IV. Geological Study

1. Regional Geology and Physical Volcanology

Researches on various aspects of regional geology of Quaternary, Tertiary, and Cretaceous volcanic areas in Japan have been published since the previous report. Regional geological studies of Quaternary volcanoes in Japan were reported for Kutcharo volcano (Hirose and Nakagawa, 1995), Tomuraushi volcano (Ishizaki, 1995), Kuttara volcano (Moriizumi, 1998), Akita-Komagatake volcano (Wachi,1997), Gassan volcano (Nakazato et al., 1996), Numazawa volcano (Yamamoto, 1995), Bandai volcano (Yamamoto and Suto, 1996; Mimura and Endo, 1997), Shirakawa pyroclastic flow (Takahashi and Yoshida, 1996), Nasu volcano (Ban and Takaoka, 1995; Yamamoto,1997), Komochi volcano (Iizuka, 1996), Onoko volcano (Nakamura, 1997), Higashi-Izu monogenetic volcano field (Koyama et al., 1995), Izu-Oshima volcano (Koyama and Hayakawa, 1996), Miyakejima volcano (Tsukui and Suzuki, 1998), Hachijojima volcano (Suga et al.,1997; 1998; Sugihara and Shimada, 1998; Sugihara, 1998), Ontake volcano (Kioka et al., 1998), Kamisano monogenetic volcano (Nomura et al.,1996), Ojika Jima volcanic field (Sudo, et al., 1998), Aso volcano (Ono et al.,1995), Unzen volcano (Ohno et al., 1995), Hohi volcanic area (Kamata,1995), Kuju volcano (Kamata and Kobayashi, 1997), Iki volcanic area (Sano, 1995), and Kaimondake volcano (Fujino and Kobayashi, 1997). Submarine volcanoes were also studied (Watanabe et al., 1995; Yuasa, 1995). Regional geological studies of Tertiary-Cretaceous volcanoes (pre-Quaternaly) were published for calderas (Otake et al.,1997; Miura and Tamai, 1998), Hokkaido (Yahata and Nishido, 1995), NE Japan (Yamamoto, 1996; Ohba and Ban, 1997; Ban et al.,1997), and SW Japan (Matsuura, 1997). For volcanoes in foreign countries, the eruptive history of Pacaya volcano, Guatemala, was studied by Kitamura and Mat_as (1995).

Geologic maps (1:50,000) with explanation including Quaternary volcanic area have been published for Norikura volcano (Nakano et al., 1995), Adatara volcano (Sakaguchi, 1995), debris avalanche deposits from Yatsugatake volcano (Makimoto et al., 1996), Kuju volcano (Kamata, 1997), Pleistocene volcanoes near Beppu (Yoshioka et al., 1997), pyroclastic flow deposits from Narugo volcano and Onikobe caldera (Tsuchiya et al., 1997), Hime Shima volcanic group (Itoh et al., 1997), Aso pyroclastic flow deposits (Okumura et al., 1998), Sambe pyroclastic flow deposits (Kano et al., 1998), and Ontake volcano (Takeuchi et al., 1998).

Various tephrochronological studies in Japan were reported for Quaternary tephras (Furusawa, 1995; Nomura et al., 1995; Ogura et al.,1995; Katoh, et al.,1995; Suzuki et al., 1995; Kobayashi and Koyama, 1996; Saito and The "Crystal Ash" Layers Research Group, 1996; Katoh et al., 1996; Umeda et al., 1996; Hayakawa, 1995b; Sawada et al., 1997; Okajima, et al.,1998; Kitamura et al., 1998), and for Pliocene-Pleistocene tephras (Miura and Kurokawa, 1995; Nagahashi, 1995; Satoguchi, 1995; Arahama Dune Research Group, 1996; Urabe, 1996; Satoguchi et al., 1996; Tomita and Kurokawa, 1997; Satoguchi, 1997; Kurokawa et al., 1998; Aoki and Kurokawa, 1996; Yoshikawa et al.,1996; Watanabe and Danhara, 1996; Kurokawa and Tomita, 1998; Collaborative Research Group for the Northern Japan Alps, 1998; Nakamura and Arai, 1998; Kanto Ash Layers Research Group and Research Group for Geology of the Western Hills of Kanto Plains, 1998). Soil including volcanic soil was studied (Hayakawa, 1995a; Shimozuru, 1995; Yoshinaga, 1995; Suzuki, 1995; Yamanoi, 1996).

Ar-Ar dating has been developed (Uto et al, 1997). A lot of radiametric ages were determined in Japan: K-Ar ages (Uto, 1995; Ishizaki et al., 1995; Hahata, et al., 1995; Saito and Kamei, 1995; Shinmura et al., 1995; Uto et al., 1996; Hoshi et al., 1998; Takahashi and Hoshi, 1995; Sumii et al., 1998; Furuyama et al., 1997; Imaoka et al.,1997; Kaneko and Tiba, 1998; Matsumoto and Ui, 1997; Sawai et al.,1998; Uto and Uchiumi, 1997; Akaishi, 1997; Yoshikawa, 1997; Hayashi and Ohguchi, 1998; Yokose et al.,1998; Uchiumi et al., 1998), 14C ages including AMS methods (Ikeda et al., 1995; Suzuki and Tsukui, 1997; Nakamura et al.,1997; Kobayashi et al., 1997; Miyabuchi and Watanabe, 1997; Okuno et al.,1998), fission-track ages (Ito and Tanaka, 1995; Danhara et al.,1997; Kamata et al.,1998; Suzuki et al., 1998a; Suzuki et al., 1998b), and ESR ages (Toyoda et al., 1995).

Geological researches on recent eruptions were published for the 1991 Pinatubo eruption (Koyaguchi, 1996), the 1996 eruption of Hokkaido-Komagatake volcano (Ui et al., 1997a; Ui et al, 1997b), the 1995-96 Kuju eruption (Hatae et al., 1997), and the 1995 steam explosion at Nakanoyu, Nagano (Miyake and Ossaka, 1998). Volcanic activities during the historical age in Japan were reevaluated by Working group on historical records and others: Towada and Baitoushan volcano (Hayakawa and Koyama, 1998), Iwate volcano (Itoh, 1998), Kampu volcano (Hayashi, 1998), Bandai volcano (Hitahara, 1998), Asama volcano (Tamura and Hayakawa, 1995; Hayakawa and Nakajima, 1998; Aramaki et al., 1998), Fuji volcano (Koyama, 1998a; Koyama, 1998b), Tateyama volcano (Nakano and Itoh, 1998), Kuju volcano (Imura and Kamata, 1996), and Sakurajima volcano (Imura, 1998; Yamashina, 1998). Problems on calendar were discussed (Hayakawa and Koyama, 1997).

Eruption products were studied to reconstruct eruptive sequence: Usu 1977-78 (Yoshida, 1995), Komagatake 1694 (Furukawa et al., 1997), Takahara volcano (Okuno et al., 1997), Asama 1783 (Yasui et al., 1997; Yasui and Koyaguchi, 1998), and Omuroyama (Koyano et al., 1996). Specific researches on volcanic products or activities were published for lava flow and dome (Goto and Fujibayashi, 1995; Nakada et al., 1995a,b; Nakada, 1996; Itoh and Taniguchi, 1996; Goto and McPhie, 1998; Miyamoto and Sasaki, 1998), small-scale eruption products (Imura, 1995; Ono et al., 1995), co-ignimbrite ash (Kamata et al., 1997), pyroclastic flow (Nagahashi et al., 1996; Nagahashi, 1998; Nakayama and Yoshikawa,1995; Nakamae and Nakayama, 1998, Nakamura et al., 1998), reworked volcaniclastics (Nakayama,1997), lahar (Adatara, Yamamoto,1998), debris avalanche and sector collapse (Yoshimoto and Ui, 1998, Suto and Yamamoto, 1997), Near-vent deposit (Kano et al., 1997), pheatomagmatic eruption (Taniguchi, 1996), subaqueous volcanism (Kano et al., 1996; Kano,1996), submarine caldera (Murakami, 1997), Tsunami (Nishimura and Miyaji, 1998), and dikes (Goto and McPhie, 1996; Yatsugatake, Matsumoto, 1997).

Various studies on physical volcanology were reported for eruption columns (Koyaguchi and Woods, 1996), volcanic ash cloud (Sawada, 1996; Arao et al., 1996), vesiculation (Tsukui and Suzuki, 1995; Toramaru, 1995; Toramaru et al., 1996), fluid dynamics (Kobayashi, 1996), melt migration (Ichihara and Ida, 1998), partial melt (Takei, 1998), fissure eruptions and dikes (Tazawa, 1996; Takada, 1997), and physical volcanology in general (Koyaguchi, 1995). Experimental studies on viscosity were carried out (Taniguchi, 1995; Goto et al., 1997). Modeling of magma plumbing system has been developed (Ida, 1995; Takada, 1996; Kaneko and Koyaguchi, 1996; Takahashi, 1997; Yoshida et al., 1997; Takahashi et al.,1997). Tectonic framework for the development of volcanoes was studied for the effect of strain rate on volcanism (Takahashi, 1995), and for tectonic settings of volcanic activity in NE Japan (Hoshi and Takahashi, 1996), in Sakhalin (Takeuchi, 1997), in Hokkaido (Goto et al., 1995; Nakagawa et al., 1995), and in Indonesia (Sunardi and Kimura, 1998). A study on spacing of volcanoes was published (Kondo et al., 1998). Various data on volcanic hazard were compiled by Oshima (1997).

(Akira Takada)

References of geology

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