Work, persistence, and formative events: The geomorphic impact of landslides

Understanding the scale and frequency of physical processes that act upon and form the surface of the Earth is a fundamental goal of earth science. Here we determine the magnitudes of landslides that impact the landscape in terms of work, persistence, and formative events. A systematic analysis of rapid landsliding (the analysis did not consider creep and other slow semi-continuous processes) indicates that moderate-sized landslides do the most work transporting material on hillslopes. The work peak defines the moderate magnitude, and that magnitude varies based on local physiography and climate. Landslides that form the work peak are distinct from catastrophic landslides that are themselves formative and system resetting. The persistence time for debris slides/debris flows (PDS) and rock slides/rock avalanches (PRS) is calculated over six orders of magnitude. We consider an event catastrophic when it persists in the landscape, as described by a persistence ratio (PF), an order of magnitude longer than the population of landslides that form the work peak.