Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.

IntroductionIncreasingly, earth scientists are coming to recognize that deformation and topography are inextricably linked. For example, the large-scale topographic expression of actively deforming regions is strongly controlled by the crustal rheology and the deformation mechanisms that operate at local to regional scales. Conversely, topographic gradients averaged over distances longer than the flexural length scale of the lithosphere also appear to exert a first-order control on crustal deformation because of the large lateral pressure gradients that they induce within the crust.The second point has been illustrated for several actively deforming regions, including the Himalayan-Tibetan region,

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