1,- 1Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan (saito.konan.n1@s.mail.nagoya-u.ac.jp)
- 2Japan Synchrotron Radiation Research Institute, Sayo-gun, Japan
- 3Center for Northeast Asian Studies, Tohoku University, Sendai, Japan
The dynamics of eruptions are controlled by volcanic outgassing through interconnected bubble networks. The question of whether frameworks formed by crystals facilitate gas escape remains unresolved, with the relative spatial arrangements of bubbles and crystals yet to be elucidated. In the presentation, we will show multi-resolution X-ray computed tomography (CT) imaging conducted to examine vesicle-crystal spatial relationships in a dacite bomb, a lava block in a pyroclastic flow deposit, and spine lavas from the 1990-1995 Unzen eruption. The acquisition of micro-CT, computed laminography (CL), and nano-CT images with progressively higher resolution was undertaken. Reconstructed 3D images demonstrate that large vesicles are consistently connected to crystals across all sample types and analysis scales. Size distribution analysis demonstrates preferential connectivity between large vesicles and large crystals. Vesicles in the bread crust bomb that appear isolated are found to form interconnected networks. In contrast, vesicles in shear-deformed dome samples are found to occupy narrow inter-crystal gaps as sheet-like structures. The findings of this study indicate that interconnected bubble networks facilitate efficient initial outgassing at depths of 0.5-0.8 km. The findings of calculations of compaction timescales and gas flow modelling corroborate this assertion. Crystal supported pathways facilitate the subsequent transport of ascending gas through shallow conduit regions. The compaction of crystal-bearing, interconnected bubbles causes the subsequent development of crystal frameworks. These phenomena serve as pathways for outgassing during the final ascent, leading to the formation of the dome.
Reference:
Saito, K., Hoshino, M., Goto, A., Namiki, A. A computed tomography observation of the Unzen lava reveals the frequent existence of vesicles and crystals in proximity. Sci Rep 16, 81 (2026). https://doi.org/10.1038/s41598-025-28770-4
How to cite: Saito, K., Hoshino, M., Goto, A., and Namiki, A.: A computed tomography observation of the Unzen lava reveals the frequent existence of vesicles and crystals in proximity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2676, https://doi.org/10.5194/egusphere-egu26-2676, 2026.
