Abstract

Landscapes developed in layered sedimentary or igneous rocks are common on Earth, as well ason other planets. Features such as hogbacks, exposed dikes, escarpments, and mesas exhibit resistant rocklayers adjoining more erodible rock in tilted, vertical, or horizontal orientations. Hillslopes developed in theerodible rock are typically characterized by steep, linear-to-concave slopes or “ramps” mantled with materialderived from the resistant layers, often in the form of large blocks. Previous work on hogbacks has shown thatfeedbacks between weathering and transport of the blocks and underlying soft rock can create relief overtime and lead to the development of concave-up slope profiles in the absence of rilling processes. Here weemploy an analytic approach, informed by numerical modeling and field data, to describe the quasi-steadystate behavior of such rocky hillslopes for the full spectrum of resistant layer dip angles. We begin with asimple geometric analysis that relates structural dip to erosion rates. We then explore the mechanisms bywhich our numerical model of hogback evolution self-organizes to meet these geometric expectations,including adjustment of soil depth, erosion rates, and block velocities along the ramp. Analytical solutionsrelate easily measurable field quantities such as ramp length, slope, block size, and resistant layer dip angle tolocal incision rate, block velocity, and block weathering rate. These equations provide a framework forexploring the evolution of layered landscapes and pinpoint the processes for which we require a morethorough understanding to predict their evolution over time.

Citation

Glade, R and Anderson, RS (2018): Quasi-steady evolution of hillslopes in layered landscapes: An analytic approach . JGR Earth Surface 123, 26-45. DOI: 10.1002/2017JF004466