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 April 2025, there have been eight eruptions, following an intense series of earthquakes in November 2023. Although localised, the seismic and volcanic activity have 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 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. This led to a loss of hot water supply for several days across the Reykjanes Peninsula. However, the Capital Region 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, 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. Based on current model calculations, the probability of another eruption is projected to increase in the autumn of 2025.