Three-dimensional mantle dynamics with an endothermic phase transition

Abstract

3D convection for the spinel to perovskite phase change has been simulated numerically. Results for Rayleigh (Ra) numbers of 0(10 exp 6) show intermittent layering with a strong robust plume rising through the phase boundary. Many descending instabilities are deflected but merging cold sheets come together at a junction. A pool of cold material accumulates underneath in the phase-transition zone. A strong gravitational instability results, which precipitates a rapid and massive discharge of upper-mantle material.