Bryan Isacks, a Cornell geophysicist whose landmark research helped establish plate tectonics as a foundation of modern geology, died Sept. 9 in Ithaca. He was 90.
Isacks was the William and Katherine Snee Professor of Geological Sciences Emeritus in Cornell's Duffield College of Engineering. His work connected earthquake patterns, moving slabs of Earth's crust and the process of subduction at a time when plate tectonics was still a contested idea.
Research reshaped modern geology
In 1968, Isacks co-authored “Seismology and the New Global Tectonics” with Cornell professor Jack Oliver and Columbia University scientist Lynn Sykes. The study used seismology to provide evidence for the movement of tectonic plates and helped make subduction central to scientists' understanding of the planet's surface.
Richard Allmendinger, a Cornell professor emeritus of earth and atmospheric sciences, called Isacks an “unassuming genius” whose 1968 paper became one of the most important works of the plate tectonic revolution.
Isacks continued publishing seismology research into the 1980s. His work on the segmentation of the Nazca-South America subduction zone became a model for understanding plate tectonics in the western United States and contributed to the long-running Cornell Andes Project.
He also produced the first digital elevation model of the Andes Mountains and linked its topography to large-scale processes in Earth's lithosphere. Allmendinger said the work helped establish quantitative analysis of topography as a new field.
Isacks later studied Earth through satellite remote sensing. He led a NASA Earth Observing System investigation of climate in high mountain systems and worked on a 1990s proposal for an Earth-orbiting radar satellite that helped inspire the NASA-ISRO Synthetic Aperture Radar satellite launched in 2025, according to Cornell geophysicist Matthew Pritchard.
Cornell career included Finger Lakes research
Born July 25, 1936, in New Orleans, Isacks attended Columbia University as an undergraduate and graduate student before beginning his scientific career there. He joined Cornell's faculty in 1971.
At Cornell, Isacks became director of the Institute for the Study of the Continents and chaired the Department of Geological Sciences from 1994 to 2003. He helped guide the merger that created the Department of Earth and Atmospheric Sciences, linking fields that study different parts of the planet's systems.
His research also reached into the Finger Lakes. Isacks used digital topography to examine the region's landscape and the forces that shaped it, and he advocated for the Museum of the Earth in Ithaca. He helped curate a model glacier exhibit explaining how retreating glaciers formed the Finger Lakes.
Isacks retired in 2008 but remained connected to Cornell colleagues and students. Pritchard said Isacks advised younger faculty on projects involving magma chambers, geothermal resources and Alaskan glaciers.
Isacks was a fellow of the American Geophysical Union and the American Association for the Advancement of Science. The American Geophysical Union awarded him the Walter H. Bucher Medal in 2014, citing his contributions to the understanding of oceanic lithosphere subduction.
He is survived by his wife, Marjorie Olds; children Lillian Isacks, Katherine Isacks, Susan Isacks, Bryan Isacks Jr., Brett Olds and Robert Olds; and several grandchildren.
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