The Fagradalfjall eruption series II – day 2

The end of the Australian TV series Neighbours (which I to my embarrassment never watched) has created room for new home entertainment series. Iceland has stepped into the breech, and has created a serial volcanic eruption. We are now on series II of the Fagradalsfjall fires, just in time for the empty summer holiday schedule. We may find out what happened to that lava surfboard that went missing from the garage of cone number 31 (I am guessing here what a typical Australian plot line might be), or whether that mysterious idiot tourist who climbed an actively erupting cone in series I and barely survived, gives death another chance.

As we are admiring the lava fountains, it can be hard to see what is actually happening. With such a new and sudden eruption, it takes time to understand the details.

The eruption is viewable from the hills around the fissure, safe from the lava but at risk of poor visibility and lack of breathing opportunity if you find yourself downwind. It is important to check the IMO reports which will include the safety recommendation. If they say don’t go, best to listen. In Iceland even in summer the weather can change very fast. So can the eruption, although at the moment the risk of large explosions is small. But in general, this seems to be a tourist-friendly eruption.

Here is an interview with a very excited person who found herself in the right place at the right time.

Acme remains the best site for the eruption viewing. The site collates streams from the main cameras. They are located around the eruption site, so if one is obscured by the fumes, one of the others may have a clear view.

The fissure opened up on the side of a hill at the edge of one the lobes of last year’s eruption. Interestingly, this location showed few earthquakes in the swarm preceding the eruption: those were mainly further east and north. It is however on the line of the intrusion from last December when there was another swarm. That did not end in an eruption (to many people’s disappointment) but it apparently set the trigger for this time. To be fair, an August eruption is far better than a December one in Iceland, when daylight becomes a rarity. The weather will deteriorate later in the year: if you are a keen lava viewer, it may be best to go early.

There were questions about the state of the old lava field. It is a year since that eruption tapered down into extinction. In a year, a few meter of the surface of the lava lake will have solidified. Underneath there will still be a mix of liquid and solid material. Some of the lava is 100 meters deep, and in Meradalir the depth is 50 meters. Expect plenty of lava sitting underneath the crust.

The fissure opened at 13:06 yesterday. The earthquake swarm abated sharply, even 10-20 km away along the Reykjanes fault. This shows that the cause of the swarm was the pressure exerted by the dike. Magma pockets build up around 7km deep along the roughly east-west Reykjanes fault zone. Dikes are thrown up from there running north-northeast to south-southwest, reaching perhaps 10 km (about the distance to Keilir). (Much deeper dikes can also form, at 20km depth, and these can reach much much further but do not reach the surface.) The earthquakes had followed several old fissure lines, and with old we are talking ice age and earlier. That is not where the magma was. My feeling is that these ancient fissures are sitting above equally ancient dikes. The plane of contact between the intruded ancient dike (rock-hard basalt, thoroughly cooled down) and the surrounding rock remains a weakness, and the pressure caused these weakness to break. Thus the purely tectonic events. In the mean time the magma crept upwards very quietly. There was very weak occasional tremor on the seismographs, but not easy to notice. The new magma had arrived on Saturday, evidence by weak earthquakes at depth of 10 km. The new dike traced a region between Keilir and the north end of Fagradalsfjall. The eruption occured at the southern end of that dike. It is not clear whether it used the rift that had been created 7 months earlier but my guess is that it did.

The fissure that opened was about 300 meters long. It has contracted slightly since, possible because the southern end has been covered in lava. Eruption rates are reported at 30 m3/s. For comparison, the eruption last year started out at perhaps 5m3/s and later increased to 10-12m3/s. We are looking at a faster rate. There are various possible explanations. The eruption rate depends on pressure, size of the exit hole, and (yes, Jesper), viscosity. This is probably fresher magma at least compared to the initial phase of last year’s eruption, and the exit is wider as indicated by the fact that the fountain are not that high at the moment. There is quite a bit of gas coming out, but for the numbers we have to wait for IMO.

Here is the map created by commenter Philip Daniels with the approximate location, together with an image of the early fissure.

Map created by Philip Daniels

early fissure

The second map is the model already created for the public (credit: Icelandic Institute Of Natural History).

3-d model

What will happen next? The lava is being injected in a depression, caught between the low shield of Thrainskjoldur to the north and the new Fagradalshraun to the south. Initially the flow went north, filling up the depression. During the night it began to flow over the lava to the south. It will need to add perhaps 20 meters depth before escaping the depression. That may take a few days. The most likely route is south and east, ending up in what is left of Meradalir. But lava can direct itself and the northern route is not impossible. The fissure is likely to contract further, and eventually (if it lasts that long) is likely create a single cone, I guess near the north end of the current fissure. It may also cease, and break through in a different place nearby, as happened last year. How long the eruption will last is anyone’s guess. Given the higher eruption rate, 1-2 months would seem plausible but it could well be much shorter or much longer! (This is not much of a help but predictions are best made in hindsight.)

Map from planetlab basemap. Red is the current fissure, yellow the potential future flow paths – if the eruptions lasts long enough

In the mean time, enjoy the view! Drone footage is not yet available but can’t be far off. For your enjoyment, here is the timelapse of the first 24 hours posted by Virtual. Note the flocking behaviour of the tourists in the background – once one gets close to the lava, the flock follows.

And Gutntog is of course on the ball, day and night

And his report of moss fires, on far side of the old lava field, apparently started by overnight sparks from the lava fountains being blown here

Albert (holding the VC fort and dungeon while the other dragons are on poorly times holidays. I should ask for a raise.)

181 thoughts on “The Fagradalfjall eruption series II – day 2

  1. Perhaps a moderate sized or big shield volcano will be created from this reykanes peninsula eruptive cycle. Only speculation but because this new eruption ended up being so close to the 2021 eruption, there is a possibly that it will add to the old cone with closer fissure popups along dyke or create a big cone of it’s own and is only another part of what will be the distant end result. I’m thinking eruptions will continue taking take place for months or years at a time and continue on and off until all the supply from the upper mantle within this region is depleted. That is if future eruptions keep taking place near the fagradalsfjall area. only time will tell. I just wanted to share a prediction of mine. (Not based on any expert analysis)

    • If lava adds to the other lava field from last year, it’ll be interesting to see if they keep adding it as it’s own or eventually consider it apart of the other lava field and add it to those numbers. After all they consider it a new eruption right now.

    • Ha nevermind lava has already piled on the old lava field. Thanks for that map.

  2. Anak Krakatau, 4 days ago. The red colour is heat – not necessarily lava

  3. Hello all:
    I keep wondering about the fissure volcano eruptions which have started up in the Reyjanes Penisula after 800 years (or so). We have witnessed recently an earthquake swarm which ran from the tip of Iceland, where the rift zone goes into the Atlantic, over to Kleifarvatn Lake. It is obvious from geology that the rift zone has cleved the island into parallel zones. We can see the alignment from current maps of the eruption, and even the newest rift itself is orientated in the same direction.
    My surmisings are this
    1. Did we see an adjustment of the microblocks to the magma dike pressure for this latest eruption?
    2. Should we expect this type of behavior in the future?
    3. If the Keilar segment finally uses up all its lava, can we expect on the other parallel segments to have been recharged and then produce its fissure eruptions.

    What I am alluding to, is that the segments seem to trigger each other, if one segment has a fissure eruption. Do we know the order of this triggering? I think we can expect a 100-200 year period of fissure eruptions once the first one takes off (on the Rekjanes Penisula)

    I keep wondering if anyone has figured out how this part of Iceland behaves?


    • Not quite. The main fault along the peninsula is mostly a transform one, so the north and south move past each other. If you look hard, you can just about see that in the Fagradalsfjall area. The magma collects in pockets along this fault zone which is about 5 km wide. After 800 years, a fair amount of magma may be waiting here, at 15 km depth. Occasionally it finds its way up to 7-8 km depth, which is the bottom of the erupted basalt layers. Now the fault is not pure transform. There is also a bit of extension. It take 800 years for the extension to activate, and provide a low pressure zone for the magma to move up. That activation happens in jumps across the region. I guess we don’t really know how! In this case, the magma is mainly under an area from Grindavik to Krysuvik. Now the rift direction is actually much more northerly. It follows the direction of the mid altlantic ridge. So once magma begins to move up, the direction of least resistance is not along the fault, but along this rift direction. There is no fault here, just rock that gives away more easily as it is being pulled by the two diverging continents. The dike thus extends first almost perpendicular to the Reykjanes fault, and after 1-2 km it turns a bit and runs to north-north east. But every intrusion creates a new dike in a slightly different location. It is likely we will see a series of events, over decades, in this area. After that (or perhaps during that) it may move east or west to adjacent volcanic areas. After an area has erupted, it may stay geothermally active for millennia. Fargradalsfjal has been aloof for much longer, so lacked this activity. Apparently that was no guarantee of future quiescence. So not really parallel segments, but separate dikes taking off at different times.

    • 100-200 years would be massive, but I think it’s within the realm of possibility considering how long it’s been since an eruption tapped this specific area within the Reykanes peninsula. I remember last year after the 1st reattempt of a new intrusion the experts thought it wouldn’t succeed to make it to the surface and that no more intrusions would be making it up to the surface according to models. Many also though it won’t be for the next few years or even decades, especially not near Fagradallsfjall, but instead near kelir or some other part of the Reykanes peninsula. Despite all of this, here we are. An eruption in a surprising spot just under a year later.

      • Therefore I think no one knows how this part of The Reykanes peninsula behaves. Only us living through this cycle will give us and experts such knowledge

    • Randall, did you intend to make your email address public the name field? Dragons, might this need solving?

        • Maybe everyone has breathed to many volanic fumes. Hopefully this doesn’t cause a proble, for Randall!!!

          • Oops, it is late and I am VERY tired! Randall, I hope you are around to amend a possible breach of your privacy!

          • Good thing he didn’t have his password there. I think it isn’t too much of a privacy issue in my opinion, but that’s just me. I cannot speak for Randall.

      • Thank you for pointing this out, I did not intend my email address to be posted, but I have been signing into MS Teams, Google Groups and other places, requiring the email address as the identifier, so I must have thoughtlessly filled this in on the post just before posting.

        Admins, can my email address be replaced with just Randall?

  4. “But if there is still flow from the mantle, then the pressure from below will increase again and the magma will look for another way out. In that case, after a while the rock-breaking earthquakes will restart and the eruption may eventually resume in a new location.

    This may well be the end. It may also be the start of something new.” -Albert July 2021. I must give credit to this analysis because it seems as if the mantle flow never stopped as confirmed by todays magma composition and that the magma built up just enough to trigger another intrusion due to the pressure. Although a last question for me remains, did the mantle flow from the last eruption continue or is this new mantle flow. Either way exceptional analysis that Im thankful to have read while lurking during the last eruption.

    • Hi volcano fan, good to have you aboard. I am an old lady now but have had a very avid interest in volanoes ever since Surtsey first erupted, Hence I have a certain affinity for Icelandic eruptions.
      As to your last remaining question, I have absolutetly no scientific basis for saying this, however my gut feeling is that this is a continuation of the previous eruption. To me it appears as if this is not a new eruption but a continuation of the 2021 eruption which was just waiting for new magma supplies to continue with it’s interupted eruption. I stress that I have no real scientific knowledge of volcanology but I am basing this on commonsense that the new supply of magma is so similar to 2021 erupted magma that it, to my mind, must have a similar supply of magma to drive this new eruption. However, I am happy to be proved wrong if that is the case.

      • Thank you for your thoughts on this. I agree without any conclusions due to my lack of knowledge, but the close proximity to the last eruption along with the similar magma composition is quite indicative to me as well.

  5. From RUV, there is a high chance of more fissures opening on the north side of the eruption, on the other side of the hill and maybe all along the new dike which seems to be quite shallow on much of its 2 km length. Fissures have been seen opening in these areas already although no lava or gas. Pressure has not been relieved by the existing vent, so it seems the eruption as we see it now may be erupting at the deep supply rate or even underperforming.

    • The fissure doesn’t seem to be erupting with as much umph like it has been.

      • I would guess because of the lava flooding. It takes much more pressure to push out the lava. It seems like the thickness of the lava field, especially near the fissure is growing faster than the 2021 eruption. As I remember it got the the point lava and gases had to accumulate to a certain point to push the lava out of the 100 meter plus cone

        • Yes, I think the fountains todayt woudl be much taller if it was not erupting through the lava. I wonder if that might have actually been why last year got so powerful too, because the eruption last year all of the vents began in locations that lava was not prone to accumulate directly around them and flood them, until one of them literally became a mountain of its own and did partly drown itself.
          The lava erupting now is both at a higher rate and apparently also has a higher volatile content relatively speaking compared to the eruption last year (no numbers given on that metric that I have seen though) so one would expect fountains to be more powerful. Even in spite of the now probably almost 15-20 meters of lava depth around the vents some of the fountains do get quite high in short bursts, several tens of meters.

          • I think that too, but also because of the dyke widening over time in last year’s eruption. Maybe both reasons or one or the other due to the effusion rate increase.

          • Sorry I mean causing the effusion rate increase, not due to.

      • Ný Sprunga/Sprungur, new words that I think we have all come to know very well here 🙂

        I think that basically guarantees that an eruption will occur wherever that was now. Last year fissures opened in advance of new vents, and I believe every one of those later erupted quite completely, although it took several weeks to get to the last part. That last part though did end up becoming the main vent of the whole thing…
        It isnt certain but with all the evidence it seems very likely. If an eruption happens on the other side of Meradalanjukur it will flow back to the new lava too, so we might get some significant flow expansion down in the valley and maybe beyond. I think given the rate of accumulation at the vents lava spilling towards the northwest around Fagradalsfjall is looking very likely in time too, although a long lived flow or a tube is more likely to go through Meradalir and to the south after that.

    This is one of my favorite videos of the 2021 Geldingadalir eruption. It shows how fluid that basalt lava became a few months into the eruption: very low viscosity runny. As fluid as Hawaii. If the temperatures are very high over 1200 C then the Sio2 content becomes less important, high temperatures breaks down the Sio2 chains. Its quite possible it was one of the most sillicate fluid lavas ever seen. Basalts this fluid are only produced by oceanic hotspots and mid ocean ridges, with Iceland being a mix of both.

    • The eruption last year looked like this too, it was really only when a single vent and a lava lake formed that the lava began erupting as pahoehoe in large amounts. Also that the lava might be from what didnt erupt in December, and that it is pooled over the vent so will take some time to flush away. Given the situation I would be surprised if this behaves any differently than last year escept possibly for being a lot larger.

    • Thanks. Very interesting, recommended!
      Also the technical bit at the end.
      We are looking at the Meradalir eruption now, together with the 2021 Fagradalsfjall eruption, the (start of?) the Fagradalsfjall Fires.

      • It will be interesting to see how this goes now then. Last year it was not really clear if that was a bit of a singular eruption, it was not ever really a proper fissure and was low rate so hard to compare it to a big rift like Holuhraun or Laki. But it seems that all of these behave the same just on ifferent scales of activity. If the rift is filled from the side as in those eruptions then we can see a caldera form and probably a single big eruption of large volume and relatively long duration, intensity may be variable, but the event is major. If it is from below though, then it has a big initial dike that might erupt or not, and then many smaller dikes that form along it over the duration of the rift, with eruptions being both larger and more powerful as it goes on. Krafla fires is a good example of thos sort of rift, where there is a source located within the rift as opposed to at one end or directly adjacent to it. Reykjanes volcanoes all seem to be like this too, Krafla-type rifts. So last year was slow, and lasted a long time, but that might not necessarily mean every eruption in the area will be the same, some eruptions particularly later in the sequence might be much faster. Still not likely to be a real fissure liek happens at Krysuvik, that requires some sort of magma chamber, but it could get quite impressive as these fires continue, and the magma pathways become well worn and more open.

        Tjadsgigur is growing 🙂

  7. Well, I guess it wouldn’t be an Iceland eruption without camera problems. MBL’s seems to be dead, and RUV’s has flies crawling all over it which seem to have confused its autofocus, so it keeps focusing on the foreground vegetation instead of the vents, which are therefore all blurry.

    I don’t recall insect infestations affecting the cameras before, either here last year or at Holuhraun … maybe they could send a guy over with a can of Deep Woods Off?

    • Yes, the flies are funny. There is nothing wrong with the mbl cameras except for a bit of Icelandic weather – they are in the clouds. Every now and then the fog lifts enough to see some tourists wandering around wondering where the eruption went. It will clear. The cameras can also run out of power at times but that hasn’t happened yet.

  8. The fountaisn are starting to get taler in the middle section of the remaining fissure, while the two vents on the ends seem a bit smaller now than before. Some fountains are probably going up close to 50 meters now, it is trying to go higher but the lake is drowning the vents. That lake must be at least 15-20 meters deep now.

  9. Very strange signal coming from the HAU SiL.
    Not sure if I’ve ever seen anything like it before? The “quakes” appear eerily similar in magnitude and duration but still are different enough to suggest discrete events are occuring. I thought at first it was periodic “shocks” coming from the eruption, but other SiL’s aren’t showing the same pattern (such as FAL in the second image)
    I wonder if there’s a weird data glitch…or maybe ice-quakes?

    • Often when you see odd waveforms it’s passing traffic, especially when the same waveforms are repeated with a reversed shape like this (returning traffic). We saw similar waveforms on the FAF drumplot last year when they drove a jeep to service the equipment. It was obvious then, because we saw the vehicles on the webcam at the same time as the signals were observed on the drumplot.

      • Perhaps….but the wave patterns do not follow a steady rise and fall in intensity as if a vehicle was moving closer then away from the SiL station. Many of the signals have near “dead” moments similar to the typical lull between between P and S wave arrival times. To me, this indicates a shock of some type? Maybe there is a nearby pothole or other nearby road obstruction that vehicles are impacting?

  10. Some extremely clever people on this blog predicting the site of eruption to within a half-mile or so.
    It’s quite lively isn’t it, certainly more reminiscent of Holuhraun at the moment than last year.
    I feel as though this one will be more short-lived, and repeat in a year or two.
    Still beautiful as ever, especially the night cams.

  11. I’m travelling to some Greek islands next week so I shall resume my article shortly about a certain Dodecanese volcanic system that was abandoned in the lockdown era. And take some beautiful pictures. I have even just discovered there is an ancient (probably extinct) volcano just 43 miles from where I’ll be staying, last dated 700ka, part of a Miocene volcanic arc. Glorious.

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