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Volcanic plume measurements using a UAV for the 2014 Mt. Ontake eruption

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Title: Volcanic plume measurements using a UAV for the 2014 Mt. Ontake eruption
Authors: Mori, Toshiya Browse this author
Hashimoto, Takeshi Browse this author →KAKEN DB
Terada, Akihiko Browse this author
Yoshimoto, Mitsuhiro Browse this author
Kazahaya, Ryunosuke Browse this author
Shinohara, Hiroshi Browse this author
Tanaka, Ryo Browse this author
Keywords: Mt. Ontake
The 2014 eruption
Phreatic eruption
Volcanic plume
Sulfur dioxide
Hydrogen sulfide
Volcanic gas flux
Issue Date: 22-Mar-2016
Publisher: Springer
Journal Title: Earth, Planets and Space
Volume: 68
Issue: 1
Start Page: 49
Publisher DOI: 10.1186/s40623-016-0418-0
Abstract: A phreatic eruption of Mt. Ontake, Japan, started abruptly on September 27, 2014, and caused the worst volcanic calamity in recent 70 years in Japan. We conducted volcanic plume surveys using an electric multirotor unmanned aerial vehicle to elucidate the conditions of Mt. Ontake’s plume, which is flowing over 3000 m altitude. A plume gas composition, sulfur dioxide flux and thermal image measurements and a particle sampling were carried out using the unmanned aerial vehicle for three field campaigns on November 20 and 21, 2014, and June 2, 2015. Together with the results of manned helicopter and aircraft observations, we revealed that the plume of Mt. Ontake was not directly emitted from the magma but was influenced by hydrothermal system, and observed SO2/H2S molar ratios were decreasing after the eruption. High SO2 flux of >2000 t/d observed at least until 20 h after the onset of the eruption implies significant input of magmatic gas and the flux quickly decreased to about 130 t/d in 2 months. In contrast, H2S fluxes retrieved using SO2/H2S ratio and SO2 flux showed significantly high level of 700–800 t/d, which continued at least between 2 weeks and 2 months after the eruption. This is a peculiar feature of the 2014 Mt. Ontake eruption. Considering the trends of the flux changes of SO2 and H2S, we presume that majority of SO2 and H2S are supplied, respectively, from high-temperature magmatic fluid of a deep origin and from hydrothermal system. From the point of view of SO2/H2S ratios and fumarolic temperatures, the plume degassing trend after the 2014 eruption is following the similar course as that after the 1979 eruptions, and we speculate the 2014 eruptive activity will cease slowly similar to the 1979 eruption.
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 橋本 武志

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