When Is a Caldera a Caldera?

Volcano? Erm... I don't see a volcano? Toba caldera wall seen from Samosir Island, a resurgent dome near the middle of the caldera. (Photo, Sebastian Hubarat, Tobaexplorer)

Volcano? Erm… I don’t see any volcano? Toba caldera wall seen from Samosir Island, a resurgent dome near the middle of the caldera. (Photo, Sebastian Hubarat, Tobaexplorer)

It does not take long for a newcomer to volcano-watching, if we are to call our hobby that, to come across the term “caldera”, cauldron. The term is very loosely used to describe large volcanic depressions ranging from volcanic craters a few hundred metres in diameter up to the huge depressions left behind by the very largest volcanic eruptions that may approach 100 km in their greatest extent. Consciously or subconsciously, there is always a sensationalist undertone evoked in the reader when the term caldera is used, so what is a caldera?

The archetypal caldera is Yellowstone. For many decades, scientists had realised that Yellowstone was a large volcanic feature with its geyser fields, tuffs and lava flows, but where was the volcano? There was no sign of it! It wasn’t until the advent of Space flight and high resolution orbital photography that the truth was finally realised: Yellowstone and its major explosive eruptions were so huge that the volcanic scars left were too large to leave a recognisable volcano behind. Almost wherever one is in Yellowstone National Park, one is standing on top of the volcano. Let us just add immediately that the vast majority of its volcanic or volcano-related eruptions are nowhere near huge, that there is no periodicity to the largest, caldera-forming eruptions and that Yellowstone is in no way “overdue”, whatever Michio Kaku or Steve Quayle may say.

The trail of "supervolcanic" eruptions across the state of Idaho and through the Rockies known as the Snake River Plain (ISU)

The trail of “supervolcanic” eruptions across the state of Idaho and through the Rockies known as the Snake River Plain (ISU)

With this epiphany, the scars left behind by several more such very large eruptions were identified. West of Yellowstone running through the state of Idaho and cutting a swathe through the Rockies lies the Snake River Plain, a trail of at least seven calderas left behind by several ultra-colossal (VEI 8), nowadays sometimes referred to as apocalyptic eruptions, and mega-colossal (VEI 7) eruptions dating as far back as 16 million years as the North American plate travelled over the Yellowstone hotspot. It can be traced back to the Columbia River Flood Basalts in Oregon, a large igneous province formed over a period of 10 – 15 million years and most vigorous 17 – 14 million years ago that deposited some 174,300 km3 over an area of 163,700 km2 with a maximum thickness of over 1.8 km. This is not the only area in the USA where such eruptions have occurred. Long Valley in California was home to a mega-colossal VEI 7 eruption about 760,000 BP. The Valles Caldera, New Mexico, was formed by two VEI 7 eruptions some 1.15 million years ago. What has long been regarded as the largest eruption ever identified is the massive VEI 8 eruption of 27.8 million years ago that formed the La Garita Caldera and Fish Canyon Tuff in Colorado.

Interesting though the American caldera-forming eruptions are, they are not unique, nor are they the most interesting. The Atana Ignimbrite eruption (VEI 8) that formed the Pacana Caldera in Northern Chile some 4.0 million years ago was as large as the largest of Yellowstone’s eruptions. Lake Toba in Sumatra Indonesia was even larger, occurred as recently as 74,000 BP, and is somewhat controversially linked to a bottle-neck in the human genome. If true, the Toba Catastrophe Theory claims that as many as 60% of all humans on Earth at the time could have perished. The 74,000 BP Toba Eruption was preceded by at least one other VEI 8 and two VEI 7 eruptions dating as far back as c 1.2 million years. Subsequent to the most recent eruption, a resurgent dome, Samosir Island, has appeared.

Beautiful Lake Taupo, New Zealand. The only hint of its volcanic origin are the distant volcanoes on the horizon, built at the edges of the ring fault system. (Provenance unknown)

Beautiful Lake Taupo, New Zealand. The only hint of its volcanic origin are the distant volcanoes on the horizon, built at the edges of the ring fault system. (Provenance unknown)

No disrespect to the USA, but the undisputed World Champion of ultra-colossal and mega-colossal eruptions is the Taupo Volcanic Zone located on New Zealand’s North Island. Over a period from 280,000 BP to as late as 1,800 years ago, the TVZ has seen no less than two VEI 8 and five VEI 7 eruptions. The latest of those two are the Oruanui Eruption (VEI 8) 26,500 BP and the Hatepe Eruption (VEI 7) 1,800 BP of Lake Taupo.
Other recent mega-colossal eruptions that formed large calderas include the 3,600 BP civilisation-destroying eruption of Thera (Santorini) from which we have derived words such as “terrible”, “terrific” and the Tera of terawatt/terabyte as well as the legend of Atlantis. It may well be mentioned in the Biblical description of the Plagues of Egypt. Two further recent such eruptions are the Kikai Caldera, Ryukyu Islands, Japan (6300BP)and Macauley Island in the Kermendec Islands, New Zealand(6,300BP) eruptions. In addition, there have been two recent VEI 7 eruptions that did not lead to a caldera collapse even if the huge summit craters, partially the result of collapse, are often referred to as “calderas”, by scientist – Mount Baekdu/Changbaishan (969 AD) North Korea-China border and Tambora, Sumbawa Island, Indonesia (1815 AD) that caused “The Year Without a Summer”, 1816.

Mount Baekdu or Changbaishan on the Chinese - North Korean border, source of the 969 AD VEI 7 eruption (Wiki)

Mount Baekdu or Changbaishan on the Chinese – North Korean border, source of the 969 AD VEI 7 eruption (Wiki)

These very largest of volcanic eruptions begin with an initial eruption that removes a sufficient amount of magma that the ~5 ~ 10 km thick roof over the magma reservoir begins to buckle and drop. This forms a series of concentric ring fractures which eventually begin to erupt after which the now unsupported roof collapses into the magma reservoir leading to the major and usually tuff-forming ignimbrite eruption which partially fills the caldera. Later eruptions and erosion further fills in the caldera and intrusions thousands of years later may cause a resurgent dome to emerge near the middle. Note that neither Baekdu nor Tambora fit this pattern for caldera formation very well as the progenitor volcanoes survived!

In comparison to these giant scars, often tens and several tens of kilometres in extent, it seems ridiculous to refer to the 1½ km wide, shallow summit crater of Iceland’s Eyjafjallajökull, a volcano that gently spews out no more than some 0.1 cubic kilometres or so over a period of months with its eruptions, as a “caldera”, but unfortunately even scientists do in serious academic papers.

The 3 x 4½ km summit caldera of Mount Katmai, Alaska, that formed after the 1912 VEI 6 Novarupta eruption (Wiki)

The 3 x 4½ km summit caldera of Mount Katmai, Alaska, that formed after the 1912 VEI 6 Novarupta eruption (Wiki)

But the very large, ultra- and mega-colossal, eruptions are not the only eruptions to form collapse calderas. In addition to this, there are relatively speaking smaller eruptions that form them, mostly from the colossal VEI 6 eruptions. The most recent such example is the 1912 VEI 6 Novarupta eruption when the magma reservoir under the Katmai volcano, Alaska, emptied through a new vent well to the side of the volcano to form the “Valley of Ten Thousand Smokes”. Over the next few years, much of the edifice of the Katmai volcano collapsed into the emptied magma chamber to form a 3 x 4½ km summit caldera.
A better known and researched caldera-forming eruption is that of Mount Mazama (7,700 BP), Oregon. This followed the pattern of a ring fault forming followed by an eruption at the ring fault and the collapse of the volcanic edifice into the relatively shallowly located and emptied magma reservoir. The caldera has been filled with water to form the 8.0 x 9.7 km diameter Crater Lake and, in contrast to the non-eruptive resurgent domes of very large calderas, subsequent eruptive activity has built a central cone, Wizard Island.

Topographical map of the Crater Lake caldera showing the features of subsequent intra-caldera eruptions. (USGS)

Topographical map of the Crater Lake caldera showing the features of subsequent intra-caldera eruptions. (USGS)

Calderas such as these are plentiful. Europe alone, perhaps not noted for great volcanic eruptions, has several; Laacher See in Germany, Vulsini, Colli Albani, Roccamonfina in Italy, the Rodalquilar Caldera complex in Spain to name but a few. In addition there are several ancient ones such as the caldera complex upon which Oslo, the capital of Norway, is built, Mount Snowdon & the Lake District, UK, etc. etc.

But there is one type of caldera that defies the traditional description and which is impossible to tie down to a single, specific event and that is best exemplified by the large Icelandic calderas of subglacial origin, i.e. Katla and Askja. While it is thought that the calderas of both Torfájökull and Tindfjallajökull are the result of single large, possibly VEI 6 eruptions, some 50-70,000 years ago, those of Katla, Askja and the volcanoes below both Hofsjökull and Langjökull are much harder to explain in those terms. The calderas of both Askja and Katla are far larger than can be explained by eruptions known to have occurred from analysis of ash strata. Both volcanoes seem to be limited to no more than medium-sized VEI 5 eruptions whereas in both cases, at least a low-end VEI 7 – which we know never has happened – would be required to produce their large calderas. It is here that what we are now seeing at Bardarbunga might have a bearing.

Aerial photograph of the sub-glacially formed Askja volcano with its large caldera containing the nested caldera of Lake Öskjuvötn, which resulted from post-eruption collapse following the volcano's 1875 VEI 5 eruption (RUV)

Aerial photograph of the sub-glacially formed Askja volcano with its large caldera containing the nested caldera of Lake Öskjuvötn, which resulted from post-eruption collapse following the volcano’s 1875 VEI 5 eruption (RUV)

That Bardarbunga is now undergoing a collapse event is beyond question. Furthermore, to judge by previous eruptions in the area emanating from or involving this central volcano, this is not the first such time in its history. Until this eruption started, the caldera as shown on the IMO maps was significantly smaller but was enlarged to its current extent by human reinterpretation. The collation of earthquake data by VC-reader Albert strongly suggests that a collapse event is happening at the N to NNW margin of the newly defined caldera where the data indicates that the deep magma reservoir extends beyond the limits of the “rescheduled” caldera. If this continues, the caldera will eventually be enlarged in this direction.

If this is indeed what is currently happening and has happened before, we may have obtained a vital clue as to how and why the Icelandic subglacial calderas defy the correlation between the size of the caldera and the eruptions that formed them.

/ Pyrite

Some further reading:

Yellowstone –

Toba –

Tondano, Indonesia –

Taupo Volcanic Zone –

Campi Flegrei/Vesuvius –

Calderas of Southern Japan –

Central Kamchatkan Depression –

Atitlán, Guatemala –

Thera/Santorini –

Katmai & Novarupta –

Laacher See –

Vulsini caldera complex –

Roccamonfina –

Rodalquilar Caldera complex –

Mt Snowdon –

Okmok Caldera –

The Onekotan Voclanic Complex –

Rabaul –

Taal, Philippines –

San Juan Volcanic Field (La Garita) part of the article:

April Fools Joke –


1,488 thoughts on “When Is a Caldera a Caldera?

  1. Comparison of landscape today on left, and 22nd Sept on right. One tributary obliterated by lava, and the second relocated to the east somewhat. Look at the glacier behind for reference points. And no R2D2 😦

    • Yeah, I am waiting for the lake to form. Now the lava is moving in a direction where there is a low hill on the other side.

        • And on that note, time for me to eat and go to bed… bloody Ebola has struck…
          Shivers, coughing, the works… Feels like Ebola, looks like Ebola, must be Ebola… 😦

          • Don’t joke about Ebola, Carl. People where I work have gone out to Guinea, Liberia and Sierra Leone to help contain the epidemic. They are putting their lives on the line every minute they work. It’s a truly scary disease. (Hope you get better soon, by the way!)

            • It is not a decease to joke about if you have it. But, joking about bad things is good and helps to put things into perspective.
              And FYI, I have worked with Ebola helping to track its origin. Obviously far from my speciality and I mostly carried things and caught african fruit bats, but I have been amply in contact with the live item.
              And, I have enough knowledge about the decease to know that it is more of an health education problem than a world threat.

            • Oh Carl’s been out there too, collecting blood samples from fruit bats so it’s a perfectly reasonable fear on his part. My father used to be a doctor too, (not physics, medicine) and whenever a family member was struck down with fever as high as >41C (106F) it was nobbut the common cold. Should he, God forbid, suffer from a slightly congested throat it was a) a disease unknown to medicine, b) 100% fatal, and c) there was no known cure. I’ve lost count of the number of times he was convinced he had contracted Lhasa Fever and Bubonic Plague…

            • Ditto Talla…we must work in the same business. You are right that it is nothing to joke about. I have colleagues down in Dallas and some off to Sierra Leone as well.

            • I know you’ve been there, Carl. Me too, I’ve had malaria, bilharzia and something unknown that lasted a year when I was a child and never was diagnosed. But haemorragic fevers are very nasty indeed and even though it’s far away, it’s also only a plane flight away. And stay away from bush meat! 🙂

            • @Pyrite, All doctors are hypochondriacs but don’t dare think that way if you are a patient! Probably why an awful lot of doctors drink too much.
              As for Ebola, a very scary disease! They say not transmitted in the air, however I did read up about an experiment with infecting monkeys with it. The infected ones mostly died, the non-infected control group where on the other side of the room and supposed to be no actual contact. Some of those monkeys contracted the disease too! So either someone wasn’t following proper sterile procedures or else be scared, be very scared! Especially as some scientists are saying they are worried virus will mutate. Is this a warning? I truly hope not but seriously wish everyone returning from an infected country was put into quarantine. Also hope they make a better job of the quarantine than US.
              Sorry for OT post but Carl almost invited it.

          • I think you should consider another rule: Don’t die. I’ve always insisted on that one wherever I’ve worked. 🙂

        • Carl…Now, one’s and for all, you have long lost your chance to see me in a thong, ….there was a time factor that ran it’s course 2-3 weeks ago and you lost. So I now know your caliber and like a good sport I release small fry of the hook. So now you can start sleeping again at night. Even though no lake forms. (when the lava hits the small hill the river will flow on the other side of the hill. You need to come up and study how our glacial rivers work. (i would however like to thank you Carl for giving me the idea, the wife loves my pink thongs!)

          • I am happy that Mrs JayBee loves the pink thongs.
            But, as I have stated prior to this. I never gave a time frame. And, FYI, I have actually been in Iceland.

            • I appreciate that the mighty dragon is well acquainted with fire and flames, but it is no suprise that water is not a strong subject for the flame breathing beast. I actually knew you have been in Iceland as you have written very informative articles on it. But I still believe you need to get your feet wet. 😉 And like I say, lets put this aside, I think we both have had enough of this bickering. I won’t hold you to your word.

      • I keep seeing a little hill on the floodplain, sometimes it has snow downwind making it more visible. I have tried to find it on a map for orientation purposes, but haven’t been able to work out where or what it is, or if it has a name. Can anyone help?

  2. Depth by Day and Magnitude within 20 KM of BB
    M5 – trending deeper
    M4 – trending shallower
    M3 -trending deeper

    • Ian, I do not want to dismiss your hard work in generating these graphs, but I have some remarks:
      1. The trend lines have a very small difference from a straight line.
      2. The grouping of M5, M4, and M3 is completely arbitrary.
      3. The latest M5 at 0.9 Km goes against the trend, and personally I would not have used a straight line, why not a graph line?

      And finally, what does it mean? What conclusions can you take?

      • Hi , Events of the past month around the caldera, hour by hour. I have diminished the relative size of quakes to avoid overcrowding. First view is from the east, then from the top (with terrain elevation numbers), last views are rotations with all the events and some moving tilt in the last one. All events are over mag 3, event color is date related (see colorbar)
        data from IMO nad NOAA, made on Gnu Octave

      • What conclusions?

        Well pretty much exactly what you said lol

        There is nothing there, no patterns or trends no matter how hard anyone looks it is completely random so far expect for maybe the locations

        I am just posting data that I am playing around with, anyone can come to whatever conclusions they take from it

        And I don’t find it hard work :), I enjoy playing with numbers


        • Ian, good you didn’t take it too critical.
          We are all humans, and we have the natural tendency to see patterns, even if they aren’t there.
          After weeks of looking at eq and gps charts I also see patterns, but do not know what they mean as I’m *not expert* !
          I just saw your charts and thought: what does he want to say? That’s clear now.


          • I have been looking too long

            I am getting strange looks from my family when at dinner I am making Bardar cones out of mashed potatoes with gravy chambers

    • I wouldn’t say the M≥5s are trending deeper. I can’t read your fonts (too small for my old eyes) but from the fourth day back from the end, they are getting shallower. There’s a similar trend for the M≥4s as well and more of them are above the 6km mark than below it, especially in the last two days.

      • Sorry Mopshell

        It is easy to see before I make it into a picture

        M5 is red
        M4 is brown
        M3 is blue

        I just set the trend from the beginning of the first M5 and the line is automatically calculated

        You could be right about the last few days or week

        • Oh that’s okay. This is why I make my fonts ridiculously large (around 36-48pt) when doing the summary maps 🙂

          I think I’d need to see more than two days of an apparent upward trend to feel any confidence in it. Though, if you look the shape at the bottom of the graph, there is a dip on the third day and another on the fifth and sixth days after which there’s a distinct rise, except for about three outliers (two M≥3s and an M≥4). I’m also fascinated by that diamond shape that straddles days 6, 7 & 8 below the 6km mark. That has to be the heaviest concentration of ‘quakes in the entire graph and it’s intriguing that it should form such a distinctive and symmetrical shape.

          Looking at today’s quakes: of the eleven M≥3 so far, only four have been below the 7km mark (and one of those was 7.3km). Of those four, one was an M4.6 (8.2km) and the others were M3.2 (8.7km), M3.5 (7.3km) and M3.7 (9.9km). So there may be an upwards trend – or the very next half dozen ‘quakes could void that idea by being even deeper! 😀

          • Every time I think I see a pattern it falls apart when you look at it close.

            The best graphs to show any sort of pattern or cycle are Karen and Deep Thoughts energy graphs, you can really see the buildup and release. I would guess this is related to the structure failing after a certain volume has drained from below, so it holds and then holds and then hits the breaking point and faults rupture and center drops.

            The only other distinctive pattern appears to be location, it is quite clear. The 3D plots are the best to see this

            Also, the lack of patterns can also help you reach conclusions as well

            • Fair enough. I wasn’t reading anything into the diamond, just “oh look, there’s a diamond shape”. 🙂 But I can see where the concentration of ‘quakes are on the location charts. And I do think that looking at depth over time is an interesting idea.

    • Hi Ian

      You are plotting all earthquakes within 20km. The relations may show better if you plot it within 10km. I am ataching my plots (last time, I think.) On the left, all M3+ quakes within the Bardarbunga area (not the rifts). Right – only the ones north of the centre. The red/blue lines are my suspected sequences. I picked them up first from very brief series, within a couple f hours, and the noticed that this upward migration continued in some cases. But without the lines to ‘guide the eye’ they would be far less obvious, and they won’t show at all if you fit a line to the whole data set (because only a fraction of the quakes belong to sequences, and sequences don’t last.) I plotted the blue line before the latest M5 but as you can see, it fits well.

      The bottom plot is sneaky. I took the slope of the red line and subtracted that from the depths. Than I reversed the axes. The result is that each sequence now shows up as a vertical group which is easier on the eye. You can pick out some groupings but also see that many quakes do not group. But in general, if several points (circles) touch, they tend to do so vertical rather than horizontal.

      Keep going – theories need constant checking against data! Do make your labels a bit larger if that is possible.

      GL Edit: Added an errant “L,” It was absent with out leave. If it had permission to wander off from it’s duty station, let me know and I’ll take the substitute back off. 😀

  3. “We don’t need to know where you are
    You don’t want to know where we are
    Because you know if I would meet you
    I would get you down on your knees and eat you”

  4. You guys are killing my business…. Have a bistro – summer on its way 27c tomorrow and I still have not produced my summer menus. Staff are praying for an eruption so that we can get back to work. (I am not – think that we should be satisfied with the fiery and beautiful baby bard.)

        • Wide selection and am very indulgent with friends ….. Cape wines suit the sunshine and beach life.am looking for a New Year’s Eve cabaret…..

      • You’ve given me a great idea of what to do with some of my Scotch Bonnets. These are definitely NOT for beginners – this year’s babies are a volcanic 100,000 – 250,000 Scoville Heat Units, compared to a typical Jalapeño which is around 5,000 – 10,000 SHU.

        • Heh… I had some store bought dill pickles that I re-canned with a slice of habenero in each jar. My stepson and his coworkers ate every single jar that I made. They would sit around at lunch daring each other to eat the pickles. It got to be a testosterone driven competition as to who could eat the most.

        • Growing Trinidad Scorpion and Carolina Reaper here (Sydney, Australia), and that’s like biting into a piece of glowing lava. Making sauces, pickled chilli and true firewater with them.

  5. Smoke rises near the peak of Mount Ontake after it erupted Sept. 27. The photo was taken by Izumi Noguchi, who failed to escape. izumi noguchi/kyodo
    From today’s article in Japan Times: “Mount Ontake’s ashes yield four more bodies as search teams race to beat typhoon”

    Yesterday it was noted that the widow of the victim (59 years old) allowed AP to publish this frightening photo.

    Daily Mail (of course) has more:

      • Tragic.

        One, surprisingly, did die from inhaling hot ash or gas. Surprising as this is the only reported death that I know of from anything to do with heat from this eruption. I guess he or she was closer to and / or above the erupting vents.

  6. Sorry was away doing other things. further to discussion about “new vent” north of Baugur, on screenshots today, and on previous post-page, here is a shot from 30 sept

    I had assumed that the feature was an artifice, the continued vigorous outgassing of erupted lava seen on a bend in the lava river and so foreshortened. Of course I’d be very happy for it to be a new vent!

  7. Something is very different now, on the webcam, inbetween the blasting sand and low clouds billows of steam from a new place, seems like the lava is doing a serious attemt on the river.

    • Oh I have to see this Carlpuđdl… a lovely close-up of cloud on Mila 1…. oh and on Mila 2 too… so over to Kverkfjöll and… hello cloud. :-<

  8. Can someone contact futureVolc, and see if any of the presentations are posted up on Utube ?

    Am locked out of my email acct right now…

  9. So, Mars geo is “heating” up

    Curiousity is into the base level strata of Mt.Sharp, and it appears to be sandstones, no way it could support a 3 mile high peak in the middle of a shattered crater.. look how the slabs break and rattle stones around while drilling

    and some decidely weird formations, this one is the ‘traffic light”



    and an interesting angle on formation, but i still like Thomas Golds theory that Mars was an ice planet, and all these mud volcanos formed scarps because the ice supported them


    and you thought we had it tough with plate movements, imagine finding the energy to do this stuff without them…

  10. Another large one though not showing up on the drumplots as yet:

    4.10.2014 _ 18:55:07 _ 64.665-17.438 _ 2.1 km _ 4.9 _ 99 _ 5.1 km ENE of Bárðarbunga

    • You’re not wrong there! I too was wondering why not on drumplots! I thought I’d worked out which data sets showed EQs and in what order, but nooooo, far too simple….

      • I was really surprised to find it on the IMO table before the drumplots – they’re playing with our minds, I tell ya! o_O

            • Yes, My Precioussssss, and Dante would be proud too! Looking at Baugurs outflow on mila 2, the first stretch of the flow seems very agitated, (on the first bright stretch), not sure if the jam’s actually sloshing or it’s a pixellation effect?

            • The sloshing seems to be out of time with the jumping camera, so I think we have explosive degassing within the lava flow. And the lava seems to be stretching further east; soon it will b passing out of view.
              Looking at mila 2, last night it looked as if Baugur had a hole in its front wall. I assumed that it was just part of the lava stream flowing down from the vent, having turned a corner. This morming it was smoking like a new vent. Now it looks bigger and brighter.

              With so much going on, we NEED more cameras to cover the wider scenes of action. And some overflights to see where that lava has got to.

          • I see it, I see it! Ooooooh! Red stuff! But this is spooky… **adjusts tinfoil millinery**… see those two black eyes staring down at the eruption… 😮

            • Probably nothing worse than a combination of an overdue appointment at the opthalmologists and an active imagination.

            • Sleep deprivation! Either that or my heart medication some side effects my doctor neglected to mention… 😀

            • Oh and everything Pyrite says… I really am overdue for an eye test and all my school reports waffled on about ‘daydreaming’ as if it wasn’t a good thing! 😎

            • Have you noticed thet the edge of Baugur now is very visible on cam 2? How high are the walls now?

            • Let’s see…. I have a ruler here somewhere…. ah yes, top drawer… right…. measuring on screen… about 5mm. 😀

            • Mopshell, that´s not what I meant… lol! I actually think it is about 8 mms on my screen…

            • Carl, let me drag you up from the murky depths of your imagination and help you out here – “screen” or possibly “monitor” is the word you’re looking for. 🙂 Mine is rather oldish and smallish while icelandamateur has one of those you-beaut big ones! And we were being very scientific and measuring the height of the central crater… with a plastic ruler in my case… on screen… which is very much safer than doing it in situ… my ruler would melt for a start! 😮

            • Now you’re using a very sophisticated measurement device there, tottyrose! I’m very impressed… which flavour?

            • Mopshell, I am pretty happy with my murky imagination. It thankfully saves me from measuring my “screen” that often 😉

            • Carl, you can imagine all you want, it´s a good way too spend time whatever the teacher might have to say about it. 🙂 But I didn´t actually measure with a ruler, I did a guestimate (med ögonmåttet). And by the way, I a girl….

            • I was wondering what Carl thought we girls were measuring but didn’t like to ask… o_O

              And Carl, by all means imagine all you like to your heart’s content, if it keeps you out of trouble. 🙂

            • I just knew it had to be a black one – that’s style, that is, and with a Dr Who reference as well – sweet! 😀

            • Oh, I was fairly convinced that all of you are girls… and it is rare that Ladies measure their screens to see who has the most inches… Aherm!

              Ögonmått är alltid bra, själv mäter jag med skumbananer 😉

            • told you, carl does not go by rules
              even mumble in some foreign language
              take no notice of him

            • He’s waffling about foam bananas… I don’t think he has Ebola… maybe it’s Malarial hallucinations… or possibly he’s blotto (translation for non Australians: a temporary condition associated with alcohol 🙂 )

            • yes, very bad mix alzheim light with beear,
              flu or other medicin needed substances
              might meke him sound lik he be drunk 😉

            • If so, then he’s a funny drunk. 🙂 He’s excused. He’s not feeling well and I’m sure any alcohol was only meant for medicinal purposes. He’ll sleep well! 🙂

              You’re a really good friend, islander. 🙂

            • Lol woke up to Carls remark …yes us ladies do measure our screens lol…being an artist i have several types of ruler and a jar of jelly beans on the desk :D…some 100 pens, a printer and no nails, glue, glitter and a couple of oh sh1t buttons…(don’t ask)…..

            • Sounds to me like you have all the essentials – I really must get some no nails **adds it to shopping list**. I have an on-the-other-hand button – not quite as interesting as an oh sh!t button (not asking, just employing my active imagination) but quite useful. 🙂

  11. And so, to bed, as someone famous said. Sleep well Europeans, Wakey wakey Californians, enjoy the summer, Ozzies. ZZZZZZZZZZZZZZZZZzzzzzzzzzzzzzzzzzzzzzz.

  12. And in honour of the boiling lava flow, tonight’s dessert will be ‘bombe surprise’ – home-made chocolate ice-cream encased in home-made mango ice-cream.

      • Take two sorts of contrasting ice creams and several small receptacles (plastic ones may be better than pottery for turning out, as I found out the hard way!). Use one ice to line the base and sides of the containers. Return to freezer and chill. Then fill the hole with the second flavour, again freeze. Then cover the ‘surprise’ with the remaining first ice cream, freeze again. When ready to serve, turn out by plunging the container into hot water for a few seconds to loosen it. Enjoy.

        • the mango ice cream is one tin of mango puree, 7 fl oz of cream, juice of one lime, and sugar syrup made out of 4oz of caster sugar dissolved in 2 tablespoons of water. Mix and freeze. I have an ice cream maker which does the biz in 50 minutes.
          The chocolate one is more tricky, as I have 100% coca pate from a choclaterie in France, and I have to adapt recipes for it. the recipe I adapted uses dark 50% chocolate, muscovado sugar, cream, and custard.
          Other recipes are available.

      • So, how do you make this? 🙂 🙂

        ETA: Ah, never mind, you posted the instructions while I was typing my comment. 🙂

        • It was goooooooood. A nice pud to have after duck with red wine cherry sauce, bubble and squeak, and spinach. (All veg home-grown)

  13. Ahhh, I’m happy to see the bar is open. Anyone for a Gin Rickey? I made my first (successful) cheesecake today – Lime Cheesecake to be precise. Please help yourself to a slice. Now, I’ve had this song in my head for about a month now and was not helped by Lurking’s story of Frizbee and Heart … enjoy:

  14. And now to bed as ive a hundred gaming related calls to answer tomorrow…which are mainly on the Fifa 15 at the moment and i am not really keen on football so its very tedious lol…..would rather discuss volcanic activity while upside down playing a flute drinking schnapps….nitenite volcanoholics 🙂

    • this is several days/weeks old; I remember being frustrated that they did not film right down the end of the flow.

      • right, but it shows well the canion and the smoke from its edge
        not new craters, but will not be bad go look at them next summer

  15. Nearly bedtime for me too. Just winding down right now and I thought I would share this with you all. It’s an Icelandic folk song about the area we are all watching. It’s a wild and stark journey now, even with the comfort of modern transport. This song really brings home the remoteness of the area and how unpleasant the journey must have been on horseback. Imagine all those dust devils and the occasional earthquake. No wonder people worried about trolls, elves and dragons.
    Also I find the music interesting. It has a lot in common with Russian folk music.
    I hope you enjoy this very dramatic and poetic song. 🙂

      • good plot
        shows well how
        stabilized the event is
        my estimate be five more months
        and no ash eruption
        untill then

        Actually figured out how this is now driven. By gravity.
        Bárðabunga magma “chamers” have rock and ice on top of them.
        Quantity unknown, irrelevant untill it runs out.
        This weight simply sqeeses magma out,
        outlet is at “just” 850 m asl, top of Bunga is at 1900 m asl
        (so 1000 meter “fallhæð”)
        so unless it sinks (ie. Ice surface) down to 900 m asl,
        it will only stop when magma chamber(s) drain out,
        so far at rate 39 meters/month… dedcting Dike, but that might
        complicate things if “rift” goes on beyond magma supply
        from Bunga. But there might also be magma squeesing into
        Grimsvötn. It is inflating at rate 2 cm /month. They also lie lower than Bunga.
        Think stick tube into full 200 liter water barrel, kneel down and suck
        on tube until water runs free; it will emptie the barrel.
        Only here magma goes first up into dike, before coming all way up.

            • Also thought it was getting steadily bigger with live lava flows brightening up all the way when it flows from the vent after a ‘pulse’. Interesting to read what you think, Mr Islander.

        • Hi Islander. I hate to say it but I think you have it 180 degrees backwards …. The weight of the rock above does NOT squeeze magma out. Usually the fluid, in this case magma, holds the caldera up. As you withdraw magma and/or gases, a void is created and the structure becomes unstable. Too much instability and it fails, causes earthquakes and the floor falls down. So the magma is leaving the chamber through a new path and given that magma is buoyant the path must have some vertical component at all times. This is why I think the lowermost chamber is “leaking” towards the NE.

          And another implication is that all the energy released by the EQ is really meaningless as all it represent is gravity forces and structural colapse. No connections to an imminent eruption.

          Again my humble opinion but it fits most laws of rock mechanics and fluid behavior.


          • Using your arguments and thinking a void beneath the caldera plug, wouldn’t it have collapsed before now unless the “void” is being filled rapidly from somewhere else? From where? The mantle? The depths of the quakes do not uphold this as a possibility unless there is a free path for the magma to rise. In which case I would have expected , again, an eruption by now.
            The slow drop does indicate loss of material but to where? The fissure? If that is happening then the leak from the caldera is happening at mantle depth as I understood that the magma being ejected from the fissure originates directly from the mantle. Do these speculations from yourself and islander suggest that the ejecta from Holuhraun originates from beneath Bardarbunga or even further, from beneath Grimsvotn?
            This morning’s quakes do suggest that the NE rim is being hammered again, by what though? Magma from one of the chambers?
            I do think that the Grimsvotn system is affecting the activity in the whole area. I suggest that each volcano system here is playing some part in the mechanics of the event. I think, with absolutely no proof, but just a suggestion, that the Icelandic plume is complicating matters here.
            For months prior to the eruption here we were watching activity from SILs in the area and we knew something was happening beneath. Each SIL was telling a story which we couldn’t interpret.
            I am far from being an expert, hence my many questions. I have no answers at all, just throwing a few spanners in the works 😀

            • Hi Diane and good questions/observations. Subsidence is caused by removal or shifting of magma at depth. The EQs seem to indicate that subsidence starts at 10km so thats probably the top of your magma chamber. Magma leaves from there and goes in the dyke and erupts at Holuhraun. It does appear that the chamber is not being replenished as fast as it leaks but it still must be huge to maintain such a steady flow rate at surface. Mantle probably starts at 25km and I have no idea how it reacts regionally and if all the volcanoes are somewhat connected.

              And you got some the rifting, the weird bend in the MAR and the hot spot to contend with … Lots of possibilities for answers.

            • Thanks for the paper Ian. I fully agree that there might have been some regional stress fields that forced magma out of the 10km deep main magma chamber via the formation of the dyke. What I was discussing was related to the events post dyke emplacement where the main chamber is somehow deflating into the dyke and removing pressure support for the rocks above it creating the normal faults (earthquakes) surrounding the caldera and the associated subsidence.

              I wonder if anyone looked at the tensor fields of the main EQ from the start and noticed if there was a change from strike slip (stress inducing) to normal faulting over time. Not a geophysicist so cant do it …

          • There is no void, at least not lower than, say, 4km in depth. Below this, water, CO2, and probably sulfur dioxide are all above their critical point, so they would be supercritical fluids, rather than gasses. The pressure at this depth is also high enough that brittle or ductile failure of rock would occur for any void of meaningful size.

            Therefore, avoid void theories of a void. 🙂

            • Thanks Matt. You are correct that there is no void. Gas expansion, fluid expansion or magma expansion due to depressurization would fill any available space. I was trying to visually simplify the science … What I believe you get is that if you lower the pressure of the chamber, the roof will subside as the magma pressure cannot support the full load. This has a trickle effect upwards and creates all the EQs between the chamber and surface.

              The point I was trying to make was chamber depletion drives the EQs and it is not the caldera collapse pushing the chamber to empty like a piston pushing from the top.


    • Hi KarenZ,
      what do you use to process the raw eq data?

      I started doing some energy release estimation of an different earthquake area in excell and I just want to know if I am on the right path or I should work this in a different way.

        • Or you could use a derived formula that comes from matching EMSC’s moment magnitude values to the quake they were calculated for.

          In Excel: =10^(9.385+1.434*(Quake Mag))

          The result is in Newton-meters. (Equiv to Joule according to Wikipedia)

          The formula was derived using DPlot.

          • Ok, thanks KarenZ and GeoLurking, I started some weeks ago with something derived with a conversion based on the wikipedia article, moved on then to some calculations and after that I got stucked between Mw, ML and MD.
            I will check out the EMSC derived formula!

            • Just remember that it is not “their” formula. It’s my formula derived from their data. In other words, it could be very wrong. It’s essentially a best guess as to what relationship it is that they use.

            • We have actually asked IMO and EMSC-CSEM for their formulation, but without getting an answer.
              This is a bit surprising, normally you give formulations out if someone asks for them, they are not secret after all.

  16. So far I didn’t have enough time to watch more carefully to the eruption videos. The one above is just breathtaking! What a lava river! I would never have imagined it was soooo long! And lively, I mean, lava keeps hot miles away from the fountain!

    • Amazing video. Hard to believe that a phreatic detonation could have caused such a tremendous damage. There was this Brazilian Nissei among the hikers who happened to shoot a video right in the moment when the eruption took place, Images on Brazilian TV were stunning! Hope I can find it and post it here.
      Meanwhile we can only imagine the horrors these poor people went through.

      • The culprit is dynamic overpressure. It only takes about 5 psi of dynamic overpressure to detonate a house. And, in a phreatic detonation, that pressure front can be quite destructive.

      • Yes indeed.

        All the same, and considering the location, its amazing anyone survived and that any buildings are still standing, let alone in pretty good condition. I guess most of the energy went upwards.

      • Agreed scotsjohn, a very sad event and I have very great respect for the ones with the dreadful task of finding and recovering these poor people who died. They are the heroes in this awful situation.

    • Very comprehensive vid. They worked so hard to recover the bodies. And it will mean so much to their loved ones to have them recovered. God Bless them, motsfo

  17. Tonight a toast to Lord Kelvin who once said, “A great reform in geological speculation seems now to have become necessary.” OK, and to wash down that thought, a great Maine-made beer

  18. thanks for a fine beer, got nothing like that around here.

    would make a run to Portland, but festival season is done.

    all our emissaries to Black Rock Desert are home safe, will wander the haunted streets of this town. and catch the house band doing

  19. Good Morning everyone 🙂 Something’s hammering on the NE side of the lid this morning 🙂 maybe those Bardy trolls are boiling potatoes ready for Sunday Lunch 😀

    05.10.2014 07:10:28 64.676 -17.478 8.9 km 3.9 99.0 4.6 km NNE of Bárðarbunga
    05.10.2014 06:06:42 64.678 -17.463 3.1 km 3.9 99.0 5.2 km NE of Bárðarbunga
    05.10.2014 05:19:21 64.669 -17.454 7.2 km 3.8 99.0 4.8 km NE of Bárðarbunga
    05.10.2014 04:53:21 64.685 -17.495 7.6 km 3.5 99.0 5.3 km NNE of Bárðarbunga
    05.10.2014 04:01:00 64.668 -17.457 7.5 km 3.6 99.0 4.6 km NE of Bárðarbunga
    05.10.2014 03:54:54 64.666 -17.450 8.3 km 4.8 99.0 4.7 km NE of Bárðarbunga
    05.10.2014 03:44:24 64.616 -17.503 5.0 km 3.6 99.0 2.9 km SSE of Bárðarbunga
    05.10.2014 02:40:51 64.684 -17.496 4.7 km 4.1 99.0 5.0 km NNE of Bárðarbunga
    05.10.2014 02:40:29 64.670 -17.477 8.2 km 3.6 99.0 4.1 km NE of Bárðarbunga
    05.10.2014 02:19:27 64.619 -17.520 0.8 km 3.4 99.0 2.4 km S of Bárðarbunga
    05.10.2014 01:45:44 64.673 -17.461 7.4 km 3.7 99.0 4.8 km NE of Bárðarbunga
    05.10.2014 00:54:48 64.666 -17.418 1.6 km 3.2 99.0 6.0 km ENE of Bárðarbunga
    All Verified. With thanks to Iceland Met Office (IMO) for the data

    • I had a nice long sleep and woke to find… 13 earthquakes of M≥3 at Bárðarbunga! They have since added another 3 to the list. The total of earthquakes over 48 hours has gone up too since yesterday morning, and the vast majority of them are at Bárðarbunga.

  20. According to IMO, “no obvious changes are seen in the volcanic activity at the eruption site in Holuhraun.” – didn’t we see the opening of another vent? Perhaps they find it rather insignificant because the total output of lava and SO2 remain at the same level?

    Speaking of SO2, air pollution is expected in the southwest tomorrow. Poor people in Iceland – clearly a negative side effect of the otherwise picturesque eruption.

  21. Now that the ladies have started to measure their “screens” I thought we should set down some ground rules for how to measure your precious “inches”.
    1. You should measure from the first “pixel” in the upper lefthand corner to the last “pixel” in the lower lefthand corner.
    2. Do not measure the plastic or metalic frame to get more “inches”.
    3. Do not measure the box the “screan” comes in.
    4. If you give your size in a more obscure way as counted in candies you need to provide the size of the candy in millimeters together with a conversion chart or you will be disqualified by the umpires.
    5. Remember that everyone lies about their “screan” size. After all, it is not that likely that someone else in here will come and try your “screan” out.
    The Umpires are GeoLoco, Pyrite and Carl

    Now the competition for size queen can commence.

    *straight face*

      • Addendum to the addendum, if you are using a cm-graded tape you need to convert to a candy, construct a conversion table and give the size as candies.

        • I’ll put lollies (translation for non Australians: lollies = candy) on the shopping list for tomorrow. I’m thinking smarties… or maybe chocolate freckles… or, if I can’t decide, both. 🙂

            • Smarties are like M&Ms (without peanuts) and it’s always been my belief that they would make me smarter if only I ate enough of them. I haven’t, as yet, reached that shiny goal but I’m persistent. 😉

  22. From the above conversation, I deduce there’s nothing much going on on the webcams or drumplots?
    I plug my laptop into my 40 inch tv screen, does that count?

    • I’d say it counts but final decisions are up to Carl and Pyrite. You do have to convert it to candy measurement though…. So far jelly beans and smarties have been the candy of choice but you might want to choose something larger for your screen… candy canes perhaps? or blocks of chocolate?

  23. An intriguing ‘Specialist Remark’ posted a few moments ago on the IMO site….

    “Today (5 October) at 09:34 an earthquake of magnitude 3.4 occurred in Öxarfjörður (North Iceland). An earthquake sequence has started in that region on 2 October and up to now about 100 small events have been detected. Öxarfjörður is on the southeastern end of the so called Grímsey Oblique Rift. Earthquake sequences are common in that area, however stronger events can not be ruled out.”

    • More or less a statement that all is normal there. In any given year the Tjörnes Fracture Zone has between 50 and 100 earthquake swarms. The area is also known for causing earthquakes up to M7.2

  24. There was a note a while back, in which the difficulty of assigning type of volcano to Bardar, it was suggested it is a question of semantics.
    I would like to comment, that in general in geology as in many other fields, the terms tend to be quite determined. One would not call a case of chicken pox a case of small pox, or hives a chicken pox? Anyway, they all produce kind of rash and can be unpleasant…
    Some terms are very precise, and others not so, such as porphyry rock or country rock. But still, there is a reason for each term. It is not a question of semantics.
    Now in the case of Bardar, I suppose there is some information lacking to make a good call what kind of volcano it is really. In a chapter out of a future booklet about Icelandic volcanoes (which can be downloaded from IMO’s pages), Gudrún Larsen and Magnús T. Gudmundsson (Institute of Earth Sciences, University of Iceland) have declared that Bardar is a “subglacial volcano with caldera”, dominant type of activity is “basaltic explosive, phreatomagmatic” and lava of type is “basalt dominant”.
    Apparently they had to come up with a designation for subglacial volcanoes in Iceland 🙂
    But of course, other experts or not-experts may come into their own conclusion about what it is…

    • I was looking at some mountains in my childhood island of Tasmania. As far as I’ve been able to find out, they were formed by folding and then shaped by glacial erosion. There is a short series of 7 photos in the slide projection at the top of this page:


      This got me to wondering about the erosion of Iceland’s subglacial volcanoes. How much do the glaciers move in a year and in what direction, and what kind of pressure does that movement exert on the caldera rim of Bárðarbunga for example? I’m guessing the timescale would have to be in thousands or even tens of thousands of years to make any real impact though.

      • Hi Mopshell. Most glaciers around the world are regressing due to global warming. They mostly erode when advancing so nothing being eroded at this time except by the streams from melting ice. And a rule of thumb is that 3km of ice will push down the land mass by 1km. Check the isostatic rebound theory. A 600m thick glacier has a very small impact …

        • Java, your assertion that nothing is being eroded when glaciers retreat is not true. From memory: all glaciers are in an equilibtium; above a certain line, snow accumulates and below, it melts. This provides a mechanism for constant erosion of the bedrock, as the ice always moves due to gravity to maintain the equilibrium. Glaciers are categorised according to their temperature. The Icelandic glaciers are temperate, not frozen to their bedrock and thus capable of erosion whether they are undergoing a surge phase or a retreat.
          When a glacier retreats, it does so by losing ice from melting on the surface and at the snout. This can actually increase the erosional power of a glacier, as gravity then speeds the ice movement relative to the bedrock, causing more plucking of the bedrock and abrasion by the rock load carried in the lower levels of the glacier.

          • Source: http://www.antarcticglaciers.org/modern-glaciers/introduction-glacier-mass-balance
            Vatnajokull is the largest of 5 ice caps in Iceland. These are the remnants of the large ice caps which covered Iceland during the last 3 million years. Studies have shown that the oldest ice in Vatnajokull is 1,000 years old, by dating of tephra layers (Ari Trausti Gudmundsson (2007) ‘Living Earth’ pp219-222.
            I’ll have a go at finding out whether there is erosion going on under this area, but it may well not have been studied.

      • So very beautiful Mopshell. I was fascinated about Tasmania too. You really grew up in a special place! And also I was looking at the local hills when I was growing up and wondered how they came about to be….
        And later the Appalachian mountains in the US, also folded and eroded, but small and smooth. (Maybe a bit like Smarties)…
        About glaciers, I get a kick thinking that the density of ice is much less than that of rock, so if water is one then rock is about 2.6 or even around three for mafic rocks (specific gravity – compare something to same volume of water), and ice slightly less than one… The weight of ice is less than same amount of rock would be. BUT ice has also other properties, such as it may melt in a lower temperature than rock of course… and would cool the magma quicker I suppose.

        • I was very lucky to grow up where I did but then, I hope all of us here feel the same way about our childhood homes. 🙂

          Isn’t it fascinating to start thinking about our home regions in terms of its geology and formation. Gives me a whole new appreciation of the awesome power and beauty of the place. 🙂

    • I guess that definition works as well as any other.
      I called it a complex volcano since it having tuya parts, a caldera, stratovolcanic components and shield components, also side vents and so on and so forth…
      I guess calling it an Icelandic sub-glacial volcano with caldera fills any need for a definition since it is wide enough to incorporate all Icelandic sub-glacial volcanoes and leaving out the non glacial ones.

      • So perhaps the glacial part has to do with morphology of the volcano, as I read somewhere, as if the erupting lava was under water, and this is why it becomes such a flat head?
        What do you think, is the flat head because of glacier or because of some horrible catastrophic explosion?
        Or just a gentle subsidence of the roof to the emptied out magma chamber?

        • Nature often seems to like having several solutions to the same problem. I am quite convinced that parts of the caldera has been caused explosively, parts through subsidence, and that the general flatness is due to it basically being a huge tuya formation.
          Most volcanoes alternate style of eruptions so believing in just one model is normaly just counterproductive.

        • Makes sense, also with the many – apparently – eruptions that are attributed to Bardar.
          By the way, the formations on the west flank of Bardar, what are they? Are they ash or lava? Seem quite dark in pictures.
          The other question is, how long does it take to form some 800m of ice, the proud top of Bardar? This question is or course specific to Bardar.

          • Have a look at my reply to Java Geodude a few posts up. There has been ice on Iceland for about 3 million years.

  25. Another large quake.
    05.10.2014 11:14:25 64.673 -17.455 6.5 km 4.7 99.0 5.0 km NE of Bárðarbunga
    Weird that the drumplots are now so far behind the action as it isn’t showing on them yet.

    • The drumplots aren’t updating for me either. They’re stuck at 10:53 and a bit for the moment. They were behind the IMO table yesterday too. Maybe it’s the chill factor…
      *not very technical but can connect up a PVR and my own desktop 🙂

    • IMO have now included another four M≥3 quakes prior to that M4.7:

      5.10.2014 _ 11:11:18 _ 8.2 km _ 3.3 _ 99 _ 3.4 km SSE of Bárðarbunga
      5.10.2014 _ 11:10:06 _ 8.9 km _ 3.0 _ 99 _ 3.6 km WNW of Bárðarbunga
      5.10.2014 _ 10:55:13 _ 1.9 km _ 3.0 _ 99 _ 7.7 km ENE of Bárðarbunga
      5.10.2014 _ 10:49:29 _ 4.6 km _ 3.8 _ 99 _ 7.4 km NE of Bárðarbunga

      With the M4.7, that’s five M≥3 ‘quakes in 25 minutes.

      • And then…. nothing, unless it was such a shock to the poor people working for IMO they had to go and lie down. Nah, they are far too professional for that… now it it had been that many 5+… 😉 😀
        Odd though the lack of quakes for a short period then only small ones after that. Must have used up all it’s energy and needs to build some more first.

        • IMO have just added another M3.6. So many small ‘quakes though.

          Frances, do you remember back in August waiting and waiting for a ‘star’ quake? How excited we were when there was an M3.0 but then deflated because there was no star because they had to be over M3.0 to get a star? Now we feel the same way about M5+ 😀

          • Yay! My memory isn’t that bad after all! :p I do remember that well and I know for sure that I am really going to miss fitting in regular daily visits to this site when things die down again. Still perhaps there will be another non-deadly eruption to watch. That is what I love about keeping up to date with Etna, fascinating and no slightly guilty feelings involved in my enjoyment.

            • I also recall your choosing an earthquake figure for eruption time – I think it was 1666? – and we didn’t realise until later that the figures we were looking at were just over 48 hours and not cumulative. It went way over 1666 in 48 hours before we got the Holuhraun eruption – and I thought your figure was going to be too high! 😀

  26. I don’t think we will see any more significant M5+ quakes in the caldera unless the plates move significantly again, we are just seeing friction quakes until an event happens. Does anyone have any current data on the rate of plate movement and directions?

      • It would seem to me that all but 3 stations reflect rifting of the region. But GFUM, HAFS, and ONO (is that right, hard to be sure of the letters on that one) — these are all moving more or less opposite to the regional rifting. Anyone have thoughts on what’s going on here? Are they moving towards Bardy becaus of its deflation?

        • What clued me into looking at this a different way was how the experts spoke of the GPS measurements. They talked about them in terms of using them to evaluate the volume of magma in the dike and didn’t mention rifting (that doesn’t mean they weren’t taking it into account; they just weren’t mentioning it). That’s when the GPS started to make sense for me.

          From what I recall, the first visual evidence of rifting was noted after the first Holuhraun eruption had ceased. At about the same time, earthquakes in the rift zone began to intensify, as though the rifting had caused a blockage in the conduit and the magma was having to bully its way through. A couple of days later, the second eruption began in Holuhraun and has been going strong for 36 days now. Meanwhile, the earthquakes in the rift zone have gradually eased up. I’ve noticed that it can go for more than four hours without a ‘quake in that area which may indicate that the magma is moving through there quite freely now. Also, I’ve noticed in the last couple of days, that there is an occasional earthquake at the tip of that zone. Maybe it’s extending its way northeast again – or maybe not. 🙂

  27. Did anyone see Doctor Who last night? The episode, ‘Kill the Moon’ was partly filmed on Lanzarote, with its black lava fields doubling up as the moon. Loved it!

    • Never miss it – I’ve been an addict since the days of William Hartnell. Peter Capaldi as a cantankerous, grumpy Doctor is growing on me.

      • Patrick Troughton was ‘my’ doctor. I have happy memories of hiding behind the sofa and being scared witless by the cybermats (I was fine with the Cybermen, for some reason) and the Daemons (church gargoyles coming to life, ugh – I still get the willies at them) and the shop mannequins whose hands dropped to reveal guns, among others. Watched it religiously until about half way through Tom Baker’s stint, then stopped. Am just getting back into it, all these years on, but I don’t feel inclined to catch up on what I’ve missed!

        A brief search shows they were filming this May at El Cuervo volcano in Timanfaya National Park. Lucky buggers.



  28. Hello folks,

    Could this be showing the reactivation of the secondary vents to the south of the main vent?

  29. Quakes this week M3+ up to 20:00 last night from final lists by Icelandic Met Office. Please note that often these lists are different even from quakes listed as 99.00 on the 48 hour chart

    Also, the black dot is where the IMO uses to measure distance from Bard

    I used Smarties 🙂

    • Aha, smarties and jelly beans – the new international measurements of choice among discerning faux scientists 🙂 Incidentally, did you eat all the green and blue ones? The blue and red are my favorites. 🙂

      I’m thrilled to see that black dot – I’ve been wondering for so long about where IMO’s reference point for measurement was located. So if we draw the four arms of the compass through that point, it makes sense as to why the vast majority of ‘quakes are designated as being in the north-east quadrant with the secondary cluster being in the south-east. It also explains why so few fall into the western half – there isn’t much of it!

    • Would by any chance the Black Spot be where the GPS is? Though I really thought it would be .. somewhere else….

      • I recall reading the GPS was 1 km SW of the center of the deepest point, I marked it on with a green dot and included depths of this weeks quakes

        Hope this is readable??


    • I think I’ve just realised why IMO sited the reference point where they did – it’s on the border of two flood plains. It would help them to estimate where a jökulhlaup would flow to if there were to be an eruption. If it occurs in the arc north to south-east of that point, then it would flow through to Jökulsá á Fjöllum; if it’s on the other side, it would flow to the west. That would have to be a very important determination for the authorities as they organise their flood preparedness plans.

  30. OK! I have showered (Smiles sweetly at GeoLoco) and done my chores, washing hung out before we in the NW of England gets hammered by some nasty weather due tomorrow and my little brain has been threatening a belated and short rumination.
    I make no apology that this rumination may be a very senior moment and/or blonde…..

    If there is a micro plate under Iceland that “rotates” causing the MAR to form an “elbow” or “Dog leg” and there is a mantle plume causing volcanic activity under the Vatnajokull ice cap,
    Does the plume pass through the micro plate or does it just affect the temperature of the ancient rock causing it to melt? Does the micro Plate affect the upward direction of the plume as it side tracks round the micro plate ? Is this all happening under Bardabunga?
    I have read papers about “The Plume” . I have read papers about the micro plate, but I cannot find any references to how both these possible features interact with each other. It seems to be one or the other that affects the activity of MAR rifting.
    Does the activity of the micro plate and plume affect what is happening under BB?

    • In an article written by R. Stefansson in a local paper yesterday he drew the outline of the plume at around 2-300 km depth roughly as a triangle with the three corners at close to Myvatn in the north, Langjokull in the west and Oraefajokull in the south. Bardarbunga is near the center of that area. I found that interesting.

  31. Can someone please prove to me that Barda is supplying the magma to this eruption? It made sense to me when it started, but now after 6(?) weeks of consistency of eruption at new volcano, I’m doubting it.

    • I can’t imagine how one could “prove” any such thing, whether true or not. You’d almost have to inject a tracer substance into Bardy’s magma chambers and see if they come out the new volcano.

      But Bardy has been steadily subsiding, and something in the ballpark of 0.5 cubic km of magma has been leaving (if I recall experts’ estimates correctly), while something like 0.5 cubic km of magma has been erupting (IIRC). Both have been remarkably steady.

      Furthermore, I believe sudden drops in Bardy’s caldera have coincided with increases in intensity in eruption (subjectively, as best I’ve been able to compare visually).

      It seems pretty straightforward to me, and makes sense in terms of magma leaving an area pressurized by the great altitude of rock of Bardy and exiting at a lower altitude spot.

      • If I understand the experts correctly, it also fits in with the GPS movements: deflation around Bárðarbunga (GFUM, HAFS and VONC) and inflation on either side of the intrusion dyke (GSIG, URHC, HRIC and THOC).

      • Oh. I have been imagining just the opposite, that the deformation/subsidence of Barda is due to stress from the dike emplacement and deep-sourced magma eruption at Holuhraun. I got up the nerve to venture this postulation a few days (or more) ago in a different thread, after struggling for days to believe in the direct-injection from Barda magma chamber theory that seems to be the most popular here. NOT an expert of scientist, I just can’t get my head around the eruption being caused by Barda and not the other way around. and I guess I didn’t know there had been a direct correlation between magma “leaving” barda and magma erupting at Holuhraun. .

    • That is not an argument about the location of the source, just the depth. If the magma comes from the Bardabunga chambers, it can still be a shallow or a deep chamber – either way would give deflation. Magma rises, so it is not impossible that the stuff making its way into the rift comes in part from a deeper layer underneath Bardabunga. Steven’s argument above is convincing, linking the volume of the deflation to the amount of the eruption. The fact that the exit is lower than the rocky surface of Bardabunga can explain how easily it is flowing to the exit. That was mentioned in the comments above

      • The magma coming from BB, erupting 45km away after working its way under huge pressures through an existing dike structure, says one thing to me

        There is no easy path to the surface in the caldera

    • Haraldur Sigurðsson said in his blog that the magma chamber was deeper than he thought – could that be it?

      An excerpt from his blog http://vulkan.blog.is/blog/vulkan/entry/1448119/

      “The chemical composition of the magma also helps to determine the depth of magma… it is pretty much clear that this dynamic can not be reached directly from the mantle, but has evolved into a magma chamber within the crust, probably at a pressure corresponding to a depth of 10 km. Which said quakes and chemistry is consistent. This is now a little deeper than I would have thought, but then we are always learning something new.”

      • Yes, worrying stuff from an expert of his calibre, particularly –

        “öskjusigAllt suggests that there is a very large magma chamber under Bárðarbunga. This magma chamber, for example, delivered a one of the largest basalt lava on earth modern, Thjórsá lava. It ran for about 8600 years, all the way south to the sea, there is now a Stokkseyri and Eyrarbakka. The lava is about 25 cubic kilometers. Probably magma chambers with up to 100 cubic kilometers in the tank of about 1175 oC hot magma.”


        “Exciting times ahead? But the thought of the massive amounts of magma, which is under development is certainly awesome.”

        I have long suspected the magma chamber to be full, and any intermediate or lower chambers, but those figures are scary!

        • Yes, they really are, aren’t they. I remember when the tremor plots shot upwards on August 16 and reading that it was likely caused by a huge pulse of magma from the mantle. Those tremor plots never came down again. They’ve stayed at the 3000 – 5000+ mark ever since.

  32. Also at Haraldur Sigurðsson’s blog (link in comment above), there was also this diagram:

    and this accompanying explanation:

    “Earthquakes spread in a circle, defining the contours of the carton on a map. Bottom picture [the diagram above] shows Bárðarbunga on a map and the map shows distribution of earthquakes [at] Bárðarbunga in August. Seismic Data are of course from the website IMO.”

    He then linked to this short video which not only shows the distribution of earthquakes on a map but also charts their depth and magnitude from 16 August to 19 September: https://www.youtube.com/watch?v=3PTEDxrIRoM I suggest opening the link in a new tab and going to full screen as the charts are fairly small.

  33. Isn’t the current theory that the fissure’s magma is not being fed directly from the magma chamber directly below the caldera floor: rather that both the shallow magma chamber directly under BB caldera AND the fissures are both being fed from a larger reservoir at depth?…e.g. a common magma source for both the fissure and under the caldera?

    Lastly, this whole mess is starting to weigh on my psyche. This morning, I spent at least 15 minutes squeezing a brand-new tube of toothpaste, trying to visualize the whole BB magma system.. then proceeded to forget to brush my teeth.
    The Wife is now rationing my VC access until AFTER morning hygiene is finished.
    She does like her morning smooch.
    But not when I smell like an old truck tire.

  34. Hmmm . . . per IMO, there have been 36 quakes of M3+ in the past 48 hours. Since 16 Ausust, that number has been as low as 7 and as high as 25 or 26. Most often, I would see it in the upper teens. I had surgery Weds., so have been in la-la land for a few days, and haven’t looked at that figure since maybe Tuesday. Does anyone know if this is a sudden increase, or if the 48-hour rolling total has been steadily going up? The total number of quakes is down, so what we seem to be getting is less frequency, but higher intensity.

    OT: Regarding “screen” size. I use an iPad Air. Objects enlarge with the slightest touch. But who needs size, anyway, if one has imagination? 🙂

    • Unscientific answer is that I keep a running total of 3+s per 48 hours and on 22 sept it was 21 in the 48 hours, and on the 3 Oct it was 17 and at one point today the 48 hour figure was 33. I think there was quite a burst of 3+ and 4+ overnight-ish, but no 5+ recently. Go on Wise Ones, shoot me down for subjective inaccuracy…………

      • I don’t doubt your figures at all. I remember those giddy minutes when it was 33 M≥3s in the last 48 hours – it’s now 38! 😮

        In the 48 hours before SoCal went in for surgery, there were just fourteen M≥3s recorded on the 29-30 September. On 1 Oct it was 11; 2 Oct it was 9; 3 Oct it was 8; 4 Oct it was 14 and so far today it is 21!

    • I did notice yesterday morning that the quake count was 145 for the 48 hours with about 9 M≥3s. Some 12 hours later, it had rocketed up to 192 total but I can’t remember how many M≥3s there were by then. Now it’s 209 with 38 M≥3s so it’s increasing quickly! 😕

      Great to have you back, SoCal and I trust you are taking it easy. To bring you up-to-date on the most recent happenings: Carl announced that he is engaged – to his “nutty professor” I believe 🙂 He has also decided he has Ebola (a step up from a man cold apparently). He then waffled on about foam bananas, apropos of nothing, and retired for the night.

      Islandamateur asked how high the Irpsitadyngja crater was so I took out my ruler and measured it on the screen (5mm). Islandamateur said it was 8mm on her screen and tottyrose said it measured one black jelly bean on hers. Carl decided that there needed to be rules about measuring screens and that candy measurements were to be adopted. This introduced smarties into the new international measurement code. There were addenda added by Carl and Pyrite but whoever looks at the small print?

      Meanwhile, stars1die made a mouth-watering volcano dessert from homemade mango and chocolate icecream (recipe above) and I swear I put on kilos just looking at it. 🙂 Greyfool and I were wondering what’s going on with the drumplots and Frances can’t remember if she’s losing her memory or not. Diana posted links to a traditional Icelandic song which is worth listening to and reading about.

      On the Bárðarbunga stock exchange, M5s are down but M3s and M4s are up (five in twenty-five minutes earlier today). Welcome back! 😀

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