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Fig. 9 | Earth, Planets and Space

Fig. 9

From: Source constraints for the 2015 phreatic eruption of Hakone volcano, Japan, based on geological analysis and resistivity structure

Fig. 9

Schematic geological model of 2015 eruption center and adjacent area. Beneath the eruption center area, a vapor pocket is formed, and the steam migrates from the pocket to the surface through Layer IIa, which is a sub-unit of Layer II characterized by mineral formation due to boiling. Mineral assemblage from the borehole data indicates an underground temperature of approximately 200 °C, even at the bottom of SPW52. The open crack formed at 7:32 on June 29, 2015 (JST), triggered the eruption; however, the uppermost tip did not reach the surface. The steam emitted by the eruption originated from the vapor pocket, and craters were formed by the erosion of Layer A or Layer IIa

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