Self-consistent generation of tectonic plates in time-dependent, three-dimensional mantle convection simulations

Abstract

Presented here are self-consistent, three-dimensional simulations of mantle convection, some of which display an approximation of plate tectonic behavior that is continuous in space and time. Plate behavior arises through a reasonable material description of silicate deformation, with a simple yield stress being sufficient to give first-order plate-like behavior; however, the required yield strength or fault frictional coefficient is much less than experimentally determined values. Toroidal:poloidal ratios are within geologically observed limits. The sensitivity of the system to yield strength and the form of strength envelope is systematically investigated. Optimum plate character is obtained in a narrow range of yield strength, below which diffuse boundaries, and above which episodic behavior, and eventually a rigid lid, are observed. Models with mobile lids develop very long wavelength horizontal structure, the longest wavelength possible in the domain. Two-dimensional models display much greater time dependence than three-dimensional models.