Parameters controlling dynamically self‐consistent plate tectonics and single‐sided subduction in global models of mantle convection

Abstract

AbstractRecent advances in numerical modeling allow global models of mantle convection to more realistically reproduce the behavior at convergent plate boundaries; in particular, the inclusion of a free surface at the outer boundary has been shown to facilitate self‐consistent development of single‐sided subduction. This allows for a more extensive study of subduction in the context of global mantle convection, as opposed to commonly used regional models. Our first study already indicated important differences between mantle convection with single‐sided subduction and mantle convection with double‐sided subduction. Here we further investigate the effect of various physical parameters and complexities on inducing Earth‐like plate tectonics and its evolution in time. Results reinforce the previous finding that using a free surface instead of a free‐slip outer boundary dramatically changes subduction style, with free surface cases displaying many episodes of single‐sided subduction, which leads to more realistic slab dip, stress state, trench retreat rate, and slab‐induced mantle flow. Longevity of single‐sided subduction is promoted by a layer of hydrated crust with a low yield strength to lubricate the subduction channel, a low‐viscosity asthenosphere, and a high strength of the slab (determined by a combination of high‐diffusion creep viscosity and intermediate friction coefficient), although its effective viscosity is in the observationally constrained range in the bending region. The time evolution displays interesting events including subduction polarity reversals, subduction shut‐off, and slab break‐off.