[M-IS24] History X Earth and Planetary Science

[MIS24-P01] Reconsideration of an eruption at Chokai volcano in the 19th century using historical documents, NE Japan

*Nanami Jimba¹, Takehiko Suzuki¹, Yasuyuki Kano², Junzo Ohmura² (1.Department of Geography, Tokyo Metropolitan University, 2.Earthquake Research Institute, The University of Tokyo)

Keywords:Chokai volcano, histrical documents

Chokai volcanoVolcano, located on the border between Akita and Yamagata Prefectures, is an active volcano with many recorded eruptions in historical period. However, there are few studies on the pyroclastic deposit of historical eruptions, and geological knowledge is not sufficient. Therefore, information obtained from historical records is important for understanding the actual state of Chokai volcano’s recent eruptions. Although previous studies (Ueki, 1981; Anezaki, 1952, and so on) have investigated the eruption history of Chokai volcano based on historical records, many of these studies have issues such as unclear sources for the referenced historical documents or only mentioning the names of historical documents without providing access to their original texts. If original data cannot be accessed, it is difficult to verify whether the recorded information is reliable as an eruption record. In Hayashi et al. (2013), two documents from the “Akumi-Distirct-History” of Yamagata Prefecture were examined to analyze the 1801–1804 eruptions. However, no studies have been conducted in the progression of eruptions on historical records from Akita Prefecture that clarify the sources of historical documents and provide detailed analyses of these documents. Therefore, this study focuses on historical records from the Chokai volcano’s eruptions occurred in Edo period. By verifying and transcribing original documents, we aim to organize the data, assess the reliability of the sources, and reconsider detailed sequence of each eruption.
For this study, historical documents were investigated at the Yajima Local History Museum in Yurihonjo City and the Kisakata Local History Museum in Nikaho City. Through this investigation, several historical documents were obtained, including “Chokai-san-Kemuri-Yake-Mitodoke-Oboe”, “Kyowa-Ninen-Yori-Meiji-Shonen-Made-Kikin-Chokai-san-Funka-no-Koto” , and “Kyowa-Gannen-Chokai-san-Yama-Yake-Narabini-Jishin-No-Ki”. Additionally, previously introduced documents such as “Sai-Dai-Ki” and “Sai-Dai-Kiroku” were also examined.
Among these,“Chokai-san-Kemuri-Yake-Mitodoke-Oboe”, preserved at the Yajima Local History Museum, is considered particularly important for research. In Anezaki (1952), a document called “Old record in Yajima” was introduced. However, this record merely indicates "historical records preserved in the Yajima area," and the original source of the quoted information remained unclear. When comparing the old record with “Chokai-san-Kemuri-Yake-Mitodoke-Oboe”, the latter records the same events as the old record and contains matching descriptions, supporting the credibility of the old record. Therefore, “Chokai-san-Kemuri-Yake-Mitodoke-Oboe” serves as a complementary historical source for “Old record in Yajima”, which had been considered unverifiable due to an unknown original source. Furthermore, it is believed to be a copy of a detailed eruption report prepared in response to a request from the Shonai Domain.
The obtained documents provide detailed descriptions of the 1801–1804 and 1821 eruptions. We plan to focus on reconstructing the spatiotemporal progression of various eruption phenomena based on these descriptions. Additionally, we will continue historical record investigations to further enhance the content and accuracy of our findings.

Acknowledgments: I would like to express my sincere gratitude to the Yajima Local History Museum in Yurihonjo City and the Kisakata Local History Museum in Nikaho City, and the Tsuruoka Local History Museum inTsuruoka City for their cooperation in the historical document research.