薩摩硫黄島におけるカルデラ形成期以降の噴火史  [in Japanese] Eruptive History of Satsuma Iwo-jima Island, Kikai Caldera, after a 6.5 ka Caldera-forming Eruption  [in Japanese]

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Author(s)

Abstract

Kikai Caldera, 17 km wide and 20 km long, is a Quaternary volcano located, nearly submerged, in the East China Sea, southern Kyushu. Two volcanoes, Iwo-dake (a rhyolitic volcano) and Inamura-dake (a basaltic volcano) on Satsuma Iwo-jima Island at the marginal part of this caldera, were formed after the great caldera-forming eruption of 6.5 ka known as the Akahoya Eruption. We made a geological study to understand the eruptive history of Satsuma Iwo-jima Island after the caldera formation. The volcanic activity in the island after the Akahoya Eruption is divided into three main stages and ten sub-stages based on volcanic edifice development and tephra deposits; the old Iwo-dake stage (stage OIo-I-II), the Inamura-dake stage (stage In-I-IV), and the young Iwo-dake stage (stage YIo-I-IV). The old Iwo-dake stage was initiated by phreatomagmatic eruptions and pumice fallout (stage OIo-I), followed by the effusion of rhyolitic lava with continuous ejection of ash and lithic fragments, resulting in building up an old volcanic edifice (stage OIo-II). In the stage OIo-II, intermittent explosive eruptions also occurred. The Inamura-dake stage is characterized by the effusion of basaltic lava flows and scoria-cone building (stage In-I-II). After that, at the western foot of the cone, phreatomagmatic explosions occurred (stage In-III) and andesitic lava flow effused (stage In-IV). In the young Iwo-dake stage, the explosive eruption occurred at the beginning (stage YIo-I), followed by the effusion of multiple rhyolitic lava flows from the summit crater and the formation of hyaloclastite in shallow sea that made up the marine terrace (stage YIo-II). During the past 1000 years, the volcanic activity changed to intermittent ones with pumice and bomb fallout (stage YIo-III-IV). Total phenocryst contents of the Iwo-dake lavas increased up to 8 vol.% through the young stages. The magma of the young Iwo-dake stage is different from that of the Akahoya Eruption and the old Iwo-dake stage, bordered by the Inamura-dake stage.

Journal

  • BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN

    BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN 50(2), 71-85, 2005

    The Volcanological Society of Japan

References:  28

Cited by:  1

Codes

  • NII Article ID (NAID)
    110003041636
  • NII NACSIS-CAT ID (NCID)
    AN10512786
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    0453-4360
  • NDL Article ID
    7707037
  • NDL Source Classification
    ZM44(科学技術--地球科学--海洋・陸水・火山)
  • NDL Call No.
    Z15-101
  • Data Source
    CJP  CJPref  NDL  NII-ELS  J-STAGE 
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