University of Cambridge > Talks.cam > Department of Earth Sciences Seminars (downtown) > Walking on broken glass: investigating magmatic processes in explosive and effusive rhyolitic eruptions

Walking on broken glass: investigating magmatic processes in explosive and effusive rhyolitic eruptions

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Eruptions of rhyolite magma occur fairly infrequently, but their hazardous nature is clear from the abundant and widely dispersed deposits they produce. Examples such as Novarupta 1912 are among the largest historic eruptions and Earth’s largest supervolcanoes such as Toba, Yellowstone and Taupo are invariably rhyolite producers. There is even rhyolitic ash scattered over much of northern Britain from Holocene Icelandic eruptions. Rhyolitic melt is initially volatile-rich and the highly viscous melt hinders gas escape, yet initially-explosive eruptions somehow produce large volumes of degassed lava. The mysterious explosive-effusive transition is one of many aspects of rhyolitic volcanism that have long remained poorly constrained, partly due to a lack of observed eruptions. However, two recent rhyolitic events in Chile – Chaitén (2008) and Cordon Caulle (2011-2012) – have provided unprecedented insights into eruption dynamics.

In this seminar I will describe ongoing research into the degassing, crystallisation and deformation of rhyolitic magma, using experimental, geochemical and field approaches. I will also report some of the latest findings from Chile, including observations of synchronous explosive and effusive eruptions that call the notion of an explosive-effusive transition into question, and the first measurements of how active obsidian flows advance.

Eichelberger, J.C., Carrigan, C.R.,Westrich, H.R.,Price, R.H., 1986. Non-explosive silicic volcanism. Nature 323, 598-602.

Castro, J.M., Cordonnier, B., Tuffen, H., Tobin, M., Puskar, L., Martin, M.C., Bechtel, B., (2012) Defusing explosive rhyolite eruptions by melt-fracture degassing. Earth and Planetary Science Letters, 333-334, 63-69.

Gonnermann, H.M., Manga, M., 2003. Explosive volcanism may not be an inevitable consequence of magma fragmentation. Nature 426, 432-435.

This talk is part of the Department of Earth Sciences Seminars (downtown) series.

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