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Temporal variations in the constituents of volcanic ash and adherent water-soluble components in the Unzen Fugendake eruption during 1990–1991
Earth, Planets and Space volume 53, pages 723–730 (2001)
A change in the chemical compositions of volcanic gases is one of the noticeable phenomena that frequently occurs prior to an eruption. Analysis of the water-soluble components adhering to volcanic ash is available for remote monitoring of volcanic gases from inaccessible volcanoes. It is a secure method for monitoring volcanic activity without using particular devices. Prolonged volcanic eruption at the Unzen Fugendake volcano from 1990 to 1995 started with a phreatic eruption after 198 years of dormancy. Volcanic activity changed from a phreatic and phreatomagmatic eruption to a magmatic eruption with pyroclastic flows in May 1991. The relationship between the chemical composition of volcanic ash and the contents of the water-soluble components adhering to it are discussed in relation to the early stage of the long-term eruption. Volcanic ash ejected by phreatic and phreatomagmatic eruption before dome formation was the product of the alteration in the volcanoclastic materials beneath the surface. The ash had a high content of water-soluble components, which was caused by the absorption of hydrogen chloride and sulfur dioxide gases from magma into wet debris before dome formation. Volcanic ashes which were generated by pyroclastic flows after dome formation were fresh lava fragments. While the contents of water-soluble sulfate adhering to the ash noticeably decreased, those of water-soluble chloride adhering to the ash hardly decreased. The considerable decrease in the contents of water-soluble sulfate was caused by the reaction of volcanic gases with dry lava fragments. Contrary to this, the concentration of hydrogen chloride gas in ash clouds was extremely high, which obstructed the decrease in the water-soluble chloride content in the ash. Volatility of chlorine and sulfur from volcanic rock suggests that the inner temperature of pyroclastic flows was higher than 600∼700°C at least.
Geological party, Joint University Research Group, Geological Report on the 1991 eruption at Unzen Volcano, Bull. Volcanol. Soc. Japan, 37, 47–53, 1992 (in Japanese).
Hirabayashi, J., T. Ohba, M. Yoshida, K. Nogami, K. Uchikawa, J. Ossaka, K. Notsu, and T. Kagiyama, Volcanic activit at Unzen Fugendake and geochemical observation, Report of Grant-in-Aid for Scientific Research (No. 03306009; Ohta, K.) on Research on Prediction for lava extrusion at Unzen Volcano, pp. 99–111, 1992.
Hirabayashi, J., T. Ohba, K. Nogami, and M. Yoshida, Discharge rate of SO2 from Unzen volcano, Kyushu, Japan, Geophys. Res. Lett., 22, 1709–1712, 1995 (in Japanese).
Hirabayashi, J., T. Ohba, and K. Nogami, Chemical monitoring for the volcanic activity, Abst. 1999 Japan Earth and planetary Science Joint Meeting, 1999.
Kagiyama, T., H. Utada, and T. Yamamoto, Magma ascent beneath Unzen Volcano, SW Japan, deduced from the electrical resistivity structure, J. Volcanol. Geotherm. Res., 89, 35–42, 1999.
Mori, T. and K. Notsu, Remote CO, COS, CO2, SO2, HCl detection and temperature estimation of volcanic gas, Geophys. Res. Lett., 24, 2047–2050, 1997.
Mori, T., K. Notsu, Y. Tohjima, and H. Wakita, Remote detection of HCl and SO2 in volcanic gases from Unzen volcano, Japan, Geophys. Res. Lett., 20, 1355–1358, 1993.
Mori, T., K. Notsu, Y. Tohjima, H. Wakita, P. M. Nuccio, and F. Italiano, Remote detection of gas chemistry at Vulcano, Italy, using FT-IR spectral radiometer, E.P.S.L., 134, 219–224, 1995.
Nakada, S. and Y. Motomura, Petrology of the 1991–1995 eruption at Unzen: effusion pulsation and groundmass crystallization, J. Volcanol. Geotherm. Res., 89, 173–196, 1999.
Nakada, S., Y. Motomura, and H. Shimizu, Manner of magma ascent at Unzen Volcano (Japan), Geophys. Res. Lett., 22, 567–570, 1995.
Nakada, S., H. Shimizu, and K. Ohta, Overview of the 1990–1995 eruption at Unzen Volcano, J. Volcanol. Geotherm. Res., 89, 1–22, 1999.
Nogami, K., J. Hirabayashi, T. Ohba, and Y. Yoshiike, The 1997 phreatic eruption of Akita-Yakeyama volcano, northwest Japan: Insight into the hydrothermal processes, Earth Planets Space, 52, 229–236, 2000.
Ohba, T., J. Hirabayashi, and M. Yoshida, Equilibrium temperature and redox state of volcanic gas at Unzen volcano, Japan, J. Volcanol. Geotherm. Res., 60, 263–272, 1994.
Ohta, K., Emission rates of sulfur-dioxide from some volcanoes in Japan, Abst. Kagoshima International Conference on Volcano, 87–88, 1988.
Okita, T. and D. Shimozuru, Remote Sensing Measurements of Mass Flow of Sulfur Dioxide, Bull. Volcanol. Soc. Japan, 19, 151–157, 1975 (in Japanese).
Ono, A., M. Jinguuji, Y. Fujimitsu, and S. Ehara, Remote observation of CO gas using FT-IR at Kuju Iwoyama, Bull. Volcanol. Soc. Japan, 42, 47–51, 1997 (in Japanese).
Ossaka, J., Alteration of rocks in volcanic and hot spring area, Chinetsu, 17, 65–79, 1968 (in Japanese with English abstract).
Ossaka, J. and T. Ozawa, Study on chemical compositions of volcanic gases and volcanic activity at Sakurajima Volcano, Rep. Joint. Ob. Sakurajima Volcano, 62–65 (in Japanese).
Ossaka, J., K. Nogami, and J. Hirabayashi, Water-soluble components on volcanic ashes from Tokachi-dake Volcano, Hokkaido, Japan during the 1988–1989 Eruption, Bull. Volcanol. Soc. Japan, 43, 25–31, 1998 (in Japanese with English abstract).
Taylor, P. S. and R. E. Stoiber, Soluble materials on ash from active Central American Volcanoes, Geol. Soc. Amer. Bull., 84, 1031–1042, 1973.
Watanabe, K., T. Danhara, K. Watanabe, K. Terai, and T. Yamashita, Juvenile volcanic glass erupted before the appearance of the 1991 lava dome, Unzen volcano, Kyushu, Japan, J. Volcanol. Geotherm. Res., 89, 113–121, 1999.
Yamamoto, T., Chemical studies of the volcanic rocks of Unzen district, Bull. Volcanol. Soc. Japan, 5, 69–74, 1960 (in Japanese with English abstract).
Yoshida, M., Chlorine, Fluorine and Sulfur Content in the Volcanic Emanation, Dr. Thesis, Tokyo Inst. Technology, 1962 (in Japanese).
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Nogami, K., Hirabayashi, Ji., Ohba, T. et al. Temporal variations in the constituents of volcanic ash and adherent water-soluble components in the Unzen Fugendake eruption during 1990–1991. Earth Planet Sp 53, 723–730 (2001). https://doi.org/10.1186/BF03352400
- Dome Lava
- Water Leachate
- Dome Formation
- Phreatic Eruption
- Phreatomagmatic Eruption