V. Stamenkovic, T. Höink, and A. Lenardic

Abstract We use 1-D thermal history models and 3-D numerical experiments to study the impact
of dynamic thermal disequilibrium and large temporal variations of normal and shear stresses on the
initiation of plate tectonics. Previous models that explored plate tectonics initiation from a steady state,
single plate mode of convection concluded that normal stresses govern the initiation of plate tectonics,
which based on our 1-D model leads to plate yielding being more likely with increasing interior heat
and planet mass for a depth-dependent Byerlee yield stress. Using 3-D spherical shell mantle convection
models in an episodic regime allows us to explore larger temporal stress variations than can be addressed
by considering plate failure from a steady state stagnant lid configuration. The episodic models show that
an increase in convective mantle shear stress at the lithospheric base initiates plate failure, which leads
with our 1-D model to plate yielding being less likely with increasing interior heat and planet mass. In this
out-of-equilibrium and strongly time-dependent stress scenario, the onset of lithospheric overturn events
cannot be explained by boundary layer thickening and normal stresses alone. Our results indicate that in
order to understand the initiation of plate tectonics, one should consider the temporal variation of stresses
and dynamic disequilibrium.

Stamenkovic, V., T. Höink, and A. Lenardic (2016), The importance of temporal stress variation and dynamic disequilibrium for the initiation of plate tectonics, J. Geophys. Res. Planets, 121, doi:10.1002/2016JE004994.