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| Titel |
The Influence of Climate and Micro-climate (aspect) on Soil Creep
Efficiency: cinder cone morphology and evolution along the eastern
Mediterranean Golan Heights |
| VerfasserIn |
Matan Ben-Asher, Itai Haviv, Joshua J. Roering, Onn Crouvi |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250147763
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| Publikation (Nr.) |
 EGU/EGU2017-11969.pdf |
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| Zusammenfassung |
| Although hillslope evolution has occupied geoscientists for over a century, the effect of
climate on the morphology of soil-mantled hillslopes remained poorly-constrained. In
this study we utilize numerical simulations of volcanic cinder cones in the Golan
Heights (Eastern Mediterranean) to estimate soil creep efficiency across a strong
north-to-south gradient in mean annual precipitation (1100-500 mm). Our model utilizes the
initial cinder cone profile (constrained by the dip of the ash layers), the current
hillslope profile (measured with cm scale accuracy) and the known eruption age
(40Ar-39Ar constraints) to predict the best-fit value of the soil creep diffusion coefficient
(‘diffusivity’).
Our results indicate that the best-fit diffusivity coefficient varies from 0.5 to 6 m2/ka
among the seven cinder cones we have analyzed. Soil diffusivity varies with both climate
(precipitation) and aspect-related microclimate: diffusivity values are higher on south facing
hillslopes, and decrease with mean annual precipitation. This climate dependency likely
reflects an increase in the apparent soil cohesion (or resistance to disturbance-driven
transport) at higher precipitation rates due to higher density of vegetation coverage (root
network) which co-varies with rainfall and aspect. We demonstrate this significant
co-variance utilizing the spatial distribution of NDVI vegetation index calculated from
ASTER images and show that aspect-related hillslope asymmetry becomes established
over time on cinder cones as well as in other landforms. In addition, our results
show that 750-850 ka cinder cones display lower diffusivity values relative to late
Pleistocene cinder cones (120-150 ka). This temporal variance in diffusivity may reflect
either rapid transport associated with climatic conditions of the last glacial and
inter-glacial period or time-dependent material properties that influence transport
efficiency.
Analysis of previously studied cinder cones in the US extends our framework to arid
climatic domains and suggests a humped relationship between soil diffusivity and mean
annual precipitation with maximum diffusivity at annual precipitation of 400-600 mm. |
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