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Magma fragmentation in highly explosive basaltic eruptions induced by rapid crystallization

DOI: 10.1038/s41561-019-0468-6 DOI Help

Authors: Fabio Arzilli (University of Manchester) , Giuseppe La Spina (University of Manchester) , Mike R. Burton (University of Manchester) , Margherita Polacci (University of Manchester) , Nolwenn Le Gall (University College London) , Margaret E. Hartley (University of Manchester) , Danilo Di Genova (Clausthal University of Technology) , Biao Cai (University of Birmingham) , Nghia T. Vo (Diamond Light Source) , Emily C. Bamber (University of Manchester) , Sara Nonni (Diamond Light Source) , Robert Atwood (Diamond Light Source) , Edward W. Llewellin (Durham University) , Richard A. Brooker (University of Bristol) , Heidy M. Mader (University of Bristol) , Peter D. Lee (University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Geoscience , VOL 397

State: Published (Approved)
Published: October 2019
Diamond Proposal Number(s): 16188

Abstract: Basaltic eruptions are the most common form of volcanism on Earth and planetary bodies. The low viscosity of basaltic magmas inhibits fragmentation, which favours effusive and lava-fountaining activity, yet highly explosive, hazardous basaltic eruptions occur. The processes that promote fragmentation of basaltic magma remain unclear and are subject to debate. Here we used a numerical conduit model to show that a rapid magma ascent during explosive eruptions produces a large undercooling. In situ experiments revealed that undercooling drives exceptionally rapid (in minutes) crystallization, which induces a step change in viscosity that triggers magma fragmentation. The experimentally produced textures are consistent with basaltic Plinian eruption products. We applied a numerical model to investigate basaltic magma fragmentation over a wide parameter space and found that all basaltic volcanoes have the potential to produce highly explosive eruptions. The critical requirements are initial magma temperatures lower than 1,100 °C to reach a syn-eruptive crystal content of over 30 vol%, and thus a magma viscosity around 105 Pa s, which our results suggest is the minimum viscosity required for the fragmentation of fast ascending basaltic magmas. These temperature, crystal content and viscosity requirements reveal how typically effusive basaltic volcanoes can produce unexpected highly explosive and hazardous eruptions.

Journal Keywords: Petrology; Volcanology

Subject Areas: Earth Science


Instruments: I12-JEEP: Joint Engineering, Environmental and Processing

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