Investigation of Mechanisms of Super-Continent Fracture using Spherical-Axisymmetric Models of Thermal Convection in the Earth's Mantle

The question of the mechanism that is responsible for super-continent break-up has been a long-standing one. Active mantle plume upwellings, down-going oceanic plates at continental margins, and passive upwellings due to continental insulation of the mantle have all been proposed as mechanisms capable of creating sufficient extensional stresses within super-continents to result in fracture and dispersal. Much work has subsequently been done using numerical models of the mantle convection process and many of the above-mentioned mechanisms have been demonstrated for different Earth-like convective regimes. For the most part, all previous studies have been performed in Cartesian geometry and in the absence of many effects such as compressibility, phase-transitions, and depth-dependent properties. In this contribution we investigate these effects in a spherical-axisymmetric model of thermal convection in the Earth's mantle in which the effects of surface plates are also included. We demonstrate that the extensional stresses needed to fracture super-continents are significantly reduced in spherical geometry and that the active plume mechanism of super-continent fracture may be less viable when effects due to compressibility are included.