Impact of asymmetric uplift on mountain asymmetry: Analytical solution, numerical modeling, and natural examples

Mountain asymmetry is defined by the ratio of the lengths of two river systems across a drainage divide and is determined by the normalized location of the drainage divide. Understanding how asymmetric uplift influences the drainage divide, and therefore mountain asymmetry, is one of the preconditions for extracting tectonic information from topography. However, there is no consensus on this fundamental problem. Here we combined analytical solutions and numerical landscape evolution modeling to examine the impact of two key parameters (uplift gradient, and ratio of uplift rates at two edges) on mountain asymmetry. We followed the convention by assuming uniform gradient of uplift rate and erosion coefficient across the drainage divide. Our analytical approach and numerical simulations show that mountain asymmetry is not always controlled by the uplift gradient as previously suggested; instead, it is governed by the ratio of uplift rates at two edges across the divide. We quantified the relationship between the normalized divide location and the ratio of uplift rates. We applied the new formula to two natural examples to reconstruct the tectonics from the locations of the drainage divides. Moreover, we compared the influences of vertical and horizontal movements on the mountain asymmetry in different situations. The result suggests that in mountain belt with weak tectonic activity or high erosion coefficient, the mountain asymmetry is mainly controlled by the ratio of uplift rates. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Mountain asymmetry is controlled by the location of the drainage divide and the ratio of uplift rates at two edges, rather than the uplift gradient as previously suggested. Research indicates that in mountain belts with weak tectonic activity or high erosion coefficient, the mountain asymmetry is mainly influenced by the ratio of uplift rates.