Evolution of midplate hotspot swells: Numerical solutions

Abstract

The evolution of midplate hotspot swells on an oceanic plate moving over a hot, upwelling mantle plume is amenable to numerical simulation. In our model, the plume supplies to the lithosphere a Gaussian‐shaped thermal perturbation and dynamic support dominated by thermal buoyancy. We consider the two fundamental mechanisms of transferring heat, conduction and convection, during the interaction of the lithosphere with the mantle plume. The transient heat transfer equations, with boundary conditions varying in both time and space, are solved in cylindrical coordinates using the alternating direction implicit finite difference method on a 100×100 grid. The topography, geoid anomaly, and heat flow anomaly of the Hawaiian swell and the Bermuda rise are used to constrain the models. Our results confirm the conclusion from previous work that the Hawaiian swell can not be explained by conductive heating alone, even if an extremely high thermal perturbation is allowed. On the other hand, the model of convective thinning predicts successfully the topography, geoid anomaly, and the heat flow anomaly around the Hawaiian islands, as well as the changes in the topography and anomalous heat flow along the Hawaiian volcanic chain. The model constrains the Hawaiian plume to have a half wavelength of about 500 km, a center heat flux 5–6 times the background value, and a convective current velocity 3–10 times that of the background convective current. Comparatively, the mantle plume for the Bermuda rise is much weaker. Conductive heating is probably the dominant mechanism for the evolution of the Bermuda rise.