Casey Moore, cocreator and leader in the field of subduction zone science, passed away in March. Casey was recognized internationally for his contributions to the geology of subduction zones and in understanding the evolution of sediments as they become rocks in the seismogenic zone, where earthquakes originate. He was awarded fellowships from AGU (2013) and the Geological Society of America (1984), and he received the Francis P. Shepard Medal for Marine Geology, awarded for “excellence in marine geology,” from the Society for Sedimentary Geology in 2013. The Geological Society of Japan recognized his outstanding contributions with its International Prize in 2011.
Arriving at the Cusp of a Revolution
Casey spent his youth enjoying the beaches of Southern California. He arrived at Princeton for graduate work in 1968—just as Harry Hess, Jason Morgan, and Fred Vine, all at Princeton, were developing and refining the theory of plate tectonics. He completed nearly 90 days of fieldwork in the summer of 1970 on Sanak and Shumagin Islands, which sit on the seaward edge of Alaska’s Aleutian Arc, where the Pacific plate subducts beneath the North American plate. As a result of this fieldwork, Casey confirmed that deep-sea sediments from the subducting oceanic plate had been deformed and added to the upper plate.
These findings supported the hypothesis of plate tectonics and provided new insights on the growth of continents. The results were published a year after Casey graduated from Princeton in 1971, as he was starting his teaching career at the University of California, Santa Cruz (UCSC), setting the stage for 5 decades of research on modern and ancient subduction zones.
Subduction at Sea
Casey distinguished himself as an exceptional field geologist as well as a major leader in ship-based research. He led or participated in dozens of field-based expeditions to exhumed accretionary prisms—wedges of sedimentary material that accumulate at the interface between two colliding tectonic plates—around the world. He was a cochief or science party member on more than 20 research cruises in Barbados, Cascadia, Sumatra, Alaska, Japan, the Indian Ocean, and the Gulf of Mexico.
His participation and leadership in ocean drilling were integral in ushering in a new era of scientific drilling to study subduction zones, beginning with Legs 25 and 31 of the Deep Sea Drilling Program in 1972 and 1973. Casey was also reportedly the first person to hold a Brunton compass with clinometer to the window of the Alvin submersible so that he could measure the dip of the thrust faults revealed in submarine canyons offshore Oregon.
Casey had the rare talent of being able to seamlessly integrate shipboard data, core descriptions, and geophysics with field observations from exhumed rocks. He contributed formative concepts on the interaction of fluids and clays during deformation; these concepts underpin our understanding of fault strength in shallow subduction zones. His research was the first to demonstrate the importance of rapid effective burial of subducting sediments in controlling pore pressure and changes in rock strength. He also developed or adapted methods of studying stress, strain, volume change, and the formation of penetrative fabrics in rocks (patterns of mineral orientation that form when the sediments or rocks are deformed) to the unexplored, water-rich settings of shallow subduction zones.
Casey even applied his interest in fault fluids and deformation in his own backyard, where he characterized the deformation of sediments saturated with water and hydrocarbons along the San Gregorio Fault in California. Combining insights from subduction and strike-slip plate boundary faults, Casey’s understanding that the sedimentology and structural evolution of trench sediments were intrinsically coupled and needed to be studied as integrated processes is still influential and relevant today.
A Thirst for Knowledge
Casey’s leadership was exemplified by what he did not do as much as by what he did. It was never Casey’s style to promote himself or to patrol his scientific turf. He enjoyed a healthy discussion and would marshal evidence from geology, hydrogeology, geophysics, and geochemistry to support his positions, always good-naturedly.
Throughout his career, he kept adding to his breadth of abilities. He regularly dug in deep to learn new methods and techniques so he could add new sources of data to his lifelong synthesis of subduction processes. He did so with remarkable humility, studying appendixes of methodological details and consulting experts, including graduate students astounded that he had approached them for help. He never became entrenched in his past interpretations, and he took joy in seeing them overturned by new insights from his own or others’ work.
His excitement for discoveries and enthusiasm for fieldwork inspired many young scientists. He routinely turned over his best project ideas to his advisees and gave his students complete creative control. He avoided recognition until he couldn’t find an escape, at which point he accepted it graciously. He always focused on the importance and fun of understanding tectonic processes through observations of all kinds.
By example, he taught his students to value interdisciplinarity, talk to everyone, and listen carefully to all ideas. Casey’s legacy shines through the successes of his advisees in a broad range of fields. His students and postdocs are found in the leadership of the International Ocean Discovery Program, heading major research institutes and geoscience departments, winning teaching awards at undergraduate-serving institutions, and starting their own companies.
A Lasting Legacy
Casey spent his entire academic career at UCSC, where he served as chairman of the Earth Sciences Board from 1984 to 1986. He was a distinguished lecturer for the Joint Oceanographic Institutions/U.S. Science Advisory Committee (JOI/USSAC, 1992–1993) and NSF MARGINS (2006–2008), and he served on the Chikyu +10 Steering Committee and the Chikyu IODP Board for the Integrated Ocean Drilling Program (now the International Ocean Discovery Program) and the Japanese deep-sea drilling vessel Chikyu. He served as associate editor for Tectonics and the Geological Society of America Bulletin. He was also an editorial board member for Geology, Geofluids, and Progress in Earth and Planetary Sciences. In 1999, he was recognized as an Outstanding Alumnus by the Department of Geological Sciences at the University of California, Santa Barbara, his undergraduate alma mater.
Casey died of complications related to non-Alzheimer’s dementia. He spent his last few weeks in the hands of Westwind Memory Care in Santa Cruz. His passing sent waves of love and sadness around the globe, as former students and colleagues reached out to each other with memories and photos. We authors, who were among his first and last Ph.D. students, appreciated the opportunity to honor Casey’s contributions to science and to the community at the AGU Fall Meeting 2019 with a “Giants of Tectonophysics” presentation, attended by members of his family.
Casey will be greatly missed, but his honesty and generosity, and his deep enthusiasm for geology, for science, and for understanding, will live on through his family, friends, and former students.
—Christie Rowe, Department of Earth and Planetary Sciences, McGill University, Montreal; and Tim Byrne (tim.by[email protected]), Department of Geosciences, University of Connecticut, Storrs