The Happy Dyke of Fagradalsfjall

/ 14/03/2021

Dalssel at Fagradalsfjall. Image from Ferlir.is

Background

The good part about volcanology is that nature will sooner or later test both your theories and your scientific models. In this case what was tested was the original model of the available pent up seismic strain in the currently active area of Reykjanes Peninsula in Iceland.

It turned out that the amount of pent-up strain was higher than the models had given at hand. Science loves when oddballs like this comes around the corner, then you get the opportunity to see if something is wrong or missing with your theories, or if there is something wrong with the models used. I love the smell of science in the morning.

As everyone has noticed by now, well at least everyone interested in Icelandic geology, the seismic activity continued well beyond what could be expected according to the model for the area. Since the start of the seismic crisis an average of 20 000 earthquakes has occurred per week, and the size of the larger earthquakes are comparatively in the same range without any sign of them abating.

During the first week of seismic activity, we mainly saw tectonic earthquakes along the portion where the Mid Atlantic Rift enters the Reykjanes Peninsula in a WSW/ENE-direction spanning most of the peninsula.

After that the activity started to concentrate in an area between Keilid and Fagradalsfjall, with a migrating trend towards the southern part of Fagradalsfjall.

At this point in time this is the largest earthquake swarm recorded instrumentally in Iceland. It is in fact so numerous in earthquakes that it stands for a large portion of all earthquakes ever measured in Iceland. It even dwarfs the famously noisy eruption of Holuhraun in 2014-2015.

 

Tectonic or Magmatic?

Dykemap, courtesy of the Icelandic Met Office.

One of the most irrelevant questions in Iceland is probably if an intense earthquake swarm is tectonic or volcanic. The reason I am saying this is that sooner or later an initially purely tectonic swarm will turn into a magmatic swarm as intrusions sets in.

Here I am talking about earthquake swarms that are not directly in or around the well known large central volcanoes, they operate a bit differently. I am here keeping to areas like the Reykjanes Peninsula.

The reason for this is simple fluid dynamics. The main tectonic regiment in Iceland is caused by the rifting apart of the Eurasian and North American continents. This is by no means a constant process, instead you get increased strain locally, and that strain is later released as an earthquake swarm (or as a large earthquake, but now we are talking about swarms).

The swarm in turn is in the beginning tectonic as things are pulled apart, and here it is where fluid dynamics comes into action. I will here invoke a rule, nature abhors a vacuum. So, if a void is formed in the crust as it is pulled apart two things will happen.

Scenario number one is the purely tectonic one, and the rift will snap back together giving no dilation of the rift. In other words, the vacuum problem is solved by the sides of the rift coming back together (most often not exactly in the same way).

I am obviously simplifying things quite a bit here, but the principle is correct. In these cases, you might get lateral slip or vertical slip of one edge, but you do not see dilation. This is quite easy to see a few days later on the GPS-network.

The second option happens if the swarm is ongoing for some time and the crust is fractured enough that magma can enter from below. In this scenario you will instead be having fresh magma being sucked into the void, filling it up.

Now we have dilation that will be visible on the GPS system if we are in the happy situation that we have a GPS-station on either side of the rift as the earthquake(s) strike. It is visible since the stations will move apart, and then they stay apart.

The important part here is that it is quite common that this happens in Iceland, it usually happens a couple of times per year, or even more. After all, most intrusions will fail before an eruption occurs since the intruding magma is just enough to fill up that pesky void in the crust.

 

The Happy Dilating Dyke

Cumulative seismic release over 11 days. Image by Gaz Dale based on data from the Icelandic Met Office.

Now things will become a tad technical, so I need to explain a few expressions as I go. The first one is obviously the word dyke. It is a form of volcanic conduit that is extending from the mantle upwards like a hanging sheet of magma, sometimes spanning a considerable horizontal distance.

It forms like I explained above as the rift is pulled apart by the continental drift, the ensuing void will be filled by magma. If the magma moves far enough upwards it will start to exert force in two ways.

The first way is through buoyancy, due to being hotter than the surrounding bedrock it will buoyant and will strive to move upwards like a hot balloon. If the magma is shallow an eruption might happen since there is not enough time for the magma to solidify in the dyke.

This is a fairly slow process, and it can be followed since the earthquakes will be slowly migrating upwards.

The other force will kick in if the magma comes close enough to the surface. All magma contains volatile compounds like water and gasses. In Iceland there is comparatively little water in the mixture, but there is quite a bit of gas that can nucleate out of the magma.

Cumulative number of earthquakes over the last 11 days. Do note that the numbers of earthquakes do not correspond to the energy release. The numbers show a decrease, but the energy is increasing. Image by Gaz Dale based on data from the Icelandic Met Office.

The amount of gas becomes higher the closer you come to the mantleplume that is residing near Bárdarbunga below Vatnajökull. In Reykjanes the magma is poorer in gas, so the force is less.

As the magma nears the surface the pressure from the crustal over-burden will decrease, and the gasses that are locked into the magma will start to come out.

Think of it as a warm soda can that has been shaken. If the lid is on (over-burden pressure) the carbon dioxide will stay dormant in the soda, but as soon as you pop the lid you will get covered in sticky sugary soda.

As and when this start to happen the magma will start to expand and that increases the pressure, and this in turn will push apart the dyke even more, and the gasses will push mainly upwards since they are a lot lighter than the magma it is originating from.

By now we know that a dyke has formed at the old (formerly) dormant Fagradalsfjall volcanic system. From GPS measurements and InSAR we know that the dyke is 7km long (horizontal extension) and that it is 5km deep (vertical extension), and that it is 1.2 to 1.5 metres wide (dilation).

Depth of earthquakes over the last 11 days. Image by Gaz Dale from data by the Icelandic Met Office.

We know that in volcanic rift systems dykes prefer to extend horizontally so that they become longer as magma continues to pour into the expanding rift. This is due to the mass of the magma creating a disproportionate pressure lengthwise.

This will continue until the expanding rift encounters harder colder bedrock at the ends. When this happens, the systemic pressure will jump up a notch.

In a system like Fagradalsfjall there is a lot of pent-up strain, up to 22 meters worth of it. This means that the lava can push the sides of the dyke apart until all strain has been accounted for.

What now, 22 meters? Well, that is the maximum figure of the accumulated motion of the MAR at Fagradalsfjall since the last eruption in the region. From this we obviously need to deduct all swarms that have formed dykes since the last eruption in the region.

To this question we do not have an answer. So, the available pent-up strain might be another half a metre, or several meters.

Latitude of earthquake locations for the last 11 days. Image by Gaz Dale over data from the Icelandic Met Office.

And this is the interesting part, because as soon as that is done the pressure will notch up again, and the dyke will start to propagate upwards, plus the buoyancy effect, plus the expansion of the magma as it nucleates out volatiles… By this point there is literally no return and an eruption will occur.

Now we just need two more figures of interest. The first is how much magma is entering the system, and that is roughly 20 cubic metres per second on average. This in turn equates to 50 cubic meters per second of lava in its fully nucleated fizzy state if an eruption would occur. At least if we assume a steady state of magma arrival to eruption rate.

Now we just need to know how much magma has been emplaced at this moment. It is so far a measly 0.05 cubic kilometres and counting.

This equates to what is called a tourist eruption in Iceland, complete with nice lava fountains that may come from one or several vents along the rift. There will obviously be little, or no ash if the eruption does not end up in the ocean. I will soon return to the ocean issue.

 

The miscalculation

Longitude of the earthquakes during the last 11 days. Image by Gaz Dale using data from the Icelandic Met Office.

This section could also be called: When nature kicked Carl’s model in the teeth. I can though comfort myself with being in good company on this.

My initial modelling was based on historic instrumental data. And this gave at hand that the pent-up strain was significantly less than it was.

This made me assume that the maximum possible seismic release would be akin to the famously noisy eruption at Holuhraun, and that when about as much seismic energy had been expended an eruption would occur. Oh boy was I wrong.

Back when I did my research on the Lakí eruption I modelled that it had by necessity had a very high seismic activity, including several earthquakes above M6. This also seemed to be evidenced by written sources and collapsed houses.

Back then nobody agreed with my estimates, but after seeing this I think that it was correct after seeing this utter melee of earthquakes. After all, the strain potential in the area where Lakí happened is much higher compared to Reykjanes.

I do think that Reykjanes is proving my original point. Alas, I digress…

What I had done was to take the historic instrumental data and just extend it backwards for Reykjanes all the way back to the last eruption.

In hindsight it is easy to see where this model was wrong, and I should really have caught my mistake. After an eruption, the strain build-up will be aseismic. This means that for quite some time there will be no earthquakes releasing the strain, and this creates a bias in that you would assume that there is more released strain compared to the reality of nature.

Second mistake was that I assumed that the crust was more plastic compared to what it turned out to be. This in turn meant that you get more, and larger, earthquakes compared to the size of the dyke since it takes more power to crack the rock.

Therefore, my original estimate of the needed time until an eruption would start was off. Originally my original estimate was 5 to 12 days (starting the clock from the beginning of week two of the swarm).

 

Current estimate

The Icelandic word for a dyke is Kvikugangur. This is a pretty good graphic of the dyke at Fagradalsfjall. Think of it as a hanging sheet of magma candy… Image from Iceland Review.

I am still convinced that an eruption will occur, and for the same reasons as back when I started to see this as a runup phase.

That being said, pinpointing exactly when and where is something completely different. Let us start with guesstimating the when (well, at least if nature does not throw something new into the works that I have not yet figured out).

Let us start with the length part. I cannot for the life of me see that the dyke will continue much further south, at least not longer than to near the coast. There is just no evidence that Fagradalsfjall has erupted previously that far south.

This means that the crust is becoming ever harder and more resistant the further south the dyke extends. As and when this happens the dyke can extend a bit more to the north, and then the same cold and hard crust will happen again.

After that, the question is how much the dyke can dilate as the magma pushes it apart. This is obviously the big unknown part. We do know that it is less than 22 meters, and significantly less so, but how much? I have a problem seeing more than another 1.5 to 3 meters, but here is where I was very wrong previously.

Let us say that we have another 0-5 days of horizontal extension, and 0 to 20 days of dilation. After that there is less than 2 days of vertical extension until the magma reaches the surface.

Now, is there any sign that the pressure is increasing that we can look for? Well, yes there is.

Currently the magmatic intrusion has been mostly evidenced as horizontal displacement and only locally have upwards motion been detected. As and when the horizontal displacement dies off and the vertical motion picks up pace an eruption could happen anytime.

So, what is the verdict on that? Yes, there is increasing vertical uplift, not by much but enough to take notice of.

So, the guesstimate is that an eruption is probable to occur within 2 to 25 days from now, unless something happens that is stopping things up, and I see that as ever less likely. I also believe that the eruption will occur in the southern part of the rift.

CARL REHNBERG

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486 thoughts on “The Happy Dyke of Fagradalsfjall”

    • Thanks for that. Goggle translate at its best: “The corridor landed on a ledge in the south.”

      • On the RUV live feed, giggle managed this on the 9am update

        “The stars now form a rather handsome donkey between Reykjanestá and Kleifarvatn.”

        I assume it is a reference to a smile but i’m curious what the proper translation is?

    • Interesting translation. Google at its finest…ish.
      But a good report. Thanks.

  2. Is there a feed overlooking Natthaga which is currently working?

    • Re the Borgarfjall cam :-
      From the RUV page:
      “Tuesday, March 16, 8:22 p.m. – Contact with the webcam was interrupted at 4am on Tuesday. Repair work is underway.” (translation courtesy of Bing)

  5. From January 20th to 1st of February 2021 we had an uplift on the Reykjanes Peninsula of max. 35 mm. Does anyone know how high/low in total we are today since January 2021?

    • Thanks. I’d been wondering whether that was what was showing on the drumplots, so it’s nice to have confirmation from more qualified eyes.

  8. What happens if the new magma flow reaches the slushy stuff from last year’s intrusion at SKSH? I think the older stuff outgassed a bit – does that have any bearing on the outcome of mixing them?

    • I suppose crystallization in the older magma slush would be a potential issue, too, yes?

      • This is interesting from that link and has a bearing on the current activity. It probably goes some way in explaining why only a small nunber of quakes are confirmed, as it looks to be quite a manual process.

        “It can be complicated to estimate the size of larger earthquakes, but now several of us have studied the event and this is the result” says Kristín Jónsdóttir. “This is partly because of strong wave reflections in the crust in Reykjanes Peninsula that complicate the data processing.”

        • There is always an excuse for an error, “I was drunk” or “No one told me that I have not to behave like a sheep” or “I am human”.

          Amen

  10. Do you think the next eruption (fingers crossed) in the Socorro region of New Mexico will be similar to this Icelandic one?

  11. I noticed that it is possible to select a custom area on the map in Skjálfta-Lisa (“Veljið svæði á korti”). I traced out the dyke on the map to get a better picture of the dyke progression. This is what I got:

    Note the sudden shift at March 3. That was when volcanic tremor was detected. At that point activity shifted from Keilir to the central part of the dyke, where it remained until March 9 when the dyke again broke out and progressed south. Now, since yesterday, activity is back at the central part again. Note that for every such episode it comes a little bit closer to the surface.

    • Updated depth with recent data. Seems like there are more shallow quakes now. However, do note that more of the smaller quakes get verified since the activity is less intense now. Maybe that could cause a bias in the reported depth.

  12. Latest from Reykjanes, from science advisory meeting https://ruv.is/frett/2021/03/10/helstu-tidindi-2000-jardskjalftar-i-gaer:
    1) the smaller number of large earthquakes is due to ‘normal’ variability and not interpreted to mean that the unrest is decreasing or that an eruption is less likely 1/n
    2) magma is still streaming into the dike intrusion but in a different part of the dike
    2/n
    3) the most likely eruption location has moved 4-5 km from the southernmost end of the dike (Nátthagi), to its middle (NE of Fagradalsfjall). This is based on seismic, GPS and InSAR data. Pic of earthquake locations from
    @Vedurstofan

    3/n
    4) the dike is no longer intruding to the south 4/n
    5) part of the intrusion has solidified since it’s been ‘sitting around’ in the crust for 3 weeks. But this does not make an eruption less likely 5/n
    6) the scenarios of likely events are unchanged 6/6
    https://twitter.com/EIlyinskaya/status/1371902078239510531

  13. 18.20 – As readers have no doubt noticed, our webcam showing Nátthaga frá Bolafjall fell into the night. Our most powerful men, Freyr Arnarsson and Guðmundur Bergkvist, strapped on the mountain blocks and went up to Borgarfjall to get the engine running again. It is now back on the air, and the batteries have been refilled. The equipment was more powerful than expected.

    On the newsfeed.

  14. This is probably based on the drone footage that was linked a couple of days ago.

    https://www.ruv.is/frett/2021/03/10/helstu-tidindi-2000-jardskjalftar-i-gaer
    16/3 15.46

    Police warn of rock falls

    The police in Suðurnes issued the following warning to the public just before:

    “Due to a rock fall following strong earthquakes in Reykjanes in recent days, the police in Suðurnes encourage hikers to be careful in the mountains in Reykjanes. However, there is not only a danger in the mountains in the area, but also along the shores of the peninsula, which are sea cliffs and cliffs. A large rock fall has been observed due to the earthquakes from the cliffs west of Festarfjall near Grindavík. Such a collapse can be expected elsewhere, such as at Krýsuvíkurbjarg and Valahnjúkur by Reykjanes lighthouse. In the attached photo, which was received by the Meteorological Office, you can see how the collapse has occurred from sea cliffs west of Festarfjall, “says the announcement.

  15. If we translate the Icelandic text to English then to Icelandic again, then back to English and so on: does the text sequence converge to a stationary, i.e. invariant text in the limit. A text that does not change if translated back and forth? An ‘equlibrium’ text? And, what does it say? Just kidding.

    • Generally, the translations I have been getting seem a bit better than others (for example, I got mountain instead of ledge earleri), but that last one caused soem headscratching :P.

  16. Wrong reply button again. It was meant as an – obviously unecessary – supplement to Avalonlightphotoart’s posting. So to make my comments less futile, here are the latest quakes (not verified):

    • Te blue cluster shows the location of the dyke quite nicely too on the first plot, if you ignore the outliers, which are probably due to tension or just misplaced.

      • The grouping, Avalonlightphotoart, ist done statistically. I’m certainly no geologist. The grouping helps perhaps to understand things but is certainly not the one an geo expert would come up with.

        I think I start to realize that the idealistic idea that the ‘reply’ button works for the last posting in a thread was naive. This post will again be placed at the wrong place…

        • Even if it may be slightly arbitrary though, it does help to separate them for easier visualisation, which is often the key aspect of presenting data.

  17. I wonder what would happen if you put some random nonsense in to giggle and translated it into icelandic and then back.

    I tried Hvernig bætir litli krókódíllinn skínandi skottið. Hellið vatni Níls á öllum gullskala. Hversu glaðlega virðist hann glotta, hversu snyrtilega dreifir klærnar. Og býður litla fiska velkomna, með brosandi kjálka.

    Giggle must have a famous quote filter as it came back pretty much the same as the poem.

    randomly mixing up lines does not do much either the nonsense remains I may have mispelled some words to see what would happen. the last two words english words were ‘ a nigh’ not a common expression.

    twinke twinkle litla kylfu eins og teatray á himninum hvenær mun eldfjallið gjósa nálægt

    -julie

    • I think there must be some variation/algorithm built in, as teh translations I have got back are slightly different to what others have had. I’ve noticed it with the app in Polish too. A few times, I’ve tried conversing with my friend’s mum and some of the translations really don’t make any sense (partly because it doesn’t always recognise my Devonshire accent I think), even when it shows what it thinks I said in English, I can’t understsnd it :P. The Norwegian phrases I’ve played around with in the past haven’t been too bad on the whole, although my Norwegian is very rusty now.

  18. It seems that Etna will go for the 14th paroxism tonight… but it will not be easy to have a good view, it’s cloudy.

  20. Theres been relatively little activity the past day, it looks like the dike is at its maximum size. Its like the calm before the storm, I think theres a very good chance the next pulse of quakes will open the fissure to the surface, especially if it is so shallow that there is now visible cracking in the ground in places, well under 1 km now for sure.

    Thing is with only 1 km or less to the surface, it will probably be little more than a few minutes to actually warn of any eruption. Kilauea a few months ago erupted after an hour of warning, just as is the case for Fagradalsfjall now it was long expected, but still took us all by surprise at how sudden it was. Kilaueas magma chamber is shallow but still at least 1.5 km down, which is almost twice the depth of the Fagradalsfjall dike. I expect we will see nothing particularly noteworthy, just another little quake peak on the graph, just this one comes with a glow on the horizon.

    🙂

  22. From a quiet but devoted follower of this blog… 😉

    The graphic below the earthquake map showing earthquakes in the last 48 hours seems to have spaced out a lot and quietened down. But IMO’s official remark says “Over 400 earthquakes have occurred since midnight.” No way are there anywhere near 400 points on that graph since midnight. Has something gone wrong with the script that generates the graph, or do you think it’s a deliberate filtering-out of most of them?

    • Do realize how small some of these earthquakes are. An M0 is not much more than a moderate-speed traffic collision. Only the nearest seismographs is going to pick that up. The seismographs we have show strong earthquakes at larger distance, but smaller ones only for their immediate environment. To count everything you need to combined all seismographs, figure out which quakes are the same, and perhaps even extrapolate to figure out who many you would have missed altogether. (They probably don’t do that last step which is far from trivial and carries uncertainty.)

    • I got 998 quakes now in the list since 00:00:00. Here are the absolute frequencies of the magnitudes (all preliminary):

      0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8
      77 62 57 53 55 58 58 53 53 50 45 58 34 38 36 27 20 17

      1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.3 3.4 4.3
      15 17 22 13 13 14 10 8 3 7 12 6 3 2 1 1

    • I don’t think all the quakes are showing on the map and mag v time plot below it; there aren’t many very small quakes on the list.

      Been thinking that since yesterday or the day before.

    • Mind you, with fewer quakes, IMO should be able to confirm more of the smaller ones so we can see what is going on better.

    • Yay !! Beat me to it !!

      Seriously, the locals look really, really nervous. Yes, this is Iceland, and they’re accustomed to unquiet geology, but this zone has been mostly quiet for a millennium, long enough for the old lava flows to become pleasantly green…

  24. Is there any data for the magma supply to the rift as of today? The quake rates are down a lot comparatively but that could be because all the rock breaking is over and it is unobstructed, with the supply still being unchanged.

    • Its filling the dyke intrusion… without breaking too much rocks now.
      But this is … it… the time… that determine if it will erupt or not.
      At any time the dyke can stop filling…resulting in a shallow intrusion and failed fissure eruption

  26. Slightly off topic from Iceland, this time Greece. There seems to be an earthquake swarm around Larissa in Greece that looks quite similar, prima facia at least, to what is happening in Reykjanes. The really weird thing is that there isn’t any known volcano dormant or otherwise in the immediate vicinity of the swarm.

    Fagrad has woken up.

    Question, could a new volcano be formed in the Larissa region?

  27. Is this tremor? Can not see any related EQ-activity.

    hraun.vedur.is/ja/drumplot/drumplot/fag_highpass_2.0.png

  28. An interesting chat with Páll Einarsson(Professor Emeritus of Geophysics/University of Iceland) about Reykjanes posted yesterday:

    • THX for sharing!

      Curios what’s behind “the eastern part”, from a line dance to a tango?

      Emeritus of inorganic analytics
      cementboy

    • Paraphrased:
      Interviewer: ” so the recent earthquakes have released enough stress so that we won’t be having a larger earthquake?”
      Professional Scientist: ” no… the stress hasn’t been released on the other side so there is a greater possibility of an even bigger earthquake.”
      and that’s the difference between having an “Opinion” and having “Facts”. i love science. i get bored out of my tree with ‘opinions’ …. who gives a flying bat for opinions. opinions change with the accumulation of facts. More time is wasted on “in my opinion….”… BAH! humbug. i’m so tired… i refuse to listen to the opinion news/ political crude any more…. i’m down to this board and the weather. …. geee i wish i drank…
      Best! from mots. 3 steps from the quiet room.

      • We do our best.. volcanoes have scant regard for opinions and do what they want. They won’t always listen to the facts either!

      • <<<<<<<< Passes Mots a drink….. hot malted milk…. "Cheers!" . I am not very interested in opinions either …Ideas? Yes……. Questions? Yes……. Theories based on evidence and facts? …Yes… Cheerful banter and discussions on here ? Yes! Yes! yes! Hang in there Mots. Nearly time for jab #2 but I don't think I will ever enjoy shopping again! Thank goodness for good friends and an interest in the natural world that totally ignores the rules and regulations of humans. Today I saw a bumble bee looking at my "Insect Hotel" as a possible summer home and also there was a tiny ant sitting on the front step beside me in the sunshine…winter here is nearly over!

        • my second jab was very weird/sicky for one and one half days. Felt like cramps throughout my core…. every organ was involved, heart, lungs, intestines, stuff i didn’t even know i had…. so it it happens to You, hang in there… it does pass. and it is so wonderful to be fully vaccinated. Let us know how it goes… You know, “It’s for Science!” from the Princess Bride. 😉

  29. Either the earthquakes are getting more shallow:

    or the technicians have more time to input smaller quakes into their statistics…

  30. When you look at plots of the earthquakes in this swarm, why is there a seismic gap between Keilir and Krysuvík?

    eg. https://skjalftalisa.vedur.is/#/page/map

    Is this gap likely to fill in? It must be on, or close to, the plate boundary so the stress / strain (never know which is which) must be high.

    • I think that must be what Páll Einarsson was referring to in the interview above. He mentioned a lack of stress release to the east, even though it is building.

      • I though he was referring to east of Krýsuvík, e.g Brennisteinsfjöll, – but I could be wrong.

        • Yes, that is what he meant. That region has larger earthquakes because the fault segments are longer. There were events there though some 20 years ago but there still remains a gap

  31. https://www.cnrs.fr/en/deep-magma-facilitates-movement-tectonic-plates

    https://www.google.se/amp/s/www.techexplorist.com/molten-rock-located-under-tectonic-plates-encourages-move/35842/%3famp

    Looks like Earths entire Astenosphere are more soft and more partialy molten than previous realized, perhaps the astenosphere is the dying remains of an old upper mantle hadean magma ocean?
    The litosphere slides over the Astenospheres partialy molten rocks.

    • Its possible that the larger Super Earth class Exoplanets with their greatly increased internal heating and radiogenic heating because of more mass, they may have true upper mantle magma oceans .. that their alien tectonic plates slides over.

      Super Earths ( a few Earth masses more ) coud display hyperactive plate tectonics? With many plates, rifts, mountain ranges, volcanoes, trenches, possible so active that They are a chaos of twisted protocontinents in a large global ocean. With only small rudimentary landmasses .. like New Zeelands, Icelands, Samoa
      Earthlike Super Earths must have fascinating geology with their far deeper hotter mantles

      • They probably wont have any land, even a superficial ocean would probably be deeper than the height mountains can reach, and the hotter mantle might mean water is forced to the surface. Early Earth was like this, an ocean planet with almost no land.

    • It is either the dying down of this swarm or the calm before a new swarm storm (or an eruption).

      • In my opinion, we had a waiting for the storm yesterday. The intensity of (relative) larger EQ’s seems picking up. Sit back, wait and see…

    • Yeah, it looks like she’s wiggling up. Depth is very shallow on these

  35. Here are all verified shallow (0-3km) quakes >M1 since Monday. Activity is clearly focused at the center of the dyke, but there’s also a small cluster at the southern tip that’s almost right under the RÚV webcam. If an eruption starts there it should make for some really interesting footage, given that the camera survives.

  36. Thursday
    18.03.2021 11:20:38 63.881 -22.279 4.5 km 3.3 99.0 2.4 km S of Fagradalsfjall

  37. Yeeeeessssss … preeeecuuioousssss
    Swarm is probaly comming back now

  38. Would be a shame if the eruption begins right now, its raining and you cant see anything 🙁

      • I can imagine the geothermal engineers: “OK lads, start drilling here…”
        Eruption starts.

        • as a matter of fact they did that at Krafla, and hit magma 3 times.. then decided to abandon their efforts. Interesting, they hit ryolite magma, not basalt.

          • That also happened at Kilauea in 2005, finding a dacite magma pocket, its probably not all that strange to have evolved magma inside big basalt volcanoes like this, basalt doesnt really mix with silicic magma, fissure 17 was quite a strange event in that some of this evolved magma did reach the surface. I read something too that some of the Galapagos volcanoes have evolved magma in them, so it is probably a common occurence.

            I think there are also some rhyolite domes at Krafla, actually the prerequisite to be a central volcano in Iceland is that said volcano has silicic rocks or a caldera, or both, otherwise it is just a fissure swarm.

          • I understand that they did, after repeated tries manage to plug into a lava pocket. First few times saw their equipment flying. At the start they got incredible amounts of power (>20MW) but the power output tampered way too fast. So in the end they said its not worth it.

  40. It is possible that the decrease in seismic activity is a precursor to an eruption. In an interview with RÚV, Kristín Jónsdóttir from IMO says that before the Krafla fires started, seismic activity and deformation had decreased. At the same time she also points out that Krafla is a different volcano with a clear magma chamber, someting that the Reykjanes peninsula lacks.

    New satellite radar measurements are expected tomorrow.

    https://www.ruv.is/frett/2021/03/18/minni-skjalftavirkni-gaeti-verid-undanfari-eldgoss

  41. A chat with: Sara Barsotti – How IMO gets ready for a possible eruption in Iceland. March 15th, 2021

  42. Interesting swarm between Mauna Loa and Kilauea, Station: MLOD is having a lot of fun.

    started with 3.1 + 3.5

    • Looks like a slip of one the strike slip faults that are created due to opening of Mauna Loa’s Northeast Rift Zone, through shearing between the mobile and fixed portions of the flank. This is tectonic, a mainshock-aftershock sequence, same as the deep M 3.3 near Kilauea yesterday, which was followed by some other small earthquakes there.

    • The Pahala Swarm also continues to be very active, 25 earthquakes so far today. It has been more than 2 years already since Pahala became so active, but still there’s no clear sign it is leading up to anything on the volcanoes.

      • After the 4.1 quake on the Pali on 3/15 all of the tilt readings IKI,SDH,ESC have leveled off.

  43. Heard that geophysicists working on the data have floated the theory that all the deformation interpreted to be caused by propagation of the dyke could instead be interpreted purely by strike slip faulting. Meaning there could be no magma. Just a theory at present, but was discussed today.

    • It’s an unusually large swarm for that. OTH, if there has been any evidence of magma de-gassing, I have missed it.

    • I had been wondering. There has been a bit of tremor but not much. However, strike-slip faulting tends not to last three weeks, and the insar data is not easily fully explained as strike-slip. Some extension seems to be needed too. But there is not much inflation. There have been intrusions in the peninsula over the past years, so magma would not be unexpected. The amount is as yet unclear.

      • I have been wondering too. The photos I’ve seen of cracks do not look to me as caused by a dyke, faulting from dykes shows a downthrow, one side drops into a graben, the cracks seem more tensional and could have been formed above a buried strike-slip. Fagradallsfjall has not had any eruptions in the Holocene nor signs of graben formation due to dykes. And this whole sequence did start with a tectonic earthquake, the M 5.7. The duration seems to long though, it is outside of my knowledge whether faults could take so long to settle after an earthquake.

    • The gps movements in the region are slowing down. Earlier the Eurasian plate, now also the ones on the North American too, even far away Nylenda has slowed considerably. There is a mix, the faults and the six/seven volcanic zones rowed up.
      Kind of logical that lot of the stress caused by the moving plates triggered many tectonic quakes.
      I always had the impression that there was involved just a blob of magma.

      Well, impressive it was! Maybe more to come in next decades.

  44. Today’s quakes (non verified ones from the website). The frequency was peaking around noon and declining afterwards. The maximal quake density is attained ~2km north of Natthagi below Fagradalsfjall.I attached a figure depicting magnitude vs.indicated quality, showing that the assessed quality is typically larger with larger events. Maybe not too surprising.

  45. They have read elevated Radon levels during gas samples today.

    Interesting

      • “Among other things, the concentration of Radon gas (222Rn) was measured, but it is known that the concentration of the gas increases just before or during an eruption.”

        Taken straight from the scientific meeting today.
        Elevated levels of radon has been seen before and eruption also….after large quakes. So we are still 50/50 right now.

  46. Thanks for the latest post Carl. Your time and dedication is appreciated. Has anyone else got a bad view on the Mila IR cam> I have do definition and just a wobbly, grey tartan pattern effect.

  47. What’s the now-best webcam for watching the now-likeliest eruption site? Since it seems it will erupt north of the area watched by the Nátthagi cam, and south of the area watched by the several Keilir cams …

  49. 2021-03-19 05:34:25.3 ML 3.5 ICELAND REGION
    2021-03-19 05:27:48.7 ML 3.9 ICELAND REGION

    emsc….

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