The relative efficacy of fluvial and glacial erosion over modern to orogenic timescales

Since the late nineteenth century, it has been debated whether rivers or glaciers are more effective agents of erosion(1). The dramatic landscapes associated with glaciated terrain have often led to the argument that glaciers are more erosive than rivers, and recent studies have documented the topographic signature of an ice-controlled limit of mountain height known as the 'glacial buzz-saw'(2,3). Here we present a new global compilation of erosion rates, which questions the conventional view of glaciers and erosion. In regions of rapid tectonic uplift, erosion rates from rivers and glaciers both range from 1 to over 10 mm yr(-1), indicating that both are capable of generating erosion rates matching or exceeding the highest rates of rock uplift. Moreover, a comparison of erosion rates over timescales ranging from 10(1) to 10(7) years indicates that glacial erosion tends to decrease by one to two orders of magnitude over glacial cycles, whereas fluvial erosion rates show no apparent dependence on time. We conclude that tectonics controls rates of both fluvial and glacial erosion over millennial and longer timescales and that the highest rates of erosion (>10 mm yr(-1)) generally result from a transient response to disturbance by volcanic eruptions, climate change and modern agriculture.