Posted on by Jón Frímann

Grímsvöt eruption appears to be over

Given the current tremor plot on Icelandic Met Office and with reports it seems that the eruption in Grímsvötn (Grímsfjall volcano) is about to be over for now. It is impossible to know if the eruption is going to resume soon or not. But at the moment this eruption seems to be over as it looks now. If it remains like that has to be seen however.

This drop in the eruption has been confirmed by Icelandic Met Office tremor plots.

Tremor plots as of 07:00 UTC. This tremor plots are from Icelandic Met Office web site. Copyright of this pictures belongs to Icelandic Met Office.

Early news this morning in Iceland reported that steam was only coming from the main crater of Grímsvötn.

Other interesting development is that an earthquakes have started to appear SSE of Grímsfjall volcano (Grímsvötn). It is unclear why earthquake are happening at this location. But dike intrusion at this location is not impossible.

The reason for flight problems in Europe is because of the volcano ash that was ejected into atmosphere in the first days of the eruption. It is going take few days for that volcano ash to disappear from the air. Until that happens, it is going to create problems for air traffic.

Update 1: Even if the eruption appears to be over the tremor is still high. I do not know why that is. It is a question why that is or if this is just break in the eruption or not. Only time is going to tell what happens next.

Update 2: There was an news report this morning that before 02:00 UTC there was an spike in activity in Grímsvötn that did shoot the ash cloud up to 8 km. But that spike did only last for few moments before it was over. Rúv has released video here (Windows Media Player) of the eruption site.

Updated at 07:37 UTC.
Updated at 07:50 UTC.
Updated at 08:33 UTC. Blog post title updated.
Updated at 11:42 UTC.
Updated at 12:23 UTC.

86 Replies to “Grímsvöt eruption appears to be over”

  2. Is it possible that the current EQs are a conseuqence of the magma chamber draining?

  3. Thanks for the great reports all, I have been travelling, but have followed the blog on my mobile phone.

    1. This is interesting. The reports says that there is no eruption ongoing. So this must mean that magma is flowing into the volcano or that it has found a new path in the ground. But has not yet broken out in a new eruption.

      This is an pattern that must be watched.

      2. There is a lot of wind in my webicorders. So that is what I have been recording for the past few days, wind and lot of it.

        Check the wind information web site to see if there is a lot of wind at Hekla or not. It helps when you read the webicorder.

      3. Indeed. I would expect a fissure eruption on the southwest or southeast side of Grimsfjall if there will be one.

        Most apparent increase seems to be at Vatnsfell. Worrysome is that the old Laki fissure is not far from this place.

    2. Couldn’t it be that the now relatively empty magma chamber is rapidly re-filling. I small stop on the eruption could part block the eruption route allowing the magma chamber to start re-filling from deep magma. I would be cautious that the eruption may restart again if their is a high flow of deep magma back into the chamber.

      1. Yes but the strange thing is that Grimsfjall tremors are decreasing at the same time as SIL stations south of the glacier is increasing. Seems that magma has found new pathways. Note that I used plural. SSE of grimsfjall there are earthquakes deep below in a place I have not seen EQ´s up until now. Even further south around the old Laki cones tremors are increasing.

        Is the magma on its way up through several conduits? It would be possible if the report that magma came from a very deep source wouldnt it?

  6. Now there are some EQs out near the Westmann Islands showing on the IMO website. I’ve not seen EQs out in that area before. All seems a little strange this morning! 🙂

  7. New deep quakes SSE of Grimsfjall…

    The patterns seems really strange now…

    1. Yes, and why are the red traces not dropping so much – especially, why is Godabunga not dropping for the red trace? Tremor experts out there – can you explain this – it is probably expected, but is something I wish to learn.

      1. Some months ago, there was an interview with the lady who is responsible for interpreting EQs and she used Godabunga and Mýrdalsjökull as examples – anything shallower than ~4.5 km she interprets as hydrothermal activity after having eliminated the possibilities of a subglacial eruption by referencing electrolytes in the streams. No increase of electrolytes, and it’s hydrothermal. Having followed the IMO site for well over a year, almost every eq in the Godabunga area, and there have been plenty of those, turn out to be hydrothermal in origin.

        Extrapolating this / applying this information to Vatnajökull, it’s obvious that much of the activity over the past months have been hydrothermal. But unlike Godabunga, there are almost daily eqs too deep than can only be explained as tectonic or magmatic. With the rapid emptying caused by this eruption, I wouldn’t be surprised if many of the outlying eqs turn out to be caused by tectonic readjustment rather than magmatic intrusions “all over the shop”.

      2. Addendum:

        Hydrothermal activity causes an increase in tremor, just look at the Godabunga station! IIrc, most of it shows up in the blue, 2-4Hz part of the spectrum.

  8. Tremor measurements from Kalfafell SIL seem to be slowly rising as well.

  9. One thing is certain. There is hardly any wind according to IMO website. So something is causing the widespread tremors.

    1. Working my way through the tremor tables it’s clear that all tremor readings coming from the SIL’s in the Grimsfjall region are now on the increase. Are we seeing the signs of a potential second phase?

      The somewhat strange off shore activity over at the Westmann Islands is also becoming quite interesting! 🙂

      2. Renato my friend, only in the blue. The lower frequencies, red and green, continue their downward trend. And if there’s a trend in depth of these quakes, it’s downwards. Let’s wait and see! If the quakes continue in the same location, show an upward trend and a sharp increase in tremor over all bands, I’ll be jumping up and down in exitement enough to cause a local seismic disturbance. 😉

      3. Thanks, Henrik. Never seen earthquakes in this area, as far as I can recall. But other stations like Fagurholsmyri are showing increase in the green too.

      4. I think 10 earthquakes don’t make an eruption inevitable especially in a place where there never was an eruption 😛 The tremors around grimsfjall are more a sign of a new eruption I think

  12. I found two things odd (about the tremors widespread I think now it’s strange that they are still high around Iceland). But two odd things are those earthquakes east of Laki (might be magma trying to open up a new fissure. This is an area I never saw earthquakes before. So, it might be that a future Grimsvotn eruption will take place as a fissure here.

    Even more strange are those earthquakes in the sea south of Eyrabakki, west from the Westman Islands, and east from Reykanes. They are all grouped around a small area. Could it be a new volcano or fault forming there? Why now, just after Grimsvotn? There was also an increase in earthquakes in Katla. And why is one of anti-spam verification words “BTournm Volcán”. This is so funny and adds to the weirdness!

    ps: I can’t see no plume, no ash cloud in my eastern horizon. Still a bit hazy but the weather seems really much more clear today.

    1. Wouldn’t deep relatively unobstructed flow cause widespread tremor? I huge magma reservior has now been emptied below Grimsvotn giving lots of room and relatively low magma chamber pressure, for the plumbing to be re-filling it from below via conduits which could support harmonic tremor.

      Meanwhile teh relative pressures now could be that magma pressure further South is now lower than under Grimsvotn, so the magma further south has started to move toward Grimsvotn along the many underground fractures in this area. Perhaps even, the fractured rock below Vatnajokull acts a bit like a sponge to molten basalt and if pressure is released from anywhere it slowly oozes across below ground to gradually re-equalise the pressure. That would lower underground further south producing earthquakes – This is not proven theory – just my idea.

      2. Sorry for careless typing.
        Also Correction:- I meant that the pressure below Grimsvotn may be significantly lower than it is further South so magma may be moving from further south towards the emptied bit.
        It also occurred to me that the magma chamber may not be all liquid in a void. It may be a mesh of more solid obstructions and may be big enough to span all that area below all current quakes and not be a void like chamber, but an obstructed mass with liquid basalt between. As it empties liquid basalt may gradually negotiate the obstructions and re-fill the area emptied by the eruption. Flow within the magma chamber may be slow, gradual and highly turbulent due to obstructions.

      3. Maybe we could add some bubbles and steam in that mix of moving fluids too?

      4. The deep magma chamber under Grimsvötn is not emptied, it is something like 200-400 km3 in volume. It has just relieved a little the overpressure. With this pressure release the rate of magma heading upwards slowed, which I think closed some of the conduits. I think, taken the explosiveness of the initial eruption, it ended too soon. There’s more to come, I think.

        This is NOT an expert opinion, but a hunch of a mad physicist.

    2. What earthquakes east of Laki are you reffering to? The ones south of Grimsvötn? They are outside the volcanic system of Grimsvötn so I highly doubt they are a result of or a precursor to a new fissure opening up. The earthquakes are at a great depth which could indicate a deep-nested dyke-formation or just plain stress release to nearby rocks. Please do not go crazy everytime an earthquake occurs within a 40km radius of Laki. In order to start an eruption at Laki, there is so much more needed. Don’t draw any conclusions with facts that are not there.

      When a volcanic eruption has occured, or is occuring, the ground over a large area is stressed and distressed in many ways. This causes phenomena that are not regular, but just part of the huge energy-transfers that we see. So earthquakes do not immediately mean that there is magma on the move at the epicenter of the earthquake.

    3. Earthquake swarms in this area happen. But they are not common. I have seen few times earthquakes in this area before. It is just normal fault earthquakes. Far as I know (and I think everyone else) there is no volcano in this area.

      The area around Grímsfjall might have higher then normal earthquake activity in coming days. Both to adjust to the movement and pressure release from the magma chamber. That might explain the earthquaks south of Grímsfjall. But the GPS data says that the movement was 50 cm to the north, and that is a lot of movement in short time.

      But I continue to be unsure why the high tremor continues in Grímsfjall volcano.

  13. Well, my only other suggestion is that perhaps the initial swarm of big earthquakes at the start may have shaken everywhere enough that underground/under-ice molten water has been disturbed and the tremor is geothermal and will take a while for the water pressures to settle down – but I would not expect that to show over such a wide area. The relatively recent incident at Reykjanes didn’t cause widespread tremor, so I don’t think this latter explaination is likely to be the real answer – experts, do you have ideas about this?

    1. The Krysuvik earthquake swarm was not accompanied by any volcanic tremor. It’s even being disputed if this swarm wasn’t just tectonic in origin.

      1. If that was tectonic, then perhaps shaking up a precariously balanced hydrothermal system would produce widespread tremor and perhaps did.

      2. Hydrothermal systems produce tremor on a limited frequency. (mid or high frequency) In order to have tremor that can be observed throughout the country you need harmonic tremor. That means all frequencies, 0.5-1Hz(red) 1-2Hz(green) and 2-4Hz(blue working in harmony, creating stronger pulses. This harmonic tremor is what we are still currently seeing beneath Grimsvötn, indicating that there’s still magma on the move. (draining? refilling? who knows)

      3. Thanks for that Pieter. Kind thanks for explaining these things and how different things can be distinguished between..

  14. One further thought:-

    Is the MOHO juction really a sudden boundary between molten rock and solid rock – I doubt it. If there is a layer like a sponge between the molten rock and solid rock, if magma gets a route up from there and erupts, it will be a bit like water being sucked out a sponge. As it is sucked out, the water in the rest of the sponge moves across to equalize the water in the sponge. Movement is greatest close to the point where the water gets sucked from and decreases with distance from that point, but does cause some water movement throughout the whole sponge to some extent. Well, an opening to the lower pressure of our atmosphere is the same thing as sucking to higher pressure systems below ground. This eruption from deep – do we know it is even from a magma chamber. Could it have been from the MOHO itself? I bet many rift eruptions are. If it is from the MOHO, and the boundary has this spong like structure I propose, then you would expect tremor to measure across the whole of iceland and adjustment movement to occur in places where it is not normally seen. Experts here – any ideas? I want to learn.

    1. This eruption certainly did not come directly from the asthenosphere. (partially molten part of the mantle) For that we would need to see way more deeper (>20km) earthquakes that indicate an intrusion. Secondly the composition of the magma would be different and that would be recognized. And finally it is known that beneath Grimsvötn lies a shallow (1-2km) ‘magma chamber’ (laccolith) which is the feeder for all central eruptions in Grimsvötn. An intrusion from the mantle takes a lot longer and more energy. This is (most probably) what is happening near Upptyppingar (see link).

      http://www3.hi.is/~heidi/Data/Article-richard/Jakobsdottiretal08.pdf

      1. Thanks for that Pieter. I shall have a good read of that interesting article in detail.

      2. According to the news in Iceland the magma was originated from a very deep source. Jón posted that a few blogposts ago.

        Could this laccolith be “fueled” from an ever deeper source which would change the composition of the magma?

      4. Yes, but the difference is that the magma during Chaitèn eruption travelled fast FROM the magma chamber TO the surface, which is a completely different process.

  15. Also, what type om magma intrudes in which type of magma in the chamber is of importance too. A basaltic intrusion (~1200C) into a chamber of slowly cooling and fractioning andesitic – rhyolitic mush can remobilise it “almost instantly” as happened with the Laacher See eruption 12,000 BP or as at Eyjafjallajökull last year. According to Dr Erik Klemetti, proprietor of the Eruptions blog, it was likely that remaining magma from the 1612 and 1821-3 eruptions was remobilised and erupted, explaining the differences in chemical composition between the Fimvörduhalsi and main eruption magmas. When asked point blank, he said that you could not exclude the possibility of remaining magma from the 920 eruption having been remobilised.

    1. One of the characteristics of Hekla has been a very rapid series of events. I am not sure if inflation is a normal thing at Hekla but last time I think there was only a few hours of seismic activity before it erupted.

      That is one mountain I would never set foot upon..

      1. Ind to be honest there are a few volcanoes which has the potential for eruption in a near future.

        Helka, Katla, Krafla..and so on…

        There has even been speculations that Iceland has been going through a quiet time volcanowise and is now starting to enter a more active period. I believe that within the next decade or so we will see more eruptions.

      2. Krafla? How do you figure? I’d rather say Askja given the latest unrest.
        And these theories about active and inactive cycles in the timescale of decades is doubtfull and (yet) unproven.

      3. The warning time for the eruption in 2000 was around 30 minutes between the first quakes (and the warning) and the eruption itself.

    2. I’ve also read this article earlier this morning.

      IMHO, this article is another contribution to the “ash cloud paranoia” going on in Europe at the moment. Since the eruption of Eyjafjallajokull last year, many people, catalysed by the mass media, are only thinking of flight disruptions. Other things like pyroclastic flows, damage to villages and farmland, flash floodings and so on are more or less ignored. Welcome to the journalism of 21st century! 😉

      Back to the article…whole information is that there have been numerous indications, including a significant change of GPS elevation data since the last eruption,that Hekla is charging for an eruption. Scientists believe it is only a matter of days or weeks (maybe months) to erupt.

      Well, actually you don’t have to be an expert to predict that Hekla is one of the top candidates for the next eruption. Everything else (especially the time frame) is speculation, I think.

      1. To speculate that it will erupt within weeks/months is really pushing it. It might also be quiet for another year or so. It all depens what will happen beneath Hekla. There might be other intrusions forming which would release the “up” pressure.

        There are two words which should never be put in the same sentence and they are “prediction” and “volcano” unless the first word is accompanied with a big “NO”.. 😉

      2. I totally agree with that. Pressure inside a volcano can be gone as fast as it appeared. Especially for Hekla there is absolutely no way to predict an eruption in any way. The only thing we can use are statistics, the 10 year average of the last 30 years. But that’s also hardly any prediction since Hekla had intervals of 110 years without any eruptive activity.

    3. Haha, they state that they found a bulge 20km wide. I believe the whole mountainridge is 20km long indeed, that’s one hell of a bulge.

    1. Nope, actually its raining there. You can see raindrops accumulating on the lens. On the glacier you can have snowfall at any time of the year, since it has its own micro-climate. Large parts of it are also located quite high (up to 2100m).

  19. A question Jón or anyone who knows…

    How come the bands on the tremorcharts are so wide? What does that indicate?
    Example. See the blue (2-4Hz) on GRF SIL station before and after the eruption. Before it is narrower and after (especially now) the band is very wide..

    http://hraun.vedur.is/ja/oroi/grf.gif

    1. There is a lot more going on now then when just the background noise is recorded. But I do not fully understand the question. But I do not know how they configure the tremor plot on Icelandic Met Office web site.

      On my webicorder higher noise levels (volcanic tremor, wind noise) means that the line gets darker and thicker when there is more going on.

      1. Think that he wants to know why the blue (and green) part of the tremor plot look like a very wide/thick line since the eruption stopped, while during the eruption you could clearly see it bounce up and down

  20. Sunday morning when we went close to Vatnajokull to see the eruption, we could see Eyjafjallajokull steaming. It has been steaming on and off for several months. You can see it when the weather is clear above it. But its always a small steam cloud.

    Top candidate for next eruption is clearly Hekla, followed by Katla. This if Grimsvotn does not erupt again.

    Jon, do you think the earthquakes west from Westman Islands are fault-related? Have you seen it before?

    1. Isn´t that an area without faultlines? Or maybe there is an unknown fault there?

      1. What i meant was doenst the faultline go further west than that?

    2. I have seen earthquakes in this area before. This looks just like a intraplate earthquake. They happen in Iceland sometimes. They also happen in the area off the coast. But they are harder to locate due to the distance from the SIL network.

  21. Btw guys thanks for all this talk about volcanoes, really helped me in my A level Geology exam today! So clearly there was a big drop in activity early this morning, but it does appear to be slowly but surely rising up again. Is there a good chance of another eruption from grimsvotn in the near future? I personally think its just a small pause but what do you guys think of it?

  22. re Vatnajokull volcano systems.
    This site is worth revisiting, as it shows that EQ activity at most of them (Grimsvotn, Bordabunga, Hammarinn-Loki etc) have seen much more frequent EQs over the past 5 years compared with 1990-2005. The depth plots show EQs extending down to 20km but the crust mantle boundary here is deeper, approx. 35km. Under Hammarinn in particular there is a hint of linear configurations. Note that there a very few EQs between the volcanos- suggesting to my (inexpert) eye that lateral magma transfer is not happening.
    http://en.vedur.is/media/jar/KSV_eq_locations.pdf

    When looking for new spots of EQ activity in Iceland you can check against the archives. Each year’s EQS are summarised on monthly maps here:
    http://hraun.vedur.is/ja/viku/all/skj2010m.png
    ( tweak the URL for other years).

  23. If you enjoy the prospects of really huge eruptions, VEI 5 or larger, there are only a hanful of volcanoes on Iceland that have been quiet for centuries if not millenia such as Bardarbunga central volcano, Torfajökull, Tindfjallajökull and the volcanoes under Lang- and Hofsjökull, a span of time that seems to be neccessary for these huge eruptions. Örefajökull, well, possibly. Askja can be ruled out as it had a huge eruption as recently as 1875 (VEI 5) and has had as many as eight smaller eruptions since. Other than that, there aren’t many volcanoes on Iceland capable of a substantially greater eruption than the one we have just been fortunate enough to view.

    1. This is purely statistic. There is no long interval needed for a large eruption. Most volcanoes have a caldera forming episode and have multiple collapses within thousand (sometimes even hundred) years. There are volcanoes that are dormant for a long time and return with a cataclysmic eruption (such as supervolcanoes) but it’s not neccesary at all.

      One of many examples:

      Long Island, Papua New Guinee, had 2 VEI 6 eruptions within 380 years
      http://www.volcano.si.edu/world/volcano.cfm?vnum=0501-05=&volpage=erupt

    2. Snæfellsjökull is probably the most likely candiate.
      Öræfajökull also has a history of very large and destructive eruptions.
      (The one in 1362 turned the quite prosperous Litla hérað into Öræfi (waste land)

      1. I highly highly doubt that. Snaefellsjökull has shown zero (and that is really NONE) activity in the last 100 years. Also it didn’t have any large eruptions in the Holocene, because it’s a special location considering the Mid Atlantic ridge. It is seen as a failed rift/fissure breathing it’s last breaths.

  24. True, but as you note yourself it’s 380 years between them. In a geologically very active region where large amounts of (eruptible) magma is formed annually, there is naturally a shorter period between large eruptions. The rule of thumb that “the longer a period of repose, the larger eruption” is but a rule of thumb and not an immutable Law of Nature. A volcano such as Tindfjallajökull, which had a very large eruption 54,500 BP (Thórsmörk Ignimbrite) and over the last 15,000 years or so has only had about a dozen small eruptions, might never erupt again – or if it does, the eruptions might be small and lie thousands of years in the future. That doesn’t change the fact that it’s one of only a handful of Icelandic volcanoes with a known, “certified”, *potential* to produce very large eruptions.

    What I’m trying to say is that none of us are likely to live long enough to see a larger Icelandic eruption than Grímsfjall 2011 – this is “as good as it gets”. I for one am very grateful to have been around to experience Eyjafjallajökull 2010, “the eruption of a lifetime” as someone in the know labelled it, and Grímsfjall 2011.

    1. Well I’m hoping to reach at least the age of 70, so that would be 52 more years, in which statistically the possibility is rather large that either Katla, or maybe even Öraefajökull erupts with most probably a force that is compareable to this eruption or even larger. And there is the always present minor minor possibility of a fissure eruption, chances are rather slim though.

      Personally I don’t really ‘expect’ anything, I’m just going to try to experience every bit of firework at it’s fullest. 🙂

    2. Henrik, you’re counting on history to repeat itself, nothing more. There are also numerous examples where “nice little volcanoes” have unexpectedly turned “big bad asses”, or a new bad or powerful volcano has been born in a relatively short time span.

      The thing is, you can not predict the future behavior of any volcano, not even based on statistics. Statistics will only tell you, what has happened. It will not predict what will happen. You can use statistics to estimate what is likely in the future but that is not a prediction!

  28. Hi Jon,
    I’ve been following your blog since its inception and have found it to be quite informative. I have been watching the tremor graphs as well. Ever since the Grímsvöt eruption began I’ve noticed that the stations near Mýrdalsjökull have been very eratic as well. You you have any ideas about what may be causing this? Thanks.

    1. The reason for this is that Grímsfjall volcano eruption is also being recorded on those SIL station also. The harmonic tremor from this eruption is being seen far and wide in Iceland.

  29. What about Katla/Eldgjá 934, Bardarbunga/Veidivotn 1477 and Grimsvotn/Laki 1783?

    These were some of the largest eruptions in Iceland since settlement, and rank around VEI5 or VEI6, with explosive activity followed by huge amounts of lava released.

    The respose period before these eruptions were:
    Katla-Eldgjá VEI5 in 934 happened only 14 years after the previous VEI4 Katla eruption!
    Grimsvotn-Laki VEI5 in 1783 happened only 9 years after its previous eruption!
    Bardarbunga VEI6 in 1477 happened 67 years after its previous eruption, and 120 years after another fissure eruption.

    I think the longer the repose, larger the eruption, makes sense. Certainly I don’t expect next Hekla eruption to be a VEI5 like the one in 1104 that occurred after 250 years of silence, but Grimsvotn still seems to be capable of releasing a very large eruption in our current days, judging from the history of the volcano. The current VEI4 (almost VEI5) eruption is a living proof. The Laki eruption happened only 9 years after its former eruption.

    Katla and Bardarbunga are the most likely to deliver such catastrophic eruption due to their current very long repose.

    I even think that their next eruption will be almost likely a VEI5 at least.
    But I wouldn’t be surprised if they only delivered a VEI4 eruption. You never know where magma goes.

    1. First of all, it’s a common mistake to assign Laki with a VEI 6/5 because it did emmit that amount of lava, but the eruptions were not explosive enough. It was simply one giant ooze of lava over a long period of time. In order to have a VEI 6/5 a plume higher than 25km is required, and from what we know the plume only went up to 15km. VEI is a very bad scale to measure these events because VEI stands for Volcanic Explosivity Index.
      I do agree that these events consecutively are a proof that large eruptions can occure with small repose time.

      Oh and this eruption is far from VEI5, keep in mind that Eyjafjallajökull hardly was a VEI4 because it did emit 0.25km3 tephra, but the plume only got up to 9km height, where 10km is required for a VEI4. For a VEI5 at least 25km high is required, the tephra amount is not clear yet but I highly doubt that it will exceed 1km3 which is required for a VEI5.

      And again, these are only statistics, repose time does not say anything about the size of the next eruption, it has happened often that a volcano goes dormant for many years and becomes active with only a small eruption. For example: Katla took a 200 year break after the 960 eruption, and returned with only a small VEI0 subglacial eruption, and 27 years later with a VEI3.

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