Update on Fagradalsfjall mountain eruption on 9-July-2021

This is a short update on the eruption in Fagradalsfjall mountain that is part of Krýsuvík-Trölladyngja volcano system (currently, this might change in the future).

  • Since 23:00 UTC on 5-July-2021 the eruption has been on the low side and no lava has been seen leaving the crater when the fog is less dense in the eruption area. This is the longest break in the eruption activity since it started in 19-March-2021.
  • Small amounts of lava has been seen in the crater and it is speculated that it might be flowing from the crater in tubes in the lava field. This remains unconfirmed at the writing of this article.
  • Currently the eruption is not over. It is ongoing as is.

The following is a speculation on my part.

This lack of activity and amount of lava in the crater suggests that the deep system that has been feeding the eruption is for now close to being empty or is completely empty. That system of magma chambers needs time to fill up. This lack of activity is also common for this type of volcano and magma system. Since eruptions go trough a cycles of high and low activity. This might result in the eruption starting in a new fissure in next few weeks to months along with continuing in the current crater. There is also a equal chance of the eruption just continuing in the current crater once the eruption starts at full energy again. But that might be weeks until that happens.

End of speculations

Summer is fog season in Iceland when there is no strong wind and this has been a problem for monitoring the eruption on Reykjanes peninsula in recent days. This is going to continue until September or October depending on the weather pattern.


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22 Replies to “Update on Fagradalsfjall mountain eruption on 9-July-2021”

  1. I am seeing significant lava fountains 1200 hours local time Saturday July 10. I don’t know about lava flows.

  2. It appears that a hole or a crack of some sort has formed at the base of the cone on the northeast side causing a massive flow of lava into Meradalir. This is currently visible on the mbl panorama cam and the IMO still cams are showing probably the largest flow of lava to date into Meradalir. It was a flood earlier today. The YouTube channel “Iceland Volcano Timelapses” posts the IMO stills to the web as timelapse videos.

  3. @George B –well spotted– thanks. Does anyone have the link to the Fagradalsfjall tremor plot?

  4. Thanks, but that link gives me a 404 Not Found error.

    Also, to the extent that one can see anything on the mbl.is panorama camera, I can see the lava leak and flow to Meradalir. I hope we get a new cam to show this side soon.

  5. Make sure you are using HTTP not HTTPS on that link but I do not have any problem clicking on it.

    Also, I now see what looks possibly like a second trail of lava coming from the base of the cone on the east side. I think maybe there is some weakening on the east wall or due to lack of activity it cooled and developed cracks.

  6. All the SIL stations that I know of around Fagradalsfjall mountain can be found on this website I created. It is going to be on this domain until August when I move to its own domain. Since there is no reason for me to keep it on this domain, for technical reasons of my geophone I host this at my own home server.


    1. Is there a way to separate the blue, green and purple graphs? Blue is the only one showing, apparantly it is the last one added, but it covers both the other graphs on the Fagradalsfjall graph.

      1. No. Not with the images that Icelandic Met Office has on the internet. Icelandic Met Office can do the separation of the frequencies with the software that they use but that is not public data.

    2. Thank you for your answer. Another question: is there an explanation for the blue graph shifting between 2500 and 6500 Hz? It looks odd in comparison to green and purple, but also to previous results of blue itself.

      1. The numbers of the left are not Hz. This is I think noise amplification numbers. Lower number means its more quiet, higher number means higher noise in the environment.

        Magma can be seen best on 0.5 – 1Hz. It can also been seen on 1 – 2Hz and 2 – 4Hz. Higher the noise more the activity. What makes it difficult with the eruption in Fagradalsfjall mountain is the drops in activity create a quiet time in the harmonic tremor that instantly goes up again when the eruption starts again. That is why it is so thick on the harmonic tremor image.

      2. Ah, I see, now I understand. Thanks! It is the amplitude of the 2-4 Hz that is very volatile. If it is not the lava something else must cause it. It appears as if green and purple stay in smaller boundaries .

    1. Thanks! Great video, very clarifying with regard to that hole in the bottom of the cone.

  7. Back just over a month ago, I posted this vid showing what looks like lava coming up from the south side of vent #1. Makes me wonder how many other small openings have happened that we have not seen. The earth is cracked in this area of the eruption, so other fissures, or small openings can allow magma to find another way other than the main crater. And of course the main crater being compromised like we see now, allowing magma another route.

  8. I don’t know what has happened to the east side of the crater. Maybe a new crater has opened up or a path from the large crater has formed allow lava to flow down into Meradalir. There might also have been a collapse of the crater on the east side. But it has been difficult to see because of fog.

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