One of more than 20 volcanic peaks in the Kirishima mountain range on the Kagoshima-Miyazaki prefectural border, Shinmoedake is believed to have formed between 7,300 and 25,000 years ago.
Most of the recorded eruptions on the Kirishima range have occurred at Shinmoedake and Ohachi peaks.
Small eruptions caused by phreatic explosions were observed on Shinmoedake from March to May last year. Phreatic explosions occur when the heat of rising magma causes underground water to boil and steam pressure rises.
According to experts, however, the eruptions that have taken place since Wednesday are explosive eruptions characteristic of phreatomagmatic explosions, which are caused when magma and underground water directly interact. Read More..