Don has been a role model for me and for many of us in marine geophysics. I came to know Don through his pioneering work and his leading role in the Mantle Electromagnetic and Tomography (MELT) experiment, which transformed both marine seismology and our understanding of the melting processes beneath the ocean spreading centers. It was a technological breakthrough, which became a model for future marine seismology experiments. The MELT experiment demonstrated that the melt extends down to 150-kilometer depth and that the melting is asymmetric beneath the ridge axis.
While we were still admiring the results from the MELT experiment, Don led another important experiment, Gravity Lineations, Intraplate Melting, Petrology and Seismology Expedition (GLIMPSE), to study the origin of the linear chain of seamounts and volcanic ridges present only on the Pacific plate side orthogonal to the fast spreading East Pacific Rise. Based on the analysis of seismological, gravity, and bathymetry data, he challenged the existing model of the origin of these ridges by small-scale convection in the mantle and proposed a new model requiring viscous interfingering of enriched material from the mantle upwelling related to the superswell.
It seems that marine geophysics was natural to Don; he started making fundamental contributions during his Ph.D. and wrote a seminal paper on the relative importance of driving forces (ridge push and slab pull) of plate motion. This model helped him to quantify the oceanic mantle anisotropy due to plate motion as it cools away from the ridge axis. He was first to recognize the importance of plate bending in the outer rise leading to earthquake generation.
Don realized the importance of analyzing integrated seismological, gravity, and bathymetry data to determine the anisotropy structure of the Pacific upper mantle and the effective elastic thicknesses of the East African plate. Using gravity data, he discovered the idea of the mantle Bouguer anomaly, separating the effect of crustal thickness from the mantle, allowing us to identify the effect of mantle upwelling beneath ridge axes and plumes and downwelling, such as the Australia–Antarctica discordance zones. He also developed the concept of a bull’s-eye at slow spreading centers.
My recent encounter with Don has been on the imaging of the oceanic lithosphere–asthenosphere boundary (LAB), where he discreetly and humbly enlightened me with different conflicting models of the LAB. I would like to thank Don for providing leadership over the last 40 years and invite you to join me in congratulating him on receiving the 2017 Maurice Ewing Medal, a well-deserved honor.
—Satish Singh, Institut de Physique du Globe de Paris, Paris, France
I’m honored to receive this year’s Maurice Ewing Medal. It is a very nice semiretirement gift to receive as I embark on the emeritus phase of my research career. Thanks to AGU and the Office of Naval Research and, particularly, to those who wrote letters in support of my nomination.
This honor really should be a community recognition for all the infrastructure and technological advances developed by others that have made my research possible. Multibeam echo sounding reveals the basic seafloor structure, GPS allows us to actually know where we are, and satellite altimetry makes it possible to plan detailed surveys in advance. There have been great advances in ocean bottom seismographs that make probing the mantle beneath the seafloor possible with much better resolution. The Incorporated Research Institutions for Seismology data management center has made accessing and processing seismic data much easier. And, of course, none of this would have been possible without ships and their crews and technicians. The capability and comfort of research ships in the academic fleet have improved tremendously since my first cruise on the Chain, a converted minesweeper.
Almost all of my research has been done in close collaboration with students, postdocs, and other colleagues. It is totally unfair to single out just a few individuals among them, because they all contributed immensely through hard work and innovations of their own—but I’ll do so anyway. Early on, Seiya Uyeda showed me how much fun science can be as we worked together trying to understand the driving forces of plate tectonics. Dan Scheirer and I had several cruises together; he taught me by example how to be an organized, effective chief scientist. My students and my colleagues at Brown, especially Marc Parmentier, Karen Fischer, and Greg Hirth, have made the past 40 years delightful. My Ph.D. adviser, Frank Press, taught me to tackle important questions, to critically evaluate my own work, and to be bold and unafraid of being wrong or making mistakes. I seem to have learned this last lesson well. I’ve told my students that I couldn’t retire until I published a paper with no mistakes, but now I have gone ahead and retired anyway. But since I expect to remain active in research for another decade or so, there is still hope.
Finally, I’d like to thank my wife, Roberta Ryan, who has tolerated my seagoing adventures and has been a wonderful partner.
—Donald W. Forsyth, Brown University, Providence, R.I.