Volcanic activity of Kusatsu-Shirane volcano, Gunma, and secular change in water quality of crater lake Yugama
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- OSSAKA Joyo
- Faculty of Agriculture, Tamagawa University
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- OSSAKA Tomoko
- Faculty of Science and Technology, Sophia University
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- HIRABAYASHI Jun-ichi
- Kusatsu-Shirane Volcano Observatory, Tokyo Institute of Technology
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- OI Takao
- Faculty of Science and Technology, Sophia University
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- OHBA Takeshi
- Kusatsu-Shirane Volcano Observatory, Tokyo Institute of Technology
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- NOGAMI Kenji
- Kusatsu-Shirane Volcano Observatory, Tokyo Institute of Technology
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- KIKAWADA Yoshikazu
- Faculty of Science and Technology, Sophia University
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- YAMANO Mayumi
- Faculty of Science and Technology, Sophia University
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- YUI Mitsuaki
- Faculty of Science and Technology, Sophia University
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- FUKUHARA Hideki
- Faculty of Science and Technology, Sophia University
Bibliographic Information
- Other Title
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- 群馬県草津白根山火口湖“湯釜”の水質変化と火山活動
- グンマケン クサツ シラネサン カコウコ ユガマ ノ スイシツ ヘンカ ト
- Volcanic activity of Kusatsu-Shirane volcano, Gunma, and secular change in water quality of crater lake Yugama [in Japanese with English abstract]
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Abstract
Geochemical study on Yugama, a crater lake at Kusatsu-Shirane volcano, has been conducted since 1966. Amounts of various cationic species in Yugama water started increasing around 1981, slightly before the phreatic eruptions in 1982-1983, and kept increasing until 1985. In 1986, they turned to decrease and at present restore their former levels before the eruptions. The concentration of sulfate ion showed a secular change similar to those of cationic species, but no such variation was observed for chloride ion even during the 1976 and 1982-1983 eruptions. However, it started increasing in 1989. A high correlation between the concentrations of chloride and hydrogen ions suggests an increasing influx of hydrogen chloride from the deep volcanic systems under the lake. A Cl--SO42- is an excellent monitor of the variation in volcanic activity at Kusatsu-Shirane volcano; all of the three past activities since 1966, i.e., the high-level subsurface activity in 1968, the eruption in 1976 and the eruptions in 1982-1983, showed a reverse secular change with time in the Cl--SO42- plot. This could be attributable to the function of Yugama water as a condenser of volatiles released underground.
Journal
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- Chikyukagaku
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Chikyukagaku 31 (2), 119-128, 1997
The Geochemical Society of Japan
