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. Albert I never watched Neighbours and am Australian so it’s not an issue. Again thanks for updating the current Icelandic action-this site is the only means I have in knowing what’s going on …let the Games begin.

  2. Thanks for keeping the lights on Albert!

    Funny, as one of the (few, I think?) Americans here I just had my holiday for the year; the prior 12 days I’ve been out with my first round of (known) COVID. This new variant hit me pretty hard, but I’m finally on the mend.

    Always been envious of the European august “holiday.” It’s a great concept. I’ve been fortunate enough to spend lots of time in Europe for various reasons, and it’s always come with a healthy respect for how things are done over there.

    Back to the volcano! May it reign for months and without human incident!

    • I hope you have recovered well from Covid. It is a nasty disease, although vaccination has greatly reduced the lethality. I lost two colleagues and one extended family member to it. As for August, it is perfect for France and other more southern locations. For Manchester and further north it is a bit too late as summer tends to end by mid August.

      • Albert, I take 4000IU daily of “vitamin”D3, as do all my family and friends. More here: As an Em Prof in cell biology the failure to use D3 is shocking, and incomprehensible.Peter

        • Good for you. Certainly not a cure for covid but indications are it can reduce the mortality, I expect most for people with a vitamin deficiency. I would not let it replace vaccination, though.

          • I was put on high dose Vit D some years ago and continue to take it as my body appears not to absorb it well, Blood tests showed almost no Vit D in my blood at all. It was only discovered as I was having a lot of balance problems and falls. Since Vit D no balance problems and no Covid despite being with close family members the day before the Covid showed up in their tests. I am though triple jabbed so I think I am lucky to have the ‘Belt AND braces approach.’ Good Vit D levels are essential in preventing Covid but never choose it in place of vaccinations is my advice.

        • What are your thoughts on the current findings regarding the lack of efficacy for Vitamin D in high dose forms.

      • Yes, yes it is. I’ve lost several co-workers as well throughout the last couple years as well as a couple executives as the company I work for.

        And thank you, finally feeling much better.

        I’ve spent two summers in Greece (Evvia and the Cyclades) having dated the daughter of immigrants who had family there. Studied in Firenze for a semester and traveled all over Central Europe. And lately my wife and I have developed a passion for exploring Iceland and have been three times between 2017-2019. Derailed by COVID since, but hoping to be back this October / November. We go for the Aurora hunting and because I’m something of a cold weather / snow hound lately.

        Hoping to visit the UK and perhaps Norway / Sweden / Finland in the coming years. Beautiful places, all.

  3. I do wonder If it woud acually look difftent If it was Nyiragongos lava that erupted in that Iceland Fissure .. ( perhaps it woud ) I guess more gas clouds and perhaps not as bright in glow, perhaps more fluid as well, not soure. But Fagradals 2021 late in the eruption had Nyiragongos viscosity close to the vent

    But Nephelinites are Impossible in Iceland as the melting rates in the Mantle are too large and too shallow in Iceland

    Snafellness are the most alkaline in Iceland and the lowest melting rates ( Althrough only mildly alkaline )

    • Saw Snaefellsjökull up close and it’s a pretty impressively large volcano.

      I gather it’s a very infrequent eruptor throughout the Holocene? More active prior?

  4. If this eruption slows down and become tube feed it have then the capacity of flowing very far indeed because lava is an amazing insulator

    • But To reach that stage, it Will take a long time .. by far No signs of that

  5. I suppose the two big questions now burning in everyone’s minds are:

    1. What is the temperature of the lava at the vent?
    2. What is the lava chemistry? In particular, how similar to last year’s lava from this site?

  6. After seeing the InSAR pictures, the location of the eruption should come as no surprise. Look at the pattern here:

    You have the typical butterfly pattern of a dyke. To the northwest you have a larger area with lots of fringes. Here the ground has moved up and to the northwest, away from the dyke. The satellite is to the west, so there are lots of fringes indicating movement towards the satellite. Then there is a narrow area with fringes indicating movement away from the satellite. This is the dyke. On top of the dyke you get subsidence as the support from the sides is pushed away from the dyke. This is basically a graben. To the southeast there is an area of equal size as to the northwest, but with fewer fringes. Here the ground has been pushed up, towards the satellite, and to the southwest, away from the dyke and the satellite. The result is fewer fringes because of the direction of the satellite, but the actual deformation is symmetric around the dyke.

    Now, look at the center of the fringes indicating the dyke. It’s exactly halfway between Keilir and the coastline. Drawing the same line on a detailed map and looking at the halfway point gives you a point on the slopes of Meradalahnukar towards Fagradalsfjall, within some 100m from the eruption site.

    I actually pointed that out in a facebook comment in another group when the new RUV cam had been set up. It was partly meant as a joke, because that spot would not be visible from that location, but it actually turned out to be spot on.

      • And this is where I say you drew the fissure line too far east…

        Just kidding, it looks good. I checked again using features from the coast line to get a better coordinate mapping and it checks out ok. Note that the fissure line is within 300m from the center of the fringes indicating the graben. I’d say that’s pretty close.

        • It also suggests that if another fissure were to open, it won’t be far from the current one

          • Agree. And just like last year, the fissure is located right north of the main Reykjanes fault, in the fault crumple zone. If the hypothesis holds that the fissure won’t cross the fault, then it won’t open up more to the south. To the north is Meradalahnúkur, so the elevation would have to be a bit higher, unless a parallel fissure opens up, or if it extends all the way to the other side of the hill.

            If it were to open in a new spot, I’d place my bet on a parallel fissure a bit to the northwest.

          • Actually, after watching some aerial footage it seems like the current fissure line wouldn’t have to climb much higher up Meradalahnúkar, it would just follow the side at about the same elevation as the highest part of the fissure already is.


    Good video and page showing how low the viscosity was for Fagradals 2021 .. very low .. I guess its around 10 Pa-s or perhaps acually less. If the lava is really hot then the Sio2 content becomes less important.

    The color on this camera is amazing as well

    This was in late stage of the eruption involving the really hot deep lava

    • My sentiments too, comparing the 1st hour after things got rolling (14:00 local time) to this morning, (15:29 local time next day) it seems like the fountain heights have diminished and the main fountains have become about 3, two on either side of the main fountain area. Maybe it is the shutting down of the either end of the fissure’s fountains which have led to the impression that this eruption is beginning to fade away.

      • Or is it consolidating to more of a cone? I had read that it’s possible the early ends of the long fissure line because occluded by lava and that the fissure could contract through today. Didn’t mention flow rate that I saw.

        Is the flow rate down? I’m definitely not the one to judge that.

        • Good lord that was butchered by my phone randomly correcting words to whatever it wanted. Let’s try this again:

          “I had read that it’s possible the early ends of the long fissure line because occluded by lava and that the fissure could contract through today.”

          Should read:

          I had read the ends of the long fissure line may become occluded by lava and that it may cause the fissure to contract throughout the day.

        • The central area is fountaining higher than before. It has shown the tendency throughout the day. The other area on the fissure are being swamped by their own output. Their flows are beginning to hide behind their own cones. It is hard to tell whether they are diminishing because the lower parts are now hidden. But you would expect the eruption to eventually end up as a single cone.

        • The ends pinching down lead to the impression that the eruption is slowing down, but the same question about cone building has been on my mind too, but the center area seems too fluid to do that yet. Obviously the north end has small spatter cones now. Determining the flow rate needs some scientific measurement, in order to get an accurate value.

          • It is measured by determining the volume of the flow field. It may take a week to get a definite number.

          • The flow has decreased from 32 m2/s yesterday to 18 m2/s this morning according to the latest report from the scientist.

    • It’s odd. And the Langihryggur cam on Rúv is zooming in on smoke in a whole different area!

      • Lobster, that appears to be the moss fire which started several hours prior to the eruption. Stiall a mystery as to what caused it.

      • That moss fire is remarkably persistent. It also covers quite a wide area. I’m wondering if there is a sub-surface heat source that sparked and maintains it.
        I saw the report on it from Iceland news, and they ‘assumed’ it was a normal moss / grass fire but they drew no firm conclusion.
        Time will no doubt tell.

        • there were small patches of moss fires in Gutntog’s latest video. They were all some distance from the eruption but precisely downwind on a very windy day. So I think wind-blown sparks. The one that was before the eruption obviously needed another trigger. Presumably a human one

    • That lava river has broadened considerable since I first watched it 40 minutes ago. Fascinating to watch, Reminds me of last year and all the lava rivers, now we just need some lava bergs to add interest.

      • And just like that I watched a large lava block rolling down a ‘falls’ at the far right of the cam.

  8. Interesting the lava effusion rates nearly halved. The initial pressure must’ve been quite substantial. But it kind’ve make sense considering how fast the lava travelled to the surface since the huge earthquake swarms started

    • Oh brilliant javi! I was wondering for hours since where the lava river was flowing.

  9. We seem to be blessed with cameras this time. On this one you can see just how far the lava has made it into Meradalir already

  10. Did anyone notice there was a very noticable swarm of 70+ shallow earthquakes at Mauna Loa that started yesterday and went into today.

    • Any idea of the significance or otherwise Chacanger? The ERZ eruptions I found fascinating but so far the recent summit lava flows in Hawaia have been of less interest…………. to me personally of course.

      • I tend not to be that interested in Kilauea unless it does something like in 2018, but seeing as it’s Mauna Loa it’s more interesting to me.

        The swarm seems to have trended along a straight line through the caldera and out bot ends where the lava normally flows from it.

      • I agree completely. I had dozens of my stormchaser friends drop everything–in the middle of tornado season–to head to Puna in 2018 because of the eruption style (and the fact it was on private property for the most part.)

        • “I had dozens of my stormchaser friends…” ! ! !

          Damon, in my wildest dreams I cannot imagine making that statement. You hang with a more interesting crowd than I do.

    • Mauna Loa is a monster volcano capable of very fast eruptions involving multiple km3 in a week or so in really large cases I doubt Hilo will last another 100 years

      • I know very little about Mauna Loa outside of basic facts, any specific eruptions I should check out and read about?

          • Thanks Albert. I knew from its location and size that it’s a powerhouse, just not the specifics. Haven’t seen this article though and it’ll be a nice read for me tonight!

          • “Over that time it has covered its slopes with 4 km3 of new lava. But those are just the most recent stirrings. Its older lava flows cover over half of the island of Hawaii.”

            Yup, wow.

          • Mauna Loa and Kilauea are really the summit of basaltic volcanism. Kilauea for the amount of lava it erupts consistently and Mauna Loa for the magnitude of its eruptions. Some eruptions are larger in volume and some are faster, but I cant think of many places that can actually do both on the regular. All of Mauna Loas historical eruptions outside a few summit only events would be at least a VEI 4 if they were explosive…

            Mauna Loa in terms of its true eruption potential is like the worst case combination of Bardarbunga and Nyiragongo, eruptions of Holuhraun scale that occur within a week… Kilauea in 2018 erupted like that and with twice the intensity of Holuhraun and did so with only 700 meters altitude difference, Mauna Loa has nearly 4 km.

    • Thanks for pointing out the swarm Chacanger. I had never seen a swarm like this before. I used to check the monitoring map of Hawaii very often, but it has been some time since the last time, given that there is very little change ever since the last eruption of Kilauea started.

      The swarm seems to involve about 100 earthquakes that took place during the afternoon of August 2 Hawaii Standard Time. This swarm is in the location of volcano-tectonic earthquakes that occur under the summit and upper SWRZ dike swarm, 2-3 km below the surface, and are triggered when the volcano inflates.

      The August 2 event involved deformation seen in the MOK tiltmeter as a sudden small inflation of the summit caldera. Looks like some kind of small magma intrusion, maybe a sill or a minuscule dike. Alternatively it could have been a surge of magma into the volcano, but it seems too fast to be that. The small intrusion will have triggered the faulted and stressed area under the dike swarm, and caused a surge in earthquake activity.

      This could be taken as a sign that Mauna Loa is approaching its breaking point, eruptions are sometimes heralded by intrusions. The last 2 eruptions of Kilauea were both preceded by intrusions. The last eruption occurred after a sill that grew from the summit south-westward. The previous eruption was preceded by a small inclined dike under the southern rim of the caldera. So it is conceivable that an eruption of Mauna Loa is closing in, hard to tell when will happen though,

  11. From via Google Translate.

    The pressure in the magma tunnel under the eruption fissure in Meradälar has not been balanced, but according to geophysicists, this probably means that either the flow will increase from the tunnel or that an eruption can start in a new place. This is stated in a status report from the Public Defender’s Office.

    The Norwegian Meteorological Agency publishes a picture of a large area northeast of the fissure, where there is a risk of new fissures opening.
    Flow has decreased

    As mentioned before, the eruption has decreased somewhat since yesterday. It is now about 100 meters long, but was 300 when it opened.

    The latest lava flow measurements show that the lava flow has decreased, but between 17:00 yesterday and 11:00 this morning, the average lava flow was about 18 cubic meters per second, compared to 32 cubic meters per second in the first hours.

    Aerial photography at 11am this morning showed that the lava covers about 144,000 square meters, or the equivalent of 20 football fields (here, of course, we are considering a 105×68 meter field). The volume at the same time was 1.60 million cubic meters.

  12. It looks like the wind in the area will soon back to SW in the next few hours and then S Friday Morning. It looks like the plume of SO2 could blow over Reykjavik for a little while, although the plume will probably blow more straight N and miss the capital to the W most of Friday. Could the plume be a problem for Reykjavik ?

    • I read a news report yesterday saying that the distance Reykjavik is from the eruption site, it is unlikely that gases will be a problem there.

  13. One timelapse from the Langholl RUV webcamera this morning

    Though always pleased with the results I don’t expect to make these regularly. I was reminded today how much time this takes and occupies my pc.

  14. Large quake but very brief under the eruption site (bit to the north). It will likely be re-assessed but it looks significant

  15. I read that the harmonic tremor is increasing, so the apparent reduction in the flow might be because of impending new breakouts rather than an actual release of pressure in the whole system. The fountains have been taller at times too even through the lake. I think this eruption will be quite bigger than the last, if it was only a small event it would have stopped or significantly slowed by now.

  16. Long time lurker but first time commenter- been following this blog since last year’s Geldingadalir eruption. I’ve learned so much thanks to this site and its contributors, and have been eagerly following along in the leadup to this eruption!

    Also, is it just me or does the fountaining definitely seem to be picking up now on the RUV cam!

    Welcome! And sorry about the long delay in approving your first comment. You commented just after the start of a weekly night of sleep -admin

  17. Yeap it’s cone building time, can make out the coming shape,with spatter falling down on it’s side.Weather been kind for viewing now.

  18. What are your thoughts on the current findings regarding the lack of efficacy for Vitamin D in high dose forms.

  19. This stream looks out over Meradalur up towards Keilir, the lava has already almost reached the other end of the valley and will soon be ponding. I saw somewhere that at the rate of eruption now it will probably overflow in a week or two.

    • Being honest I wasnt actually that convinced the lava would go that far. Last years average was lower but it was episodic so actual episodes had rather high effusion rate, this is pretty constant so far. Evidently though, the lava can flow a long way, several km ina channel on flat ground, the lava field from this eruption could prove to be quite extensive in the end, likely a lot more than last year given no valleys need filling anymore.

    • I see No signs of conduit erosion yet Althrough that may take a week or more If it keeps going in that spot, also the lava is not as fluid and smooth as it was last year, perhaps older stuff thats being pushed out

    • At the moment the lava stream is about 1 km long. It doesn’t seem to be advancing further at the moment but if it does we will need new camera angles.

      • Most likely it has reached the end of Meradalir, a hard stop. Probably it will start spreading noticeably especially at night, but the flow field might not change much until it overflows somewhere. The fountains look to be trying for greater height though, still subdued in the lava lake around the vents but I think we will see some proper fountaining at some point later in the week when the vents can contain themselves a bit 🙂

    • Notice the smoke in the middle centre of the picture. I assume that it is another moss fire, probably started by hikers.

  20. On the Keillir cam, 6.45am – what’s that burning over on the far right?

  21. It was mentioned that this lava has got more volatiles than the eruption last year, it seems it really is a different magma, at least in a relative sense. I think at least part of the reason this lava looks more like a’a in because the rate of eruption is high and goes into a wide shallow lake that lets it cool a bit. If the cone grows up and keeps all of the output focussed to one direction it will probably form a smooth channel. Still very early days, this will probably last for months liek last time, maybe even longer given it seems to be closer to the deep conduit, this place will be unrecognisable in a few weeks 🙂

    • If it holds on to the end of October or early November, my wife and I will be there to see it. We’re finalizing our plans to get back out to Iceland now, and we’re going to be doing the hike out to the area. Of course carefully and with full attention paid to gas emissions / wind / weather.

      To be safe, I’m expecting to see a lava field and not an active eruption. If it holds on that long and I get to see erupting magma, that’s pretty awesome.

      • Depends on two factors really. If the eruption rate is higher then one can imagine a fixed volume would be used up quicker. Last year was slow so lasted a logn time, this might only last 1 month to get the same volume. But last year was not a single fixed volume, it was a direct supply from the mantle at a comparabel rate to the effusion, a supply that that presumably began before the whole thing and never stopped with the eruption. In that case we have an eruption that has got bot hthe high supply rate that was seen last year and an additional almost a year of magma buildup, or at least 8 months of magma build up. 8 months of ~10 m3/s is about 0.2 km3 of potential extra magma.

        So I think this eruption might actually both last longer than last time and also sustain a higher effusion rate for at least the rest of the year and then some. It will overall be a lot bigger than last year. I would also not be surprised if this forms into a proper open conduit and can stay open for much longer, I dont think it will become gigantic but some of the eruptions on Reykjanes in the Middle Ages probably got over 1 km3 and this potentially could to.

        I think though, the chance of this still being active in 2 months are quite good 🙂

  22. Just watching the cam and it looks like the lava stream has gone into a tube.


    • I think it is actually a deep channel that has got a lava boat in it that is partly obstructing the flow. The lava is backing up behind and flowing over the lava boat, and slowly pushing it downstream which is visible if you scroll back a bit.

    • Luis, can you post some URL links to the experts suggesting that other fissures are likely? I would like to read what they say. Also I noticed that small quakes are still occurring on both sides of our current vent, so this might indicate pressure underground?

  23. Taal is inflating once again, with much more substantial steaming, and it should be noted that this is the first inflation signal in almost a year, coinciding with some more deflation. Just looking at the Seismometer at Cerro Negro, I can see an increase of LP and tremor, and the IGEPN is dragging their feet when it comes to releasing the deformation data.

  24. New fissure compared to the vents from last year. It is within the active area of last year but is a different dike, parallel to the first one and pretty close to the one in December although that one went much further south. I think by the time this rift becomes inactive there will be basically vents all along it groing from Natthagi to Keilir and maybe even a bit further north from there. It will not be one eruption though, not in a normal sense, just as there has been a gap up until the other day, so this eruption will end, and maybe in another couple of months another will begin but at a different location. It is also quite likely that new eruptions will take place at the 2021 site, and that maybe as the rifting goes on and becomes more filled with magma dikes will erupt more quickly and with higher intensity. perhaps calling this a ‘minor’ eruptive event on account of last year is being premature, this might be pretty significant if slow to unfold.

  25. Ooh similar magma/lava composition, another eruption that is sourced from the upper mantle. Similar to last years.

    The lava that erupted in Meradälur on the first day of the new eruption has a similar composition to that which erupted last year.
    The concentration of MgO in rapidly cooled glass is about 7.5% and the ratio of K2O/TiO2 is 0.25 (see figure 1).
    The calculated temperature of the magma is 1190-1200 °C and the equilibrium pressure of the dikes in the magma is consistent with the fact that the lava came from a magma passage in the upper part of the earth’s crust (see figure 2).

    A flow of magma from below the mantle in recent months, as indicated by geophysical measurements, may have triggered the eruption. The Institute of Geosciences will regularly collect samples and chemical analyses, which will lead to a much better knowledge of the origin and nature of the magma.

    Figure 1. Variation in the ratio of K2O/TiO2 in the magma that emerged in the eruption in Fagradalsfjall in 2021 together with the same ratio in the first sample from the new eruption. The picture shows that the K2O/TiO2 ratio is almost the same in the new sample as in the sample from the end of the eruption last year

    • Wow is the 1190 C figure the eruption temperatures? I wonder then why the lava flows are not super – smooth and super – low in viscosity, in other words it should as fluid as Hawaii and many other Reykjanes flows appears more fluid than this eruption as well. But fagradalshraun really became super – runny as the eruption progressed to 1240 C

      Somehow Erta Ale looks more smooth at lower temperatures, but coud be the crystal content in this lava as well that makes the current lava a bit rough as 1190 C is not full liquidus temperatures. Holuhraun at 1180 C was full of microlites and explained its rather rough look of the pahoehoe close to the vents

        • I says magma, not lava, and calculated, not measured. (At least, that is in translation.) That suggests it is the temperature in the dike or magma chamber at which crystallization occured. The eruption temperature would be a bit lower.

          • Ok thank you, I’m not an expert. Just fascinated with this stuff. Perhaps from all the lurking and corrections given I can become quite knowledgeable about volcanology in the future

          • There are a lot of different temperatures quoted, and it is not always clear which one is meant. One is indeed the eruption temperature, the temperature at which the lava first reached the surface. It cools as it ascends and decompresses. Another one is the crystallization temperature, the temperature at which the crystals in the magma formed. That takes time and tells you where the magma spend time. (The crystals also tell at what pressure, meaning the depth of the magma chamber). Sometimes you find that the crystals have a coating with a different composition, in which case they formed at one temperature but then spend time at lower temperature (for instance the dike) where the coating condensed on the crystals. In this case, I can’t really tell which temperature was meant but from the fact that they showed crystals and talked about magma and calculation, I figures it was likely the underground temperature. As Jesper mentioned, the lava does not look very hot but that can be hard to judge especially with an eruption on fairly flat ground as here

    • It looks crystal rich and that coud be why it looks rather rough and easly turns into Aa

      1190 C is quite toasty .. thats hotter than most commerical waste To energy incenirators and crematory retorts that runns at 800 to 1100 C

      Did fagradalshraun when it was superrunny last year really erupt at 1240 C ??

    • 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.

  26. A screenshot from the 3d model, I guess based on a fly-over photo. It shows the raised pond and overflows, and the tentative expansion to the north. Most of the lava goes towards Meradalir but it hasn’t expanded the old lava field there yet

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