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A rheological map of Mauna Loa Basalts

Stephan. Kolzenburg 1, Martin. A. Harris1, M. Oryaelle. Chevrel1,2,3,4 Kendra. J. Lynn5

  • 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 5 U.S. Geological Survey, Hawaiian Volcano Observatory, 1266 Kamehameha Avenue, Suite A-8 Hilo, HI 96720, United States

  • Presentation type: Poster

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

  • Poster Board Number: 213

  • Programme No: 3.6.17

  • Theme 3 > Session 6

Abstract

Rheological data are crucial to modeling the storage, transport, eruption, and emplacement of magma and lava. Magma and lava transport processes generally occur at subliquidus conditions, where the melts crystallize, and at lower than atmospheric oxygen fugacities (fO2). Yet, the effect of oxygen fugacity on sub-liquidus rheology remains largely uncharted. Surprisingly, to date, there are no direct rheological measurements for Mauna Loa, the largest active volcano on Earth. We present the first complete rheological characterization of Mauna Loa lava, based on samples from its latest eruption in 2022. We map its rheology across the solidification interval at both oxidized (in air) and reduced (log fO2=-8.7) conditions. These measurements constrain the pure liquid viscosity and map the lava's rheology during crystallization in both thermal equilibrium and at cooling rates between 0.25 and 3.00 C/minute. We find that for Mauna Loa the solidification interval is significantly narrower than for Icelandic and Etnean basalts. In respect to oxidized conditions, we observe that at reduced conditions: 1) the onset of crystallization is delayed in both time and temperature, 2) crystallization is suppressed by up to 50 °C, 3) the crystallization kinetics are slower, 4) the composition of the crystallized phases changes, 5) the volume fraction of crystals decreases and, with that, the effective suspension viscosity decreases as well. The resulting rheological map constrains the minimum and maximum effective lava viscosity applicable to Mauna Loa lavas and can help guide physical property based lava emplacement models that aid in eruption response and hazard assessments.