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European Geosciences Union

J. Brian Evans

J. Brian Evans
J. Brian Evans

The 2008 Louis Néel Medal is awarded to J. Brian Evans for his internationally acclaimed path-breaking research on the rheology of rocks, his elegant experiments based on physics and materials science, and his discoveries in the relationship between deformation and fluid transport in a variety of geophysical environments.

Since 1993, J. Brian Evans has been a full professor in the department of Earth, Planetary and Atmospheric Sciences at the Massachusetts Institute of Technology, USA. His Ph.D. dissertation advisers were (the late) Professor Chris Goetze and Professor Bill Brace. These two are among the founders of modern research in the rheology of rocks that is firmly based on the principles of condensed matter physics. After teaching for three years as an Assistant Professor at Princeton University, Brian returned to M.I.T. in 1983 as a faculty member and established what is arguably the best laboratory in the world on the microstructure of deformed rocks under the broadest number of natural variables, e.g., composition, pressure, temperature, presence of fluids, and of chemical and crystallographic second phases. His recognition as a consummate designer of simple yet elegant experiments backed by advanced theories of physics and materials science has resulted in a large number of brilliant young scientists beating their paths to Brian’s laboratory. Some of his younger research colleagues and collaborating faculty are now “stars” in their own rights in Europe and the USA: Yves Bernabé (IPG, Strasbourg), Georg Dresen (Potsdam), Greg Hirth (Brown U.), David Mainprice (Montpellier) and Jörg Renner (Bochum).

Brian’s research has had a major impact on a number of distinct areas of earth sciences: rock deformation, structural geology, geodynamics and even mantle geochemistry and petrology. Brian’s first publication (in 1979) introduced the concept of strength versus depth profiles for the earth and in a later landmark paper (1995), jointly with David Kohlstedt and Steve Mackwell, he helped define the experimental constraints on the strength of the lithosphere as a function of depth. The approach championed in this and other papers by him have moved our understanding of measured rock properties from empirical power-law relationships to a fundamental physics that can help predict changing behavior of rocks with significant changes in strain rates, presence of fluids and second phases, and other variables.

Brian’s sweeping contributions to new understandings in rock physics have a wide range: crack healing and grain boundary migration and their controls on deformation regulation; evolution of porosity and permeability due to pressure solution, brittle-ductile transition and plastic flow; pioneering the use of synthesized two-phase rocks for simulating realistic brittle and plastic properties. But the work that has elicited great excitement among a broad group of petrologists, geochemists and geodynamicists has been his discovery of anomalously fast grain boundary migration induced by chemical variabilities in composition. Such rapid chemical changes in minerals have a critical impact on mantle melt composition and rheology.

In summary, through his research, scholarship and mentoring, Brian has achieved a world-wide reputation as a rock physicist who is an elegant experimentalist, who bases his interpretations on sound physics, applies his discoveries in the relationship between deformation and fluid transport to a variety of geophysical environments and has created an enormous ‘footprint’ through his mentoring and continued advising of brilliant young scientists world-wide.