On Friday, 16th September, Surface Processes & Palaeoclimate team organizes a joint seminar with the “Earth Surface Processes Modelling” group from GFZ Potsdam (GFZ German Research Centre for Geosciences).
Where: GFÚ Lecture Hall
For details, please contact: Greg Ruetenik (ruetenik@ig.cas.cz)
14:30 – 15:00 Prokop Závada (Dynamics of Orogens & Rock Deformation, GFÚ): The impact of melt on the rheology of lower crustal rocks and style of exhumation of subducted continental crust during Variscan collision (with a look at their state-of-the-art analog modeling experiments)
15:15 – 16:00 Jean Braun: What controls the height of mountain belts? (abstract bellow)
Jean Braun, GFZ Potsdam
Sebastian Wolf and Ritske Huismans, University of Bergen
Xiaoping Yuan, China University of Geosciences, Wuhan
This question has been at the core of much debate since strong links and feedbacks between tectonics, erosion and climate have been postulated in the early 1990’s. Based on the results of large, state-of-the-art and coupled numerical models of tectonic deformation and erosional processes, I will demonstrate that the controls are a combination of three factors that can be factored into a new dimensionless number, the Beaumont number (Bm). These are: convergence velocity, erosional efficiency (and hence climate) and crustal strength. I will also show that mountains belts are of three types, depending on their value of Bm: the height of small Bm (or Type 3) mountain belts is controlled by erosion (and thus climate), whereas large Bm (or Type 1) mountain belts have reached their crustal strength-controlled maximum height. The two types differ also by their widening rate: Type 1 mountains accommodate shortening by widening, while Type 3 mountains have reached topographic and flux steady-state and maintain a constant width. There exists an intermediary type of mountain belts (Type 2, with Bm~0.5) that have reached their strength-controlled height but do not widen. We show that the Bm value and thus the type of all mountain belts can be derived from simple observations, such as convergence velocity, mountain height and widening rate. This, in turn, can be used to determine the relative contribution of each of the three controlling factors for each mountain belt, thus finally answering the question of what controls mountain height on Earth. Finally, we show how the three types of mountain belts behave after shortening stops and demonstrate that erosional efficiency is the dominant parameter that controls old mountain belt longevity.