Publication Date:
2023-06-19
Description:
Phreatic eruption is hazardous phenomena ubiquitously observed in active volcanoes. The eruptions are sourced from solid (altered rock, and etc)-water system underground. It is surely that the expansion of water in the system drives the eruptions, however, evaluation of water content of the system has not been enough. The quantification of the water content is essential for understandings on the mechanism of the phreatic eruptions. Here we estimate the water content in solid-water system driving the phreatic eruptions, by combining the geological and geophysical approaches. We dealt with three phreatic eruptions (Feb 7-9, 2012; Feb 17-18, 2013; Apr 11, 2013) at Ioto volcano, Japan. The detailed geological survey gives eruptive volume of the three phreatic eruptions. On the other hand, the seismic and infrasound analyses give the total volume emitted (solid+liquid+gas) in the three eruptions. Subtracting the solid volume from the total volume provides a volume of water emitted. The water volume was converted to the mass by using ideal gas equation of state and temperature. Then, the mass fractions of water in the three phreatic eruptions were estimated to 16-33 wt.%. The result of our study shows that there are positive correlations among the masses of water and solid, and mass fraction of water. This fact suggests that large hydrothermal chamber which is generated by high water flux from deeper part fuels large scale phreatic eruption. The observation of hydrothermal chamber size and water flux from deeper part will be critical for prediction of volcanic hazard from phreatic eruptions.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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