivating structures known to solid Earth geophysicists and geodynamicists as `mantle plumes.' David has investigated the possible initiation of mantle plumes from the D layer at the base of the mantle and has found that starting plume heads can stall and linger for times as long as a 100 Myr before lifting off and ascending into the mantle. Before liftoff the large plume heads would appear to seismologists as strong lateral heterogeneity in the structure of D. On their way toward the surface, plumes must first pass through the transition at a depth of 660 km that separates the upper mantle from the lower mantle. David has recently proposed that owing to a possible viscosity contrast between the upper mantle and the lower mantle, a plume head would separate from its trailing conduit upon reaching the base of the upper mantle. The starting plume head would continue its ascent to the surface, and the conduit would form a second plume head at the interface between the upper mantle and the lower mantle that would eventually lift off the interface and rise to the surface. David has offered this theory as an explanation for why some flood basalt provinces display two distinct times of major eruptions separated by tens of million years. He showed that the mechanism works in a simple laboratory demonstration with fluids of different viscosity. David also developed a new gravity-current theory to model the effect of cooling on plume heads spreading beneath the lithosphere. He used this theory to infer that the thermal and chemical anomalies of plume heads can become separated as the plume heads spread; this prediction may account for the spatially separated melting and geochemical anomalies such as the Galapagos and the Marquesas hotspots. All of these efforts are marked by their originality. New ideas generate excitement and open up new research directions, and David's papers on mantle plumes have this quality. A second and major focus of David's recent work is nothing less than the outstanding unsolved problem in geodynamics: How can the theories of plate tectonics and mantle convection be reconciled? In other words, how does plate tectonics arise in a natural, self-consistent way as the surface expression of mantle convection? A fundamental, related question is what causes toroidal or strike-slip motion in a system dominated by buoyancy-driven flow. The answer to this problem is still in the future, but David has written several papers in the last 3 years that have put us on the correct path toward the solution. In fact, he has shown that the answer must lie in the exotic rheological behavior of mantle rocks, in particular that self-lubrication mechanisms, which might arise through the combination of shear heating and strongly temperature-dependent rock viscosity, can produce platelike deformation. He has done this not with a huge and resource-consuming numerical calculation but with simple models that are almost, but not quite, back-of-the-envelope exercises that bring out and clarify the basic physics of the problem. This is classic David Bercovici; he thinks deeply about the fundamental processes in geodynamics and designs a simple theory or laboratory experiment to elucidate the physics. David has done all of this, and more, without any apparent effort. He is the most laid-back, unperturbable, high achiever that I know. Had I not known him before he went to Hawaii, I would attribute his relaxed mode of operation to the atmosphere of the islands. David is down-to-Earth, without airs or pretensions, and the AGU's Macelwane Medal Committee couldn't have chosen a nicer person to receive this award. For all these reasons and others that went unsaid, I am proud to present David Bercovici as recipient of the Macelwane medal for basic and insightful contributions to the dynamics of the mantle and lithosphere. —GERALD SCHUBERT, University of California, Los Angeles

Thank you very much, Jerry, for that generous, perhaps overly generous citation. I am honored to accept this James B. Macelwane award from AGU. There are many people throughout my life whose influence I wish to acknowledge, but of course I'll probably neglect many out of pure oversight. While an undergraduate at Harvey Mudd College, I was greatly influenced by the late Ted Stoddard, a nuclear physicist who was enamored of the physics of the Earth. Ted took pity on a big slow football player and introduced me to the field of geophysics; he undoubtedly thought I'd be able to master it more readily than relativistic quantum mechanics. In fact, Ted Stoddard initiated many other Harvey Mudders into the world of geophysics, such as Greg Lyzenga, Coort Voorhies, and Dave Caress, to name a few. If the truth be told, I was a less-than-mediocre undergraduate student. Not until I was at the University of California at Los Angeles for a year or so did I eventually grow up, most notably through the patience and generosity of Jerry Schubert. Luckily (for me), we shared a pragmatic approach to doing science and a joy of writing that led to a fruitful collaboration. Jerry is an outstanding member of our community, a great example of creativity, productivity, and amazing diversity. I have continued to treasure his friendship and wisdom even after leaving UCLA. My years in graduate school and after were also strongly influenced by my collaborations at the Los Alamos National Laboratory, in particular with Gary Glatzmaier, who to this day remains a close friend. I also gained an experience rare for most graduate students through the Institute of Geophysics and Planetary Physics/Los Alamos Mantle Convection Workshop; there I was able to discuss ideas and get advice from the likes of Rick O'Connell, Peter Olson, and Dave Yuen. The encouragement and support I have continued to receive from Rick, and especially from Peter and Dave, have been extremely important to me. While at Woods Hole Oceanographic Institution for a postdoctoral fellow, I had the pleasure of working with Jack Whitehead and the inimitable and generous Henry Dick. In addition to gaining enough skills in fluid dynamical lab experiments to be dangerous, I obtained from Jack Whitehead the invaluable lesson of when and how to use the simplest models possible, and in turn, how to persuade geologists not to be offended by them. My 6+ years at the University of Hawaii have been outstanding. My colleagues and students there have been a joy to work with. I have gained greatly from discussions, arguments, and friendships with a list of people too long to recite here, although Paul Wessel, Stu Weinstein, and Rodey Batiza deserve special mention. I also owe a great deal to the support of Fred Duennebier and Greg Moore, who jointly (and somewhat haphazardly) nominated me for this award. Although I was often warned about the isolation of living in Hawaii. That is the infamous `rock-fever,' I have personally never felt it. The awesome beauty of my home state never ceases to amaze me, and I always miss it enormously when I travel. I also enjoy seeing my children grow up in a place with such a unique and rich culture and history. I realized one day that we live in a place like no other when my (then 5-year-old) daughter Sarah said that she `wished there could be another salami warning so that she could miss school.' After a minute I realized she was referring to the 4-inch-high tsunami that closed down the state in October of 1994. In the end, I owe much to my mother and father who ran a somewhat bohemian but intellectually stimulating and demanding household. My mother, a psychologist, gave me her common sense and logical abilities, while my father, a screenwriter and novelist, instilled in me a love of writing. However, I don't think my parents ever quite knew what I was studying and often would say, `David, you're a physics major, fix the trash-compactor.' Unfortunately, my father passed away just a few months before I was informed of this award. He would surely have reveled in this ceremony. Naturally, I owe the most to my wife, Julie, who provided an infinite well of support and friendship and love through many hard times in graduate school and afterward, and whose bearing and raising of our wonderful children, Sarah and Hannah, gives me the invaluable perspective that mantle convection is by far and away not the most important thing in my life. Rather than close, I would like to take this opportunity to editorialize a bit, especially since this is a captive audience and Eos is more or less obligated to publish this speech. The last several years have seen a growing antipathy toward basic research by politicians and much of the public. Earlier this year, Neal Lane, Director of the National Science Foundation, implored scientists to essentially hit the pavement and make lay people and politicians aware of the usefulness of basic research. This is an important notion, but also (knowing myself and many colleagues) fairly impractical. For various reasons, most of us are not likely to take time out of our day to write to our congressman. In truth, one of the primary ways in which most scientists contact and serve the public, the most profound method by which we disseminate the fruits of our research, is not by lobbying and popular speeches; it is, and especially at universities, through undergraduate education. Now, I am not about to demand that we teach more undergraduate classes or do a better job of teaching. However, I will suggest a very simple and not very new solution that is mutually beneficial to students, the public, and scientists. It is simply involving, in fact literally hiring, undergraduates in our research projects. Many scientists and institutes do, in fact, take undergraduate research very seriously, and NSF itself has several programs to support such endeavors. Nonetheless, the effort could and should be expanded greatly. There are many extremely important products of undergraduate research. Naturally, it benefits our research projects, and it provides a legitimate link between research and education. Perhaps most importantly, however, undergraduate research gives students firsthand experience in how to apply their education; it lets them witness and participate in the excitement of doing original science, of discovering something new, of learning how to solve heretofore unsolved problems. Although many of these students will not go on to become scientists, they will have gained an important lesson in original thought. From a more practical perspective, they will go on to become voters and possibly politicians themselves. With their research experience, they will know that scientists are not simply selfish eggheads who closely guard the keys to the ivory tower. When undergraduate students are actually gainfully employed on research projects, then the benefits to all are even greater and more tangible. In particular, the financial aid provided by research dollars will be considered kindly by all the powers that be, especially parents. Many people may not understand the research we do, but they will certainly appreciate its value if it helps pay for and improve the quality of their children's education. If the scientists amongst the more than 30,000 members of AGU itself who could employ one undergraduate did, it would actually be equivalent to supporting almost the entire undergraduate student body of a major university. Undergraduate education in this country needs to be reinvented, and our involvement through undergraduate research would be a vital contribution that would be beneficial both to the public and to the survival of basic science itself. Thank you for bearing with me, and I thank AGU and its members for this Macelwane medal and the chance to pontificate without interruptions or questions. —DAVID BERCOVICI, University of Hawaii, Honolulu