Repeated inflations, deflations, dike injections and eruptions since 2023 in the Svartsengi volcanic system, Reykjanes Peninsula, Iceland

The Svartsengi volcanic system, SW-Iceland, started to show unrest in early 2020 with a series of inflation-deflation cycles. In late October 2023, it started to inflate at unprecedented rate of ~8 mm/day until it produced a ~15 km long dike intrusion on the 10 November 2023. The inflation resumed soon after and has been continuous since, only interrupted by deflation periods concurrent to additional dike injections and associated eruptions at the Sundhnúkur crater row. Geodetic modelling, assuming a deformation source within a uniform elastic half-space, infers pressure changes between about 3-6 km depth, with inflow causing volume increase rates of 3-8 m³/s of a crustal volume inferred to be a magma domain (complex of liquid magma, crystal mush and hot rock).  Displacements mapped by GNSS (Global Navigation Satellite System) geodesy are used to derive volume change estimates of the magma domain in near real-time. Additional geodetic inversions also use extensive interferometric analysis of synthetic aperture (InSAR) satellite images. These results have been used to map the locations and volumes of the intruded dikes and the concurrent contraction volume of the magma domain. Since 27 October 2023, we infer continuous inflow of magma from depth into the magma domain, which appears to continue even during outflow into dikes and the extrusion of lava flows. We analyze all the inflation-deflation cycles, to better understand the mechanisms controlling the activity. The relationship between volume loss of the magma domain during these events and subsequent volume recharged to the domain (before the next event is triggered) has allowed success in forecasting diking/eruption onset in the medium and short term.