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The Multiphase Viscosity of Lava: New Insights from Combining Laboratory and Field Measurements

Martin A. Harris 1, Stephan Kolzenburg1 , and Magdalena Oryaëlle Chevrel1,2,3,4,

  • Affiliations: 1Department of Geology, University at Buffalo, 126 Cooke Hall Buffalo, NY 14260-4130, USA 2Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, 63000 Clermont-Ferrand, France. 3Université Paris Cité, Institut de physique du globe de Paris, CNRS, 75005 Paris, France 4Observatoire volcanologique du Piton de la Fournaise, Institut de physique du globe de Paris, 97418 La Plaine des Cafres, France

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 209

  • Programme No: 3.6.13

  • Theme 3 > Session 6

Abstract

Laboratory rheometry on remelted volcanic rocks is the standard technique for measuring lava flow properties. This approach enables precise measurements but struggles to recreate the natural lava emplacement conditions.  Particularly, natural lavas erupt as multiphase suspensions (melt + crystals + bubbles), however, standard laboratory methods cannot retain gas phases, and experiments are limited to two-phase (melt+crystals) suspensions. Furthermore, the oxygen fugacity of lavas is known to influence the kinetics of crystallization, and despite its importance, few studies to date have considered this factor. Currently, the only technique to measure the three-phase rheology of lava is through in-situ measurements while it is flowing. Here we present the first study that integrates viscosity data from laboratory-derived single, and two-phase measurements with three-phase suspension data from field measurements on the 2023 Litli Hrútur eruption in Iceland. We present a multiphase rheological characterization of remelted crystallizing lavas at subliquidus temperatures, and thermal equilibrium, measured at log fO2 of −9.15, and deformation rates relevant to natural processes. We compare these measurements to in-situ field viscosities and find that our values overlap in temperature (1165-1150 ̊C) and viscosity space (2.5-4.5 Log Pa s) across cooling rates of 0.5-1 ̊C/min. We find that equilibrium laboratory measurements recreate comparable crystal volumes to natural samples (~20-50%), yet the associated viscosities are much higher in the laboratory than what was recovered in the field. This comparison allows the first quantification of the effect that bubbles have on reducing the effective viscosity of natural lavas.