Gunung Egon heading towards an eruption

The narrow crater of Gunung Egon from the air.

The narrow crater of Gunung Egon from the air.

According to local news and reports from the BPBD in Indonesia evacuation is taking place of three villages close to the volcano. So far 1 200 people have been evacuated using military trucks. Furthermore 2 000 masks have been distributed to those who are waiting to be evacuated to help protect them against the heavy sulphur fumes.

The alert level has been raised to the highest on a four grade scale and local authorities are waiting for new instructions from the PVMBG in regards of more widespread evacuation around the volcano. The current recommendation from the PVMBG is that all of the population should be evacuated in a zone 3 kilometers from the crater.

The level of unrest has increased during the last month forcing the PVMBG to raise the alert level twice from level 2. Level four means that an eruption is imminent, or that eruption has started.

Gunung Egon

The inside of the crater after the 2008 eruption. Notice fumarolic activity and the lack of a crater lake.


The volcano is situated on a narrow isthmus on the island of Flores. The volcano is not one of the more visually impressive and is only 1 703 meters high.

Before eruptive behavior started on the 29th of January in 2004 it is believed that the volcano had been dormant during recorded history. Even if there have been reports of previous eruptions it is now believed that it was just vigorous fumarolic activity in the crater and that no true eruptions have occurred.

Between 2004 and 2008 four minor eruptions have occurred ranging from VEI-1 to VEI-2.

After reading through the weekly bulletins on the Global Volcanism Program website it seems a bit unclear if the reported eruptions was caused by lava emission or if they where instead phreatic detonations. If it was phreatic detonations it is likely that it was caused by intrusion of fresh magma from depth and that this was onset of a “throat clearing” phase of the volcanic system and that a larger eruption could follow with time.

Photograph from Global Volcanism Program website. Note the high rate of fumarolic activity and the crater lake.


It is therefore hard to predict what will happen now. It could be yet another bout of phreatic detonations, or a full scale eruption could take place. There is also little or no historic record of how this volcano behaves during a full eruption, at least in the English language.

Request for links

Volcanocafé has always been a great source for links and information prior to and during eruptions. We therefore kindly ask for links to webcameras, seismometers, gps-stations and to scientific papers on the volcano. All news would also be highly appreciated.

All pertinent links and news will be collected and added to this article.


179 thoughts on “Gunung Egon heading towards an eruption

  1. The PVMBG are a highly professional bunch; they aren’t going to issue a Level 4 warning with evacuations without having a VERY good reason.

    • They are probably the best on the planet, or at least among the top 3 together with IMO and the Etna bunch.
      I would though place Surono on the top of the heap.

  2. Have a friend who has a daughter that works on some sort of mission’relief group on Flores, he is in constant communication
    with the org. and his daughter I will let you know if I hear anything..

  3. I made this image to denote something mildly interesting in Indonesia. That being the fact that east of Flores island, where Egon sits, the subduction is different than in the rest of Indonesia in that the Australian continental mass is actually what is subducting into the Sunda trench as opposed to oceanic crust. This results in a different chemical composition of the magma in volcanoes in this region.

    • There could be that, but my tagalog is not good enough to search for it.
      If one of our Indonesian friends could search and translate any papers it would be welcome.

      So Mike, are you heading out?

        • *Facepalm*
          Nope, they are not. Bahasa Indonesia would be the language of choice.
          Mea culpa and soforth…

        • MABUHAY!

          (No, neither am I. My linguistic abilities are pretty much at the gesticulating stage. Though if you have a bit of Spanish under your belt, you can occasionally work out the signage.) Just be careful at 3 am while trying to get chicken on a stick, you could wind up with balut instead. And if you are not drunk enough, you might hurl… well, you might hurl anyway. I was drunk enough that it tasted like crab boil. Scotch and San Miguel can do that for you. No, I wasn’t out wandering the streets. (not quite that stupid), I was holed up in an apartment trying to figure out the meaning of life.

      • The problem with the eruptions described at the GVP is that if you read the weekly bulletins it seems more like phreatic detonations than real eruptions. There is also no evidence of fresh material on any of the pictures.
        Also, the eruption prior to those was very vague in the description. At best I would say that was another phreatic episode.

        I do not think there has been any juvenile material so far. And so far I have not found any evidence of it and I have looked hard for petrographic data before writing the article.

        • GVP include in their background info that the southern summit is a lava dome. Can’t see from a quick skim over their stuff whether there has been any recent eruptive activity from the lava dome, itself.

          Their references may give more information.

  4. So there really is basically no literature out there about this volcano. I searched multiple sources, tried looking for more generic information on Flores island geology / volcanology, and still nothing to be found.

    Reason being: Any level 4 alert for a volcano that hasn’t had a magmatic eruption in known history is worth paying attention, especially in Indonesia.

    From what I can see and from what I’ve read, Flores island is littered with volcanic remnants, active stratovolcanos and calderas, but that doesn’t really mean a lot considering that’s about par for the course in Indonesia. Even the larger sized calderas are poorly understood beyond extremely basic knowledge that they exist on the island (Lobobutu caldera, Sukaria Caldera).

    There is also a relevant question of whether Egon is a somma. There is a somewhat suspicious ridge to the east of the central vent that makes you wonder if it was formerly a part of an ancestral cone, but that’s nothing more than speculation (could simply be a product of erosion).

    One juicy tidbit about this island (Flores) is that in the ancient past, a unique race of pygmy humans lived here (around 18,000 years ago I believe). There are references to finding fossils and such of ancient species trapped within ignimbrite deposits on Flores island – the volume of said deposits or source is unknown however.

    • Pygmy? I do know that Homo floresiensis was of the right size to where Komodo Dragons would have literally seemed to be the size of dragons from folklore. No matter what your size, they are still quite lethal.

      “Local geology suggests that a volcanic eruption on Flores approximately 12,000 years ago was responsible for the demise of H. floresiensis, along with other local fauna”

      The discovery of the remains of a meter-tall hominid on Flores Homo floresiensis, alive at least as recently as 13,000 years ago, has inspired more literal interpretations of the Ebu Gogo stories. Anthropologist Gregory Forth, Professor of Anthropology at the University of Alberta, Canada has stated that “wildman” myths are prevalent in Southeast Asia and has investigated their linguistic and ritual roots, speculating that H. floresiensis may be evidence that the folktales of Ebu Gogo and similar creatures such as the Orang Pendek on Sumatra may be rooted in fact.

      • Flores is an interesting island for many reasons. We flew from Bali to Ende which is west of G.Egon. We visited the volcanic complex east of Ende where three volcano cones reside in Kelimutu. Each lake has a different color due to different dissolved minerals. There is quite a bit mythology associate with these beautiful volcanic lakes and different types of personalities are associated with these mystical lakes. A number of people has slipped and fallen into the lakes and when we were there safety was not too serious. The blue lake is extremely acidic much like Kawah Ijen in east Java. Even your bones would dissolve if you were unfortunate enough to fall into the lake

        The flight to Ende was on an aircraft where big patches of damaged plastic on exit doors were repaired with duct tape. It started to rain inside the aircraft on takeoff because outside, very moist air, was mixed with cold interior air. I believe that Indonesian aircraft are not allowed to land in parts of the EU because of an abysmal safety record. Anyway it was an unbelievabley beautiful flight since the air was clear and one could see volcanoes and jungle covered slopes.

        We left Ende by local bus (pigs on top of bus and some cages of chickens inside). lol Shortly after leaving Ende we saw obvious alcohol stills in back yards. They were almost certainly distilling Arak a very strong alcohol almost guaranteed to make you sick if you have very much.

        Arrack (arak) is often created as a form of moonshine in Indonesia. Indonesia has the largest Islamic population in the world. However Flores has mostly Christian people in the center and small mainly Muslim fishing villages along the perimeter. The bus ride down the middle of Flores is fantastic with steep jungled slopes. Occasionally one would see groups of tree ferns. Apparently plant fossils are sometimes found in coal mines with identical characteristics to the modern living plants.

        One of the highlights for the trip to Flores was to visit Liang Bua Cave which was partially excavated a year or two earlier yielding numerous bones of Homo floresiensis, the “hobbit”. I met a bunch of young people who were training to work in tourism. One very pleasant young man said he would take me to Liang Bua on his scooter which is not far from Ruteng. It was thrilling to see this small major archaeological site.

        At the west end of Flores, we traveled by boat for three days in the direction of Bali. We did stop and see the Komoto dragons on Komoto Island but if you want to really see these beasts you need to visit Rinca Island. They are truly fearsome creatures often obtaining 3 m long. They lie in wait for buffalo who are present through out the island and are dangerous enough by themselves. The Komotos have long, yellow-orange forked tongues and will be seen with slivers of flesh and skin hanging from their mouths. Also, they have established that the dragons do in fact have some kind of venom. They will bite a prey such as a buffalo and wait for them to die. Real deja vue Jurassic Park kind of feeling. Several people had been killed by the dragons prior to out visit. The rangers assigned a ranger to travel with you the several km dirt trail to the center of the Island however the only protection he carried was a long stick with a small Y on the end. Didn’t see what good that would do. Oh well.

        Thanks Carl for the update on G.Egon and the crew who keep improving the site.

        • It’s good to be back – and thank you for sharing that interesting comment, Biologique. I know that such tree fern fossils have been found in the South Wales coal fields which were formed by the Caledonian collision, when the forests were submerged, and which went extinct at the end of the Permian era. Flores and that part of Indonesia must have been part of the 10% part of the planet which didn’t have an extinction at that time. The land that time forgot.

  5. I don’t believe the alert is at the highest level. According to their website and accounts, it’s only level 3 of 4. Still quite high obviously, but not the highest.


    This morning, we are going to be moving the blog over to a temporary URL whilst we move the Domain to the new home.

    As part of this process and to ensure we don’t lose any comments, I’ll be taking the comment function offline for a short time at some point this morning. We expect it take no more that an hour or two at most.

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    • Thank you for all your hard work now and in the future and for this notice. Best wishes XXXXXX

    • A response made on an “Ask the Expert” site without citations, though worth a second look, isn’t exactly reliable, especially from a professor who is writing a bit outside of her specialty. There was most likely confusion at some point with the 1932 eruption at Lewotobi.

      • There are many volcanoes where there are confusions about eruptions prior to the “modern” age.
        Egon is one of those. Problem is just that these questionable eruptions tend to hang around until they are finally dismissed.
        Remember that volcanology is a rather young science with a lot of house cleaning to do.

    Not sure if all pictures are from Egon…
    Egon kembali aktif pada 2006 setelah vakum selama 75 tahun. Egon tercatat meletus dahsyat pada 1925.
    Egon active again in 2006 after a vacuum for 75 years . Egon erupted explosively recorded in 1925 .

  8. Part one of the move has been accomplished. Part two will take place somewhere over the weekend.

  9. Report on the activity of egon dd 13/01/16 with graphics.

    Translation of conclusions in this report:


    Visually, no visible change in the color and height of the smoke solfatara G. Egon volcano closed due to fog. However, thin white smoke were still visible as high as 25 meters is still generated by the energy in the body G. Egon tend to fluctuate.

    Egon G. seismicity is still dominated by volcanic earthquake tremor In (VA), Harmonic Tremor earthquake, and the earthquake Blowing. After a rise in the level of activity on December 15, 2015, the number of seismic G. Egon entirely tend to decrease and increase. But on this day RSAM chart shows considerable increase in activity sigifikan after the earthquake felt at 09:36:08 pm.

    In general, the type of eruption of Mount Egon is phreatic. This type of eruption can occur if the interaction between the vapor (steam) magma with water below the surface (hydrothermal) which resulted in changes in the liquid phase to a vapor, produces changes in volume (decompression) that can push the rock cover (plug) near the surface of the crater. Symptoms observed at this time is identical to symptoms of increased seismicity before the eruption of Mount Egon 15 April 2008 which lasted a relatively short. While it can not be ascertained the eruption of Mount Egon, but anticipatory efforts and disaster mitigation efforts need to be improved.”

    translation Google Translate

  10. Seems to be in order now.
    I guess that I was among the last to get back the comments.

    • Yeah, but the back channel conversation is definitely spooky. No more ghost tales for me.

      I also hope that my response is not one of those pseudo-psychic things that I unintentionally state. By stating this, I lessen the chance of it being one. This way, if whatever happens, anyone can come back and say “See? That’s not what he was saying!”

      Caveat: Not a Medium, not even a Well done. Just slightly charred. {I guess that would make me a Rare}

      • You are to date the closest I have come to a psychic. Not intentionally or anything like that. I think that it is your inordinate capacity to figure stuff out that make you sometime figure out things slightly before they should be able to figure out. Ie, Being rare! 🙂

  11. Ever so slightly volcano related rumination…

    I live in a city called Gothenburg. It lies in the southern part of Sweden.
    Last couple of weeks there has been a cold snap and this night there came 30 centimeters of snow.
    In the morning I looked out and noticed that everything was white, pulled on my shoes and went to work.
    In retrospect I could as well have taken the day off. Out of 150 people only 3 came to work.
    Here it is now known as “The Snow Catastrophy of the Millenium”, for me who is from the far north I called it a normal tuesday in winter.

    This got me thinking about volcanoes and being used to them. In Gothenburg there is no abundance of snow clearing machines and people do not even have proper winter shoes.
    Same goes for areas that are not used to volcanic eruptions. No equipment, no knowledge about what to do.
    In a volcanic sense it was like I was from Indonesia, being used to waking up to ash and eruptions. I just got on with life trusting my knowledge and equipment whilst someone from a less eruption frequent country would have gone nuts.

    Knowledge and a simple bit of equipment (shoes, gloves and a snow cap) got me to work without a hitch (had to walk for 30 minutes). Now, compare this to the eruption of Kelud in Indonesia. It was the second largest eruption of the millenium so far. It was brilliantly prognosticated and mitigated even though there was a lot of residents close by. Heavy equipment moved in to clear the roads hours after the eruption ended. Only two people died due to roofs caving in. Due to knowledge from the professionals, authorities and the locals a potent eruption became a nuisance instead of a catastrophy.

    Ponder it for a while.

    • It always strikes me as funny how people in Sweden fail to realize that each year there is this period called “winter”. Winter usually brings cold days and snow even in the southern parts of Sweden. Often, it melts away quite fast, but it almost always makes a short appearance, at least for a few days every year. Even further up north, where winter stays for a couple of months, people are taken by surprise each year as the first snow falls. Yes, winter happened. This year again…

      Earlier this winter, I was very amused by the Swedish met office, SMHI, when they issued a class 1 weather warning for the Stockholm area – they were expecting 5 centimeters of snow, in the end of December!!! Class 1 is the lowest on a scale from 1 to 3 and means that some disturbances in public services can be expected and there is a possible danger to the public. Well, with people waiting until the first snow before switching to winter tires, maybe that warning was actually called for.

      Now 30 centimeters on a single day IS quite a lot of snow, even if it falls in the northern parts of Sweden, but I’ll agree that it is more of a nuisance than a catastrophe.

  12. A small possible intrusion going on in the Bárdarbunga system. Starting at depth and moving upwards. No clear magmatic signals.

    19.01.2016 19:49:29 64.671 -17.477 1.6 km 1.3 99.0 4.2 km NE of Bárðarbunga
    19.01.2016 19:29:22 64.677 -17.486 2.0 km 1.2 99.0 4.5 km NNE of Bárðarbunga
    19.01.2016 19:15:22 64.665 -17.501 3.4 km 1.5 99.0 3.0 km NNE of Bárðarbunga
    19.01.2016 19:12:41 64.617 -17.178 9.6 km 0.6 99.0 16.9 km E of Bárðarbunga


      • I think you mixed up the volcanoes Geyser…
        I was not talking about the cryptodome in Myrdalsjökul, I was talking about Bárdarbunga in Vatnajökull.

          • Precisely,have an open mind.The formation of a dome may explain some of the activity that never seem to make any sense with the 2014 Holuhraun event?

          • @GeyserSoze: What activity are you eluding to that made no sense?

            It simply wouldn’t make sense for there to be a current cryptodome growing in Bardarbunga. Cryptodomes form when magma can’t find an easy path to the surface, so the pressure forces it into the shallow crust, pushing up the ground below the intrusion. Considering the fact that magma clearly and easily found a way out of Bardarbunga, why would there be a cryptodome forming?

            I get the impression that you’re trying to frame circumstances to fit a narrative you already decided on.

            @TomasAnderrson: Both volcanoes *could*, and probably have had a cryptodome at some point. But in order for a cryptodome to form, you need specific circumstances that make it more likely. Those circumstances are not presently in effect for Bardarbunga.

            Think of it this way, if a champagne bottle had a large hole in the side of it, it’s pretty unlikely that it would push the cork out when you shake it up. The champagne would simply move through the easier pathway (the hole) to release pressure. The same is the case with Bardarbunga.

            Technically speaking, all volcanoes could be argued to start out as cryptodomes. Afterall, a cryptodome is simply an intrusion that hasn’t popped the surface yet. In the case of Katla, the intrusion is the Godabunga Cryptodome, which comes from an independent feeder system between Eyja and Katla. It is essentially a new volcano being created (although it’ll take some time and a lot more injections before its ready to break the surface).

          • cbus05 ,the crypto dome would been in long before the magma that caused the Holuhraun event came to the surface,some of that magma may have had an effect on the subsurface evolved viscous magma dome ,causing dome growth and seismic activity that was out proportion to the voluminous and freeflowing basalt eruption.I am putting forth an idea for discussion and if anyone can blow it out of the water as nonsense then all well and good.

          • My comment was just to point out what I thought Geyser was trying to say. I don’t really think there is a dome building. Personally, I think it’s the plug either settling or being pushed back up. It would be interesting to have beach balls to see the faulting mechanism.

          • regarding whether the radar would pick it up: it measured changes in the ice level during the eruption, to an accuracy of centimeters. A changing bulge underneath the ice should have been visible.

            I would agree that doming is always possible, but in this particular case seems less likely. I guess the main reason to discus sis the cluster of earthquakes during the 2014 eruption in one location. But I think this was due to drainage of a small magma layer, emptying into the hole caused by the dyke.

          • Albert,would not aerial radar penetrate the ice and show surface topography,not anything below the surface of the caldera floor or under its rim.Was there not a recent report that implied the subsidence was due mainly to flowing ice in the glacier and GPS measurements indicated inflation?There seems to an impression that a dome, would form with the low viscosity basalt and because of the eruption dyke that basalt is no longer present.I am suggesting that the theoretical dome would be most like evolved magma (rhyolite?)and been in place for decades and perhaps centuries and a large rifting surge of magma(some of which found an escape path via the dice to the surface) has energized this dome into a growth phase.

          • I think the radar measured the level of the ice surface, not the rock surface below. If you grow a dome, it will push out the ice too. It gives a bit of a ripple effect as it is pushed both upward and sideways. That pattern, I think, would have been seen. A quiescent dome would not show up, but a growing (or deflating) one should. Of course it would depend on the assumed growth rate.

        • Problem is just that Godabunga is not an intrusion from Katla.
          Anyway, this is just magma moving up the system, or settlement of the caldera again.

          • Not @Carl specifically, he just had a good spot to hook this comment on to.

            Radar mapping can penetrate ice, and with the right frequency, the ground to some extent. Can radar detect really deep stuff? Yes with interferometry. In that case, it’s doing detection of changes in ground deformation. By watching these changes, magma movement can be infered.

            I don’t know if IMO was using SAR, but they were definately watching the seismic signal and tracked the dike while it made its trek from bardabunga down to the grimsvotn fissure swarm where it turned north towards holuhraun.

    • I believe there have been a few of these episodes, of varying intensity, over the past couple of weeks

  13. Magnitude 3.6 at Bardarbunga.
    20.01.2016 13:05:48 64.670 -17.370 1.1 km 3.6 50.5 8.2 km ENE of Bárðarbunga

      • Wednesday
        20.01.2016 13:05:48 64.673 -17.456 0.7 km 3.6 99.0 5.0 km NE of Bárðarbunga

    • Swarm followed too
      Credit: Icelandic Met. (Meteorological) Office
      20.01.2016 13:45:40 64.676 -17.447 10.0 km 1.7 99.0 5.5 km NE of Bárðarbunga
      20.01.2016 13:22:07 64.704 -17.503 13.4 km 0.4 99.0 7.1 km N of Bárðarbunga
      20.01.2016 13:20:16 64.670 -17.425 9.0 km 1.6 99.0 5.9 km NE of Bárðarbunga
      20.01.2016 13:20:02 64.699 -17.523 11.7 km 0.7 99.0 6.5 km N of Bárðarbunga
      20.01.2016 13:17:30 64.670 -17.508 0.3 km 0.9 99.0 3.4 km NNE of Bárðarbunga
      20.01.2016 13:16:20 64.671 -17.512 3.6 km 1.2 99.0 3.5 km NNE of Bárðarbunga
      20.01.2016 13:15:35 64.643 -17.442 5.9 km 1.0 99.0 4.1 km E of Bárðarbunga
      20.01.2016 13:10:52 64.685 -17.427 7.3 km 0.5 99.0 6.9 km NE of Bárðarbunga
      20.01.2016 13:08:50 64.672 -17.490 6.6 km 1.4 99.0 4.0 km NNE of Bárðarbunga

  14. Both the tremor charts and the drumplots went offline just before the quake.

    • I would suggest that under the circumstances earthquakes like this will be an ongoing occurrence for years.It’s only a concern if it escalates to dozens of these quakes per day or a large quake at or >6 mag occurs nearby.

    • One thing to note here is the lack of any real tremor increase with the swarm of quakes, would you not see this on the drum? It is really “quiet” right now in Iceland so I would think it would show in the baseline if any sizeable amount of magma was moving?

  15. Here are some of my thoughts about the situation in Bardarbunga. The last 3.6 is not included in the analysis, since it happened after I have collected the data.

    At a quick glance, it may look like there is a lot of shallow activity going on at the Bardarbunga caldera. Now what’s that all about? Blocking? Cryptodome? I decided to have a look at the depth distribution of the released energy, both during the eruption and during the post eruption phase. To do this, I divided the depth into 1km segments and computed the accumulated seismic moment at each depth interval. I then translated that into the magnitude we would get if that seismic moment was released by a single quake. The result is as follows:

    Looks similar, right? Almost the same distribution, just a couple of orders of magnitude less intense. To be exact, the total seismic moment that was released during the eruption was 5320 times larger than what has currently been released since the end of the eruption up until today. One thing stands out for the post eruption phase, though, and that is that below 20km there has been more activity after the eruption, not less!

    It has been pointed out that there is no evidence of uplift in the GPS data. That’s correct, but consider that the caldera floor subsided by some 35 meters (after the GPS was installed) and the surrounding area by a few centimeters. Also consider that the subsidence followed a quadratic function quite well. Something that is true also for the accumulated seismic moment.

    Armed with this observation we can assume that the total plug movement is approximately linearly proportional to the total amount of seismic moment. That means that the corresponding post eruption movement of the plug would be something like 35m/5320 = 6.6mm. That’s for the plug, not the surrounding area. During the eruption the DYNC GPS subsided about 40mm. Assuming again a linear relationship, we would expect the current activity to correspond to 40mm/5320 = 7.5 micrometers. This is way too small to be observable on the GPS measurements.

    My conclusion is that most quakes are probably due to plug movement. If it is moving up or down is hard to tell (might beach balls help here?). The deeper quakes suggest magma injection, which would support uplift. At the same time the increased activity coincides with winter time and could simply be more subsidence caused by the added pressure of accumulated snow in the depression that formed during the eruption.

    • Excellent post!

      Without enough real data or GPS info all anyone can do is speculate at this point, pushing any one specific theory is just that, speculation …..even the “experts” are doing this.

      If BB proper is slowly moving away from the greatest rifting zone, it would not be unreasonable to wonder if the Holuhraun rift fissure is the future site of all of the “BB” activity. There is a great deal of very deep activity where the rift made a turn north and also at the edge of the glacier just before it surfaced, the fissure stalled there for a while. There is a possible deep connection at these points (papers have been written about this) that may not be a big connection today, but will only get bigger due to rifting, or maybe it is getting bigger as we speak.

      Without GPS data right on top of this fissure or in other key areas around BB one can only speculate on what is happening …..along with the theory an alien spacecraft crashed into the caldera 100’s of years ago and its energy core is about to explode.

      • One thing you can be sure o,is that what is happening now has happened before in some variation of the other.For example the area where the fissure erupted was a lava field and the eruption created another lava field .The caldera was created by a process of either violent eruption or extrusion and subsidence either way what is now happening is variation of the same process and eventual outcome.

        • Yes, that’s right. If I’m not mistaken, the eruption actually took place exactly along an old fissure in an already existing crater row. Look at the satellite image on google earth. The satellite image is from 2010 and clearly shows the old fissure and crater row.

    • The problem is the terms inflation and subsidence may not accurately portray the mechanics of a complex situation,this is not a balloon or a plunger this is a geological event comprising multiple factors,geology,temperature,gas content and viscosity of magma.The term deformation would be more accurate because inflation and subsidence would be occurring in conjunction,movement could be horizontal not vertical etc.

      • Agree, but this is an active rift zone, how much of the movement can be specifically ruled out as just rifting alone? Including the ongoing quake activity.

      • Sure, deformation is probably a better term. The deformation during the eruption was caused mainly by rifting, and by a reduction in the pressure below the central volcano. The rifting part will not be reversed, but the deformation due to pressure loss will in some sense reverse when new pressure is building. Of course it is a bit oversimplified, but I think it is quite beautiful how a really simple model can explain much of the things we observed during the event. From the propagating dike exactly following the slope of the mountain, to the volume of the depression from the subsiding caldera floor matching the volume of displaced and erupted magma.

    • I second IanF, excellent post tomasanderson2 …

      I have been pondering too about those deep connections too IanF.
      To be equal in the graphic ‘Released seismic energy’ before and after the eruption has ended, one should gather and capture the (deep?) quakes from a short period before the B. event started I think?

      How could the uplift of the northwest rim measured by the station KISA fit in this theory?

    • From the paper:2.3 Rhyolite Iceland and their formation.”In Iceland domes are generally thought to form where the crust is thick,i.e. more than 10km”.”It is at its maximum under the NE end of the Vatnajokull icecap,where the centre of the mantle plume is now believed to be.”

      • What evidence is there that magma is rising in the caldera? The quake activity caused by a draining chamber alone can account for the slight increase in geothermal activity noted.

        From the paper you quoted, which is an excellent read BTW

        Bardabunga is not on the list

        • Those locations were the known locations at the time the paper was written, I would presume and in areas where the crust is not as thick as the location of the current quake activity so the natural presumption is if domes can form in those areas then why not Bardarbunga.In the paper it mentions the difficulty in locating a cryptodome and the deformation caused by it.It mentions the famed cryptodome at Mt St Helens was only recorded by one ground station and there was no thick ice cap present,so a major subsurface dome was missed by most other observations

          • The magma would already be in place it would only be rising if it’s buoyancy is sufficient compared the surrounding rock (high gas content?).If the gas content is low than it would be more passive?But it would explain a cluster of earthquakes in one general location.We have the luxury of speculation that the scientists in public do not,it will probably take years for them to say one way or another with certainty what is happening there unless the volcano speaks first of course.

    • Now Geyser, for the third time. Publish evidence of a VT or a HT signal cought on a seismograph that belongs to Bardarbunga in the last couple of months.
      Evidence is in factual data after all.

      • I would also, since you are interested in cryptodome formation, point you to the seismograph data Godabunga. Then notice how noisy and prolonged it was. Now ponder things. Kindly.

        • Show me the shield volcano at Holuhraun?Show me conclusive evidence of caldera collapse.The point is you don’t have because those were just theories that may or may not be correct with passage of time.There is evidence of localized earthquakes swarms on thee caldera rim.

          • Now you are just being silly.
            One thing was a theory of what might come in the future. And what you are stating is something that has happened. Back to you, where is the VT or HT signal on a Bárdarbunga seismometer after the eruption?

            You are just not understanding the difference between volcanic and tectonic earthquakes. These are tectonic only. And tectonic only signatures on a ring fault is not a sign of intrusion. Ever.

          • I am not stating anything as having happened ,l am putting forward a possibility and constructing a basic argument for it.I could give numerous examples of volcanoes particulary caldera that experience shallow earthquake swarms that are not accompanied by volcanic tremor.Are all these quakes strictly tectonic,no of course not,they are related to the volcanic area they situated in through factors that may or may not be fully understood.There is constant confusion here between the effects of activity from different types of magmas.[..] I rest my case for now and see what happens.

            slightly redacted. choice of wording could have been taken wrongly – albert

          • If there were spectral signals of quakes, it would be a bit easier to demonstrate.

  16. An unchecked 3.7 at Tjornes fracture zone followed by a swarm a few hours ago.

    • After filtering out all the small earthquakes below M2 since they tend to have bad solutions you see that the earthquakes is ranging from 9.6km up to 1.8km.
      The spot has had numerous swarms over the last few years, the swarms are mainly tectonic.

  17. And here is todays recording from Fuego.
    The pyroclastic flows is currently following the scarp after ancestral Fuego decided that it was a good idea to fall down towards the pacific ocean in the Esquintla debris avalanche.


  18. The tectonic quake swarm at Kópasker is exciting though. I wonder how many swarms we shall see there this year because this is the second one in a very short period of time.
    Bárðarbunga I don’t know but there are still quakes going on in the dyke. Whether that is of any importance?

  19. I guess this publication is somewhat in line with what Geysersoze is promoting:

    Personally, I think their conclusions are a bit far stretched. Does their model accurately capture distant deformations, or is there another reason why the effects the model predicts are not visible in GPS data? What happens if you add more layers, model the actual topography of the region (instead of a flat slab of bedrock and ice), or consider other shapes for the magma chamber? What happens if you model the ring fault as an outward dipping cone (as suggested by analysis of older large BB earthquakes)?

    My greatest concern about the article is that they use the results from their model to disprove the subsidence as being caused by draining magma and a subsiding plug, but they don’t actually provide a model that accurately proves their own conclusions.

    • It’s a bit like the supposed discovery of the potential existence of “planet nine”,it is based on the perturbance of the orbits of dwarf planets.But first you must entertain the possibility of the giant planet ,otherwise you will be only modelling causes and may neglect what maybe the real culprit.Can they prove at this stage that planet exists conclusively,no,not until they see it.So it goes with the cryptodome, it cannot be conclusively proved until it either breaks the he surface as a dome or less likely violently erupts.

      • Maybe I’m wrong, but with doming I don’t think the authors refer to a cryptodome building from shallow magma, but rather a regional uplift caused by pressure increase in a deep chamber. They present a conclusion on how the depression on top of BB supposedly formed from flowing ice, but they don’t present any simulations results to support it.

        • That’s how I read it: their argument doesn’t seem to me (extreme amateur that I am) to support the existence of a cryptodome.

          • Yes on reading it you seem correct in that asumption,although the use of the term “doming” in that context seems a bit confusing,why not uplift due to magma chamber pressure?But also they suggest a subglacial lake and seem to rule out the piston model as well,as they say 60m drop in the caldera floor would have significantly fractured the ice,so the amount of subsidence was a lot less ,a few metres.

          • I don’t think your second sentence is a very accurate summary of the paper. For example, they don’t say that subsidence was less than 60m; they suggest that some of it was caused by ice flowing out of the caldera and some of it (iirc) by collapse as the shallow chamber emptied.

          • Page 38 quote:”Second, a 50 or 60 m piston-like displacement along the ring-fault is ruled
            out. The ring-fault would, for such a large displacement, definitely cut
            through the ice to form a large and easily visible fault, but this has not
            happened. By contrast, there has been comparatively little fracturing in the
            ice within the Bardarbunga Caldera during the subsidence, which suggests
            that the ice behaved as ductile, was flowing, right up to its surface. The
            results seem to limit the actual ring-fault (piston-like) subsidence to, at most,
            a few metres.”unquote

          • I have no horse in this race, so whether the paper we are discussing is plausible is immaterial for my point, which is that you seem to be misrepresenting it.

            According to you, “they say 60m drop in the caldera floor would have significantly fractured the ice,so the amount of subsidence was a lot less ,a few metres.”

            That is a very partial summary of the argument of the paper which, unlike what you’ve written, doesn’t allow the inference that the total subsidence is “a few metres”. The passage that you have quoted has been taken out of its overall context and even what you have quoted doesn’t warrant the inference.

            You quote from the paper thus: “The results seem to limit the actual ring-fault (piston-like) subsidence to, at most, a few metres.” The key phrase here is “ring-fault subsidence”: it’s the amount of ring-fault subsidence that was “a few metres”, not the overall subsidence.

          • Say what you will,the paper says that 10m of the 60m, if that amount of subsidence occurred ,would be just in the ice,so even if the floor was dropping like a piston the most the rock dropped was 50m.Also it says from memory the gps measured horizontal deformation would have to be in the tens of centimetres for this level of subsidence to have occurred ,I think it was probably in the tens of millimetres.The paragraph I quoted was part of the summary,so hardly taken out of context.

          • Your memory is wrong. The horizontal spread E and W was more than a few centimeter. It was meters and you know it.

          • OK Carl,quote from the conclusion in the paper:”First, the measured horizontal displacements in the surface rocks outside the
            ice appear to be significantly less than expected from modelling 60 m vertical
            displacement. At stations west of the Bardarbunga Caldera, horizontal
            displacements towards the caldera of the order of tens of centimetres would
            be expected but are not observed. This indicates that the vertical
            displacement in the bedtrock/crust, and thus the chamber roof-subsidence, is
            significantly less than than the maximum of about 60 m measured in the ice.”end quote.OK they don’t say what the displacements were but they infer not tens of centimeters.I think you are being a bit harsh.

          • The VON displacement was to the east about 8cm

            The DYN displacement was to the west about 380 cm

            So, logically you could conclude from the geographical locations of the GPS stations that the VON station, the one to the west of the Caldera, was most likely moved 10’s of cms to the west and the subsisdence moved it even more back towards the east, therefore the actual movement to the east caused by the collapsing caldera would have been most likely much greater.

            You cannot just ignore the rifting movement that took place at the same time.

          • I have news,I did not write the paper,it maybe complete nonsense,but the fact remains it was written by appropriately qualified people.I would guess there is a cut and paste from other papers thing going on to explain something,that can’t be fully explained with current knowledge about the system.

          • I think we all know you did not write the paper and are only presenting its arguments

            The image below sums up the movement in the area very well, you can even see the curved displacement/time lines as the draining of the caldera pulls them towards the south. This data only runs until September when the vertical drop was 16m.

            Other data that goes against this doming theory, once the eruption stops the caldera GPS started to rise. This makes sense if the ice is then flowing back towards the center of collapse.

            Image taken from here


            Freysteinn Sigmundsson, Andrew Hooper, Sigrún Hreinsdóttir, Kristín S. Vogfjörd, Benedikt G. Ófeigsson,
            Elías Rafn Heimisson, Stéphanie Dumont, Michelle Parks, Karsten Spaans, Gunnar B. Gudmundsson,
            Vincent Drouin, Thóra Árnadóttir, Kristín Jónsdóttir, Magnús T. Gudmundsson, Thórdís Högnadóttir,
            Hildur María Fridriksdóttir, Martin Hensch, Páll Einarsson, Eyjólfur Magnússon, Sergey Samsonov,
            Bryndís Brandsdóttir, Robert S. White, Thorbjörg Ágústsdóttir, Robert G. Green et al.
            Nature 517, 191–195 (08 January 2015) doi:10.1038/nature14111


          • My problem with the ice flow model is,where is the measured increase in ice outside the caldera.i.e. a growing glacier?My guess it melted and added to a subglacial lake.

      • But the converse can also be the case, which is what I think several people have been arguing.

        To develop your example, the advance of the Mercury perihelion might be instructive. Newtonian mechanics suggested an unobserved planet, General Relativity removed the need for one. Entertaining possibilities is important but sometimes in order to understand something we need a radical shift in our thinking which both respects the observational evidence and explains it satisfactorily.

    • I have a lot of problems with this.
      1. The subduction at the ice corresponds very well with the amount of magma that left the chamber.
      2. With doming they mean resurging dome.
      3. Tomas Andersson up above had a good point. There is actually quite a lot of external influence on Bárdarbunga due to the almost recordbreaking uplift going on at nearby Grimsvötn.

      • Another thing, we know that there is a mechanical connection between the reservoirs of Bárdarbunga and Grimsvötn. As magma poured out of Bárdarbunga the pressure inside of Grimsvötn temporarily shrunk. But, as soon as the eruption was over the pressure emediately started to rise in an unprecendented manner. If we now flip the causation logic around we see that increased pressure in Grimsvötn would cause a small increase of pressure in Bárdarbunga.
        So, there is actually no need at all for a real intrusion in Bárdarbunga to explain what we are seeing, it is more likely to be a false signal caused by Grimsvötn as it inevitably nears another explosive eruption.

        • This is exactly what all the data points to in my mind

          I have a problem with the slow dishing of the immense and thick caldera roof having to create a sharp break in the ice, just do not see that happening

          • The caldera floor would sink in the middle then fault then that effect would pull the rim down,so 60m in the ice is 50 m in the floor most of which would get transferred to rim ,so the ice would fracture all the way through at the rim and subside vertically with the floor rim,so the ice would not be able to absorb that amount of vertical collapse at the rim.That’s my interpretation.

          • Sorry, but what you just wrote is incomprehensible to me??

            All I know is this was not a sharp single fault break at all, but a gradual dishing over several kilometres as shown by radar measurements. No sharp break in the ice makes perfect sense

      • Well they agreed with at least 2 of my ideas from 2014,the subglacial lake,very little if any piston like subsidence and if by doming they mean resurgent caldera that’s 3.They haven’t reached the stage of calling the rhyolite cryptodome..yet😊

        • I will break it gently to you.
          A resurging dome within a caldera is something completely different to a cryptodome. And where on earth would the rhyolite come from? So far nobody has found evidence of rhyolite in Bárdarbunga. It erupts mainstream plume derived basalts.

          What is the meaning of a resurging dome? Well, that is when a caldera is refilling with magma and it forms an inflating lense-like object (dome-shaped) inside the caldera. A cryptodome is an emplacement of magma that could be called a failed volcano. And one thing is clear, cryptodome formation is increadibly noisy and takes time.
          Take Godabunga for instance. First a conduit from more than 20km depth formed. This was a new conduit in between the one leading up to Katla and the one leading up to Eyjafjallajökull. After that the emplacement itself took place. This caused 3 year long earthquake swarms containing tens of thousands of earthquakes over a 20 year long span of time. Then Fimmvörduhals happened and Godabunga pretty much shut down.
          So, do not think that cryptodoming is a fast and rapid business.

          I hope this made things clearer for you.

        • Is not Bardarbunga “the Queen of all volcanoes” in Iceland,so by extension other systems would not have excessive influence on such a massive system ,but the opposite could be the case.Interesting in that paper they mentioned wher the eastern Iceland volcanic zone,the Kenyan rift valley and the Taupo volcanic zone as areas where regional stress caused by doming in shallow crust magma chambers causes the formation of ring faults,interesting to see TVZ in that mix of examples.

          • Grimsvötn and Bárdarbunga are equal in size, but the caldera is slightly larger at Bárdarbunga.

          • And the back story about Grímur’s favorite fishing hole is a hoot. His wife cursed it. {Grímsvötn} Being a giantess, I guess she tended to have a sour disposition. Not quite as convoluted as Katla’s story, but still entertaining. And the selection of the name for Gjálp was pure genious. The Gjálp fissure eruption (between Bárðarbunga and Grímsvötn) was probably a source for a Jökulhlaup, like the tale of Thor and Gjálp… though Thor’s solution to mitigate the flooding was a bit rude by anybody’s standard.

            Back to the real world. The Gjálp eruption is probably another migrating Bárðarbunga originated dike that intruded into the Grímsvötn fissue swarm… or at least tried to, but broached the surface before getting anywhere really interesting.

  20. Been watching this antacid commercial of and on for three days, and just now realized that the thing chasing the guy around the resturant is a T-bone steak..

  21. I think what Geyser is saying *IS* in fact possible. But with that said, I think the important thing that needs to be emphasized is that it’s extremely unlikely in the near geological future, especially given present conditions. Also, there aren’t really any signs that this any sort of dome is forming or bulging at the volcano, so it’s extremely doubtful that this is something occurring now.

    If we’re going strictly off hypotheticals, we could more or less say a caldera eruption at any of 300+ volcanoes is possible in the next year. That’s just the nature of volcanoes in general.

    I would honestly say, if you’re looking for excitement from volcanoes, Bardarbunga probably won’t provide too much of it outside the fact that it’s extremely well monitored, and thus easy to follow along to.

    • Great wrap up of this discussion

      For me, the interest is mainly due to its location, a rift zone above water. Where else can we see plate tectonics actively changing the landscape in such a short period of time, it’s just amazing!

      Can’t wait to visit

    • That says it all a given year the chance of an eruption in any volcano is quite small and in calderas a very slim chance,over a hundred years the odds are high for frequently active volcanoes and still small for a caldera.So yeah the odds of a large eruption in the Bardarbunga caldera in a lifetime even now are probably quite small.It could be that the next caldera forming eruption will be from an unknown site.

      • “Ding.” And the spooky bit, is that under the law of infinite probability, eventually, it will happen, no matter what. Whether anyone will be around to see it is a different story.

      • No, seems like this eruption is picking up speed as it goes. A bit unusual from a volcano that has been erupting for years.

        • Kind of hard to read the seismo when they have it turned up so high. Looking at the plot, it just looks like a big jumble of seismicity for the last week straight – difficult to even see the spikes and valleys in there.

          • It is an old seismo, I am not sure it can be set down. And, the signal is really strong to begin with.

        • “been erupting for years”

          Is it possible that what is now happening is that mostly fresh decompression melt is getting into play?

          It would be quite nice if a petrological guy was looking at the chemical composition of new vs old ejecta… Might even be a good paper in it if one was looking for something to write on.

          • I wholeheartedly agree.
            Fuego has switched magma as the ancestral Fuego up and walked towards the pacific beaches. So, keeping track of any changes is probably a good idea.

  22. Hey all. 🙂

    Heading over to Japan again, last time had a visit to Kagoshima and that little old monster next door. 🙂

    This time, when I am over, looking forward to climbing mount fuji and then while I am around Kyushu, I will pop over to mount Aso for a peak.

    Does anyone would like samples or special requests?

    Just hope the JMA is not hiding things.. 🙂 (That’s is a silly joke)

    /Released from the Dungeons.

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