NON-LINEAR CONTROLS ON EROSION RATES IN TECTONICALLY ACTIVE MOUNTAIN RANGES

The functional relationship between erosion rate and topography is central to understanding both controls on global sediment flux and the potential for feedback between tectonics, climate, and erosion in shaping topography. Analysis of a fine-resolution (10 m grid) DEM transect across the convergent orogen of the Olympic Mountains reveals a non-linear relation between long-term erosion rates, mean slope, and local relief, consistent with a model for hillslope evolution by landsliding in steep terrain. Coarser-scale global analysis of the relation between erosion rate and local relief reveals a linear trend for areas with low erosion rates and a strongly non-linear relation where erosion rates are highest, such as tectonically active mountain ranges. Together these analyses support the emerging view that erosion rates adjust to high rates of tectonically driven rock uplift primarily through changes in the frequency of landsliding rather than hillslope steepness, and imply that climate-induced changes in rates of valley incision play a minor role in controlling landscape-scale erosion rates.