Dynamics of Volcanic Explosion

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This project aims at better understanding of fundamental processes and mechanisms of volcanic explosions with some contribution to volcanic hazard mitigation. The "Mobile Observatory for Volcanic Explosions" that can be moved and operated for observations, sampling and device installation in the vicinity of volcanic craters with a remote control has been developed for detailed studies of volcanic eruptions. New data sets of broad-band seismograms and air-wave records obtained at some volcanoes involving frequent small explosions have revealed the presence of characteristic inflation and deflation prior to each explosion as a common physical process. Theoretical and experimental studies on volcanic materials have specified the factors that may control degassing and fragmentation of ascending magma. Computer simulations about magma ascent processes have clarified the conditions that may determine explosiveness of eruptions and have shown that the explosiveness can be predicted by accelerated inflation. A three-dimensional simulation scheme of effusing gassy flow mixed with magma fragments has been developed to describe volcanic plumes and pyroclastic flows. Scaling of explosions and simulation of explosive air flow also provide useful methods to evaluate influences of volcanic explosions.Compiling our research outcomes and some other knowledge, a database, which is useful for a systematic understanding of volcanic explosions, has been constructed. This database and some computer programs developed in this project can be basic tools in simulating the entire eruptive processes and evaluating possible volcanic hazards. A web server also has been developed for prompt decisions to derive from efficient discussions at volcanic crises. Some lectures about volcanic explosions for the public were given with some demonstration of our studies. A textbook that may explain our research results to the general people will be published.