Proximal Deposits of the Usu 2000 Eruption(＜Special Section＞The 2000 Eruption of Usu Volcano (3))

• TAKARADA Shinji

  Hokkaido Branch, Geological Survey of Japan

• HOSHIZUMI Hideo

  Volcanic Activity Research Group, Institute of Geoscience, Geological Survey of Japan

• MIYAGI Isoji

  Geodynamics Team, Research Center for Deep Geological Environments, Geological Survey of Japan

• NISHIMURA Yuichi

  Institute of Seismology and Volcanology, Hokkaido University

• MIYABUCHI Yasuo

  Kyushu Research Center, Forestry and Forest Products Research Institute

• MIURA Daisuke

  Geology Dept., Abiko Res. Labo., Central Research Institute of Electric Power Industry

• KAWANABE Yoshihisa

  Volcanic Activity Research Group, Institute of Geoscience, Geological Survey of Japan

Bibliographic Information

Other Title

• 有珠火山2000年噴火の火口近傍堆積物(＜特集＞2000年有珠山噴火 (3))
• 有珠火山2000年噴火の火口近傍堆積物
• ウス カザン 2000ネン フンカ ノ カコウ キンボウ タイセキブツ

Abstract

Events of the March 31, 2000 phreatomagmatic eruption at Usu Volcano can be subdivided into two stages: (1) large-scale black plume stage having 6 major events from 13:07 to 15:28, and (2) relatively small-scale, black plume and jet-type plume stage having 5 major events from 15:28 to 17:07. The total thickness of the March 31 deposit are 100 cm at a site 90 m north from the vent, 9 cm at 550 m NNE from the vent, and 2.5 cm at 1,030 m NE from the vent. The March 31 deposit at the proximal site (90 m north) comprises 10-70 mm thick 20 layers, consisting of sandy coarse 11 layers and sandy to silty matrix-supported 9 layers. The 20 layers at the proximal site can be correlated with each eruption event observed from 13:07 to 17:25 on March 31. In the proximal deposit, essential white pumice ratio is high in the early stage (42%), then the ratio decreases toward the final stage (up to 21%). Essential pumice fragments are white and subrounded, and contain many 0.05-0.2 mm vesicles. The pumice is relatively poorly vesiculated. Grain-size distributions of all layers in the proximal deposit show bimodal distributions, with peaks at -0.5φ to 1φ and 6.5φ to 7.5φ. Poorly-sorted muddy layers are observed in post April 1 deposits. These layers formed during repeated phreatic explosions associated with abundant mud-clast spattering. The proximal area data show that the discharged mass of the March 31 deposit was 2.2×10⁸ kg in total and 1.0×10⁸ kg in the proximal area to 8 mm isopach.

Journal

• BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN

  BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN 47 (5), 645-661, 2002

  The Volcanological Society of Japan

Details

• CRID: 1390001204304604032
• NII Article ID: 10010428817
• NII Article ID: 110003041289
• NII Book ID: AN10512786
• DOI: 10.18940/kazan.47.5_645
• ISSN: 21897182
• ISSN: 04534360
• HANDLE: 2298/36962
• NDL BIB ID: 6398517
• Web Site: https://kumadai.repo.nii.ac.jp/records/29862
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I6398517
• Text Lang: ja
• Data Source:
  • JaLC
  • IRDB
  • NDL
  • CiNii Articles
• Abstract License Flag: Disallowed