[S-IT30] Tectonic collision systems in continents and oceans

[SIT30-02] Mountain height at convergent plate boundaries is controlled by the megathrust shear force

★Invited Papers

*Armin Dielforder¹, Ralf Hetzel², Onno Oncken¹ (1.Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Germany, 2.Institute of Geology and Paleontology, University of Muenster, Germany)

Keywords:Megathrust, mountain building, erosion

Force balance considerations suggest that the height of mountain ranges at convergent plate boundaries depends on the shear force acting along the plate boundary megathrust. Whether this dependency indeed controls mountain height is, however, currently unknown and highly debated. In particular, climate-dependent erosional processes, such as glacial and fluvial erosion, are often assumed to exert a first-order control on mountain height, although this assumption has remained difficult to validate. To test whether mountain height is controlled by the megathrust shear force or by erosion, we constrained the shear force along active megathrusts from their rheological properties. We then determined the theoretical elevation supported by the megathrust shear force using a force balance model and compared it to the actual height of mountain ranges. Our results indicate that mountain height around the globe closely matches the force-controlled elevation, irrespective of climatic conditions and erosion rates. This finding indicates that mountain height is primarily governed by the megathrust shear force and that the upper plate is close to force equilibrium. We therefore propose that temporal variations in mountain height reflect long-term changes in the force balance, but are not indicative for a direct climate control on mountain elevation.