Influence of spatially variable precipitation on passive margin escarpment evolution
Passive margin escarpments are large-scale geomorphic features which persist over timescales of tens of millions of years. The maintenance of steep topography over these timescales challenges conventional understanding of fluvial erosion. Typical explanations for passive margin escarpments rely on lithospheric flexure and fluvial network geometry. I suggest a role for interactions between climate and landscape evolution motivated by the Western Ghats of India. The Western Ghats experience a wet, tropical climate with topographically-controlled spatially varying precipitation. Precipitation reaches a maximum in the escarpment foothills and decreases sharply with elevation. Using a numerical landscape evolution model, I simulate the effects of coupled climate and topography on an idealized escarpment, including the effects of lithospheric flexure, pre-existing fluvial network geometry, and variability in bedrock resistance. Spatially varying precipitation enhances the slope and lifespan of an escarpment in a similar manner to a resistant bedrock ridge parallel to the escarpment crest. Precipitation variability is a viable mechanism for maintaining a steep escarpment, indicating that the lifetime of such geomorphic features may be a strong function of climate and precipitation mechanisms.
passive margin, passive margin escarpment, Western Ghats Great Escarpment, geomorphology, CASCADE, coupled topography and climate, landscape evolution, numerical model
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign