Critical factors for plate tectonics on rocky planets

Convective mantle flow of terrestrial planets is governed by a temperature- and pressure-dependent rheology. This results in a stagnant-lid regime observed on most terrestrial planets. Plastic deformation can lead to breaking of the strong upper lithosphere, which resembles plate tectonics on Earth.

Most efforts to model mantle convection with self-consistent plate tectonics combine Newtonian power-law with a stress-dependent pseudo-plastic rheology.
In the uppermost mantle, where stresses are high, deformation is thought to be driven partly by dislocation creep. This is often neglected in viscoplastic consideration, which employ purely diffusion-creep-driven flow combined with a yield criterion.

In our models we employ an effective viscosity law combining both Newtonian and Non-Newtonian power laws with a pseudo-plastic model. We study the influence of rheology in combination with grain size and different yield stress parameterizations on the likelihood of the on-set of plate tectonics in a 2D-spherical annulus geometry. We compute common diagnostic values related to the characterization of a mobilized surface. With this model we aim at identifying key planetary factors for the occurrence or absence of plate tectonics.