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


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.


Rhyolite Dome Cristobalite Ash Health Hazard Obsidian 



Thanks to Chris Rolfe, University of Cambridge, UK for grain size analyses and Nick Marsh, University of Leicester, UK for XRF analyses. Thanks to all those who were kind enough to supply fresh ash samples so rapidly following eruption. We are grateful to Luis Lara for advice on the Chaitén dome obsidian. Horwell acknowledges a Natural Environment Research Council (NERC) Urgency Grant NE/G001561/1 and a NERC Post-doctoral Fellowship NE/C518081/2. JSL's work is funded by an NERC studentship NER/S/A/2006/14107. Particular thanks to P. Baxter, A. Bernard, G. Plumlee and S. Hillier for useful reviews of the paper before and after submission.

Supplementary material

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


  1. Baxter PJ, Bonadonna C, Dupree R, Hards VL, Kohn SC, Murphy MD, Nichols A, Nicholson RA, Norton G, Searl A, Sparks RSJ, Vickers BP (1999) Cristobalite in volcanic ash of the Soufriere Hills Volcano, Montserrat, British West Indies. Science 283:1142–1145CrossRefGoogle Scholar
  2. Getahun A, Reed MH, Symonds R (1996) Mount St. Augustine volcano fumarole wall rock alteration: mineralogy, zoning, composition and numerical models of its formation process. J Volcanol Geotherm Res 71:73–107CrossRefGoogle Scholar
  3. Hincks TK, Aspinall WP, Baxter PJ, Searl A, Sparks RSJ, Woo G (2006) Long term exposure to respirable volcanic ash on Montserrat: a time series simulation. Bull Volcanol 68:266–284CrossRefGoogle Scholar
  4. Horwell CJ (2007) Grain size analysis of volcanic ash for the rapid assessment of respiratory health hazard. J Environ Monit 9:1107–1115CrossRefGoogle Scholar
  5. Horwell CJ, Baxter PJ (2006) The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bull Volcanol 69:1–24CrossRefGoogle Scholar
  6. Horwell CJ, Sparks RSJ, Brewer TS, Llewellin EW, Williamson BJ (2003) The characterisation of respirable volcanic ash from the Soufriere Hills Volcano, Montserrat, with implications for health hazard. Bull Volcanol 65:346–362CrossRefGoogle Scholar
  7. Le Blond JS, Cressey G, Horwell CJ, Williamson BJ (2009) A rapid method for quantifying single mineral phases in heterogeneous natural dust using X-ray diffraction. Powd Diffr 24:17–23CrossRefGoogle Scholar
  8. Naranjo JA, Stern CR (2004) Holocene tephrochronology of the southernmost part (42°30′-45°S) of the Andean Southern Volcanic Zone. Rev Geol Chile 31:225–240Google Scholar
  9. Reich M, Zúñiga A, Amigo A, Vargas G, Morata D, Palacios C, Parada MA, Garreaud RD (2009) Formation of cristobalite nanofibers during explosive volcanic eruptions. Geology 37:435–438CrossRefGoogle Scholar
  10. Swanson SE, Naney MT, Westrich HR, Eichelberger JC (1989) Crystallization history of Obsidian Dome, Inyo Domes, California. Bull Volcanol 51:161–176CrossRefGoogle Scholar
  11. Watkins J, Manga M, Huber C, Martin M (2009) Diffusion-controlled spherulite growth in obsidian inferred from H2O concentration profiles. Contrib Mineral Petrol 157:163–172CrossRefGoogle Scholar
  12. World Health Organisation (1986) Asbestos and other natural mineral fibres: environmental health criteria 53. World Health Organisation, GenevaGoogle Scholar
  13. Zoltai T (1981) Amphibole asbestos mineralogy. Mineral Soc Am Rev Mineralogy 9A:237–278Google Scholar

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

Personalised recommendations