Significance of the gravitational relaxation on a plume-driven surface uplift: Dynamic calculations using the Boundary Element Method

Surface topographic deformations produced by mantle movements are typically estimated using a numerical mantle convection model with the thin-sheet approximation, where the topographic load is assumed to be always balanced with the calculated normal stress at the top of the fixed boundary of the convecting cell. Although this approximation is commonly used due to its relative simplicity, it implicitly neglects the effect of gravitational relaxation over the dynamically uplifted topography. In order to estimate the potential errors of this approximation, we have developed a new Boundary Element model that permits precise calculations of viscous flow movements with flexible boundaries in the gravity field. Our applications of this model to the estimations of topographic uplifts over mantle upwelling zones show that the thin-sheet approximation results in exaggerated topographic values. Thus, we conclude that, by considering the effect of gravitational relaxation, it is possible to significantly increase the accuracy in estimating the effect that mantle convection has on the surface topography.