2023–2025 Sundhnúkur eruptions

The 2023–2025 Sundhnúkur eruptions (Icelandic: Eldgosin við Sundhnúksgíga 2023–2025) are a series of volcanic eruptions on the Reykjanes Peninsula, near the town of Grindavík, Iceland. Between December 2023 and August 2025, there have been nine eruptions, following an intense series of earthquakes in November 2023. Although localised, the seismic and volcanic activity has caused significant disruption across the western part of the peninsula, especially for the town of Grindavík. However, the Capital Region, including Reykjavík, has remained physically unaffected. The eruptions were preceded by an intense earthquake swarm in the Eldvörp–Svartsengi volcanic system that began on 24 October 2023, caused by a magmatic intrusion underneath the area. The frequency and intensity of the earthquakes dramatically increased on 10 November 2023, with around 20,000 tremors recorded by that time, the largest of which exceeded magnitude 5.3. Grindavík was subsequently evacuated due to the creation of large-scale subsidence, including the formation of an extensive graben valley, which caused significant damage. This extensional tectonic activity likely altered magma pathways and triggered subsequent eruptions.

The volcanic eruption series at the Sundhnúksgígar crater chain began on 18 December 2023, with an initial eruption that lasted for three days. This eruption was preceded by land uplift in the Svartsengi area, which subsequently deflated upon eruption, indicating the accumulation of magma at a depth of 4–5 km (2.5–3.1 mi) beneath Svartsengi. This magma source fed the initial eruption as well as all subsequent eruptions in the series. The second eruption occurred on 14 January 2024, lasting approximately two days. This event had a fissure opening less than 100 m (330 ft) from a nearby town. The eruption breached anti-lava defences and destroyed three homes. Additionally, the eruption formed a new graben, although it was substantially less extensive than the one formed in November 2023. Tragically, just before this eruption, one person was reported missing and presumed to have fallen into a crack caused by seismic activity, resulting in their death. On 8 February 2024, the third eruption caused extensive damage, including the disruption of a hot-water pipeline from the Svartsengi power station. Although the eruption lasted only about two days, it resulted in a loss of hot water supply for several days across the Reykjanes Peninsula. The Capital Region, however, remained unaffected. The fourth eruption started on 16 March 2024 and became the longest in the series, spanning 54 days. A magmatic intrusion had occurred earlier in the month but did not reach the surface. The fifth eruption, which began on 29 May 2024, continued for 24 days. This eruption caused damage to power lines and cut off several road sections. On 22 August 2024, the sixth eruption commenced, lasting 14 days. It released 61 million m³ (2.2 billion cu ft) of lava, covering an area of 15.8 km² (6.1 sq mi) and resulting in 40 cm (16 in) of land subsidence. Despite being the largest eruption in the series so far, it did not cause any infrastructure damage. The seventh eruption began on 20 November 2024 and extended over 18 days. It quickly engulfed the parking lot of the Blue Lagoon and threatened protective barriers in the area. The eighth eruption commenced on 1 April 2025 and concluded approximately seven hours later the same day, marking the shortest and least intense event in the eruptive series to date. In the days following the eruption, a substantial magmatic dike intruded underground without breaching the surface. The ninth eruption of the series commenced on 16 July 2025 and persisted for roughly 20 days. While it posed no threat to infrastructure, the gas pollution spread unusually far during the eruption’s early stages and the measured pollution levels in nearby towns and cities were higher than those typically observed during the previous eruptions in the series.

Land uplift has resumed since the last eruption and is ongoing, with the current rate of vertical ground deformation lower than that observed before the previous eruption, although magmatic inflow into the magma chamber remains steady. Since March 2024, each eruption has been preceded by the accumulation of roughly 17–23 million m³ (600–810 million cu ft) of magma in the reservoir. By the end of November 2025, the interval since the previous eruption had become the longest recorded within the eruptive sequence that began in November 2023, exceeding 115 days since the conclusion of the July–August 2025 eruption. Currently, the volume of magma beneath the area has reached more than 23 million m³ (810 million cu ft), representing the highest threshold observed in the eruptive series to date. The Icelandic Meteorological Office considers a new magmatic intrusion to be more likely than not to occur, which may culminate in a volcanic eruption.