Earthquake swarms in Krýsuvík volcano, Tjörnes Fracture Zone and SPAR fracture zone (Kolbeinsey Ridge)

In the last few days there has been good earthquake activity in TFZ (Tjörnes Fracture Zone). The largest earthquakes have been up to ML3.0 in size. But this earthquakes swarm have mostly been small and lasted for a short time.

Last night a earthquake swarm started in Krýsuvík volcano. This was just a normal tectonic earthquake swarm that normally takes place in this area on regular basic. From what I can tell. But it is impossible to know if this earthquake swarm was created by magma movement or not.

The earthquake swarm as it did appear on my Heklubyggð geophone. This picture is released under Creative Common Licence, see the licence page for more details.

The location of the earthquake swarm. Copyright of this picture belongs to the Icelandic Met Office.

This earthquake swarm took place in and close to a lake called Kleifarvatn. The largest earthquake in this earthquake swarm was a ML2.9 (automatic size). Currently the earthquake swarm is ongoing. But it has slowed a lot down since it started last night. At the moment, it looks like this earthquake swarm in Krýsuvík volcano is over for now.

Some earthquake activity was also on the south part of the MAR SPAR fracture zone, south and north of Kolbeinsey Island. The largest earthquake there was a ML3.0 (automatic data). Earthquakes this area happen often also. Like on the Tjörnes Fracture Zone.

Blog post updated at 23:38 UTC.
Blog post updated at 22:06 UTC on 16. August 2011. Fixed a error in it.

120 Replies to “Earthquake swarms in Krýsuvík volcano, Tjörnes Fracture Zone and SPAR fracture zone (Kolbeinsey Ridge)”

  1. So, I feel that I am getting a decent grip on volcanoes, but plate tectonics are still a bit vague in my mind. In millions of years time, with this being a “fracture zone,” will Iceland be split into two different islands? Or will the volcanoes make new land in between so that Iceland grows bigger?

    There was an interesting programme on the BBC a few weeks back, featuring Richard Hammond swimming between the American and European (Eurasian?) plates somewhere in Iceland. The programme was equally as pretty as it was vague on scientific facts.

    1. This is a very hard question to answer, and at least I would have to write a long answer. I will try tomorrow after sleeping a bit.
      Short answer, I do not think anyone can say how things will look in Iceland in a million years. We are not there scientifically yet to give a good answer since there are still to many unknown factors regarding the interaction between the hotspot and and the north atlantic rift (which is the mother of all rift zones).
      The thing with geological timespans is that things move so slowly, for instance Iceland will only have grown 25 km out if rifting in that time, and at the same time the hotspot will have moved with another 25 km. So there would probably be a new eastern line of active volcanos on the rim of todays Iceland. What effects those things will make I do not think anyone has an answer for.
      Personally I would say it is a too short time for anything as major as a cracking of the island. But… Who know?

      1. I’ve also seen the BBC program. They said Iceland would split in 2 parts. Because the MAR is filled with oceanic crust and not continental crust. Therefore it’s a matter of “time” untill the sea fills the MAR crossing through Iceland.


      2. That is not really correct of them to say so. The MAR is a rift, where NEW oceanic crust is produced due to magmatic processes. That oceanic crust can after geological times and through other plate tectonic processes become continental crust. There is no difference between oceanic and continental crust per se.

        The Big issue is that the theoretisized hotspots has hauled Iceland 45 metres up compared to normal earth height. This is proven through satellite magnetogravitetic imagery of the entire planet. And regarding hotspot theoyy, this proves that something like that is in existance, but the actual process is not proven.

  2. Iceland has been growing for at least the last 22 million years by a process of volcanic accretion, due to its position on the mid-Atlantic ridge and the position of a conjectured “hot spot”. There is no good evidence to suggest that this process will not continue for some millions of years into the future.

    1. Correct, but what evidence says that the production of magma is enough to fill the gap also in the (geological) future?!

      1. Correct again. But that is the problem with geological times, we simply do not understand the processes well enough to predict well into Deep Future.
        But I think we can with a good bit of certainty say that Iceland will exist within Cathy-time (1 million years).
        In ten million years, who knows? Sadly we wont be around by then to check… 🙂

      2. An observation: Icelandic topography is generally more mountainous in the west and east, than in the central highlands. Based on this, it may be that the magma production is on decrease, and Iceland may indeed divide into to two islands.

  3. Thanks John for your new Post.
    Iceland is, for me, surely one the most interesting geological happenings on the planet.
    New land being created. A country that is expanding.
    So much to be discovered and understood.
    Your posts Jon are so informative as are those of others like Carl and Lurking with his wonderful graphs.
    Where else could I watch plate tectonics at work and be interactive with up to the minute recordings, explanations, volcanic behaviours and all with the added friendliness of the people who post here. Not only that but exquisite streaming cam views of a beautiful country.

  4. The interesting part, to me anyway, is that this swarm was so localised, with a spread of around 1 km in depth and only slightly more on the surface. As you say Jón – “From what I can tell” – by looking at your helicorders, it is very hard to tell whether or not this is tectonic in natoure. It would be very interesting to see a large-scale, three-dimmensional plot of this swarm in case the shape would tell us anything about its nature. If tectonic, it ought to align on, roughly, a line, even if it’s a line inclined from the vertical. If it doesn’t, other interpretations such as quakes around the perimeter of an expanding magma chamber due to fresh intrusion come into play.

    1. I am still having morning coffee so I am pretty stupid still… (Explanation for americans, Swedes are culturally forbidden to have working brains untill the other cup of caffeine rich ultra-strong coffee).
      You meant Krisuvik did you?
      If so, I would love to have a lurking graph now… sniffle… 🙂

      1. I must have Norse blood in me as I dislike English tea and need, as you say, that second cup of coffee.
        I too immediately thought of Lurking’s graphs.
        May I should explore the possibility of finding a suitable program so I could attempt my own.

      2. Well, the thing is that Norwegians dont drink that much coffee… There is a pretty large difference between Norway (mid-coffee users) and Swedes (high coffee users from which the norwegians are descendents of) and Finns (totally different people and language, but used to be the same country as sweden, current world record holders in coffee consumption).
        Since Lurking sadly seems to have gone a-wall I would be happy if someone else started doing the plots. I sadly lack the time for it… Nah, I am too lazy… 🙂

  5. Is the tremors going far up at katla? What is the reason for that? If i’m not wrong, I can see the same kinda rise at hekla too.. Someone like to explain?

  6. Hekla is acting up:
    Tremor spike followed rapidly by a midsized borehole strain transient.

    There has also been a sequentially growing transient over the last few hours between GEL and BUR. This is also midsized, but very constant.

    There has still not been a powerfull enough earthquake (2,5 aboutish) to indicate emediate eruption. Since this is the volcano I have followed the longest and know best I would say that this is another of the “aborted eruptions”, indicative of an upcoming eruption.
    For those of the journalistic profession following this site, I am not a professional volcanologist, and with upcoming eruption at Hekla I mean that it is ready for one, but it might come tomorrow or in ten years time. What I am writing about Hekla is purely my comments on the progression towards a future eruption. There is no signs of an eruption hapening within the next 24 hours.

  7. Hekla update:
    There is a clear spike on the Haukadalar SIL-station, it looks like an earthquake, but it was not detected as such. I think it was to non-localised to be detected as a quake, could have been some other form of shifting, perhaps magmatic. Curious though.

    Jóns Helicorders are picking up something to, not so much that it is alarming, but it started in the morning. Sadly the Heklubyggd helicorder went quit at 12 so it missed the events recorded otherplaces.
    What is, or not, recorded I leave to Jón to comment. It might just be wind noise or something. But it is not terribly windy in the area of interest.

    Caveat: Do not write an alarmist article. These are just two types of signs out of 4 needed. It is just curious and idle speculations.

      1. Yepp, I hope Jón will tell us what it was…
        I will pour a second white russian and sit back and wait for what happens next.
        If Hekla follows suit we will have a mid deep quake between 0,5 and 2 within 48 hours and then back to quiet again. This has happened the year or so…
        I call them the “abortions”…
        I do not think it will be different this time around. To little tremoring for anything else.

    1. That is the milliondollar question…
      Either a small Hekla quake, or a magma gas burp, or someone slamming the door… Hard to say if it is human noise or something moving down below. It is saturday so it could be visitors to the cottage.

      1. Yes… I can not explain it.
        Seems like something is happening all over, but still at low levels. But remind me, isn’t Skrokalda on the Hekla side?

      2. There is something going on in Hamarinn volcano. What I have no idea. But it is growing.

        It might be glacier flood. But that should become clear in the next few hours what is going on there. For the moment I am just waiting.

  8. Well, it should quiet down now. If this abortion behaves as the last sixty or so that has happened the last year, it will be slightly more tremoring, then it will go down, a quake, a tremor spike and then back to be for a couple of weeks. Since the January abortion week with its 56 abortions, they have come one at a time, and all of those solitaries have acted like I described here.

  9. I had problems with my geophones in the last 24 hours due to power issues or some other computer related issues. I am not sure what was the case.

    But that should have all been fixed now.

    There is a lot of human noise in Heklubyggð geophone at the moment.

  10. The increasing tremor at 0.5-1.0 Fz (red plots) at most stations are due to increasing height of the ocean waves caused by strong winds from the low pressure south of Iceland. The energy of the ocean waves turns into seismic waves when reaching the shore. The peak of these seismic waves are usually between 0.15 and 0.5 Hz but still a lot of energy between 0.5 an 1.0 Hz. The red plot in is following the significant waveheights off southern Iceland very well. Strong wind causes increasing tremor at shorter frequencies (blue plot) and is local in origin.

    1. Ingemar, do you think this is what is also happening at Skrokkalda station? I thought it looked a littledifferent to the pattern on other stations at the moment but I’m sure you are correct. 🙂

      1. He is correct for the coastal stations, not the inland ones. Skrokalda is affected by other factors. Even Haukadalur is showing other effects.
        But Ingemar is pointing to one of my favourite pet-peeves, half of the Katla-scares here are related to waves and wind 🙂

    2. Yes, it explains those SIL-stations that are coastal bound. But… They do not influence into the middle of the country.

      If you for instannce look at the Vestmannaeyar SIL you are looking at a SIL that is heavilly hit by Waves, for natural reasons 😉 If you use that one as a baseline against other coastal SILs you see that they match up. So far so good.

      Problem is just that the further inland you go, the more of the energy is “eaten up”. For every doubling of the distance from the ocean-waves, the tremor-wave is divided in strength by 4 on average (different rock, different permeabillity. Rest assured that nothing the ocean does would affect the Skrokalda SIL-station. Take my word for it, it is after all my speciality how energy waves propagate through any media.

      1. Skrokalda would be that spot.
        I did extensive work on this field back in the nineties, for obvious reasons. Yes they travel the distance, but not with enough residual energy to be noticed.
        And since the energy level falls by 4 for every doubling of distance in normal rock…
        Second of all, Skrokalda has a higher increase than Vestmannaeyar, and that is physically impossible to be related to waves.

      2. I am not so sure it is not ocean waves there as well. The seismic waves from ocean waves travel far inland. We had a small magnitude 3 earthquake in SE Sweden that was recorded in Hagfors (south Sweden) and if did not filter out the short periods of the earthquake the seismic waves from the quake could almost not be seen due to the strong long period waves from the sea. That was oceanwaves that hit the west coast of Norway and had travelled through the mountains of southern Norway to Sweden (several hundred kilometers).

      3. First of all, I just checked waves, they are only 2-3 metres right now. And that is normal waves in the ocean. I have seen waves affecting far inland, but they are normally storm waves above 10 metres.
        I cannot comment the Hagfors one since I do not have the wave heights for that event.
        You should also remember that we here in Sweden do not have anything even remotly close to the Icelandic network.
        Swedish small quakes are normally hard to detect due to lack of detection equipment. And you should also remember that the majority of quakes we have are man-made, ie. Mining blasts…

      4. I’ve read that one.
        Yes, but the thing with the deep waves in the north atlantic is that they are normally produced by the Icelandic low, or a hurricane. The Icelandic low is not highly active now, and there has been no hurricane or other storm that could create DOPWs (Deep Oceanic Preassure Waves).
        So for today the coastal stations are influenced just a bit, the rest not at all.
        Please all, I am not saying that waves do not affect at all. I am saying that they DO affect, but mainly coastal or coastal close stations, and it takes mid to large waves.

      5. Actually it’s a factor of 2 maximum! The ocean waves propagate in the base rock as a cylindrical wavefront, not a spherical one. Actually it may be even lower than 2, as the source (waves hitting the coast) is likely more like a plane than a line…

      6. Sorry, mixed numbers too much. You’re correct Carl. For a spherical wave the exponent is 3, i.e. a factor of 8. For a cylindrical wave, the exponent is 2, i.e. a factor of 4. And for a plane wave, it is 1, i.e. a factor of 2 (each one for doubling the distance).

        I should go to take one more cup of coffee…

  11. The red line (0.5 – 1.0 Hz ) on the tremor plot at Rjúpnafell (rju) is rising almost vertically.

  12. Skrokkalda is very far from the sea, would it reach so far, this kind of seismic effect from the waves? And besides, the higher frequencies are also affected.

  13. I believe it is the energy from the ocean waves we can see in Rjúpnafell (rju) as well. The attenuation of long periodic waves is much smaller than of short periodic waves and can therefor travel much longer.

    1. Not as far as Skrokalda.
      Or to be exact, there is no equipment that can detect it at that distance.
      FYI, I built and invented equipment like this for a large part of my work-life. The equipment here is by far less sensitive than for instance the old SOSUS network, which was built on my patents.

  14. And let me debunk the waves.
    Current wave height is only 2-3 metres when hitting the coast. That is not high waves.
    There is quite simply not enough energy in them to affect anything more than coastal stations, and those just a little bit.
    Klick on the map containing Iceland for current wave heights.

    1. I would say the significant waves are between 3 and 4 meters, that means max wave heights between 5 and 7 meters. Late on July 31st the significant wave height off SE Iceland reached 6 meters, that means max waves around 10 meters which also can be seen on the tremor graph og Godabungu.

      1. Average wave height is 2-3 metres, and that gives max wave heights at 3-4.5 metres (ie, a hundreth wave where two wavefronts intersect can only be 50 percent higher than their parent waves, it though contains twice the energy).
        I will though not argue the waves on the 31st since I never checked those. And that is also beside the point. Godabunga is affected by both waves and wind, especially wind… It is also among the most sensitive of the SIL-stations on Iceland. As I said, coastal or close to coastal will be affected.
        Skrokalda on the other hand is ten times as far away from the ocean as Godabunga, and it is still more affected than Godabunga. Do you start to see my point at all?
        Yes waves affect, but it takes more than average waves to do so.

        Ingemar, I do not know if you have ever sailed? I do, and let me tell you that the waves currently in the north atlantic are normal on any day. This is almost as good as it gets around Iceland wavewise.

  15. It can not be wave noise at Skrokalda because, as Renato said, whatever is happening is effecting all frequencies..

    1. Good point, the shorter the frequency, the shorter it permeates. In theory, a very low frequency wave moving at high speed could affect a station very far inland. Tsunami waves for instance do, and they have periodicities of minutes. A tsunami would bash straight through Iceland.

    2. There was something else going on at Skrokkalda then just wind. But it was skewed by the wind noise in this area.

      I did mention this above in a earlier comment about Skrokkalda SIL station.

  16. The river flow level at Jökulsá á Fjöllum is being shown on the IMO site as ‘Very Much Flow’

  17. There is study made in Iceland about the effect of seismic waves generated by wind/sea. . About 10 % of the energy (about 30% amplitude) of the frequency 1 Hz still remains at a distance of 100 km. That equals to an attenuation (Q) factor of about 100. If this is applied at the frequency 0.5 Hz there would be about 35 % of the energy still remains or (about 60 %) of the amplitude. Most of the energy in the 0.5-1.0 Hz range is surely in lower range closer to 0.5 Hz, would guess about 25% of the energy or about 50% of the amplitude still remains at a distance of 100 km.
    Of course I can not be sure that it is pure ocean waves at station (SKR) but some of the rise seen can be related to ocean waves just as can be seean at HVE.

  18. The quake at Katla was at 6.2km!? I do not speculate about 1 earthquake but that does seem a little… unusual? 😀

    1. Because the automatic system decided that it was not an earthquake. The system use various algorithms to remove false readings. Probably it was removed due to time-errors between SIL-stations.

      Nah, it was last weeks Unidentified Flying Sheep who landed 🙂

      Thing with all automatic systems is that they pick up ghost-readings. Just be happy that they filter them out, otherwise we would be drowned in false readings. If you really want to make sure that it is not removed inaccuratly you can handcalculate it. You can find the calculation basis for time-vectoring P & S waves at Wikipedia. Doing it by hand takes about a day, but who knows, you might catch a fault in the calculations.

  19. Yes, I really think something is going on again in Hamarinn. All stations show an increased in tremor but that is the increased wind that started to blow strong this afternoon. But in Skrokkalda, there is something else there on the graph, a small uptick in the middle of the increased tremor, actually noise, from the increased wind.

    We should look mostly at the stations around the volcanoes which have been showing unrest lately, Hekla, Katla and Hamarinn. Because those are the suspects. Of course, most often increase in tremor is due to wind. But if something subtle occurs in one or two stations, then, you try to watch where this activity might be coming from. On this case, there is something happening at Hamarinn, but apparently small.

    1. I have two more we should keap track of…
      Askja is showing unrest. And also Hengill. I know that I am the only one warning about that one, but there are good reasons behind it, magma-infusion at root-base, odd quake patterns from time to time. But I have been wrong before. On the other hand, this would be the most disturbing volcano of them all for Iceland in itself.
      If I had to rank the top ten list in likelyhood of eruption this would be the order.
      1. Hekla
      2. Askja
      3. Hamarinn/Bardarbunga
      4. Katla
      5. Hengill
      6. Krafla
      7. Vestmannaeyar area
      8. Geirfugl area/Reykjaness Ridge
      9. Esjufjöll
      10. Krisuvik

  20. The water temperature at Jökulsá á Fjöllum is being shown on the IMO site as dropping 1.5 degrees in the last 12 hours… this is the coldest its been for many months.

  21. WoW! What a very interesting discussion on the effects of ocean waves inland. I get a bit lost with the details and measurements but I am able to follow the reasoning fairly well.
    I too have wondered about Skkokalda. Often there are anomalies there, it seems a “Strange” place!
    I have always allowed for energy noise of running water there. The run off of water from the surrounding glaciers must get very rapid and at time heavy during the summer months not including sudden rushes from thermal activity beneath Vatnsjokull. I would be surprised that normal ocean waves could affect this SIL station. I could understand more in Autumn and Winter when there are heavy seas due to wind action from the deep low pressure systems that affect Iceland .
    I always allow for ocean waves and wind certainly around Myrdalsjokull and the south and east edges of Vatnsjokull.

    One other point. As the energy from ocean waves travel through the rocks, is their energy dissipated more quickly by fault lines and changes in rock density? Does the pressure on underlying rocks from an icecap have any effect on how oceanic wave energy travels?
    The more I think about it the more complex this becomes!

    1. Correct the fault lines and cracks will make the waves dissipate more, however this will be more effective at higher frequencies. The Q-factor for the waves mentioned in the article, 100, is already a low factor (means high attenuation).

  22. Cathy, in reply to your question up above …

    “Iceland offers scientists a natural laboratory for studying – on land – the processes that occur along submerged parts of a divergent boundary. Iceland is splitting along the Mid-Atlantic Ridge – a divergent boundary between the North American and Eurasian Plates. As North America moves westward and Eurasia eastward, new crust is created on both sides of the diverging boundary. While the creation of new crust adds mass to Iceland on both sides of the boundary, it also creates a rift along the boundary. Iceland will inevitably break apart into two separate land masses at some point in the future, as the Atlantic waters eventually rush in to fill the widening and deepening space between.”

    I beleive it is the consensus of earth scientists that Iceland will split in two.

    1. Great website, thank you for the link, and your response. That should keep me busy for the rest of the afternoon!

  23. M0.9 – 3.7 km N of Hábunga @ 33% quality.
    M2.0 – 8.0 km N of Hábunga @ 90% quality.

  24. Sunday
    14.08.2011 12:05:28 63.551 -19.106 0.1 km 1.7 99.0 3.2 km S of Hábunga

    1. The repeating earthquakes down there south of Habunga is actually getting a bit stronger now than before, occur about every 5 hours compared with 3-4 hours before. However I think the magnitude 1.7 will be downgraded later.

      1. Ingemar, the alertpage give raw numbers before automatic systems recalc, then they are recalced again by hand to give the 99%. So 99s are never changed. With one very famous exception about a year ago… 🙂
        My point is that I wouldn’t go to far with the alertpage figures if I where you. Yes it can give clues, but I wouldn’t depend on them.

  25. 2 recent earthquakes at Langjökull, I don’t think this is a very common place to have earthquakes?

  26. I just noticed that my second favourite volcano, Askja, had a quake…
    13.08.2011 22:33:04 65.021 -16.671 4.0 km 2.0 99.0 3.7 km WSW of Dreki

    1. Why do you have Askja so high in your potential-list? I believe there are reports that it has been deflating for years.
      Just wondering. 😉

      1. It had been deflating until 2008 or 2009, after that is has been inflating again…

      2. Didn’t know that! Thanks for the correction, I have never been able to find any real-time GPS data from this area, do you know any?

      3. There is also more quakes than before with higher magnitude, and a longterm increase in tremoring. Since 2008 it has doubled in strength.

        There is one GPS that you can find at Sigrun Hs page. Problem is just that Askja is so vast that parts of it might be holding still while another part rises and a third might subside. The mechanics of Askja is wildly intricate.
        I gave a link a couple of days ago that was writen 2010 by Hazel Rymer, look for the link, it is a good place to start.
        But, Askja will probably give warning signs before erupting, but it is like Katla. The warnings will be coming for a long time before going boom. But while everycody has been waiting for Katla, Askja has given off more signs actually, but she is more subtle with a different type of signs. For instance, all those heavy quake swarms over at Herdubreid is believed to be magma movement towards Askja. As I said, the mechanics of that one is hard to interpret and intricate.

    1. Sam, a hint. Miniquakes like that has the energy of a small firecracker. They do not mean anything more than that a piece of rock about 3 squarecentimetres cracked due to pressure.
      If you wish to keap track of the quakes, do it for those above 1 in magnitude. 🙂

      1. Ok thanks Carl, I only really felt the need to post it because of it’s depth, but will keep your advice in mind for future! 😀

        P.S: I am only just beginning to understand the science behind volcanoes. 😉

      2. I remember how it was, in the beginning anything made the blood pound, after a while one knows that most things are normal, and start to know what to look for.
        Katla is still just teasing us. Wait for a bunch of 3 pluses and you will see me start getting upset 🙂

      3. Remember the “Lurking Caveat”, those small ones probably have been there all the time, but it is first now with the wast upgrade of the sensor net that we can see them.
        I still say I wont get excited about Katla before she does something a bit more spectacular. Either a very long and intensive series between 1 or 2, or a series of 3s…
        In my eyes she is not close to erupting.

        But… I’ve been wrong before 🙂
        I guess you remember my prediction that Grimsvötn wouldn’t go before Hekla… 🙂

      4. That was very informative, Carl. If Sam hadn’t posted the data, we would have missed out on learning something from you. Every comment has merit.

  27. It is quite interesting the activity that is SSE in Katla volcano. Just on the edge of the glacier. Since this activity has been almost continuous since it started on 12. July after the glacier flood.

    There is a good and full reason to watch this area. As something might be going on there.

    1. What do you think is happening Jon. Do you think it could possibly lead to a small flank eruption similar to fimmvörðuháls in the future.

      1. I am not sure. But a eruption at that location would be really bad. As it is directly above Vík í Mýrdal town and they would get a glacier flood that would go directly into the towns path if a eruption where to happen at this location.

        But this is not good in my opinion. But at the moment all we can do is to wait and see what happens in that location when the time comes.

  28. Hey people. Again I have a few questions. What do we know for sure about katla’s eruptions? Does she give any signs before one, or does she just get one? I keep on checking her every few minutes, and my boyfriend goes crazy about me sitting on the internet on my phone all the time. Another question is; what does these small earthquakes around katla mean? And how has the activity been around katla the last year or two? Has the mountain been raising? Is there a chance that what happened in july was just a way for katla to release some of her pressure? And the last question; if katla start to show signs of an eruption, how long up front can you see it? From when it’s sure that she will erupt, like.. And jon, thanks for a great blog!;-)

    1. Before instrument that recorded earthquakes. There are only the tails of earthquake that happen shortly before the eruption happens.

      What the long terms sings are is a undocumented part for now anyway.

    2. Remember that we are talking about an immense volcano that has had no proven eruption since 1918. We do not with certainty know how she will behave before an eruption. But… We can on fairly good grounds assume that she will behave like Eyjafjalljökull did, in sorts at least.

      First of all I want to say a couple of things before going into what I believe we will see before an eruption. First of all, she is still a long way from erupting, the second thing is that she has started to be more light in her sleep. She has started to show a few and small signs of an upcoming eruption. She could though go back into dormancy again after giving off more signs. This said, here goes.

      Slightly elevetad tremor levels, but nothing major really. There is movement on the GPS-stations, especially at Austmannsbunga inside the crater. There is a constant medium activity at the Godabunga cryptodome. A cryptodome is a magmachamber that has not yet erupted, but the Godabunga cryptodome is not well understood, it might in some ways be a part of a mechanical or magmatic connection between Katla and Eyjafjallajökull. Or it might be a volcano of its own in the making. Third is this new spot of action in the south.

      Signs to look for:
      If we assume she will have a normal eruption inside the caldera.
      I think it will be like before the Eyjafjallajökull eruption. A prolonged very heavy quakeswarm with hundreds of quakes per day for weeks. Heavy tremoring as magma is pushed up. But first really rapid movement on pretty much all GPS-station. Austmannsbunga would probably move more than a centimetre per day. Then after weeks or months like this we would either have a small flanking eruption before a large eruption (Eyja-conjecture), or a heavy eruption in the caldera directly. The amount of pre-eruption level of activity will give a sign of how heavy the eruption will be.
      Assuming Godabunga erupts.
      Same signs as above, but perhaps even more as there are no previous channels for the magma to go through. Exact behaviour totally unknown.
      Southern flank eruption.
      The signs before such an eruption might be harder to predict, but probably about the same as above. The eruption could be anything from a Fimmvörduhals eruption leading all the way up to an Eldja event ripping up all the way from the flank down to the sea. The last is highly unlikely.

      I would say that you would see it coming for weeks or months. My guess is that we are at least a month away from an eruption, but more likely 1 to 10 years away.
      I think others will give other answers to your questions, but I think most old-timers will all say that it takes more signs than we have now.

      On a personal note.
      Katla is a victim of her reputation and useless speculation from the media-circus. She is just one of several powerfull Icelandic volcanos. There are many more of them, and some of those are probably closer to an eruption.
      As I have said before, Hekla, Bardarbunga and Askja is showing as many signs or more of an impending eruption. It is even likely that Grimsvötn will erupt again before Katla. Hekla is though a special case, she wont give off a lot of signs. She can at any time erupt withing 30 minutes from a first sign. If you want a volcano to observe that craves constant attention to drive your boyfriend crazy with, Hekla is the one. She is close to driving me bonkers 🙂

  29. Hamarinn (SKRO), Hekla (HAUD) and Katla (SOHO) are all showing clearly rapid inflation… A busy autumn and/or winter is coming! ;o)

  30. I dived the Kleifarvatn lake the next day after the quake. There is a lot of activity in the thermal vents, and there is a new big black crater, the size of several cars, with bubbles coming up from the bottom. Have been diving there for two years and this is the most active. Also, the water has receded. The geysir that used to be just steam are now mud geysir again. The fissures have probably gotten deeper, as the water is receding.
    Two months ago the large black crater at 8 meters was the size of a large umbrella. Like I said, it is much bigger now.
    Is there any way to sign up for updates of upcoming quakes from the met office?

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