The influence of large-scale mantle flow on the dynamics of the East African Rift

Because the Nubia/Somalia plate system is almost entirely surrounded by spreading ridges in the Atlantic and Indian Oceans, Earth's mantle buoyancies are thought to play a key role in the dynamics of East Africa rifting. While this notion is supported by images of large-scale mantle structures beneath Africa from seismic tomography, the details of the force balance driving continental rifting are still debated. In particular, the contribution of gravitational potential energy (GPE) associated with continental topography in driving ~E-W extension across the East African Rift remains elusive. The Nubia/Somalia divergent boundary therefore presents a unique opportunity to quantify in detail plate-driving forces associated with 1) mantle buoyancies acting at the base of the African lithosphere and 2) lateral GPE gradients within the lithosphere. In this study we employ numerical models of the mantle/lithosphere system to test explicitly the contribution of mantle convection to the dynamics of rifting in East Africa. Preliminary results suggest that such contribution may be smaller than previously thought, and that forces arising from GPE gradients may control surface deformation in East Africa.