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 (Rú
Fylgjast með aukinni virkni í Kötlu (Ví
Eftirlit aukið með Kötlu (
Flogið yfir Kötlu (

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. If you can’t see the Katla webcam provided by RÚV due to your operating system or your web browser not being compatible, you can use VLC to play the stream directly. 1st you need the VLC player ( then once you have it installed, go to ‘Media -> Open Network Stream’ and enter this URL into the URL field: mms://

      1. Is it me or has the glacier shrunk a little, or a trick of the light? It has been a month or two since i last viewed. All very quiet.

    1. Thanks a lot Seattleite, now I can make screen captures again from this webcam. It didn´t work here with any browser. From all other webcams it worked, but not with this one.
      You seem to be very familiar with this player, may I ask you if it is possible to make video captures with it? That might be really interesting if something happens. And so much easier to make clear to others what one have seen.

  2. IMO:- “19:02:11 63,642 -19,146 1,1 km -0,1 68,97 5,1 km A af Goðabungu” the first since early afternoon local time, very small.

  3. hi guys. I don’t know what to make of this, so I’ll leave it to you experts. I am a rabid saver of Katla webcam shots, and I THINK I’ve spotted something. The following gif is 6 images, the first two from the 18th and 21st of July this year, (for comparison) and the last 4 from just now, this past half hour. At first I thought the cut off look at the top of the glacier was caused by clouds, but I’m not so sure having compared images. it LOOKS like the top of the glacier has sunk down some considerable distance…

    what do you think? weird, eh?

    1. No, I don’t think so. I guess this is due to the very different lighting of the area. In some of the images you can hardly distinguish between sky and ice.

      1. yeah, i thought it might be clouds at first too, but the fact the same shape to the top keeps showing in every shot I’m taking is making me think otherwise. as you said though, the lighting is a bit dodgy. I’ll wait and see. Just thought I’d show you all.

      2. @Mark:
        If you magnify the image (current) you will notice that the contour of the ice above the evidently “visible” line can be seen. White ice against white clouds: whiteout. That gives the “shrinking” impression.

      1. no Al, it was an effect of the light. You can see it more clearly now.

        Still puzzled as to why the areas closest to us on the glacier have gone far darker, whilst the very top of the glacier has gone white, when compared to previous pics, but one thing it isn’t is a slump.

        perhaps snow overlaying the Grimsvotn eruption ash was washed off by heavy rain, exposing the ash layer?

        anyway, sorry for wasting all your time. just goes to show you need to exercise caution when making judgements about what is ‘OBVIOUSLY’ in front of your eyes. Your eyes, and webcams, play tricks on you.

    2. Thought the ice looked darker earlier today, which implies that top snow has melted or been washed off, if you have had recent heavy rain or warm weather. Or, if the ice is thin, the ground could be showing through. All of which I have seen on Swiss alps with no associated volcanic activity – entirely due to weather. Don’t know Katla well enough to know if this is normal for this time of year or not.

  4. Tremor seems be to rising again after a small but significant earthquake swarm.

    The Lady decide to wake up slowly but surely !

    PS : Sorry for mistake, i’m french and i’m learn english language.

    1. Pas des problemes ici.
      We are all welcome here with our misspellings and language issues. That’s why I love these guys. 🙂

    2. Guigui – Don’t worry about the spelling. I live in Canada, and I know people here who have been speaking/spelling it all their lives who spell worse than you lol.

  5. Hello. I was near Kleifarvatn to day picking bluberries. I did´nt feel any quakes. I left 17.00 . Very nice weather exept rain for 10 min.

  6. Thank you Renato. I following the excellent website since several months but i decide only now to participate with messages.

    I want to felicit Jon for he’s excellent work to following volcanic situation in Iceland.

    I’m fascinated by all the natural disaster (Earthquake, Hurricane, Volcano, Solar Storm, Weather, Climatology and the rest).

    If not, to present me, i’m live in Switzerland, and i’m 27 Years Old. Voilà !

    1. Welcome, Guigui! I’m also from Switzerland, but the german-speaking part. Don’t speak french ( to complicated *smile*).
      Have fun here.

      1. Argh. My natural language is French, i’m learning english, but german is more complicated than English. lol.

  7. And once again orogenic clouds being driven upwards by some kind of air draft. Coincidentally when we suspect a hlaup is under way.
    I wonder where this sudden upward winds originate from.

    1. That’s really weird, I was watching the cam and all of sudden it looked like an avalanche/PF.. are they your orogenic clouds, Renato?

      1. I only see things. Coincidentally they happen in such occasions. Perhaps this is normal behaviour, but it always intrigues me.
        Caveat: I’m not implying there is a steam plume, or anything volcanic!

      2. “Cloud fronts are often formed over mountains. As the surface winds encounter mountain ranges, the air is diverted to cooler, higher elevations where the water vapor condenses to form clouds.” – this is what I found about orogenic cloud fronts.
        That’s what we often see at Katla.
        But every time there is some “action” taking place they begin to behave weirdly. Especially given the fact that wind is almost none.
        But this one doesn’t look especially weird today. We’ve seen them forming vortexes right over the glacier, but this one seem to originate at a lower surface, with no ice beneath. So, simply fog.

  8. It would be nice if perhaps someone who is intimately familiar with Katla could take a still of the webcam shot and highlight the geologic/volcanic features of Katla for those of us who are unsure what we are looking at, or looking for. Identifying things such as the caldera, distances, locations of past eruptions, etc. Cheers!

    1. I was thinking the same thing last night, Boucher. At least the Katkla webcam shows where the camera is located in relation to where it is pointed. And there is a small but very different looking cloud/fog/steam formation showing right now.

  9. @ Jay,
    A small article on this subject by National Geography (hopely a good source, Jón): Iceland Lake Disappearing Into New Crack in Earth, concerning the 2000 Kleifarvatn happening at

    “…….. she and her colleagues assume the waters will return. The last time a similar event happened was in 1912, after a magnitude 7 earthquake, and it took about three decades for the water level to normalize, she said.”
    So 2000 was at least not the first time the lake partly disappeared.

    1. This trend stopped a few years after and the lake was back to normal levels in 2008. Last fall another episode of disappearing water started.

      1. No, I don’t mean the clouds/ steam. A view times per day a little white thing, cause very rapid to the left side of the screen, and then it goes back to the right again. It goes across that “path” you see on the left site….

    1. No, it’s not steam. For the last time, volcanoes don’t steam before eruptions. Only after.

    2. Having watched it for a few minutes, my money is on low cloud at the moment. Don’t know why it is hanging around when the cloud behind it is moving but I do not know the topography well enough.

      1. Silly me… I really ought to lurk more, linking on the stream links on main page works too. Thanks

      2. Interesting upswing on all graphs, i take it the electrolyte and ph are counted although i’m not great with giggle translate. Can we safely say a minor flood may be apparent, or has it happened already

  10. No, I don’t mean the clouds/ steam. A view times per day a little white thing, cause very rapid to the left side of the screen, and then it goes back to the right again. It goes across that “path” you see on the left site….

    1. I think i saw a bright dot on the top left hand side… In the absence of rational argument i would suggest ufo’s or perhaps lens flare?

      1. Hahaha, that’s the most plausible explanation 😉 When I see it again, I will try to make a screenshot… Could also be a very, very quick sheep…

    1. Your feeling is same as mine re 48 hrs map, but studying the Dutch website (posted before) this appears as maybe one sort of plume (“tracing” up near Austmannasbunga), then like “dividing” (like horse-shoe), one arm west, the other arm in semi circle south and west. This might be illusive, all todays and yesterdays EQ in question are well within the caldera. The EQ might “be around” an “magma reservour”. I doupt it is cryptodome (?), rather like quakes happening around something (softer/hotter rock, that does not crack?) but again might be circumstential so to speak. I repeat my view from before, I think it will erupt, rather sooner than later. Maybe some days or weeks, if it continiues like this today.

  11. You would have to see some kinda ash cloud starting to form when an eruption is taking place, right? Or is it just gonna explode?

    1. The first signs will be earthquakes, massive amounts of earthquakes accompanied by harmonic tremor. As soon as the magma breaks through the surface an ash cloud will form and explosions will take place.

      1. I know nothing about volcanos but just wondering would the ice not steam as the magma melts it or would you not see it, just curious

      2. Well most of the ice melts and forms the well-known Jokulhlaups or glacial flash-floods. A minor part does evaporate before it gets the chance to escape the heat, but most of this happens beneath a massive icecap and will not be visible. As soon as the magma has penetrated the crust and found a path to the surface, it will form hydromagmatic explosions which are very powerfull.
        In fact, without these massive icecaps, Icelandic volcanoes wouldn’t be all that ashy, the only water it will react with is groundwater. After all most Icelandic volcanoes erupt mainly basaltic magma which contains little silica (gas) which makes the eruptions so powerfull.

        This is also the reason why volcanoes near subduction zones are so violent. They are a result of the melt of the subducted oceanic slab. This slab contains massive amounts of water which forms a deadly mix. Basic rule: magma + water = no good.

        (Sorry for getting off-topic a little!)

      3. Pieter:
        A small correction silica is not the same as gas, but some silica rich/silicic magmas contains more gasses.
        I know you know, but it got unclear here 🙂

      4. I think katla is getting ready to blow, within the next week, if not sooner. Just hope it puts on a good show, but also that people are safe!!

    2. I had an amazing .gif bookmarked of the first minutes of the Grimsvotn eruption this year. It was captured by someone passing the Vatnajokull while the eruption started. It was very usefull to imagine how eruptions start. Too bad I’ve lost the link, anyone else maybe?

      1. Ingolfur_KPS_samsetning7.gif i think although i’m not sure if you get the file here. How to send post?

    1. We had better remind everybody that the Atomic looking eruption gif is Grimsvotn. Just in case.

      That is a really good gif.

      Katla has quietened a little now, what a day.

  12. In Katla seems that now it’s the turn of the tremors from 0.5 to 1 Hz red
    just see in this

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