نتایج جستجو برای: fluvial erosion
تعداد نتایج: 34245 فیلتر نتایج به سال:
High rates of erosion (1-15 mm/yr) of fluvial strata have persisted over intervals of 0.2-1.5 m.y. and across areas of 60-2000 km 2 in the Cenozoic foreland basin of northern Pakistan. These rates occur in areas associated with thrust shortening, and they indicate that erosion nearly kept pace with the rates of latest Miocene to Pleistocene uplift. Such high rates of erosion are predicted to pr...
[1] To explain the much higher denudation rates and valley network development on early Mars (> 3.6 Gyr ago), most investigators have invoked either steady state warm/wet (Earthlike) or cold/dry (modern Mars) end-member paleoclimates. Here we discuss evidence that highland gradation was prolonged, but generally slow and possibly ephemeral during the Noachian Period, and that the immature valley...
It has been proposed that plant biodiversity may increase the erosion resistance of soils, yet direct evidence for any such relationship is lacking. We conducted a mesocosm experiment with eight species of riparian herbaceous plants, and found evidence that plant biodiversity significantly reduced fluvial erosion rates, with the eight-species polyculture decreasing erosion by 23% relative to mo...
Future global warming has a number of implications for fluvial geomorphology because of changes in such phenomena as rates of evapotranspiration, precipitation characteristics, plant distributions, plant stomatal closure, sea levels, glacier and permafrost melting, and human responses. Potential changes in rivers are outlined in this review in the context of changes in the intensity of rainfall...
Large-scale topographic analyses show that hemisphere-scale climate variations are a first-order control on the morphology of the Andes. Zonal atmospheric circulation in the Southern Hemisphere creates strong latitudinal precipitation gradients that, when incorporated in a generalized index of erosion intensity, predict strong gradients in erosion rates both along and across the Andes. Cross-ra...
This first overview of large-scale rock slope failure (RSF) in the Pyrenees addresses the eastern third of the range. Around 30 principal RSFs >0.25 km and 20 lesser or uncertain cases have been identified from remote imagery and groundtruthing. Compared with other European mountain ranges, RSF incidence is relatively sparse, displays no obvious regional trend or spatial clustering, and occurs ...
Milna Crater, Mars (23.4S, 12.3W) exhibits signs of fluvial modification early in Mars history, including a large multi-lobed fan deposit cut by several sinuous valleys. We describe the past hydrologic conditions in Milna and the surrounding area, including a potential lake with a volume of 50 km 3. We also introduce new methods (i) to calculate the timescale of sediment deposition by consideri...
Landscape topography is the expression of the dynamic equilibrium between external forcings (for example, climate and tectonics) and the underlying lithology. The magnitude and spatial arrangement of erosional and depositional fluxes dictate the evolution of landforms during both statistical steady state (SS) and transient state (TS) of major landscape reorganization. For SS landscapes, the com...
Many numerical landform evolution models assume that soil erosion by flowing water is either purely detachment‐ limited (i.e. erosion rate is related to the shear stress, power, or velocity of the flow) or purely transport‐limited (i.e. erosion/ deposition rate is related to the divergence of shear stress, power, or velocity). This paper reviews available data on the relative importance of deta...
The relative rates of erosion by rivers and glaciers, and the topographic effects of these two different styles of erosion, remain outstanding problems in geomorphology. We use a quantitative description of local fluvial landscapes to estimate how glaciated landscapes might look now had glaciers not developed. This indicates the landscape modification attributable to glacial erosion. We present...
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