Changes in Bárdarbunga Caldera

Image of the Holuhraun eruption taken by the Volcanocafé Productions Film expedition to Bárdarbunga. This image is from the upcoming film by Eggert Norddahl, Bergsveinn Norddahl and Nick Small. Produced by Volcanocafé.

Image of the Holuhraun eruptionCredit: Eggert Norddahl, Bergsveinn Norddahl 

During a scientific over flight a marked and unexpected drop was noticed in the caldera floor of the Bárdarbunga Central Volcano. The drop was 15 meters, and is as such the largest deformation of a caldera in Iceland. It is interpreted as the result of magma leaving the magmatic reservoir under the caldera floor.

If this number is valid for all of the 11 by 7km caldera it equals to a volume of drained magma of 808 million cubic meters, or just shy of a cubic kilometer. This does not take into account magma that has come into the system during this episode

Image of the Holuhraun eruption taken by the Volcanocafé Productions Film expedition to Bárdarbunga. This image is from the upcoming film by Eggert Norddahl, Bergsveinn Norddahl and Nick Small. Produced by Volcanocafé.

Image of the Holuhraun eruption taken Eggert Norddahl, Bergsveinn Norddahl 

.Now, where has all of this magma gone? Well between one quarter and one third has erupted out through the fissures. The current estimate is that between 250 and 300 million cubic meters have come out of all of the fissures so far. And that would leave between 500 and 750 million cubic meters inside the rifting fissure extending from Bárdarbunga Central Volcano.

A short note on the diminished amount of earthquakes. This is fully to be expected since the earthquakes are mainly a sign of increased pressure in a fissure system as magma pushes apart rock. Now that the fissures have opened the pressure will be more constant and no new rock would need to be ripped apart by the magma.

So far at Volcanocafé we have been able to keep ahead of the eruption at Bárdarbunga. We were the first in the world to publish information about the upcoming unrest of Bárdarbunga before the earthquake swarm started; we accurately predicted the most likely scenario with the following eruption. As did we do with what now has been confirmed to be happening at the caldera.

Image of the Holuhraun lava field taken by the Volcanocafé Productions Film expedition to Bárdarbunga. This image is from the upcoming film by Eggert Norddahl, Bergsveinn Norddahl and Nick Small. Produced by Volcanocafé.

Image of the Holuhraun lava field Credit:Eggert Norddahl, Bergsveinn Norddahl

So, what will most likely happen at the caldera? For starters, it is normal for rapidly deflating large magma chambers to cause deflation caldera formations. Normally this does not lead to an eruption, or lead to just small eruptions since a deflating caldera floor is a sign of loss of pressure.

In this case we need to take into account that there are two large pools of water below the ice over the caldera floor, and that the ice in and of itself can rapidly transform into water. If that water finds a way down into the extremely hot magma reservoir the water will instantly transform into supercritical steam and a steam explosion will occur. In that case pure physics take over; if a small amount of water hits a small area of hot material a fairly benign explosive event happens. If a large amount of water hits a small area of hot material a prolonged event follows. If a small amount of water hits a large area of hot material a short rapid explosive event happens. And if a large amount of water finds a large area of warm material I would prefer to be more than 50 kilometers away.

Image of the Holuhraun eruption taken by the Volcanocafé Productions Film expedition to Bárdarbunga. This image is from the upcoming film by Eggert Norddahl, Bergsveinn Norddahl and Nick Small. Produced by Volcanocafé.

Image of the Holuhraun eruption taken by  Eggert Norddahl, Bergsveinn Norddahl 

Now that we have covered the options of water dumping into the magma reservoir we should briefly discus Jökulhlaups. For Bárdarbunga it would take quite a lot for it to cause a Jökulhlaup directly from an explosive event at the Caldera since there is not natural way for the water to leave. So, a lot of new water would need to be melted for that to happen. So either a prolonged event or a very large scale event would be needed.

As usual, follow the warnings from the Icelandic Authorities; they are the best on the planet at handling situations like this.



Correction:  In a recently published article on volcanic gasses, I stated that volcanic ash could cause silicosis.  Upon further review of the information out there, I found that this is unlikely.  While volcanic ash is mostly silica, the most toxic form, (fine, crystalline silica,) is rarely abundant in volcanic ash.  It would take years of exposure to crystalline silica rich ash to develop silicosis.  Those with preexisting lung diseases, such as asthma, may be more prone to problems, up to and including death.  Additionally, there is some evidence that children exposed to ash may be more prone to asthma.  However, healthy individuals are unlikely to experience anything more than bronchitis-like symptoms.

The pertinent information on volcanic ash toxicity is presented here:


1,525 thoughts on “Changes in Bárdarbunga Caldera

  1. Your mirror has worked so fine for me, Tom, thank you for putting it up. The forbidden links often don’t work here.


  2. Previously I’ve posted overlays of the quakes and cauldron on top of the topo map that Desert Rat posted and the Landsat image that Bjarki posted. This is a combination of the two. It doesn’t show the same level of detail (look at the originals for that), but it does give an overview and shows the sheer scale of the area we’re looking at and how the eruption sites and lava field are tiny compared to Bardarbunga. The alignment isn’t perfect and it looks a little messy, but I think it is good enough.

    • It’s amazing that I just found your site today. As soon as I found it I Tweeted it to my followers because your work far exceeds what I have done. I am not a Vulcanologist, however I have been studying volcanoes and earthquakes and their relationship to Climate Change for over eleven (11) years now. I have been concerned greatly in regard this series of eruptions and recently wrote an article on my site laying out the historical danger that Bardarbunga could pose to the entire Global Community if it experiences a major eruption. If Bardarbunga does experience even a moderate eruption we could easily experience a year or two without a summer and that would be disastrous. A huge eruption as it has erupted before that is a VE-6 would be unimaginable to me and even though I believe it could happen, I hope that I am wrong.

      Again, you folks are going a great job and my hat is off to you for an eye-opening experience. I’ll be a regular visitor from this date forward.


    Please correct me if I am wrong, but with 15.9 km2 covered by lava since the eruption started, assuming an average depth of 0.33 m, which I think would be rather shallow, wouldn’t it mean that more than 5 km3 of magma have already been erupted?

  4. Average depth let’s say 10m:
    16 km2 x 0.010 = 0.16 km3 which is as much as Eyjafjalljokull, roughly. And average small fissure eruption.

    If it keeps for more 10weeks, then it could make up to 1 or 2 km3, which is a nice size for a flood basalt, quite common in Iceland.

    At maximum, if it keeps for 1 year, it would make 0.16 x 52 = 8 km3, about half of Laki.

  5. If one looks at the speed at which the lava has been growing since the third it could make quite a different volume over time. 6,8 Km2 in the last three days w. the same thickness (10 m. avg.) would give 0.023 km3 growth a day.
    Or 8,4 km3 a year.

    5 m. avg. growth gives 4,2 km3 in a year

    10 m. avg. growth gives 8,4 km3 in a year.

    15 m. avg. growht gives 12,6 km3 a year.

    And so on.

    Just numbers, but maybe someone could make some graphs? And add SO2-release based on known output?

  6. Ok, here’s a question in regards to the Jökulhlaup. If there is one, and it comes down into the lava fields, Holuhraun, where the current fissure eruption is happening. Carl said that the flood would be equvilant to the flow of several Amazon rivers at coming at once. So, if that comes into Holuhraun, it would seem to me, that it would also flow into the erupting fissure. What happens then? Enough water to put out the eruption at the fissure (some reason, I think no) or would it cause a massive eruption possibly unzipping the dyke and causing a bad situation to become worse?

    • Okay, first of all, an eruption is not fire instead it is molten rock poured out, so water will not put it out. Instead the eruption would change in nature and become explosive and we would get ash.
      And it would not cause a massive eruption. The output of magma would stay the same.

    • I think so, I saw them too…

      And, I can now confirm the numbers by sCyborg, the larger fire fountains are in excess of 250 meters. I did the trigonometry after getting the angles.

      • Converted to the Eiffel Tower scale, that’s at least 10/13 Eiffel Tower.

        (sCyborgs high estimate would be 1 1/4 Eiffel Tower.)

    • And a bit of trigonometry on that one gives at hand that the average thickness is 30 meters. That river will be a lake by tomorrow.

        • It was 0,24 3 days ago, so that sounds quite right.
          Remember that the average thickness I gave is at the outer tongue, I would suspect the lava is thicker closer to the fissure since it is layered up there.

          • 0,24 km3 in just three days? That is a lot of goo…. In a year that would accumulate to 29,2 km3 in a year. Or apx. 2 times Laki. Are you sure?

            • @DracoPyrite; do we know anything about the openings themselves? If the fissureopening at laki was narrower, then a higher fountain might have been produced given the same pressure (?) Think of two different sized hoses from the same pressuresource. A 2″ hose would give a smaller fountain then a 1/2″ hose given the same pressure. Correct?

              So the case might be that the rift/opening is much wider here than it was when Laki erupted. ???

      • Did they give a figure to the depth of the layer flow exposed at the new graben ?

        didn’t look that thick…closer to 10-12 meters.

        so the older fissure eruption was less effusive ?

        • The first fissure that closed down was a mini compared to the big one. Also the two new ones (that also seem to have closed down) are also tiny in comparison.

  7. Are there fish in that river down stream ? maybe a salmon run goes up it. Could poisons leach out of the lava and kill aquatic life down stream ?

    • Yes, most likely it will kill most of the fish. But the salmon run has been allready so no worries about the salmon.
      This happens now and then, but the fish always come back when the poison has been flushed out by the water.

        • But, if there is poison leached out into the water in sufficient quanitities it would whack the fish below dettifoss also.

          And, not to forget that there is quite a chance that the hraun will dam the river sufficiently to drown the fish on dry land so to speak. Will be interesting to see a dry Dettifoss.

          • Yes, this fascinate me, the rivers will change, new lakes will form, the nature will show us this right now. And this is permanent!

            • Yes Mizar, this is what I find so interesting in this scenario also, the changing topography of the land. I was wondering if the river could eventually even find another way through to the sea. Then I realise that would be very doubtful as there are so many mountains and valleys which will likely keep it to the same channels.

              When this eruption first started I was a little disappointed not to get a ‘real’ volcano. Now I realise this is far more of a treat, far less dangerous and a real delight to the eye. Instead of just getting smoke and steam out the top of a mountain and almost no sign of lava as at Eyjafjatlajokull, we are seeing lava fountains in abundance and a massive outpouring of lava flows to delight us. As beautiful as Hawaii with no danger to people. Just wonderful I feel.

          • Dettifoss will not dry out since a large part of the river is the tributary Kreppa that joins in opposite of Herdubreidarlindir, also I think it will be a while before you see a complete dam, the river is already finding ways to flow further east of this main channel, Look at the photo how the water is spreding towards the right) if you look at maps you will see a small branch of the river quite aways east of this one -it will take over that channel as soon as this one is shut down I presume, there is hardly any height difference.

            • Jökulsá á Fjöllum´s flow is also buffered by rainwater and snowmelt percolating through Ódáðahraun, there will be some flow down river for decades even if the upstream were completely blocked. By the time you get to Dettifoss there are a lot of sources for the flow, not just the root tributaries from the glacier.

        • But these are Icelandic salmon. tough guys, they wouldn’t be stopped by a little bump in the river like Dettifoss would they?

    • That video though was shot on the 4th Sept. Todays lava fountains, particularly the middle crater, seems very much higher to me but that is just watching the cams.

      • Also this seems much higher because we can see this one clearly even during the daytime and through the smoke. Obviously not too much smoke though! 😉

    • That was three days ago – narrator says 4th of September, and that they are about 500m away. They are probably bigger now.
      One of the smaller lava outlets starts to produce ash on the video, I think he says it was weak and got occluded.

          • Thank you! Being an accountant, I never had physics courses, so I’m frantically googling a lot these days. Q. Daniels’ and your assistance is greatly appreciated.

          • Glad I could help, and thanks for pointing out the explanation I omitted.

            I’ll note that others at VC have previously used the same method. All I did was write it out.

            • . . . which enabled me to do future estimations myself. Don’t diminish the significance of that. The difference between giving a person a fish and teaching a person to fish. You just taught me to fish. (And your humility is admirable, BTW.) Now, back to The Bard.

    • At about 1:52 in this video, the videographer zooms in on a lava formation that looks quite like a shark fin with a bite out of it. The formation rises up much higher than the rest of the lava. I think I recall that rhyolite in lava tends to pile up into towers, and the mineral analysis of the lava said it contained some rhyolite, but other sources say there is no rhyolite. Is there rhyolite in the lava?

  8. Cloaking off.

    Taking advantage of a quiet spell in the action, a wannabe from darkest Wiltshire here to thank the Dragons for the only blog in Known Space whose comment section isn’t a knowledge-free zone. And a special thank you, too, to Tom-Helge Andersen for the mirror webcam feed which most of the time is the only one I can get.

    At uni many score moons ago I tried to sell my soul to become a ologist rather than a olic but there were no takers. In my department if you could damage it with a hammer it was gardening not geology – oldy but goody. So I’ve lurked silently and seethed with jealousy, and whacked many a passing rock, ever since.

    I think we should sue somebody as it is blatant discrimination that Iceland has more than one volcano while we have none. There’s a big blank area in Wiltshire where we could easily put one, a small one anyway; but even an explosive one would be ok as the only town that could be damaged is in dire need of improvements. I’ve approached the county planners about this matter but they don’t seem to return my calls any more. C’est la vie.

    Back to ogling the lovely hunk of pumice on my mantelpiece which I picked up somewhere near Askja some aeons ago; it weighs no more than a whisper.

    Dragons, commenters, lurkers, please Keep calm and carry on.

    Cloaking on.

      • yeah i still really can’t to seem to wrap my mind around it. it’s so daunting.

        went on to try and find some sort of comparison for seeing the buildings at a distance of 15 to 20 KM since that’s about the distance in between the cam and fissure :\

  9. Hello Volcano Cafe! I finally stick my nose in the door, after being a habitual lurker since Eyjafjallajokull did her dance in 2010. Thank you for the most excellent coverage and commentary, not to mention the occasional outbursts of volcanoholic humor! I am curious, how does this current eruption now compare with Krafla, as far as volume and coverage, and whatever happened to the camera at Kverkfjoll? It should cover some of the lava flows. Thanks!

    • ❤ ❤ <3. (With the caveat that if this event starts to cause human suffering, my ❤ will be moved to 😦 and providing disaster relief for anyone affected.)

  10. Mila 1. Looks as if the fires from all the vents have joined together, and the lava stream on the ground is glowing

    • Tiger, tiger, burning bright. . . guess everyone but me is off drinking beer. I’m drinking beer too and editing a book on paper so the screen is Mila.

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