Bárdarbunga and stratovolcano formation

Bárdarbunga might be one of least visually impressive volcanoes on the planet, but she is there down below the glacier. Photo by Oddur Sigurdson.

Bárdarbunga might be one of least visually impressive volcanoes on the planet, but she is there down below the glacier. Photo by Oddur Sigurdson.

A couple of days ago we received an email containing questions from a bright young student named Jennifer D in West Chester in the United States of America. It seems like she has developed an interest in one of our absolute favorite volcanoes, namely Bárdarbunga in Iceland (among other things).

So, I will attempt to answer her questions in this post. After all, Volcanocafé is about learning and teaching about new things concerning volcanoes. And in this case, I do not think we have actually attempted to answer these 3 questions.

How do you know when a volcano is no longer active?

Volcanoes are normally grouped into 3 categories of activity. First we have the erupting volcanoes, then we have the active ones and those that are judged to be dormant. Sounds like there should not be a problem to divide volcanoes into these categories, but as usual things are never that simple. Let us start at the beginning.

Volcanologists working with volcanic hazard mitigation normally color code volcanoes into green, yellow, orange and red.

Erupting volcanoes

One of the more than one thousand eruptions that take place yearly at Sakurajima that takes place every year.

One of the more than one thousand eruptions that take place yearly at Sakurajima that takes place every year.

One could define an erupting volcano as a volcano that is actively ejecting lava and ash from lava (tephra). This is a commonly used form by volcanologists. This definition though quickly run into all sorts of problems as all definitions do when they are faced with the hard reality.

First of all, there are volcanoes that have very short eruptions. One of those is Sakurajima in Japan, it literally has more than 1 000 eruptions every year. The Japanese authorities have decided that Sakurajima is only counted as an erupting volcano during those short eruptions, and otherwise it is downgraded into an active volcano. On the other hand, volcano agencies in some countries have different interpretations of the definition all together.

Then we run into problem with a class of volcanoes that suffer from something called a phreatic detonation. That is not a real eruption since no fresh lava is erupted. Instead it is hot magma (lava underground) heating up water causing steam explosions. Some agencies say that those volcanoes are erupting, others do not.

Erupting volcanoes are color coded red. I hope that you at least get a feeling for the problems with definitions now Jennifer, and that we have not scared you away.

Active volcanoes

Mount Sinabung, really looking like an eruption, but it is just a phreatic detonation. The Guardian.

Mount Sinabung, really looking like an eruption, but it is just a phreatic detonation. The Guardian.

An active volcano is a volcano that is showing signs of activity that could lead up to a future eruption. Those signs might be earthquakes, rapid motion of GPS-coordinates (signs of magma entering the system), Geysers, hot springs, fumaroles (steam vents), volcanic tremor recorded on seismographs, and so on. But, in the end this is not enough. For a volcano to be considered active it should be showing signs that it could erupt in a near future.

A splendid example of an active Volcano is Mount Sinabung in Indonesia. It shows earthquakes, volcanic tremor and active fumaroles. It also suffers from phreatic detonations hurling pulverized rock between 500 and 7000 meters up into the air. This is about as active as a volcano can get before she is erupting. These volcanoes are color coded orange.

Dormant volcanoes

The dormant Yellowstone slowly doing very little while being beautiful. Image from Wikimedia Commons.

The dormant Yellowstone slowly doing very little while being beautiful. Image from Wikimedia Commons.

Let us now take a look at Yellowstone and Bárdarbunga. Yellowstone shows all of these signs of activity, and Bárdarbunga only a few of them. Still most scientists are certain that Bárdarbunga is far more likely to erupt. The answer to the question why Bárdarbunga is more likely to erupt compared to Yellowstone is though very long, and if you are interested I have written an article about Yellowstone that I link to at the end. Anyhow, both of these volcanoes are considered dormant. The important part is that they are currently not showing signs of erupting in the near future, even though Bárdarbunga is currently closing towards a possible upgrade into being active.

From there it is a sliding scale of dormant volcanoes until you arrive at volcanoes like Lassen Volcanic Center in Northern California. It had a very small eruption in 1915, but what makes it interesting is not that. The researcher Erik Klemetti has shown that there was no signs of an eruption for 100 000 years. So, a volcano can be dormant for a very long time between eruptions, and that is highly interesting.

These volcanoes are either color coded green if they are at their normal state, if they show signs of unrest they can for a time be coded as yellow as a warning that this volcano is showing signs of unrest. Now we are ready for your answering your question number two.

I read that the Bárdarbunga volcano in Iceland is considered restless, what does this mean?

Well, it simply means that it is showing some signs that it might be moving towards a future eruption. In the case of Bárdarbunga we are talking about earthquakes that are deep enough to be of magmatic origin, we also see GPS motion indicating that magma could be moving into the system, and on occasion we see magmatic tremor. For these reasons it has been called “restless”. The reason why Bárdarbunga is not classified as Active is that we do not really know how she behaves before an eruption. This is because the last eruption started in December 1902 and ended in June 1903. Some sources list a lot of later eruptions, but those where both uncertain and located in a different volcano named Loki-Fögrufjöll. I do not have a good answer how those possible eruptions have been attributed to Bárdarbunga.

So, the phrase “restless” is used quite simply to point out that Bárdarbunga might be headed for an eruption in the near future, but that we are far from sure.

How are stratovolcanoes formed?

This is really a giant of a question that is fairly hard to answer since the answer is different from each volcano, and also varies in between the different types of processes that form volcanoes. So, instead I am going to use my favorite volcano as One example of how a stratovolcano can form and leave the rest for you to answer Jennifer since this is the type of question that you can spend your entire future career as a volcanologist on.


The upturned boat hull shape of Hekla. Image from Wikimedia Commons.

The upturned boat hull shape of Hekla. Image from Wikimedia Commons.

Hekla is a very young volcano, it might be as young as 8 000 years old. And that is a really short time for a volcano to evolve as far as Hekla has done. She is in many ways a unique volcano unlike other volcanoes in Iceland, and for that matter in the world.

Hekla started as fault in the crust of Iceland, a weakness that opens up as tectonic forces continues to pull apart the Mid Atlantic Rift that divides not only Iceland, but also continuously pull apart the North American plate and the Eurasian plates.

As the fault opened up an unusual type of acidic magma poured out of the ground instead of the usual Icelandic hotspot basalt. Normally Icelandic volcanoes first form basalt floods and then a shield volcano with gently sloping sides. The gentle slopes form due to the basalt being very fluid, not unlike the maple syrup on top of your pancakes. Instead Hekla’s lava (dachite/andesite) was much stickier so it skipped the stage of forming a shield volcano.

Right at the end of the eruption in 2000. One can clearly see that the eruption has taken place along a rift and not through just a central vent. Photograph from Institute of Earth Sciences, University of Iceland.

Right at the end of the eruption in 2000. One can clearly see that the eruption has taken place along a rift and not through just a central vent. Photograph from Institute of Earth Sciences, University of Iceland.

At first Hekla formed a serious of steep sided cones along the 7 kilometer long principal fissure. As the eruptions followed those cones merged until a single mountain had formed. Hekla is shaped more or less like a ship’s hull that is flipped over and not like a classical cone shaped stratovolcano. This is due to Hekla being so young, as time goes by it will most likely form a more classic shape.

Another sign that Hekla is very young is that she is still erupting along the entire 7 km fissure when a large eruption occurs. She has though by now formed a central crater at the top, and as time and more eruptions occur more and more of the action will take place there. And when that happens most of the lava will pour out over the sides in such a manner that the classical type of cone starts to form.

Another thing with Hekla is that she is unusually violent for such a young volcano. Normally volcanoes evolve and acquire larger magmatic systems as they grow older, but Hekla seems to have had massive eruptions the entire time.

What can be said about stratovolcanoes is that they normally evolve from either a crack in the ground or a gently sloping shield volcano. And some evolve directly into a stratovolcano if they are forming where a previous larger volcano has been. Like for example Monte Vesuvius in Italy that was born from the remnants when the Monte Somme volcano was destroyed in a large eruption.

Welcome Jennifer to the large and bewildering world of volcano formation, as you have perhaps noticed by now almost every stratovolcano on the planet have followed a unique path as it formed. I just used Hekla as one example of how it can happen.




155 thoughts on “Bárdarbunga and stratovolcano formation

  1. Excellent post! I absolutely love reading about Hekla. I think she’s becoming one of my favorite volcanoes.

    • Yep, Hekla is quite one fascinating volcano, and like many others, quite deceptive. Didn’t everybody believe that the interval between eruptions was 10 years and the next one thus “overdue”? Well, the 10-yr intervals worked fine after 1970, but before that, Hekla erupted once or twice per century. A must-read: Sigurdur Thorarinsson’s “Hekla, a notorious volcano”, which can be found on internet bookshops like Abebooks at relatively reasonable prices:


      An article on Hekla’s 1980-1981 eruption:


      The book on Hekla’s historical eruptions (also by Thorarinsson) is currently available at Amazon.de


      and some more at Amazon.com


      I guess some of you would like to have one of the other of these as a Christmas gift 😀

      • Human memory is short. With Hekla, perhaps more than any other fairly active volcano, the recent past is NOT necessarily any good guide to the future.

        It’s become a bit TOO much received wisdom in more amateur volcanology circles that Hekla is “aseismic, a few M2.0, 60 minutes, then BOOM”. Dangerous. We have no idea what she’s going to do next.

        • In my very amateurish expertise I tend to concur with Mike. It has become a sort of “dogma” around here that Hekla is “aseismic” in a larger time span than 24 hours, or even less than that.
          However, given the more ductile nature of this region’s crust it is quite possible to admit it being so.
          On the other hand, how come it produce such evolved magmas with no previous seismic signals? For how long this “tradition” has created its roots?…
          Maybe this is what attracts us so much to this particular volcano – the desire to break with this tradition. We, Volcanocafeers, would enjoy very much to be the first guys and girls to forecast an eruption from Hekla within a fairly larger time span! 😉
          ,,,well just my two cents of rumination…

          • The latest eruptions (since 1970) have been essentially basaltic andesitic (that is, a very mafic andesite), so these magmas have been the least evolved that Hekla has emitted in the past few hundred years. Maybe that’s the trick?
            Anyway, also before the 1947 eruption, which occurred after 101 years of repose, and which initially emitted a much more evolved magma, there seems to have been little premonitory seismicity (though there was no seismic monitoring to speak of at the time).

        • Personally, I have never considered Hekla to be aseismic. Short tempered, yes, but not aseismic. My fascination with the short temper is just how fast the 2000 event went from simple indigestion to full on spew. But that is pretty much a one-off in my opinion. An example of just how quickly it can get into party mode. In order for that short temper tendency to be of any statistical merit, we need a lot more than one example/sample. Even at that the usefulness of the info is of dubious value. Statistically speaking, many of those systems are “overdue.” But like all proper volcanoes, they do what they want to do when they damn well please, no matter what the stats have to say about it, or how much prophesying or ill will is involved.

          • Problem is that at every recorded event there was either no warning, or very short warning. So the 2000 short run up was most likely the norm and not the exception.
            Thorarinson is very specific on that point when he goes through all known eruptions up to and including 1947.

          • Noted. Thank You. But even with more data, the Black Swan idea hints that even with that, the series of short run ups could be part of the “one in a million” group of events.

            And you know volcanoes better than I, one thing they seem to enjoy doing, is crapping all over the best statistical theories. Much like a pigeon on a statue.

            • I totally agree with that.
              It could be a Black Swan, or it could be that Hekla has some sort of Gear-box that she runs through as she matures. 1 per 1000ish for the first 7 000 years, then 1 per 100ish, on to one per 15ish…
              Not impossible really. One should remember that little addendum when looking at statistics of volcanoes. Ish. It always bites one in the butt.

      • To be a bit nitpickity Hekla has erupted with any range from 1 to 102 years in between eruptions since the large settlement eruptions. Before that she seems to have gone once every 1 000 years or so.

        I must admit that I am one of those who think that Hekla is “due” for another eruption. But that is not based on statistics, it has more to do with her unusual high level of activity. But, then on the other hand any activity at Hekla before an eruption is unusualy much 🙂

        As Boris pointed out, this is a marvelous series of books. “The Eruption of Hekla 1947-1948. Vol. I: The Eruptions of Hekla in Historical Times.” They made a series out of it, but number 1 is the essential one if you do not want to go into obscure details of ash chemistry (fairly outdated in parts).

        • Ruminating on my comment, and your follow on, I think the clue is that Hekla is not a volcano after all.

          It is a pigeon.

          It knocks over the chess pieces of a statistical model, craps all over the table, and then struts around like it has accomplished something, daring you to try and pen it up with a theory.

  2. Nice intro Carl. Of course, it goes downhill from here. The things get more and more complex the more you look at them. My favorite bruiser is of course, Grimsvotn, but it’s big brother Bardabunga is sitting over there on tip of the cook pot, biding it’s time.

    One thing that Jennifer probably didn’t ask, but that will bring up, is that Grimsvotn, Bardabunga, and Askja are all pretty large systems… yet they are all pretty close together. (Not to mention the other huge volcano on the other side of the icecap). There must be a rather large amount of magma feeding into the system. (loaded [and leading] question, I know) Do you think that the Icelandic hotspot may have anything to do with it? How about the fact that Bardabunga is sitting on top of a defacto triple junction, much like Hengill?

    • You really had to go there had you 🙂

      Yes, it just gets more complicated and more fun the further one goes.

      Yes, I think that the hotspot/mantle plume upwelling of hot material from deep inside the planet down under Iceland is affecting the amount of volcanoes in that part of Iceland since it gives a nice and steady flow of new magma.
      Also, I think that triple junctions do increase the chance for a volcano to grow bigger like Bárdarbunga. After all, it is not a coincidence that all of the 3 known triple junction volcanoes on Iceland are very big. The other two are Hengill and Theistareykjarbunga.

      • Yah… I did. You can’t leave out the Hreppar and Tröllaskagi microplates, they might get fidgity since they were left out. 😀 The boundaries for those two allow the triple junction aspect to come into play, and triple junctions (as you know), are some of the most seismically active tectonic regions due to their instabiliy. I think this weakness is what makes them prone to having volcanoes form on top of them, such as the Azores, Bardabunga etc. It doesnt’ always happen, like at the Mendocino triple junction but there isn’t really a source of readily availble magma until the subduction plate gets down to around 110 to 120 km depth and begins to delaminate.

        Since I broached it, what sort of source does Hekla have for it’s fairly evolved magma? Everybody else along that line seems to prefer basalt.

        • Science does not yet have a good definite answer why Hekla erupts erupt Dacite or Andesite instead of the usual Icelandic basalt. Dacite or Andesite is usually associated with subduction volcanoes and not hotspot volcanism.
          3 solutions have been mentioned, one is that there is actually subduction going on, but in a very local scale as a microplate is dragged down close to Hekla. Another theory is that there might be a piece of sunken crust that lies under Hekla, and the third is that Hekla has a very intricate way of quickly evolve basalt into more evolved magma. The last of those theories have problems though since Hekla is to young to have had the time for such an evolved magma as Dacite to form.

          • It’s rather a question of magma differentiation during a repose period; the longer the repose period, the greater the amount of differentiation (as outlined by Thorarinsson already in the 1950s and 1960s). The latest eruptions (1970, 1980-81, 1991, 2000) have been more mafic, with emission of basaltic andesite, which fits with Thorarinsson’s theory. A few decades to centuries can be perfectly enough to have a mafic magma differentiate into andesite or a similarly evolved magma. Vesuvius is a basaltic volcano when it is in an open-conduit, steady state condition (like from 1631 until 1944), but once it falls silent, as before the AD 79 eruption or also since 1944, the magma in its reservoir starts to differentiate, and just a few centuries are enough to make it become phonolite (that’s like a dacite rich in potassium and sodium) and tremendously explosive.
            We shouldn’t be all that surprised that there is evolved volcanism at Hekla, it’s surprisingly common in Iceland: Öræfajökull in its 1362 eruption emitted rhyolite magma (that’s still more evolved than dacite), as did Askja during its large 1875 eruption, and there are numerous rhyolitic products in the Landmannalaugar area, some of which were emitted in late Medieval time.
            Such evolved magmas do occur in a lot of so-called hot-spot settings, even Hawaii, where eruptions in the late evolutionary stage of a volcano often produce rhyolite. All you need is a magma that resides for some time in the crust, where it can evolve from basalt into andesite, dacite, rhyolite or the alkaline likes phonolite and trachyte.

        • Also, we should point out that since Iceland is not a subduction volcanism site the thickness of the crust is thinner than at the Mendocino. Only between 15 and 45 kilometers thick depending on where in Iceland you are.

        • So, you are saying with Scenario #2, that part of the sumbduction zones that ate the Rheic Ocean basin or the Iapetus Ocean basin when Avalonia formed may still have a shard slowly melting under the Hekla region?

          • That is one of the two more likely things that could have happened, but then on the other hand there is a general lack of xenoliths in Heklas lavas, and there should be quite a lot of it if it was a remelted slab of old crust.
            I prefer alternative one, that it is a corner of the adjacent microplate that is subducting localy, it would be less likely to form xenoliths, and it would interact better with the hotspot mantle and explain the high heat of Heklas andesites and dacites.

            Yet another thing is that Heklas first eruption was acidic rhyolite, and that is such an oddball that science right now do not have any answer for it, even less so than how the andesite/dacite is formed. According to every known model it should have taken thousands of years for the magma to form rhyolite, and on top of that, the rhyolite that erupted was much to hot in comparison with ordinary rhyolites. Here volcanology could do with a bright young one with fresh ideas.

            • I give you two observations. Of nearby volcanoes to Hekla.

              First, Eyjafjallajokull also erupts andesite magma. It’s also a volcano on the edge/corner of the Hreppar microplate, roughly.

              Then, there is Tindfjallajokull, a long dormant volcano. Also on the “edge” of the microplate, and it had one of the most massive eruptions in the Pleistocene in Iceland. Could it be that these two nearby volcanoes share (slightly) similar mechanisms to Hekla?

              Second, Torfajokull is the perfect example of a rhyolite volcano of Iceland. Could it be that Hekla first eruption has some helping hand of its neighbour?

              Finally I think its amazing to contemplate how was the first eruption ever of Hekla some 8000 years ago. Something strikes me as impressive: around that time, Bardarbunga had its most massive fissure eruption in the Veidivotn area, the largest lava field ever in the Holocene! And guess what lies just a few kms to the southwest of the spot of this eruption: Hekla. I find it amazing that both events occurred almost at the same time. I often wonder if they were connected. If you follow the fissures of Veidivotn further west or southwest you eventually end up, after Torfajokull, at Hekla, Vatnsfjoll and Tindfjallajokull. Some alignments there are perfect and make my eye brows raise their attention when I go to that region.

            • Irpsit, good one.
              Tindfjallajökull I have never gotten around to so let us leave that one be.
              Eyjafjallajökull has ordinary Icelandic basalt as driving magma type. Nothin inordinate there. Instead she has eruption far apart enough for the magma to evolve into andesites.
              If we take 2010 we first had basalt popping out, then andesite/basalt, then all of a sudden we had a batch or rhyolite. That one Erik K. suspected was when hot basalt hit a pocket of 1000 year old rhyolitic mush that got remobilized.
              Pretty much any Icelandic central volcano could eject andesites, but it is not of the same type.

      • In a way, the area between Hekla and Katla is also a kind of “triple junction” in formation.
        As the rift propagates southwest towards Surtsey, we end up with a “triple junction” somewhere around there. Well it’s not very neat, but its a spot where things could become or are already unstable.

        • Different type entirely, it is not a common triple junction. Instead you have one zone of rifting running from Grimsvötn down via Myrdalsjökull onwards via Vestmannaeyjar. At the side of that running up to Hekla you have the South Icelandic Fracture Zone.

        • Yeah, but Irpsit does have a point. As the MAR landfall area migrates to Surtsey, Katla inherits a triple junction. The area west and north of the newly forming MAR connector could become another microplate… and this could be an example of the early stages of how the other two formed.

          Oraefajokull could be a maifestation of where the line of rifting down through Askja will extend south for the next stage, taking over front row center for Bardabunga in a few million years as the relative location of the hotspot migrates that direction.

          • Shouldn’t it more be moving from Kistufell towards Kverkfjöll? And a new more easterly riftswarm will take over as the most active.

            • Yes. That would support the movement of the activity in the direction that I yammered about. I was speaking in a larger term of movement. But what you noted would be a leading indicator.

            • The hotspot is currently centered under Bardarbunga. Previously it was under Tungnafelljokull, Hofsjokull, Langjokull. Next locations will be under Grimsvotn (if not already!!), and then under Oraefajokull. At least that’s what I saw in a few papers. And it makes sense.

              So, I expect Oraefajokull will become much more active in the next thousand of years, possibly Kverfjoll, Esjufjoll, and Thordarhyrna also.

    • Not to mention the other huge volcano on the other side of the icecap): Oraefajokull.
      Everyone seems to forget that big one. Which is actually the biggest in Iceland.

      • Öræfajökull is indeed Iceland’s tallest volcano, but not its biggest volcanic system; compared to those huge things like Grímsvötn and Askja it’s actually rather small. And, let’s not forget this, big volcano does not mean it must necessarily also make big eruptions, it may just have had a longer lifespan or more frequent eruptions to grow bigger than others. Compare Etna to Vesuvius – Etna is three times the height and dozens of times the volume of Vesuvius, yet the latter is the potentially more violent.

        In the case of Öræfajökull, it is true that its first of two historically documented eruptions, in 1362, was very large and explosive, actually the largest explosive eruption in Iceland during history; its second historic eruption, in 1727 was much smaller and the magma was more mafic.

        Here’s a pdf link to Thorarinsson’s fabulous 1958 article on the 1362 eruption of Öræfajökull:

        Click to access Acta-Naturalia-Islandica-II-2.pdf

        • And not to forget Bárdarbunga/Veidivötn, Hengill, Katla, Theistareykjarbunga and Vatnafjöll. Not to forget also whatever volcano belted out Odhadhahraun. All of this related to size of eruption in the holocene, each of these volcanoes have gone bigger than Öraefajökull.
          Largest Explosive? Saksunarvatn tephra, VEI-6 from Grimsvötn but Öraefajökull was not the largest explosive eruption at all during settlement times, that honour goes to the 1477 VEI-6 caldera formation of Bárdarbunga. It just got a lot less credit out of having happened far from population and the ash moving in a fortuitous direction.

          Edit: I would also assume that Veidivötn banging at the same time also stole a large part of the show from Bárdarbunga.

    • Heh…. one of his least favorite songs is “Don’t let your babies grow up to be cowboys”

      But, as in most country music, there is a heavy reliance on emotion and attitude in the lyrics. This is one that our crew and the crew from the tender wore out at the “Cowboy Bar” in Palma de Mallorca. Not that any of us considered ourselves cowboys, but the whiskey did flow… copiously.

      Aside from a couple of sea stories that decorum prevents be from telling, all I can say is that after awhile, I grew curious as to why the sawdust that they had on the floor kept moving around. Why that place and not Texas Jacks? Because Texas Jacks wasn’t always open, and it was easier to get a cab from there. At Texas Jacks you had to navigate a few ally-ways to get to the road. Not something that all drunk sailors are adept at pulling off. It does take a certain skill set.

      (It’s not that there is anything nasty about the stories, it’s just that some of the people in the stories may have careers or relationships that could be adversely affected by it, even if I don’t name names.)

  3. Nice one Carl.

    As a layman I would say : if something is coming out of it (ash, lava, tephra, lapili) : eruptive – Sakurajima, Nishinoshima, Sinabung…

    If something has happened “recently” (to be defined – less than 10 years maybe) and something can happen (pyroclastic flow due to dome collapse) and there is still tectonic activity – active. – Soufriere hills – El Hierro – Soufrière Guadeloupe (last phreatic in 76 but nothing except some quakes since)- Campi Phlegrei, Vesuvius, Kick them Jenny

    If nothing happened for a some years (very low seismic unrest – stable hydrothermal activity): Dormant – Montagne Pelée – North Tenerife zone – On that line if someone can explain to me the hotspot theory of the canaries in view of the last Lanzarote eruptions, I’m game.

    If nothing happened for a thousand years and the geology say it’s dead (no hotspot, not a subduction zone)- you can consider it extinct , depending on the geology – Olot volcanic field in spain, Auvergne volcanic field in France, Eifel volcanic field in Germany (the 2 last ones could be challenged, if only to please the Laacher See loonies) ( for sure the old volcanoes around cap d’Agde)

    Of course all that can be challenged as there are many type of volcanic eruptions – if you take the Canaries, the cones are monogenic , so if you take Chinyero (early 20th) – it’s extinct, but the Teide zone is dormant (or lowly active as there was some seismic unrest only a few years ago).

    So maye all this is a bit too wide and there could be some different definitions for different geologic situations.

    It is true that you cannot say that there will never more be some action in Martinique because the plates are still cavorting together. However, the Auvergne volcanoes are maybe dormant because the hot spot is not longer there ?

    Iceland is also a separate situation, I wonder if there was some comparison of the icelandic and african rift volcanoes ?

  4. Great post, but poor Jennifer must have now got lost among so many brilliant comments. Take your time, Jennifer, it will come by and by…. 🙂

  5. Honestly, I think the only time you can announce a volcano entirely 100% dead, is when you can be sure that the magmatic source has completely dried up and gone away from the volcano.

    There are quite a few volcanoes that went completely inactive for over 10,000+ years, only for them to become active later on. As long as there is potential to generate magma in the area below the volcano, it’s certainly possible that a new injection of magma will return later on and exploit the same weaknesses in the crust that were already there as it rises.

    • agreed…. 10k years is nothing for Mother Earth, which is kind of sobering as you can fit all of written human history within 10k years, and this is really just the interval between lunch and dinner for a young growing volcano. The mature volcanos get into the ball park of 100k years and the volcanos in the retirement home are up to 300k years and more. After a while erosion wins and you have nothing much left. Understanding the sheer scale of geological time is probably the hardest thing of all to understand.

  6. In my research for my post on the Columbia basalts, I
    Noted something. Scoria cones. Quite common, but
    Active millennia after the main event. We have several
    in a 80km radius, that are less than 10,000 to younger
    Years old. There is one that is on the summit of a local
    Mountain the mountain is mostly basalt but yet,the cone is there
    It is estimated to be less than10,000 years old. My point, is this:
    you can not be sure if system is completely dormant.

  7. The ever diligent Islander noticed that Vöttur is back online showing quite a lot of tremoring.
    And that would explain all those anomalous reading we have seen on KSK, HUS, GRF and KAL since they are the stations surrounding VOT.
    Vöttur is the principial SIL for Thordharhyrna volcano, and the fissure swarm of Thordharhyrna rund almost all the way down to Katla, so it also nicely explains that tremor reading. Last eruption at Thordharhyrna was a VEI-4 in 1910. Eruptions previous to that was 1902, 1887, 1823, 1784 and 3500 years ago.
    It is one of the few volcanoes that often co-erupt with another volcano, in this case Grimsvötn. This lead to Thordharhyrna being placed on the Grimsvötn Fissure Swarm, but now we know that it is on a Fissure Swarm of its own to the east of Grimsvötn. Co-eruptions occured during the 1902, 1823 and 1784.

    There is a transverse rift running from Thordharhyrna up to Hámarinn volcano. This rist skirts the southern parts of Grimsvötn and Loki-Fögrufjöll volcanoes.

    • I got a cod in my head again. I was unclear. HUS is west of Thordharhyrna and VOT is east of Thordharhyrna.
      Here is a good map showing location of the Kerlingarfjöll, Grimsvötn, Háabunga, Thordharhyrna and Hágöngur volcanoes. Not marked out are Geirvörtur and Éldgigur, it is though unclear if Geirvörtur are a central volcano (erupted several time or not). Éldigur has erupted more than once, but might be the annoying occation where the lightning has hit more than once. If it ever erupts again we should know.

    • nah that bad, a baby cod, almost still a quality kaviar 😉

      I think this shows such when an system is pressurizing, hot material has been injected in (soft) layers, then starts boiling the layer abowe (and thus must be abowe the 2,500 m pressure line GeoLurk calculated so often, else it can not boil). It might be something or nothing. To me it says area is possibly more active and might show wet (more injection) quakes next time around.
      *not expert*

  8. Just noticed something fun on Google Earth, seems like a couple of cauldrons have formed to the west of Thordharhyrna right under Vöttur.

    Image and video hosting by TinyPic

    • nah, now you make me dizzy.
      Locating that fast is as in Acrobatic jet,
      doing manuvers in area at supersonic speeds at +9G
      Gets me even dizzier 🙂
      Slowly. Put in a grid and some places of recognition, else its a whiteout!

      • My PC is a biplane-taildragger (can not handle GoogleEarth fast enough).
        So BBGN (and not too soon I guess)

  9. Okay, Tangential OT. (OT, but about the subject in question)

    Bárdarbunga → Bards Bulge. Any relation to the Bardi story? You know, the guy that Katla killed?

    • Sakurajima has been *very* quiet today, as far as I’ve seen. Continuous heavy steaming from the Showa crater (the heaviness may well be an atmospheric effect) but no visible ash emissions or vulcanian activity (although I could easily have missed events).

      This long a quiet period is usually terminated by a larger than average BANG…

  10. Nice article Carl. Loving the way you sneaked Hekla in – not exactly your typical stratovolcano!
    A bit like my rugby match reports that always manage to mention my son even if he played crap 🙂

    One small point I would make for clarity: while different countries may have their own alert levels, the international (ICAO) colour-coding of volcanoes relates to the level of danger they present to aviation, rather than their actual state. Admittedly, the two correspond in some cases (erupting = red) but there are many, many volcanoes that most people would class as ‘active’ that are coded green or yellow. My old friend Bezymianny, for instance, is currently at yellow, but is steaming away quite happily, and I would doubt anyone would call it anything but ‘active’.

    Explained here: http://volcanoes.usgs.gov/activity/alertsystem/

    Long-dormant volcanoes don’t have any colour-coding at all.

    • I used Hekla as an example of a formative Strato, kind of to give me room to point out that there are various ways for a volcano to go without having to go through all of them… Eh… I just love Hekla 🙂

      Yepp, ICAO are the ones seen at the VAAC reports.

  11. It’s the same old story: never trust the last couple of minutes of this graph, because the graph shows a gliding 5-minutes average, which means that all that is less than 5 minutes ago is not averaged with the previous bit and can show in a rather exaggerated manner (but disappears or diminishes once the next 5-minutes-average is visible). Not easy to explain and maybe still less so to understand, but … never trust the last couple of minutes on this graph unless the trend continues and continues and continues 😀

    • In any case, the situation at Etna is rather quiet, maybe this latest series of paroxysms has already ended (or is about to do so soon, after maybe one or two further paroxysms in the next days to weeks); we know that only a limited quantity of magma has entered into Etna’s feeder system a few months ago, and since late-summer there’s no sign of new magma coming in. This is based on gas emissions (mostly carbon dioxide, which is released from magma at about 15 km depth) and ground deformation. We’ll have to wait for a new arrival of magma from depth (and thus, a new CO2 signal) and then a few more weeks and then we may have more paroxysms, or – if the quantity of new magma is much larger than those that have come in in the past 3 years – some more intense activity either at the summit, or if the volcano is destabilized by the large magma volume coming up through the system, a flank eruption.

  12. For the Tolkien oriented, I saw The Hobbit yesterday and from my humble point of vue it’s worth viewing. The only point I found was that the lonely mountain dome shape was a bit on the unstable side.

    • I’ve been saving up the LoR and the Hobbit trilogies for when my son is old enough to see them. I really should have gone to see them long before now because I know (or better, knew) a couple of the people involved in them. One even got an Academy Award for her work on LoR. She was a cool friend of my sisters who did some pretty amazing sewing work… She went on and did the costumes for LoR and the Last Samuari. My best mate from school did location scouting for the Hobbit… guess this is the typical Kiwi thing where everybody knows everybody else twice removed, kind of.. Still, I am kind of scared I am going to be disappointed by the films because I know the country so well.

        • I dunno. I haven’t seen them yet so I can’t say. But if the landscape is too digitially altered from the real thing that would kind of annoy me. I’m a bit protective of my own version of NZ. Some films do it well. The opening scene of Jane Campion’s “The Piano” is pretty good. The wild west coast beach and a grand piano dumped on the sand. The amazing juxtaposition of European pretensions to culture and the raw untamed powerful land. I just hope Peter Jackson hasn’t stuffed it up.

          • Ah Ok. I found the Hobbit village a little too cute. But in many scenes the landscape was just stunningly beautiful. I think often ( not always) the movies were a good advertisement for NZ.

      • Look at the bright side. You know what the Movie stand in for Mt Doom can actually do. After all, it was the Hobit launcher that hurled debris 6500 meters straight up into the air.

        Just from the phreatic detonation… Steam Power baby!

        • Oregon is much like the south Island. Similar scenery. NZ is about the same latitudes south.
          Oregon is used for location shooting-Westerns,mainly..
          Nothing on the scale of The Ring or The Hobbit.
          “Paint Your Wagon” was the most notable. Never
          met any one who saw it in the theater….

          • Yeah, the problem with that is that when the movie was cropped to 4:3 using pan and scan, much of the shot composition was lost. That’s where you can take in the beautiful vistas.

            Here is what appears to be a letter box format version of it.

            • Thanks, Lurk! Enjoyed that. My pop
              was an extra on the set-he drove a six
              horse hitch freight wagon. Got cut out.
              Area is the Eagle Cr. drainage where
              “No Name city “was. South Wallowas.
              Anthony Lake ski area too..

            • What a visionary, I agree with him. I really do.
              If not else for the insanity of building something so inefficient.

            • I do not agree really, walking keeps you fit and lean. It is also the best form of cardio-vascular excercise.

              It though suck as a means of transporting heavy items a long distance.

            • One thing I do not miss is being called out at 3 am for “manpower assist.” That’s a curt and sanitized way that dispatch meant. “They can’t lift the patient into the back of the Ambulance”/// which was about half the time. The other half was that the EMT was about to collapse doing CPR and they needed a hand. Got sent for the assist the sheriff’s department once. They needed a ladder since the suspect had fled to the roof of a business. It made complete sense to not follow him through the access scuttle, you would be a sitting duck. Keep him pinned up there and use a ladder to get at him from a different route.

            • I have watched one of those…
              I was thinking why on earth do they not have one of those portable Engine lifts. They are on wheels, and they can lift 0.5 tons. And if the patient ways more than that they will anyhow need a construction team to take the patient out with a skylift via a hole in the wall.

            • Not attempting to being trite… but I can answer that.

              Fine motor control.

              Remember, an actual human can react to shifting or sqiggly loads better than a machine. A machine can only lift or move in a manner in which it was designed. If the load shifts off it’s lift axis, it becomes unstable. A human can adapt. If the mass happens to be greater than the machine can move, your stuck, and working around this thing (machine) that is now in the way. Using humans, if you encounter that, just throw more of them at the problem and you have greater lift potential.

              Show me a lifting machine that can quickly be re-purposed to holding an IV bag or taking over the performance of CPR. Or deal with getting a relative out of the way. I’ve never seen a four ton floor jack able to console a distraught relative.

            • I guessed it was something like that.
              I guess the answer would be exo-skeletons Aliens-style. I have though always wondered why ABB never made more of them than the prototype that was used in the Aliens movie.

            • I think that the exoskeleton idea would be workable if they can get it down to a size that is easily stored and put on. And more importantly, that does not scare the hell out of people.

              They are getting there with the research though.

  13. I have just met Ivar. Ivar is a storm.
    “Hello Ivar!”

    I am just happy that I cut off the part of the tree that poked a hole in my bedroom window during the last storm.

      • No wonder I slept like a baby. For some reason nothing makes me sleep as a really good storm if I am onland. It is a flaw somewhere in my genetics, it could be lethal if I lived in Lurkings neck of the woods.

        • Might be that we sleep soundly until, “Hm, that didn’t sound right” and we awake. I awoke very fast when I got a branch poking a big hole in my bed room window…

      • Could be. I’ve slept through missile loading and launching exercises, and one thing I miss is hearing pumps in nearby spaces.

        Last night I had to get a shot of whiskey to doze off. Actually used it for what it was intended… as a sedative. I kept flopping around in bed until the whiskey. Had a glass of icewater as a chaser. The insomnia may be related to the fact that I drink tea and coffee to no end all day long. I switched to unsweet iced tea years ago, and quit having weight issues. Soda is nothing but sugar water, and once you get the sugar in your system, the body is just going to try and figure out what to do with it. Generally, it packs it up and stores it for future use. (adipose tissue)

  14. If Bardabunga and Hekla had major eruptions 8,000 years ago, what else was happening then? This was the time of the Flood, as it happened around the UK, when Dogger Bank was submerged, and I believe Storegga collapse also occurred then, and it was the end of an ice age.

    The Mid-Atlantic Ridge may be a factor, I suspect. I wonder whether it rose across a wider area and raised more land in combination with isostatic rebound, and then after such a massive eruption as Bardabunga it subsided?

    Volcanology Maps of the earth can show warm areas which are getting larger. How is this measured?

    It would seem to make it worthwhile measuring variations in heat levels where people have heating systems from deep in the earth. We have a local school which gets all its central heating from a deep source. The school is a model of renewables and green energy.

    • I do not see anything odd really. All those valve openings taking place is either indicative that the equipment is faulty somehow, or that they have a new technician who has fallen in love with that button. HEK might be a bit unusual, but not enough for me to believe anything is happening. If HEK and BUR had been moving apart in jerky fashion then I would have been more excited.

  15. Carl might be experiencing a power shortage due to the storm he said Hello to yesterday. But no worries, Chryphia and me got a post scheduled to go in at the normal friday time.

    • Nope… Fully electric. But I dreamt it was saturday so I turned off all of my alarms in a semi-sleepwalk and went back to bed. Sleep deprivation creaping up on my old bones. Christmas will be sooooo nice.

      • Oh ok cool
        Chryphia and me were not sure if you could even go online
        so we prepared a post and even riddles

        • I just saw the news. Seems like a slept through a big one. 🙂
          Okay, so I get a friday off. Yeah! :mrgreen:

          Off then to ponder Lurkings Pidgeon!

            • I am just happy 🙂
              Now I will go off and cook some chocolate, start a fire in the fireplace, and sit down and read up on things related to Lurkings Pidgeon. Later when the Riddles appear I will make a stab at them. And fail miserably 😉

            • I am going to listen to a lecture by the only person who actually has a steamdriven interstellar spaceship… Also one of the 3 people alive I append the word genius too… the other two being composer Arvo Pärt and physicist Edward Fredkin.
              The one and only Captain Bruce Damer…
              Image and video hosting by TinyPic
              Steampunk anyone?

            • If anyone is up for it…
              Seriously scientific techno-hippie galore on his homepage.

              Trust me and Mike Ross on this, without this guy your lives would not be the same, you just do not know it yet. (Serendipity and the world is a small planet, Mike and me both know Dr Bruce, but highly independently)

  16. REK is fully electrick too, but HAU area is “out” (power-outage due the storm), so SIL is out 😉
    Storm seems over at the moment (center of Lo is here, do not know if storm again when it passes). Not much going on. Save this. Kárasker SIL shows steady unrest (rather than intermittant) as last days/weeks http://hraun.vedur.is/ja/oroi/ksk.gif
    Maybe the influx is now steady, possibly towards Öræfajökull even
    *not expert*

      • Reminds me of one of the funniest games I ever played. It was BF1942 on the Stalingrad map. The game has a notification system that prints in the upper left corner [name] was killed by [name]. Someone had taken it upon themselves to make their player name “a little girl.” So when they made a kill, it would read [name] was killed by a little girl. We laughed our asses off at that one.

        At the time, DICE had yet to come up with a good equipment fit for the Heavy Assault player class, other than a SAW and a few assorted odds and ends. One deployable were the sandbags, allowing you to erect cover for you and your squad. I found that the sandbags could be deployed on stairs, and took great delight in having some of the enemy team chase me into a building and then when they headed up the stairs, I would hop over them headed down, spin and drop a sandbag barricade, effectively trapping them on the stairs. The only way out was to sit around and wait for the deployable to expire (several minutes) or to go the rest of the way up and crawl out the 4th floor window and risk being sniped.

        It was a pretty cumbersome deployable, yet vehicles could still drive through them. “McPlowed,” one of our other players would usually spend the entire map racing around looking for people to run down with the jeep. I guess that was part of where he actually lived, (LA) and was a release for his aggression against pedestrians.

        By far, my favorite tactic was to set up in a 2nd floor window and suppress activity on the streets. When the enemy team got fed up with it and came up after me, I would drop a grenade and jump out the window. The fall damage was not extraordinarily high and a medic was usually nearby.

        Once you learn the controls and the game mechanics, you can have quite a bit of fun doing the unusual to the enemy team.

        (such as “TheGit’s” fetish for shooting snipers with anti tank rockets. Last night I was in a MAX suit fitted with AA and was on the next hill over from his anti tank tripod, covering him from aircraft. Four “infiltrator/snipers” came up after me. I whacked the first one when he tried for a melee/knife kill, but Git could see the other three moving on my position. I made my way down hill, leaving them open to TheGits rockets as they tried to follow. He picked them all off. The funny part was that they didn’t clue in to what he was doing.)

  17. Interesting, I just calculated the magmatic loading of Iceland based on spread rate.
    0.36 cubic kilometers of DRE per year. If we then calculate that 10 percent is the average amount being ejected then we get about a VEI-4 every 3 years (or lava-equivalent).
    Of course we are not seeing that so there have the explanation for the basalt floods that pop up now and then.

    I also have a whopper of a Friday “Duh, what volcano did that?” for later…

    • No, err, but I am not especially good at math… Your figure should be 0,40 km3 injected (emplaced) due preading (but 10% do not stop in ground), leaving rock equivilant of 0,36 km3 behind. But then there is uplift too… or sinking in parts (netto what?)

      • I had actually counted in the 10 percent allready, and it should be 90 percent staying in the ground… or more, but it is a figure given in the books. 🙂

        The uplift would be netto zero since I am only counting crustal magma, and over time the uplift caused by the hotspot goes away as you mentioned.

  18. Pidgeons… You are having a good time in the park… “Whatcha gonna do when they come for you?”

    Image and video hosting by TinyPic

    • Our local sea-gulls have a ‘guano’ rock. It is white when all the rest nearby are dark grey.

      They also seem to have ‘target practice’ on the whitest bodies on the beach in summer….

  19. It is supposedly good luck to be sharded on by a bird. Happen to me once right before I went into an engineering class to take an exam. Ended up doing well on the test, though I was really pissed off entering the building

    • Opposite for me. I was on the way to History of the Old Testament (relating middle east population movement and society to the Old Testament).

      I took it as a sign (affirmation) from God that I needed to find something else to do.

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