Colloquium: Laurent Montesi

Dr. Laurent Montesi, Associate Professor, Dept. of Geology, University of Maryland

Abstract:  Why does the Earth have plate tectonics? Our planet is unique in the solar system in that its tectonic activity is focused on an interconnected network of relatively narrow deformation zones (plate boundaries). Mechanically, this can only happens if deforming boundaries are somehow weaker than inactive regions. I will discuss the potential origins of that weakness at different level of the lithosphere. Localization in the ductile regime depends crucially on microstructural evolution, through a combination of grain size reduction and foliation development. I will also discuss the consequences of these weakening processes for large-scale tectonics, from postseismic deformation in the western US and the difference in the degree of localization in oceanic and continental environments.