桜島火山の溶岩流(II)-大正溶岩流のシミュレーション-

The progress of the 1914 lava flows on the western side of Sakurajima Volcano was examinedin detail by analyzing the photographs taken during the eruption and then the extrusion rateof the lava was estimated. The reproduction of the lava flows was tried by the numerical simula-tion on the assumption that the viscosity of the lava was constant. The simulated lava flowswere fairly coincided with the actual ones in their extension with time along the direction ofthe main stream. The viscosity of the extruded lava was estimated to be (2-3)xlO 9 poises.The reproduced lava flows, however, disagreed with the actual ones in their lateral spreading.The simulated lava flows tend to spread more widely than the actual ones. In the case of theactual lava flows, it is expected that the temperature of the lava flows decreases faster on thesides of the lava flows than in the main stream. Therefore, it is necessary for the numericalsimulation of the andesitic lava flows to take into account the effect of the cooling of the lava.