Volcanic activity of Nishinoshima volcano from 2013 to 2015

Nishinoshima is an andesitic volcano located on the Izu-Ogasawara volcanic front. Its submarine eruption was observed for the first time in history in June 1973 and the volcanic activity continued to 1974. On November 20, 2013, the Maritime Self-Defense Force crew of the aircraft saw plume discharged from the southeast of Nishinoshima. The Japan Coast Guard immediately carried out observations by aircraft on the day. We confirmed that a phreatomagnetic eruption had occurred and that the pyroclastic deposits had formed new land to the southeast of Nishinoshima Island. On November 22, 2013, lava flowed out from pyroclastic cone and the eruption changed to a magnetic one. Characteristics of the volcanic activity was intermittent eruption continuing and extension of Nishinoshima Island by lava flow. The eruptive activity became quiet after a vulcanian eruption was observed on November 15, 2017. Although the volcanic activity kept calm for about a year and a half, a strombolian eruption and lava flow were observed on April 20, 2017 and Nishinoshima volcano started eruptive activity again. The Japan Coast Guard has been routinely observing volcanic activities of Nishinoshima volcano from aircraft. Ono et al. (2015) reported the volcanic activities before September 17, 2014. Therefore we report those from October 16, 2014 to March 22, 2017 before any re-eruption of Nishinoshima.