On December 18th, 2023, the ground on the Reykjanes Peninsula began rumbling once more. At 10:17 p.m. local time, the night sky near Grindavik lit up as magma that had been moving underground for weeks reached the surface along the Sundhnukagigar Crater Row.
It was the fourth eruption on the Reykjanes Peninsula since 2021, but the first in the Sundhnukur series. The three earlier eruptions had occurred around Fagradalsfjall, while this new activity brought the focus closer to Grindavik.
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The eruption was powerful at first, but its intensity steadily declined over the following days. Scientists remained concerned that new fissures could open, though the activity continued to weaken until the eruption was declared over on December 21st.
The pause was short. In January 2024, another eruption began near Hagafell, even closer to Grindavik. Further eruptions followed throughout 2024 and into 2025, bringing the Sundhnukur series to nine eruptions by August 2025 and the peninsula’s total to 12 since 2021.
Our study of how often volcanoes erupt in Iceland places this repeated activity in a broader historical context. Iceland averages roughly one eruption every four to five years, but eruptions do not follow a schedule, and several can occur close together before a quieter period.
These eruptions have left extensive lava fields across the surrounding landscape. To explore their aftermath, browse the available volcano tours, or take a helicopter tour of the eruption area for a bird’s-eye view of their scale.
- See more about the 2024-2025 Sundhnukagigar Volcanic Eruptions
- Learn about the 2024 Hagafell Volcanic Eruption Near Grindavik
- For more: The Complete Guide to the 2023 Eruption by Litli-Hrutur Volcano
- See also: The Complete Guide to the 2021 Volcanic Eruption by Fagradalsfjall Volcano and the 2022 Fagradalsfjall Volcano Eruption
The Leadup to the Eruption by Grindavik
Just as before the eruptions in Fagradalsfjall in 2021 and 2022 and Litli-Hrutur in 2023, the Reykjanes region had been experiencing an increase in earthquake activity for weeks before but had since quieted down. The seismic activity was caused by a stream of magma flowing beneath the surface, but unlike eruptions in previous years, this one caused real concerns for inhabitants in the area.
Weeks before the eruption, the inhabitants of Grindavik were forced to evacuate the town as magma was discovered flowing only a few hundred feet below the surface of the town.
All inhabitants and animals were safely evacuated, and over the next weeks, many valuables were salvaged from homes. Even though the eruption hadn't started, the seismic activity caused a great deal of damage to the town as cracks formed in the earth, as can be seen in the video above.
The 2023 eruption by Litli-Hrutur
The possibility of an eruption also caused concern for nearby infrastructure. The Svartsengi Power Plant, which provides both power and heat to the entire region, was under threat, as well as Iceland's largest tourist attraction, the Blue Lagoon, which had been closed down as well. Authorities took preventative measures to create defenses for Svartsengi (and, by extension, the Blue Lagoon) by erecting mounds of earth against possible eruption sites to serve as a wall against the flowing lava.
The 2023 Eruption by Grindavik
As the eruption began, all thoughts were with the people of Grindavik. The lava flow of the eruption was significantly higher than the eruptions of recent years in Reykjanes, and the fissure created reached a length of upwards of 2.5 miles (4 kilometers). A Civil Defence emergency level was declared, and police closed down nearby roads.
Thankfully, the eruption turned out to be what experts call a "best-case scenario," as the lava flowed away from the town, the Svartsengi power station, and the Blue Lagoon. Scientists closely monitored the situation to see if the fissure extended further south or if new fissures might open up, but thankfully, the eruption ended, and the people of Grindavik could breathe a sigh of relief.
The eruption began with a bang, with a lava flow ten times more powerful than the eruptions in the peninsula in previous years. The lava field created covered an area of roughly 1.4 square miles (3.7 square kilometers).
The following Sundhnukagigar eruptions were located further away from Grindavik than the Hagafell eruption, but they did manage to damage some infrastructure before dying down.
How long will the Sundhnukagigar craters continue erupting? It's impossible to say, but the Reykjanes peninsula has been very active in recent years, so the Icelandic people and geologists everywhere will be keeping a close eye on the region!
That's it about the relatively short 2023 eruption of Sundhnukagigar! Let us know in the comments below if you have questions, and we will do our best to answer them.
Hi, I’m Arnar Tómas, a storyteller with a background in journalism and content creation. I’ve worked with top Icelandic media and travel organizations, and I’m into fantasy football, pro wrestling, and travel.
