Effects of relative motion between gas and liquid on 1-dimensional steady flow in silicic volcanic conduits: 2. Origin of diversity of eruption styles

Tomofumi Kozono, Takehiro Koyaguchi

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

We investigate the origin of diversity of eruption styles in silicic volcanoes on the basis of a 1-dimensional steady conduit flow model that considers vertical relative motion between gas and liquid (i.e., vertical gas escape). The relationship between the assemblage of steady-state solutions in the conduit flow model and magma properties or geological conditions is expressed by a regime map in the parameter space of the ratio of liquid-wall friction force to liquid-gas interaction force (non-dimensional number ε), and a normalized conduit length Λ. The regime map developed in the companion paper shows that when ε is smaller than a critical value εcr, a solution of explosive eruption exists for a wide range of Λ, whereas an effusive solution exists only when Λ ~ 1. On the other hand, when ε > εcr, an effusive solution exists for a wide range of Λ. Diversity of eruption styles observed in nature is explained by the change in ε accompanied by the change in magma viscosity during magma ascent. As magma ascends, the magma viscosity increases because of gas exsolution and crystallization, leading to the increase in ε. For the viscosity of hydrous silicic magma at magma chamber, ε is estimated to be smaller than εcr, indicating that an explosive solution exists for wide ranges of geological parameters. When magma flow rate is small, the viscosity of silicic magma drastically increases because of extensive crystallization at a shallow level in the conduit. In this case, ε can be greater than εcr; as a result, a stable effusive solution co-exists with an explosive solution.

Original languageEnglish
Pages (from-to)37-49
Number of pages13
JournalJournal of Volcanology and Geothermal Research
Volume180
Issue number1
DOIs
Publication statusPublished - 2009 Feb 20
Externally publishedYes

Keywords

  • conduit flow model
  • diversity of eruption styles
  • silicic volcanism
  • vertical gas escape

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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