Posted on by Jón Frímann

Short analyse of events of Katla volcano 28th and 29th of July-2017

Icelandic Met Office released interesting graphs of the activity in Katla volcano during the 28th and 29th of July-2017. It gives clues to what might happen just before an eruption in Katla volcano.

Harmonic tremor pulses

On the 28th of July small and short harmonic tremor pulses appeared on SIL stations around Katla volcano. When 29th of July did come the harmonic tremor intensified considerably from what it had been the day before. The harmonic tremor pluses on 28th of July is close to impossible to see on the harmonic tremor plot on Icelandic Met Office website.


Harmonic tremor pluses as they appear on Icelandic Met Office tremor software on 28th of July-2017. Each frequency has it’s own line. Time is horizontal and intensity is vertical. Copyright of this image belongs to Icelandic Met Office.


The harmonic tremor as it is by 29th of July-2017. After midnight the activity intensifies considerably from earlier levels. Copyright of this image belongs to Icelandic Met Office.

This data suggests that before an eruption happens some type of boiling or increase in hydrothermal vents takes place in Katla volcano. This is also connected to the glacier flood that followed into Múlakvísl glacier river.

Glacier flood and harmonic tremor


Blue: Water level. Red: Conductivity. Green: Tremor activity. Values are at 10 minute central value. This data is from the SIL station at Lágu Hvolar. Copyright of this image belongs to Icelandic Met Office.

There seems to be some connection between the harmonic tremor change and the changes in the glacier flood. That suggest in my view that a minor eruption took place in Katla volcano during 28th and 29th of July. How long the eruption did last is a good question. Harmonic tremor data suggests it was only for few hours before it ended. New cracks have been seen around Cauldron 10 in Mýrdalsjökull glacier according to reports. Locations of cauldrons in Mýrdalsjökull glacier can be found here on University of Iceland Earth Science map.

That would be the end of the story in most normal years. Minor eruption and then nothing more. That does not seem to be the case this time around. Small pulses of harmonic tremor have been taking place during the week (Week 31) and that seems to be ongoing process. Most of the tremor pulses are hard to see on the SIL stations and most don’t even appear on more then one or two SIL stations. At the moment Katla volcano is quiet and that might go on for a considerable amount of time due to this minor eruption (my view) and connected glacier flood.

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141 Replies to “Short analyse of events of Katla volcano 28th and 29th of July-2017”

  2. Thanks Jón. One question: you say that in your opinion Katla will remain quiet now for a while after the short eruption, but on the other hand something seems to be going on because of the the very small pulses. What in your opinion are those pulses and can the lead to something? Thanks!
    By the way, I wish I could help you with your money problem but I am a poor student myself…..

    1. It also picked up a little last night as well but it seems to have calmed down for now. Not so much Earthquakes though apart from the odd small one here and there

    2. It is impossible to know for how long Katla volcano is going to remain quiet. Last few years have shown that Katla volcano can go from quiet to active in short amount of time.

      As for the pulses, that suggests that the hydrothermal system in Katla volcano are getting highly active, at least for the moment. Sometimes they just cool down again and the pulse activity stops. Last year (2016), following the earthquakes in Katla volcano that happened then, no pulse activity took place.

  4. I’d say the conductivity in Múlakvísl started to slowly creep up pretty soon after the glacial flood, but it’s rising faster now.
    I see the pulse activity in highpass graphs (Aus, God, Syl)only while lowpass is very quiet. When there are earthquakes, they show up in both graphs. So it seems to be a different process.

    1. Something is different. The earthquake activity has dropped to almost nothing at the moment and that is highly unusual given the time of the year this happens.

      1. Hi Jón,

        Is it unusual for the red and green frequencies to go this low in the tremor charts?? I don’t think I have ever seen them fall this much. I’ve checked all stations in Iceland, and pretty much all of them show this trend.

        Few examples,

        http://hraun.vedur.is/ja/oroi/hvo.gif
        http://hraun.vedur.is/ja/oroi/alf.gif
        http://hraun.vedur.is/ja/oroi/god.gif
        http://hraun.vedur.is/ja/oroi/sva.gif
        http://hraun.vedur.is/ja/oroi/aus.gif

        Maybe this is connected to the drop in earthquake activity?
        Would love to know what you think.

      2. The tremor bands go this low at the moment as there is almost no wind in Iceland at the moment. That also means there is no ocean wave happening and that drops the noise levels down to almost nothing. The fluctuations in the green and red bands is just noise from the environment.

  5. Jon, are you talking about a magmatic eruption, or a hydrothermal explosion?

    1. This was a lot stronger than any hydrothermal explosion. This was a minor eruption in my view. The science community is still checking their data.

      What happened before the minor eruption appears to be a increase in hydrothermal activity. That is interesting that happens.

  7. What are your thoughts on the V089 atm? Seems to be some high readings. I assume red is conductivity? (Still new to using these charts)

    1. If you are using the live chart. The bottom image named “leiðni” is conductivity. At the moment the conductivity in Múlakvísl (V089 station) is high according to Icelandic Met Office.

      Translations of the live river monitoring images.

      Vatnshæð = Water level (in the river).
      Vatnshiti = Water temperature.
      Lofthiti = Air temperature.
      Leiðni = Conductivity (in the river).

    1. There is no wind to speak of in Iceland at the moment. This also doesn’t look like a human made traffic. I am just seeing minor changes in the harmonic tremor at the moment. It is difficult to know if this is something more than just the glacier moving.

      2. This is pure amateurish speculation on my behalf, but watching the steadily increasing conductivity, micro-seismic noise and popping activity in IMO stations around Katla, I believe there will be bigger earthquakes before the day is over. It might look calm, but the nap time also seems very restless.

      3. Hehe. Bold guesses like that one are foolish and deserve to be proven wrong. But atleast now there’s some activity again.

  9. Jon there seems to be a pattern still ongoing on the charts but still know real quake activity

    1. I’m unsure if anything is going on at the moment. This might just be hydrothermal change happening. It’s all bit a unclear at the moment.

  10. Anyone else getting the message: this camera is offline, when checking the webcam on Katla?

      1. Mmm, really frustrating. Just as things are getting excited… Same thing happend when Bardabunga was acting up. Is this on purpose Jón? Anyone with some connections at livefromiceland.is? 🙂

    2. There seems to be a communication problem in south Iceland. It has also put my geophone at Heklubyggð off-line. I hope they repair it quickly.

  11. Guys I don’t think we are close to anything happening so don’t worry about the camera,I would think she is going to play with us for a while yet but yes she is getting interesting

    2. Yeah, Just noticed jokulsarlon webcam is offline as well, so they’re probably just updating or something

    3. There seems to be a communication problem to that part of south Iceland. My geophone at Heklubyggð has been off-line since 23:30 yesterday (04-August-2017). I guess this problems are connected. I just thought this problem was related to the internet connection that my geophone is using. That does not seems to be the case at all.

  12. What do you think the mechanism is for Katla to have a *minor* eruption at this time? It’s generally assumed that it’s pretty close to the point where it’s ready to have a full eruption – or actually at that point. So perhaps it’s in a delicate state of balance and only needs the right seismicity to open a large enough conduit to the surface?

    I’m thinking in terms of there currently being small quantities of old evolved relatively cool magma rather close to the surface in the hydrothermal system under all that weight of ice; if it does break surface and erupt it’s rapidly chilled and the eruption – for now – capped. Makes sense?

    1. I don’t know why small eruptions happens in Katla volcano. I’ve also not seen any ideas on what might power such an event besides fresh magma pushing up a little bit trough the crust.

      I guess lack of magma pressure might be the answer?

  14. Hmm, the Conductivity seemed to have suddenly shot up around 3am last night and its much more higher than it has been over the past few days. Though it is dropping down again but it looked to be higher than 270 for a good few hours, thoughts?

  15. It certainly is curious, especially considering that otherwise the volcano is so quiet. Usually rising conductivity has also implied more seismic activity, but this time around it doesn’t seem to be the case. Also, those hard to detect little pulses of tremor on highpass keep on going.
    Whatever this means, it looks like a new behavioral pattern. If a volcano is considered as ready to erupt as Katla, new can’t be good. I’m far from expert, but to me it seems that Katla has entered a new stage in its development towards a larger eruption instead of going back to business as usual after a minor event. How long will this stage last and what exactly is going on inside the volcano- impossible to say.

    1. Totally agree; it is curious in deed. We simply don’t know what to expect next, which only adds to the suspension. This discharge of conductive glacial water might be common/typical for Katla (especially during the summer months), but how could this effect the volcanism in the months to come, now that we know for certain that the volcano has entered a more active, restless phase?

      1. What’s also been interesting since last week is the lack of earthquakes around Katla. The only earthquakes which have appeared are at a very low magnitude

  16. I also notice since the 5th Aus pattern has changed again ever so slightly

    1. The pattern appears to be gradually rising a bit from what I can see

  17. Check out FED highpass if you want to see interesting tremors…
    Speaking of lack and weakness of recent earthquakes, during the past year there have been mag 4.5 earthquakes at Katla. As far as I know, there weren’t that big earthquakes prior to 2011 glacial flood/minor eruption.

    1. There has not been earthquakes of that magnitude in Katla since atleast the 70’s. It’s unclear. So yes, something is brewing without a doubt, but how long it will brew, and how the brewing will look like is pretty much unknown territory.

      Hekla (Fedgar), I know very little about. 🙂 Isn’t that the type of volcano that can go boom before anyone knows it’s coming?

  18. There is almost no wind in Iceland at the moment. This lack of wind is going to be the status of the weather for next few days (maybe all week) in Iceland.

  19. Maybe this will help to give a clearer picture on some of these stations Jon and see what is going on at the moment.

  21. Is it me or does it look like something is picking up with the Alf and God models?

  22. Hi Jon.
    Me and my family are walking Laugarvegur next weekend, and started getting worried about Katla. We’re walking from Landmannalaugar to porsmork. Do you know if these areas will be affected if Katla has an eruption?

    1. If Katla volcano erupts the whole area is going to be evacuated. As it currently stands there is nothing suggesting that eruption is imminent as is. I don’t know if that is going to change. While current signals suggest that an eruption is going to happen soon* the question remains when that might happen.

      I am expecting a lot more earthquake activity in Katla volcano just before an large eruption. The current quiet in Katla volcano means that pressure has dropped inside the volcano. At least for now.

      * Soon might mean next year or several weeks from now. There is no good way to know a eruption is going to happen in Katla volcano.

      —–

      The walk from Landmannalaugar to Þórsmörk lacks mobile coverage in large areas. I suggest that you get a PMR446 hand held radio to use on the trip. They don’t have a great range, but good enough to keep in contact where there is no mobile signal.

  23. Looks like some of the SIL stations got a little interesting last night

      1. You would think something seems to be happening, it hasnt stopped increasing yet since the early hours of this morning. No earthquakes as such yet though, whether that’ll change later on. Not sure though. I’m just guessing from what’s being shown on the stations 😛

      1. This looks like a ocean wave noise. There is a strong wind on the west side of Iceland. It is several hundreds of km away from the SIL station around Katla volcano. But it still seems to have an effect on them.

    1. Looks like traffic noise, mostly cars passing by this SIL station. It happens, there is good weather in this area so traffic might be more then normally when the weather is poor or bad. This is the high season for tourism in Iceland.

    1. I was wondering about that one as well. if you’re reffering to the small jump around midnight 07/08. I’ve been on the look out for anything that might look like harmonic tremor. It looks like a small quake happened at the same time, but it was one of those right on the surface as far as I could tell.

    1. Noticed it, too! Usually when there are spikes like this on most/all stations, it’s signals from a far-off earthquake of significant magnitude (and depth).

      USGS reports a M 6.5 in China, but that was well over an hour ago…
      Perhaps there’s a bigger EQ that has yet to be registered by the global network. I don’t know.

      1. It also seems as if vedur.is is a bit delayed with the earthquakes. So that’s a possibility!

    3. The large Mw6.5 earthquake is in the spikes now. But there is something more going on at the moment. There might be a signal on SIL station Álftagröf (alf).

  28. That god tremor chart troubled me yesterday. Otherwise, Katla seems more normal today: plenty of small earthquakes and high but not super high conductivity.

    Sly lowpass and god lowpass look the same as alf, but interestingly the phenomenon is much weaker at aus. Correct me if I’m wrong, but if Katla was about to erupt (esp. in the caldera region where most earthquakes have happened), I think we would see more action at aus…at least more than at the stations farther from the caldera.

  30. Earthquakes now picked up at Katla from earlier, still at low magnitude

    1. Sorry (Didnt realize I posted that twice) thought it was my internet playing up

    1. The drumplot lowpass filter (which I’m not good at reading) shows some anomaly for about 30 minutes, around the same time as the M6.5 in China. Same pattern is also clearly visible at GOD, but less so in AUS, SLY, et ceterahttp://hraun.vedur.is/ja/drumplot/drumplot/alf_lowpass_0.7.png

  32. Thomas, I think that we are still within normal variation. It will take some time (and preferably anomalous data from other sources) to see if there’s something unusual.

    Which is not to say that it’s not worth keeping an eye on… : )

  34. I think something happened in Austmannsbunga (or close to it). It is not wind, but Austmannsbunga is now in the strong wind path.

    The only confirmation that might appear is higher conductivity in next few hours in Múlakvísl (possibly other glacier rivers around Mýrdalsjökull glacier).

    The weather forecast is strong wind until Friday at least.

  35. It’s interesting how the earthquakes have shifted from the east side of the caldara to the west side.
    Jon, would there be a possibility of a fissure running out that direction?

    1. As I understand it the whole caldera is a fissure in all directions. This earthquake shift from east part to the west part of the caldera also happened in 2011. I don’t think anyone knows at the moment why this happens.

    1. Yes, Katla and the volcanoes in this area (maybe not Eyjafjallajökull) are rift zone volcanoes. A new rift zone is forming south of Vestmannaeyjar volcano that is of the same type as Katla volcano. It might even be bigger, it is just under the ocean making it difficult to see how big it actually is.

  38. Jon I have a question for me, but if there is a subglacial eruption, the thawing water should not flow into the volcanic duct and produce violent phreatomagmatic eruptions?

    1. It will flow into the erupting crater for a while. Making the eruption ash like (no lava). If that stops depends on how long the eruption last or if the crater can seal off from the water.

      Once the water is out of the crater any eruption in Katla volcano is going to turn into a lava eruption like in Holuhraun (2014 – 2015) eruption.

  42. Not sure if its worth keeping an eye on the V089 at all with the water temperatures rising or if that’s just a normal thing to happen

  45. I see Katla is more quiet today now with no Earthquakes or anything since early afternoon. The day it comes to erupt though I bet that would produce some nice sunsets in other countries. Plus I imagine a Winter like the UK got in 2010 which I imagine was partly down to Eyjafjallajökull?

    1. Eyjafjallajökull volcano eruption in 2010 was not powerful enough to change the weather. I don’t know if Grímsvötn eruption in 2011 did manage to change the weather the following months. It was not long lasting effect.

      All that Eyjafjalljökull volcano did was to diminish the endless greenhouse gas emission from air planes for few days.

      https://en.wikipedia.org/wiki/Air_travel_disruption_after_the_2010_Eyjafjallaj%C3%B6kull_eruption

      I was unable to find any good article that had information about the CO2 that was not emitted due to grounded flights those few days the airspace over Europe was closed.

      1. Ah right, thanks. Wasnt too sure after the amounts of snow we had the following Winter from the eruption

      2. As we do for almost all late winter spring and early summer years Grimsvotn eruption in 2011 caused an extremely cold winter opposite the southern end of Hudsons Bay and west to Winnipeg

    1. There is mostly wind noise on that SIL station at the moment. Currently low pressure systems have been passing over Iceland with strong wind and rain.

  47. Snowball GB was post solar minimum of the 23rd solar cycle 2010 & 2011. It was the deepest minimum in 100 years. But who knows weather is capricious with all the huge amounts of trace co2, cosmic rays and volcanic sunsets during thoses pause years! Oh yeah, those were the years of noctoluecent clouds in the southern US and the shrinksge and cooling of the upper atmosphere and a bunch of big eruptions in kamchacta and the Kurile islands.

    1. Earthquake activity at the caldera margins. Not related to volcanism. This are tectonic stresses being released. A large earthquake might happen but again, it might not happen.

      Nothing to worry about. Yellowstone is not going to erupt soon and if it did, it would just be a minor eruption. Like in 1350BCE (that is ~3300 years ago I think).

      https://volcano.si.edu/volcano.cfm?vn=325010

      1. you are not sure about Katla, but you can say for sure that in yellowstone would be just minor eruption ? 🙂

      2. Radek I’m sure about Yellowstone.

        There’s a substantial body of opinion in volcanology that Yellowstone is very likely pretty much played out as regards large eruptions; it can never erupt in a big way again simply because the hot spot that started it has moved too far away; it’s now under very thick cratonic crust and may take a million years or more to burn its way through that and for a new caldera to form. That’s what it’s been doing for many millions of years – hence the chain of calderas of which Yellowstone is just the latest.

    1. Not sure if Alf is picking something up but I imagine its most likely to be wind noise

    2. I noticed that too. Not sure if it is wind noise. According to vedur, wind conditions shoul be varying in that area but god, alf and hvo lowpasses look very similar to aus. Also, conductivity in Múlakvísl is rising though not very quickly. I think we’ll be wiser in a few hours…or when Jón shows up.

      1. Yeah, it’s still rising and is now ar around 200 plus a couple of sharp spikes apear now and then. Suppose we’ll know for sure in a few hours like you said

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