Eruption style transition during the 2017–2018 eruptive activity at the Shinmoedake volcano, Kirishima, Japan: surface phenomena and eruptive products

Earth, Planets and Space

Full Paper

Yuya Ikenaga¹  Takayuki Kaneko²  Natsumi Hokanishi²  Atsushi Yasuda²  Fukashi Maeno²  Setsuya Nakada³  Sayaka Shohata⁴  Yuki Suzuki⁵ 

[1] Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-0033, Tokyo, Japan;Earthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, 113-0032, Tokyo, Japan;National Research Institute for Earth Science and Disaster Resilience, 3-1 Tennodai, 305-0006, Tsukuba, Japan;Tera Technology, Inc, Ikebukuro East Bldg., Higashi Ikebukuro 3-4-3, Toshima-ku, 170-0013, Tokyo, Japan;Waseda University, 1-6-1 Nishi-Waseda, Shinjuku-ku, 169-8050, Tokyo, Japan;

关键词: Lava dome;    Phreatic;    Phreatomagmatic;    Effusive;    Explosive;    Subplinian;    Number density;    Shinmoedake;   

DOI  :  10.1186/s40623-023-01834-3

 received in 2022-10-21, accepted in 2023-04-25,  发布年份 2023

来源: Springer

【 摘 要 】

Recent eruptions of the Shinmoedake volcano, Japan, have provided a valuable opportunity to investigate the transition between explosive and effusive eruptions. In October 2017, phreatic/phreatomagmatic explosions occurred. They were followed in March 2018 by a phase of hybrid activity with simultaneous explosions and lava flows and then a transition to intermittent, Vulcanian-style explosions. Evolution of surface phenomena, temporal variations of whole-rock chemical compositions from representative eruptive material samples, and rock microtextural properties, such as the crystallinity and crystal size distribution of juvenile products, are analyzed to characterize the eruption style transition, the conduit location, and the shallow magma conditions of the volcanic edifice. The 2017–2018 eruptive event is also compared with the preceding 2011 explosive–effusive eruption. The chemical and textural properties of the 2018 products (two types of pumice, ballistically ejected lava blocks, and massive lava) are representative of distinct cooling and magma ascent processes. The initial pumice, erupted during lava dome formation, has a groundmass crystallinity of up to 45% and the highest plagioclase number density of all products (1.9 × 106/mm3). Conversely, pumice that erupted later has the lowest plagioclase number density (1.2 × 105/mm3) and the highest nucleation density (23/mm4 in natural logarithm). This 2018 pumice is similar to the 2011 subplinian pumice. Therefore, it was likely produced by undegassed magma with a high discharge rate. Ballistics and massive lava in 2018 are comparable to the 2011 Vulcanian ballistics. Conversely, the high plagioclase number density pumice that occurred in 2018 was not observed during the 2011 eruption. Thus, such pumice might be specific to hybrid eruptions defined by small-scale explosions and lava dome formation with low magma discharge. The observed transitions and temporal variations of the activities and eruption style during the 2017–2018 Shinmoedake eruptions were primarily influenced by the ascent rate of andesitic magma and the geological structure beneath the summit crater.Graphical Abstract

【 授权许可】

CC BY   
© The Author(s) 2023

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