Update 23rd December 2023

IMO have confirmed that the eruption has ended. However, since uplift resumed immediately at Svartsengi after the onset of the eruption and is at a higher rate than that which preceded the eruption, magma is still accumulating under Svartsengi and the risk of further eruptions increases daily. The rate of uplift decreased prior to the eruption; this process is thought likely to be repeated. The most likely site for another eruption is thought to be between Stóra-Skógfell and Hagafell.

A new hazard assessment has been issued by IMO. It can be found here: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night . The purple zones (very high risk) over the magma intrusion have been lowered to red (high risk); all other zones remain the same. The hazard level for Grindavík remains considerable. Conditions can change rapidly and adverse weather can hinder detection, reducing warning time.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night

Update 21st December 2023

At risk of jinxing it, the eruption appears to be over. Activity decreased late last night / early this morning. Scientists who viewed the site from the air today report that there is no visible activity in the craters and the lava flow appears to have ceased. It is, however, feasible that lava is flowing in closed channels. It would be premature to declare the eruption over. Scientists continue to monitor the area. Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Update 20th December 2023

IMO are reporting that the eruption remains steady today. The authorities are concerned that the eruption started with considerable force after only an hour from the start of the latest episode in the seismic swarm. Magma is most likely sourced from Svartsengi, which has had several periods of inflation since 2020, although the eruption started on the magma intrusion which formed on 10th November 2023. The current level of activity is comparable to recent eruptions at Fagradalsfjall.

A new risk assessment has been carried out. Seismic activity has remained fairly steady, following the initially intense swarm, and ground deformation has not changed significantly to date (or not as much as during the formation of the November magma intrusion). The risk of a new eruptive site forming near Grindavík is thought to have decreased but the risk still remains substantial. Magma can reach the surface quickly, not giving the authorities much time to issue warmings. The most likely sites for new activity remain over the November magma intrusion. A new hazard map has been created.

Scientists collected lava samples on 19th December 2023. Their analysis shows a composition of c.6% Mg₂O, c.2.29% TiO2 with a K₂O/TiO₂ ration of 0.23. The lava is thought to be more evolved than the lavas erupted at Fagradalsfjall, having spent more time in the crust. It may have the same source as the recent Fagradalsfjall eruptions. (Source: https://jardvis.hi.is/is/eldgos-vid-sundhnuksgiga-nidurstodur-maelinga-18-desember).

Armchair Volcanologist

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Update 19th December 2023, 16:30 (video issues corrected)

The lava flow has decreased and is now about 25% of the initial output.

The Coast Guard reports that the eruption is now mainly in two places on the fissure and a small vent in the south. The larger sites are each c. 300 metres to 500 metres long. The southernmost site is c. 2 kilometres north of Sundhnúk. There is also a very small site north east of Stóra-Skógsfell.

Magma plumes are also smaller, reaching about 30 meters at their highest point. Lava is currently flowing eastwards towards Fagradalsfjall, with two smaller flows heading westward, both north of Stóra-Skógfell.

The eruption is currently following a similar pattern to recent volcanic eruptions at Fagradalsfjall, where the fissures have started to contract and form single vents.

We have updated our earthquake plots. These are in the video below. 

Armchair Volcanologist

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Original Post, 19th December 2023

This evening an intense earthquake swarm started c. 20:40 local time, north of Grindavík, following the path of the recent magma intrusion.  This heralded the eruption which started just after 10:00pm. The eruption is located close to Sundhnúkagígar, about four kilometres northeast of Grindavík. At the time of writing, the aviation code is orange.

The local authorities are evacuating Grindavík and Reykjanesbraut (the road which connects Reykjavik to the airport). A civil defence emergency has been declared. This is not a tourist eruption.

The eruption is powerful, with jets reaching hundreds of metres high. The initial fissure was 200m to 300m long, with a lava flow of 100 to 200 cubic metres per second. The fissure has now reached c. 3.5km length. There is a risk that lava may reach Grindavík.

Prior to the eruption, inflation at Svartsengi had reached 10th November 2023 levels prior to the formation of the graben and magma intrusion.

For updates, please consult the relevant authorities, for example, IMO and Department of Civil Protection and Emergency Management

We will update our earthquake plots as soon as we get a chance.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Sources are referred to in the text and also https://www.ruv.is/english/2023-12-18-eruption-on-reykjanes-peninsula-399922