Magma fragmentation in highly explosive basaltic eruptions induced by rapid crystallization

Arzilli, Fabio; Spina, Giuseppe La; Burton, Mike; Polacci, Margherita; Gall, Nolwenn Le; Hartley, Margaret E.; Genova, Danilo Di; Cai, Biao; Vo, Nghia T.; Bamber, Emily C.; Nonni, Sara; Atwood, Robert C.; Llewellin, Edward W.; Brooker, Richard A.; Mader, Heidy M; Lee, Peter

doi:10.1038/s41561-019-0468-6

Cited by 104 publications

(100 citation statements)

References 68 publications

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“…Fast magma ascent and high undercooling (∆T) is crucial to produce rapid syn-eruptive crystallization within the conduit where fragmentation occurs (41). Therefore, in situ investigation of nanolite formation at realistic time scales (the first few hundreds of seconds of cooling and with a time scale resolution on the order of milliseconds) would allow structural observation of the incipient dynamics of nucleation.…”

Section: Introductionmentioning

confidence: 99%

In situ observation of nanolite growth in volcanic melt: A driving force for explosive eruptions

et al. 2020

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Although gas exsolution is a major driving force behind explosive volcanic eruptions, viscosity is critical in controlling the escape of bubbles and switching between explosive and effusive behavior. Temperature and composition control melt viscosity, but crystallization above a critical volume (>30 volume %) can lock up the magma, triggering an explosion. Here, we present an alternative to this well-established paradigm by showing how an unexpectedly small volume of nano-sized crystals can cause a disproportionate increase in magma viscosity. Our in situ observations on a basaltic melt, rheological measurements in an analog system, and modeling demonstrate how just a few volume % of nanolites results in a marked increase in viscosity above the critical value needed for explosive fragmentation, even for a low-viscosity melt. Images of nanolites from low-viscosity explosive eruptions and an experimentally produced basaltic pumice show syn-eruptive growth, possibly nucleating a high bubble number density.

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Section: Introductionmentioning

confidence: 99%

In situ observation of nanolite growth in volcanic melt: A driving force for explosive eruptions

et al. 2020

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“…Houghton et al 2004]. The associated increase in melt viscosity will inhibit bubble expansion and promote rapid ascent and explosive fragmentation [Arzilli et al 2019;Costantini et al 2010;Szramek 2016]. However, the Fur ashes show relatively low crystallinities, with small fractions of both phenocrysts and microlites (Figure 9).…”

Section: Morphological and Textural Evidencementioning

confidence: 99%

“…In contrast, the low viscosities of silica-poor basaltic melts do not sufficiently restrict bubble growth and instead enable gas-melt separation and non-explosive degassing of exsolved volatiles [Cashman and Scheu 2015;Mangan and Cashman 1996]. Sub-Plinian and Plinian eruptions of basaltic magmas are therefore rare, and those that are known have largely been attributed to rapid ascent and syn-eruptive crystallisation of hydrous basalts, and the associated increase in magma viscosity [Arzilli et al 2019;Costantini et al 2010;Houghton et al 2004;Sable et al 2006;Walker et al 1984;Williams 1983]. Critically, these rheological constraints imply that the tholeiitic basaltic ash layers in the positive ash serieswhich we show below are largely crystal-free-likely reflect a type and scale of explosive basaltic eruption not observed in the historical record.…”

Section: Introductionmentioning

confidence: 99%

Evidence of explosive hydromagmatic eruptions during the emplacement of the North Atlantic Igneous Province

2020

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Early Eocene sediments in northwest Denmark contain over 180 well-preserved volcanic ash layers, likely sourced from the North Atlantic Igneous Province (NAIP) between 56.0 and 54.6 Ma. Most of these ashes are basaltic, widespread, and represent a phase of unusually large and explosive eruptions that is coincident with the opening of the northeast Atlantic Ocean. Explosive basaltic eruptions of this magnitude are unheard of in historical times and in the current geological record. Here, we combine analyses of glass sulfur concentrations and variations in the morphology and vesicularity of pristine volcanic glass grains to explore the possible eruptive processes promoting such widespread basaltic ash dispersal. We suggest that these ashes formed in shallow subaqueous environments (<200 m water depth) where they fragmented and rapidly quenched during explosive hydromagmatic activity. We speculate that magma-water interaction during the opening of the northeast Atlantic Ocean was the main cause of this unusual explosive basaltic activity.

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“…Areas within volcanology where real-time in situ synchrotron X-ray tomography could prove transformative include (but are not limited to) bubble nucleation, growth, and coalescence; crystallization; crystal alignment and physiochemical interaction; multiphase magma deformation and rheology (including strain localization reactive transport, and fragmentation); magma-rock-fluid interaction; rock mechanics; etc. Work has now begun in some of these areas, such as bubble growth and permeability (Baker et al, 2012(Baker et al, , 2019Colombier et al, 2018;Pleše et al, 2018), gas driven filter pressing (Pistone et al, 2015), deformation (Okumura et al, 2013), sintering (Wadsworth et al, 2016(Wadsworth et al, , 2019, and crystallization (Polacci et al, 2018;Arzilli et al, 2019).…”

Section: Recent Applications To Volcanologymentioning

confidence: 99%

Quantifying Microstructural Evolution in Moving Magma

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Many of the grand challenges in volcanic and magmatic research are focused on understanding the dynamics of highly heterogeneous systems and the critical conditions that enable magmas to move or eruptions to initiate. From the formation and development of magma reservoirs, through propagation and arrest of magma, to the conditions in the conduit, gas escape, eruption dynamics, and beyond into the environmental impacts of that eruption, we are trying to define how processes occur, their rates and timings, and their causes and consequences. However, we are usually unable to observe the processes directly. Here we give a short synopsis of the new capabilities and highlight the potential insights that in situ observation can provide. We present the XRheo and Pele furnace experimental apparatus and analytical toolkit for the in situ X-ray tomography-based quantification of magmatic microstructural evolution during rheological testing. We present the first 3D data showing the evolving textural heterogeneity within a shearing magma, highlighting the dynamic changes to microstructure that occur from the initiation of shear, and the variability of the microstructural response to that shear as deformation progresses. The particular shear experiments highlighted here focus on the effect of shear on bubble coalescence with a view to shedding light on both magma transport and fragmentation processes. The XRheo system is intended to help us understand the microstructural controls on the complex and non-Newtonian evolution of magma rheology, and is therefore

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Magma fragmentation in highly explosive basaltic eruptions induced by rapid crystallization

Cited by 104 publications

References 68 publications

In situ observation of nanolite growth in volcanic melt: A driving force for explosive eruptions

In situ observation of nanolite growth in volcanic melt: A driving force for explosive eruptions

Evidence of explosive hydromagmatic eruptions during the emplacement of the North Atlantic Igneous Province

Quantifying Microstructural Evolution in Moving Magma

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