Citation by Arthur Sylvester, University of California at Santa Barbara
Noting that the Penrose Medal is awarded for “outstanding contributions that mark a major advance in the science of
geology,” GSA Fellows Peter Molnar, Dan McKenzie, David Scholl, and Clark Burchfiel nominated geophysicist and
marine geologist Tanya Atwater for that honor, pointing out that her 1960s and 1970s studies of Pacific and North
American plate interactions were the outstanding contributions that provided the key
breakthrough and major advance in our understanding of the dynamics of the Earth’s crust.
Many of us first became aware of Atwater’s work at an extraordinary event: GSA’s first Penrose Conference chaired by
Bill Dickinson at the Asilomar Center in California in 1968. The topic was Plate Tectonics and the Western
Cordillera. Approximately 100 scientists, all eminent scholars on western North America geology, attended. The
principal focus was the San Andreas fault system. Many specialists gave presentations that wrestled with its history
and nature. Their erudite lectures exposed wide differences of thought about its complexities and evolution and just
seemed to be repetition and rehashing of the same old ideas.
But then a modest young woman named Tanya Atwater gave a 30-minute presentation of her work on the evolution of the
Pacific Plate and how it related to western North American geologic evolution. She showed the geological world, for
the first time, how quantitative relative plate motions could be translated into geological predictions that could
be tested against known geology of western North America. The results were spectacular.
Atwater’s presentation directed everyone’s tectonic thinking away from the then generally accepted notion of crustal
fixity and special pleadings of the geotectonic cycle to a paradigm of crustal mobility and continental drift. Her
transformative message was the disclosure that since early Mesozoic time, the tectonic construction of western North
America was largely the product of boundary interactions between moving plates of the Pacific Basin and that of
Thus, by exploiting the magnetic anomalies and fracture zones in the Pacific, Atwater changed how geoscientists in
the western USA could view the geologic history of their own territory. She showed in detail how many of the
well-known geological features of the area, such as the San Andreas fault, the Franciscan Formation metamorphism,
the Cascade volcanism, and the tectonic evolution of the region in Cenozoic time, were direct and simple
consequences of the complex three dimensional kinematics which she reconstructed from the geometry of the magnetic
anomalies of the northeast Pacific Basin. Atwater showed that subduction of Farallon Plate oceanic crust beneath the
western USA must have continued until at least 29 Ma everywhere, and more recently in many areas. Rock so young had
not yet been found in the Franciscan Formation, and few accepted this prediction, until some investigators went back
into the field and looked again at the rocks. She argued that despite offsets of Cretaceous rocks, the San Andreas
fault was unlikely to be much older than 29 Ma. She was right again. Atwater also showed that extrapolation of
present-day rates led quickly to trouble. She solved this first by improving the least complicated plate
reconstruction, between the Pacific and Antarctica Plates, and then by combining global sets of reconstructions, she
linked the Pacific Plate to Antarctica, India, Africa, and North America. In this one presentation using a
quantitative analysis of the ocean floor magnetic anomalies and transform faults, Atwater reconstructed the Pacific
plate motions and their effects on the adjacent North American geologic evolution.
Tanya Atwater was just 27 at the time of her Asilomar presentation, a marine geophysics PhD student who had been
struggling against systematic discrimination of women in the world of science. She mentions that she had not been
able to apply to one prestigious American university because they “would not accept women because they viewed us as
a waste of their time”. Yet, here she was, in front of all these senior respected geologists and geophysicists,
showing for the first time that plate tectonics led to quantification of continental geology, particularly in this
most unusual western North American setting where, to quote her, “oceanic and continental realms are so completely
and intricately intertangled.”
I can say that the 1968 Asilomar audience was stunned. I know I was. I felt I had just been witness to the end of an
era of geotectonic speculations and the beginning of a totally new approach to understanding the dynamics of the
Earth via Atwater’s new world of potentially quantitative and testable geotectonic synthesis.
If you have been lucky enough, then perhaps you too have caught one of her many talks or participated in one of her
field trips exploring California’s spectacular geology. Perhaps you were one of her students. However you found
yourself in contact with Tanya Atwater, chances are that you came away with a new or more profound appreciation for
the Earth under your feet, one that is especially reinforced every time the ground shakes, rattles, and rolls.
The career contributions of most of us are compiled in incremental steps, Atwater’s have been provided in large,
high-impact strides. Important in this regard are the extra-regional implications provided by her detailed mapping
of the pattern of north Pacific magnetic anomalies published in GSA’s Pacific Basin DNAG volume. These maps and her
interpretations of them remain widely used and referenced as are her earlier signature papers detailing the
plate-boundary driven evolution of the northeast Pacific and its continental margin, and her subsequent papers about
the details of southwestern US tectonism driven by plate motion changes.
Atwater joined the UC Santa Barbara faculty in 1980 after stints at Massachusetts Institute of Technology, Woods Hole
Oceanographic Institution, and Scripps Institution of Oceanography. She received her bachelor’s degree from UC
Berkeley in 1965 and her doctorate from Scripps in 1972. During the course of her career, she participated in or led
numerous field expeditions both on land and at sea, including 12 dives to the deep ocean floor — depths as great as
two miles — in the tiny submersible “Alvin.” Atwater is also known as a trailblazer for women’s rights to conduct
oceanographic field research, a practice that was generally not allowed when she began her studies.
In the past decade, Atwater has turned her attention to making hand-crafted “animations” that graphically and
effectively illustrate several geologic phenomena, including and especially plate tectonics, that illustrate to the
professional and lay person how continental drift and plate-boundary processes constructed the rock fabric of most
of western North America. Her goal has been to educate the public in the wonders of geological science; however,
academic scientists commonly use these animations to illustrate their lectures, and they do so often without knowing
who made them.
Atwater is the recipient of numerous honors and awards, including the Newcomb Cleveland Prize from the American
Association for the Advancement of Science; the Encourage Award from the Association of Women Geoscientists;
election to the National Academy of Sciences; the National Science Foundation’s Director’s Award for Distinguished
Teaching Scholars; the Leopold von Buch Medal from the German Geosciences Society; a Lifetime Achievement Award from
the Structure and Tectonics Section of the GSA; and a Los Angeles Area Emmy for Instructional Programming. She
retired from university teaching in 2007 but continues to deliver lectures and teacher workshops, and to lead field
trips for the community.
The Penrose Medal was established in 1927 by R.A.F. Penrose, Jr., to be awarded in recognition of eminent research in
pure geology, for outstanding original contributions or achievements that mark a major advance in the science of
geology. Tanya Atwater clearly fits the Medal’s criteria and well deserves the GSA’s recognition by bestowing its
highest honor upon her.
Response by Tanya M. Atwater
And thank you, my geo-colleagues, for your encouragement, guidance, patience, and generosity over the years as I’ve
bumbled my way around the West, trying to learn your unique local and regional stories and jamming together with you
about their global implications. And thanks to Western North America, itself, for its spectacular, huge, beautiful
landscapes, that lay out the rocks in such glorious, irresistable ways.
Thank goodness for sea floor spreading, that made deep ocean floor geology so straight-forward, and for the efforts,
enthusiasm, and comradery of so many shipboard colleagues in its study.
Thanks to the timing that plopped me into the plate tectonic maelstrom, and into the disarray that was conceptual
geology just then. It seemed that everywhere we turned there was a very complicated geo-explanation that suddenly
became simpler and clearer when we placed in its plate tectonics context. It was such a great privilege to be even
a small part of that giant collaboration among geoscientists all across the disciplines and all around the world.
Thanks to my parents for giving my sisters and me the self-confidence - and the audacity - to laugh when we were told
that we, just because we were women, weren’t capable of … whatever.
I feel profoundly lucky to have had such an exciting life, in such an amazing time, surrounded by so many inspiring
people and ideas and fun. I wish the same to each and all of you.