We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK


97% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > The role of melt-fracture degassing in defusing...
View graph of relations

« Back

The role of melt-fracture degassing in defusing explosive rhyolite eruptions at volcán Chaitén

Research output: Contribution to journalJournal article


  • Jonathan M. Castro
  • Benoit Cordonnier
  • Hugh Tuffen
  • Mark Tobin
  • Liljana Puskar
  • Michael C. Martin
  • Hans Bechtel
<mark>Journal publication date</mark>17/04/2012
<mark>Journal</mark>Earth and Planetary Science Letters
Number of pages7
<mark>Original language</mark>English


Explosive volcanic eruptions of silcic magma often evolve towards non-explosive emissions of lava. The mechanisms underlying this transition remain unclear, however, a widely cited idea holds that shear-induced magma fragmentation plays a critical role by fostering volatile loss from fragmentary magma and through ash-filled cracks termed tuffisite. We test this hypothesis by measuring H2O concentrations within glassy tuffisite from the 2008- rhyolitic eruption at volcán Chaitén, Chile. We show that while H2O concentrations decrease next to tuffisite veins and at the margins of obsidian fragments, the depletions cannot account for the disparity in H2O between explosively and effusively erupted rhyolite. Tuffisite vein lifetimes derived from diffusion modeling (min to hrs) imply degassing rates that are too slow to effectively degas magma, unless the magma was entirely fragmented to mm or smaller particles. This level of brecciation may locally develop near conduit margins, but is unrealistic for entire conduits. The primary role of melt fracturing may therefore be to provide gas-escape pathways for more efficient degassing of permeable vesicular
magma in the conduit interior.