Journal of Geophysical Research: Earth Surface
© American Geophysical Union
Impact Factor: 3.318
ISI Journal Citation Reports © Ranking: 2015: 27/184 (Geosciences Multidisciplinary)
Online ISSN: 2169-9011
Associated Title(s): Journal of Geophysical Research
What drives knickpoints to migrate upstream?
Mountain landscapes are shaped by tectonic uplift, which creates topography, and climate, which determines the rate at which erosion wears down upland areas. Networks of rivers and streams transmit both tectonic and climate signals to landscapes-on a fundamental level, their erosive power is determined by the mountain's steepness, a factor controlled by the rate of tectonic uplift, and the river discharge, a factor set by climate forces such as precipitation rates across an area. Whittaker and Boulton (2012) seek to answer the question of how exactly rivers and streams are affected by climate and tectonics. They focus on 'knickpoints,' which they define as the precise location on a river-long profile that plots channel elevation downstream distance, where the steepness of the stream bed changes most rapidly. Knickpoints migrate upstream depending on the flow of the river, the properties of the rock underlying it, and the degree to which rapid tectonic uplift causes the river to incise to keep pace with the rock uplift rate. But which of these factors dominate? By tracking knickpoints as they migrate upstream through catchments in Turkey and Italy, the authors find that when rock strength and catchment size are equal, channels crossing faults that experience higher rates of tectonic uplift have knickpoints that are retreating faster. Their results indicate that this tectonic control is at least as important as river discharge in driving knickpoint retreat and they suggest this is due to significant channel narrowing in areas of high uplift rates. Consequently, the authors argue that mountain belts affected by rapid rock uplift rates therefore adjust to tectonics and climate faster than those experiencing slower rock uplift rates.