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

Danilo Di Genova (1, 2, 3) , Richard A Brooker (2) , Heidy M Mader (2) , James W E Drewitt (2) , Alessandro Longo (4, 5) , Joachim Deubener (1) , Daniel R. Neuville (6) , Sara Fanara (7) , Olga Shebanova , Simone Anzellini , Fabio Arzilli , Emily C Bamber (8) , Louis Hennet (9) , Giuseppe La Spina (8) , Nobuyoshi Miyajima (3)

1 TU Clausthal - Clausthal University of Technology
2 University of Bristol [Bristol]
3 Universität Bayreuth
4 ESRF - European Synchrotron Radiation Facility
5 CNR-ISMN - Institute for Nanostructured Materials
6 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
7 Georg-August-University = Georg-August-Universität Göttingen
8 University of Manchester [Manchester]
9 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation

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.

Domaines: Volcanologie

Danilo Di Genova, Richard A Brooker, Heidy M Mader, James W E Drewitt, Alessandro Longo, et al.. In situ observation of nanolite growth in volcanic melt: A driving force for explosive eruptions. Science Advances , 2020, 6 (39), pp.eabb0413. ⟨10.1126/sciadv.abb0413⟩. ⟨hal-02989553⟩