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Cristobalite in a rhyolitic lava dome: Evolution of ash hazard

Horwell, CJ; Le Blond, JS; Michnowicz, SAK; Cressey, G


JS Le Blond

SAK Michnowicz

G Cressey


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.


Horwell, C., Le Blond, J., Michnowicz, S., & Cressey, G. (2010). Cristobalite in a rhyolitic lava dome: Evolution of ash hazard. Bulletin of Volcanology, 72(2), 249-253.

Journal Article Type Article
Publication Date Mar 1, 2010
Deposit Date Nov 25, 2010
Journal Bulletin of Volcanology
Print ISSN 0258-8900
Electronic ISSN 1432-0819
Publisher Springer
Peer Reviewed Peer Reviewed
Volume 72
Issue 2
Pages 249-253
Keywords Rhyolite, Dome, Cristobalite, Ash, Health, Hazard, Obsidian.