Total mass estimate of the January 23, 2018, phreatic eruption of Kusatsu-Shirane Volcano, central Japan

• Published in: Earth, planets, and space planets, and space, 2021-07, Vol.73 (1), p.1-10, Article 141
• Main Authors: Kametani, Nobuko, Ishizaki, Yasuo, Yoshimoto, Mitsuhiro, Maeno, Fukashi, Terada, Akihiko, Furukawa, Ryuta, Honda, Ryo, Ishizuka, Yoshihiro, Komori, Jiro, Nagai, Masashi, Takarada, Shinji
• Format: Article
• Language: English
• Subjects: 5. Volcanology; Ashes; Craters; Earth and Environmental Science; Earth Sciences; Express Letter; Fall deposit; Geology; Geophysics/Geodesy; Isomass contour map; Japan; Kusatsu-Shirane Volcano; Mass estimate; Observations; Phreatic eruption; Phreatomagmatism; Understanding phreatic eruptions - recent observations of Kusatsu-Shirane volcano and equivalents; Volcanic activity; Volcanic ash; Volcanic craters; Volcanic deposits; Volcanic eruptions; Volcanoes
• ISSN: 1880-5981; 1343-8832; 1880-5981
• DOI: 10.1186/s40623-021-01468-3

On January 23, 2018, a small phreatic eruption (VEI = 1) occurred at the Motoshirane Pyroclastic Cone Group in the southern part of Kusatsu-Shirane Volcano in central Japan. The eruption ejected ash, lapillus, and volcanic blocks from three newly opened craters: the main crater (MC), west crater (WC), and south crater (SC). Volcanic blocks were deposited up to 0.5 km from each crater. In contrast, the ash released during this eruption fell up to 25 km ENE of the volcano. The total mass of the fall deposit generated by the eruption was estimated using two methods, yielding total masses of 3.4 × 10 4 t (segment integration method) and 2.4 × 10 4 t (Weibull fitting method). The calculations indicate that approximately 70% of the fall deposit was located within 0.5 km of the craters, which was mainly attributed to the low height of the eruption plume.