Debunking Caldera Myths

Post by cbus20122:

Before this post gets read, I would like to note that I am not a scientist or geologist. If any information is inaccurate in this post, I would like to encourage the more scientifically inclined to correct me and inform readers if there are any inaccuracies!

Caldera Volcanoes.. The Mythological Beast of Volcanology

Aniakchak Caldera - Alaska

Image Wikimedia Commons : Aniakchak Caldera – Alaska

If you’ve ever paid attention to volcanoes, there is a good chance you’re familiar with what a caldera is. For those who are new to the terminology, a caldera is a collapse structure that forms when the magma chamber below a volcano empties, leaving the overlying rock to subside into the ground. Calderas are to volcanoes what an atom bomb is to explosives. They’re the largest, most destructive, and rarest variety around, and because of that, they’re incredibly interesting.

Caldera forming eruptions are interesting and notable to scientists and casual observers alike since they’re both rare, and incredibly powerful. In fact, some caldera-forming eruptions can be so powerful, that they’ve been associated with global climate change, and small-scale extinction events. Due to their potentially cataclysmic nature, there is a lot of misinformation and doom & gloom in the press and media.
Chances are, you’ve heard the title “supervolcano”. The term “supervolcano” was coined by the media to describe the largest caldera-forming eruptions on earth. Ever since the inception of the term, it’s been used to describe any massive volcanic eruption, the likes which haven’t been seen in the modern era. So what are some common myths about calderas and supervolcanoes? Read the guide below!

Debunking Myths Associated With Calderas

MythThere Are Only 6-7 Supervolcanoes on Earth

Somewhere along the line, the media decided that there were less than 10 supervolcanoes on earth. This myth is a bit difficult to dispel, because there is no real cutoff between “supervolcano” and “really large caldera” as it’s not a true scientific term.

Campi Flegrei in Italy is frequently described as a supervolcano, yet it’s not even 1/10 the size of Lake Toba. If we were to assume that Campi Flegrei is a proper supervolcano, then that means there are over 100 known supervolcanoes on our planet, and it would be on the lower end of the size spectrum. If we’re defining “supervolcano” by capability of producing a VEI – 8 eruption, then it’s true that there are only a few volcanic systems with this capability.

Myth – All Calderas form from explosive eruptions

While more calderas form as a result of a violent eruption, some caldera systems form from a gradual subsistence. Hawaiian volcanoes have calderas that formed slowly following the gradual effusion of basaltic magma, which caused a gradual drop in the size of the magma chamber. Subsistence calderas form most often in mafic shield volcanoes, which are common in oceanic hotspots such as the Galapagos, or the Hawaiian Islands.

Myth – Volcanoes that have had a violent caldera forming eruption are extremely violent by nature

Caldera forming eruptions are more of a cyclical process then they are indicative of a Volcano’s overall nature. Even extremely violent and active volcanoes such as Krakatoa show that they’ll stay active with small-scale eruptions post-collapse. A caldera-forming event typically happens only after a volcanic system has been “plugged” up for a long enough time, allowing pressure to build and magma to evolve to a degree that it can erupt in a dramatic fashion. For some volcanoes, this takes a very long time, others like Krakatoa can recharge much quicker. Some caldera volcanoes will create multiple massive caldera-forming eruptions. Others will only go massive one time, then they’ll sprout several smaller volcanoes after the initial caldera collapse event.

It’s also important to note that there are different varieties of explosive calderas. Caldera volcanoes formed from andesitic arc-volcanism behave in a much different fashion than Caldera volcanoes that form from basaltic rift-oriented volcanism, which typically erupt effusive basalt eruptions, but can create massive rhyolitic eruptions on rare occasion. These caldera systems are usually indicative of a large heat source (basaltic magma) transforming country rock into Rhyolite (the most explosive variety of magma) which later erupts after being disturbed by a fresh injection of basaltic magma.

Myth – Supervolcanoes Are Formed By Hotspots

The largest caldera systems in the world all have a few things in common, yet being hot spot volcanoes is not a similar trait they share. In fact, Yellowstone is the only supervolcano that is known to be formed in association with a mantle plume (hot spot), whereas most other supervolcanoes are located in subduction arcs. What they do have in common is extremely hot and shallow heat sources, typically produced by continental rifting. Rifting occurs when land pulls apart due to largely tectonic reasons. Rifting lowers underlying pressure and thins the surface, which in turn pulls magma and hot rock closer to the surface. Eventually, these large shallow heat sources melt and evolve country rock (often granite) into our familiar friend Rhyolite. If you accumulate enough Rhyolite, let it evolve for a long enough time, then set it off with a fresh injection of magma, you have the ingredients for a massive eruption.

For Yellowstone, the heat source comes from the mantle plume, instead of a rift-oriented heat source (although it’s likely some rifting is occurring as well).

Google Earth Overlays For Caldera Systems – Calderas Outlined in Green or Red (screenshots)

Ecuador Calderas

Ecuador has quite a few massive caldera systems, with the Chacana caldera being the largest

Kamchatka Calderas

Of the 11 large calderas in Kamchatka, the smallest is still 10 square KM..



137 thoughts on “Debunking Caldera Myths

  1. Fascinating post cbus, many thanks.
    By the way, the tremor is starting to rise on the Etna ECPNZ chart. The upper chart EBELZ is still down but last paroxysm ECPNZ showed a rise first with the other following slightly later. So keep eyes on the charts and web cams today is my advice.

    • OH! 15,000 people at risk must be a major problem for the area! One of the volcanoes I wont be hoping will erupt then. 😦

      • 15,000 people at risk must be a major problem for the area!

        Being “at risk” doesn’t mean that something is definitely going to happen, it just means that there is a non-zero probability of something bad happening.
        FYI, pretty much the whole of Naples is at risk from Vesuvius (around 4million, depending on where you draw the line), and the outskirts of Rome contains the decidedly threatening Colli Albani cladera for another 2-3 million “at risk”.
        Which is not to say there’s no grounds for concern. I’m trying to persuade the wife of the delights of going on holiday to climb Mt Etna (and do some archaeology, diving, sunbathing, eating), and Vesuvius would be on the list too. But nothing would persuade me to actually live nearby.
        (Yes, I am a geologist. Yes, I did consider sea level rise and tsunami hazard (~1% for 30 years living here) when recently moving house. Nowhere is “safe”, witness Chelyabinsk recently, but that’s no reason to not be rational about these things.)

  2. As Andy and Newby mentioned above, it looks like Etnas Tremor is rising again. But the weather is awfull, i cant see anything on the webcams.

  3. Great article cbus!

    I especially enjoy the myth “Volcanoes that have had a violent caldera forming eruption are extremely violent by nature”

    Yes, almost all large caldera volcanoes do have a lot of smaller eruptions in between the big ones. Magma is accumulating under them, with each passing small eruption, until a very large eruption occurs.

    Most likely next caldera event is going to be one volcano no one waits (because Camp Flegrei, Yellowstone, Toba, etc), all of these are not “ready” for a super-eruption yet.

    Just picture Askja eruption of 1875 in Iceland, or Oraefajokull eruption in 1362. No one expected such dormant volcanoes to explode powerfully. Askja was a rathr unknown volcano until 1875. After that all its eruptions were tiny in comparison. Oraefajokull is still ignored nowadays but it had the strongest eruption in Iceland since the settlement, even larger than Askja.

    The quiet ones are often the most dangerous ones.

  4. Perfectly fine article, cbus ; nothing of significance that I’d consider “wrong”, but there’s always lots of uncertainty in the Earth Sciences. Mostly you seem to be “tilting at journalism”, which is fine to keep them on course, but they are not known for scientific rigour mostly anyway.

    • I’m very anti-sensationalist, but I do feel that writing non-scientific articles affords the writer to speculate more. It just needs to be kept in reason. In that sense, It’s definitely accurate that I’m more into the “Journalism” camp than the scientific journal camp.

      I took a few geology classes when I was in college, and have been fascinated by the more dramatic aspects of our planet ever since.

  5. Bunch of small but deep quakes near Vatnajokull all of a sudden.
    27.02.2013 15:00:10 64.839 -17.319 19.6 km 0.8 99.0 7.2 km SSW of Trölladyngja
    27.02.2013 14:59:58 64.902 -17.318 15.5 km 0.7 99.0 3.3 km W of Trölladyngja
    27.02.2013 14:57:12 64.850 -17.268 16.1 km 1.4 99.0 5.3 km S of Trölladyngja
    27.02.2013 14:57:05 64.806 -17.244 15.2 km 1.3 99.0 3.3 km NNW of Kistufell
    27.02.2013 14:56:43 64.845 -17.251 14.8 km 1.1 99.0 5.7 km S of Trölladyngja
    27.02.2013 10:45:12 64.746 -18.117 25.2 km 1.1 99.0 2.9 km NW of Nýidalur

  6. Thanks for sending in the article cbus, there were a couple of nice new things in it; I liked it. Would be interesting to see a world map with all known calderas that have produced, say, VEI7 or VEI8.

    I think you mentioned a Google earth overlay before, do you have it somewhere?

    • Yeah, I have it saved on my computer, although I do not have any means to upload it / store it. Anybody know somewhere I can upload it so that it can be downloaded?

      • I would have recommended Megaupload but that was in a different era 🙂

        Perhaps something like Dropbox, Gdrive or something, where you can generate a publicly accessible link. WordPress does not allow it unfortunately…

  7. I’ve often noticed that when a volcano in Vatnajökull has an earthquake. Many other volcanoes have one too. Maybe just one or two, but it’s a pattern that I’ve been noticing more and more. I’ve always imagined that the whole mantle plume under Iceland, and there is a tiny influx of magma into all regularly active volcanoes (in volcanic terms) such as Katla, Grimsvötn, Bardarbunga, Askja etc… causing them to hiccup.

    When I load the IMO page on my computer, the only part of the map visible is the North of Iceland, extending down to the northern tip of Vatnajokull; and if there has been no quakes in this area, I assume the same for the rest (and vice versa), and usually I am right.

    Listen to me, talking nonsense. 😉

    • Reply to Sam: Earthquakes in Vatnajokull in several volcanoes at once:

      Exactly. This is a pattern I also observed, and all the today’s earthquakes were deep. So I also strongly think tthat this was caused by a magmatic pulse of the plume. But I have no idea about the dynamics of those pulses. I also can tell you that being a very ductile and hot lower crust, it takes big energetic events to cause significant earthquake swarms.

      I notice that many times earthquakes happen at Hamarinn, Kverfjoll, Tungnafell and Askja at same time. So probably magma injects under them at same time.

      For instance, in 1860 Grimsvotn erupted, then in 1861 there was a large fissure eruption in Bardarbunga. Within just a decade, another very large eruption happened: Askja in 1874-1875. This was proceeded by two eruptions in Vatnajokull in 1872 and in 1873. So I guess there was a large injection of magma under the whole Vatnajokull prior to 1860, which resulted in all these large eruptions.

      Same thing in early 1700s. First several small eruptions of Grimsvotn and an eruption in Kverfjoll in 1710. Then, the 1720s brought a “party” to Iceland. 1721 Katla, 1724 long eruption of Krafla starts for five years. 1725 Hekla and Vatnajokull join Krafla. 1726 Vatnajokull again (probably Grimsvotn). 1727 Oraefajokull (also in Vatnajokull). And 1729 Kverfjoll.

      So, many neighbouring volcanoes; all erupting withina short period of time. This has happened several times in Icelandic history. And this will be part of a post I want to write.

    • This is just a first shot towards analyzing this interesting observation. Certainly this has been studied extensively and I just have not read it. 😉

      A histogram of time intervals (counting in 1 min bins) between all Iceland earthquakes (Jan 1995 to Dec 2012) reveals an apparent double exponential function.

      My interpretation is that most earthquakes happen very shortly after one another (“swarm”) with an exponential decay of tau2 = 1.2 min. “tau” means that at 1.2 min the earthquake count sinks to about 33% (be aware that the time resolution is only 1 min, so this might be complete nonsense). Then there is another mechanism with a larger decay time (tau1 = 15.8 min). This is for the whole listi database without considering location.

      Your question would be, e.g., is an earthquake frequency above average in northern Iceland positively correlated with a high frequency in the south. I´ll ruminate on how to compute this but am quite sure that geolurking already has a plot in his drawer 😉

      • I don’t really have anything in my drawers that I feel comfortable with whipping out in public. (people get arrested doing that) But I can say that one project that I have been toying around with is applying the Guttenberg-Ricter formulas to the longer term seismic activity for a rectangular block in the Northern zone to see if there is a detectable increase or decrease in quake activity. (or those crafty graboids). Short of that, looking at the power dissipation for the two regions on a per hectare dissapation rate could be illuminating, and no one would come by and arrest anyone for indecent exposure. 😀

        • Oh yeah, about the tesseract. I used Eureqa’s Formulize and dropped the two columns into it, set the variable to look for and turned it loose for a few minutes.

          It can churn through several thousand checks in just a few minutes, trying to find a formula that describes the relationship of the entered data.

          If you run it standalone on your PC, it’s free. I have a quad core system so it’s pretty spiffy in looking through the calculations. It uses all four cores. In the results, the formula is almost in Excel format. Usually it only needs to have the correct variable names put in and you can then use it to do other more predictive sort of things. I have one data-set that I have been occasionally processing that looks at the sun-spot number over time. If what the program is saying is correct, expect the sun-spots to take a hard dive.

          If you opt for the cloud or private server versions, you can quickly break the bank of a standard hobbyist. (in other words, they are very proud of their program)

          @#$ distractions. Another story. While I was a volunteer Fire Fighter, we used to joke back and forth about how hungry the wrecker drivers were. You could tell by how much effort they put into dragging a wrecked vehicle out of the ditch. Some would give up and bring in a larger wrecker, other’s would re-position and try over and over to get the vehicle back up on the roadway. By far the most entertaining one was a truck lodged up in a tree. It had left the overpass and gotten stuck there about 20 feet up in the air. The driver was the one who called in the accident, he had shimmied down the hoses dangling out of the back of the truck and walked down the rail road tracks to a store. He had to use a pole to attach the tow hooks to the axle. I think it did more damage hitting the ground than it did getting up into the tree.

          We stood around watching the show, ready to put it out if it caught fire.

          • I worked it out (with help from the second video) by noting that a cube is 2 squares joined by 4 more edges, (2×4) + 4=12. a hypercube is 4 squares each joined to every other with 4 edges giving us 8 cubes, (4×4)+12+8+4= 40, the next level is 8 squares (8×4)+28+24+20+16+12+8+4=144, then 16 squares=544, after that I had a pattern I could work up with excel…
            Got to 2100000 edges and 9 dimensions beyond ours before giving up 🙂

  8. Nice post 😀

    The only real addition I can make, is to point out that much like sinkholes, Calderas are collapse structures. The principle formation mechanism is likely the weight of the lid (the future floor) overcoming the sheer strength of the rock. With a sinkhole, the cavity is made by water dissolving the rock, with a caldera, by the emptying of the chamber. The strength and mass of the overlying rock will govern how it forms… and you have to remember, damage to the rock from a swelling chamber has to be taken into account. I have been musing on this most of the day, but have literally no time to properly look into it.

    Just yesterday, I was given tasking that would have required that I average 265 kph (165 mph) to meet the scheduling requirements. Two problems with that… 1) My truck isn’t up to it. 2) The highway patrol may have a few issues with it. Not to mention the several municipalities that you have to pass through along the way. Then, there is the safety issue. A paycheck doesn’t do me any good if I’m splattered along 400 feet of roadway. I told them the I would do what I could, but that appointment is not going to be made with those specifications. Everyone should learn how to do time-distance calculations and not be afraid to throw the B/S flag when presented with an impossible or quite dangerous tasking. Along those same lines. Chaff Clouds are your friend. A chaff cloud is a decoy that is launched to give an inbound missile seeker something to look at. They are reflective at the frequencies that the missile radar operates at, and once the missile has a lock on it, it quit looking for something else to kill. Like it or not, autonomous “robots” already exist. They have been around in the missile industry for years. All they want to do, is find something shiny, and kill it. (actually, just to fly into it, the fusing circuits do the rest) Think “moth-flame” Many of the missiles are quite intelligent. But when you have radar seekers looking for you, chaff is your friend. You want a bigger juicer target than yourself. This is the same logic of not having to run faster than a charging lion… just faster than the guy next to you.

    So.. when Mr. Sports car rolls up on your arse, let him pass. He’s the chaff cloud. Ready made. Let him do his thing. Sit back and enjoy the show.

    And another thing. If you drive a flashy car, expect to be looked at. Thats why you got it right? I stick with neutral colors. I don’t like to be noticed. (that’s the thing… whether it’s a missile, or a police officer.) Also, though I do push the limit, I like to be close enough to the posted speed that I can get back down to it in short order with out compressing the front springs or illuminating my brake lights. Those are two more indicators that state that you should have closer attention paid to you.

    And above all… drive according to the road conditions. Idjits are everywhere. If traffic is tight, expect them to dart out of a side street, and expect them to change lanes for no reason what so ever. Be nice. If you are lucky, you can see road karma get them in just a few hundred feet. (faster lane comes to an inexplicable halt)

    Enough of that. The last time I gave driving advice I hit a telephone pole. (at 5 mph) {It was very dark brown, it was dusk, and it was raining pretty good. I still think it should have had markers on it seeing it was in the paved entranceway of a gas station}

    Calderas…. if you take the long axis, and divide that by 2, and then do the same for the short axis, you can calculate the ellipsoidal area. A= a x b x π.

    For example, a 10 by 16 km ellipse has an area of about 125.5 km² (5 x 8 x π). Looking at several published eruptive volumes and the size of the caldera that they came out of, I get this relationship.

    Volume = 10^(1.351 + 0.02101 x Ellipsoidal Area)

    Correlation coefficient is 0.971774743886

    It’s not hard and fast, but it gives you a ball-park figure. Its also relatively important that you remember that since calderas are collapse structures, the magma chamber may have gone through several eruptive cycles before the roof was too unstable to hold itself up. In other words, just because the formula gives you a honkin big number, that volume may have been spread over several thousand years.

    And, I was wrong, not a nice post, it’s a Great Post!

    The formula is a generic fit to data derived from several published works by Self, Aramaki, Hunter, Ablay, Hildreth, Beresford, Leybourne, Tibaldi, Vezzoli, Ferriz, Aguirre-Dfaz, Katsui et al, Katsui et al, STEVEN, Greene.

    Magma volume, volatile emissions, and stratospheric aerosols from the 1815 eruption of Tambora
    Global Volcanism Program – National Museum of Natural History at the Smithsonian Institution
    Formation of the Aira Caldera, Southern Kyushu, ∼22,000 Years Ago
    Intracrustal Controls on the Coexistence of Tholeiitic and Calc-alkaline Magma Series at Aso Volcano, SW Japan
    Basanite–Phonolite Lineages of the Teide–Pico Viejo Volcanic Complex, Tenerife, Canary Islands
    Volcanological perspectives on Long Valley, Mammoth Mountain, and Mono Craters: several contiguous but discrete systems
    Kaingaroa Ignimbrite, Taupo Volcanic Zone, New Zealand: Evidence for asymmetric caldera subsidence of the Reporoa Caldera
    Submarine magmatic-hydrothermal systems at the Monowai Volcanic Centre, Kermadec Arc
    The space problem of caldera resurgence: an example from Ischia Island, Italy

    Eruption rates and compositional trends at Los Humeros Volcanic Center, Puebla, Mexico
    “Evolution and Magmatic History of Some Krakatoan Calderas
    in Hokkaido, Japan”
    The ~20 km wide Bolsena Caldera, Italy, formed between 0.6-0.2 Ma.
    Three Creeks Caldera, Southern Pavant Range, Utah
    GVP entry on Rabaul

    • & presumably the magma chamber roof and surrounding area could have taken their time to sink, if the net emptying of the magma chamber was slow enough 😕

      • Don’t call me Shirley… 😀

        Not getting into specifics…. but when a head of state (generically speaking, pick one) has been reported as having died… four separate times last year, and then is reported as having died again this year, shouldn’t the possibility of them actually being a Zombie be taken into consideration?

        Continuing along that thought… if a head of state is a zombie, and is then dispatched in Zombie elimination style, is that an assassination? One would think that they would have to be alive in order to fit the definition of assassination, if they are already not alive… that sort of negates it right?

        Note to the watchers. This is just a hypothetical rumination on how the zombie meme would fit into such a scenario. If you think that this is a bona-fide threat at your employer, get a life. It’s not.

        • Decades ago, the first couple Saturday Night Live seasons used to have a running joke about Generalissimo Fransisco Franco still being dead. Reminds me of that long forgotten humor. Cheers –

  9. True Story. I was walking past the old Courthouse and this gut was bellowing about being cold and hungry at people passing by, then following it up with “and you call yourself an American”

    At the time, I’m lugging along two hefty batteries after having replaced them in a UPS.

    The guy looks over at me then takes off. “Odd” I thought to myself. Surely it can’t be because I may have paid him to help me lug those batteries right?

  10. I think a particularly relevant & possibly advanced topic related to this would be assessing risk for a volcano to have a caldera collapse event when it has yet to have an event of that nature. As it’s always been said “the volcano that you least expect is the most at risk”. This is very true, since caldera events typically are “go big or go home” types of events. But the *first* caldera event seems all sorts of crazy to me..

    I’ve always found it interesting to think about the nature of a massive caldera. In an extreme (the largest example we currently have) example, lets take lake Toba.

    Toba has had at least 3 supervolcanic eruptions in it’s histroy. So lets say you were a bystander sitting by on the hills around toba before it’s first massive eruption… what the &*^% would the first Toba Caldera eruption look like? The first hypothetical eruption of Toba could have been the equivalent of the entire State of Rhode Island deciding to simultaneously blow up, then collapse into the ground. If you can imagine Rhode Island randomly deciding to blow up and destroy itself, then you sir are crazy, but that’s pretty similar to what would happen at the “first” supervolcanic event of a massive rhyolitic caldera.

    This is what boggles my mind, and makes me so fascinated by any type of caldera volcanism. Even if that’s the most extreme example, the scale of something like that is truly mindblowing, and otherworldly. Would there be any way to predict a new site like this forming? I recognize this is the forefront of research, and very advanced, but it’s still highly interesting nonetheless.

  11. Well, RadioStudio7 viewe is cloudy, EtnaWalk is cloudy, the Montagnola view at looks clear. I have turned on my script for the thermal and normal view, however it only updates every 3 minutes, I’ll share anything if it looks interesting

    • Correction: RadioStudio camera7 is cloudy, The 1st camera is ok, so have turned my script on for that as updates every min:)

  12. Well the tremor has subsided, it looks like a blast of ash here is waht i captured that was interesting:

    RadioStudio 7 must have got too busy as I could not capture anything past 10:50am

    etnaWalk was too cloudy

    INGV was ok it only updates at 3 mins, but atleast i cuaght it

  13. Hmm actuall, it seems i did manage to capture the radioStudio 7, just that my convert scritp is not grabing the jpegs after 11am

    It looks like the crate got blasted away

  14. Ok i fixed up RadioStudio7, the converstion script falls over if a jpeg image is empty (0 in size), which probabaly happens if the webcam is busy.

    Here is the video, My favourite by far..the camera gets blown off its original view, but that appears to be lucky for as as we seem to have caught a lava flow at the end

  15. Is anyone else having problems seeing the Mila cams in Iceland?…….
    <<<<< Potters off mumbling about Mila cams being perfectly OK until they started messing wth the new web page layout… If it aint broke don't fix it!!!!!

    • eh, some are offline, Hekla cam is ok, but weather is cloudy and drizzle anyways…
      Hamarinn was not in action this morning, rather Laki (upstream area under the Glacier) and three quakes in Askja proper for good measure. “The Zero hour” is getting nearer, shure of it, expext Mrs. Hekla be first…, I think it will show quakes very soon!
      *not expert*

      • The North West area of Vatnajokull Is particularly interesting at the moment. Today there are what I believe to be harmonic tremors . I do think there is magma movement beneath the area. Dyke intrusions?

        I watch Hekla but as I can miss Etna with all the run ups and warnings I bet I miss the start of Hekla’s next show. 😀
        For any people who have recently joined us, Hekla’s modus operandi is a couple of earthquakes, not necessarily large, right under the mountain… then very soon after the eruption starts… last time was within the hour. So do not go walking on Hekla, her magma chamber is believed to be full and if you are on the top and feel a quake or two you are likely to be fried before you can get half way back down!

  16. Although Germany did not have these floods that Britain was suffering from, we had the cloudiest winter since over 60 years, only two-thirds of the average sunshine. This is just a glimpse on what a volcanic winter must be, but I´m about to become a migratory bird already.

    • Hi GHDrake, it has been linked by barabara from germany, but it’s an interesting video… Thanks, and welcome, I don’t think I’ve seen you here before 🙂
      Also @ all, Claude G (see his link in the sidebar above) has suggested that etna is having a summit eruption now; rather than futher paroxysms…
      Is showing what looks like a goodly lava flow…

  17. Diana, it acttually raises my interest more than the ocasional swarm. This is not at Hamarinn but almost at Thordarhyrna. And let us remember that Thordarhyrna is just next door to Laki, and it is at this spot where the chamber that erupted Laki is located.

    Usually the mechanisms is this: Grimsvotn can feed eruptions at Thordarhyrna;and Thordarhyrna can feed eruptions at Laki. Often eruptions are moderate size, VEI2 to 4, but only rarely of the size of Laki. Last eruptions there were in 1887, 1903 and 1910. So its about time to expect a medium size explosive and lava eruption there.

    Its also worth watching especially after the last eruption of Grimsvotn where tremor persisted long after the eruption was finished, and that points to the system being filled with new fresh magma, which probably intruded into the southwest towards Thordarhyrna and Laki. But I do not fear any eruption from Laki, just Thordarhyrna.

    Thordarhyrna by the way (as is Laki) is considered a part of Grimsvotn.

    And to complicate things further, Thordarhyrna is connected by a fault to Hamarinn. So like Gjálp (between Grimsvotn and Bardarbunga), this fault, where earthquakes occurred today, could mark a movement of magma from Hamarinn towards Thordarhyrna or vice-versa (less likely)

    Worth watching since these last days there were many deep quakes under Bardarbunga and Grimsvotn and more shallow ones under Thordarhyrna. Just like a fissural intrusion would be predicted to occur.

    • Thank you for this informationIirpsit. What I have been watching now makes sense. It’s difficult to keep in mind what is under the ice cap
      Certainly the whole area of North West Vatnajokull seems to be brewing something. Wether it is just magma intrusions or wether it is pre- eruption wobbles is something that will be seen sooner or later..

  18. Hello Cbus,
    Thank you for your very informative article,
    when you consider that I had known a year ago what to do with the word Caldera … 🙂
    and today I read with pleasure your contribution
    Thank you for that – and also to the other experts in this forum 🙂 for their interesting contributions and comments
    I could learn a lot here already

    • Dunno :hmmm: It hasn’t been moving fast and I have been watching: but somethng is moving:

      and the bright spots on the periphery of the current action have been there all along (last few hours…)

  19. Dr Boris mentioned on eruptions that also after the paroxysm lava did not stop flowing for ( i think it was) up to two days.

    • What a shame you got into a spin Jamie. Never mind, it’s good Jon came clean over the mystery tremors. 😀

        • Oh WOW! I have heard about invasions of waxwings to Scotland but I have never seen one. They look pretty birds.

          • Ah, waxwings… I came out of work to see a whole bunch of them (I’m estimating about 30-50) in a tree a few weeks back. And we had the opportunity a couple of months ago to examine one up close when we (well actually our cat) found a sadly deceased one in our garden. I think they’re probably still around and in previous years we’ve had them in our area well into March, so if you’re in the northwest of england… keep looking out for them. You might just get to see one.

        • We get hit by mainly Cedar Waxwings here we are on a major flyway in NE Oregon for them Boehemians show up too. We’ll have hundreds strip the rose hips and berries that the other birds haven’t taken…
          Then they move on….

  20. “If we’re defining “supervolcano” by capability of producing a VEI – 8 eruption, then it’s true that there are only a few volcanic systems with this capability.”

    To which I would add ‘that we know about’.

    I think it highly likely that the next VEI8 will come from a presently unknown ‘sleeper’. The number may be higher than is believed. But we don’t know enough about VEI8s to be sure, of course.

    OK OK I’m hedging my bets; a sleeper, or Taupo 🙂


  21. Could it be a coincidence that there appears to be a diagonal line of earthquakes running North East across Vatnajokull?

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