Harmonic tremor pulse in Katla volcano

There appears to be an harmonic tremor pulse going on in Katla volcano. While I currently do not think that this is going to start an eruption. It is worth watching this harmonic tremor pulse in Katla. But in the year 1999 this type of activity did result in minor eruption in Katla volcano on the 17. July that year (it is believed).

Harmonic tremor pulse can be seen on the SIL station Lágu Hvolar. Copyright of this picture belongs to Icelandic Met Office.

Harmonic tremor pulse can be seen on this SIL station Álftagröf. But it is hard too see it then on Lágu Hvolar. But that suggests that this tremor pulse is in fact quote weak one. Copyright of this picture belongs to Icelandic Met Office.

Harmonic tremor pulse can be seen on this SIL Rjúpnafell. It is more stronger signal then on Álftagröf, so it suggest that the source of this tremor pulse is closer to this station then on Álftagröf. Copyright of this picture belongs to Icelandic Met Office.

All pictures are from 16:28 UTC on 12. June 2011.

On other station around Katla volcano I do not see this harmonic tremor pulse on the Icelandic Met Office on-line tremor chart. But that does not mean that it this tremor pulse is not being detected on other SIL stations around Katla volcano.

The source of this tremor pulse is most likely an dike intrusion at great depth inside Katla volcano that is taking place without any earthquake activity. This has happened before without resulting in an eruption from Katla volcano (besides the event in the year 1999). I do not think that this means an eruption is going to happen soon. But this might signal that Katla volcano is about enter an more activity phase then in last few decades. But if that is going to turn out that way is something that only time can answer.

100 Replies to “Harmonic tremor pulse in Katla volcano”

  1. And to be really helpful vedur.is and hraun.vedur.is/oroi seem to have given up working for me!

    1. This might just be the connection to Iceland. I did notice that while in Denmark that the connection to Iceland can sometimes be a bit odd one. I do not know why that is.

  2. Jón can you pinpoint the harmonic tremor pulse exactly (by drawing them or stating them otherwise, ie. by time) as I’m not sure I am looking at the same things as you are. Just want to be sure I’m reading this right.

    1. It is the spike at the end of the Lagu Hvolar tremor plot. It stands out from the rest of the background noise (is above it). Other spikes are most likely minor earthquakes that the SIL system is unable to locate with the automatic system.

      1. Just normal background noise. There might be one or two earthquakes on there (spikes). But nothing else can be seen on this tremor plots.

      2. Hmmmm I thought Mið-Mörk looked peculiar, it was totally flat before

  3. Jon, I just wanted to say thanks for all you’ve taught me so far. I was looking at the tremor graphs, and spotted the increased harmonics at Katla, then logged on to your blog to find you had put up a new one about tremors in Katla.

    Even if I know very little, the little I do know is thanks to you!

  4. Jón:
    Donate button is working fine for me. 🙂
    Only hope that, if Katla is going to erupt, she “waits” in line. Chile’s ongoing eruption is keeping us busy. Then there is Etna and maybe Popo or Nabro (Ethiopia).
    Don’t want to miss one second from any of them. 🙂

    1. Thanks for letting me know that it did work without any problem. This is an new account with PayPal. There should not be any issues. But if they are, please let me know about them.

      Thanks for the support. 🙂

  5. Something different: I have been again in the Krýsuvik area again after some time. And there is definitely more activity in the geothermal areas, especially the one which is located directy south of the lake. The lake went back quite a lot, so this seems to go on. There is one area which is especially active, I think here is hot steam coming up, leading to loud noises on the surface. I can show some pictures later on, if somebody is interested.

      1. Thanks Chris for those images.

        What has the water receded so far in a relatively short time? Is the ground hot enough to evaporate such a volume? Or has the water simply receded down through cracks and crevices in the ground as a result of all the small earthquakeswarms?

        It definitely seems that and eruptive event is on its was as magma is definitely getting closer to the surface heating things up. Give it a few years..;-)

      2. I’m guessing inflation. As the earth rises in one area near the lake, the lake sloshes away from that area.

      3. You realize that the inflation at Krysuvik is only in the term of centimeters? I highly doubt that is the cause.

      4. Amazing pictures! Thanks a lot! Fascinating how this new mudfountain appeared. Is it really a fountain or more like a geyser? (with intervals between eruptions)

      5. Its more a fountain. BTW: On these images you can see some summerhouses in the background. They were built on the beach of the lake a few years ago.

    1. Dear Chris,

      Please do! I’d like to see some photo’s! Especially because I’m going to visit Iceland for 3 weeks and have also planned to see the increased geothermal activity at Krýsuvik.
      Thanks in advance!


      1. I linked the gallery above. Go there, its worth it. The “new” geothermal area just south of the lake is easy to find – just follow the steam column.

      2. Great pics Chris, love the mud fountain! For some reason i’ve never been to this area.

  6. Jón, I have to disagree slightly with your interpretation. The pulse or spike is apparent on many stations surrounding Katla/Eyjafjall. On two of the stations you quote, Altagróf and Rjúpnafell, it is more of a continuation of other activity recorded by these stations.

    On two stations the spike looks a bit out of the ordinary where Lagu Hvolar reaches an intensity of 3000. But the spike is most intense reaching 4000 at Godabunga. Furthermore, Godabunga differs from all the rest – and its usual activity – in that the spike peaks in the low frequency, 0.5-1 Hz or red. The intensity of the spik as recorded at Eystri Skogar and Mid-Mork is also greater than at Lagu Hvolar

    This suggests, to my mind anyway, that the most likely culprit is the Godabunga cryptodome, not Katla, and if you look at the tremor plot for Godabunga, there have been several similar spikes in the period.

    As I have neither your experience nor access to the kind of computer software you do, I will take your word for it being a harmonic tremor pulse, but not one in Katla. To me, a harmonic tremor pulse in the Godabunga area is far more interesting – provided it is an unusual occurrence of course!

    1. Correct me if Im wrong but isn´t Godabunga a part of the Katla system?

      1. If you go to www2.norvol.hi.is and look up the paper on Katla and Eyjafjallajökull, they say that Godabunga is part of the Eyjafjallajökull system and not Katla.

        I can understand if people (and especially news agencies) are more interested news that indicate that an eruption may be due in “the big, dangerous” Katla. However, this is what Erik Klemetti refers to as Katla-mongering and should be resisted. 😉

      2. Absolutely. I am all for suppressing Katla-mongering and will take no part in it. However it does seem that the magmatic features beneath this area is shared between the two.

        And since magma might be coming from the same source which one is feeding Godabunga? Eyjafjallajökull or Katla? I believe I read it at Erik´s blog some while back during Lady E´s “stomach flu” (might be wrong) that Eyjafjallajökull is supplied with magma originating from Katlas plumbing system.

    2. There was no special activity in Goðabunga yesterday. I did check. There was just normal background noise from the glacier.

      I do not have access to any special type of software or hardware too see this. Besides what I own as an armature hardware and software. I just use Icelandic Met Office web page.

  7. I only want to say thank you to Jon ,for giving this blog to all those, who are interestested at volcanic developments worldwide ,especially the icelandic ones, and I also say thanks to all the blog -visitors giving their kowledge, their pictures and ideas,- i can learn more and more this way.

  8. On these tremor graphs what does a negative valued tremor measurement mean?

    1. Is there a another spike happening now or a continue spike on the tremor readings from weather affects?

      1. Spikes are most likely earthquakes or ice-quakes. It is hard to know for sure until IMO check them out if they can do so. But this events might not appear on enough SIL stations to be located properly.

      2. Spikes are most likely earthquakes or ice-quakes. It is hard to know for sure until IMO check them out if they can do so. But this events might not appear on enough SIL stations to be located properly.

        Weather effects appear as the long period up-rise and fall on the SIL tremor chart.

    2. IMO, this giant is no longer sleeping. Its on the verge of being awake and there are no signs it is falling asleep again. Time will tell, but as we continue in the warmer season, I’m looking for an eruption.

    3. They have been recording smaller earthquakes because there are more SIL stations around Katla volcano now.

      But regards to the tremor. Besides what did happen yesterday, nothing else has happened. But there is an lot of background noise on the SIL stations around Katla volcano. That is not be confused with actual harmonic tremor. As that goes above the background noise when it takes place.

  9. Interesting, Very Interesting… 🙂

    Is Katla now on half green half yellow alert or just yellow alert, I had a look and does not look like it is. Not on the Katla-mongering ship,

  10. I just returned from a big trip on the south (Iceland). We traveled around Hekla, Eyjafjallajokull, Katla, Laki and Grimsvotn. Interestingly, I noticed today, as we drove back to the west, along the ring road, that there was a strong smell of smell coming from the river flowing from Solheimarjokull, an outlet of Katla glacier. Well, on this river you can always feel the smell of sulfur, but this time the smell was especially stronger than usual.

    Maybe its my nose, or maybe there is increased geothermal activity under Myrdalsjokull. What do you think Jon?

      1. You never smelled sulfur there?

        Everytime I have drove in N1 ring road, whenever I pass by Solheimarjokull (on its river), always smells of sulfur. But I only live in Iceland since May 2010.

        Today the sulfur smell seemed stronger. Could be because the wind was northernly, thus carrying more smell along the river that flows south.

        The activity in 1999 in Katla, was a possible minor subglacial eruption close to Solheimarjokull.

      2. No, I didn’t. But I was probably there at the wrong time (in the summer, when a lot of meltwater comes down) or so. But I don’t doubt that this exists.

    1. Stronger sulphur smells where reported before the 1999 year event. So this is worth taking notice of. But it is important to know dates when it comes to documenting changes like this one.

  11. By the way, speaking about Katla activity, another information on Eyjafjallakokull: Yesterday as we drove in the south, the sky was completely clear over the top of Eyjafjallajokull, Myrdalsjokull (Katla), and even Hekla: something rare for Icelandic weather. And there was no steam column rising from Eyjafjallajokull. For those not in Iceland, Eyjafjallajokull has been having a little bit of steam coming from the main crater since the eruption, visible when you are close to the volcano (such as my house). Not on every day, and in some days more than others.

    Yesterday, I could not see any steam coming out from there (and there was no wind). So, the temperature in the crater is probably lower now than during last weeks, meaning decreased activity.

    Also, over the top of Hekla (because we were only 2km away from the volcano), was completely normal. Just the normal non-snow patch on its top, because the ground there has been still hot since last eruption.

  12. It is confirmed that Nabro, a long dormant volcano (with no confirmed Holocene eruptions) has started erupting today in Eritrea.

    Here are links to news and geological websites, confirming that eruption. It is also visible in Sat24.

    The volcano has two calderas, one 5km wide, another 8km wide.
    Height of plume is 14 Km high, so apparently taller than the Chilean volcano, but still lower than Grimsvotn last eruption.

    1. Relying on the VAAC reports/forecasts, and whatever error that imparts, the initial stages of the Nabro eruption have it on a path (if it keeps it up) to easily surpass the South American volcano.


      Remember that this calculation has an error factor of four, high or low.

  13. Yes this eruption seems slightly bigger than the Chilean eruption.

    But also slightly smaller than the last Grimsvotn eruption.

    All eruptions had columns 10-20km high, and are about VEI4 in intensity scale

    (VEI1 being Fimmvorduhals in Iceland in March 2010, VEI4 being both Eyjafjallajokull and Grimsvotn eruptions, VEI5 being Katla eruption in 1918, and VEI6 being Bardarbunga in 1477, or Laki)

  14. Irpsit:
    I envy this your trip. Someday I plan to visit this beautiful country.
    Let me ask you guys a question about “sulphur smell” – do you refer to the typical “rotten egg” scent we all no too well, or the intoxicating SO2, which has a different quality to it? How about elemental sulphur? How does it smell like?
    I am asking those questions because I think I have felt a funny smell twice here in Rio, especially when winds were blowing from the South, and I thought it could be from the Chilean volcano. This morning (around 7:30) the light was so funny, the sun was high in the sky and the weather, though clear, had this funny grayish-purple hue and I could slightly feel this smell again.

      1. The intense steaming on the geysir web cam seems to have to have stopped (as at 9:50pm) but i did see a tourist get a good drenching (hope it wasn’t still hot)! 🙂

    1. The typical sulphur smell which is reported by people is the one of Sulphurdisulphid, which is also highly toxic. SO2 is more a sharp smell. And I guess what you describe is caused by volcanic ash, this sounds pretty familiar for me.
      The steam in Geysir depends on a number of factors including humidity and temperature. Sometimes its like inside a washing house there.

      1. How about that!
        And I thought I was so far away from any volcanoes that I wouldn’t ever live to see this.
        Exciting, though, after this long journey tracking volcanoes since Eyjafjöl’s eruption.
        Many thanks, Jón and Chris.

      2. Even funnier if you think that Puyehue’s is among the few volcanoes I have seen from close. I was right there where the lahars hit and damaged the road at the border.
        BTW: Sunday, on TV, they showed a Brazilian journalist diving into Þingvellir fissure with the classical scene of him touching both continental plates.
        I’ve got many calls from friends who think I am crazy because I like such things.

      3. I think you mean dihydrogensulfide (H2S) which is indeed highly toxic, very low concentrations could already be deadly, and not sulphurdisulphid which should be S3 or something 😛

    2. Here in Iceland you could not smell any sulfur when Grimsvotn erupted and I was about 100-150km away from the volcano, and the wind blowing exactly from there. I don’t think you can smell the volcano from Chile in Brazil! Neither people in Scotland could smell Eyjafjallajokull! At least not the average nose! But I have a good sense of smell and I could not smell it.

      However, you could smell the ash in the air from the eruption, 150km away, everyone could. It was a ash/burnt/rock/earthy mix of scent.

      Sulfur smells the typical rotten eggs. I always smelled the same familiar sulfur smell in Iceland in many places, in my shower, in Fimmvodurhals volcano, in other volcanoes, in hot springs, in the Blue Lagoon, …

      1. and under the shower at the camping in Rekjahlid (Myvatn) as well as under the shower at Reykjavik camping! But the water at both places tasts good!


    3. Renato, you should come to Iceland.

      You will learn much more about volcanoes, and know more easily what is normal and expected to find and see in Icelandic volcanoes. The best time to visit the country is in summer months, but the weather is always rather cold (“fresh”) here.

      1. Renato,

        Go to Iceland, spend a few weeks there. I did, you just have to do it.

      1. Over the past year, I’ve become more and more convinced that there is one or more active hydrothermal fields (such as at Geysír/Strókkur) under Mýrdalsjökull, one of which ought to be close to Godabunga. This would explain the continuous activity shown on the Godabunga SIL station and occasional increases on nearby SIL stations such as the one at Lagu-Hvolar.
        (Caution – Rank amateur opinion)

      2. The existence of geothermal activity under Myrdalsjokull is well known. That is buried under deep thick ice, as thick as 600 meters. However, sometimes the heat is enough to melt some ice and cause big depressions on the ice (such as it happened in 1999).

        When the weather is clear, you can even see these “holes”, more depressions, on the ice cap over Myrdalsjokull, from the ring road (from Myrdalsandur). The shape of Katla becomes also apparent from there.

        There are some scientific papers on this, you can find them on the internet.

        This activity is normal and continuous and seen at other volcanoes, whether covered by a glacier or not. You can see this in person, if you hiked Torfajokull to the north, in Reykjanes (Krisuvik) and Hengill (close to Reykjavik), in Askja and Krafla in north Iceland, around Langjokull, and in Kverfjoll and Grimsvotn, under Vatnajokull. The same activity is also normal and present in Katla under Myrdalsjokull ice cap.

      3. Thank you Irpsit! Yes, I have read those papers. I was more thinking on the lines of subglacial Geysírs and Strokkurs in order to explain the peculiar appearance of the tremor chart of Godabunga SIL-station. As usual I didn’t explain myself clearly, sorry.

  15. Just wondering is the camera at katla not working? i havent been able to link on to it after work was happening to it

    1. Most likely I was wrong again. It just looked like those clouds were steam coming from Hekla.

    2. Hekla will not wake up nicely (steaming), it will wake up quickly andf very angry (the plinian way).

      1. Anyone have any ideas of the quality of a Hekla erution such as gas content, ash composition/courseness, VEI?

        I’m going to hunt down some research to gauge the scientific consensus

      2. Hekla produces basaltic andesites, VEI normally around 3, often starts of very powerfull, but rapid decrease within hours. Normally an effusive eruption starts after the explosive phase.

  16. I am now back with my main computer. So updates should be more frequent from now on. I have also moved the webicorders to the main computer for earthquake monitoring that I have. That is why the last 24 hour is missing from the webicorders.

      1. @Renato Rio, I know that I am born in Iceland. But for more Denmark feels more like home. Specially Copenhagen. I do not know why that is.

  17. Thank you everyone for your very helpful observations. The only experience I have had of volcanic activity and the smell of sulphur was in the Cauldera of Sulfatara in Italy, near Pozzuoli on the bay of Naples. Here there were many fumaroles and in the centre boiling mud. The smell was strongly suphurous but not just the “Rotten egg” smell. If anyone is going to Italy I recommend a visit here. It’s fascinating.

    1. This is probably due to the storm-noise which prevents earthquakes being picked up by the system.

  18. Hekla,s RUV webcam is being hardly hit by ashes remobilized from Grimsvötn. What a nuisance!

  19. Guys, no eruption in Iceland will start with a volcano steaming.
    Please stop saying that “Hekla is steaming”, “Katla is steaming”.

    Clouds hang around the top of this snow-covered volcanoes almost every day, and when wind blows, they often form at its peak and are carried away, in what looks like a steam plume. Webcams only serve to show a future eruption, nothing else!

    And if you see Eyjafjallajokull steaming, that is very normal, the crater there is still very hot, and it will remain like that for several years. Steaming only happens AFTER an eruption, not before. However, a strong smell of sulfur can be detected a few hours before an eruption, but only close to the volcano.

    1. This is not completely true, steaming can also occur when hydrothermal activity increases beneath ice. However that could never be the case with Hekla.

      1. The glaciers which cover active volcanoes are usually quite thick. So you wont notice steaming until the ice has a hole and this will not happen until an eruption occurs. Even for Grimsvötn, which has melted the ice above the volcano nothing like this is reported.

      2. I know. The lake there is included in a description of geothermal pools in Iceland where you can bath 🙂
        But there was no report of increased activity before the eruption, if I remember correctly.

      3. But the possibility of increased geothermal activity before an eruption is possible, and the fact that this could result into more vapourising is also possible.

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