Bárðarbunga daily update 24-September-2014

This information is going to get outdated quickly.

Current status in Bárðarbunga volcano at 21:47 UTC

  • Eruption in Holuhraun continues at the same phase as yesterday. There is however just one or two crater erupting at the moment. New crater might open without warning if anything changes.
  • The lava field is now around 40 square km in size. It is now second largest lava field in Iceland at the moment. Largest lava field did come from Hekla volcano in 1947 in 13 month long eruption. It is expected if anything changes that Holuhraun lava field is going to reach 80 square km size in about two weeks (or one and a half) time.
  • Largest earthquake since midnight had the magnitude 5,2. Other earthquakes today have been smaller in magnitude.
  • Bárðarbunga caldera continues to subside around 50cm/day. Total subside is now around 27 meters.
  • The lava field is going over a path that has been used by geologist to get to the eruption. The path in question is called Gæsavatnaleið. At last check that lava field had around 200 meters until it was going to go over the road and close it permanently.
  • Earthquake activity is increasing in the dyke. This suggest that pressure is increasing inside the dyke. This also means there is high risk of an eruption in new location in the dyke, inducing under the glacier with everything that follows it (glacier flood, volcano ash and so on).
  • If eruption happens under the glacier the harmonic tremor is going to jump up and glacier flood is going to be visible soon after that. Depending on where the water is flowing under the glacier.
  • No major change has taken place today.

Other things

I am sorry for this late update today. I got a hardware to watch Icelandic Television in Denmark over the internet (IPTV). But the video kept freezing and it took a while to figure that out. Turns out the problem is my current router, it just can’t handle the traffic. So I had to get a new router that did cost me 103,78€. The new router is going to solve this problem for good. The last router that I did buy did cost me 25€, I had to buy cheap router since I was broke at that time.

Article updated at 22:06 UTC. Corrected numbers about the lava field size.

149 Replies to “Bárðarbunga daily update 24-September-2014”

  1. The lava field is now about 40 square km and about 0.4-0.5 cubic km.

    This is the second largest lava field that Iceland has seen in the last 150 years, the largest being Hekla in 1947.

    1. It’s also the third largest lava field in Iceland in 240 years, since Laki eruption.
      After Hekla 1947 and Hekla 1845, 0.5 km3 as compared t0 0.8 km3.

      It’s larger than two large rift events: the Askja 1875 and Trollhraun 1862 (each with 0.3 km3).

      Also it’s 6th largest eruption in Iceland in 240 years, after Askja 1875, Hekla 1847, Katla 1918, Hekla 1866, Grimsvotn 2011 (respectively 3km3, 1km3, 1km3, 0.8km3, 0.7km3). In a few weeks, it might become the second largest eruption after Laki, after the caldera event of Askja. Laki however was much larger with 15km3.

      1. And yet this volcano system erupted 60x the amount of magma then what it has so far done this time round. That eruption 8.500 years ago saw the largest lava flow on earth since the last major ice age… I wonder how long it took to erupt that amount of magma??

        Which ever way you look at it, this volcano has real potential for big fissure events.

    1. Harmonic tremor is basically low frequency vibration. It is a constant vibration caused by the movement of magma through rock.

  2. Many thanks for the up-date Jon, as always most informative. I have noticed that the EQ,s have been more frequent in the dyke area and have just had a look and noticed that some of them are very shallow 0.1km and 0.3km, do you think this is a bad sign and the magma could be very near the surface now.

    1. We already know that there is magma in the dike that is very near the surface because some of it is erupting. As to whether or not it will erupt in another location in addition to or instead of where it is erupting now is anyone’s guess but probability would argue “yes”. As of the last information given, the dike was still filling with magma at a faster rate than it is erupting so the probability is fairly good (though not “certain”) that an eruption at another point along the dike will occur.

      When? Nobody knows. Might not even happen at all. All of this could just stop tomorrow, or 5 minutes from now or a year from now.

      1. The magma trying to find a way and forming dykes is getting clear to me, (Thanks to everyone here and Jon offcourse, one has to admire his relentless efforts to educate and inform people.) the thing I haven’t been able to wrap my mind around is the dropping of the caldera of Bardarbunga and what wil happen if it will collaps.

        I get the fact that more magma is getting in to the system than is getting out through the current eruption, what will happen if an eruption occurs from underneath the glacier is still a bit foggy to me.

        (I’m sorry about any mistakes while writing in English, I usually speak Dutch.)

      2. “the thing I haven’t been able to wrap my mind around is the dropping of the caldera of Bardarbunga and what wil happen if it will collaps.”

        There is no certainty that the caldera IS collapsing. the ICE is. The surface of the ice might not be doing the same thing as the surface of the caldera under it. We might be weeks into an eruption under the surface or at least strong heating of the rock which is melting ice. Also, this time of year the surface of the glacier drops anyway as it melts from natural causes. Since we didn’t have a GPS unit on the surface before the eruption, we don’t know the rate it was dropping before this all started. And that ice is full of caves caused by melt water and crevasses. When a quake happens, some of those likely collapse and the ice compacts.

        I am not convinced with 100% certainty that what is happening at the surface is a mirror of what is happening at the crust under the ice.

      3. There is certainty the caldera is subsiding (not collapsing), based on the shape of the waves coming from the earthquakes, and ground penetrating radar. To my knowledge (which is limited) there is no evidence any water is melting yet over the caldera although there have been subglacial eruptions from the dike. Whether the surface subsidence is due to the known sinking of rock or the unknown sinking of ice is another question.

  3. Hello everybody, I have been reading this blog for quite some time, since 2010, for obvious reasons. 😉 Cam 2 looks pretty ominous today.

    @Catherine, I tend to look for things that I don’t really understand maybe try google things and ask more defined questions, http://en.wikipedia.org/wiki/Harmonic_tremor

    What is it you do not get about harmonic tremors?

    (I’m not trying to be mean or anything, I just don’t understand your question…)

    1. as I said I am new to this and had not heard the term before but yes in future will google to get up to speed – its many years since I studied earth science!

      1. I’m sorry I didn’t respond to this yesterday, WiFi decided to crash right after I posted these messages.

        I didn’t want to tell you that you can’t ask questions, we are all just guests in this blog and learn from the questions everybody asks and answers.

        Please do understand that English is not my language, I tried to ask you what you didn’t understand about tremors, I never wanted to tell you you should do research first but just tried to figure out what the question was. I really just wanted to help….

  4. “There is no such thing as a stupid question”
    Jon Frimann

    Yes, you can look up Wiki, but that does not give automatic understanding. I find the answers given on here far easier to understand, probably because of the underlining understanding that the commenters have, that a lot of new people are visiting here with a lot of questions.
    Hope they continue to take time and patience, with us. And I for one am very grateful to all of them.

  5. Hi Catherine. I too am quite new to here. You will learn much more here than you ever could by typing questions into google. Most people are very patient with our lack of knowledge and always helpful.

  6. (Sorry for my english 🙂 Thx Jon for all your nice work here! Since 2010 im looking on Vendur web-site, about Katla tremors… I just found your blog and it’s nice to have so mutch details about was is going-on on Bardarbunga! Good luck!

  7. The fissure looks to be doing a good job of providing a channel for upwelling magma and pressure. How likely is it that the fissure will be all that we see? The initial migration of EQs to the north also seems to indicate that the magma found the outlet it needed.

    Also, how do we know that there is more magma coming into the system than what is going out the fissure?

    1. The fissure is actually remarkably high pressure. For one set of vents to hold that volume and fountaining constant for weeks on end is most unusual.

      There is a very high risk of an additional fissure opening under the glacier south of the current crater. It would not surprise me if that happened at any time. Lots of rock-busting earthquake swarms and solid evidence that it already *has* erupted minorly a few times. This fissure might starve the first one or they might both erupt.

      The longer the subsidence goes on, the greater the risk of a much larger event in Bardarbunga caldera.

      They know about magma moving into the dyke from GPS. There is a lot of debate over how much magma is really there – usually on how much the official estimates are low.

  8. Greg B., that is a good question. It has been answered before by Jon in some of his previous blogs, which I hope someone is cataloging as to subject matter and which relevant question was answered. I agree with Mike, we should send along some money to Jon for all that he does. Is his blog not just as valuable and/or interesting as movie? Show your interest, then!

  9. How about rough probabilities of glacier flood eg 5pct within 1 month 25pct within 1 year any models or use gut feel thanks

    1. I suspect most of the professionals and amateurs at Jon’s levels are surprised that there hasn’t been a jökullhaup yet. Personally, I’d put it at better than 50% percentage that within the next month there will be “some” level of event. It may not be a bridge-killer, but there is meltwater under the Vatnajökull, and eventually it just come out.

      1. Thanks Mattmabus for prob. estimate.

        anyone else ??
        also interested in prob. of damaging flood, say within next month; and within next year.

  10. Fountains are less impressive tonight. Another thing I see is tremor plots still up for not so high wind in plenty of places. Something is going on here. I really believe the plots are showing more than wind noise.

    1. Only looks like one active fountain going. Lately there have been 2,3,4 of them going. I know there is some fog, but it’s not thick enough to blot out the bright fountain I’m seeing.

      1. Another one just 12 min ago. CSEN has it down as a m 5.0

        The earlier one seems bigger than m 1.1 that is listed in the IMO catalogue

      2. I am trying to figure out what happened to Böðvarshólar geophone. I lost contact with it last night. So there is no power to it or no 3G connection, or both. I am not sure. I hope to have it back up sometimes later today, or at the latest tomorrow.

  11. Ice under pressure is pliable. It does not crack but flows. Ice under less pressure can crack but does not release the same energy as cracking rock because it cannot store the same stress energy before breaking. All the EQs at 1km and more are due to rock movement and there are an awful lot of them in a ring formation around the caldera. Analysis of similar volcanoes shows the formation of a piston system with the caldera floor as the piston. Penetrating radar confirms the sinking of the caldera floor. The gps measurements also show inflation when magma inflow to the chamber exceeds outflow. The piston volume as measured by the gps drop correlates well with the lava volumes emitted from the fissure. There is no caldera eruption yet. When that happens we will all know. The argument that this is an ice only event is very weak indeed.

    1. No one who knows anything believes that the subsidence is somehow just in the glacier. That’s moonbat logic.

      Apart from everything else, say this with me: Water is incompressible. There is nowhere for the glacier to deform *to* absent space made by a descending caldera floor.

      The amount of subsidence made Carl on Volcano Cafe do a double-take when it first popped up through then-nonofficial channels, bu it’s real.

  12. Its good to have hunches and wishes. Emotional thinking keeps us motivated and creative and come up with new ideas. But those ideas have to stand up to criticism and cold hard logic in order to be real. Cant just go around believing stuff. Might make you happy but it is delusional and will let you down one day.

      1. Is it really necessary to post irrelevant links without a description? It’s frustrating as they generally take you away from this site and aren’t adding anything useful to the discussion. There are plenty of other places you can go and “play”.

  13. Just before the fog flowed in, on both Mila1 and Mila2, it looked to me like another vent opened up to the left and possibly in the distance past the main vent – anyone else notice that?

  14. In the initial stages of this event there was an assertion that water had traveled to grimsvotn. Is this still believed? Have heard little about this since here or on vc. Sounds important if true.

    1. I have not heard anything about that. It is the most logical option since nothing was observed elsewhere. We are going to get the answer once Grímsvötn empty them self of the water they hold. That might just take a long while until it happens.

    2. I think Ármann Höskuldsson said in one of his interviews, that it could well be that we won’t register the water, because it could just leave the glacier in small portions which we wouldn’t recognize as special melting water from these small eruptions, just drippling out by some of the rivers.

      Also Grímsvötn itself does not always empty its lake in big glacial runs, but also just by letting go regularly a bit of the water which is continuously collecting in the subglacial lakes (sort of balloons within the ice), because of continous melting from the geothermal system placed under the ice cap, sometimes also in small jökulhlaups of +100 m3/sec. – +1000 m3/sec.
      See eg. http://hal.univ-brest.fr/docs/00/48/06/76/PDF/Bjornsson_resume_3_.pdf (H. Björnsson: Jökulhlaups in Iceland: Sources, release and drainage. (2010)

      See eg. for Icelandic glaciers and their development: http://jardvis.hi.is/sites/jardvis.hi.is/files/Pdf_skjol/Jokull58_pdf/jokull58-bjornssonpalsson.pdf

  15. I am wondering if the fissue rifting event is bigger than what we realize? Take a look at http://en.vedur.is/media/vatnafar/joklar/medium/bb-mismunakort2014-2011.png where apparently a feature comes from the Bardarbunga caldera then makes a right angle joining the fissue rift which was well marked by quakes the past 4 weeks.

    If we look at the Vatnajokull quake page http://en.vedur.is/photos/jarvatj/140925_0635.png we can see a similar set of quakes just north and east of Askja which seems similar to those of Bardarbunga.

    Has anyone noticed this? Could we have rifting going on in both locations, only that near Askja has not broken to the surface as that at Holuhraun? The 3-d quake video seems to show much rifting taking place. See http://en.vedur.is/earthquakes-and-volcanism/articles/nr/2971#demo for this preliminary video.

    1. I think you mean the quake swarms near Herdubreid and Herdubreidartögl.

      There have been many quake swarms in this region in the last months and more. But I also thought that it looks a bit like a continuation of our Holuhraun dyke.

      And as far as I remember, also volcanologist Dave McGarvie, who has been working a lot in Iceland, saw this and commented somewhere (Twitter?) on it. He thought, it would be a possibility that the dyke had traversed the Askja region on the eastern side without problems – a.o. because there is also just mostly basalt there.

    1. Yes, with the exception of the conduit leading off to the side. Evidence from the holurhaun now suggest that the magma there is deep sourced and not from Bardarbunga. Experts suggest that the initial eruption was fed from Bardarbunga. My amateur mind notes from the analysis and lack of certain elements that it was deep sourced from the start with decompression melting accounting for the evolved magma composition but lacking in certain compounds.

      1. As far as I know “decompression melting” is always mantle material, so this couldn’t account for an “evolved magma”, it would mean the contrary. An “evolved magma”, on the other hand, would mean a magma type which is enriched by cristallisation processes, ie. which has been evolving (changing its composition) by a longer stay within a magma reservoir under the influences of high pressure and temperatures.

  16. There have been several posters recently asking about jokulhlaups or glacial floods. I have posted this youtube video before and I’m putting it in again for any interested persons who missed the first link –

    and this shows the aftermath

    The current events will almost certainly create such a flood somewhere, but nothing is certain with this event, we may be looking at one holurhaun eruption but the activity is over a truly massive area. Even for the best experts it is still a ‘best guess’ scenario.

    My best guess is it will happen North West side of Bardarbunga. My reasoning is that evidence suggests the unsymmetrical unbalanced ‘plug’ in Bardarbunga is tilting, the large eq’s are friction quakes as it bears down its massive (10km wide at its widest) weight on the upper magma chamber. A large number of these eq’s have been to one side of the caldera.

    The Vonaskard sil station is the most active and is being used by IMO as a reference point for the gps unit on Bardarbunga. The topography of the mountain has its steeper slopes at the NW and in my amateur mind that is the thinner wall on the ‘barrel’ and the weakest.

    1. The caldera is asymmetrical in that one side is much deeper than the other. I suspect that side is either much hotter right now or actually erupting. The eruption would be invisible on the surface, would be like an eruption 700 meters below the surface of the ocean.

      I really have a gut feeling that there is an eruption going on inside that caldera but there is no way for the water to escape.

      1. I agree there is an ongoing subglacial eruption. I have said before that (if funds had made equipment available) more gps units at N,W,S and E edges of the caldera ‘lid’ would be most informative. Such instrumentation would be a total loss in the case of an eruption though.

        I think it’s impossible to have this much movement of such an enourmous object as the ‘plug’ without there being action below the icecap.

        My worry, I guess, is that the upper magma chamber is in fact full, and the fall of the plug is hydraulic in nature compressing the contents of the upper chamber and pushing it into the lower chamber/asthenosphere. This in turn would mean the magma will be very fluid in the interaction zone. But crystalline towards the top.

        It’s all guessing 🙁

        The tectonics are showing the plates pulling this area apart and this can account for some but not all of the drop. Some magma will be pushed into fissures in the sides of bardarbunga.

  17. Thank you for your replies above – they confirmed my thinking, but I am such a rank amateur that I like to check on the way before losing the (more scientific) plot completely. 🙂

    OBC hen

  18. If there is a subglacial eruption in the caldera, then it must be small. For if it were a big subglacial eruption, then we’re probably not talking about water, but of steam. In that case pressure will go up, leading to explosions.

  19. question: On the caldera of 10 km in diameter is a GPS device which just gives us data. This can but 1 or 2 km further look very different. For example, in the northwest of the caldera where there is little earthquake.

    1. Correct which is why I comented above that it would have been great if 4 gps arrays had been set up. However, IMO on Iceland have limited budgets and these are very expensive devices which would be destroyed in an eruption.

  20. Hello from Germany

    Excellent and well done site with comprehensive Information. Keep up the good work

    Being a geologist, I did some research about volcano eruptions and its influence on the energy sector of Germany and other European Countries about two years ago.

    One interesting finding is, that – while large volcano eruptions were relatively common in the 18th and 19th century, Overall global volcano activity was comparatively calm during the 20th century. So a large volcano eruption VEI 5 or larger statistically is long overdue.

    Another important point is that new “green” regenerative energies like solar, wind and bio energy were not designed for prolonged periods of ash and dust ladden atmosphere and will be more or less useless during those times

    You can read the results of the research in a short paper (sorry…german language) , which you can find here:


    Comments are welcome



    1. It may indeed be important to maintain significant coalreserves to negotiate these periods.

  21. Thank you Crosspatch.

    “I am not convinced with 100% certainty that what is happening at the surface is a mirror of what is happening at the crust under the ice.”

    Are there detailed data about other volcanos that are not erupting at the moment? So hard to get facts straight if the only thing you are watching is the system that is causing trouble. Starting measurements and monitoring at the moment things are happening means there is no reference to the “normal”situation.

    The data they are collecting now is the situation from after the beginning of the eruption, I tried to find as much information about other, quiet, volcanos but could not find anything besides the standard things they usually check, did they do fly overs over other volcanoes? (I do realise that it is impossible to check on each and every volcano this closely all the time, there would be too much data and the costs would be enormous.)

  22. There have been several flyovers with penetrating Radar to measure the caldera floor. It is sinking.

    However…don’t laugh but in Andy maths a piston of radius 5000m dropping 27m is a bit over 2,000 million cubic meters. A dyke of about 50km long of 10km depth and half a meter wide has a volume of 250 million cubic meters. 1km cubed is 1,000 million cubic meters. So erupted volume plus dyke volume is 750 million cubic meters or less than half of the piston drop volume. Where did all the magma go ? Perhaps into expansion around the area ?

    1. In your measurements and calculations you only look at magma, not at ice and seasons, weather and earthquakes. You assume that this is not normal behaviour for Bardarbunga but how do you know?

      The in depth monitoring of an erupting volcano gives a lot of information, there is a lot going on and every hick-up, burp or shiver is analysed, categorised and recorded. There are things going on that might lead to an eruption, this doesn’t mean that everything that is recorded now is out of the ordinary.

      I believe Jon and the other scientists, they say it will likely eventually lead to bigger events, they look at volconoes all the time and see things that we don’t see because of that. I think your calculations have not all the data in it so it would be very hard to draw any conclusion from it. Some part of the dropping might be from ice, how much is from the volcano itself is not known as I understand from Jon and others.

      1. I am pretty sure that one of the IMO overflights during this episode first spotted a previously unseen subsidence in the caldera. Keep in mind that Iceland’s major glaciers are mapped and annual updates show where crevasses are currently located. I very much doubt a helicopter + scientists would have landed on a subsiding caldera and installed a GPS if what is going on now was not regarded as “out of the ordinary”.

    2. Interesting article in Vísir:

      – The sulphur release is extraordinary.
      – The eruption is also up to now not a small, but a big one (Magnús Tumi Gudmundsson).
      – The caldera has sunken by 27-28 m up to now (not the ice, see the following).
      And here is a translation error: In the original text it says “sig öskju”
      sig = deflation
      askja = caldera (öskju is the genitive).

  23. @Andrew Yes I know there is something sinking, offcourse this is out of the ordinary but what makes it sink? Just magma, or is the ice melting due to higher temperatures, or both? I never said there was nothing going on, the scientists would’t be worried if it was nothing. But do you know how Bardarbunga behaves itsself if there is no eruption?

    I responded to the calculations from Andy, he states that all off the sinking is because magma left the mountain, I sincerely doubt that.

    All of the measurements from the GPS are from the surface how many metres of ice are there on top of Bardarbunga? Assuming that everything is caused by magma leaving the system is, with the data we have now, not possible I think.

    @IngeB I do not read Islandic so I don’t know if the translation is correct, I assume an error would have been noticed and corrected. The glacier above the volcano is dropping at a steady rate, there is no doubt about that,

    1. Bárðarbunga volcano is getting lower because that is how caldera collapse works. It is going to stay up for as long there is magma to hold the caldera up. If there is a powerful eruption that empties the magma chamber, it is going to collapse. It has not yet happened, but I at least expect it to happen sometimes in the next months.

      1. Oh I absolutely agree with you on that one, the system is becoming pretty unstable, my point is that the drop we see at the top of the glacier might not be representeble for what is happening at the caldera, there is so much ice, so much weight and so little knowledge about how things look underneath. You ( I can’t that is why I am here, to learn a little more about it.) can make educated guesses but there are no certainties on which hard calculations can be made.

    1. No that is totally wrong. The Eruption is still VEI 0. The VEI Index is all about Tephra and an Eruption like Holuhraun isnt producing any Tephra

      1. Agreed. All these claims of “VEI_x” now!!!! Get annoying, purely because the scale only is trying to measure explosive release.

        That being said, its equally annoying to me that there doesn’t appear to be a scale to properly compare total magma erupted. Considering geologists and amateurs both try to do just this, why then, isn’t there a scale in use to properly do it with. *sigh*

      2. Considering the amount of SO2 emission ejected into the stratosphere, that could be a sort of Laki scale where Laki = 100. Laki was also a VEI 6 event btw.

      3. StridAst, for effusive eruptions you just use the DRE (dense-rock equivalent) expressed in units of volume, like km^3, which is how the volume of this eruption *is* generally being reported. There doesn’t have to be a snazzy logarithmic index for everything! 🙂

    1. Yes, the VEI index does just refer to explosive eruption, not to effusive ones like the one now ongoing in Holuhraun.

  24. Hi Jón thank you for all that you do.

    I thought I read one of your posts that the rim of Bardarbunga caldera is showing signs of uplift while the center of the caldera collapses. Would this suggest that the roof of the caldera is actually heating and melting in on itself due to fresh magma intrusion from the mantle, rather than the magma chamber emptying and the caldera roof settling (collapsing) to occupy the space that would be voided by the erupting magma?

    I’m curious as to your thoughts on this.

  25. Do you think that when the caldera collapses that it could leave an empty chamber behind like the one somewhere else in Iceland that you can go into in a lift?

  26. I am enjoying this whole experience — watching the webcam and reading this blog. I’m in Washington DC and we have no glaciers or volcanos. I did not know any of this vocabulary. I discovered the webcam by accident and have been watching it for weeks. I leave a window open on my desktop while I write. Aside from the eruptions, the beautiful part has been watching the sun rise and set.

    I do not know the blogger at all and this is unsolicited request. Please donate as a small token of appreciation. If you have a Paypal it is very easy. US10.00 is ~EU13.00.

    Now if I can figure out the Captcha, you can read this appreciation! [added note: switched browsers because after ~10 tries and “incorrect Captcha” I gave up. Trying Firefox. If you see this it worked.]

      1. Thanks so much, Jon, for pointing out the location. Sad to admit I’m that blind- but happy to finally be registered.
        Thank you for all you do!

  27. I am wondering, how strong the tourists at Jökulsarlon are feeling a mag 5+ -quake at Bardarbunga. Tectonic quakes of this mag are generally recognized over a fairly large distance. Are ground movements of a volcanic event confined to a narrow realm?
    I never happened to see steady webcams like Bardar-1 or Jökulsarlon shake from an eq.
    Did anyone else do?

    1. Probably detectable, but not enough to stop you buying tea and cake from the nice people in the shop there. Cheapest cup of tea I’ve ever had in Iceland was in there last April 🙂

  28. Radar is accurate. Not worth running after the unknown when radar gives accurate caldera floor measurements.

  29. I keep seeing posts about the caldera and the amount it has dropped. There has been suggestions that it is not dropping and that it is the ice compressing of shaking down or melting. Last week there was a link here showing the Ground penetrating radar data that clearly showed that the caldera floor was sinking. There was also the GPS data from on top of the ice and when compared there was very little variation between them. Jon has said many times that the caldera is sinking and has put links up to prove this. Seasonal melt ect has nothing to do with what is going on.

  30. “Last week there was a link here showing the Ground penetrating radar data that clearly showed that the caldera floor was sinking. ”

    I saw a link of ground penetrating radar but I did not see where they ascribed any specific amount of drop. Also, I don’t believe the radar will penetrate to the bottom of the caldera (though it might), the pictures I saw were of the area outside the caldera where the ice is thinner.

    Do you have a link?

      1. not clear on why this clears up the Ice Surface vs. Ice Bottom debate. it does not specify what they were profiling with the airborne radar (can radar even go through 700 meters of ice ??) (unless it is hid the Icelandic labels on the plot …)

      1. As far as depth it can map, the oil industry have used Airborne GPR to map large areas down 1000’s of feet.

      2. @Clive:
        I am in the oil industry. We use mostly seismic, and occasionally electrical methods such as magnetotellurics (and gravity/magnetics) to go down 1000s of feet in the earth, but not GPR ( the skin depth effect kills radar penetration)

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