Precursory activity and evolution of the 2011 eruption of Shinmoe-dake in Kirishima volcano-insights from ash samples

Yuki Suzuki, Masashi Nagai, Fukashi Maeno, Atsushi Yasuda, Natsumi Hokanishi, Taketo Shimano, Mie Ichihara, Takayuki Kaneko, Setsuya Nakada

研究成果: Article査読

35 被引用数 (Scopus)

抄録

After a precursory phreatic stage (2008 to 2010), the 2011 Shinmoe-dake eruption entered a phreatomagmatic stage on January 19, a sub-Plinian and lava accumulation stage at the end of January, a vulcanian stage in February-April, and a second phreatomagmatic stage in June-August. Component ratio, bulk composition, and particle size of the samples helped us define the eruptive stages. The juvenile particles were first found in the January 19 sample as pumice (8 vol%) and were consistently present as scoria and pumice particles thereafter (generally ∼50 vol%, decreasing in weaker events). The January 19 pumice has water-quench texture. After the lava accumulation, particles of that lava origin came to account for 30∼70 vol% of the ash. The second phreatomagmatic stage is proposed because of fine ash and long eruption period. The SiO2 contents of bulk ash are lower in post-January 19, 2011 eruptions, reflecting lower average SiO2 contents in 2011 ejecta than in past ejecta. The free-crystal assemblages were two pyroxenes + plagioclase + Fe-Ti oxides until 2010; olivine joined the assemblage in 2011, when juvenile ash was erupted. This change is consistent with the absence or smaller sizes of olivine phenocrysts in past ejecta.

本文言語English
ページ(範囲)591-607
ページ数17
ジャーナルEarth, Planets and Space
65
6
DOI
出版ステータスPublished - 2013
外部発表はい

ASJC Scopus subject areas

  • 地質学
  • 宇宙惑星科学

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