Subaqueous Pyroclastic Deposits from Tambora and Krakatau Volcanoes, Indonesia

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During the great explosive eruptions of Tambora in Indonesia as up to 30 km3 of pyroclastic flows may have entered the ocean during the 1815 event. Similarly, pyroclastic or debris flows of unknown character formed up to 30 m thick submarine deposits up to 15km from the Krakatau volcano in the 1883 event. The nature of the interaction between subaerial pyroclastic flows and the sea is poorly understood but is critical to competing models of volcanogenic tsunami generation and of the formation of co-ignimbrite ash. The PIs will study the submarine deposits from tambora (1815) and Krakatau (1883) by using a suite of existing piston and gravity cores from the Tambora area and by collection of new cores from the shallow seas around Krakatau. The results of the study will be used to 1) test existing models for the generation of tsunamis and co-ignimbrite ash fall during the Tambora and Krakatau eruptions, 2) develop general models for the interaction of pyroclastic flows and seawater, and 3) characterize the nature of subaqueous deposits formed by such interactions. These results will be significant in terms of understanding the eruptive processes of these events and providing modern analogues of volcaniclastic sedimentation that can be applied to ancient convergent margin sequences in the geologic record. The project is being co- funded with National Geographic Society.