Self-Consistent Generation of Tectonic Plates in Time- Dependent, Three-Dimensional Mantle Convection Simulations. Part 1: Pseudo-Plastic Yielding

Presented here are the first three-dimensional simulations of mantle convection to display self-consistently-generated plate tectonic-like behavior which 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. 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 structurethe longest wavelength possible in the domain. Twodimensional models display much greater time-dependence than threedimensional models.