Posted on by Jón Frímann

Strong harmonic tremor pulse starting in Katla volcano

There seems to be a strong harmonic tremor pulse starting in Katla volcano. I do not think that this is anything else for the moment. I do not have any more details at the moment. But I am going to post updates when I know more.

Start of the harmonic tremor pulse on the SIL stations that he appears best on.


Slysaalda, north of Katla volcano. Copyright of this picture belongs to Iceland Met Office.


Rjúpnafell, South-west of Katla volcano. Copyright of this picture belongs to Iceland Met Office.


Lágu Hvolar SIL station. Copyright of this picture belongs to Iceland Met Office.


Álftagröf SIL station. South of Katla volcano. Copyright of this picture belongs to Iceland Met Office.

The start of the harmonic tremor event can be seen on the end of harmonic tremor chart. It stands out as it above the background noise on the SIL station. Next update on the SIL stations (10 or 20 min until it happens) is going to show more how big event this is going to be.

More updates when I know more on what is taking place in Katla volcano.

Update 1: The Public Civil Emergency Authority (Almannavarnir) in Iceland has increased monitoring with Katla volcano. But they have not declared any emergency level yet. Announcement about that in Icelandic can be found here. But scientists where flown over Mýrdalsjökull glacier at 18:00 UTC today (6. September 2011).

According to the news there has been increase in conductivity in Múlakvísl river. But for the moment the water level has not increased. There has been speculation that the tremor was created by water on the move. But that is unclear at the moment, however it is quite possible that more water is on the move under Mýrdalsjökull glacier.

Currently the harmonic tremor in Katla volcano has dropped back to normal levels. For the moment everything is quiet in Katla volcano. But that can change at any time without any warning.

News about this in Icelandic.

Órói undir Mýrdalsjökli (Rúv.is)
Fylgjast með aukinni virkni í Kötlu (Vísir.is)
Eftirlit aukið með Kötlu (mbl.is)
Flogið yfir Kötlu (mbl.is)

Update 2: It seems that a new harmonic tremor episode is about to start in Katla volcano. So far it has remained small. But it is impossible to know if that is going to change suddenly or not. Update 2b: There is also some wind noise on the seismometers around Katla volcano. This wind is increasing background noise. It often look like a tremor increase, while in reality it is not.

Blog post updated at 18:37 UTC.
Blog post updated at 18:46 UTC.
Blog post updated at 20:03 UTC.
Blog post updated at 20:29 UTC.

230 Replies to “Strong harmonic tremor pulse starting in Katla volcano”

    1. a) As far as I know…
      b) Oh my, (insert favourity of deity or demon) happened there. I hope someone kicked that instrument.

      Both Krisuvik and Godabunga 11 minute plot is quite off the chart.

  5. Many of the SIL stations are showing today as being livelier than they have been recently. Is this all from Katla?

    P.S. when the rain stops I’m off to get a decent map of Iceland, if they have them here.

  7. I hope that the people who were walking there an hour ago in front of the webcam are getting out.

    2. Thank you. Local shops and library a bit deficient when it comes to information on Iceland.

    1. Carl, Are the EQ’s not meant to follow such a shift, also with a temor ongoing like this too?

      1. Remember that Katla and Hekla are unrelated volcanos.
        Normaly in Hekla you have a transient and then quakes and tremoring. This was just Hekla feeling the jolt from Katla.

      2. @KarenZ
        I have problems with the captcha and my replies are never in the right positions
        Sorry!

    2. On that site. Everything is covered in ash from EJ, Grímsvötn has not erupted yet.
      All the cracks in the ice on Katla are very clear. Great near up to date satellite, more so than google Earth.

      Katla has quietened again, for now.

    3. Thank you. With two maps, I might not get confused between the Reykjanes Ridge, per IMOs maps and the Ridge beyond IMO’s area!

    2. This is a IMO screen grab. Where did you get it ?

      This might have been a dike intrusion or hydrothermal system going crazy. Hard to know for sure.

      3. We mean: where do these images you’re posting originate from? Do they come from some public website? Or are you an IMO insider with access to restricted data and tools and posting info from there?

      4. I am insanely curious about how you are getting them.
        But it is either a Jökulhlaup, a large dyke intrusion, or a severe degassing due to blocking of the roof above the magma-reservoir.
        I wrote this in the order of likeliness according to me. The last of course is very unlikely indeed and would be bad.

      5. I have no connection to the IMO. The image is from a public website, but I never link to it directly since I fear that it is not supposed to be in the public domain.

        On a related note, I prefer to post static images of graphs like this so that a few months from now we can look back at the data.

      6. Are you the man who drives a 4×4 up to EJ with the cameramen when she was erupting.
        Pardon me if you are not but your name is the same.
        Thanks for the graph and if it was you in the 4×4 double thanks. 🙂

      7. Thanks for the answer. I do wish I had that data. I had a link like that on my crashed computer, but that one did not contain the new SILs.
        I wish I had the link though…

      8. @Rustynailer Nope, that wasn’t me – I wish it was though :o)

        the IMO has a website for data that it provides open access to http://brunnur.vedur.is/

        There is a ton of stuff there and if you visit myndir you’ll find an image called grjot.png
        But let’s try to keep it to ourselves so it doesn’t get moved to somewhere else (there may be reasons that there is generally a longer lag for most of the IMO stuff)

      10. @Carl le Strange: it would be useful if it was mirrored somewhere in Jon’s website at reasonable time intervals (10-15 minutes) so that we wouldn’t waste IMO’s bandwidth (but rather, Jon’s websites 🙂 ). I wonder if he could do this.

      11. Really, all it would take is a new crontab entry to wget that file into Jon’s server at regular time intervals. If he wanted he could also crop the image in order to split the relevant bits into separate files with other utilities.

  19. The anomaly at Krisuvik is still going on, and there was a quake, right after it started, in the middle of the bloody lake.
    Tuesday
    06.09.2011 15:42:00 63.934 -21.982 8.2 km 1.1 90.01 6.6 km NE of Krýsuvík

    Tremor-anomaly:
    http://hraun.vedur.is/ja/oroi/kri.gif

    If this is not a kick in mee wee arse it is more energetic than the Godabunga event… Oddness indeed…

  20. Has anyone calculated the time and effects of surface run-off getting through the glacier via moulins/crevasses to the rock/ice interface to possibly give an increased ice movement within the caldera towards the known low-spots in the caldera wall; or for said water to permeate to such a depth in the bedrock to produce pseudo hydrothermal events and/or sub-phreatic explosions?

    1. No, and it would be a mathematical NP-problem. You simply can’t calculate it out of to many unknons to beginn with, and in the end to many factors to be possible to compute.

      1. @ Carl
        Time for a dram of Clynelish (pron Clyne leesh) from Brora – new one to me ‘n’very tasty! Need summat with all this excitement, Krysuvik’s very active

      2. I am going to go excentric on you. Since I am home in Sweden I am going to drink on my own apple-icewine. Applewine that you deep-freeze in a zip-bag that you turn around every fifteen minutes outside on a day that is colder than minus 25. After a couple of hours you have ice-mush. Then you filter away the ice, and presto, 40+ percent apple-tasting spirits…

        Yepp, something happened in the bowels of that one. I think she is drinking her fill from Lake Kleifarvatn.

      3. I froze some home made wine once. I had about 50ml of “concentrate” after discarding all the ice. I drank it all at once and blacked out almost immediately. I think it was something like 90% by volume. Potentially deadly. Be careful!

  23. This tremor activity is going to continue. So I am going get a nap now until 18:00 UTC.

    This is going to last for few hours, so prepare for a lot of up and down tremor activity.

    1. Jón, before napping, what the hell is happening in Krisuvik.
      There is hellish tremoring, and now a swarm under the lake.
      Is water going down a crack or what?

      1. Ruv News : Water rush in / from Katla today, says IMO. Water-tremor (NOT eruption) says it now live at RUV / Rás 2.

      2. Hihi, I would love to see water rushing into Katla. Would be a site with an inverted Jökulhlaup as the ocean roared up the mountain 🙂

        Thanks Islander! Now we know what it was.

      3. Water vapour cooling off.
        So in a sense of it, yes it is steam, but in the form of cloud formation as warm humid air is being pressed up the mountain side being cooled down in the process.

  26. Hi my name is Christian!

    I just flew over Eyjafallajökull, Myrdalsjökull and Grimsvötn a week ago and filmed the icecap-depressions where Katla is, the Grimsvötn vulcano lake and SE-parts of Vatnadalsjökull. It was incredible beautiful. Feels a bit strange though sitting secure at home waiting for a volcanic event now when I was there just a couple of days ago…

    I am very interested but a rookie in the volcanic business.

    Thank you Jón for a very good work on this blog! Will follow this closely.

    Cheers Christian T.

  27. The small quakes at Katla have stopped the last one was at 13:58. A pause or is it stand down for a few more weeks?

    My guess is just a pause.

    1. Katla tremour today “likely is water” (an Jökulhlaup in progress?) in the caldera (not “rushing in”) says IMO specialist in RUV news just after 17:00 UTC (but they are watching and have notified Civil Protetion unit “Almannarvarnir” of this event). She also spoke of increase in rafleiðni in Múlakvíst, also some “titringur” (vibrations = Harmonic Tremor !!!!!!??????) within Katla Caldera.

      I have open all tabs on my PC on this, hope it does not choke…

      1. Whenever an Iceland volcano gets even the slightest bit above normal noisy, I have all the tabs in my computer open too. It was EJ that started that 🙂 If there is an eruption I bring in the laptop as well…I am not joking lol .

        RUV have “According to information from the Meteorological Office’s cycle now died out and no evidence of volcanic eruptions in the near future.”
        That was in the post before the one about the water.
        Oh yes, I google translated, just thought I had better point that fact out, just in case I lost some in translation

      4. It’s at least increased flow.

        I’m just sitting at home turning the camera remotely.

        That truck is from Míla (Communications company) that runs the site that the camera is positioned on.

  31. from the VLC Windows or Linux have a look
    the Katla
    rtsp: / / 212.7.206.43:1935 / mila / grimsvotn.stream

    1. Carl, I also saw the “flood”, but it was a still image, and I also saw it being removed. Somebody held a photograph in front of the cam I suppose. Probably one of the jolly hikers from earlier today on his way home.

    2. That camera is pointing at where the flood will pass I presume. It will have ice and rocks at first from what I have seen of previous floods.

    3. Help needed!

      To my great frustration I can no longer get the RÚV webcams since the latest “upgrades” (not so much) to my MacBook Pro. And the Míla webcams only work sporadically. I am running both Firefox and Safari.

      If anyone knows the solution to this problem, please let me know. In the meantime, any screen captures you all could provide would be most welcome! I miss my Katla-cam!

      4. OMG, it worked! Thank you so much!!!

        @ Jay and Starwoman — you have to try this. First it opened up a sort of messed up screen with no picture, as usual. Then Windows Media Player opened and voilà — Katla! Now I am just waiting for some sheep and I will be truly happy…

  33. What the hell? Why there was an harmonic speak in Katla that is now followed by an harmonic tremor in Krisuvik?!!! I am surprised! I can’t understand this!

    If you look closely, one came after the other. Katla tremor is returning to normal; Krisuvik tremor is peaking now. It seems that the powerful tremor in Katla triggered a tremor event in Krisuvik.

    Civil protection is going to fly now above Myrdalsjokull to see if something happened over the glacier. http://www.ruv.is There is a high change of a glacial flood in the next mins to hours

    1. Krisuvik is right of the scale…
      Green and Red bands are off the chart somewhere up in the great blue yonder. But since we know it is up above 5000 it is a lot. I will love to see this as it resets the scale. I guess red and green is up towards 7000.
      Either it is the dyke intrusion from all living hell, or Lake Kleifarvatn is dropping into a hole at an increadible rate.

      1. And why the thing in Krisuvik just happens half an hour after the Katla one? There shouldn’t be a causal link between them, but now I am getting convinced of otherwise.

      2. Nah, I do not think so.

        Katla has been brewing for days, so that was expected.

        Krisuvik I think is due to increased movement in the MAR. I think that a fracture opened up under the lake and that the tremoring we are seeing is water dropping down. We have had a few quakes directly under the lake the last days, and I warned about this being a posibility then. I think it might be this that is happening.
        It has happened before after all.

        I just hope it wont hit any magma…

      3. This is a crazy afternoon. Harmonic tremor happening at the same time in Katla and Krisuvik.

        Krisuvik: most quakes have been happening over a wide range of depths, but also to low depths.

        I think Krusivik erupting might behave a little bit like Hekla. Explosive first, after all there is a crater lake, and the volcano is close to sea. Then, massive amounts of lava. Because it has been long before last eruption, I think the lava amount is going to be quite big.

      4. Is that how vulcanism in that area goes? That is more frightening than Katla.
        I believe(read somewhere on the Net) there is a large stretch if Iceland highway that is made from a special lava that has erupted rapidly into water and made a large sheet of very foamy rock many 100s of years ago. The Iceland authorities ground the special rock up to make the road, it makes a good road.
        The water dropping on to the lava through a fissure sounds more like explosive.

      5. @Irpsit:
        The last eruption was a gentle hawaiian affair. But that eruption was away from the lake.
        With the current activity an eruption would be just horrible.
        @Rustynailer:
        The roadmaterial I think comes from Raudholar (Brennisteinsfjöll). They have excavated a lot of material for roadconstruction and buildingmaterial out of that place since the WWII.

      6. Movement in the tectonic plates maybe? Hypothesising that the less stable ground / thinner crust in the calderas / volcanoes may be more susceptible to quakes. There have been largish quakes 4 – 5 ish on the Richter scale both North East and South West of Iceland recently. May also impact the likelihood of an eruption?

  34. I think it’s about time people read Wiki about ‘Adiabatic Lapse Rates’ – ie the rate at which an air body cools with altitude, ‘cos we’re getting a lot of confusion with water vapour and “eruption clouds”. Katla and Ejaf cams often show excellent examples of orogenic cloud formation and in the valley towards Ejaf , an inversion layer. These are wholly an atmospheric happening and are in no way related to volcanism other than the mountain causes warm moisture laden air to rise, cool – which lowers the vapour point and localised clouds form, often ephemeral with each air mass – think of how a cumulonimbus form with a thunder head.
    Volcanic clouds only occur with an eruption and are ash laden with a relatively small proportion of water vapour per se.

  38. You can also see clearly tremor in Nylenda, Sandskeid, Vogsogar, all in Reykjanes, near Krisuvik.

    So there really seems to be harmonic tremor happening at Krisuvik!! Crazy!

  39. I think they are only pointing the webcam, once in a while to the river, not to show the flood but rather to know when it starts. This is critical because the weather is good and many cars/tourists are on the road. They should close down the road. Probably they will.

  40. Has anyone had a look at the lake at Krisuvik? If something is up maybe its visible up top.

  41. Hydrodynamic tremoring at Krysuvik:

    I think that the earthquakes under the Lake of Kleifarvatn had reopened the crack created by the 2000 large earthquake over at SIFZ (Sprungur-area).
    Heave harmonic tremoring followed by a 2,3M quake and a small swarm followed with a slight increase in tremoring.
    The harmonic tremoring is on a very high scale. We are talking values that we do not normally see unless it is a Jökulhlaup or eruption ongoing. There is though no eruption happening. But there might be “Vatnhlaup” or what one calls a Jökullhlaup of water falling down into a crack.
    Last time the water fell into a crack nothing happened, but after a magmatic root-filling started. My fear is that this hydrodynamic event will saturate the ground increasing the likelyhood of an explosive eruption.
    Nightmare scenario is of course an eruption under the lake Kleifarvatn.

  42. There is no harmonic tremor in Krýsuvík volcano. But this change in the tremor plot was due to the earthquake swarm, it appears to be have quite dense earthquake swarm.

    1. But the tremor plot changed in several stations in Reykjanes right after the earthquake swarm. Its not Krisuvik alone. This type of change on the plots is similar to the change that occurred in the stations around Katla, a few hours before.

    2. First tremor, then quakes Jòn.
      I never said it is harmonic tremoring, but some sort of tremoring at high levels are going on. The tremoring started about 30 minutes before the quake at 2,3M hit.

      1. Sorry for having said “harmonic”. I did not know about that tremor only related to geothermal activity does not have the word harmonic before.

        And yes, Carl and Jon, I also noticed that the tremor change in Krisuvik started before the earthquakes. But if this is so, then, whatever happen that caused the tremor, caused later the earthquakes (but some of these were quite deep). A water drainage could not cause an earthquake swarm with some quakes quite deep.

        What do you think?

    2. It’s hard to tell what’s happened to the 0.5-1 and 1-2 bands though, they’re either behind blue or even further off the scale.

      Is there an 11-min median one for kri in the same way as there is for god?

      1. You can see them shoot off the scale in the beginning (at least the green is visible as it goas away, and it is probably hiding red going to since green goes over red.

        No 11 median for it.

    3. Yes, definitively it’s not magma connected. Seems water-related. I also think the earthquake swarm caused some fracture to open and moved some water below ground. This caused the tremor event in diverse stations in Reykjanes. So it must have been a significant event.

      Katla event seems however magma-related. I also agree with Carl that probably it’s magma blocked by the upper layers of the crust, and trying to push upwards. I think this has been happening for quite some time. But once in a while a small portion of magma escapes near surface and causing a glacial flood.

    4. Fireman, the green and red bands are also up, so much that they have left the kri.gif plot altogether. If they recalibrate we would probably find them up around 7000, you can see the green band shooting off up through the roof.

    5. I think that Krýsuvík SIL station is broken, or at least faulty. So because of that why the tremor level is too high. What might be wrong I do not know.

      1. First I thought someone had kicked it, but then it stayed up there.
        I guess we will notice. I agree that if it is not some kind hydrodynamic tremor, it might be a faulty gage.

        But it would be fun would the worlds largest toilett bowl flushing 🙂

      2. I forgot, the reason I am a bit dubious about the broken gage is that Vogsosar is also up, together with a couple of other. Not nearly as much, but still.

  44. IMO Mýrdalsjökull – earthquakes during the last 48 hours has gone off line nothing since 13:58 Iceland time. Page now showing :- ” Earthquake map not found
    The graph of earthquake timing and magnitude was not found”

    Alternative http://www.ijsland-enzo.nl/ijsland/actueel_uitbarsting.asp Good site not constrained, the results are as they arrive and not corrected last EQ 13:58 Iceland time but the page is still open, so I presume still no fresh EQ’s at Katla.

    1. I think it was Jón’s nap that did it… Many a famous last word. The Kettles off for a while now trust.
      captcha appropriate: “formJn absence”

      1. Those captchas make me giggle sometimes 🙂
        Mýrdalsjökull is still quiet with EQ’s but tremor is still up, to my untrained eye at least.

  45. Tuesday
    06.09.2011 18:31:08 63.916 -21.996 9.5 km 1.0 90.01 4.7 km NE of Krýsuvík ?
    How deep do the quakes need to be there to be at all magmatic influenced?

    4. That was much bigger but not right under the lake, more West.
      Looks more dangerous now even with this small swarm, but I am no expert.

  48. The quakes all seem to be focusing around Kleifarvatn, with regards to above comments by others, the loss of 20% of surface after the quake of 2000, the cracks had sealed and by 2008 had regained the original level. (via wiki) Is this a historical sequence repeated often?

  49. She’s sitting there smiling at the camera…looking so peaceful and innocent. “What?…… me?……. erupt? I’m a lady!”

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