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 l andslides range enormously in size, varying from small rock falls to giant sector failures involving tens of cubic kilometers of debris. A survey of l iterature has allowed us to identify twenty-three processes that contribute to edifice collapse. These have been divided into endogenetic and exogenet ic sources of edifice failure. Endogenetic sources of instability and failu re include unstable foundations, volcanic intrusions, thermal alteration, e difice pore pressures, unbuttressed structures, and buried faults. Exogenet ic sources of instability and failure include collapse of subaerial or subm arine deposits, endo-upwelling, karst megaporosity, fractures, oversteepeni ng, overloading, sea-level change, marine erosion, weathering including hur ricanes, glacial response, volcanic activity, regional uplift or subsidence , tectonic seismicity and anthropogenic agents. While the endogenetic sourc es dominate during periods of active volcanism and cone building, the exoge netic sources may cause failure at any time. Tsunamis, both small and large , are associated with these edifice failures.