Plumes anchored by a high viscosity lower mantle in a 3D mantle convection model featuring dynamically evolving plates

Abstract

Previous studies have shown that 3D vigorously convecting systems featuring plate‐like surface motion and lower mantle viscosities much greater than the upper mantle viscosity can yield long lived intraplate plumes if plate boundaries remain fixed. We investigate whether plumes originating in a lower mantle 90 times more viscous than the upper mantle will maintain relatively fixed positions when dynamic plate evolution is present. We compare the findings from a pair of calculations featuring four plates in a 3 × 3 × 1 periodic Cartesian geometry model. In both calculations, plate velocities are determined dynamically in response to the stresses acting on the viscously defined lithosphere. In one case plate boundaries are held fixed, in the second dynamically determined plate evolution is enabled. In both cases, long lived mantle plumes are observed. Moreover, the locations of the plumes remain relatively fixed even as plates systematically evolve to a completely different arrangement from their initial configuration.