Ronald T. Merrill

2002 John Adam Fleming Medal Winner

University of Washington, Seattle

Ronald T. Merrill was awarded the Fleming Medal at the AGU Fall Meeting Honors Ceremony, which was held on 8 December 2002, in San Francisco, California. The medal is given for original research and technical leadership in geomagnetism, atmospheric electricity, aeronomy, space physics, and related sciences.


“Ron Merrill was born in Detroit, Michigan. He obtained a master’s in mathematics from Ann Arbor and then decided to try Earth sciences, going to Berkeley to obtain his Ph.D. under John Verhoogen. With such a background, it is not surprising that Ron has made his mark in solid Earth geophysics. I first met him in 1974, when he worked with me in Australia while on his first sabbatical leave from the University of Washington. Our scientific collaboration has thus extended over nearly 30 years, and it is a great privilege for me to have been asked to present the citation for his award of the John Adam Fleming Medal this evening.

“Ron has made significant contributions in two very different areas of geophysics. He has made original and fundamental contributions to our understanding of rock magnetism, and the processes by which rocks acquire their magnetization and so preserve a record of the ancient geomagnetic field. He was a pioneer in relating paleomagnetic directions recorded in rocks to dynamo theories of the origin of the geomagnetic field. He has been a leader in this field for the past 25 years and has been the senior author of two books that have played an important role in bringing together these diverse disciplines in solid Earth geomagnetism.

“In rock magnetism, Ron was the first to demonstrate nonreproducible self-reversal in rocks. He was the first person to investigate the problem of low-temperature oxidation of magnetite, now known to be quite common in magnetite-bearing rocks. The understanding of the magnetic effects of chemical changes in rocks is of the utmost importance for the interpretation of paleomagnetic results, and Ron was one of the pioneers in this field. In the 1970s, Ron and his students published a series of papers providing the fundamental parameters for the acquisition of TRM and ARM in rocks, including the basic grain size properties. He was the first to realize that the demagnetizing field was in-correctly treated in magnetic studies. This led to the application of micromagnetics to rock magnetic theory and opened up a new era in rock magnetism. Bringing micromagnetic concepts into rock magnetism involved ideas such as LEM states and transdomain remanence. These applications in rock magnetism were the first in physics and predate their use by physicists in magnetic materials. Ron was the first person to use renormalization group theory in rock magnetism, a first in geophysics!

“When Ron first visited me in Australia, we had many discussions on the use of the dispersion observed in young lava flow successions as a measure of paleosecular variation. We wrote our first joint paper on this topic, published in Reviews of Geophysics in 1975. In this review paper, Ron’s major contribution, was to make the first attempt to relate such measurements to dynamo theories. This was the first of a set of pioneering papers leading to the publication of our book in 1983 entitled The Earth’s Magnetic Field: Its History, Origin and Planetary Perspective. Ron was the driving force and senior author of this classic book that relates dynamo theory to the ancient magnetic field measurements derived from paleomagnetism.

“Ron has continued to be at the forefront of this new and exciting dimension in relating paleomagnetic data to dynamo theory. This has been on three main fronts: paleosecular variation, analysis of the time-averaged paleomagnetic field, and the analysis of geomagnetic reversal sequences. At this time, Ron also started to work with my younger colleague Phil McFadden. I understand that we are together referred to as ‘M-cubed’ or the ‘three Ms.’ A major breakthrough occurred when it was realized that variations in the dipole and quadrupole (primary and secondary) families from dynamo theory could be used to model the dispersion of paleomagnetic data from lava flows. The relationship between lower mantle convection and geomagnetism through plumes, Taylor instabilities, and core-mantle interaction led to the realization that the Cretaceous superchron is not a reflection of any difference in stability of the normal and reverse fields. Rather, the reversal process gradually slowed down and then just stopped for a while, because of changing core conditions that eventually passed through a critical stage. With the rapid advances in this field, Ron was again senior author in a complete rewrite of the 1983 book, now written jointly by the ‘three Ms.’ This was published in 1996 as The Magnetic Field of the Earth: Paleomagnetism, the Core, and the Deep Mantle.

“Most of our knowledge of the history of the Earth’s magnetic field has been derived from studies of the magnetization that rocks have acquired over millions of years of Earth history. Ron’s contributions have been fundamental to our understanding of the processes and theory by which rocks acquire their magnetization. Such understanding has been vital in interpreting paleomagnetic measurements in terms of variations in the geomagnetic field with time. His pioneering work in relating these measurements to dynamo theory of the origin of the field has opened up a whole new dimension in solid Earth geomagnetism.

“Mr. President, ladies and gentlemen, it is my honor to present to you the winner of the 2002 John Adam Fleming Medal, Ronald T. Merrill.”

—MICHAEL W. MCELHINNY, Port Macquarie, Australia


“Thank you, Mike, for your generous words. I feel greatly honored to receive the John Adam Fleming Medal. I am also delighted and flattered to have such a longtime friend and colleague deliver my citation.

“John Denoyer, a faculty member at the University of Michigan, gave me my first job in geophysics and persuaded me to go to graduate school at the University of California at Berkeley. When I entered Berkeley, John Verhoogen was graduate student advisor. He offered little support for my dream of doing field geology while I climbed mountains, and he insisted that I take a class in E&M. I was tempted to end my career at Berkeley on the spot. I knew that electricity and magnetism were not for me! Eventually Verhoogen became my advisor, and this was one of the best career decisions I have ever made. I also began my friendships with Subir Banerjee, Rob Coe, and Ken Hoffman while at Berkeley, and they have continued to contribute to my scientific growth ever since. Interestingly, all of us eventually ended up serving terms as AGU section presidents. Not long after I left Berkeley, I met a student of Mike McElhinny’s, Charles Barton. Charlie not only became a lifelong friend and colleague, but he also has provided a continual steam of cartoons that I have used in my talks for the past quarter century.

“Perhaps the most important talent I have is my ability to pick good colleagues. Certainly, I need to thank all of my graduate students, my University of Washington colleagues, and also the faculty at the Research School of Earth Sciences of the Australian National University, where I have often visited. I appreciate the generous help I have received over many years from Dave Dunlop, Mike Fuller, Sue Halgedahl, and Bruce Moskowitz in rock magnetism; Gary Glatzmaier and Paul Roberts in dynamo theory; Mike Brown and Frank Stacey in mineral physics; Ken Creager in seismology; and John Booker, Cathy Constable, Dennis Kent, Minoru Ozima, and Dave Stevenson in a variety of subjects. I apologize to the many scientists who I have not explicitly mentioned but who have also significantly contributed to my personal and intellectual growth.

“Naturally, there are a few individuals who require special mention. The first of these is my citationist, Mike McElhinny, with whom I have been working since 1974. It is true, as many of you have probably suspected, that Mike and I drafted our first manuscript in a bar after a long field trip in Australia’s outback. Around 1980, Mike told me that he was trying to hire a paleo-magnetist who was a reader at the University of Rhodesia (now the University of Zimbabwe). He assured me that I would like this unusually brilliant scientist. Immediately, I knew I would dislike this man. After all, what role could I play in our scientific team with Phil McFadden around? Surprisingly, we formed an instant friendship, in part, because we felt we might be the only two people on the planet who believed there was no difference in stability between Earth’s normal and reverse polarity states. Our friendship has continued to grow over the past two decades, a time during which Mike, Phil, and I have published many papers under a variety of permutations and combinations of authors. Finally, I wish to thank my family, my sons, Craig and Scott, and especially my wife, Nancy. Without Nancy’s love and continual support, I would not have received this medal.”

—RONALD T. MERRILL, University of Washington, Seattle