An overview of break-out floods from intracaldera lakes

Large-scale terrestrial impoundments of surface water, i.e. lakes, are an effective source of major floods because they can release huge volumes of water directly into a drainage route should their margins be breached. Failures of temporary lakes, developed behind glacial or alluvial barriers during the termination of the Last Glacial Maximum, are responsible for the largest floods recognised on Earth in the Late Pleistocene. Break-outs of volcanogenic lakes developed in intracaldera settings constitute the second largest category of terrestrial floods in terms of peak discharge and volumes of water released, exceeding the magnitude of break-outs from other volcanic impoundments such as lava, debris avalanche, and pyroclastic flow dams, which are of a similar scale to failures of other natural dams such as landslides and moraines. Intracaldera break-out floods have been recognised in an increasing number of volcanic arcs around the world, including Alaska, New Zealand, and Japan, with additional candidates identified in Indonesia and Kamchatka. In many cases, repeated break-out floods have occurred at a single caldera due to repeated damming of the outlet by volcanic activity at the host or an adjacent eruptive centre. Palaeohydraulic reconstructions of some of these events indicate that they are amongst the largest postglacial floods on Earth.