Activity at Katla and Bárdarbunga

Hand coloured image of the VEI-4 1918 eruption of Katla. It was the largest explosive eruption on Iceland during the last century, only the 2011 Grimsvötn eruption was larger.

Hand coloured image of the VEI-4 1918 eruption of Katla. It was the largest explosive eruption on Iceland during the last century, only the 2011 Grimsvötn eruption was larger.

Lately the internet has been filled with the usual doom and gloom about Katla. And since there has actually been a bit of unusual behavior I find it merited to actually write about the volcano.

Background on Katla

The accumulated seismic release of Katla (red), Gódabunga (green), Torfajökull (purple) and Eyjafjallajökull (blue). This is the current year counted from 1 april 2014

The accumulated seismic release of Katla (red), Gódabunga (green), Torfajökull (purple) and Eyjafjallajökull (blue). This is the current year counted from 1 april 2014

The volcano resides under the Myrdalsjökull glacier and it is one of the larger volcanoes on Iceland. It has suffered at least two large caldera forming events, but the last one was sufficiently far back in geologic history to have given the volcano sufficient time to rebuild its magmatic system fully.

This last thing is evidenced in among by the for Iceland unusually large scale of the explosive eruptions coming from the volcano. In short, after a caldera forming event the magmatic system is normally damaged and needs considerable time to rebuild before the volcano can have large eruptions again. As time goes by the volcano incrementally has larger eruptions on average until the magmatic system has grown too large and forceful to be contained and a new caldera formation occurs.

Notice how calm Katla was during the last year. It is th calmest year on record so it is a really bad example for comparison. But the human attention span is short so todays activity seems huge in comparison.

Notice how calm Katla was during the last year. It is th calmest year on record so it is a really bad example for comparison. But the human attention span is short so todays activity seems huge in comparison.

If we look at the last two large caldera formations in Iceland after deglaciation we find that Grimsvötn had one around 10 000 years ago and that it follows pretty close to the theory of gradual eruption size increase. The 2011 eruption is probably the largest in the last 10 000 years from that volcano, but it still has thousands of years to go until the next VEI-6 caldera formation. Bárdarbunga on the other hand had its VEI-6 caldera formation in 1477 so the eruptions there are now pretty meek VEI-1 or VEI-2 eruptions.

So, even though both Grimsvötn and Bárdarbunga are much larger volcanoes, Katla is suffering from larger eruptions. The current average is that Katla has 10 times larger eruptions compared to Grimsvötn on average, and a whopping 100 to 500 times larger eruptions than Iceland’s largest volcano Bárdarbunga.

Now if we compare to the noisiest year for Katla on record (2011-2012) we find that the accumulated Strain release for the year was almost 10 times what has been released so far. And remember, nothing erupted back then.

Now if we compare to the noisiest year for Katla on record (2011-2012) we find that the accumulated Strain release for the year was almost 10 times what has been released so far. And remember, nothing erupted back then.

So yes, Katla is definitely a force to reckon with. My beef is rather that Katla is not showing any great signs of an impending eruption. So what then is all the fuss about? Let us take a look.

Current signs and portents

Lately there has been a low level Jökulhlaup coming out from the glacier. It has so far just given a slight increase in water levels; instead the warnings are because of the greatly increased amount of volcanic gasses that are released where the water comes out. And that gas can be deadly in high doses.

This is a sign that the hydrothermal activity has increased under the glacier and that somehow water has come into contact with a hot area. It is more likely that water has found a way down than that magma has found a way up.

Now, let us compare this years Katla with the massive intrusion that happened in Gódabunga back in 2002-2003. It released twice the amount of what Katla did during its noisiest year, and Godabunga went on like this for 3 years in a row.

Now, let us compare this years Katla with the massive intrusion that happened in Gódabunga back in 2002-2003. It released twice the amount of what Katla did during its noisiest year, and Godabunga went on like this for 3 years in a row. Please do not that during the same Gódabunga swarm Katla still had twice as much seismic release than it has had this year.

Now over to the earthquakes that have been seen lately, first of all, there is not an unusually high level of earthquake activity. On the contrary the current levels are about the normal level of earthquake activity for the volcano. Instead it is the last two years that have been unusually calm. If we then go on and look at the noisiest year recorded since 1992 we better understand that it takes quite a lot for Katla to erupt.

Neither has the earthquakes pointed to magmatic components so this is most likely ordinary tectonic to magmatectonic earthquakes. Some have also pointed to the fact that some earthquakes have been rather deep, but this is also normal for this particular volcano.

EW section (facing south) of Katla. The tiny rainbow coloured dots are earthquakes from 1995 to present. On a different scale, the spheres represent earthquakes from the past month.

EW section (facing south) of Katla. The tiny rainbow coloured dots are earthquakes from 1995 to present. On a different scale, the spheres represent earthquakes from the past month.

Now over to “overdue”. Yes, Katla tend to be fairly regular in the time between eruptions, but there have been longer repose times than this. So talking about overdue is not giving anything to the discussion. Saying that the volcano has had a statistically slightly longer repose time than the average is more correct.

Now, some might think that I said above that Katla is likely to go caldera, but that was not what I was saying at all. I am just saying that Katla has gone further down the road to a potential future caldera formation than the other two large Icelandic volcanoes I compared with. In reality the chance for a caldera formation is probably somewhere in the region of 1 in 50 right now, and that is not really worth worrying about.

A peculiarity

"The Peculiarity". All images above are from the Icelandic Met Office.

“The Peculiarity”. All images above are from the Icelandic Met Office.

In the seismic strain release charts I found a small peculiarity that I had not pondered upon before. It seems like the earthquake swarms tend to migrate outwards from Katla. First Katla has a swarm, then a much larger swarm occur a few months later at the Gódabunga cryptodome, and yet another few months later a smaller swarm takes place under Eyjafjallajökull.

This leads me to hypothesize that the volcanic area is prone to magmatic pulses that first impacts at Katla and then spreads outwards to the west.

There is also the possibility that a larger than normal amount of magma is not going into Katla and instead moves into the proto-volcano of Gódabunga and secondarily into Eyjafjallajökull, and that might explain the longer than usual repose time of Katla. This is though just a bit of speculation on my part. It might though explain why Katla and Eyjafjallajökull on two occasions have erupted closely together in time.

Bárdarbunga

Bárdarbunga is the largest Icelandic volcano currently active, and it is also the largest producer of lava in the world during the last 10 000 years. The reason for this is probably that slightly north of Bárdarbunga you find the center point for the Icelandic Hotspot.

As I mentioned above the volcano went caldera in 1477 after a prolonged rifting fissure eruption in the southern part of the fissure swarm (Veidivötn). It seems to greatly have affected the size of the eruptions from the volcano; the question is more if it also will have affected the large rifting fissure eruptions that have burst forth from the fissure swarm on average every 500 years.

The current increased activity has been taking place at a spot halfway between Bárdarbunga and a volcano further north on the fissure swarm named Kistufell. This swarm has over time slowly moved closer Bárdarbunga himself. Depth and signatures have ranged from the MOHO up to close to the surface and the signatures have ranged all the way from purely tectonic to volcanic/magmatic.

My personal belief is that Bárdarbunga is gearing up to another VEI-1 to VEI-2 eruption like the one it had in 1996 when it produced an ash column for a few hours that reached 3.5 kilometers height at the end of the more famous Gjálp eruption.

Kistufell

One of the few images in the world of faraway Kistufell.

One of the few images in the world of faraway Kistufell.

At the same time a low level highly persistant swarm has been running over at the Kistufell volcano. The swarm started with deep magmatic earthquakes that gradually have risen upwards. The vicinity between the volcanoes and the fact that Kistufell is point zero seems to suggest some sort of magmatic pulse moving upwards from the Hotspot/Mantleplume.

If Kistufell erupts all bets are really off for how it would behave. It has probably not erupted during the last 10 000 years and how such a long repose time volcano would behave is written in the stars, especially for a volcano that is sitting straight on top of a large powerful mantleplumes core center.

Personally I find it much likelier that the Bárdarbunga volcanic swarm erupts at the current time that that we have an eruption at Katla, but that is my opinion based on the current evidence. Others might disagree with me, but in the end the only really important opinions are those of the involved volcanoes.

CARL

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174 thoughts on “Activity at Katla and Bárdarbunga

  1. I’m under the assumption that the last Katla caldera session was the Vedde ash eruption? If so, that wasn’t all that much older than Grimsvotn’s last caldera eruption, but Katla would seem much further along.

    • Problem with the Vedde ash is that it is from either a corresponding VEI-5 at Katla or another VEI-5 moment at Askja.

      • Only vei-5? Why is it that the Vedde is so notorious then? I’m assuming it was simply an upper-limit VEI-5, whereas the other eruptions were small VEI-5 eruptions?

        Also, are there ash deposits found anywhere for the Caldera-forming eruptions at Katla?

        • It is just famous because of it being “The Vedde Ash”. There are other large ash deposits, mainly from Hekla found also in northern Scandinavia that is pretty equaly impressive but less illustrious.

          Any caldera formation ash out of Katla is long scoured away by the Ice Age since it probably happened during the last glacial.

          • That makes sense then. I had always figured the whole glaciation thing was fairly relevant here, but I had thought I heard there were quite a few areas in europe that weren’t glaciated. I would imagine some of those eruptions are probably hidden within the Greenland Icecap, right? I would just imagine that ash record is relatively difficult to find, but I’m no expert.

            • Depends I guess on the wind direction a bit. But remember that even a VEI-7 does not give a thick ash layer… Aniakchak did not for instance.

            • I didn’t realize I was the only one in the camp of “those eruptions were probably bigger than they say they were”. For anybody in the know, how accurate is the estimate of DRE for past and ancient eruptions? For instance:

              The eruption of the Kikai caldera around 6000 bc was one of if not the single largest eruptions in the last 10,000 years. It’s generally estimated that the DRE is around 150 cubic KM. With that said, this eruption took place in the middle of the ocean. How accurate can they really be for estimating DRE down at that depth? How much of the ash gets carried away in ocean currents?

            • As usual, DREs are normally more accurate for eruption seen, and more accurate for caldera formation. Generally they are more accurate for Iceland than other places due to glacial ice cores and generally good research in Iceland and the Scandinavian moors.
              But if one look at Katla it is fairly clear that the Caldera is not that well defined at all and it kind of implies an old caldera. And no, you are not the only one in that Camp 😉

        • Nig nice post Carl!
          The Vedde ash was proven in at least a paper I read to be from Katla. But of course we still have our doubts. I read iIts ash thickness in Iceland is less than the caldera event of Grimsvotn that happened also around 9000 BC. But ash thickness in Iceland from that time is difficult, because Iceland was mostly glaciated at that time.

          Vedde ash from Katla was probably a strong VEI5 or weak VEI6, and Grimsvotn caldera was probably a small size VEI6 but a bit larger.

          And yes, it seems that Askja also had some big event around that time. So it gets pretty confusing..

  2. I can’t watch the video?
    Am I the only one? Might be that I need to reboot my computer.

    Thank you Cryphia for the wonderful plots that should have been appended from the beginning, but due to heatstroke I suffered from premature posting of the article…

    • Video works fine for me even on the smartphone 🙂 Its interesting how you can almost get a feeling of the magma chamber at Katla where there is the area of hardly any quakes. 🙂

  3. Thanks, Carl – nice! 🙂 Regarding your comment, “This leads me to hypothesize that the volcanic area is prone to magmatic pulses that first impacts at Katla and then spreads outwards to the west.”

    I wonder if this can be seen on a more macro level Or rather, can this be seen / proven across Iceland in relation to the hot spot? As pulses to Katla trend west, is there a similar pattern within the timing and locations of intrusions or magma/tectonic quakes that can be used to better understand the shape, strength, and workings of the plume plus its interaction with the plates.

    Not sure if I’ve conveyed that question clearly … Nevermind 🙂

    • Weeeeell… I kind of hinted towards that didn’t I?
      Notice the progression from Kistufell via a spot between Kistufell and Bardarbunga and then downwards to Bárdarbunga.
      Anyhows, I would warn from drawing to much conclusions from my idea. It is an unproven theory at best, at worst it is a huge bag of horseradish… :mrgreen:

      I just wanted to point towards it so that we could discuss it at bit 🙂

      • Next question 😉 the cause of the direction: path of least resistance or force from the pulse itself, or both?

        • In the case of Bardarbunga magma is probably moving along the Bárdarbunga Fissure Swarm. But at Katla the situation is more confusing.
          Earthquake plotting (done by Lurking a couple of years ago) showed that Katla, Gódabunga and Eyjafjallajökull have distinctly different feeder tubes at depth. So it seems that the magma at depth moves for some reason westwards down at the MOHO instead of following the direction of the South Icelandic Fissure Swarm (MAR part).

          • Right, thanks! Where’s that old wedge of continent situated again, or is that understating things too much to suggest it could be influencing the path of direction?

          • I don’t know if anyone ever postulated a position for it, only that a sliver of one may exist and explain the oddball chemistry of some of Hekla’s spewing. I think at one time Carl mentioned that some of it was more characteristic of subduction zone magma. Seeing as that a subduction zone did exist in the area when Avalonia was around, and then may have had a hand in forming the Caledonian orogenic belt from when it turned into continent-continent collision, it seemed plausible to me. After all, the Jan Mayen micro-continent got sliced off of Greenland, twisted, and welded to the Eurasian plate, why not have a shard still stuck under Iceland somewhere. It is about twice as thick as a more normal volcanic island.

  4. I find that the Fimvourhous? eruption just before Eyjafjallajökull was rather intriguing. It was definitely the prelude to the big event. I would really like to know what eruptions happened after the 1821 Eyjafjallajökull event. The IMO site doesn’t go back that far. I feel as though the scientist have fallen flat on there faces unless they were trying to put the fear factor into the public which isn’t that hard to do in this day in age in regards to Katla. If the farmers around the volcano until prior to an eruption are not afraid why should we?

    Grimsvotn has remained quiet lately despite all of the activity going around it.

    • Yea, I am also interested in the Grimsvotn dilemma in this case. I would expect Grimsvotn to be almost the first to start responding to any potential “magma pulses” from below.
      But thats just me. 🙂

      • Grimsvotn already responded to that pulse, In 2011.
        It will take a while until the net eruption. Probably 2015 or 2016.

        I would be more hoping for larger eruptions in other volcanoes around Grimsvotn, and under Vatnajokull. They are all located near the hotspot.

        • I would say that currently the earliest point for a Grimsvötn eruption would be in 2017. Judging from the inflation rate and the lack of seismic activity we are at a minimum of 3 years as of now. Personal guess would be between 2017 to 2020.

          • That was what I was thinking just counting the days and the chart which the count is at 1153 days since the end of the last eruption anywhere between 2 years and 5 years realitically

    • The pressure at Grimsvötn has not buit up back enough yet to cause an increase in seismic activity.

      DU, remember that Grimsvötn is on a completely different fissure swarm than Bardarbunga, and also that the magma system is humongous there and to boot it just bopped out between 1 and 2 cubic kilometers of lava and a whopping 0.5 Km3 of tephra. I think that Grimsvötn will nap for a couple of years more since it has done its “thing”.

      • A very obvious point which I somehow forgot. Thanks 🙂

        on a side note, lets say that Hekla would hold for a few more years, and then we would have Hekla, Katla, Grimsvotn, Bardarbunga, Kistufell, Kverkfjoll and Herdubreid erupt all in the same week or month. Now wouldnt that be a sight to see… 🙂

        Another side note: I would assume that since Katla is dormant all this time, its magma chamber should have a fair share of Ryholite in it. 🙂 Just an assumption. Tho I guess it will really take a mother of all intrusions to wake this “sleeping beauty” up. 🙂

        • One should also remember that a volcano the size of Katla has several magma reservoirs and some of them might have “rhyolited” for hundreds if not thousands of years.

          Only thing we do know is that sooner or later Katla will erupt, but nothing is pointing towards it at this particular moment.

        • Katla has been dormant just short of 100 years, and prior to that, erupted on average every 60 years or so.

          In a geological time scale, it has been extremely active. I’m sure there will be some evolved magma, but I wouldn’t think that its simply a result of the 100 year repose time, which realistically isn’t all that long when we’re talking about normal volcanoes.

          • Remember that there is more than one “chamber”, so there could very well be a “chamber” down there with magma that is highly evolved and several centuries old. Just look at what happened at the pocket of rhyolite at Askja when it got reheated by new hot basalt…

            • Good point. The eruptions repeating at different (but kinda the same) places in the caldera really points to that.
              With all the westward propagations, perhaps its time for some of the westward “points” to erupt again. 🙂

            • If anything “westwards” erupt it would be Gódabunga that erupts. No, so far the very few signs and portents point to two areas of interest. One is at the NNE corner, and the other points towards the center area and the EW-trending fissure that was responsible for the large 1755 VEI-5 eruption.
              I would though like to point out that if an eruption happens where a previous big eruption has happened it is not that likely to be equally big.

            • Damn it, another logical point. Why cant I figure it out, when it is so easy to understand once you read it and think about it :/

            • Remember that the oldtimers are cheating, we have by now read almost everything about these volcanoes, and debated them for years… It is easy to sound smart then 🙂

            • Yea thats true, but still, its so frustrating when the reality is actually so logical (atleaast some basics) once you really think about it when someone tells you/you read it. 🙂
              So thanks for all your patience. 🙂

        • All volcanoes erupting at nearly same time: statistically very dificult.

          But we had somewhere near 1727, 3 volcanoes erupting in the same year. And that decade had two more years with 2 volcanoes erupting same year, and almost all years of that decade feature an eruption.

          That’s what can happen.

          Also remember: Skaldbreidur eruption lasted many decades, and Edlgjá at least 5 years. So eruptions in Iceland can last for a long time, sometimes.

          But coming back to the statistics. Let’s say 10 or the more active volcanoes in Iceland. Each erupt with a different frequency, let’s say an average of 50 years between eruptions for them (some like Grimsvotn can erupt every few years, others like Katla and Hekla erupt an average every 50 years, but others like Askja can go without an eruption sometimes for a few centuries. Frequencies vary wildly. But this gives the Icelandic average of 50:10 = 5 years of gap between eruptions in Iceland.

          I am not going into the maths, but we could calculate the odds (like 1 time oer 1000 years, or 1 time per 1M years) of two volcanoes erupting at same time, three volcanoes erupting at same time, four volcanoes erupting at same time.

          We have at least once in 1000 years; 3 volcanoes erupting almost simultaneously (or within months of each other).
          Perhaps once or twice a century with 2 eruptions in same year, or at same time.
          But it would probably really rare to see 4 volcanoes at same time.

          Maybe someone can do the maths.

          • 1727 was probably the initial year of the pulse that down the line lead to the Laki hubbub. This time around the pulse cycle and the rifting cycle are more “together” in time.

          • Something like this, in the most simplified case (All 10 volcanoes erupt with a 1:50 chance per year):
            Image and video hosting by TinyPic
            Credit mainly goes to husband, I did the table though 😉 .

            • so about the same as a single lottery ticket winning the jackpot as having 9 in the same year, when only one ticket is bought each year.

            • One should remember that 7 separate volcanoes actually did erupt in 1983…

              My guess is that if a “magma pulse” and the time for the Icelandic rifting occurs at the same time the likelyhood of several eruptions in one year is far better then otherwise. Both of these events increase the rate of eruptions for all of the volcanoes near the mantleplume and near the MAR-line.
              So, what is winning a lottery ticket during normal times tend to be more of a case of “shit happens” during those times.

              Remember that during Veidivötn we had at least 3 volcanoes erupting at the same time, with it being fairly likely that one or two more was into the fray but was overlooked from the bigger cousins antics.

  5. List of eruptions in Iceland 1821 to 1900.

    1821 Eyjafjallajökull VEI-2
    1823 Katla VEI-3, 1860 VEI-4
    1823 Thordharhyrna VEI-2, 1887 VEI-2
    1830 Reykjanes VEI-3, 1879 VEI-1
    1838 Grimsvötn VEI-2, 1854 VEI-2, 1867VEI-1, 1873 VEI-4, 1883 VEI-2, 1891 VEI-2, 1897 VEI-2
    1845 Hekla VEI-4
    1862 Bárdarbunga VEI-2
    1875 Askja VEI-5
    1878 Krakagigar VEI-2 (By GVP wrongly written down as Hekla)

    These are the volcanoes that erupted during that period. And this is basically pretty much how Icelands history have looked. About once per century a really oddball volcano erupts, otherwise it is pretty much these volcanoes that erupt over and over again. Especially Grimsvötn does the over and over again thing.

    • Curious, you mentioned once every 10,000 years or so Iceland gets a magma event of over 50 cubic KM (typically basalt). Which over the last 10,000 years have approached this #? I would guess one would be theistareykjarbunga, but have there been others (I know the lava fields near bardarbunga are huge)?

      • I do not remember saying exactly that.
        What I think I said is that Iceland has had a couple in the last 10 000 years.
        There are 3 I can name from the top of my Head. Those are Theistareykjarbunga, Odadhahraun out of Askja and Trölladyngja.
        Perhaps Skaldbreidur too, but I am not sure if that put out that much, but it was really big. And then you have the 35 km3 Thjorsahraun out of Bardarbunga. So at least 5 eruptions bigger than 35km3. None in the last 8000 years.

        • Ah, yeah, sorry – I didn’t remember the exact quote. Have to imagine glaciation played a very large role here.

          Out of curiosity, would these eruptions be similar to the dead zone rift eruptions? Or would these eruptions come from the presumably massive magma chambers near these volcanoes? I would have to imagine the magma largely comes from the MAR in these scenarios since Iceland isn’t great at holding pressure in, but that’s just a presumption.

          • All of them formed as the fissure swarm rifted apart, same as at Laki. Well, with the probable exception of Theistareykjarbunga. It is the only central volcano that had an eruption on that scale. Skjaldbriedur and Trölladyngja are one off eruption shield volcanoes, and Odhadhahraun and Thjorsahraun are rift eruptions.

      • And to answer your other question, Krakagígar actually means Kraki’s Craters while Crow’s Craters would translate as Krákugígar. Due to declension the nominatives kraki and kráka become kraka and kráku (respectively) in their genitive form needed for the compound words. Also note that in Icelandic the accented vowels denotes independent vowels not emphasis like you might be more familiar with. In the case of a and á, a like (a) in ah and á is like (au) in Faust or (ow) in how.

        As for the etymology, Krakagígar are (i think) to the east and west of mount Krakatindur (Kraki’s Peak). The mountain itself gets its name from the tallest peak, Krakanum (The Kraki [dative form with definite article suffix]). From what I can figure out, kraki is the Icelandic form of the Norwegian word krake, which you might know better in the form kraken.

        So… I guess that means that The Kraken sits atop Kraken’s Peak with the Kraken’s Craters stretching out to the east and west. 😏

        Sorry about the long winded response, it’s 4:40 am Friday and I’ve been up since 1:30 pm Wednesday. Got no work coming to my water jet and needed something to keep myself awake

        • Krake would actually be “The poor fool” in modern scandinavian languages like Norwegian and Swedish.

          If you swing by with the waterjet you could spray me down… Here it is a class 2 Heat Warning… The first ever in Sweden. Now for putting a bag of frozen peas in my groin to cool myself down in the 39C office.

        • I appreciate the rumination upon the word. Though I find the topic fascinating, the terminology behind the genuflection of clauses and phrases make my eyes gloss over. And yes, I intended to use genuflection in that manner, after all that is essentially what the words are doing among themselves as they trundle down through history. 😀

  6. Been driving. I really appreciated the couple at the gas station moving away from the pumps to have a smoke… but I really would have thought even more of their safety conciousness, if they didn’t stand next to the propane tanks.

    I decided it was best to not stick around. There has been nothing on the news, so I guess they got away with it.

      • I was musing to myself about a fictional competition among sports teams should driving on the Interstate be thought of as a competition. The Alabama Dirtbags vs the Georgia Assmonkeys. Mainly from watching two idiots treating Hwy 85 North out of Fr Walton Beach as if it was the straightaway at a Nascar track. In the competition that I was witnessing…. the Freightliner won. Both of them got trapped behind him as the rest of us just motored on by. The funniest part was the gesticulation they were making to each other. The rest of the trip home was uneventful until I got to my exit off of the Interstate. I came across an SUV in the emergency breakdown lane right next to 70 mph traffic and a dude trying to get out and check his engine while traffic was blowing by at high speed. That’s a bit dangerous, so I called the FHP non-emergency number so that they could send the “Road Ranger” truck to go assist him. Most of the phone call seemed like FHP wanted to know more about who I was than where the disabled vehicle was at.

    • They’ve got a clerk there that is quite a cutie pie. She instantly reminded me of a girl from… about 35 years ago…(sigh…) She is also somewhat oblivious to the propane storage rack. I saw her taking a smoke break near it sometime last week.

  7. Apologies if posted before – nice video of how the lava tube at Tolbachik looks now, courtesy of the Belousovs

  8. If I remember correctly, I believe Katla also has multiple magma chambers, and the area beneath the volcano is presumed to more resemble a mesh of magma pockets (obviously some being pretty large). So this also probably has a large degree of influence over things in this area.

    Not sure if this is correct, but I thought I remembered hearing this somewhere.

  9. What would be interesting to see, is a one year earthquake plot for the year running up to Eyjafjallajökull 2011.

    • In this 3D plot of the Myrdalsjökull area from last year, the light blue swarm was the one leading to the Eyjafjallajökull eruption.

      • The interesting part is that the Eyjafjallajökull swarm did not cover the Fimmvörduhals area, but the swarms of Gódabunga did…
        Lurking then tracked magma moving onwards from Fimmvörduhals to Eyjafjallajökull during the days between the two eruptions.

  10. Re. Grimsvotn… I may have posted in these terms before, but it bears repeating. A year or so ago, I was reading about the 2011 Grimsvotn eruption. Apparently it marked a bigger development that I realised.

    The paper concerned analysis of thorium content in Grimsvotn magmas.

    The general picture is that apparently, ever since Laki, thorium content of magmas erupted in that area has been steadily increasing, up to and including the 2004 eruption. This is interpreted as being due to fractional crystalisation processes concentrating thorium over time; it seems that even as late as 2004, the system was still erupting the last dregs of the ‘Laki’ pulse of magma!

    That all changed in 2011; the products of that eruption contained less thorium than any eruption since Laki (if I’m remembering what I read correctly). This is interpreted as strongly implying a significant new source of fresh magma, straight from the mantle. The rapid inflation prior to the eruption, the size of the eruption, and the immediate and rapid reflation starting immediately after eruption ceased tend to confirm that – and, perhaps, bode ill for the next few decades.

    I wonder what the chances are of another Laki-type event in that timescale?

    I was aware of discussions in these general terms before, but I hadn’t previously seen the evidence of the thorium. I’ll see if I can dig up the reference.

    • It is basically true.

      I just want to point to a small but far from insignificant detail.
      Laki never drew magma from Grimsvötn, Laki was decompression melted mantle material. Basically the removal of approximately 150 cubic kilometers of mantle material created an area that has more or less siphoned off new magma as it arrives thusly limiting the magma going up into Grimsvötn. The part of the Laki lava being totally unevolved mantle material is beyond a shadow of a doubt judging from the 1100 samples my previous company had…

      Now over to another point that the paper in question forgot (I’ve read the same paper). And that is that Grimsvötn has several magma chambers too, and the eruptions after Laki has not been from the main vent up untill 2011. Instead it has been from vents towards the northern side of the Caldera or rift eruptions in Gjálp area. Or from Thordharhyrna which GVP wrongly lumps together with Grimsvötn. And Thordharhyhrna is famously thorium rich (almost to the point where it becomes a mineable mineral deposit).

      My argument with the paper is that it has a way to simplistic view on the complexity of Grimsvötn and Icelandic volcanoes in general.

      • Perhaps a better way of looking at it is, a large pulse of mantle material arrived in the area. Some was erupted at Laki, the rest formed reservoirs in the Grimsvotn system, and has been erupted, with continuously evolving thorium concentrations, ever since.

        2004 represented the final eruption involving that pulse of material, and 2011 the first of the newest pulse.

        That seems to be part of the picture, even if the whole thing is significantly more complex. But the trend in thorium, and the ‘different’ nature (vent and thorium poor) of the 2011 eruption does make some kind of sense…

        • It does make sense. In general it seems like Iceland Pulses about every 260 years. It seems to correspond quite well with the times of the rifting.
          Right now we are waiting for a potential rifting, and I think we are starting to see the signs of the upcoming pulse.

  11. For the dragons, I’ve started to write a post, but then realized it was going to be a behemoth (will probably split into 2-3 posts). I may need a bit of help on a few topics where certain people have more knowledge than I, but hopefully it can provide some much needed content for times where there isn’t much interesting happening in the volcano world.

    • In regards of your actual question whilst the Dragondoom ponder ponderously in the Ancient and Mysterious Den…
      It would be delightful to have 3 new posts from you. I think I speak for all the other Dragons in that we would happily help out in any way we can.

        • There should be two invites sent to your email, one for the Den and one particular other.
          Go to the Den and Log in and we will explain. 😉

          • for some reason, all I was able to do was subscribe to the blog. This post may be a little while in the making, been pretty busy with work recently :o.

            • I have asked Cryphia to Gently guide you into the Den, and from there I will take over explaining what needs to be done with the second invitation. 🙂

    • Jon has it in English:

      http://www.jonfr.com/volcano/?p=4628

      “According to Icelandic Meteorological Office, a large landslide fell yesterday (22-July-2014) around midnight in Askja volcano, the landslide did go into Askja lake creating a flood wave that was 100 to 200 meters high. It did reach the other end of the crater lake and did flow over its edge, some water did go into Víti crater. This landslide took place in south part of the Askja lake crater (best information I have at the moment). Harmonic tremor was detected following this events, it was recorded for 20 minutes according to news reports (no image since Askja harmonic tremor plot image is missing in IMO website).”

      Mike

      • Pretty hefty tsunami.
        I do not make to much of the harmonic tremor. I would say it is more likely to be due to gas releases as the lakes sloshed about.

        • Which is at the best of times a dangerous concept due to the large amounts of volcanic gasses that are released there. It is only safe on windy days, otherwise that dip can be your last swim.

        • It turns out that an acquaintance of mine is somewhere in the vicinity of Askja walking on fot from Myvátn to Askja caldera. Latest news is that he had walked fifty kilometers from his starting point towards Askja.

      • Flood wave height is wrong. Heard interview with geologist Höskuldson on RUV news ths morning.
        Jóns confusion is of it progressing 100-200 meters onto shore, probablu no more than 15 – 20 m height, but impressive anyways. Seems part of Caldera wall side collapsed, blamed due spring meltwater in unstable material, but some water did spill into “Hell” (Vítí Crater)

  12. And a special for Lurking to cheer him up in the heat…

    A Zombie virus is rapidly spreading.
    UDN – Ulcerous Dermal Necrosis attacks the skin and the brain and causes severe zombielike features.
    The virus is spread through bites and originates in the salmon fish. If humans are bitten by UDN-salmons or by UDN-humans they will catch the zombie-desease.
    Anyone who think I am joking, think again.

    Image and video hosting by TinyPic

  13. Speaking of magma pulses, if one doesnt come up soon, the entire Iceland is going to be an earthquake “dead zone” 🙂

  14. Oh, I do quite like the EMSC app alerts, nice and red, adds a bit if excitement to your day when u see it thinking the world is about to end. But no, just another 4 near the channel islands, Sharkano strikes again! 😉

    • I would be seriously surprised if it did not. Especially in the smaller Viti lake that is highly gasrich. I would say that anyone near Viti when it happened probably died from actute gas poisoning.

      • Having seen photo of “smoke” from rockslide (ash and steam or just dirt-steam ?) posted in at mbl.is – see below – I´d not be surprised there was phreatic reaction. (If that triggered the rock slide, or was triggered by the slide – I do not know – but I saw “the unreast” at Kreppuhraun (followed initial Hekla eruption curve – but did not save it).

        NOTE – The mountain appears having had such event before.

        http://www.mbl.is/frettir/innlent/2014/07/23/vigalegur_mokkur_steig_til_himins/

        Lateral blast like St.Helens … ? *not expert*

        • I could not find any curve at any SIL?
          I would go by brittle sides and ash mounds giving way in normal landslides. The HT visible was most likely a gas release from the excited lake.

          • I saw it at Kreppuhraun SIL (Grjót page), in late evening on 21 July,
            either 22:35 hrs or 23:25 hrs or there about. I checked other staions just in case there was eruption starting, It did not show on other stations, so went to sleep.
            so sorry folks, it whould have been nice having the órói plot that time

            • At Kreppuhrain I would rather suspect that Kverkfjöll is the culprit.

              And speaking about Kverkfjöll, there is a volcano that Irpsit missed in his list of volcanoes.

            • Ok, then there is one very large wolcano the world has missed.
              Even I do not know its name or where it is at 😉
              It has not started erupting.
              *not expert*

            • I meant that I did not see Kverkfjöll in Irpsits list of Icelandic commonly erupting volcanoes.

              He missed the fifth most commonly erupting volcano in Iceland… And that is the very famous Mount Unpronouncable, also known as the Icelandic Surprise volcano that every body goes like… “Where did that come from?” Every tenth eruption in Iceland comes from a volcano nobody knew about, or from a new volcanic feature.

            • Yepp, Mt. Old/New Volcano or New/Old Island Volcano (which ever comes first)!
              That be because Iceland is one big volcano. Much larger than Hekla and Katla combined.
              (Just helping News Anchors composting a new silly headline 😉 )
              *not expert*

  15. Warning: Wild Speculation derived from alternate sources. Posted here mainly for the tongue in cheek humor aspect of it.


    The Apple iPhone’s Siri function is saying that July 27, 2014, will be the “Opening [the] Gates of Hades,” or the Greek term for Hell, leading many to question why.

    If one asks Siri, “What is July 27” or “What is July 27, 2014,” she’ll give the response “It’s Sunday, 27 July 2014 (Opening Gates Of Hades).” It doesn’t appear to work for everyone.

    Several Epoch Times staff members could confirm that Siri delivered the “Hades” response, while another staff member’s phone said July 27 is “Arbor Day” and displayed a Wikipedia page.

    http://www.theepochtimes.com/n3/412857-siri-says-the-opening-gates-of-hades-is-july-27-2014-users-question-why/?photo=2


    Mount Hekla: Iceland’s particularly active volcano developed a reputation as a gateway to Hell in the 12th century, after its 1104 eruption. Benedeit’s 1120 Anglo-Norman poem Voyage of St. Brendan mentions the volcano as the prison of Judas, the apostle who betrayed Jesus. That reputation continued with further eruptions; after the 1341 eruption, there was a report that people saw birds flying amidst the fire—birds, some thought, that must really be swarming souls. Even in more recent times, Hekla has maintained its diabolic status, as some superstitious folk have claimed that it’s a spot where witches meet with the devil.

    http://io9.com/13-places-on-earth-thought-to-be-entrances-to-hell-1441628317



    • Wikimedia Commons

      Not a practitioner of latin, but the text for Hekla sort of translates via Google as “condemned to perpetual fires and horrible snow stones crying vomits

      • LOL – Skálholt and Oddi still are there. Medalland too.
        “SVNDLEN-DINGA FIOR DVNG” stands for “SUNNLENDINGA FJÓRÐUNGUR”
        (the Southern-ers Quart Part) Ambiguity of place names seem to me be this be copied from other maps, but the drafter be not that well versed in Icelandic (Old Nordic) spelling.

  16. Geolurking, this is for you:

    I don’t have better data than GVP for eruptive istory of the Icelandic volcanoes.
    But for the sake of more simple statistics, use this data.

    It’s the estimated frequency of eruptions for each Icelandic volcano.
    I basically calculated for volcanoes like Hekla or Katla, how many often they erupted on average, since settlement. For other volcanoes like Bardarbunga or Askja, I have used a 500 year period of time, since those are remote volcanoes and many older eruptions are probably unaccounted (and they have erupted frequently enough in those 500 years to have a make a solid guess). For others, like Snaefellsjokull, which seldom erupt, I used Holocene data.

    Reykjanes average eruptive frequency: every 71 years
    Krisuvik/Brennisteinfjoll average eruptive frequency: both around every 190 years (but now dormant 700 years, so frequency during first centuries of settlement was estimated to be every 78 years; between their active periods, dormant periods average around 1000 to 1500 years)
    Katla average eruptive frequency: 50 years
    Hekla (and neighbourhood) average eruptive frequency: every 63 years
    Hekla neighbourhood average frequency: every 228 years
    Dead zone average eruptive frequency: every 228 years
    Bardarbunga average eruptive frequency: every 23 years (estimated from last 500 years)
    Grimsvotn average eruptive frequency: every 10 years (estimated from last 500 years)
    Eyjafjallajokull average eruptive frequency: every 286 years
    Oraefajokull average eruptive frequency: every 572 years
    Krafla average eruptive frequency (only 2 episodes in past 500 years): every 250 years (and since Holocene is 4 eruptions, gives a near average of 286 years)
    Snaefellsjokull: roughly every 1000 years (estimated from Holocene history)
    Westman Islands and nearby: every 125 years (roughly estimated from 4 eruptions in 500 years)
    Kverfjoll: every 125 years (same as above)
    Langjokull volcanoes: roughly every 1111 years, estimated from its Holocene history
    Hengill: every 769 years, estimated from Holocene history
    Askja: roughly every 83 years, estimated from major episodes in past 500 years

    I am not going to estimate less studied, remote, highly dormant or irregular volcanoes like Hofsjokull, Theistareykjahraun, Grimsnes and others.

    • I can actually give the probable high score in the last 10 000 years, and the definite high score during settlement.
      1783 list from north to south…
      1. Grimsvötn (Written record)
      2. Háabunga (Written record)
      3. Thordharhyrna (Written record)
      4. Háagöngur (physical evidence)
      5. Geirvörtur (physical evidence)
      6. Eldgigur (physical evidence)
      7. Lakí (Hm, yeah)

      So that would be seven known eruptions in one single year. I would not be surprised if there wasn’t eruptive activity at Loki-Fögrufjöll and Gjálp volcanoes too, but there is not evidence for it in the written records and no physical evidence of it.

    • Well, I appreciate it, but I was hoping to calculate the variance and get a distribution out of it. Doing them as a whole will yield a score for the whole shebang treated as a group instead.

    • This is based off the repose intervals in Irpsit’s listing.

      What is peculiar about that list is that the one sigma interval is 329.593 years. With a Mean of 292, that means that it is just as likely for there to be far less than 292 years between eruptions as it is for it to be up to 621.593 years.

      The red line is read off of the right hand scale. That percentage is the probability for there to have been an eruption of some sort by that interval of time. (bottom scale is years)

      The blue line is just the associated bell curve.

  17. More active volcanoes of Iceland are thus:
    1. Grimsvotn, every 10 years
    2. Bardarbunga, every 23 years
    3. Katla, every 50 years
    4. Hekla: every 63 years
    5. Reykjanes: every 71 years
    6. Askja, every 83 years
    7. Kverfjoll: every 125 years
    8. Westman Islands: every 125 years
    9. Dead zone: every 228 years
    10. Hekla surroundings: every 228 years
    11. Krafla: every 250 years
    12. Eyjafjallajokull: every 286 years

    Others erupt only rarely, every several centuries: Oraejajokull (600 years), Hengill, Krisuvik, Brennisteinfjoll, Langjokull, Snaefellsjokull (1000 years), Theistareykjahraun and Grimsnes (3000 years)…

  18. Now a FUN game:

    If volcanoes would play exact math, then the list of Icelandic eruptions this century, would be like this:

    2015 Katla (it would have erupted in 1968, so let’s make Katla finally erupt next year)
    2016 Reykjanes (it would have erupted in 1997, so let’s make it erupt also within the next few years)
    2019 Bardarbunga (23 years have passed since 1996, and now it does a VEI2-3 somewhere in the region)
    2021 Grimsvotn
    2031 Grimsvotn
    2041 Grimsvotn
    2042 Bardarbunga
    2044 Askja (probably still around VEI2-3)
    2051 Grimsvotn
    2054 Katla and Kverfjoll (bingo! Two in same year!), it makes a very ashy year
    2061 Grimsvotn
    2063 Hekla VEI4 (yes, Hekla went back to its old frequency)
    2065 Bardarbunga
    2071 Grimsvotn
    2081 Grimsvotn
    2085 Reykjanes
    2088 Bardarbunga
    2090 Dead zone rifting episode! Iceland is partially evacuated,
    2091 Grimsvotn
    2098 Westman Islands VEI4 (surprise!)
    2100 Langjokull (another surprise!) a big lava eruption

    Circa 2300 Krisuvik starts frequent eruptions, a new cycle of activity in Reykjanes region; Reykjavik builds dikes against the running lava

    Also Theistareykjahraun and Grimsnes seem slightly “overdue” and so should likely erupt in the next centuries.

    • Ah, forgot to write:2016 Reykjanes (and the Icelandic international airport in Keflakvik is unusable for a few weeks, due to the nearby explosive activity)

      • It does not work that way. Snow clearing equipment can also be used for sweeping runways and aprons of ash, and wind constantly changes, so preatty good chanses could be of it beeing kept open + 30% or more of the time.
        Disruptions, not much actual closure, and these can be predicted in advance.

        • That is unless the US President wants to adversely affect your economy, shutting down flights by having the FAA issue a NOTAMs saying it’s hazardous, then claiming it’s for safety.

          • They do over US based carriers. The way it works is that if a mishap of any sort occurs, the carrier is instantly guilty in US courts and can be sued into oblivion. (a Lawyer’s wet dream)

            A similar thing is in play with USDAO offices. If the state department puts out an alert warning about some area, and a US citizen gets into trouble there, the US’s position is that you were warned, you are on your own. (and apparently, you are on your own even if there is no alert → Tahmooressi)

  19. Obama would be afraid of a typical Grimsvotn eruption in the 1st place. I’m glad Iceland’s volcanoes aren’t friends w/politicions

    • As a joke, I strung old memory chips and chicken bones on a string and shook it at particularly obstinant PCs that were thrown up onto my bench. About half the time it worked. I have pondered shaking that talsman at a wall chart in the vicinity of Wash DC.

      • There was a news feature about him having to leave Ireland early as Grimsvotn started to do it’s dance he flew to London a day earlier than scheduled.

        Eyjafjallajökull is another one of his foes a double whammy

  20. Askja, that could have led to a serious explosive eruption had it have happened.. That is what Hazel Rymer and associates are trying to determine what type of an eruption of type may happen there next.

    • How exactly are they trying to guess that? 🙂 I thought you should at least know the magma composition for that, but that could be a problem since it is fairly underground. :). And I dont think the past eruptions trick would help much with the volcano being pretty much in all the range from 1-5 :). Tho I bet there are sh*itloads of different methods. 🙂 And yea, I have learned over the past months that I know crap, and thats why the experts will figure that out and I am sitting behind my computer in the meantime. 😀

      • With all due respect to Professor Hazel Rymer, but you nailed it DU.

        I think what Hazel is studying is the volume of the available magma, not the type of it. At lest no paper of Hazels that I have read is about the type of magma below surface.

        • And that translates as ordinary (for Iceland) mantle derived basalt, Icelandic andecite (semi-evolved magma), evolved magma (rhyolite), gas and/or water rich magma blasted out explosively (pumice), and finally silicicic xenoliths which in this case is the rock the explosion blasted around.

          I know that KarenZ knows this, I just wanted to make it more clear for any newcomers.

          • “Einn möguleikinn sem jarðvísindamenn velta nú fyrir sér er hvort samspil jarðhitavirkninnar og mikillar úrkomu að undanförnu hafi getað komið berghlaupinu af stað. Mökkurinn sem reis upp þegar berghlaupið varð er einnig ráðgáta, því óvenjulegt er að slíkur mökkur fylgi atburðum af þessu tagi. Ekki er talið útilokað að þar hafi verið um gufusprengingu að ræða.”

            Phreatic “eruption” may have kicked this “Berghlaup” off
            (yup, new Icelandic word – Rockrunning!)

            http://www.ruv.is/frett/askja-fyrir-og-eftir-berghlaupid

  21. I think must of the human race is just lucky to live far from volcanos. But seeing them erupt isn’t the end of the world. Well, not yet. But after seeing this video about the worst eruptions ever, I just shudder.

    • There are quite a few areas of the world that have a rather dense population around volcanoes, or around volcanic risk areas (IE lahar fields).

      Central America & Indonesia are particularly notorious for this, although Indonesia is pretty darn good at threat monitoring and mitigation. I would guess that central America is a pretty likely place to have a large volcanic disaster sometime in the next 500 years or so simply based off the population centers in relation to the nearby volcanoes.

      Based off population density in the vicinity of a volcano, the worst case scenario short of a VEI-8 eruption would be the Laguna Caldera in the Phillipines deciding it wants to wake up again. The Laguna Caldera is a very large caldera complex (10x20km) located right next to Manila. Based off nearby population density, it has the highest volume of inhabitants living within 30km of the volcano in the world with over 7 million residents located nearby. It also has had at least two very large eruptions in the past 50,000 years.

      Read more about it here –
      https://volcanocafe.wordpress.com/2012/11/09/sleeper-fish-a-look-at-the-taal-and-laguna-de-bay-setting/

      With that said, I speculate that Laguna is similar to Long Valley in that it’s slowly dying off as volcanism shifts elsewhere (in this case, towards Taal).

      • If I were a betting man… I’d put my money on Taal rather than Laguna. Taal actually has a quake stack that leads down to the magma genisis realm, Laguna does not.

        … but, as we saw with Fimmvörðuháls, a finger of magma can quickly shoot across to a nearby chamber and kick-start an eruption. Once that happened, Eyjafjallajökull then quickly developed a stack all the way down to the Moho and joined the party.

        If it turns out that Fimmvörðuháls was using Godabunga magma, that will just make the whole thing freaking wild. However I don’t think that Godabunga deflated from all of that and I have no data to back that up.

        • Well, this is why I mentioned that Laguna seems fairly comatose. Taal is pretty dangerous as well, but it’s quite a bit further from Manila (albeit still quite potent).

          7 million people within striking distance of just a VEI-5 eruption is pretty crazy, and Laguna has done much much more than VEI-5 eruptions in it’s past. I would imagine if you were to take that out to the 50km radius (well within range of a VEI-6) you probably get well over 10 million people.

        • Geolurking, Fimmvorduhals was a tiny eruption. VEI1 at best. So it couldn’t deflate Godabunga is any possible way.

          Just as a sidenote, perhaps, what we saw in Katla in 2011 was just a repeat of Fimmvorduhals but under Myrdalsjokull. And all of these systems (Katla, Godabunga, Fimmvorduhals, Eyja, are separated for about 3km of each other) Distances are quite similar between them.

          Something else: the volcanic systems seem to favour E-W oriented fissures, so in theory the rifting favours that magma could escape from one system into another. (yes, I know form the quakes Fimmvorduhals seem independent from both Eyja and Godabunga).

          Last point: maybe a magmatic pulse could have happened and sent magma deep under the MOHO under the 3 or 4 feedtubes: Katla, Godabunga, Fimmvorduhals and Eyjafjallajokull. If Goda and Fimmvorduhals share the same feeding system or not, I don’t know.

          Another interesting thing; I think its rather interesting to see in geological history of 3 very large eruptions in this region, since a long time (thousand of years): these are of course the 2010 eruption of Eyjafjallajokull and the two eruptions at the Westman Islands, 1963 and 1973, almost at the same time in geological timing.

          And this happens, at a time when Katla was long asleep. As if deep down, its magma was channeled somewhere else: to Eyja and Westman Islands.

          Caveat: Just my wild speculation.

          • I can perhaps shed some light on it.
            In this post you I used one function of the IMO sites Myrdals Seismic Page.
            There is another that maps together all quakes in 2D during each year. If one looks at the quakes like that a peculiar patter emerges. Katla and Godabunga remains separate, but during 3 individual years the earthquakes at Godabunga covers Fimmvörduhals. That implies that Godabungas magmatic system reaches all the way over to Fimmvörduhals.
            And I know that Lurking at one time over at Eriks site posted a plot where he had tracked a tendril wandering off from Fimmvörduhals to Eyjafjallajökull… and the rest is history.

            Check for yourselves 🙂

            http://hraun.vedur.is/ja/myr/myr_map.html#img

            • Well… I guess your wording captures the moment far more eloquently than I did 🙂

            • I had sat amazed at how much the plume resembled a blowtorch more than a scoria cone from a distance.
              That had to be some serious pressure.

            • It is where the MAR continues through Katla and goes out into the ocean, so it was most likely tectonic quakes released by the motions inside the volcanic systems.

      • Uhm… I would say that a VEI-6 flank collapse from Popocatepetl complex could outdo that.
        Also a medium sized VEI-6 out of Campi Flegrei could outperform it due to the double impact of the pyroclastic base surge paired with the ensuing tsunami.
        Also Guatemala has the potential for something inordinate when Amatitlan goes VEI-7 the next time around.

        About 2 to 3 billion people live within the immediate strike range of a VEI-6 eruption.

        • You mean million, not billion, right?

          Agreed on Popo, but that flank collapse would need to point directly towards Mexico City or Puebla to come close to what Laguna could do in a normal VEI-5 to 6 eruption.

          • No, I meant 2 to 3 billion people across the globe live within the striking range of volcanoes capable of killing them. ☠☠☠ I should though have written VEI-6 and lower. 🙂

        • I have a question. Why does everyone (media) refer to Campi Flegrei as a supervolcano? Were there actual VEI-8 eruptions there at some point? ツ

          • Nope, but there have been large VEI-7 eruptions. Supervolcano is a superfluous term coined by the media. As such, there isn’t any “real” definition of what one is outside a volcano that has a potential to make big nasty things happen.

            Generally, when used by media, it’s just a means to generate buzz, establish some fear, and provide a bit of hyperbole.

            To be fair, I would personally argue that a large VEI-7 eruption in a populated or metropolitan area such as Naples or Southern Japan would be way more devastating than a small VEI-8 eruption in the remote Andes.

            • I would say that a for Campi Flegrei normal sized VEI-7 would be deadlier than a regular VEI-8 at Yellowstone.
              Campi Flegrei has an average VEI-7 size at around 200 to 400 cubic kilometer volume, and Yellowstone bops out 1000 cubic kilometers on average. But on the other hand Yellowstone is far from large population centers (generaly speaking) and Campi Flegrei is placed at pretty much the worst possible place.

    • Another thing here to ponder – this list is likely extremely inaccurate (not that I fault them for this). The main reason being that we don’t know much about how other past eruptions affected mankind and the proposed death toll.

      What was the death toll for the enormous eruption of Llopango? What about the huge eruption of Rinjani in 1258 which likely was even larger than Tambora? How large was the death toll from Santorini’s enormous eruption? How about the Baekdu / Changbaishan eruption around 950 ad?

      The biggest issue here is that many of these huge eruptions took place in previously unpopulated areas. With globalization and a huge population boom, it’s more likely we’ll see some major volcanic catastrophes in the next 1000 years or so.

  22. Updates on Askja:

    From comments on Jon’s blog, and also from my past hiking in Askja, it is clear that the caldera walls were already very unstable prior to this week event. Apparently the walls were heavily cracked some years ago. They were about to fall down, so anything small could have triggered this landslide.

    Whether the very warm weather at the region in the last days (more than 20ºC) or increased geothermal activity that triggered that, I don’t know. Both are plausible causes.

    Geothermal activity has not been seen to be increased at the surface of Askja, but a bit down something might be happening. Back 2 years ago, we had the caldera lake being ice-free in spite of very cold winter temperatures. At that moment, no one knew exactly what was going on.

    So its equally plausible that increased activity within the walls of the caldera triggered the rockslide.

    The rockslide was a wall of 1.2km wide, It created 4 tsunami waves, up to 75 meters high, as judged by the marks along the walls. When it happened at midnight, a dust plume rose above Askja some few hundred meters high. A tourist photographed it and the picture was on the Icelandic news.

    I don’t think it was smoke. Any huge rockslide would certainly move a lot of material into the air.

    Anyways, this was seems similar to the event that seemed to have happened in Kverfjoll lastyear, and also to a similar event in Hofsjokull I guess it was last year. In both cases, a phreatic explosion possibly happened, in Hofsjokull the river was smelling sulphur, ash was observed in the glacier but no quake detected (amazing no?. In Kverfjoll same thing; no quake (but there was a strong swarm some time before) but the guys at the glaciar hut there heard the big phreatic explosion.

    This shows how sudden these “small” events can happen, without the need of any earthquake prior, tremor, or anything else. They just occur out of the blue. Obviously they aren’t eruptions, just surface events by play of water, steam and unstable rock. Well, maybe some small shallow pocket of magma.

    It also reminds my friends when they hiked in 2012 to Hekla and heard a big explosion-sound at its top and everything shaked. No quake was ever detected but something surely happened there.

    Quite impressive these things! And quite interesting that all of these do not show anything in quakes or tremor.

  23. Someone mentioned a Phreatic eruption in as an possible explanation for the Askja slide above. Here’s a video I took at Askja in 2011, there was steam rising from the area of the slip even back then (from about 10 secs in), so I presume the area has been geothermically active for a long time.

    Not presenting this as proof of a phreatic eruption!

    • Thank you for the video.
      The steam is from a fairly old hydrothermal feature. It’s activity increased back in 2011 and might be a part of the solution to why the lake has remained Ice free for the last two winters.

      One should remember two things about Askja. The first is that the walls of the inner caldera are very steep and mostly made up out of ash and debris from the 1875 blast out of Viti. And the are around Viti is very severely fractured. So this was neither the first, nor will it be the last time a berghlaup happens there.

      Personally I do not think a phreatic detonation occured, but I do not rule it out completely though. Nothing an Icelandic volcano does would surprise me.

      Impressive video of an impressive landscape!

    • Beautiful video! Indeed the hydrothermal background could explain the vulnerability of the slopes and, of course, if magma lies behind this activity a phreatic event can’t be ruled out.
      Thank you for posting!

  24. Don’t have much time, but don’t want to completely dissapear / stay away (again), so just a little comment to say the talk that’s going on and especially the fact that Katla/Bardarbunga is giving signs is just soooo “cool”…
    Have a nice Friday!

    • Interesting, Nishinoshima now seems to have both an Hawai’ian style of effusion combined with vulcanian detonations from the main crater.
      Nishinoshima is really a candy that never stops giving out new flavours. For me this is the most interesting eruption I have seen or heard of. Quite in a league of its own. Now the only two things left to do is either a lateral flank collaps with a following explosion, or an outright caldera forming event. Otherwise this volcano has done every possible style of eruption. Hm, forgot peleean eruption… At least as far as we know, but on the other hand the plug it extruded and that had blown away between shots could have been peleean. Candy!

  25. Great post, Carl 🙂 And also a belated thanks to Bobbi and dfm for their latest posts too 🙂

    Been a bit busy recently so have only just had the time to read the posts properly.

    • It is the walking trail around the Lake that is closed, not the volcano in and of itself.
      They have decided that it was caused by the melting ice and that it was not volcanic.

      Now, the really interesting part is the volume of rock given as 50 to 60 million cubic meters. That would be an equivalent of a medium sized VEI-3 eruption in regards of shear rock volume that would have been erupted. That is rather a large arse Berghlaup.
      Another way of looking at it, during 20 minutes time half the total volume of what Eyjafjallajökull erupted moved down into that lake.

      • That was obviously an answer to DFM and not Renato Rio… 🙂

        @Renato: Intriguing indeed, sounds like how the NSEC got started. Might this be long avaited EMNSEC opening up? (Even More New South East Crater)?

        • I read an answer from Boris somewhere over FB that this present activity wouldn’t last much longer as to form a new crater, as had been suggested by some regulars. According to him, such events had happened before. It seems that a thermal anomaly was seen at the NSE crater, so it is possible that it may reawaken and the recent vents would cease to exist. But he leaves a caveat that all is possible with Etna. 🙂

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