ausblenden:
Schlagwörter:
-
DDC:
550 - Earth sciences
Zusammenfassung:
Denudation links tectonics with climate by changing topographic loads and promoting the drawdown of CO2. Measurements of denudation are a key to understanding this link. In particular, they are required to test and calibrate geodynamic models, to evaluate the tectonic control on landscape evolution, to quantify the geomorphic impact of faulting and seismicity, and to assess the role of tectonically driven denudation in stabilizing Earth’s climate. We review techniques used to measure denudation, and weathering on timescales relevant to faulting and the dynamics of fault zones, with particular attention paid to the use of hydrometric data and cosmogenic isotopes. Using selected examples, we illustrate the application of these techniques to problems ranging from soil formation and coseismic erosion of earthquake epicentral areas to the erosion of orogens and estimation of catchment-scale erosion and weathering fluxes. The examples show that faulting is the Earth’s premier erosion and weathering engine. Globally, erosion scales with tectonic forcing. Locally, fluvial incision and landscape lowering are correlated with faulting and seismic activity. Thus, tectonically active areas yield disproportionate amounts of sediment. Erosion refreshes rock surfaces in these areas, thereby enhancing chemical weathering rates and CO2 consumption. The effects of climate variability and change are evident in the patterns and rates of erosion and weathering. However, they are almost always superimposed on a stronger tectonic signal. We highlight the potential of cosmogenic nuclides to quantify present and past rates and patterns of denudation associated with faulting. Finally, we identify outstanding challenges for future work: (a) to characterize crustal deformation, climate, and denudation over their full range of time and length scales; (b) to analyze the geomorphic impact and stratigraphic record of recent earthquakes; (c) to identify the processes, thresholds, and feedback mechanisms that control global weathering and regulate the long-term climate; and (d) to provide constraints that help to mitigate the risks associated with geomorphic processes triggered by earthquakes. Constraining the denudational response to faulting will help to meet these challenges.
