Sundhnúkagígar Eruption in Iceland, December 2023

Image – Daily Telegraph

The much anticipated eruption on the Reykjanes peninsula began at 17 minutes past 10 on the evening of Monday, December 18th.

The events leading up to this point have been documented on this site in previous blog entries – here is a record of what is known so far about the events of the first days of the new eruption:

The situation is evolving rapidly, with high uncertainty of eventual effects.
The eruption is around 3 km northeast of Grindavík.
The eruption began at 22.17 on December 18^th, following an earthquake swarm (70 in one hour) that began around 21.00.
The eruption started between Sýlingarfell and Hagafell.
This is a fissure eruption.
The eruption appears to be occurring exactly along the old crater line of Sundhnúkagígar (an old fissure) indicating the magma likely exploited this weakness in the crust.
As a first assessment, the fissure was 2800m long. As a comparison, the length of the fissure in the eruption at Litla Hrút in July was about 800 to 900 meters.
By the first morning, the fissure was ~4km long, and growing considerably at both ends.
This is a much larger eruption than previous recent events with lava spreading far into a wide plain.
It is currently (Tuesday) erupting about 150 cubic metres of lava every second.
Already twice as much lava has flowed as came out in the entire last eruption in Litla Hrút, and it has happened in just seven hours.
Lava appears to be flowing from both ends of the fissure – it could flow north towards the Blue Lagoon (and power station) or south towards Grindavik (and the sea).
Vigorous fountaining (150 metres) of the early hours of the eruption was replaced the following morning by a more stable oozing of lava.
Gas emissions (SO2) with a fissure this long could be an issue locally.
All roads anywhere near the eruption area are currently closed. The airport road is showing as closed on travel apps, but is open for essential traffic.
The airport is operating normally, and surrounding settlements are not expected to be affected.
Based on lava flow models, the defence ramparts constructed close to the Blue Lagoon and the Svartsengi power station won’t be tested for the next few hours leaving plenty of time to continue work on them.
One extra challenge is the fact that the eruption is occurring at the worst possible time for remote sensing using solar radiation with UV instruments from ground and space. As we are in the depths of winter there is very little light.
No one is in danger at the moment.
This is not a tourist eruption. Previous recent events were safe (relatively speaking) and easy to view. The new eruption is covering a larger area and will not be as accessible.
What of the future? It is likely that that there will eventually be one crater that takes over and the lava flow will decreases over time. However, the situation is rapidly evolving, and it is hard to say at this stage where the lava might flow.