An overview of rock avalanche-substrate interactions

Abstract

Large rock or debris avalanches inevitably encounter and interact with a variety of earth materials along their paths. These substrate materials influence rock and debris avalanche emplacement in one or several of the following ways (1) longer runout due to an increase in volume by entrainment on the steep failure slope, (2) higher mobility by reduction in basal frictional resistance (e.g. emplacement over glacier ice), or (3) a larger area of deposition due to transformation into debris flows, contrasted by (4) runout impediment due to interactions along the flatter runout path (e.g. bulldozing of substrate material or entrainment of high-friction debris), and introducing (5) flow complexities resulting from changes in basal mechanical properties and other localized interactions. Additionally, the total area affected by a rock avalanche may extend beyond the deposit margin itself when sediments in front of the rock avalanche are bulldozed or are mobilized and flow independent of the rock avalanche for some further distance.