Lifespan of mountain ranges scaled by feedbacks between landsliding and erosion by rivers

• Published in: Nature (London) 2013-06, Vol.498 (7455), p.475-478
• Main Authors: Egholm, David L., Knudsen, Mads F., Sandiford, Mike
• Format: Article
• Language: English
• Subjects: 639/705/1042; 704/2151/215; Bedrock; Creeks & streams; Erosion rates; Evolution; Experiments; Geomorphology; Grain size; Humanities and Social Sciences; Landslides; letter; Life span; multidisciplinary; Physics; Rivers; Science; Sediment transport; Soil erosion; Stochastic models; Streams; Tectonics
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature12218

Computational simulations show that variations in the rate of fluvial erosion between tectonically active and inactive mountain ranges may relate to a bidirectional coupling between bedrock river incision and landslides. The longevity of mountain ranges Mountain ranges are expected to erode away in the absence of tectonic activity, but several have been preserved over several hundred million years. A new model study shows that the unexpectedly long lifespan of tectonically inactive mountain ranges can be explained in terms of a feedback mechanism that results from coupling between bedrock river incision and the various ways in which landslides can affect fluvial erosion. An important challenge in geomorphology is the reconciliation of the high fluvial incision rates observed in tectonically active mountain ranges with the long-term preservation of significant mountain-range relief in ancient, tectonically inactive orogenic belts 1 , 2 , 3 . River bedrock erosion and sediment transport are widely recognized to be the principal controls on the lifespan of mountain ranges. But the factors controlling the rate of erosion 4 , 5 , 6 , 7 , 8 and the reasons why they seem to vary significantly as a function of tectonic activity remain controversial. Here we use computational simulations to show that the key to understanding variations in the rate of erosion between tectonically active and inactive mountain ranges may relate to a bidirectional coupling between bedrock river incision and landslides. Whereas fluvial incision steepens surrounding hillslopes and increases landslide frequency 9 , landsliding affects fluvial erosion rates in two fundamentally distinct ways. On the one hand, large landslides overwhelm the river transport capacity and cause upstream build up of sediment that protects the river bed from further erosion 9 , 10 , 11 . On the other hand, in delivering abrasive agents to the streams 4 , 5 , 6 , landslides help accelerate fluvial erosion. Our models illustrate how this coupling has fundamentally different implications for rates of fluvial incision in active and inactive mountain ranges. The coupling therefore provides a plausible physical explanation for the preservation of significant mountain-range relief in old orogenic belts, up to several hundred million years after tectonic activity has effectively ceased.