Bárðarbunga – Nature of the beast

Dyngjujökull. Photograph by Eggert Norddahl. Used by explicit permission. If you wish to use the image contact Volcanocafé via our email.

Dyngjujökull. Photograph by Eggert Norddahl. Used by explicit permission. If you wish to use the image contact Volcanocafé via our email.

First let me write one thing, and that is that we are not in Kansas anymore. And with that I mean that we are in totally uncharted country. Icelandic Met Office has the best volcanologists on the planet, and they pretty much never make a mistake. They are quite simply the best and their reputation at this site is set in solidified lava.

So, when people like that in an hour first states that a small eruption has started and an hour later recant on the statement it does not hamper our confidence in their abilities, it is instead a sign of how “out there” what we are seeing right now really is.

What is happening now is really like if you walked down a familiar street and turn a corner and find yourself in the fabled Land of Oz

So it is time to sit down and calmly go through what is happening, and what has happened previously. Of course this will just skim the surface, but hopefully it will be enlightening.

In the beginning

Bardarbunga. Dyngjujökull. Photograph by Eggert Norddahl. Used by explicit permission. If you wish to use the image contact Volcanocafé via our email.

Bardarbunga. Dyngjujökull. Photograph by Eggert Norddahl. Used by explicit permission. If you wish to use the image contact Volcanocafé via our email.

There is of course not any beginning to our story, instead this story has been ongoing for 14 million years, and what we are seeing now is just a single word in the entire story of Iceland’s birth and growth.

So, let us just say that Bárðarbunga is the largest volcano of its type on the planet, and that it has had the largest lava flood eruptions in the last 10 000 years, and that it is prone to have what is called rifting fissure eruptions.

A rifting fissure eruption is when a large part of the fissure swarm “rifts”. Rifting is when a large part of a fissure on Iceland opens up all the way down to the mantle and as that happens a large scale decompression melt starts in the mantle and obscene amounts of magma is formed and pushed upwards filling the void that is created as the tectonic plates move apart.

Bárðarbunga has had more than half of the Icelandic rifting fissure eruptions, and of course the largest. Last time that happened to Bárðarbunga was in 1477 when a fissure opened up at Veidðivötn that extended all the way down to Torfajökull (causing an eruption there) and it also caused a VEI-6 caldera event at Bárðarbunga central volcano. The next time it happened was at the 1783 Skaftár Fires (Lakí) that happened on the Grimsvötn fissure swarm.

Back in 2010 Icelandic Met Office issued a statement that a phase of increased volcanic unrest was to be expected. These phases are due to Icelandic volcanism being cyclical, and there are two cycles. One is the Icelandic Mantleplume activity cycle; the other is the Icelandic MAR rift cycle. This time around both cycles would coincide.

Back then I also hypothesized that the rapid melt of Vatnajökull glacier would increase it further due to isostatic rebound (land lifting due to weight on top disappearing) would cause increased decompression melt.

Bárdarbunga. Dyngjujökull. Photograph by Eggert Norddahl. Used by explicit permission. If you wish to use the image contact Volcanocafé via our email.

Bárdarbunga. Dyngjujökull. Photograph by Eggert Norddahl. Used by explicit permission. If you wish to use the image contact Volcanocafé via our email.

All of this made me start to look for signs of unrest in the southern parts of the fissure swarms, and about two years ago I saw an uptick in earthquake activity at both Skaftár fissures and at Veidðivötn fissure swarm. Problem is just that there is extremely little scientific work done about these, the largest eruptions of their type on Earth. Basically there is only one good paper out there. This led me to do my own research and write a series of articles in here about the Skaftár Fires. I seriously suggest everyone to read those to get a better picture of what is happening now. My own research gave results at odds with what was previously believed about large rifting fissure eruptions, but it was based on enough data to make me believe in the validity of the result.

Around this time I and GeoLurking started to look sternly at what was going on in Iceland, and especially to track earthquakes in odd spots related to the fissure swarms.

Slightly more than a year ago odd small swarms started to appear in the area we are now looking at, and I concentrated on those that happened on the Bárðarbunga fissure swarm. Chiefly among those I noticed small swarms of deep earthquakes (20km+) under Kistufell and Trölladyngja. At the same time I noticed two odd swarms at equal or even greater depth at two points out in nowhere land. I thought those two swarms was just some odd volcanic activity related to unknown small volcanoes. Interesting, but not what I was on the prowl for.

As the months turned into a year of constant and slowly increasing activity I felt pretty sure that something was going on, and that it was time to write about what I thought would be an upcoming eruption on the Bárðarbunga fissure swarm. I though delayed writing the article for two weeks while debating it with a couple of the editors in here. In the end I decided that it was time to write about the upcoming event.

As things go I must have looked like a blatant psychic, the swarm started just a few hours later. Obviously most tree stumps are more psychic than me; instead I used science at every corner. I am though happy to have been the first to spot what would come.

What I find interesting is that those two deep swarms out in nowhere land are exactly at the spots where the meandering intrusion changed directions. That is just a bit too much of a coincidence, so I now think that those where signals of what would be coming, just that we missed them.

Now, let us look at the present.

Seismicity

Image from Icelandic Met Office. Corrected earthquake seismicity plot from onset of the swarm showing the collapsing caldera and the propagating intrusion.

Image from Icelandic Met Office. Corrected earthquake seismicity plot from onset of the swarm showing the collapsing caldera and the propagating intrusion.

Let me first start with the seismicity, in my Skaftár Fires series I wrote that we would be seeing almost constant M4 and M5+ earthquakes in an upcoming larger event in one of the fissure swarms, right now we are seeing exactly that. I do suspect we will see more of that later on if the fissure actually starts to rift. There are no signs of the seismic activity abating now, I would expect it to continue or even increase.

What is interesting is that at the current direction and speed of propagation the swarm will reach Askja in 4 days.

GPS orbits

Image by Icelandic Met Office. Kverkfjöll GPS Genggisig (GSIG).

Image by Icelandic Met Office. Kverkfjöll GPS Genggisig (GSIG).

 

Image by Icelandic Met Office. Dyngjuháls GPS-station (DYNC).

Image by Icelandic Met Office. Dyngjuháls GPS-station (DYNC).

Dyngjuháls (DYNC) has changed its orbit slightly and the rapid north motion has shifted to a slow south motion as the intrusion has passed the GPS-station. The westwards motion goes on unabated and the station has now moved 185mm in that direction.

If we look at the Kverkfjöll station named Gengissig (GSIG) we see 90mm of southwards motion combined with 180mm of eastwards motion.

If we now combine the west motion of DYNC with the east motion of GSIG we get a total rifting of 365mm in 8 days. That is an average of 45mm per day, or the equivalent motion of 14 years of normal Icelandic rifting done in only 8 days.

These two stations are though a bit distant from the rifting fissure, so the rifting is obviously larger than that. Most likely the rifting right on top of the dyke is in the order of a meter or more. This means that more than 0.8 cubic kilometers of magma has intruded.

Now, even that number is on the low side since the “lips” of the rifting fissure are still closed. As the lips open the total rifting will most likely be closer to ten or twenty meters if it occurred now. And the longer the intrusion continues before onset of eruption the larger the fissure opening will be.

Other signs

Except for this there are so far no other signs of volcanic activity. There is no gas measurements (if they are taken) indicating an eruption being close, neither are there gas or particles in the glacial run off indicating melting ice from an eruption.

Now, let us move on and talk about what type of an eruption will be most likely at this juncture in time. Remember that this might change as things evolve further.

  1. The seismic activity decreases and the intrusion lose momentum and no eruption happens at this time. For every day this scenario becomes less likely. In the beginning most scientists stated that it was fifty/fifty that an eruption would happen. The chance of it not happening is now probably below ten percent chance.
  2. A small sized eruption at Bárðarbunga central volcano. This is now a very unlikely scenario since the pressure is decreasing inside the caldera.
  3. A large phreatic event in the caldera due to magma chamber collapse. This is an increasing risk as the roof of the magma chamber is currently lowering causing those large earthquakes noted in the caldera.
  4. A small scale fissure eruption like the 1996 Gjálp. The risk for this has significantly decreased as things have moved on.
  5. A medium sized prolonged rift episode like the Krafla Fires. This is currently the most likely scenario.
  6. A large rifting fissure eruption. As time goes by the risk for this increases, currently I think the risk is around 10 percent. So, I guess it is time we start talking about this in the open and what it might entail. I once again recommend reading my series about the Skaftár Fires.

Rifting fissure eruption

Dyngjujökull. Photograph by Eggert Norddahl. Used by explicit permission. If you wish to use the image contact Volcanocafé via our email.

Dyngjujökull. Photograph by Eggert Norddahl. Used by explicit permission. If you wish to use the image contact Volcanocafé via our email.

Let me be clear about what this is, it is about as large as an eruption is likely to be in this geological era. Only full scale trap formations and supereruptions are larger.

But let me start with why I think this is an option. Foremost the length of the fissure, at 40km it is definitely long enough to be able to sustain a large eruption. The fissure is also showing signs of having opened up down to the mantle at places, and that would mean that it is possible for rapid decompression melt to occur, and that is a necessity for a large rifting fissure eruption to access large enough quantities of magma.

The most surprising sign though is that this rifting fissure is not following a single fissure swarm. This is totally unsuspected behavior that nobody has even guessed at in their most feverish fantasies. The initial intrusion charged straight out of the Bárðarbunga fissure swam, passed barren land in between fissure swarms and connected with the Grimsvötn northern fissure swarm, followed that downstream and then once again changed trajectory and entered the fissure swarm of Askja.

This means that potentially the intrusion might be feeding on the 3 largest Icelandic volcanoes if the fissure evolves a bit more. If this actually happens all bets are off and we would be most likely talking about a rifting fissure eruption with explosive components.

If the intrusion continues to move forward in this direction it will enter the caldera of Askja in 4 days. Problem here is that Askja is known to have pockets of rhyolitic explosive magma, and if those pockets suddenly reheat from the new hot magma things could get interesting fast.

Commenter Irpsit has pointed out that the area seems to be more prone to form single stage eruption volcanic shields instead of rifting fissure eruptions. I think this has great merit on what we are seeing, and that it is the single most likely thing. It is though not necessarily a better option since it would entail years and many cubic kilometers of highly gas rich magma coming forth at rapid pace.

Above I have touched on the worst case scenario. If that happens we will face temperature changes, ash and voluminous gas clouds. But one thing is certain, it would not in any way threaten life on earth, it would not even put a big hindrance on your daily life. Get real, the world will not end like this. But, expect a bit of nuisance.

CARL

Prequel to the Skaftár Fires series – https://volcanocafe.wordpress.com/2013/05/29/central-volcanoes-of-vatnajokull/

Part one of the Skaftár Fires series – https://volcanocafe.wordpress.com/2013/06/05/laki-deconstructed-anatomy-of-an-eruption/

Part two of the Skaftár Fires series – https://volcanocafe.wordpress.com/2013/06/10/laki-deconstructed-grimsvotn-and-beyond/

Part three of the Skaftár Fires series – https://volcanocafe.wordpress.com/2013/07/31/laki-deconstructed-a-timeline-for-destruction/

Volcanocafé business

I post this here so that this will not disappear in the general hubbub of comments. There will be emails coming soon to Bruce Stout, Diana Barnes, Evan Chugg, Graniya & Renato Rio. So please check the mail-boxes you have registered here.

 

836 thoughts on “Bárðarbunga – Nature of the beast

  1. Thanks so much for this for me so clear update ++ – as i will be traveling for the first time to Iceland this Wednesday, all happenings began for me only last week with the updates – so yes, you guys keep me more relaxed than I would have been otherwise – so now I started packing, opening a blog and a twitter account to keep everybody at home and abroad informed, and I referred especially to this article for all the other volcano dummies in my near surroundings

    • Hi Carolien. I am also a first time traveler to Iceland, leaving this Saturday. I have also read this blog for the past week and have to say a big thank you to all contributing!! I am definitely more relaxed following the discussions. My friend from the United States whom i was supposed to meet decided to cancel her trip. However, I decided to go ahead alone and I’m sure I won’t regret it. I wish you happy travels!

      • Good decision! You will be safe in any case, and if an eruption happens you might even be able to watch some of it live so you will have something to tell your grandkids 🙂

      • She cancelled ??? What a lost opportunity to – perhaps – experience an eruption in the safe-as-houses hands of Icelands’ experts.

      • Thnx for sharing Kat, same to you. For some reasons I feel very confindent – Having lived in Turkey with the frequent minor euartquakes and some major ones, made me, just as living with snakes and scorpions nearby, more awake and less easily to scare. So looking forward to both the traveling with my 21 yr old son and to share the experience of the beauty of nature, I guess I am in a wau both curious and thrilled to go under these more ‘special’cricumstances. have a great time!!

  2. Gisli Olafsson ‏@gislio

    Earthquakes overnight north of #Dyngjujokull have not moved further north – main activity 4-5km north of edge of glacier #Bardarbunga

  3. the reduction in 2+ quakes is very noticable, 1 1/2 hour since last one?. Does the lava flow easy now? – or is it calming down?

    • To me it seems to be calming down since the EQ’s are not moving further north according to Gisli Olafsson. But I’m no expert.

      • Could it be that magma has found an area of rock that hasn’t been previously fissured by either Askja or Dyngjujokull / Bardarbunga and is just ‘piling’ up behind until enough gets there that the rock melts or fractures. I’d say if that is the case there’d be a biggish 4.5+ earthquake when it breaks through.

        But nobody can really say what is going to happen.

        • I’m no geologist but I’m a fluid dynamics engineer and to me a “piling up” situation would result in higher pressure and therefore higher intensity EQ’s. If the magma on the other hand would encounter cavities and flow more freely, then it would result in lower intensity EQ’s because of the lower pressure.

          But once again, I’m no expert in geology.

    • I have a hard time following the google translation of the article. But it seems to me the article is confirming what I speculated about a few minutes ago; that the decrease in pressure and EQ intensity is a result of the magma flowing into the Askja fissure system?

      • Looking at the harmonic we’re within hours of another surge, it’s been doing this same pattern of going quiet before the next break-out, NNE for a few cycles now. It’s 40 km from Askja and may never go there. It depends on what the mantle divergence has been doing for the past few hundred years since the last episode (which alters some with each new plume) because the crust is just responding to the induced tension field, which it needs to relieve via pulling apart and reforming. Where it needs to do that, is anyone’s guess. It may jump away from Askja and nothing even happens there. But why guess?

    • “Hann hefur færst eilítið í norður, er kominn 5 km frá norðurjaðri Dyngjujökuls og hann er nú kominn inn í sprungusveiminn sem tilheyrir Öskju,“ segir Gunnar.

      Through Giggle translate:

      “He has shifted slightly to the north, it’s 5 km from the northern edge Dyngjujökuls he has come into the crack my servant belonging cardboard, ” says Gunnar.

      Er…

      Please can any Icelandic speaker translate that? Thank you…

        • It hurts when you only have cardboard to serve when you need to clean your crack. Bad thing when you know shit is on the way. Stay away from Bardarbunga.
          Indeed, what is not clear about that?

        • Let’s see now, “crack my servant belonging cardboard” – is the magma on drugs? Is Gunner’s trusty valet, from the village of Cardboard, nicknamed “Crack” because of his former career in the safe-breaking business? There’s a world of possibilities in that phrase! 😀

            • The scientists think that the intrusion has entered the volcanic system (i.e. the dyke system) of Askja.

              That could mean that the magma would now flow within an old dyke of Askja.
              Something which would perhaps explain that the number of earthquakes is reduced now. (no expert)

              I’ll translate perhaps later the whole text, if I have time – or perhaps Mbl will do it themselves.

          • Askja, when not being translated as a Caldera (or when not referring to the mountain, usually means a small container or box. These are usually made of cardboard, hence the frequency of up-comings.
            Calderas are box shaped, sort of.

        • So “crack” is fissure? What about the “servant belonging cardboard”? That doesn’t seem a very appropriate description of Askja to me… 😕 😀

          • Askja is either the cardboard or the box (while the box, I think, has also been used for crater elsewhere) . I think it means the fissure that “serves” as magma path for Askja. One really needs a good portion of imagination 😀

            • So very true, Granyia! Meantime it makes for wonderful humour. Some favourite examples from this article: “But she picked up between 2 and 5 After 5 drew from her again.” and from http://www.ruv.is/frett/breytir-kenningum-um-bardarbungukerfid “Pall Einarsson, professor of geophysics at the University of Iceland is the development of an earthquake” (That makes Pall a pretty special person!) and “Hole lava is considered to have expired in 1797” (is this lava that looks like Swiss cheese?) and “Most likely this would sprungugos” (can let the imagination run wild on this one!) and “a review of the movie that has been made of the Bárðarbunga system” – Bárðarbunga the film star!

      • Lets explain this sentance… Seems Giggle ripped it open beyond recognition.
        “He has shifted slightly to the north, it’s 5 km from the northern edge Dyngjujökuls he has come into the crack ´my servant belonging cardboard´ (Askja = Box; Cardbord Box), ” says Gunnar.

  4. A couple of hours without big quakes just don’t mean anything in such a context. It’s abolutely no idication for something big in preparation or something calming down. It’s like trying to interprete one thunderstorm and come to conclusions concerning a climatic evolution.

    • The underground is not linear as a medium. Don’t try to see the evolution like the track of a motorbike on a circuit, it’s more like a dirtbikes trajectory during a race. Surprises lead to other surprises – only big trends that last for some significative time allow us to understand things. Jumping after every tiny detail before we can put it in the larger context will lead us to misinterpretations.

      • Oh I think this is definitely a nachos kind of event! Went shopping today and now have enough food for at least 4 days – will go again Wednesday if necessary to see me over at least the next week…. **adding nachos to shopping list….**

  5. IMo reports 270 million cubic meters ( 0,27 km³ ) of magma intrusion since the 16th. What’s the percentage of possible eruptive part ?

    • It’s deceptive though – in the last 48 hours there have been 2456 earthquakes – many of them small (225 under M1; 1468 between M1 and M2). Of the larger ‘quakes, there’s been 688 between M2 and M3 and 75 of M3 or larger. That’s a lot of ‘quakes! The magma intrusion is generating most of them at the moment – that magma train seems hellbent on getting to Askja as soon as it can! 😮

      • Very well said.
        I think you have a point with that. We should follow that path and maybe this will turn out to be the best explanation for all that happens since more than a week.

  6. I am fascinated by all of this. I initially joined because I have a flight to Iceland next week… but now I’m just coming for all the epic volcano teachings. I’m learning so much! Looking forward to continue reading this blog from now on 🙂 Keep up the great work!

  7. The Laki articles are indeed excellent read. Thank you very much Carl.
    Looking from where we stand today it seems to be almost dwarfed by current activities. Unless of course such dykes have been created all the time and we just don’t know about it because we had no means to measure besides witness reports. But this being such a remote area I think a 5 would not necessarily be registered south of Vatnajökull or other inhabited areas. What do you guys figure is the odds of this?

    • There are seismographs just everywhere in Iceland. 🙂
      (perhaps with the exception of the western end of Snaefellsnes peninsula …)

      • Sorry Inge, I was not clear. My question is rather if this has happened many times before all those nice seismographs have been installed.

  8. Can someone please explain their thoughts on the relation to the dyke swarm and Bardarbunga caldera? @subglaical on twitter explained the depressing of a cafetiere plunger to explain the caldera lowering. IMHO I would say that as the swarm progresses along the dyke and the movement of the magma, this creates a low pressure point at the dyke-caldera junction. The lower pressure is causing the magma to be sucked/siphoned from out of the Bardarbunga magma chamber, which is causing the noted deflation and quakes around the caldera rim.
    OR is it that the swarm punched a hole “pulled out the bath plug” out of the bottom of the magma chamber. And gravity just squeezed out the bottom into the dyke?

    Could someone also explain, as the swarm changes direction along the dyke, why there are little or no EQs where the swarm changes direction, why is this?

    • The lowest pressure point is the top of the volcano/caltera and just below that is the area of relative higher pressure that supports the very top layers of the caldera, so as the magma chamber empties this lower pressure area may well be kilometers above the areas of higher pressure dike intrusion

    • It may just be that the magma has scoured the passageway clean so is moving freely through there now; no pressure on the rocks any more. The magma reminds me of the huge bores used to make underground tunnels – there’s a lot of noise and pressure on the surrounding rocks where the bore is working but smooth and quiet where the bore has been.

      Unlike the bore in this short film, however, magma doesn’t reinforce the walls behind it!

    • My meaning of over is that this event seems to be an isolated introduction of magma under Bardarbunga rather than an opening up of a rift in direct contact with the core of the earth leading to a very extended eruption

      • Indeedy! Or to put it like our American cousins – “You ain’t seen nothing yet”. The fat lady hasn’t even cleared her throat yet.

        • Translation of the Icelandic Rúv-text (the “cardboard-text):
          http://www.ruv.is/frett/kvikuinnskotid-nalgast-sprungukerfi-oskju

          Kvikuinnskotið nálgast sprungukerfi Öskju
          Rúv,25.08.2014 09:44

          The intrusion is approaching the fissure system of Askja (volcano)

          There were about 450 earthquakes during the night near Bárðarbunga and Dyngjujökull , many of them over 3. Though the earthquakes activity is less than yesterday, it is still at a very high level and has been showing ups and downs during the night and the morning hours.

          „Around midnight the activity lessened at bit compared to yesterday when it was at a very high level. But it accelerated its pace again between (not after, I think) 2:00 and 5:00. After 5:00 it lessened again. The earthquake activity comes in high activity phases which can hold on for some hours and wane in between,” says Gunnar B.Guðmundsson, geologist with the department of risk mitigation at IMO.
          Most of the quakes take place a bit north of the glacier terminus of Dyngjujökull, initiated by the dyke which has been forming there. “Almost all of the quakes tonight were to the north of the northern terminus of Dyngjujökull, where the dyke intrusion is progressing northwards. It has taken a small step to the north and is now arrived at (a distance of) 5 km from the northern terminus of Dyngjujökull and into the fissure swarm which is part of Askja (volcanic system),” says Gunnar. “Up to 10 quakes were over 3 , and the biggest ones over 3,5 and they all had their origin within the Dyngjujökull dike intrusion.”
          The quakes are still at a depth of 5-10 km and there is no sign of a HT typical for eruptions. When he was asked about the meaning re. possible eruptions that he dyke which had its origin in magma entering a fissure deep within the crust under Dyngjujökull was now within the Askja fissure swarm, the answer of Gunnar was, that it would be very interesting for geologists to follow these events. “There is said to have been a eruption there in 1797 when the so-called Holuhraun (lava field) was formed. This is now actually following the fissure there and arrived in this region. Perhaps will it be like some geologists think that there was a possibility that the eruption would take place at the same location. But there is still no sign which would indicate that the magma is on its way to the surface,” says Gunnar.

          (my translation, no guarantees)

          And a more actual English RÚV version re. the quake situation:
          http://www.ruv.is/frett/over-700-earthquakes-in-12-hours

      • The GPS stations at Dyngjuhals and Kverkfjöll are still pulling apart at neckbreak speed as of this morning.

        Serge

  9. This is from Iceland Met
    25th August 2014 08:15 – from geoscientist on duty

    At 07:30 UTC about 500 events have been automatically detected. Most of them were
    along the northern tip of the propagating dyke intrusion northeast of Bardarbunga volcano
    at about 5 km segment outside the northern margin of the outlet glacier Dyngjujokull.

    At the northernmost segment of the dyke 9 earthquakes were larger than M3 and 3 of them about M3,5. The earthquakes depths are still below 5 km (mostly around 10 km).

    No large event were detected at the Bardarbunga caldera since midnight.

    There is no sign of volcanic (harmonic) tremor.

  10. I assume that the ” There is no sign of volcanic (harmonic) tremor.” is a tremor that indicates eruption under way as harmonic tremor of movement of magma is clearly visible.
    Can some one clarify this statements meaning

      • No, i questioned the meaning, i am not an expert in any way on volcanos, i just have a keen interest in them.
        I made an assumption as from the little knowledge that i have picked up from here (little from what some on here have) its what i thought it it could mean.
        I am certainly unable to clarify what the duty Geologist meant.

      • Ok, harmonic tremor is associated with fluids moving under high pressure such as magma. It’s exact origins and generation are not completely understood. The below examples from the USGS show four different types of tremor:

        Note that the time scale is rather drawn out. We do not have access to any seismic recording devices with such high temporal resolution, which the IMO scientists do. Therefore, we cannot detect the presence or absence of harmonic tremor with any degree of certainty or probability but have to rely on their bulletins.

        On Saturday, the detection of harmonic tremor indicated that magma was moving in the conduits. As I understand it , harmonic tremor always precedes an eruption and is an almost certain indicator that an eruption may be imminent. This is why the IMO scientists declared a red alert for Bardarbunga. With its absence, an eruption is no longer imminent and is why the Alert level was lowered to orange.

        Now, as well as dying down, harmonic tremor can stop and start again several times before an eruption occurs. The absence of detectable harmonic tremor at present should serve as an indication that an eruption is no longer imminent, but that can change very quickly.

    • Volcanic quakes generally have their own seismic signatures – and do behave a bit differently. One of the things to look for are pure frequencies – the harmonic part – integer multiples of the fundamental frequency. The fundamental frequency is approximately proportional to the chamber size. By looking at things like the change in time of the fundamental frequency (gliding) other inferences can also be made. As usual though these indicators are not always there but when present can give a reasonable indication of what is going on.

      One very simple way to think of it is like the harmonics generated by blowing over the top of a bottle. The sound changes depending on the size and if it is open or closed – as in musical instruments.

      • I remember watching a documentary about the discovery of harmonic tremor before an eruption that used those huge church organ pipes as an example when they were explaining it

        • Hi Bev! Would be great if you could remember or even locate that as I’m sure there are many people here who would be interested in that explanation.

          PS. Been for “Walkies!!!” yet? 🙂

        • Happened during Redoubt….. guy from Argentina? called the Redoubt guys up and said “i think You are having a volcano” … 😉 reading the story is neat. Best!motsfo

  11. Activity has slowed down but still there shaking the area.

    The dyke/intrusion is now traveling N-NE towards the Askja, so Still continuing but much far away now from Barbardunga, so it makes sense the “echoes” are not shaking it s caldera that easy.
    From my point of view in next hours/days activity will remain as fracture keeps opening towards Askja.
    If Askja gets lava into the caldera a nice boom will be seen 🙂

    Thanks for the site!!!

    • I think that when the dyke reaches Askja’s magmachamber which contains highly evolved magma, Askja will have a VEI 6 Pinatube-style eruption. That would be very exeptional, basaltic rifting fissure eruptions together with a rhyolithic Pinatubo-like central volcano eruption.

      • Ah! Askjatubo.

        Probably not very likely as Askja had a major (VEI 5) eruption only some 140 years ago, on March 29, 1875. It will not have had enough time to cook up enough new dacitic-rhyolitic magma for another such large eruption yet. Furthermore, it is highly unlikely that the magma chamber is large enough to contain sufficient eruptible magma for a VEI 6 especially as the last major eruption resulted in a partial collapse of the magma chamber.

  12. Ok, having now done my homework and studies ‘How to read strain and seismicity…’ I went to take a look at the tremor measurements on IMO. It does look like many are showing an increase in 2.0-4.0Hz readings over the last 24 hours. Interesting. Thanks for link to article which was really clear to read and understand

  13. Don’t know about Bardy/Askja but activity in here sure has dropped this morning.

    I wonder if there is a relationship between numbers of posts here and numbers of earthquakes in Iceland?

    • More likely a correlation between number of posts and the number of those at work today. There were a great many people here over the weekend – I noted the build-up in numbers from Friday evening – but they weren’t here just because there was more earthquake activity but because it was the start of the weekend and they had the time to log in and stay a while.

      • See posts below Mopshell. I was just being flippant anyway 🙂 In truth the dyke is still rocking and rolling just not quite so loudly this morning. This has some way to run and it’s back to work for me tomorrow too 😦 so no doubt site traffic will drop some more.

    • Sadly, I know and the weather is typical for a UK August Bank Holiday! Rain hasn’t started here yet in earnest (spits and spots) but down south doesn’t look to clever.

      I do remember reading a post on here some time ago about visitors to the site and most were from the UK so I think you are onto something, especially as our friends across the pond are only just getting out of bed.

      • Rain been pouring down in the South Coast of England since very early morning. No washing for me just washing up and cleaning the cooker after husband decided to make brownies. Oh that man is messy!
        But he does make exceedingly good cakes!

      • That was my excuse – whereas being at work would not necessarily curtail my online activities, being a Bank Holiday we have been out to buy lots of Thomas The Tank Engine stuff. I do spoil my grandson rotten, although my wife reckons that the toys are really for me.

  14. @carl is it possible that the intrusion could miss the Askja chamber, turn and join up with activity that had been ongoing in the Herðubreið area?

      • This has been mentioned previously over the last couple of days. I don’t have a Scooby doo but at this point all bets are off. No-one really knows what’s going to happen, it’s just a case of watching and waiting. This ground-breaking (no pun intended) stuff we are being treated to in Iceland at the moment and I for one am loving it!

    • There are a lot more tectonic fissures in that area than the region between the eq activity and Askja.
      (Although it may be that in some areas fissures are not detectable by eye.)

      • Jonfr wrote on his site back in March 2013 that there had been some deep eq under askja and linked this to the lack of ice. Am I seeing links that really are not there? I do tend to invent ‘facts ‘ to fit situation and not the other way round. Also keep fit by jumping to conclusions!

  15. Not sure what you mean by “calming down” and “It´s over”.. Looking at the EQ in total so far today (since midnight) the total number of tremors are 581. 340 of those has a quality higher than 90% and 112 has a quality of 99%.

    This is far above any normal day and to say “its over” seems a tad early to say..

    Also looking at a previous post demonstrating the cycles of the ongoing activity I would not be at all surprised if it picks up again soon.

    I know that humans tend to look at patterns in almost everything they see and this is no exception. Looking at the tremor chart for DYN it does seem to be on its way back up.. Just ever so slightly but still an small upward trend.

    • I’ve been watching the total # of Vatnajokull quakes over the previous 48 hours. 1966 when I started looking a couple of days ago, 2300 last night, 2486 as of now. This figure doesn’t tell us anything about size (no 3+ quakes since 7.20 GMT – 4.3 hrs ago), depth or direction, but the total quake # is still increasing as of now.

    • And once the more normal tremor moves of the screen and leaves only the higher tremor they will forget what they are really looking at, unprecedented levels of tremor most of the time.

    • I still think there is a 50/50 changes that it stalls and erupts there, just like in 1700s, or that it travels further north and erupts at Askja. Or perhaps more changes of stalling and erupting at the current spot.

  16. More dust storms on the webcam this morning. Looks quite windy too. At least we now know the webcam is pointing to exactly the right place should anything surface.

    • That is just because its magma came from a Bardarbunga lateral dike intrusion, just like we are seeing now.

      I would be curious to see whether in 1874-1875, some magma in Askja was also derived from Bardarbunga.

      • That paper indicates no mixing.
        The Holuhraun eruption looks, to me, to be the closest resemblance we have to the current activity.

        That paper is recent. Traditionally Holuhraun has been asocaite with Askja. But the petrology suggests its from Bardabunga. So I question whether the activity has entered Aska’s fissure field.

        • Also are the authors of this (very interesting – as far as I understood it, just skipped the geochemical details) paper, talking about magma reservoirs rather deep down, near the bottom of the crust. Couldn’t these be also the feeding mechanism in our case? So that there would no mantle magma have to be involved?

          • And Peter, do you then think, that the reason why there are now no more heavy earthquakes in this region whould perhaps be, because this magma has found the existing feeder system of Holuhraun lava exactly from Bárdabunga?

        • Seing the pictures I would not want ot get caught in such a phenomenon. It is lava dust, so very very abrasive. I think you would need googles, gloves and probably some dust mask and a way to protect your faces’ skin.

  17. can someone with knowledge update us on MOST LIKELY happenings now.
    Does the lower harmonics and less intense quakes indicate.
    1 Less magma moving in from deep
    2 less restriction on it moving but same amour flowing through. Ie it found old dykes and so pressure released as it flows to fill that void and so not having to burst through rock etc.
    3. neither and something else.

    I understand a definitive answer can be very difficult. However thoughts and explanation would be very good.

    What seems like a slightly quieter period could infact be the calm before the storm, as if 2. is correct the magma could move very quickly to Askja and possibly mix with volcanic matter there. Some say this could be a spectacular mixture if it happened.
    So would be good if one of the regulars could give their thoughts.

    • See mt reply blow. Sometimes intrusions stall and no eruption happens. Example of Hengill rifting episode in 1789 or Theistarreyk rifting in 1618. The tectonic fissures opened but magma only intruded did not erupted.

      I think here it might intrude, and stay like that for a few months or years until it erupts. So don’t get excited yet.

    • What plot are you looking at floodwarn? I cant see it on the one I am watching. Perhaps yours is faster loading.

      • DOH *slaps forehead* :0

        I was looking for it after 12:00 when obviously it would be before. Sorry about that.

      • Another newbie here. No good reason to follow you all except for wow factor ;-).
        I can’t see this stronger earthquake either so was wondering the same…

        • I think it may depend on which of the drum plots you look at. Some show it more than others, I think according to which one it was closest too. I personally watch the ASK and DYN ones as I think they are closest to most of the quakes. Others are good for reference too of course.

  18. Gorgeous sunshine and horizon to horizon blue sky here today in the NW of Scotland. Doesn’t look as though it is likely to be spoiled by any ash today.

  19. If you go to this site it shows the progression of quakes over the last 15 days

    http://www.ijsland-enzo.nl/ijsland/actueel_aardbeving_5dgn.asp

    Zooming in on the leading edge of the fracture you can see when it stalled a few days ago there is a small swarm, maybe 4-5km in front of the leading edge, that quickly works backward to join the leading edge and then the edge moves north again

    This happens again as the edge approaches the end of the ice and stalls. there is a swarm 2-3km in front that tears backwards and the edge move quickly north

    Will be interesting to see if it happens again during this stall

    • Cool stuff, thx! I was looking for a timelapse of the quakes. You are right, it does look like it’s punching a hole in front and then completing the “trench”…

  20. todays update up to 9 h35 AM IMO time

    The swarm seems to have progressed less, but the progression is not stopped. There is some accumulation in the “older” zone. Quake quality >99%, datafrom IMO, NOAA, made on Gnu Octave

  21. Last one shows up well at IHAE: http://hraun.vedur.is/ja/drumplot/IHAE.png

    I edited your comment so that the link still shows, but no image. It is generally a good idea to post screenshots uploaded to an image service like tinypic, imgur etc. There are two reasons: first, the traffic on VC will not automatically affect hraun.vedur.is, secondly, the image probably updates so comment and picure might not match anymore tomorrow. Thanks for your kind consideration. 🙂 chryphia

  22. After such strong quake activity i think it is likely that even if the dyke totally stopped progressing right now the quakes would continue for days to come

  23. My weird statistical guesses:

    60% of changes that magma stalls in this intrusion and then 3 things can happen: either does not erupt (20%), or erupts there (40%). If it erupts it can either form a fissure (25%) or a single-spot eruption (15%). I still think we will see the intrusion eventually stalling before reaching Askja.

    30% of changes that it travels further north and then either, erupts at Askja (20%), or a slight change that it does not trigger an eruption there and continues northwards and loses pressure and the intrusion eventually dies down (10%).

    10% of change that the intrusion travels slightly east into Herdubreid system and might trigger an eruption there (5%) or not (5%). But I think it is more likely if it continues northwards and it reaches Askja rather than Herdubreid.

    Thus 65% changes of eruption (40% of where it currently, 20% at Askja, 5% at Herdubreid).
    35% of not erupting (20% it dies down at current place, 10% it dies down around Askja further north, or 5% dies down around Herdubreid region).

    • Hm…

      Even if the total amount injected by now exceeds 0.3 cu km (300 million cubic metres), it is spread out over something like 30 km which gives a figure of about 10,000 cu metres per metre of trench. Not a very big eruption even if the Bardarbunga magma system should have drained of a similar amount.

      • This is only if we’re assuming the mantle doesn’t get involved. Keep in mind, the majority of the magma from the skaftar fires eruptions had little to do with the actual amount of magma intruded.So in other words, this is not a huge eruption *if* the mantle doesn’t get involved during an eruption. That’s a very very very important if in this scenario.

        • Exactly!

          Now, we know that the intrusion is at about 5 – 10 km depth and that the crust along these rift lines it’s following is 25 km or so. With 10,000 m3 per m length, that leaves us with no more than a 40 cm wide crack from top to bottom.

          Somehow, there’s not enough magma in the system to cause a rift eruption. 😉

    • Irpsit, good morning from Brazil! As I already told you guys before, volcanology is a completely new subject to me, so, I just wanted to make a humble question: between your statistical guesses, which are the worst consequences? Sorry to bring back again this question, but do you think there is any possibility to having UK’s airspace closed? Thanks so much.

      • The forecast for the coming week – up until Friday – is for wind coming from the south-west. This should keep any winds from Iceland well to the north of UK and Europe. Hope this helps.

  24. On page 2 a beautifil picture showing how a lateral dike works (A) , and later when mantle deompression works (B). Sometimes there could be years or decades between A and B. Please remember this.

  25. It looks to me we now have a lot more 3+EQs that has been added on vedur. 16EQs 3+ since midnight in total. Maybe I missed it before or they have only checked and added them?

  26. And with the amazing paper I just read above I learnt the following:

    Year 1862-1864: for these two years an eruption happened in part of the Veidivotn fissure AND Dyngjujokull at the same time! Both came from Bardarbunga central volcano.
    Year 1873: a large eruption of Grimsvotn, similar to 2011
    Year 1874: an eruption starts at Askja caldera and possibly a fissure extending southwards of Askja into Vatnajokull glacier, belonging either to Askja or to Bardarbunga. Reports of two 20km apart ash plumes are still unlocated.
    Year 1875: a large fissure forms near Myvatn, formed by a very long dike north of Askja, and then Askja also goes caldera at same time.
    Yer 1902/1910: possible eruptions again in Dyngjujokull, Bardarbunga central volcano and Loki-Fogrufjoll., just slightly north of Laki.

    Amazing how much rifting activity the region had within a few years!

  27. Hi! Thought I would return to the riddles while we wait. Feeling too lazy to check past answers so apologies up front 🙂

    #3, Soufrière Hills?

  28. Iceland Laki forgotten Volcano 1783 this could happend again this time.
    Allot forgot the Killer Cloud Laki, and cost allot of lives.
    Watch full version KILLER CLOUD LAKI.

  29. I found this site really interesting.

    http://www.ijsland-enzo.nl/ijsland/actueel_aardbeving.asp

    The quakes are dropping down in time sequence and when watching it zoomed to just below maximum zoom in it appears that many of the small quakes are propagating laterally from the larger size 2 quakes.
    I am wondering if this signifies that the magma is held up ahead and trying hard to find a different way out.
    Any ideas from more expert contributors on this?

    • Just for fun: looking at the behavior in the last 2-3 days and the current relative stall, I would bet the dyke is changing direction towards East of Askja (NE) when it resumes its advance…

        • I understand your point and it may be correct. However, it did change direction a couple of time after a brief period of relative stalling (like today), there were a few eq’s on the path it eventually went (look towards the direction I mentioned) and it doesn’t need to be a radical change in direction, it would still go on a general NE direction. Plus, I took into consideration what was said a few times here, that the pressure in Askja system may block the advance of the intrusion coming from Bardarbunga. If so, it could only go left or right (or stop, or…) 🙂 I bet on right. As I said, just for fun, lets see 🙂

  30. Hi Carl , diana, geo’s , irpsit et al

    Wow carl et al youve been busy, awesome work papers you ve done. Enjoying catching up and looking forward to the day s ahead.

    • I take FULL credit for that! That was when my computer crashed! When I watch football my husband’s team loses, when I don’t watch they win. Same with quakes. Expect them to stop again now. 😉

      He couldn’t find the fault so cured the problem with his usual trick. Take out the RAM blow off any dust with compressed air and then replace. He reckons it works every time. Hope so! I can’t lose this now! Wail!

      • hehe reminds me of Nintendo cartridge blowing xD.

        but yeah not sure if you also have a dedicated graphics card in there but cleaning that on out and the CPU cooler would definitely also help if problems are heat related.

  31. Flavia, please remeber that no-one here knows at all what will happen, with volcanoes often no one knows until it happens. We have been surprised before. All that you will find here is conversation about geologic processes, following of events as they occur, and continuing attempts at self-education from all of us, even those who have some professional familiarity with volcanism. No one has predicted, only specualated, and no one can correctly predict at this time. The Icelandic Met Office will be the only ones to follow for that, and no one at all has issued any travel warnings (ecept, briefly, for airlines to stay away from certain air routes, and that is now canceled.) I understand how frustrating that can be when your plans are possibly affected. This site is only a place for learning and discussion, and sometimes people who post here like to ask what can be the worst thing possible, which does not mean that anything like that is about to happen…
    Any future Icelandic Met Office warnings will of course be posted here. I hope personally that you have a wonderful vacation. Perhaps Renato Rio can answer you in your language? Or, use Google translate even though it is sometimes peculiar.

    • Granite1, thanks for your response. I totally understand what you wrote. Don’t worry! 🙂 Thanks a lot for your attention. I’ll keep my fingers crossed. Regards.

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