Effects of gas escape and crystallization on the complexity of conduit flow dynamics during lava dome eruptions

T. Kozono, T. Koyaguchi

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

We investigated the coupled effects of gas escape and crystallization on the dynamics of lava dome eruptions using a one-dimensional conduit flow model. The relationship between chamber pressure pch and mass flow rate q for steady conduit flow commonly has a regime of negative differential resistance (i.e., dpch/dq < 0), which causes a transition from lava dome to explosive eruption. Two positive-feedback mechanisms that result in negative differential resistance have been identified. First, effective magma viscosity decreases with increasing q because of a delay of crystallization, leading to reduced viscous wall friction (feedback 1). Second, magma porosity increases with increasing q because of less efficient gas escape, leading to reduced gravitational load (feedback 2). For high-phenocryst-content magma (volume fraction >0.5), feedback 1 is the main mechanism that forms negative differential resistance. In this case, the transition from lava dome to explosive eruption occurs when the magma supply rate exceeds a fixed critical value. For low-phenocryst-content magma (volume fraction <0.5), feedback 2 plays a key role so that the transition is controlled by the permeability of the surrounding rocks; the critical magma supply rate remarkably decreases with decreasing permeability. Transition due to feedback 2 is associated with a change in the chemical composition of volcanic gas, a drastic increase in magma porosity from nearly 0 to greater than 0.8, and overpressure at a shallower level, which can be detected from geochemical and geophysical field observations.

Original languageEnglish
Article numberB08204
JournalJournal of Geophysical Research: Solid Earth
Volume117
Issue number8
DOIs
Publication statusPublished - 2012 Aug 1
Externally publishedYes

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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