Open AccessTime Variation in the Chemical and Isotopic Composition of Volcanic Gas at Mt. Mihara of Izu-Oshima Island, Japan
Author(s) -
Takayoshi Ohba,
Muga Yaguchi,
Kaishino,
Nozomi Numanami
Publication year - 2019
Publication title -
journal of disaster research
Language(s) - English
Resource type - Journals
eISSN - 1883-8030
pISSN - 1881-2473
DOI - 10.20965/jdr.2019.p0972
Subject(s) - fumarole , volcano , impact crater , borehole , geology , hydrothermal circulation , volcanic gases , crater lake , gas composition , geochemistry , phreatic eruption , chemical composition , mineralogy , magma , chemistry , seismology , paleontology , physics , organic chemistry , thermodynamics , astronomy
Volcanic gas was sampled at three fumaroles and one borehole on Mt. Mihara, Izu-Oshima volcano. The fumarolic gas and the borehole steam possessed an excess enthalpy relative to the air saturated with water vapor. The fumarolic gas located west of the pit crater on Mt. Mihara showed a time variation in chemical and isotopic composition. The cause of the variation seems to be an enhancement of water vapor condensation. No similar variation was observed in the fumarolic gas located east of the pit crater, suggesting the above variation is a phenomena localized around the western fumarole. Hydrogen gas was detected in the sampled gases with low concentration. The change in the H 2 concentration synchronized among the three fumaroles, suggesting the H 2 gas originated in the hydrothermal system developed beneath Mt. Mihara.