Horwell, C.J. and Hillman, S.E. and Cole, P.D. and Loughlin, S.C. and Llewellin, E.W. and Damby, D.E. and Christopher, T. (2014) 'Controls on variations in cristobalite abundance in ash generated by the Soufrière Hills volcano, Montserrat in the period 1997-2010.', Memoirs., 39 . pp. 399-406.
The Soufrière Hills Volcano (SHV) crystallizes cristobalite (crystalline silica) in its lava domes, and inhalation of cristobalite-rich ash may pose a chronic respiratory hazard. We investigate the causes of variation in cristobalite abundance (measured by X-ray diffraction) in ash from dome collapses, explosions and ash venting from 1997 to 2010. Cristobalite abundance in bulk dome-collapse ash varies between 4 and 23 wt%. During periods of slow lava extrusion (<5 m3 s−1), cristobalite is abundant (7–23 wt%), which we attribute to extensive devitrification in slow-cooling lava; it can also form rapidly (15 wt% in 2 months), but we find no correlation between cristobalite abundance and dome residence time (DRT). By contrast, during rapid extrusion (>5 m3 s−1), cristobalite abundance is low (4–7 wt%, similar to that associated with Vulcanian explosions), and correlates strongly with DRT. We attribute this correlation to progressive vapour-phase mineralization or devitrification, and the lack of contamination by older lava. Cristobalite abundance is expected to be >7 wt% for collapse of slowly extruded lava, for ash venting through a dome or for incorporation of hydrothermally altered edifice during explosions; cristobalite abundance is expected to be <7 wt% for collapse of rapidly extruded lava, for ash venting without dome incorporation and from Vulcanian explosions at SHV.
|Additional Information:||The Eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010. Chapter 21.|
|Full text:||(VoR) Version of Record|
Available under License - Creative Commons Attribution.
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|Publisher Web site:||https://doi.org/10.1144/M39.21|
|Publisher statement:||This article is published under the terms of the CC-BY 3.0 license.|
|Date accepted:||15 February 2013|
|Date deposited:||17 June 2014|
|Date of first online publication:||02 June 2014|
|Date first made open access:||No date available|
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