Interfacial tension-driven relaxation of magma foam: An experimental study

Shizuka Otsuki, Michihiko Nakamura, Satoshi Okumura, Osamu Sasaki

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


To improve our understanding of permeability evolution of magmas in a shallow volcanic conduit, we experimentally investigated the interfacial tension-driven microstructural relaxation of foamed magma. By heating pumice cubes at temperatures of 800-1000°C and ≤6 MPa vapor pressure, we simulated magmas in interexplosion periods of vulcanian activity, including magmatic clasts welding within a shallow conduit. Outlines and internal pore microstructures of run products relaxed significantly in 3-5 and 30 min at 1000 and 900°C, respectively. In addition, self-contraction was caused by the expulsion of pores connected to sample surfaces. As a result of self-contraction, the porosity of 3 mm side pumice cubes decreased from 72 to 15% in 8 h at 900°C. For larger starting materials (9 mm side pumice cubes), multiple-contraction units formed melt globs, which promoted the formation of connected pores with concave outward shapes between globs. In contrast to the interbubble network, such pores are expected to maintain high permeability on a macroscopic scale; therefore, magma outgassing could be facilitated. These interglob pores were pinched off due to gravitational compaction after 8-32 h at 1000°C. The rapid and drastic changes in pore microstructures via relaxation, contraction, and compaction processes may be responsible for vent plugging during vulcanian explosion cycles.

Original languageEnglish
Pages (from-to)7403-7424
Number of pages22
JournalJournal of Geophysical Research: Solid Earth
Issue number11
Publication statusPublished - 2015 Nov


  • interfacial tension
  • magma foam
  • relaxation
  • vulcanian explosion

ASJC Scopus subject areas

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


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