Life and death of slow-moving landslides

Abstract

In the most destructive and catastrophic landslide events, rocks, soil and fluids can travel at speeds approaching several tens of metres per second. However, many landslides, commonly referred to as slow-moving landslides, creep at rates ranging from millimetres to several metres per year and can persist for years to decades. Although slow-moving landslides rarely claim lives, they can cause major damage to infrastructure and sometimes fail catastrophically, transitioning into fast-moving landslides that can result in thousands of casualties. In addition, slow-moving landslides are highly erosive features that control the landscape morphology in many mountainous regions (such as the California Coast Ranges or the Apennines). The persistent and long-term motion of slow-moving landslides provides an exceptional opportunity to investigate landslide processes and mechanisms. In this Review, we examine the environmental conditions (such as geology, climate and tectonics) of slow-moving-landslide-prone regions, analyse the forcings (for example, precipitation and groundwater, earthquakes, river erosion, anthropogenic forcings and external material supply) that drive their motion and investigate the subsequent implications of the different forcings on landslide dynamics. We then discuss circumstances in which slow-moving landslides can accelerate rapidly, move large distances or even fail catastrophically. Finally, we provide new perspectives and challenges for future landslide research. Some landslides creep at low velocities of a few millimetres to metres per year, forced by external factors such as rainfall, snowmelt, earthquakes or anthropogenic forcings. This Review discusses the recent advances in understanding slow-moving landslides and examines circumstances where slow-moving landslides can accelerate and fail catastrophically.