火山 第 59 巻 ( 2014)
第 4 号 287-298 頁論 説

1888 年磐梯山水蒸気爆発に関するノート
─（3）1888 年の水蒸気爆発論考に潜むジレンマ─
浜 口 博 之＊・植 木 貞 人＊＊・中 道 治 久＊＊＊（2014 年 5 月 22 日受付，2014 年 10 月 17 日受理）

Notes on the 1888 Phreatic Explosion at Bandai Volcano(3) Hidden Dilemmas in Interpretation of the Mechanismof the 1888 Phreatic Explosion
Hiroyuki HAMAGUCHI＊, Sadato UEKI＊＊ and Haruhisa NAKAMICHI＊＊＊A great phreatic explosion at Bandai volcano on 15 July 1888 was accompanied by a huge rock avalanche thatflowed northward and strong windblasts and mudflows that flowed southeastward. This extraordinary eruption occurredat the dawn of modern Japanese civilization during the middle Meiji era when the Imperial University of Tokyo began tointroduce to their curriculum for systematic studies of scientific theory developed in the western world.
Although more than 120 years have passed since the eruption, no firm conclusions have been reached about themechanism of the 1888 phreatic explosion at Bandai. This is partly because statements and interpretations by Sekiya andKikuchi (1890) were based on circumstantial evidence from their own observations and those of local inhabitants, andpartly because in their 1890 paper, Sekiya and Kikuchi chose to disregard scenarios for the eruption other than the one
they published in Japanese. However, after a critical review of their paper and related reports written in Japanese, wefound evidence that Prof. Sekiya (the first Japanese seismologist) and Associate Prof. Kikuchi (a young and spiritedgeologist) had different opinions on the mechanism of the 1888 eruption. Therefore, they faced several dilemmas whenpreparing their paper for publication. For example, they disagreed on whether the explosive source was beneath
Kobandai-san (the collapsed edifice after the 1888 eruption) or beneath Numanotaira (the old crater). Prof. Sekiya
appears to have overruled his junior colleague: their published interpretation of events was based on Humboldtʼs (1849)
outdated views on the causes of earthquakes and volcanic eruptions. Associate Prof. Kukuchi favored the more modern
theory of volcanism of Scrope (1862), but consented reluctantly to Prof. Sekiyaʼs interpretation of the mechanism of the1888 eruption. Here, we provide a detailed discussion of how the dilemma faced by these scientists developed and revealthat they were deeply affected by mid-19th century controversies in geological theory as espoused in the western world.
We must take into account that Japanese geologists of that era generally accepted the western worldʼs theories about thecauses of earthquakes and volcanic eruptions, some of which are now seen to be fanciful.
Key words : volcanism, Bandai volcano, phreatic explosion, scientific dilemma

1．は じ め にについては様々な解釈があり，いまだに混迷した状態が磐梯山水蒸気爆発の噴火位置，規模やメカニズムなど続いている．例えば，最初の噴火位置の同定についての＊＊＊＊〒981-3122 宮城県仙台市泉区加茂 2-6-2
2-6-2 Kamo, Izumi-ku, Sendai, Miyagi 982-3122, Japan.
＊＊〒980-8578 宮城県仙台市青葉区荒巻字青葉 6-6
東北大学大学院理学研究科附属地震・噴火予知研究観測センター
Research Center for Prediction of Earthquakes andVolcanic Eruptions, Graduate School of Science, Tohoku
University, 6-6 Aoba Aramaki, Aoba-ku, Sendai, Miyagi
980-8578, Japan.

〒891-1419 鹿児島県鹿児島市桜島横山町 1722-19
京都大学防災研究所附属火山活動研究センター
Sakurajima Volcano Research Center, Disaster Prevention Research Institute, Kyoto University, 1722-19
Sakurajima-yokoyama, Kogoshima, Kagoshima 891-1419,
Japan.
Corresponding author: Hiroyuki Hamaguchi
e-mail: hamaguti@cello.ocn.ne.jp