A temperature dependent viscoplastic flow model of continental lithosphere is used to investigate the evolution of deformation and topography of high elevated plateaus. Such plateaus are products of both continent-continent collision (Tibetan Plateau) and ocean-continent collision (the Altiplano) and develop in the overriding continental plate. In this study we emphasize the mechanically simpler case of oceanic collision, because it does not involve mass transfer between the two plates. The lithosphere is deformed in response to tectonic and buoyancy forces. The tectonic forces arise from subduction of an oceanic plate (or underthrusting of continental lithosphere) that horizontally indents and vertically shears the overriding lithosphere. The buoyancy forces arise in response to horizontal density variations and tend to relax existing topography or thick crust.

The time evolution of the deformation and topography is investigated using a finite element technique that solves for the flow field in the overriding lithosphere. The model produces dynamically supported near-trench topography and inland mountain topography that is isostatically supported by a thick crust. A finite region of localized deformation, thick crust, and high topography develops only if the model includes a horizontal thermal perturbation or an initially thick crust; however, only thermally perturbed lithosphere generates a plateau topography. The shape and size of the calculated plateau depend on the wavelength of the thermal perturbation, Grashof number, and density contrast between the crust and mantle. The time evolution of the deformation shows a significant change in the deformation pattern as the high elevated plateau evolves. During early stages, compressional deformation of the crust and mantle are localized in the thermally perturbed weak zone. At later stages, as the crust thickens, buoyancy forces of larger magnitude resist further thickening of the crust and the locus of compressional crustal deformation migrates inland. This migration does not affect the location of the mantle deformation, which remains in the thermally weak region, but it is accompanied by a significant deformation in the weak lower crust. The separation of the crustal locus from the mantle locus of deformation emphasizes the importance of vertically dependent deformation in the formation of high elevated plateaus. This demonstrates the limitations of models that ignore changes of deformation with depth, such as plane stress or thin sheet models.