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The compressibility of the Svartsengi magma domain: lessons learned from comparison of volumes of inflation-deflation and volumes of dikes and lavas during the Sundhnúkur crater row rifting episode 2023 to present

Freysteinn Sigmundsson1, Michelle Parks2, Vincent Drouin2, Halldór Geirsson1, Gro B. M. Pedersen2, Benedikt Ófeigsson2, Simon W. Matthews1, Sæmundur A. Halldórsson1, Eniko Bali1, Magnús T. Gudmundsson1, Joaquin M. C. Belart3, Birgir V. Óskarsson3, Sydney R. Gunnarsson3, Tom  Winder1, Andrew Hooper4, Chiara Lanzi2, Yilin Yang1, Sonja H. M. Greiner1, Ásta Rut Hjartardóttir2, Páll Einarsson1

  • Affiliations: 1Nordic Volcanological Center, Institute and Faculty of Earth Sciences, University of Iceland, Reykjavik, Iceland; 2Icelandic Meteorological Office, Reykjavik, Iceland; 3Natural Science Institute of Iceland, Urriðaholtsstræti 6-8, 210 Garðabær, Iceland; 4COMET, School of Earth and Environment, University of Leeds, UK. 

  • Presentation type: Talk [Invited]

  • Presentation time: Thursday 15:45 - 16:00, Room R380

  • Programme No: 1.8.6

  • Theme 1 > Session 8

Abstract

Rifting events at the Sundhnúkur crater row, Iceland, beginning in 2023, have drained magma from a magma domain at ~4-5 km depth, where magma accumulates between events. Geodetic observations and modelling give information on deflation source volume contraction, as well as volumes of dikes (~156 Mm3 and ~182 Mm3 at end of 2024, respectively). Volume of eruptive products (lavas) mapped by photogrammetry is ~217 Mm3 at end of 2024. Constraints on the compressibility of the magma domain comes from the ratio between volume change of the deflation source and the DRE volume of the extracted material. Assuming DRE volume of lava extruded during deflation is 0.8 of measured total lava volume and geodetically imaged dike volume corresponds to DRE volume, we preliminary infer the ratio to be in the range 1.3-4.2, comparable to that reported in studies of basaltic systems. The ratio depends on the shape of the magma domain, the shear modules of host rock and the compressibility of material in the domain. If the domain is approximated as an horizontal spheroid with horizontal semiaxes of 4 km and 1.5 km, half-thickness of 1.5 km, and crustal shear modulus is 10 GPa, then the inferred compressibility of material in the domain is ~0.03 - 0.3 GPa−1. Compressibility of the erupted basaltic magma at depth inferred from petrochemical analysis is within this range, showing the difference in volume change of the magma domain and volume of extruded material and dikes can be explained by the effects of magma domain compressibility.