Plate Motions and Stresses from Global Dynamic Models

Abstract

Driving Forces The physical properties that control the motions of Earth's tectonic plates are difficult to predict accurately on a global scale. Large-scale geodynamic models are continually becoming more powerful, but controversies remain regarding plate-driving forces. Ghosh and Holt (p. 838 ) present a global geodynamic model that achieves a high level of accuracy in fitting surface plate motions, plate boundary deformation, and intraplate stress fields. The model identifies regions where mantle drag drives plate motion and regions where the drag resists plate motion. Based on the relative magnitude of mantle drag forces and lithospheric buoyancies contributing to the stress field, the model also quantifies absolute viscosity—a parameter that has been notoriously difficult to predict for Earth's interior.