Bulletin of Volcanology

, Volume 51, Issue 2, pp 115–122 | Cite as

Flow behavior of large-scale pyroclastic flows — Evidence obtained from petrofabric analysis

  • Tadahide Ui
  • Keiko Suzuki-Kamata
  • Rumi Matsusue
  • Kei Fujita
  • Hideya Metsugi
  • Mami Araki
Article

Abstract

The grain orientations within the matrix of two large-scale welded, two small-scale nonwelded and two nonwelded low-aspect ratio pyroclastic flow deposits are measured to analyze flow behavior. Preferred grain alignments are especially apparent in the middle part of layer 2 of each deposit. Preferred grain alignments do not vary laterally within a 10 m interval. The grain alignments obtained are radial from the source caldera, especially in proximal to medial and plateau-forming facies of pyroclastic flow deposits. Grain alignments are controlled by valley-channel directions for the valley-ponded facies of pyroclastic flow deposits, especially at medial to distal locations. Such local topographic factors strongly affect the data for high-aspect ratio and smallscale deposits, and weakly affect the data for widespread low-aspect ratio pyroclastic flow deposits. This work suggests that grain alignment analysis should be used with care when attempting to determine the location of an unknown source.

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Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • Tadahide Ui
    • 1
  • Keiko Suzuki-Kamata
    • 1
  • Rumi Matsusue
    • 1
  • Kei Fujita
    • 1
  • Hideya Metsugi
    • 1
  • Mami Araki
    • 1
  1. 1.Department of Earth Sciences, Faculty of ScienceKobe UniversityKobeJapan
  2. 2.Faculty of EducationKobe UniversityKobeJapan
  3. 3.Nomura Securities Co. Ltd.TokyoJapan
  4. 4.Metal Mining AgencyTokyoJapan

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