Estimate of pyroclastic flow velocities resulting from explosive decompression of lava domes

摘要: APPARENTLY benign silicic domes or lava flows can travel for several kilometres and then suddenly collapse to generate pyroclastic phenomena capable of causing widespread destruction, as happened recently at Mount Unzen in Japan1. Two sources have been proposed the energy that propels such 'Pelean' 'Merapi'-type2 flows: gravitational col-lapse (supplemented by heating expansion air) sudden pressurized gases from inside flow. If gravity controls transfer, areas likely be affected predicted on basis topography3, resulting deposits will bear a simple relationship part flow which they issued. But if gas pressure adds significant contribution, hazard assessment becomes more difficult because decompression velocities beyond those acquired forces, putting much larger risk forming are relate their source. Here we estimate initial generated dome disintegration range compositions volatile contents, offer conceptual framework correlating dynamics dome-front with sediment record. Our results indicate explosive distal portions cause comparable collapse, especially cases where volatiles become locally concentrated above equilibrium values.