Collisional mountain belts grow as a consequence of continental plate convergence and eventually disappear under the combined effects of gravitational collapse and erosion. Using a decade of GPS data, we show that the western Alps are currently characterized by zero horizontal velocity boundary conditions, offering the opportunity to investigate orogen evolution at the time of cessation of plate convergence. We find no significant horizontal motion within the belt, but GPS and levelling measurements independently show a regional pattern of uplift reaching ~2.5 mm/yr in the northwestern Alps. Unless a low viscosity crustal root under the northwestern Alps locally enhances the vertical response to surface unloading, the summed effects of isostatic responses to erosion and glaciation explain at most 60% of the observed uplift rates. Rock-uplift rates corrected from transient glacial isostatic adjustment contributions likely exceed erosion rates in the northwestern Alps. In the absence of active convergence, the observed surface uplift must result from deep-seated processes.
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机译:碰撞的山地带是大陆板块汇聚的结果,在重力塌陷和侵蚀的共同作用下最终消失。使用十年的GPS数据,我们显示出西部阿尔卑斯山目前的特征是水平速度边界条件为零,这为在板块收敛停止时研究造山带演化提供了机会。我们发现该带内没有明显的水平运动,但是GPS和水平测量独立显示了在西北阿尔卑斯山达到〜2.5 mm / yr的区域抬升模式。除非西北阿尔卑斯山下的低粘度地壳根局部增强了对表面卸载的垂直响应,否则等静压对侵蚀和冰川作用的总效应最多可以解释所观测到的上升速率的60%。从瞬态冰川等静压调整贡献中修正的岩石上升速度可能超过西北阿尔卑斯山的侵蚀速度。在没有主动收敛的情况下,观察到的表面隆起必定是由深部过程造成的。
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