Posted on by Jón Frímann

Harmonic tremor pulse in Grímsfjall volcano

There have only been seven months since (May 2011) the last eruption in Grímsfjall volcano. But it seems that Grímsfjall volcano is getting ready for its next eruption. Even if the last eruption was the largest one for at least 140 years in Grímsfjall volcano. So far earthquake activity remains low in Grímfjall volcano. But I am not sure if that means anything for the moment. But there has been in earlier lead up to a eruption a build up of earthquake activity in Grímsfjall volcano.

Today at least two harmonic tremors spikes have been detected by IMO. But this type of harmonic tremor pulse have been detected before in Grímsfjall volcano. Older blog posts on that subject can be found here and here. But this time around it seems that the harmonic tremor is stronger then before. Currently it remains uncertain of there is a glacier flood starting from Grímsvötn lake, as was the case last time this type of harmonic tremor pulse was detected in Grímsfjall volcano.


Harmonic tremor in Grímsfjall volcano at 00:21 UTC on 5 December, 2011. Copyright to this picture belongs to Iceland Met Office.


The harmonic tremor in Grímsfjall volcano at 01:39 UTC on 5 December, 2011. Copyright to this picture belongs to Iceland Met Office.

There is a clear change in the harmonic tremor, as can be seen here. But why and what this actually means for Grímsfjall volcano I am not sure. But I am rather sure that this means a new eruption might only be several months away. But it is hard to know that for sure. But I am just base my estimate on earlier experience with Grímsfjall volcano. But it might not mean anything after last eruption.


The GPS data from top of Grímsfjall volcano. The data is missing for the last few days. Must be because of snow and ice. But given the last data set, the change so far it not that great since the eruption last spring. Copyright to this picture belongs to Iceland Met Office.

What happens next in Grímsfjall volcano is a big question. But it seems that Grímsfjall volcano is going to go for a new eruption. When that might happen I have no idea.

33 Replies to “Harmonic tremor pulse in Grímsfjall volcano”

  1. We are ready for the outcome of this.: crazy volcano, Grimsfall…
    Jon. Xmas donation underway.
    Wish you luck!

  3. Thanks for all your infos everytime, finally a source u can look up to stay in touch with latest news about volcano and earthquake activity 🙂

    and i hope this volcano can still wait a few more weeks until i’m done with my to flights to Germany and back to Iceland, would really appreciate this ^^

  5. Thanks for the post JOn. I did ask about the harmonic tremors at
    http://hraun.vedur.is/ja/oroi/esk.gif in the last Blog page. (Diana Barnes says:
    December 5, 2011 at 01:52)
    Surely Grimsfjall could not be causing this? Other SIL stations around Myrdasjokull seem not to be showing the same signals,

    1. Hi Diana – sorry, missed your comment before.
      Agreed, it’s nothing to do with Grimsfall, but I’m also not convinced it’s just weather – over this duration I’d expect to see something similar affecting other stations, like god. The first part of the spiky section probably is weather – it’s also there in the Westermann Islands – but the second half looks more interesting to these completely amateur eyes, irrespective of the weather. It also seems to have just come to a very abrupt stop.

  6. Well, hard to tell if these are due to high winds and sea waves, or if we do have a harmonic.
    But I still think it’s weather related. Amateur opinion.
    Have a good day!

    2. Indeed beautiful with the clear blue frost sky and the horses running around! Completely different compared with my stay there last july! also beautiful weather (warmer!) with me taking pictures at 23:00 hours (local time) with a red glow of the setting sun on Hekla!
      Henk

  9. This could be the lake of Grimsvotn preparing to empty itself. Usually floods follow the eruption, but during last eruption there was no flood. Sometimes this also happens.

    It might be that the lake is now full and could be discharging down the glacier.
    Otherwise could be increased hydrothermal activity, linked to rising magma.

    If we are entering a cycle of increased volcanic activity in Iceland, then it is expected that Grimsvotn might erupt every 2-4 years, besides expecting other eruptions in Vatnajokull.

    It’s -14ºC as of the midday today, and a beautiful (horizon) sunshine day!

    1. The lake emptied itself almost exactly one year ago – I don’t think its already full enough to cause a glacier run. But I might be wrong.

  11. Tremor pulse at Mel SIL station is stil looking like something is going on in its vicinity. Any ideas anyone?

    1. Good for you Jon Frimann!

      Now, with the activity at Grimsvotn, we can get off of Katla for a bit and watch something else for a change. It will be interesting to see what Grimsvotn will do.

  13. Typical! Just when I have cleaned my windows, Icelands volcanoes get restless again!

    Great post Jon and congratulations on the media coverage.

    1. WOW, that is an incredible photo, I don’t often say breathtaking but that one had that effect on me. So very beautiful I almost forgot to breathe. WOW again. I so wish I had been there to experience that. I once had a Finnish friend who wrote of “The marvelous play of light above our heads.” First time I have seen it that spectacular.

    2. I had a look at Stefan’s site. All his aurora photos are awesome! Please go and have a look at them. I might order myself something to hang on the wall from him. What a photographer!

  16. Jon, how does the inflation seen at Grimsvotn prior to eruption earlier this year compare to that seen recently at El Hierro? If I read the above graphs correctly, inflation was in the order of 10 cm – 15cm in each direction.

  19. First-time poster, long-time lurker.
    Jon wrote: Year 1492, eruption starts in Tenerife on ~24 August.
    From Wikipedia: Christopher Columbus’ first voyage to the new world: On the evening of 3 August 1492, Columbus departed from Spain with three ships. Columbus first sailed to the Canary Islands where he restocked the provisions and made repairs. After stopping over in Gran Canaria, he finally departed from San Sebastián de La Gomera on 6 September, for what turned out to be a five-week voyage across the ocean.
    Columbus and his crew certainly must have witnessed this eruption, although the historical record seems to be silent. What a way to start their adventure. 😉

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