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

TLDR

The simulations use a simple yield‑stress model of silicate deformation, showing that plate‑like behavior emerges with a yield strength far below experimental values, and the authors systematically examine how yield strength and the strength envelope shape influence the system. The self‑consistent 3‑D mantle convection simulations produce plate‑tectonic‑like behavior that is continuous in space and time, with toroidal‑to‑poloidal ratios within geologic limits, optimal plate character in a narrow yield‑strength window, mobile‑lid models generating the longest horizontal wavelengths, and 2‑D models exhibiting greater time dependence than 3‑D.

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.