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Combined effusive-explosive silicic volcanism straddles the multiphase viscous-to-brittle transition.

Wadsworth, Fabian B. and Witcher, Taylor and Vossen, Caron E. J. and Hess, Kai-Uwe and Unwin, Holly E. and Scheu, Bettina and Castro, Jonathan M. and Dingwell, Donald B. (2018) 'Combined effusive-explosive silicic volcanism straddles the multiphase viscous-to-brittle transition.', Nature communications., 9 (1). p. 4696.


Magma is a viscoelastic fluid that can support fracture propagation when local shear stresses are high, or relax and flow when shear stresses are low. Here we present experiments to confirm this using synthetic and natural magmatic liquids across eruptive conditions and use Maxwell’s linear viscoelasticity to parameterize our results and predict the maximum stresses that can be supported during flow. This model proves universal across a large range of liquid compositions, temperatures, crystallinity and rates of strain relevant to shallow crustal magma ascent. Our results predict that the 2008 Volcán Chaitén eruption resided in the viscous field at the onset of magma ascent, but transitioned to a mixed viscous-brittle regime during degassing, coincident with the observed combined effusive-explosive behaviour during dome extrusion. Taking a realistic maximum effusive ascent rate, we propose that silicic eruptions on Earth may straddle the viscous-to-brittle transition by the time they reach the surface.

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Publisher statement:Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit
Date accepted:11 October 2018
Date deposited:22 November 2018
Date of first online publication:08 November 2018
Date first made open access:22 November 2018

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