Deformational modeling of the south American plate will test the roles of dominantly non-slab processes acting on the plate. The modeling consists of a finite element analysis of deformation within the plate using grids with 1o-5o node spacing, variable plate rheology, and is the first to explicitly include lateral density contrasts in the south American plate. The study is expected to substantially improve understanding of non-slab forces acting on the South American plate and allow comparisons with the North American plate and will benefit from recent work on the dynamics of the North American plate.