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jonathan tomkin
School of Earth, Society, and Environment, and
Department of Geology, University of Illinois at Urbana-Champaign
September 19, 2007
3:00 pm: Conversation and Cookies in Room 109 ASB
3:30 pm: Seminar in Room 144 Loomis Lab
Climate plays a fundamental role in determining the topographic evolution of actively uplifted mountain ranges. In this talk the influence of glacial erosion on the development of mountain ranges is explored, by comparing the predictions of analytical and numerical models with field observations. A key model prediction is that glacial processes are of first order importance in mountain evolution, being more efficient and more climatically sensitive than fluvial processes. A one-dimensional critical-taper model predicts that the orogen width scales with the rate of accretion to between the 2/3rd and 2nd powers, and with the rate of precipitation to the 1/3rd and 5/4th powers. A full two-dimensional numerical model, that explicitly couples rock uplift produced by convergence with surface erosion, supports these predictions. Taken together, the theoretical model makes a number of predictions about how climate change influences both surface processes such as erosion rates, total yields, and simulates the action of a “glacial buzzsaw”. Tectonic changes are also predicted, and the simulations support the idea that a climate cooling of the magnitude recorded in the Late Cenozoic has the potential to more than double the rate of rock uplift in appropriate orogens. These predictions are compared with preliminary field evidence from the Patagonian Andes, which show that rock uplift rates have increased coincidently with the onset of Late Cenozoic glaciation. |
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