Possible runup phase at Fagradalsfjall

The bothersome Fagradalsfjall.

The current swarm at Reykjanes Peninsula that has been going on since the M5.7 NW of Krysuvík on Wednesday at 10.05 declined over the last couple of days. Today it became reinvigorated with 10 earthquakes above M4.

At the same time the earthquake swarm go reinvigorated signals was detected pointing towards movement of volcanic fluids at depth. Currently there have been more than 6000 earthquakes in the swarm.

The larger earthquakes have ranged from 2km NE of Krysuvik to 2km SW of Fagradalsfjall, but todays M4 earthquakes have mainly been at Fagradalsfjall and Keilir, with the bulk at Fagradalsfjall.

A large proportion of today’s large earthquakes (M3+) have been holding steady at depths ranging from 7 to 4.5km with no discernible upwards movement. As such, no eruption is likely to be imminent. This might though change rapidly if steady upwards movement is detected.

Updated image showing a far more interesting low frequency earthquake. The long LF coda indicates movement of volcanic fluids. Image by Icelandic Met Office.

Due to the size of the earthquakes associated with the swarm dykes can rapidly form towards the surface, and magma ascent ratios above 2km per day is possible, with even higher speeds as and if nucleation of volatiles start to set in.

Currently the IMO has not issued a bulletin concerning an upcoming eruption, but the University of Iceland’s Volcanology Department has made a risk assessment that is concurrent with what I wrote earlier today (14.48). There is also an Aviation Colour Code of Yellow in effect for Krysuvik, but I guess this is about to be amended to also include Fagradalsfjall.

It is good to remember that the current unrest is not new, I wrote about it back in 2017, so it is likely that this is a secondary emplacement (the first was very small though).

Unrest at Fagradalsfjall | VolcanoCafe



Volcanic eruption location risk assesment map from the University of Iceland. Image purloined from the University of Iceland, serious thanks for this beautiful map.

Using energy release modelling versus bedrock resilience figures it is quite easy to see that if the current earthquake swarm continues at these energy levels the rifting will become great enough to create dykes that will reach the surface.

Signs to look out for is Volcano-tectonic type earthquakes moving upwards, low frequency tremor bursts, tornillos, and onset of harmonic tremor (likely in that order). So far none of this has been seen except for VT-signals that have remained stationary at depth.

The GPS-trajectories is also showing an intrusion at depth with a hypocenter of 6km slightly NE of Fagradalsfjall, the trajectories is though based on limited datapoints so far. The intrusion is there, but the location could very well be off.

So, what would an upcoming eruption look like if it would occur? Historic data and judging from pre-historic eruptions we can expect something similar with the Krafla Fires. Episodic outbursts of mainly effusive lava fountains and lava flows.

So, if an eruption happens, do not expect something overly big (for being in Iceland), but it could still be a bloody nuisance if it is moving towards Grindavik or other populated places.

This will be updated if and when things progress.


Edit: Post updated with nicer LF earthquake signal image.

Edit 2: Added another one thousand earthquakes to the swarm.

Edit 3: New image with even more interesting coda. I will leave new pictures down here for the time being to give a progression line. This one is yet another LF, this time from KRI-station:

Image from Icelandic Met Office.


195 thoughts on “Possible runup phase at Fagradalsfjall

  1. 16:35:45 63.944 -22.150 0.1 km 5.1 99.0 1.1 km ENE of Keilir

    • Updated: 6:35:46 63.941 -22.152 2.5 km 5.1 99.0 1.0 km E of Keilir

        • What does that mean? A large earthquake, but shallow? What are the usual implications of such?

          I am learning a lot about seismology at the moment.

          • If it is “Wet”, as in consistent with the presence of liqid magma, then a depth of just over 1km represent a rise of about 3000 metres in just one day.
            I’m not any kind of experts, but as I understand it, IF that quake has a magmatic signature, it would mean that an eruption is imminent, as (someone please correct me here) the bouyancy of the fresh magma will drive it upward…. I think.

          • The hypocenter tells the location of the initial break. It is where the earthquake starts.

            In a large earthquake you get movement along a more or less vertical plane. To get a picture of the entire fault, you have to look at the distribution of aftershocks. This is somewhat simplified, but the important thing to remember is that the earthquake extends to both shallow and deep parts of the crust.

            The deepest part of the crack can be filled with magma after the earthquake. This is seen as a low frequency signal. The hypocenter of the large earthquake tells very little about how far up the magma goes. Look at the concentration of M2-3 aftershocks instead to see in which part of the crust the most interesting things are happening.

          • If so many earthquakes are happening, how do you tell which are fresh and which are aftershocks?

  2. Evening news on Icelandic public broadcaster (RUV radio one) just confirmed that movements far beyond what earthquake acitivity can explain (around 30 cm) has been observed in satellite data, most likely explained by a magma intrusion. This is after a meeting of Department of Civil Protection and Emergency Management, meterological office nature hazard chief and other scientists this afternoon.

  3. From IMO: https://www.vedur.is/um-vi/frettir/skjalfti-m57-a-reykjanesi

    The money graph:

    “The Scientific Council also reviewed satellite images (InSAR) received today. Excerpts from those images show more entry than has previously been observed in the area in recent days. The most likely explanation is that magma is forming under the area where the greatest seismic activity has taken place in recent days. This new data will be better processed, for example by means of a model, in order to shed a clearer light on the course of events.”

  4. Possibly more reason to assume an eruption

    Páll Einarsson, professor emeritus of geophysics, said that perhaps more needs to be assumed for a volcanic eruption in the Reykjanes peninsula. A dynamic corridor that stuffs itself into the tectonic plate may be the reason for the prolonged earthquake that has been felt in the area recently. However, he wants to be careful about predicting a volcanic eruption.

    He says new evidence demonstrates that it may be a so-called dynamic that breaks into the lower layers of the fossil record. If so, there might be a higher chance of a volcanic eruption.

    “There are, of course, things that can explain this seismic activity, but humans don’t seem to have such a plausible explanation, we can say. But this changes quickly, of course, and there could be completely different ideas tomorrow.”

    Paul says that in the event of an eruption, it could occur in the middle of the Reykjanes peninsula. He thinks it’s a good idea if he’s going to go to another table.

    “The most likely place for this is in the middle of the peninsula behind Bowling if we look at this from the capital area and this would then be one of the most suitable places for eruptions if it is to erupt on another table,”

    yes, where nobody is?

    “Yes, there’s almost nothing to destroy, at least anytime soon.”

  5. Due to the increased depth of the earthquakes and the GPS-trajectories.

    Me, University and Páll in order:

    In light of InSAR images, earthquakes that have steadily grown more shallow, increased Low Frequency components to geophysical signals and GPS-trajectories indicating inflation, it is possible that there is an increased risk for an eruption at the Reykjanes Peninsula somewhere between Fagradalsfjall and Krysuvik.
    Currently the most likely place for an eruption, IF there will be one, seems to be 2-4 km East of Keilir.
    IF and eruption would occur, it is advisable to be ready with ONE bag of necessities, but the location is likely to such that there is NO to highly LIMITED risk for human life.
    IF an eruption would happen, FOLLOW the advice of the relevant authorities.

    This quote of the University comes from ruv.is:
    The Scientific Council also reviewed satellite images (InSAR) received today. Excerpts from those images show more entry than has previously been observed in the area in recent days. The most likely explanation is that magma is forming under the area where the greatest seismic activity has taken place in recent days. This new data will be better processed, e.g. with modeling to shed more light on developments.

    And Páll Einarsson:

  6. I remember sometime back we held a ‘predict the next Icelandic volcano’. I guess nobody went for Keilir?

  7. And Tumi Gudmundson has weighed in with what might be the least concise Stonetablet of all time:

    “An eruption will occur between 24 hours and 100 years from now”

    • That is a good sign, because its been way more than 100 years since the last eruption there 🙂

      I will be a bit disappointed if there is an eruption but it is a tiny 1 hour spatter cone that you could pick up in a dump truck, and then that is it for the whole thing… but from the looks of things in that area eruptions seem to be of decent size, nothing absurd but it will make for a good show. Might be similar to the Krafla Fires as Jesper says.

    • This depends on someone dressing up as a stonemason, finding a suitable quarry, obtaining the necessary ancient tools and then applying for planning permission, risk assessment, not forgetting ‘elf ‘n’ safety’……then finding out that ‘stonetablet’ has been copyrighted by the Chinese!!

  8. If an eruption was to occur at the that spot near Keilir as some of you here believe, there’s a chance the main highway between Reykjavik and Keflavik (both the town and airport!) could get cut off by lava. Fortunately, there appears to be more than one way between these places

    If you go to Google Maps and switch to satellite mode, you will see a bunch of postglacial (?) lava flows and that highway crosses at least one major flow/lobe which appears to have reached the coast. I have to wonder if these flows erupted during historical times.

    • Be happy that I cannot controll earths volcanism…. perhaps chad knows what woud happen
      I woud unleashed “the flood” : ) with myself becomming the most disliked person on the planet, in that process..

      Anyway I hopes for a Krafla Fires at Reykjanes and that lava goes into the oceans with minior distrubtion, as well as some nice spatter and cinder cones built by tall fountains

      • I actually would go more 0.01-0.03 km3, an eruption of 0.3 km3 would be one of the biggest post Laki eruptions in Iceland, it is as big as the total volume of magma erupted by Grimsvotn in 2011. Krafla Fires was about this much too, but was not one eruption, the biggest single flow in that was about 0.08 km3. Holuhraun really was a massive eruption, its easy to compare it to Laki and call it small, but that is in the same category as calling St Helens small because it wasnt a VEI 8.

  9. Not that things have been too crazy, but so far 2021 has been off to a good start for the volcanically inclined.

  10. Just wanted to share this article and the beautiful satellite picture of Öræfajökull volcano

  11. A brilliant and extremely Icelandic newscast filmed right before magma movement was confirmed.
    Filled with good tips and tricks on how to survive earthquakes and volcanoes. And yes, loads of scenery from the area.

        • Was more likely coined in Italy for Vesuvius or Etna, and put into proper use in Hawaii in the early 20th century. But Iceland right now is probably set for a very good example 🙂

    • Thanks Carl! Icelands
      High Fantasy – J.R.R Tolkien landscapes are totaly insanely beautyful! Ever since a small child, I have wanted to move to Iceland. Reykjanes Penninsula haves insane landscapes. Iceland is a much easier goal than Hawaii is. Im building up my job experiences with taking as many jobs as possible.
      Im also wanting to try, a
      so called ”qualifyed jobexam” ( yrkeshögskola). But I also knows job and housing market in Iceland can be tricky. But I haves the wonderful advantage with the Scandinavian Nordic Partnership.

      Im so tired of northen sweden, that Im almost dying… I was adopted into the wrong country 😉

      I hopes the Blue Lagoon will not be buried in lava now

    • Carl, this is very nice.
      I really enjoyed this.
      I spend the video wondering if he would experience any M5 jolt.
      The newcast is very well made and very Icelandic indeed.

      Its important that he stayed around 3km from the epicenter of activity.
      You can see well how lava would flow over the airport highway road, that links to Reykjavik. That happened in the past.

      However, let us be mindful of 4 different scenarios:
      – EQ swarm continues for at least one more week. Eventually an eruption happens, as it reaches the point of no return. We are progressing in this scenario
      – EQ stops. An intrusion stays in place, as it did in 2019-2020 further west. Another EQ is likely to start further east, probably in Blafjoll, and it could be a big one (and nothing necessarily volcanic). This is the expected eastwards unfolding of tectonic tension, and most likely scenario.
      – Activity might shift eastwards and a swarm starts at Krusuvik. It could lead to an intrusion there (if it then stops), or an eruption.
      – Grey swan. Grimsvotn erupts in the meantime and this swarm continues too. It’s not unlikely to have two eruptions at the same time. Its Covid time, airplanes are mostly not flying. Volcanoes chose wisely this time.

    • I live in the UK, looks like a great place to go hiking.

        • It is very good, but even in summer it can be cold, grey, bleak, wet, and very hostile. I’ve done a lot of mountaineering in different parts of the world and walking off the beaten track in Iceland can be as demanding in its way – especially on kit – as anything I’ve encountered. It’s not a place for waterproofs that aren’t, festival tents, or ignorance about navigation!

  12. There seems to be a slight lull in the earthquakes… thoughts?

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