2025 diking events and eruptions within the Svartsengi volcanic system, Iceland.

During 2025, volcanic activity continued within the Svartsengi volcanic system on Reykjanes Peninsula, Iceland, with diking events and eruptions on 1 April and 16 July 2025. The dike intrusion on the 1 April 2025 was the second largest thus far, with a estimated length of ~20 km and intruded volume of about 100 million cubic meters. The concurrent volume drop within the magma domain was ~35 million cubic meters. The eruption itself however was short lived, lasting only 7 hours and producing a very small lava field (0.3 million cubic meters). It is proposed that the eruption ended because less energy was required for the magma to intrude laterally within the crust than to erupt, because of 'un-released tectonic stress' stored in the crust, despite 9 earlier diking events in the area. The April dike continued propagating for at least 10 hours, based on continuing deformation and seismicity, propagating laterally both to the SW (beneath the town of Grindavík, as occurred previously during November 2023 and in January 2024) and the NE. The dike propagation on 16 July was a smaller intrusion, with a median length of 3.5 km and volume change of ~16 million cubic meters. The volume drop within the magma domain was ~12 million cubic meters. The eruption continued until the 5 August and produced a lava field of ~31 million cubic meters.

Between November 2023 and July 2025 there have been 11 dike intrusions and 9 eruptions within the Sundhnúkur crater row and its extension. Despite the wealth of data and high frequency of events, eruption forecasting remains challenging. Since 16 March 2024, observations indicate that the volume required to trigger a new diking event/eruption has changed compared to previous events. For the last five events, the modelled volume recharged to the reservoir has been between 17-23 million cubic meters.

This presentation will provide an overview of the diking events and eruptions to date within the Svartsengi volcanic system and an update on the forecasting methodologies used thus far for medium-term eruption forecasting and future implications.