Island Edifice Failures and Associated Tsunami Hazards

Volcanic ocean islands are prone to structural failure of the edifice that result in landslides that can generate destructive tsunamis. These island landslides range enormously in size, varying from small rock falls to giant sector failures involving tens of cubic kilometers of debris. A survey of literature has allowed us to identify twenty-three processes that contribute to edifice collapse. These have been divided into endogenetic and exogenetic sources of edifice failure. Endogenetic sources of instability and failure include unstable foundations, volcanic intrusions, thermal alteration, edifice pore pressures, unbuttressed structures, and buried faults. Exogenetic sources of instability and failure include collapse of subaerial or submarine deposits, endo-upwelling, karst megaporosity, fractures, oversteepening, overloading, sea-level change, marine erosion, weathering including hurricanes, glacial response, volcanic activity, regional uplift or subsidence, tectonic seismicity and anthropogenic agents. While the endogenetic sources dominate during periods of active volcanism and cone building, the exogenetic sources may cause failure at any time. Tsunamis, both small and large, are associated with these edifice failures.