Bárdarbunga – The Elevator to Hell

Icelandic BBQ. Photograph copyright by Eggert Norðdahl.

Icelandic BBQ. Photograph copyright by Eggert Norðdahl.

Due to me having had a couple of hectic weeks at my day job and catching this year’s influenza I have not gotten around to writing as much as I have wished. What I had wanted to do by now would have been to explain more in detail what is happening at the Icelandic eruption, but perhaps mostly why it is happening as it does.

The advantage is that we have seen volcanic history unfold and a type of eruption never witnessed before in the age of instrumentation. Early on Icelandic scientists tried to use modeling from the Krafla Fires eruption sequence and to be honest that led them quite astray. The Krafla Fires came out of a shallow dyke, whereas this one is much larger and deeper, skirting or breaching down to the mantle. Also, the size of the eruption is quite different.

As we look at the eruption via webcams, or look at pictures it is easy to think that this is a small eruption. But nothing could be further from the truth; it is just that the sheer scale of the Icelandic landscape is fooling us all.

In reality this is a major eruption, not on the brutal scale of let us say the Lakí eruption, but it is still massive. By now the lava flood covers 50 square kilometers, the edges are reported to be between 6 and 10 meters high, but that is not the average depth of the lava, that is more likely to be 30 meters and that would put the total output at around 1.2 cubic kilometers if we allow for the lower edges. Now, let us start comparing with other large eruptions.

Tolbachik eruption in december 2012.

Tolbachik eruption in december 2012.

Eyjafjallajökull is an eruption that has etched itself into our brains. That eruption coughed up as little as 0.15 km3 of lava equivalent. The lesser known Grimsvötn 2011 was the largest eruption in more than a hundred years in Iceland. It erupted about 0.4 to 0.5 km3 in lava equivalent. No, we must go further back and further out.

In 1975 the Great Tolbachik eruption took place, it erupted 1.2 km3 and it used to be the standard that every later effusive eruption was measured against. It was even called “The Great Tolbachik eruption”. But now Holuhraun is busily surpassing that figure.

Instead we have to go for the VEI-6 1991 eruption of Pinatubo to get figures that are larger. In lava equivalent that would be 4.5 km3. So far there is nothing saying that the Holuhraun will reach that large a figure, but on the other hand there is not much actually saying that it will not.

Pinatubo's eruption in 1991, the second largest eruption of the twentieth century.

Pinatubo’s eruption in 1991, the second largest eruption of the twentieth century.

If we instead look at Iceland we will have to go back to the 1874-1875 cataclysmic Askja eruption to find a bigger eruption. That would place us at 1.8 km3 of lava equivalent. To get a larger Icelandic effusive eruption we have to go back to the 14 cubic kilometer Lakí eruption. I find it rather improbable that we will see something on the scale of Lakí.

At the current stable eruptive rate of 350 m3/s Holuhraun erupts 0.9 km3 per month and at that rate it will become a pretty large eruption soon, and remember that it is the world’s largest eruption in the last 23 years and Iceland’s largest in the last 139 years. Next time you wonder when the “real eruption” will begin, think about it again.

The caldera plug

I have used the word plug for the huge lump of rock that sits inside the circle of earthquakes that form the ring fault around the caldera floor. But plug is not a good description really, so perhaps we should come up with a better name. On the other hand it kind of describes it quite well.

This plug has been dropping at an even rate since the onset of the eruption, but there have been a couple of misconceptions about it that I wanted to explain better. I did so in a comment earlier today, but I thought it deserved to be expanded into a proper article.

The dynamics of the plug

Image by the Icelandic Met Office. The image shows the earthquakes outlining the ring fault and the dyke leading all the way to Holuhraun.

Image by the Icelandic Met Office. The image shows the earthquakes outlining the ring fault and the dyke leading all the way to Holuhraun.

There is a huge lapsus in thought running around concerning this eruption. I will try to correct that now.

We know that magma is leaving the system at a rate of 350 m3/s lava equivalent and that it ends up at Holuhraun. We also know from GPS evidence that this is creating a system less pressurized. I am not using the word under pressured since this would implicate something else. I will now try to tie the knot on the sack.

Now, if a pressure of 1 is needed to keep the caldera lid(s) in place (the plug) we now have less than 1, it would probably be possible to calculate how far below 1 we are, but that would take quite a bit of calculations and contain a great bit of uncertainty at best. For now <1 is enough to know.

At the top it has always been assumed that there was a pancake shaped layer of magma, or a set of pancakes. The depth for these pancakes was assumed to be 2 km by the Icelandic scientists. Remember that this might not be entirely correct given new data. But, if we assume it to be correct this would most likely be stale magma that is unlikely to be eruptible and form a rhyolitic mush.

Below that there is now believed to be a secondary magma reservoir between 5 and 6 km depth (source: IMO), I think this forms another set of pancakes, or it might be a more solid “chamber” like structure. This most likely contains hotter eruptible material.

At about 10 km we have a larger chamber and between 16 and 20 km you have the start of a boat hull shaped reservoir stretching down to the mantle.

Image by the Icelandic Met Office. This is the station BARC residing on top of the ice on the Bárdarbuna caldera, notice the very steady drop.

Image by the Icelandic Met Office. This is the station BARC residing on top of the ice on the Bárdarbuna caldera, notice the very steady drop.

And it is also believed that the entire shebang is connected via a permanently open conduit. Since we are talking about connected pressure vessels the pressure should be pretty much the same equilibrium of 1 everywhere, or in our case an equal <1.

Now, if it was higher somewhere in a single part of the system it would rapidly equal out to be the same all over. So, if we get a pressure below 1 at the deep chamber that feeds Holuhraun we get lowered pressure in all reservoirs causing a cascading chain of readjustments.

The magma at the top is most likely not going to go anywhere since it is stale rhyolitic mush, but magma from reservoir two is most likely going down to reservoir 3 to feed Holuhraun, magma should also be moving up from the “hull” into the feeding reservoir number 3. Basically, the system is at <1. This makes it pretty impossible for magma to move upwards and form new intrusions since the easiest path would be to continue out towards Holuhraun. At least until a path opens that goes straight to the top, then the resistance of the dyke might be greater than the extra height to reach the surface at the caldera floor.

Now, the general belief seems to be that the pressure is greater than 1 however impossible that would be. This would mean that more magma is entering into the system then is going out. This would at the very least leave the plug where it is. But it is more likely that it would either push the plug upwards, or that magma would move up from the “hull” into reservoir 3, onwards into reservoir two and then up into reservoir 1 were the rhyolite would be reheated, and we would have noticed that at least. But even if the rhyolite didn’t blow up we would be seeing inflation and a GPS permanently moving upwards and not down.

By now any good physics student should be raising their finger to say “but won’t the system be striving to achieve equilibrium in the pressure, i.e. 1?” But of course! And the only way to achieve that is by the lowering we are all following on the GPS at Bárdarbunga. It is equally marvelously linear as the output of at Holuhraun is stable.

Now one last thing that seems to have swept past everyone, the missing magma. Seemingly twice as much magma is either residing inside the dyke leading to Holuhraun or have been erupted at Holuhraun as is seemingly leaving Bárdarbungas magma reservoirs if we calculate it from the drop.

First, a small part of that differential is what is giving the <1 value of pressure, but it is a rather small part. Initially when I noticed this I thought it was magma from the initial intrusion that took place in the months prior to the eruption. But, with time it became apparent that this seemingly missing magma is also ridiculously linear.

350 m3/s of lava equivalent goes out, and the caldera plug drops 175 m3/s in lava equivalent. Now, the solution is to be had by the pesky pressure differentials. Not only is the plug dropping, there is also decompression melt running at the bottom of the “hull”.

Now, when I speak about “low pressure” it should be understood that the pressure is still tremendous. It is just lower then what is needed to keep the caldera plug up and lower than is necessary to keep the mantle material in a semi-solid. With decompression melt in this case it means that the pressure drop makes the semi-solid mantle transition into a more liquid state (magma).

Now some people seem to think that it is the dropping plug forcing the magma out, but this would just create another pressure level of 1 and we know that the drop only equates to half of the erupted lava, so there just simply has to be pressure below 1 at play, and it also pans out with the decompression melt model.


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1,190 thoughts on “Bárdarbunga – The Elevator to Hell

  1. For those living in the UK (and those familiar with the UK), here are three places where I’ve introduced the lava field to the UK map: (1) London (2) Scotland and (3) Salisbury Plains:

    • Thanks Mopshell (Mapshell), also for the other nice maps. But I wonder if in GE distances are preserved when moving overlays. Also, depending on the projections used internally by GE, the measure changes when applied to different parts of the map (sometimes I believe that the earth isn’t flat, but this is crazy thinking). Doesn’t it seem that your 4km-measures have different sizes when compared to the lave-outline?

      • I was wondering about that but because each of the maps that I used are of different magnifications, it’s hard to tell. Basically what I do is, have two 4km measures, one on the GE image and the other on the overlay. I resize the overlay until its 4km measure is the same as that on the map image. Once the overlay is positioned where I want it, I then link it to the map image. If I then change the size of it, both the map and the overlap resize at the same ratio. It isn’t an exact science but it’s the closest I can get. It gives us an approximate idea at least. 🙂

        • They are realy useful. The one of Manhattan got to me since I have walked from one end to the other in a day. It is the only way we can understand the scale to have it emplaced like this.
          If it is off with a few hundred meters does not really matter.
          Good ‘un!

        • I’m not nitpicking. If you compare the 4km distance in the first picture with the one in the last picture you see that either the 4km was shrinked or the lava field expanded, and that by a considerable factor (compare the length of the lava-island: it’s ~3km in the above pic, but ~6km in the one below). Anyway, it’s good to have a rough impression of the extend of this exceptional eruption.

          Btw: any name so far for the lava island?

          • ok, I just checked it in GE again (assuming GE is accurate enough for our purposes and I have no reason to doubt it!
            Measuring the distance from the vent to the furthest tip of the flow in the radar image posted the other day using the ruler function in GE gives you 17.41 km.

            The image overlaid on London is slightly inflated but not by much, maybe 800m or so. Here’s 17.4 km as the crow flies from the bend in the Thames near Shepherd’s Bush towards the Millennium Dome.

            • Then the mystery is solved: in the last picture the distance from Stockbridge to Wilton is roughly 26.7km according to G.E. so there is the problem. The other maps seem to be ok.

              (double post, sorry)

    • Thanks Mopshell! That’s a great way to visualise the extent of the lava. Basically, if the Salisbury one was true I’d be dead, but if I had a space suit I could go to work and see nothing but a flaming lava field spread out below me. Slightly more exciting than sleepy old Salisbury! 😀

    • very nice…. how about one for me………… over the Kenai Peninsula in Alaska. 🙂 Best! and Hi, Mopsy, from motsfo

  2. This one is being followed by quite a bit of tremor. It is still buzzing, you can see a thickening of the line on the drumplot if you zoom up

    • It seems that Google translate didn’t do badly at all because you got it right. The text is confusing even for us natives.

      • It’s more a case of honing in on some key words then guessing the rest! 🙂 I’m surprised that the text is confusing for native speakers; you’d think a media group would be in the business of making their communications crystal clear!

  3. Ahhh, temptation when you have minimal will power is tough going but I like the idea of a self fulfilling prophecy …

    Question to Islander and Irpsit and any other local. How close can an average person actually get to Holuhraun? On my first and last visit to Iceland we flew out on the day Fimmvörðuháls erupted. Always regretted that we never got a closer look than from far away and now this morning I wake up from a dream where I impulsively bought a trip. Having to use 3 weeks of leave before the end of the year I immediately thought why I didn’t think of this earlier! Then I remembered I can’t really afford it without breaking into my savings so I want to ensure I spend wisely.

    I’ve seen all the pics online but also see there still an exclusion zone. How close can you actually get, by guided tour or similar? Thanks! 😀

    • I woke up from a dream yesterday morning – a +6m on the plot! I checked the time (in my dream) and it was just on 7.00 a.m. I knew it was the beginning of something big – and promptly woke up. We’ll have to see if I’m a prophet (no date provided by my unconsious unfortunately). 🙂

        • …and commiserated when it was just an M3.0 so didn’t qualify for a star. 😀 That reminds me — all the earthquakes M≥3 so far today have all been M≥4! That would have been an extraordinary idea back when we exhilarated upon a couple of M3+! 😀

      • Ha ha! Will be keeping an eye out for the 6 at 6, unless of course its after the clocks change 🙂 VolcanoCafe can certainly lead to some interesting dreams. In mine I was actually umming and ahhhing between seeing active volcanoes in Iceland and France – perhaps we’ll see the reawakening of the Chaîne des Puys 😉

        Now, if I only I could dream myself winning big at the lottery … … … Brain has won over my heart and I’ve decided against a trip to Iceland (for today atleast) and I’ve bought myself some thermal underwear instead 😀 I shall save my pennies for Lady Hekla OR Katla, I’m looking forward to a nice hat flavoured BBQ’d steak if she goes first!

      • Dont underestimate dreams.

        Wednesday I dreamt I was fired together with other people. And that day a colleague was fired, and as it was a top position it was quite a stir. Quite a coincidence no? More impressive was this volcanic dream: One day before Grimsvotn erupted in 2011 I dreamt that Grimsvotn and Laki were erupting!

        And even to shock you further: A few months ago I dreamt that there was a large lava eruption between Askja and Bardarbunga. I remember going on my jeep along Sprengisandur and looking at Dyngjfjoll (Askja) and the eruption south of it. Exactly where Holuhraun is now! Yes I am not kidding!

        This is just a small example of my dreams. There are others. Like waking up Christmas morning in 2004 very disturbed after dreaming of a giant tsunami and thousand dead bodies floating. I freaked out, because this is not the sort of dream you want to have on a Christmas morning before meeting the family. Quite shocking no? Eheh, perhaps you don’t believe me.

        Now, because you probably would ask, I tell you two dreams of my future, one is volcanic. Ocasionally I have this recurrent of a lava eruption at the south part of Hengill system, I am at Bláfjoll looking towards Krisuvik. Another freaking dream that repeats every other time since many years ago, it is set in the 2020s and then there are violent street uprisings everywhere, shops closed up (i remember it was sort of food shortage or economic crises), war tensions (i see missiles), etc. Do I believe this is going to happen? Sincerely I don’t know. I just dream stuff, I don’t know if it’s real until these freaking coincidences occur.

        Well, just an offtopic.

        • Dreams like that are normally just your sleeping brain admitting to things it does not want to admit to when awake and that you pretty much now allready.
          I guess the signs was up there that someone would be fired, and Grimsvötn we knew for months prior would erupt, and the same goes for Holuhraun. Heck, I wrote quite a lot about both of the events prior to them happening.

  4. Just looking on the Etna webcams – there is currently a steady plume of ash, with the air over Palermo looking rather polluted

    • Palermo is not really near Etna. It’s at least 200 km distant. And yes the air is rather stuffy there….maybe Catania ? Have a ristretto on my account 😀

    • The big city you can see on some webcams is Catania. It’s located southeast of Mt Etna.
      I think the most of the dust you saw is in real a mixture of gas (Sulphur dioxide) and vapor; in the last few hours damper air arrived. But there is also a continuous, but weak emission of fine ash from Bocca Nuova/Voragine (summit craters). I think the gas emissions at the summit craters are also higher today than during last week (less than 5000 tons SO2/day).
      There have also been sporadic deep seated strombolian explosions inside of the New Southeastcrater, lunching sometimes hot material (most ash) and gas.

      • All volumes in Dense Rock Equivalent, all figures from the Actividad Volcanica (the responsible authority).

        Total ejected volume 0.037km3, amount of ejected fresh material 0.0097 in tephra recalculated as DRE, the rest of the volume was rock and sand being blasted out.
        The maximum columnal height was 10km.
        As such it barely barely scraped together as a low end VEI-4, more likely to be a high end VEI-3. To dub it into a VEI-5 is just a mockery… If so Eyjafjallajökull was a larger VEI-5 and Grimsvötn 2011 was a VEI-6.

        No, GVP is wrong on this one.

  5. I’m frankly disappointed in Team Blue on the drumplots today. While gold leads the way with a magnificent M5.2 and both red and green have given us creditable M4s (M4.2 and M4.7 respectively), Team Blue has barely scraped by with a couple of splashes. Yes they are both M4.0s but it just doesn’t look as if Team Blue are really committed to putting in the effort. “Can do better” is all I can say.

    • Hi Mopshell, You don’t race snails or tortoises do you? Hens are doing well but there has been another rash of unplanned pregnancies. A bedraggled little girl appeared from nowhere a few days ago and presented us with 8 chicks. Fortunately we had an empty coop and mother and chicks are blissfully happy.

      • Are you getting invaded by bedraggled little girls? Sounds like there is a story there somewhere. The “from nowhere” part sounds like the opening of a H.C. Anderson story.

      • No honey, I don’t race snails or tortoises. 🙂 My current level of interaction with animals is limited to feeding the local possums (mother and rapidly growing baby) and wondering if the frog who has taken up residence in the cistern of the downstairs toilet is really happy there or if I should try to find him a new home somewhere with more natural surroundings.

        I’m so glad to hear the girls are doing well and that you were able to take in the poor bedraggled little hobo-ette and her chicks. I wonder where she came from? I’m impressed that she found you and have no doubt at all that she and her chicks are blissfully happy. What a wonderful home they have found with loving people to care for them.

        Have you had your op? If so, how did it go and how are you doing? Please pass on my best to your partner too. ❤

    • And I thought I was the only one wondering if there was anything meaningful to be said about EQ distribution between “The Teams”……………………

    • They are moving forward, a bit slowly though. First I coughed my lungs out, now Islander is coughing them out. But the plan is to get is started ASAP, hopefully next weekend if we can keep our lungs inside our bodies.

      Tipp of the day, go get a flu shot, this years flu is not kidding around. It picks you up and slams you into bed, then it starts getting really nasty…

      • i don’t like flu shots……… meds just don’t seem to work for me. Not saying flu shots don’t work, have kids in the medical fields and they all get their shots and are doing well with them but stuff just doesn’t seem to work right for me. i keep up with my vit C at 2000 iu and vit D at 5000 iu daily and pray i don’t get sick. At almost 70, the flu can be a game over for me. But thinking about it; at almost 70 most things are over for me. 🙂 Best! motsfo and ps…. how many of us in the northern most climes take Vit D and how is it working for You?

        • I don’t like flu shots either and find that echinacea works wonders for me (liquid, not tablet form) plus moderate amounts of alcohol. 🙂 It isn’t the needle thing either. I’m happy to get my regular B12 shot and I’ve spent enough time in the ER these past 20 months to be able to give paramedics and nursing staff a quick priority rating of the four best veins for the intravenous whatever-they’re-giving-me-this-time. Personally I prefer the magnesium drips – they don’t have much effect on my erratic heartbeat but they guarantee I won’t suffer any muscle cramps for at least a month! 🙂

          • Very, very off topic here but something I am very interested in finding out from Mopshell.
            How often do they give the B12 shots in Aus? I assume they are for pernicious anaemia which very many of my extended family member have. 5 out of 11 siblings in parents family. I ask how often they are given in other places because in the UK they are only given 3 monthly and one particular member of family finds they are feeling very ill indeed by the time the 3 months are almost up. Would love to know how often they are given in other parts of the world as the UK NHS is notoriously penny pinching because of not so good government funding.
            Sorry to everyone else for this very OT post.

            • As I understand it, 3-monthly is the standard here too. Mine are 5-monthly but likely to become more frequent as I get older apparently.

        • With me flu or cold, has a direct link to something I do that reduced my immune system.
          Most often some stress or psychological stress, sometimes unproper eating or lack of sleep.
          If I keep calm, physical exercis and good eating, sleep, flu never gets to me. If I fail one of those things for a while, then flu strikes nearly certain, if it’s winter. And when do I get most depressed? Winter. So getting enough sunshine and engaging in uplifting activities is a must for me.

          • And i would never get the shot. I only get shot for deadly diseases. Because for easy stuff like the common flu, it’s better to exercise my immune system. Anyways, what is 39ºC fever and just a general disconfort. A walk in the park compared to most tropical diseases.

            Also flu mutates so fast, that I don’t really believe a shot can protect you that much.

            But groups with risk of death from flu can certainly benefit from it.

            • Antique people in the UK get free flu jabs annually, also this year vaccination for 30 different types of pneumonia (that’s what the nurse said anyway). Minor soreness on the pneumonia side, zilch on the flu.

              Sadly its flue and not colds, just getting over this years one which takes 6 weeks to fully clear , sigh.

            • I only once ever had a ‘flu shot. After that I had a low grade fever and muscle aches, then every 4 weeks again the low grade fever until after 4 months I felt better. So they certainly don’t agree with my system for sure.

    • Good grief! I see what you mean! I wonder if there’s an extra helping of magma trying to bully its way through or if the rifting has caused another partial blockage? Most of them seem to be at a depth between 12.8km and 10.4km. There are two more recent ones at 7.4km and 3.3km respectively. Hopefully those ones were off the ice. I’m interested to see if it moves forward at all.

  6. Hi everybody, I’ve been following you all for weeks now, it’s been very interesting to learn from you! Thanks for that!
    Now, maybe a bit off topic, but what are guys thinking of mount Etna?… It’s been huffing and puffing for some time, do you think there is more to come? Just wanna know because I’m travelling over there in 2 weeks!

    • Hekla has been unusually quiet lately. And it seems like the activity is slowly building up towards another paroxysm. But, remember that even if it has a paroxysm you will just get a nice show unless you are standing next to the mountain as it erupts.
      Have a nice bottle of wine and some cheese and bread and sit down and watch the show if it erupts! 🙂

      • Perhaps Hekla goes to sleep for 20 years (making next eruption around 2020) or perhaps it will sleep for 50 years.

        Something changed the pattern after 2000. And we know of something. The large SISZ quakes. But I don’t know whether that would be a reason.

        One thing I know: Hekla and large SISZ quakes seem to co-occur within a year of each other, in many ocasions since settlements. 2000 was last such co-occurance. But there are many on record. Sometimes Hekla is first, then the SISZ quakes, sometimes the other way around.

        Just to add that the largest ever recorded SISZ quakes were just months after Laki. So, SISZ can be triggered also after other events. Same story for Tjornes. 1975 Krafla starts. 1976 large quake in Tjornes.

        I wouldn’t be surprised the rifting in BB triggering some M6 quakes within the next 12 months either at SISZ or Tjornes.

        • I think volcanism is a bit stochastic. Highly sensitive to small changes in variables. Just like the weather Therefore, it is impossible to predict with accuracy as time goes on. But we can predict probabilities.

          Therefore, large nearby quakes can affect the high sensivity of such volcanic systems, and we find these co-occurances of the events I just spoke about. But sadly, they only occur, in case of Hekla and SISZ only 30% of the times. It is still a significant co-occurance, but not a direct correlation, so it can’t be predicted. Just that a Hekla eruption or a SISZ large quakes brings a 30% probability of the other event occuring too within a year.

    • With Etna there is always more to come, and she huffs and puffs most of the time. Of course, sometimes she takes one or two weeks off for recreation and beauty sleep… I cross my fingers that she is wide awake for your holiday, enjoy it! 🙂

      • Asking for a warning to go in here might not be best fot forward… after all we go on purpose to where there is an eruption 🙂

        But, what we are trying to say is that Etna is safe to watch if you are at a safe distance. It is the best tourist volcano there is. It is just that simple. And Boris Behncke and the rest at INGV are really good at what they do so you will be safe.

        • My thought exactly, Carl, I recommend a sunny spot on the terrazzo in Taormina with a nice espresso coffee, on a clear day. That should keep ash out of your hair while giving a good view of any paroxysms that might be on the way. There have been a lot of mag 3 quakes at 38km under Etna in the last few days so I would anticipate another push will reach the surface before long.

          Just speculating idly here, I know nuthin…

          Have a great trip Vanessa!

    • Either increased geothermal energy, which is a known fact. And that might be due to moving magma under the volcano. Or some human activity (like road repair or drilling geothermal exploration).

      • 4 days of 24 hour roadworks, sounds like the UK 😉 I was just curious since the activity pattern has returned to reykjanes ridge (4.7 and 4.8 a long way out) and it looks odd for the pattern to alter on this band only. Nothing activity wise, it was just the change of pattern that drew my attention.

          • Reykjanes is one of my bets for next “unexpected” eruptions in Iceland (within next couple of decades).

            Why? See my two comments I wrote today, the large earthquake swarms that ocasionally occur there, it’s a volcano that erupts actually quite often, recent geothermal increase there, and I had a dreamt about it erupting in the future (that’s the funny bit that makes me think about it)

            While we are all looking at BB, this might be next black swan.

  7. So around 05:00z this morning, there seemed to be an active flow from the vent towards the north. There also appeared to be lava fronts starting to fill the blanks in the middle and to the north of the lava covered area. Has there been any indications of how things went on during the day?

  8. Furthermore and now more scientifically. I was into something yesterday.

    I realized this. Let’s think in terms of energy release or desestabilization.
    And let’s think frequency (like frequent swarms). And their depth.

    Which part of Iceland was in 2009, early 2010, having deep and frequent swarms? Eyjafjallajokull.
    Which part of Iceland was, in last few years, having the highest frequency of earthquake swarms and frequently those quakes were deep? Kistufell and Bardarbunga.

    Also which part of Iceland had the highest number of M5 quakes recorded some decades ago? Bardarbunga caldera!

    Clearly these areas were long preparing for an eruption, and their signs were CLEAR and BIG.

    Let’s continue this thought:
    – Where else in Iceland do we see recurrent earthquake swarms?
    1) Askja and Herdubreid (so, a likely candidate for next eruption)
    2) Along Reykjanes peninsula (between Hengill and Krisuvik, and in Reykjanes tip), and there have been swarms up to M4.5, so remember what I said before.
    3) Katla
    4) Hamarinn

    We could say that these 4 spots are the next large eruptions of Iceland.

    Then, which other regions of Iceland have been having earthquake swarms and deep quaks, but less frequently:
    5) Kverfjoll
    6) Vatnsfjoll, south of Hekla
    7) Southeast of Langjokull

    So those 3 spots mark the other 3 most likely spots for a future significant eruption in Iceland. But either not as likely as the spots above, or not as large eruptions.

    Of course, Hekla and Grimsvotn do not count. As they are mostly asseismic in between their frequent eruptions.

      • No, southeast of Langjokull, means southeast of Prestahnukur system, north or northwest of Geysir, and south of Hveravellir system. This is just located close to Langjokull ice cap, westsouthwest of Hofsjokull.

  9. Pingback: It feels a bit soon for an update but… | Limestone and Lava

  10. Really? Have you ever worked in a construction environment? Try going out into your drive and drilling a circle of deep holes then expect the concrete in the middle to drop smoothly down, it doesn’t happen. Let alone 26 km of 2 km thick fused lava wall. If there was sufficient space between the “plug” and the volcano husk there would be escaping gas and magma boiling out. The Ice Is Melting. THAT is why it is linear. Look at the signs.. gentle up and down movements, sudden upsurge then a regular drop. lie a pressure cooker. The caldera base is probably being eaten away from below too. When the thickness of the base is less than the weight of ice above, and the fracture point is reached, the caldera may collapse. Until then then floor is fixed. Fused, interlocked for 1000’s of yrs. Not an elevator floating up and down.

    • In your example of drilling a circle of holes, there is still support from below to hold the weight of the concrete plug. If you were somehow removing dirt from underneath the concrete plug, it would start to sink. That’s what happens right now at Bardarbunga, when magma exits into the dike.

      Don’t think of a plug with smooth edges sitting in something like an elevator shaft. It’s just a huge mass of rock hanging on to other rock, like you say, fused and interlocked. When the supporting pressure from below is reduced, the weight is simply to much for the interlocked rock to hold. The rock is fractured and the “plug” moves down. The immense pressure is still enough to close the cracks so that no magma can escape up the sides of the plug. At least for now. If the rock is fractured enough, magma might be able to escape and start an eruption at the caldera’s edge.

      All the earthquakes registered at Bardarbunga’s caldera is simply this. Rock fractured as the “plug” sinks deeper down into the crust.

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