An analog experiment of magma fragmentation: Behavior of rapidly decompressed starch sirup

Hiroaki Yamamoto, Kazuyoshi Takayama, Valeri Kedrinskii

Research output: Contribution to journalArticlepeer-review


Paper reports a result of analog experiments regarding the simulation of magma fragmentation. We filled a starch sirup foam, as an analog material, in a 117-240 mm long and a 50 mm diameter high pressure chamber and exposed it to a rapid decompression. The foam was prepared by mixing starch sirups of dynamic viscosities ranging from 5 to 10 12 Pa• s at temperatures ranging from 293 to 343 K with nitrogen at 2.5 MPa gauge pressure. In ejecting high-pressure foams into a low-pressure chamber, diagnostics of foam's fragmentation process were pressure measurment and high-speed video recording. Prior to decompression experiments, we examined visco-elastic properties of foam specimens by using a rheometer. The foam deformation under decompression was found to be axial-symmetrical, and strongly coupled with bubble growth and coalescence. These effects contributed even more efficiently to fragmentation processes than previous laboratory experiments using other analog materials. Fragment shapes varied widely depending on the temperature and water concentration of starch sirup foams, which proved that fragmentation process was governed by not only ductile deformation but also brittle failure, and determined by the degree of visco-elasticities of starch sirup foams.

Original languageEnglish
Pages (from-to)371-385
Number of pages15
JournalShock Waves
Issue number6
Publication statusPublished - 2008 May 1


  • Analog experiment
  • Magma fragmentation
  • Rapid decompression
  • Starch sirup
  • Visco-elastic material
  • Volcanic explosion

ASJC Scopus subject areas

  • Mechanical Engineering
  • Physics and Astronomy(all)


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