Bulletin of Volcanology

, Volume 72, Issue 2, pp 249–253 | Cite as

Cristobalite in a rhyolitic lava dome: evolution of ash hazard

  • Claire J. Horwell
  • Jennifer S. Le Blond
  • Sabina A. K. Michnowicz
  • Gordon Cressey
Short Scientific Communication

Abstract

Prolonged and heavy exposure to particles of respirable, crystalline silica-rich volcanic ash could potentially cause chronic, fibrotic disease, such as silicosis, in individuals living in areas of frequent ash fall. Here, we show that the rhyolitic ash erupted from Chaitén volcano, Chile, in its dome-forming phase, contains increased levels of the silica polymorph cristobalite, compared to its initial plinian eruption. Ash erupted during the initial, explosive phase (2–5 May 2008) contained approximately 2 wt.% cristobalite, whereas ash generated after dome growth began (from 21 May 2008) contains 13–19 wt.%. The work suggests that active obsidian domes crystallise substantial quantities of cristobalite on time-scales of days to months, probably through vapour-phase crystallisation on the walls of degassing pathways, rather than through spherulitic growth in glassy obsidian. The ash is fine-grained (9.7–17.7 vol.% <4 µm in diameter, the respirable range) and the particles are mostly angular. Sparse, fibre-like particles were confirmed to be feldspar or glass.

Keywords

Rhyolite Dome Cristobalite Ash Health Hazard Obsidian 

Supplementary material

445_2009_327_MOESM1_ESM.doc (50 kb)
ESM 1(DOC 49.5 kb)

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Claire J. Horwell
    • 1
  • Jennifer S. Le Blond
    • 2
    • 3
  • Sabina A. K. Michnowicz
    • 1
  • Gordon Cressey
    • 3
  1. 1.Institute for Hazard and Risk Research, Department of Earth SciencesDurham University, Science Labs.DurhamUK
  2. 2.Department of GeographyUniversity of CambridgeCambridgeUK
  3. 3.Department of MineralogyNatural History MuseumLondonUK

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