Global plate tectonics and mantle convection with damage memory

University Of Texas At Austin, Austin TX

Investigators

Abstract

Plate tectonics is fundamental for Earth's evolution and the surface expression of mantle convection. However, it is unclear how the narrow and strongly deforming boundaries between the more rigid plates form. The reactivation of plate boundaries, in particular, gives the continental plates a long-term hysteresis with profound implications for tectonics. This project seeks to better understand the causes and consequences of damage memory in convection. Funding will support a female graduate student and speak to issues outside geodynamics including the quest for a general law describing fault behavior from the seismic cycle to long-term Earth evolution. The project will also support new international collaborations, and research outcomes will be disseminated widely, including for UT Austin's GeoFORCE K-12 outreach program. This project will implement strain-dependent weakening into global, numerical convection models in order to explore the style of "plate tectonics" that is generated by visco-plastic mantle flow. Incorporating such rheological memory will allow study of the full range of tectonic behavior, including how plate boundary evolution and plate motions are linked with the deep mantle. A range of viscous damage formulations will be explored and benchmarked against grain-size evolution theories and other suggested mechanisms for strain-localization, such as formation of shear bands and mechanical anisotropy due to lattice preferred orientation of olivine. Model results will be compared with geological constraints including plate kinematics, with particular focus on the time-dependence of plate boundary geometry, plate speeds and sizes, and seafloor age distributions. The overall goal is to develop a theoretical understanding of the role of tectonic inheritance in terrestrial planet evolution and heat transport. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.