Reykjanes region has now had four eruptions in three years. On this site, we will collectively be referring to the first three eruptions in and near Mt. Fargradalsfjall as one eruption site as they are located close to each other and their origin from the same line of fissure. The new eruption site by Sundhnúksgígar will be a separate location although the origin and geological event are connected.
The first eruption in Mt. Fagradalsfjall started on March 19th, 2021 at 8:45 (pm) after an increased seismic activity on the Reykjanes peninsula for over a year, dating back to January 2020. The eruption was steady in the valley of Geldingadalir for about 6 months, attracting numerous visitors and was officially declared over in December 2021 after being quiet since September.
An eruption started again in Mt. Fagradalsfjall, in the valley of Meradalir on August 3rd 2022. The fissures opened only 1 km north of the previous eruption site. The eruption lasted up to 3 weeks.
The third eruption in three years started on the 10th of July 2023 at 16:40 and lasted about four weeks, until the 8th of August the same year. The location of the eruption was further inland than the previous ones and led to one of the biggest wildfires in Iceland as the fields of moss caught fire. Because of the wildfires or moss-fires and the fact that the hike to the site was significantly harder, the eruption site was less accessible for visitors than the sites of the previous eruptions.
The eruption by Sundhnúksgígar started at 11 pm on the 18th of December 2023. This event was a bit different from the previous ones as it was developing closer to the town of Grindavík. The Icelandic Meteorological Office had been observing an increase in seismic activity in the area since October 24th, identifying it as a possible precursor to a potential eruption. This seismic activity had already led to the precautionary evacuation of all residents of the nearby town of Grindavík on November 10 to guarantee their safety. The eruption started four weeks after the evacuation. Although the event was bigger than previous eruptions it did not pose an immediate threat to people, and no additional evacuations were necessary. The eruption only lasted for four days.
These events were unusual, compared to the background activity in the area over the last decades.
Periods of rifting and volcanism occur at intervals of 800-1000 years on the Reykjanes Peninsula, alternating with periods of earthquake episodes occurring at intervals of a few tens of years. The latest eruption was the Reykjanes Fires in 1210-1240 AD, where eruptive fissures within both the Reykjanes and the Eldvörp-Svartsengi volcanic systems were active, producing extensive lava flows.
Read more about the eruption: The Icelandic Met Office
Read more about volcanic sites: The Icelandic Environmental Agency