Japan Geoscience Union Meeting 2024

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-VC Volcanology

[S-VC31] Mechanism of volcanic eruptions

Tue. May 28, 2024 10:45 AM - 12:15 PM 103 (International Conference Hall, Makuhari Messe)

convener:Mayumi Mujin(Tohoku University), Ryo Tanaka(Hokkaido University,Institute of Seismology and Volcanology), Takafumi Maruishi(National Research Institute for Earth Science and Disaster Resilience ), Dan Muramatsu(Earthquake Reserch Institute, The University of Tokyo), Chairperson:Ryo Tanaka(Hokkaido University,Institute of Seismology and Volcanology), Takafumi Maruishi(National Research Institute for Earth Science and Disaster Resilience)

11:00 AM - 11:15 AM

[SVC31-02] Investigating the Eruption Shifting of Kikai 7.3 ka Caldera Forming Eruption: A 3D X-ray Microtomography Study of Eruption Products

*Selvia Novianti1, Atsushi Toramaru1 (1.Department of Earth and Planetary Science, Graduate School of Science, Kyushu University)

Keywords:Kikai Caldera, Caldera Forming Eruption, 3D X-Ray Microtomography, Silicic Magma, Textural Analyses

Kikai Caldera, located in the southwestern part of Japan, has been the subject of extensive research due to its complex volcanic history and potential hazards associated with its eruptions. This study focuses on understanding the eruption shifting of the Kikai Caldera by exploring the relationship between water interaction and the climactic phase of caldera-forming eruptions, which is known to be influenced by the explosivity of the eruption and the characteristics of the silicic magma.


In this research, 3D X-ray microtomography methods are employed to study the eruption products of the Kikai Caldera. The use of this advanced imaging technique allows us to visualize the internal structures and composition of the eruption products in high resolution, providing valuable insights into the mechanisms and processes involved in the eruption shifting from Plinian to Pyroclastic Flow Deposits.


By analyzing the 3D X-ray microtomography images, we aim to identify and characterize the role of water interaction during the climactic phase of the caldera-forming eruption. We quantified 3D vesicle shape distribution and porosity (Φ) which ranged from 0.38 - 0.8 for the Plinian Phase and 0.62 - 0.8 for the climactic phase. This porosity will affect various aspects such as explosivity, fragmentation, and the transport of eruption products. Higher porosity can lead to explosivity, as the rapid expansions of steam and gas within the pumice.


The combination of 3D X-ray microtomography methods and analysis of eruption products will enhance our understanding of the complex interplay between water interaction, explosivity, and magma characteristics in volcanic eruptions. The results of this study will clarify the dynamic behavior of the Kikai Caldera during caldera-forming eruptions and provide valuable information that may assist hazard mitigation shortly, particularly for silicic systems that have a wide range of eruptive styles.