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Outgassing through magmatic fractures enables effusive eruption of silicic magma

Research output: Contribution to Journal/MagazineJournal articlepeer-review

E-pub ahead of print
  • Josh Crozier
  • Samantha Tramontano
  • Pablo Forte
  • Sarah Jaye C. Oliva
  • Helge M. Gonnermann
  • Einat Lev
  • Michael Manga
  • Madison Myers
  • Erika Rader
  • Philipp Ruprecht
  • Hugh Tuffen
  • Rebecca Paisley
  • Bruce F. Houghton
  • Thomas Shea
  • C. Ian Schipper
  • Jonathan M. Castro
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Article number107617
<mark>Journal publication date</mark>31/10/2022
<mark>Journal</mark>Journal of Volcanology and Geothermal Research
Volume430
Number of pages20
Publication StatusE-pub ahead of print
Early online date14/07/22
<mark>Original language</mark>English

Abstract

Several mechanisms have been proposed to allow highly viscous silicic magma to outgas efficiently enough to erupt effusively. There is increasing evidence that challenges the classic foam-collapse model in which gas escapes through permeable bubble networks, and instead suggests that magmatic fracturing and/or accompanying localized fragmentation and welding within the conduit play an important role in outgassing. The 2011–2012 eruption at Cordón Caulle volcano, Chile, provides direct observations of the role of magmatic fractures. This eruption exhibited a months-long hybrid phase, in which rhyolitic lava extrusion was accompanied by vigorous gas-and-tephra venting through fractures in the lava dome surface. Some of these fractures were preserved as tuffisites (tephra-filled veins) in erupted lava and bombs. We integrate constraints from petrologic analyses of erupted products and video analyses of gas-and-tephra venting to construct a model for magma ascent in a conduit. The one-dimensional, two-phase, steady-state model considers outgassing through deforming permeable bubble networks, magmatic fractures, and adjacent wall rock. Simulations for a range of plausible magma ascent conditions indicate that the eruption of low-porosity lava observed at Cordón Caulle volcano occurs because of significant gas flux through fracture networks in the upper conduit. This modeling emphasizes the important role that outgassing through magmatic fractures plays in sustaining effusive or hybrid eruptions of silicic magma and in facilitating explosive-effusive transitions.