Millennial-scale record of landslides in the Andes consistent with earthquake trigger

Geologic records of landslide activity o er rare glimpses into landscapes evolving under the influence of tectonics and climate. Because the deposits of individual landslides are unlikely to be preserved, landslide activity in the geologic past is often reconstructed by extrapolating from historic landslide inventories. Landslide deposits have been interpreted as palaeoclimate proxies relating to changes in precipitation, although earthquakes can also trigger landslides. Here we measure cosmogenic 10Be concentrations in individual cobbles from the modern Quebrada Veladera river channel and an adjacent terrace in Peru and calculate erosion rates. We find, in conjunction with a 10Be production model, that the 10Be concentrations of each cobble population record erosion integrated over thousands of years and are consistent with a landslide origin for the cobbles. The distribution of 10Be concentrations in terrace cobbles produced during the relatively wet climate before about 16,000 years ago is indistinguishable from the distribution in river channel cobbles produced during the drier climate of the past few thousand years. This suggests that the amount of erosion from landslides has not changed in response to climatic changes. Instead, our integrated, millennial-scale record of landslides implies that earthquakes may be the primary landslide trigger in the arid foothills of Peru.