IGPP is pleased to invite you to join its Spring 2023 Seminar Series presentation featuring University of Texas Institute for Geophysics' Thorsten Becker. Dr. Thorsten's talk, "On Convective Memory" will occur May 9, 2023 in the Munk conference room.
Time: 12:00 pm, Pacific Time
Location: Munk conference room
Abstract: Plate tectonics is the surface expression of mantle convection, but many aspects of our present-day tectonic setting depend on how the solid Earth system has evolved over time. I touch on work across a range of spatio-temporal scales addressing how convective memory can be used to validate tectonic scenarios to better understand plate boundary evolution. Seismic anisotropy in the upper mantle is one recorder of convective deformation, and the duration over which textures are reworked controls the lifespan of memory. This means that the lithosphere may allow distinguishing between different plate tectonic scenarios over the last ~50 Ma. Uncertainties about those scenarios and slab rheology imply that our understanding of subduction mass transport remains incomplete, leading to ambiguities about the deep mantle record of subduction. One particular issue is how slabs are deformed upon bending in the trench. I discuss results from convection models with rheological memory which affects subduction dynamics and plume-slab interactions. Within global, plate generating convection models, reactivation of damage zones increases the frequency of plate reorganizations and hence reduces the dominant periods of surface heat loss fluctuations. Inheritance of lithospheric damage dominates surface tectonics over any local boundary stabilizing effects of rheological weakening. Progressive generation of weak zones may counteract any effects of reduced convective vigor throughout planetary cooling, with implications for the frequency of orogeny throughout Wilson cycles. I close by a consideration of the effects of local rheological damage weakening vs. the longest recorder of geological history of all, the continental lithosphere.