9725629 Gurnis The PI will develop a new generation of dynamic models with the finite element method and test such models against observations at both intermediate (10-100 km) and large scales (100 -10,000 km). The principle objectives are to place bounds on (1) the effective viscosity of converging plate boundaries, (2) the lateral strength of slabs, (3) radial variations in mantle viscosity, and (4) the mass flux of slabs into the lower mantle. Bounds on the effective viscosity of converging margins are essential ingredients in generating plate tectonics from theoretical models of mantle convection. Constraining mass flux into the lower mantle is a fundamental constraint on geochemical and thermal models of the mantle. The main components of the proposed work will be (1) synthesis of a suite of geophysical observations, (2) formulation of regional flow models with actual slab and fault geometries, (3) comprehensive investigation of the dynamics of these 3-D models, and (4) testing with data independent of that used to construct slab geometry and buoyancy. ***
