Quantifying the climatic and tectonic controls on hillslope steepness and erosion rate

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Abstract

Hillslopes in humid regions are typically convex to concave in profile and have a relatively thick, continuous regolith cover. Conversely, hillslopes in arid regions are typically cliff-dominated and have a relatively thin, discontinuous regolith cover. The difference between these two end-member slope forms is classically attributed to climate, but climate, tectonics, and lithology all play a role. In this paper, we describe a mathematical model for hillslope gradient and regolith thickness using basic climatic and tectonic input data for a given rock type. The model first solves for the regolith thickness on a planar slope segment in topographic steady state using the soil production function and a prescribed uplift/incision rate. The climatic and lithologic controls on soil production rates are quantified using an empirical energy-based model for the physical weathering of bedrock. The slope gradient is then computed by balancing uplift/incision rates with sediment fluxes calculated using a nonlinear depth- and slope-dependent sediment transport model. The model quantifies the ways in which, as aridity and uplift/incision rates increase, regolith thicknesses decrease and hillslope gradients increase nonlinearly until a threshold condition is reached, beyond which bare, cliff-dominated slopes form. The model can also be used to estimate long-term erosion rates and soil residence times using basic input data for climate and regolith thickness. Model predictions for erosion rates closely match cosmogenically derived erosion rates in granitic landscapes. This approach provides a better quantitative understanding of the climatic and tectonic controls on slope form, and it provides a simple, widely applicable method for estimating long-term erosion rates and the thickness of regolith cover on hillslopes.

Original languageEnglish (US)
Pages (from-to)73-80
Number of pages8
JournalLithosphere
Volume1
Issue number2
DOIs
StatePublished - Apr 2009

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regolith
erosion rate
hillslope
tectonics
uplift
cliff
climate
soil
aridity
arid region
sediment transport
residence time
bedrock
lithology
weathering
rate
prediction
rock
sediment
energy

ASJC Scopus subject areas

  • Geology

Cite this

Quantifying the climatic and tectonic controls on hillslope steepness and erosion rate. / Pelletier, Jon; Rasmussen, Craig.

In: Lithosphere, Vol. 1, No. 2, 04.2009, p. 73-80.

Research output: Contribution to journalArticle

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