The prediction of volcanic eruptions and eruption hazards is important to mitigate volcanic hazards. The purpose of the Volcano Program Promotion Panel in the Research Program on Earthquake and Volcanic Observations is to elucidate the conditions and logic of the event branch of volcanic activities, construct a transition model of volcanic activity, and promote research for the prediction of volcanic eruptions. During 2019–2023, submarine and remote-island volcanic eruptions were prominent. Additionally, terrestrial volcanic eruptions highlighted issues in volcanic disaster prevention. Significant progress was realized in material science research. The effects of water content, conduit size, and magma ascent rate on the magma supply systems and eruption explosiveness were evaluated. The relationship between the increase in phenocryst and decrease in eruption size was also elucidated, and the time evolution of the silicic magma system leading up to the caldera-forming eruption was elucidated using a new analytical method based on isotopes. The isotopic ratios of volcanic gases revealed the effects of magma foaming on shallow hydrothermal systems. The importance of rapid analysis of eruptions was highlighted, and magma supply systems and volcanic activity transitions were modeled. Remarkable progress was also made in geophysical observation research. An increase in the amplitude of volcanic tremors and a change in the epicenter location were detected, which were presumed to be caused by the rising of magma before the eruption. New observation techniques were actively introduced, and detailed magnetization structures and temporal changes were detected from aeromagnetic observations using uncrewed aerial vehicles. Distributed acoustic sensing observations were used to determine the epicenter of volcanic earthquakes and estimate the ground structure. Furthermore, seismic survey and ejecta analyses indicated the volume of deposits and magma production process in caldera-forming eruptions. Standardization of the volcanic activity index was promoted through applications of the index for multiple volcanoes as an objective method of volcanic activity evaluation. The addition of highly accurate information on the subsurface structure of volcanoes has advanced our understanding of the eruptive activity and processes. Through these results, the trial and verification of predictions based on the transition model of volcanic activity will be conducted in the following research plan.

1. [1] F. Maeno, A. Yasuda, N. Hokanishi, T. Kaneko, Y. Tamura, M. Yoshimoto, S. Nakano, A. Takagi, M. Takeo, and S. Nakada, “Intermittent growth of a newly-born volcanic island and its feeding system revealed by geological and geochemical monitoring 2013–2020, Nishinoshima, Ogasawara, Japan,” Front. Earth Sci., Vol.9, Article No.773819, 2021. http://doi.org/10.3389/feart.2021.773819
2. [2] T. Kaneko, F. Meano, M. Ichihara, A. Yasuda, T. Ohminato, K. Nogami, S. Nakada, Y. Honda, and H. Murakami, “Episode 4 (2019–2020) Nishinoshima activity: Abrupt transitions in the eruptive style observed by image datasets from multiple satellites,” Earth Planet Space, Vol.74, Article No.34, 2022. https://doi.org/10.1186/s40623-022-01578-6
3. [3] F. Maeno, T. Kaneko, M. Ichihara, Y. J. Suzuki, A. Yasuda, K. Nishida, and T. Ohminato, “Seawater-magma interactions sustained the high column during the 2021 phreatomagmatic eruption of Fukutoku-Oka-no-Ba,” Comm. Earth Environ., Vol.3, Article No.260, 2022. https://doi.org/10.1038/s43247-022-00594-4
4. [4] https://www.data.jma.go.jp/vois/data/obs/kansoku/data_index.html [Accessed December 20, 2024]
5. [5] T. Ohkura, “Vulnerability of Aso Volcano’s disaster mitigation system, as revealed by the phreatic eruption of October 20, 2021,” J. Disaster Res., Vol.19, No.1, pp. 50-55, 2024. https://doi.org/10.20965/jdr.2024.p0050
6. [6] M. Iguchi and T. Yamada, “Volcanic disaster during the eruptive period since 1955 at Sakurajima Volcano,” DPRI Annuals, Vol.64B, pp. 57-72, 2021 (in Japanese with English abstract).
7. [7] H. Nakamichi and M. Sakamoto, “Questionnaire survey of the volcano information to the residents in response to falling ballistic volcanic blocks found on June 8, 2020, in Sakurajima Volcano,” DPRI Annuals., Vol.66B, pp. 111-120, 2023 (in Japanese with English abstract).
8. [8] A. Yasuda, “Magma plumbing system beneath Fuji volcano unraveling from volcanic ejecta,” Kagaku, Vol.92, pp. 611-617, 2022 (in Japanese).
9. [9] Y. Ishizaki, A. Nigorikawa, N. Kametani, M. Yoshimoto, and A. Terada, “Geology and eruption history of the Motoshirane Pyroclastic Cone Group, Kusatu-Shirane Volcano, central Japan,” J. Geol. Soc. Japan, Vol.126, pp. 473-491, 2020 (in Japanese with English abstract). https://doi.org/10.5575/geosoc.2020.0022
10. [10] N. Kametani, Y. Ishizaki, N. Katsuoka, M. Yoshimoto, and A. Terada, “Eruption styles and ages of the Shirane-Minami Crater Chain and the Yumi-ike Maar on the southern foot of the Shirane Pyroclastic Cone Group, Kusatsu-Shirane Volcano, central Japan,” Bull. Volcanol. Soc. Japan, Vol.66, No.1, pp. 1-19, 2021 (in Japanese with English abstract). https://doi.org/10.18940/kazan.66.1_1
11. [11] Y. Ishizaki, W. Numata, and N. Kametani, “Magma discharge step-diagram of Kusatsu-Shirane volcano,” Technical Note of the National Research Institutre for Earth Science and Disaster Resilience, Vol.500, pp. 61-67, 2023.
12. [12] Y. Ikenaga, F. Maeno, and A. Yasuda, “Temporal change in eruption style during the basaltic explosive An’ei eruption of the Izu-Oshima volcano, Japan: insights from stratigraphy and chemical composition analyses,” Front. Earth Sci., Vol.11, Article No.172615, 2023. https://doi.org/10.3389/feart.2023.1172615
13. [13] T. Kuritani, M. Nakagawa, J. Nishimoto, T. Yokoyama, and T. Miyamoto, “Magma plumbing system for the Millennium eruption at Changbaishan volcano China: sonctraints from whole-rock U-Th disequilibrium,” Lithos, Vols.366-367, Article No.105564, 2020. https://doi.org/10.1016/j.lithos.2020.105564
14. [14] T. Kuritani, “Geochemical constraints on the evolution of the magmatic system leading to catastrophic eruptions at Aira Caldera, Japan,” Lithos, Vols.450-451, Article No.107208, 2023. https://doi.org/10.1016/j.lithos.2023.107208
15. [15] M. Ichihara, T. Kobayashi, F. Maeno, T. Ohminato, A. Watanabe, S. Nakada, and T. Kaneko, “The sequence of the 2017–2018 eruptions and seismo-acoustic activity at Kirishima volcano group,” Earth Planets Space, Vol.75, Article No.144, 2023. https://doi.org/10.1186/s40623-023-01883-8
16. [16] T. Obase, H. Sumino, K. Toyama, K. Kawana, K. Yamane, M. Yaguchi, A. Terada, and T. Ohba, “Monitoring of magmatic-hydrothermal system by noble gas and carbon isotopic compositions of fumarolic gases,” Sci. Rep., Vol.12, Article No.17967, 2022. https://doi.org/10.1038/s41598-022-22280-3
17. [17] T. Koyama, T. Kaneko, T. Ohminato, A. Watanabe, T. Yanagisawa, and Y. Honda, “Aeromagnetic survey in volcanoes by using autonomous-driven unmanned helicopter,” BUTSURI-TANSA, Vol.74, pp. 115-122, 2021 (in Japanese). https://doi.org/10.3124/segj.74.115
18. [18] T. Koyama, T. Kaneko, T. Ohminato, A. Watanabe, Y. Honda, T. Akiyama, S. Tanaka, M. Gresse, M. Uyeshima, and Y. Morita, “Magnetization structure and its temporal change of Miyakejima volcano, Japan, revealed by uncrewed aerial vehicle aeromagnetic survey,” J. Disaster Res., Vol.17, No.5, pp. 644-653, 2022. https://doi.org/10.20965/jdr.2022.p0644
19. [19] T. Koyama, T. Kaneko, T. Ohminato, A. Yasuda, T. Ogawa, A. Watanabe, S. Sakashita, M. Takeo, T. Yanagisawa, Y. Honda, and K. Kajiwara, “An ultra-high-resolution autonomous uncrewed helicopter aeromagnetic survey in Izu-oshima Island, Japan,” J. Volcanol. Geotherm. Res., Vol.425, Article No.107527, 2022. https://doi.org/10.1016/j.jvolgeores.2022.107527
20. [20] T. Miwa, N. Geshi, J. Itoh, T. Tanada, and M. Iguchi, “Automatic onsite imaging of volcanic ash particles with VLOCAT: Towards quasi-real-time eruption style monitoring,” J. Volcanol. Geotherm. Res., Vol.416, Article No.107267, 2021. https://doi.org/10.1016/j.jvolgeores.2021.107267
21. [21] M. Mujin and M. Nakamura, “Late-stage groundmass differntiatiion as a record of magma stagnation, fragmentation, and rewelding,” Bull. Volcanol., Vol.82, Article No.48, 2020. https://doi.org/10.1007/s00445-020-01389-1
22. [22] Y. Yukutake, Y. Abe, R. Honda, and S. Sakai, “Magma reservoir and magmatic feeding system beneath Hakone volcano, central Japan, revealed by highly resolved velocity structure,” J. Geophys. Res. Solid Earth, Vol.126, No.4, Article No.e2020JB021236, 2021. https://doi.org/10.1029/2020JB021236
23. [23] Y. Matsunaga, W. Kanda, S. Takakura, T. Koyama, Z. Saito, K. Seki, A. Suzuki, T. Kishita, Y. Kinoshita, and Y. Ogawa, “Magmatic hydrothermal system inferred from the resistivity structure of Kusatsu-Shirane Volcano,” J. Volcanol. Geotherm. Res., Vol.390, Article No.106742, 2020. https://doi.org/10.1016/j.jvolgeores.2019.106742
24. [24] T. Yamada, A. Terada, R. Noguchi, W. Kanda, H. Ueda, H. Aoyama, T. Ohkura, Y. Ogawa, and T. Tanada, “The onset, middle, and climax of precursory hydrothermal intrusion of the 2018 phreatic eruption at Kusatsu-Shirane volcano,” J. Geophys. Res. Solid Earth, Vol.128, No.11, Article No.e2023JB026781, 2023. https://doi.org/10.1029/2023JB026781
25. [25] A. Terada, M. Yaguchi, and T. Ohba, “Quantitative assessment of temporal changes in qubaqueous hydrothermal activity in active crater lakes during unrest based on a time-series of lake water chemistry,” Front. Earth Sci., Vol.9, Article No.740617, 2022. https://doi.org/10.3389/feart.2021.740671
26. [26] T. Nishimura, K. Emoto, H. Nakahara, S. Miura, M. Yamamoto, S. Sugimura, A. Ishikawa, and T. Kimura, “Source location of volcanic earthquakes and subsurface characterization using fiber-optic cable and distributed acoustic sensing system,” Sci. Rep., Vol.11, Article No.6319, 2021. https://doi.org/10.1038/s41598-021-85621-8
27. [27] S. Shimizu, R. Nakaoka, N. Seama, K. Suzuki-Kamata, K. Kaneko, K. Kiyosugi, H. Iwamaru, M. Sano, T. Matsuno, H. Sugioka, and Y. Tatsumi, “Submarine pyroclastic deposits from 7.3ka caldera-forming Kikai-Akahoya eruption,” J. Volcanol. Geotherm. Res., Vol.448, Article No.108017, 2024. https://doi.org/10.1016/j.jvolgeores.2024.108017
28. [28] M. Hamada, T. Hanyu, I.M. McIntosh, M.L.G Tejada, Q. Chang, K. Kaneko, J. Kimura, K. Kiyosugi, T. Miyazaki, R. Nagaoka, K. Nishimura, T. Sato, N. Seama, K. Suzuki-Kamata, S. Tanaka, Y. Tatsumi, K. Ueki, B.S. Vaglarov, and K. Yoshida, “Evolution of magma supply system beneath a submarine lava dome after the 7.3-ka caldera-forming Kikai-Akahoya eruption,” J. Volcanol. Geotherm. Res., Vol.434, Article No.107738, 2023. https://doi.org/10.1016/j.jvolgeores.2022.107738
29. [29] S. Yamamoto, F. Nishizawa, M. Yoshimoto, Y. Miyairi, Y. Yokoyama, H. Suga, and N. Ohkouchi, “Dating lake sediments using compound-specific 14C analysis of C16 fatty acid: A case study from the Mount Fuji volcanic region, Japan,” Geochem. Geophys. Geosys., Vol.22, No.5, Article No.e2020GC009544, 2021. https://doi.org/10.1029/2020GC009544
30. [30] F. Maeno and Y. Ikenaga, “An eruption transition model of Izu-Oshima volcano, Japan,” Technical Note of the National Research Institute for Earth Science and Disaster Resilience, Vol.487, pp. 58-61, 2023 (in Japanese).
31. [31] S. H. Potter, B. J. Scott, G. E. Jolly, V. E. Neall, and D. M. Johnston, “Introducing the Volcanic Unrest Index (VUI): a tool to quantify and communicate the intensity of volcanic unrest,” Bull. Volcanol., Vol.77, Article No.77, 2015. https://doi.org/10.1007/s00445-015-0957-4
32. [32] T. Miwa, M. Nagai, H. Ueda, and A. Yokoo, “Classification of volcanic ash particles with a convolutional neural network on RGB microphotographs: Towards real-time monitoring of an ongoing eruption,” Report of the National Research Institute for Earth Science and Disaster Resilience, Vol.88, pp. 25-31, 2023. https://doi.org/10.24732/NIED.00006516
33. [33] H. Miyamachi, C. Tomari, H. Yakiwara et al., “Shallow velocity structure beneath the Aira caldera and Sakurajima volcano as inferred from refraction analysis of the seismic experiment in 2008,” Bull. Volcanol. Soc. Japan, Vol.58, No.1, pp. 227-237, 2013. https://doi.org/10.18940/kazan.58.1_227
34. [34] T. Nishimura, T. Kozono, A. Matumoto, M. Nakagawa, and M. Iguchi, “Vulcanian eruptions at Sakurajima Volcano: geophysical data, numerical modeling, and petrological evidnece,” Bull. Volcanol., Vol.86, Article No.27, 2024. https://doi.org/10.1007/s00445-024-01722-y
35. [35] L. Olah, H. K. M Tanaka, T. Ohminato, G. Hamar, and D. Varga, “Plug formation imaged beneath the active craterss of Sakurajima volcano with muography,” Geophys. Res. Lett, Vol.46, Nos.17-18, pp. 10417-10424, 2019. https://doi.org/10.1029/2019GL084784
36. [36] L. Olah, G. Gallo, G. Hamar, O. Kamoshida, G. Leone, E. W. Llewellin, D. Lo Presti, G. Nyitrai, T. Ohminato, S. Ohno, H. K. M. Tanaka, and D. Varga, “Muon imaging of volcanic conduit explains link between eruption frequency and ground deformation,” Geophys. Res. Lett., Vol.50, No.2, Article No.e2022GL101170, 2023. https://doi.org/10.1029/2022GL101170
37. [37] F. Maeno, S. Shohata, Y. Suzuki, N. Hokanishi, A. Yasuda, Y. Ikenaga, T. Kaneko, and S. Nakada, “Eruption style transition during the 2017–2018 eruptive activity at the Shinmoedake volcano, Kirishima, Japan: surface phenomena and eruptive products,” Earth Planet Space, Vol.75, Article No.76, 2023. https://doi.org/10.1186/s40623-023-01834-3
38. [38] N. Kametani, Y. Ishizaki, M. Yoshimoto, F. Maeno, A. Terada, R. Furukawa, R. Honda, Y. Ishizuka, J. Komori, M. Nagai, and S. Takarada, “Total mass estimate of the January 23, 2018, phreatic eruption of Kusatsu-Shirane volcano, central Japan,” Earth Planet Space, Vol.73, Article No.141, 2021. https://doi.org/10.1186/s40623-021-01468-3
39. [39] H. Ueda, T. Yamada, T. Miwa, M. Nagai, and T. Matsuzawa, “Development of a data sharing system for Japan Volcanological Data Network,” J. Disaster Res., Vol.14, No.4, pp. 571-579, 2019. https://doi.org/10.20965/jdr.2019.p0571
40. [40] H. Ueda, “Introduction the JVDN (Japan Volcanological Data Network) system,” Bull. Volcanol. Soc. Japan, Vol.69, No.1, pp. 15-20, 2024 (in Japanese). https://doi.org/10.18940/kazan.69.1_15