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 erosion1. 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 101 to 107 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. Quantitative support for the perception that glaciers are more effective erosional agents than rivers is primarily based on topographic analyses, numerical modelling, and two key studies4,5 that compiled sediment yields measured from glaciated and nonglaciated basins. Both studies reported that, for basins of similar size, glaciers can erode at 1–10 times the rate of rivers. Moreover, modern basin-wide glacial erosion rates of over 10mmyr−1 have been measured from orogens, such as the coastal ranges of Alaska, where maximum tectonic uplift rates rarely exceed 1–4mmyr−1 (ref. 6, 7), reinforcing the idea that glacier erosion inhibits crustal material from rising above the elevation of the snowline, effectively providing an ice-controlled limit tomountain building. In the decade since the last comprehensive reviews were published4,5, advances in both geochronology and numerical modelling, driven by a renewed interest in landform development and the relationship between climate and tectonics, have led to new studies documenting both fluvial and glacial erosion rates in a variety of tectonic settings and over several timescales. A few of these studies suggest that in regions of rapid tectonic uplift, such as in the Nepalese Himalaya8,9 and Taiwan thrust belt10, river incision rates of over 10mmyr−1 have been measured, comparable to the highest erosion rates in glaciated regions and two orders ofmagnitudemore rapid than in less tectonically active orogens, such as southeastern Australia11,12 or the Oregon Coast Range13,14. From these new data, we have compiled an expanded global dataset of sediment yield and denudation rates from glaciated and non-glaciated catchments. By taking advantage of the wide array of geochronometric tools now in use to examine variability in glacial and fluvial erosion over a