5:15 PM - 7:15 PM
[SVC33-P07] Synchrotron analyses of pumice to reveal the formation process of pyroclastic flow
- A case study of 7.6 ka Mashu and 14 ka Me-akan eruptions
Keywords:synchrotron analysis, pumice, pyroclastic flow
Pyroclastic flow has a significant impact on human society, making it crucial to understand their formation process. The stability of the eruption cloud is an essential factor in pyroclastic flow formation[1]. Air entrainment into the eruption column generates buoyancy due to heating and thermal expansion. Additionally, this entrainment leads to the oxidation of pyroclasts. By analyzing the degrees of oxidation based on the Fe3+/Fetot (Fetot = Fe2+ + Fe3+) ratio in volcanic products, we can infer the temperature conditions within volcanic clouds and further discuss the formation mechanisms of pyroclastic flows.
In this study, we performed synchrotron analyses of pumice from 7.6 ka Mashu (Ma-g, -g, -h, -i) [2,3] and 14 ka Me-akan eruptions (M9 - M12)[4] and to examine variations in the Fe3+/Fetot ratio during eruption.
We conducted a field survey and collected samples from pyroclastic fall deposits (Ma-g, -h, -i; M-10, M12) and pyroclastic flow deposits (Ma-f3, M9, M11). The samples were cleaned using an ultrasonic washer and dried at 60-80°C and were sieved. Then pumices larger than 4 mm were selected. For synchrotron analysis, we used powdered pumices. To determine the Fe3+/Fetot ratio, absorption spectra between 650 eV and 750 eV were obtained at room temperature using standard materials at the BL-10 beamline of NewSUBARU, Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Japan.
Our analysis revealed that the Fe3+/Fetot ratio in the 7.6 ka Mashu eruption ranged from 0.8 to 1.0, with pumice in pyroclastic deposits showing lower Fe3+/Fetot ratio. In contrast, the Fe3+/Fetot ratio in Me-akan eruption ranges 0.8 to 0.9, with no significant variation among pumice samples. These variations in the Fe3+/Fetot ratio provide valuable insight into the temperature condition within volcanic cloud and contribute to a better understanding of pyroclastic formation.
References
[1] A. W. Woods: Bulletin of Volcanology. 50, 169-193,1988.
[2] H. Kishimoto, T. Hasegawa, M. Nakagawa, K, Wada: Bulletin of the Volcanological Society of Japan. 54, 15-36, 2009.
[3] T. Hasegawa, S. Shibata, T. Kobayashi, N. Mochizuki, M. Nakagawa, H. Kishimoto: Bulletin of the Volcanological Society of Japan. 66, 187-210 ,2021.
[4] K. Wada, E. Sato: Journal of Hokkaido University of Education (Basic Research), 75, No.1, 2024
In this study, we performed synchrotron analyses of pumice from 7.6 ka Mashu (Ma-g, -g, -h, -i) [2,3] and 14 ka Me-akan eruptions (M9 - M12)[4] and to examine variations in the Fe3+/Fetot ratio during eruption.
We conducted a field survey and collected samples from pyroclastic fall deposits (Ma-g, -h, -i; M-10, M12) and pyroclastic flow deposits (Ma-f3, M9, M11). The samples were cleaned using an ultrasonic washer and dried at 60-80°C and were sieved. Then pumices larger than 4 mm were selected. For synchrotron analysis, we used powdered pumices. To determine the Fe3+/Fetot ratio, absorption spectra between 650 eV and 750 eV were obtained at room temperature using standard materials at the BL-10 beamline of NewSUBARU, Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Japan.
Our analysis revealed that the Fe3+/Fetot ratio in the 7.6 ka Mashu eruption ranged from 0.8 to 1.0, with pumice in pyroclastic deposits showing lower Fe3+/Fetot ratio. In contrast, the Fe3+/Fetot ratio in Me-akan eruption ranges 0.8 to 0.9, with no significant variation among pumice samples. These variations in the Fe3+/Fetot ratio provide valuable insight into the temperature condition within volcanic cloud and contribute to a better understanding of pyroclastic formation.
References
[1] A. W. Woods: Bulletin of Volcanology. 50, 169-193,1988.
[2] H. Kishimoto, T. Hasegawa, M. Nakagawa, K, Wada: Bulletin of the Volcanological Society of Japan. 54, 15-36, 2009.
[3] T. Hasegawa, S. Shibata, T. Kobayashi, N. Mochizuki, M. Nakagawa, H. Kishimoto: Bulletin of the Volcanological Society of Japan. 66, 187-210 ,2021.
[4] K. Wada, E. Sato: Journal of Hokkaido University of Education (Basic Research), 75, No.1, 2024