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Convective tipping point initiates localization of basaltic fissure eruptions.

Jones, Thomas J. and Llewellin, Edward W. (2021) 'Convective tipping point initiates localization of basaltic fissure eruptions.', Earth and planetary science letters., 553 . p. 116637.

Abstract

Basaltic fissure eruptions may evolve rapidly and unpredictably complicating hazard management. Localization of an elongate fissure to one or more focused vents may take days to months, and depends on fluid dynamic processes, such as thermally-driven viscous fingering, in the sub-volcanic plumbing system. However, fluid dynamics in a dyke geometry are poorly understood. We perform scaled analogue experiments to investigate convective magma exchange flow within a dyke-like conduit, and discover flow regimes ranging from chaotic mingling to stable, well-organized exchange, over the parameter space relevant for natural eruptions. Experiments are scaled via the Grashof number Gr, which is a Reynolds number for buoyancy-driven exchange flows. We propose that chaotic exchange at high Gr hinders thermally-driven localization by suppressing viscous fingering, whereas flow organization at low Gr enhances localization. Consequently, progressive decrease in Gr through increasing magma viscosity or decreasing dyke width pushes a fissure eruption towards a tipping point that results in rapid localization. Our findings indicate that current conceptual models for magma flow in a dyke require revision to account for this convective tipping point, and provide a quantitative framework for understanding the evolution of fissure eruptions.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1016/j.epsl.2020.116637
Publisher statement:© 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Date accepted:14 October 2020
Date deposited:26 November 2020
Date of first online publication:29 October 2020
Date first made open access:26 November 2020

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