Posted on by Jón Frímann

Update for Sundhnúkagígar eruption on 20. December 2023 at 18:29 UTC

This is a short update and information here might go outdated quickly and without warning.

This eruption is a short one and that’s how eruptions in Iceland are normally. This eruption might end by Friday to Monday, depending on what happens.

  • The flow from the craters that are erupting is around 10m3/sec. This is low compared to the start of the eruption on Monday 18. December 2023 and suggest that this eruption is going to end soon.
  • GPS data shows that Svartsengi volcano has only lowered around 80mm since Monday. This means there’s a lot of lava in Svartsengi for new eruptions to happen without much warning.
  • Earthquake activity along the fault valley has resumed, after stopping soon after the main eruption took place. This is interesting and I am unclear what this means at the writing of this article.
  • Icelandic Met Office is reporting that the eruption, even is small, is stable at the writing of this article. This can change without warning.
  • The lava field is now, according to best measurements around 3,7 km2 (square kilometres).
  • According to University of Iceland Earth science department, the chemical makeup of the lava shows that its more evolved in part than the lava in Fagradalsfjall volcano. This can be read here (new link, now in English). This means that this magma stopped on its way to the surface and cooled a little and changed chemical makeup before erupting.
  • This new lava is different than the lava that erupted 2400 years ago at the same location. Why that is I don’t know. It is going to take few years to maybe get an answer to this question when the experts have done their research and published their science papers.
Earthquake activity along the rift valley in Svartsengi volcano shown by a green stars, red and orange dots showing smaller earthquakes.
Earthquake activity along the rift valley. Copyright of this image belongs to Icelandic Met Office.

It is interesting to see that Þorbjörn mountain continues to get lower, based on GPS data from today (20. December 2023). Icelandic Met Office has released new danger map and that can be found here in English on Icelandic Met Office website.

This is all the information I know of today (20. December 2023). Next article should be tomorrow (21. December), unless something happens then I’ll try and write article soon as I can.