Long undersea debris runout can be facilitated by a boundary layer formed by weak marine sediments under a moving slide mass. Undrained loading of such offshore sediment results in a profound drop of basal shear resistance, compared to subaerial shear resistance, enabling long undersea runout. Thus large longrunout submarine landslides are not truly enigmatic (Voight and Elsworth 1992, 1997), but are understandable in terms of conventional geotechnical principles. A corollary is that remoulded undrained strength, and not friction angle, should be used for basal resistance in numerical simulations. This hypothesis is testable via drilling and examining the structure at the soles of undersea debris avalanches for indications of incorporation of sheared marine sediments, by tests of soil properties, and by simulations. Such considerations of emplacement process are an aim of ongoing research in the Lesser Antilles (Caribbean Sea), where multiple offshore debris avalanche and dome-collapse debris deposits have been identified since 1999 on swath bathymetric surveys collected in five oceanographic cruises. This paper reviews the prehistoric and historic collapses that have occurred offshore of Antilles arc islands and summarizes ongoing research on emplacement processes.
Times Cited: 0 5th International Symposium on Submarine Mass Movements and Their Consequences OCT 24-26, 2011 Kyoto, JAPAN IUGS UNESCO; United Nations Educ Sci & Cultural Org; IUGS; Integrated Ocean Drill Program; Tokyo Geograph Soc; Inoue Fdn Sci; KAkenhi NAnkal Megathrust Earthquakes; Sedimentological Soc Japan; Kyoto Univ Global COE Program; Japan Drill Earth Sci Consortium