Posted on by Jón Frímann

Glacier flood subsides, harmonic tremors drops down

According to the news the glacier flood from Grímsvötn is subsiding and is expected to be over in the next two to three days. At the same time the harmonic tremor that started at 3rd of November 2010 is also subsiding. No clear reason is for the harmonic tremors.

Currently there is nothing that indicates that a eruption is about to start in Grímsfjalli. But that can change with a short notice, as Grímsfjall sometimes does not give a long warning before it starts erupting.

Icelandic News. Please use Google Translate.

Farginu létt af eldstöðinni (Vísir.is)
Hlaup í rénun (Rúv.is)

English news.

Flood waning, Iceland volcano eruption less likely (washingtonpost.com) – Thanks to Erik for this news.

95 Replies to “Glacier flood subsides, harmonic tremors drops down”

  1. Well, here goes my crazy theory.

    What has happened? Ok, magma rises up to the surface (tremor appears), cracks open. Heat and gas is released through this cracks. That heat makes the glacier to begin a melting process, what makes a huge amount of water to be discharged (2-4 Hz tremor). But part of the water follow a different path. Some of the water enter the cracks. More pressure added to the system (more tremor). And something unbealievable happens. Part of that water, unable to be discharged acts as a lubricant for part of the glacier, that starts creeping (sudden leap on tremor) and that creep makes the whole volcano to start a resonance (harmonic tremor inducted by an ice mass). The discharge reaches its maximum, as well as the tremor. Then the discharge of water begins to ease, then the creep stops, then the resonance gets weaker, as the tremor do. And here is the end of the story by now. Magma rises but does not reach the surface (absence of swarms), even is able to release heat and gas to melt the glacier….

    That´s what i think it can happened, but remember, just my theory….;)

    1. Grímsfjall had a failed eruption in March 2010. So that might have been a factor on why it did not erupt now. But nobody knows what the factors are for the eruption to start and take place in a volcano.

      So this is all just a guess work.

      1. I still remember the 2004 crisis at Teide volcano. We also had tremor, and things were scary up there, but in the end nothing happened, in fact nothing happens 90% of this kind of crisis…

  2. Would guess the tremors occured due to pressure release due to the glacier flood. Nothing dubious about that. Still there will probably not be long wait for an eruption

  3. Just got back from the Eruptions blog-Things are not good with Merapi..
    Calm here is good calm there not so good…

  4. What the heck is happening to the Merapi tremors? It kinda looks like an abstract piece of art by Mondriaan now haha.

      4. Still thundering sound Coming from the Slope

        While Hamlet Gronggong, Cangkringa, now still being carried out evacuation of dozens of trapped victims, either in a state of dead and wounded. Evakuasi dilakukan tim Kopassus, Brimob, Tagana, dan relawan yang bersiaga di Kepuharjo.(*) Evacuation by a team of Kopassus, Brimob, Tagana, and volunteers are on alert in Kepuharjo. (*)

      5. Correction:

        Still thundering sound Coming from the Slope

        Tribunnews.com – Friday, November 5, 2010 7:13 pm

        Sound rumble expected from avalanches of volcanic material Merapi still be heard sporadically from Balerante region, Kemalang, Klaten, Friday (04.11.2010) this morning at 6:40 pm.

        Sujiwo, residents Balerante preaching via radio communication, the visual area of the mountain peak is not visible due to thick clouds blanketed. While the seismic data, seismic frequency detected is still quite high although not sehabat the previous day.

        While Hamlet Gronggong, Cangkringa, now still being carried out evacuation of dozens of trapped victims, either in a state of dead and wounded. Evacuation by a team of Kopassus, Brimob, Tagana, and volunteers are on alert in Kepuharjo. (*)

      4. Lurking made a ‘tautological’ pun. It was *very* good. 🙂

        All four of them have been in full-on roar mode since yesterday.

        Frozen in full roar mode

        Links were provided so that could all change.

  6. By the way, I’ve always been wondering, to which volcanic system do the earthquake (swarms) that occur near Upptyppingar belong? Thanks

      1. Well that was my first thought too, but as you can see here:
        http://en.wikipedia.org/wiki/File:Volcanic_system_of_Iceland-Map-en.svg
        The Askja volcanic system runs from SW to NE. So in that case i’d rather say it’s in line with Kverkfjoll as I tried to show in this small map:

        http://img13.imageshack.us/img13/7573/uppu.jpg

        The red dot is Askja, the green one Upptyppingar, and the blue one Kverkfjoll.
        The problem with the Kverkfjoll idea is, is that most maps of the volcanism in Iceland suggest that Kverkfjoll doesn’t reacht that far north. Plus there has been a lot of seismic activity at Upptyppingar and there has been little at Kverkfjoll.

      2. I get your point…but fact is that eq are not happening at Upptyppingar, but 4-5km south than Herðubreiðartögl mountain. Upptyppingar is further to the east.
        And also similar swarm happened before in this year near Askja volcano

      3. I’m not especially reffering to the recent activity, there have been major swarms beneath Upptyppingar.
        I just found this article (http://www.springerlink.com/content/q9274tj322410621/) which states that it indeed is a part of Kverkfjoll. But then still, why has there been so much activity at Upptyppingar and close to none at Kverkfjoll central volcano?

    2. That would be Kverkfjöll volcano. But the earthquakes belong to a magma intrusion in area into the crust. However this is inside Kverkfjöll volcano fissure swarm.

  7. Well i still think that swarms under or near Upptyppingar reffers to Askja.
    And i just remember that wee speek about Kverkfjoll volcano on this bloog not long ago.
    http://icelandgeology.net/?p=70

    And i guess we will have to wati for Jon to answer theese questions, he would probably know better these things 😉

    1. Jón: I noticed that too. I think it has nothing to do with the jökulhlaup, but this is volcanic tremor, only that it is fluctuating now. My guess.

      1. The glacier flood is over or almost over. I don’t think there is anything flowing down from Grímsvötn at the moment. But there might be some water in the channels under the glacier at this moment.

  9. I really have nothing to add about Volcanoes, other than have had a recent fascination with them. But I do want to say that I have been reading Jon’s posts for the last month and I’ve enjoyed reading the bantering back and forth, the information that is so freely shared. Heck, I might even learn something here lol (ok we might not push it that far lol).
    So This is my thank you. Keep it up. I do enjoy reading the main posts as well as all the comments.

    1. Far as I know there is not any connection between Grímsfjall and Hamarinn volcano. But Hamarinn is active on the earthquake side of things. It last erupted in the year 1902 far as I know.

      1. There was one quake at each volcano. I’m just waiting to see if a swarm would develop.

    2. Directly… probably not. But referring to the gravity anomaly paper (Gudmundsson 2006) he indicates that these systems can share magma via intermingled sills, though they are not directly connected.

      From: “The Puzzle of the 1996 Bárdarbunga, Iceland, Earthquake”

      http://rses.anu.edu.au/~hrvoje/Tkalcic_etal_BSSA2009.pdf

      “A sequence of earthquakes commenced 29 September starting with a magnitude 5.6 earthquake in the Bárdarbunga volcano (Fig. 1).
      Similar earthquakes had occurred in this area previously. Ten earthquakes clustered around the Bárdarbunga caldera are reported in the Harvard Centroid Moment Tensor catalog for the period 1976–1996 (Nettles and Ekström, 1998). However, this time the event was followed by a swarm of small earthquakes that migrated toward a neighboring volcano, Grímsvötn, and culminated in a subglacial volcanic eruption”

      And, if you refer to a plan view plot of the Hamarinn – Grimsvotn area, you can see an arc of quakes that has occurred since 7/17/10 that tracks along a loose arc between the two.

      http://i54.tinypic.com/vx24pi.png

      Not saying that it’s so, but there is a possibility that there has been a mingling of magma between the two. But other than that, no, they aren’t connected… piping wise. Gudmundsson 2006 seems to indicate that the pairs sharing the same dike swarm can be considered connected. For Hamarinn that’s Bárðarbunga (the dominant volcano), for Grímsvötn (dominant in its dike swarm) it’s pair is Tordarhyrna (the sibling).

      But this is just from reading material. They aren’t connected… but they can leak into each other’s system.

  11. Tremors started to increase again, like Henrik expected.

    It seems we have followed the 2004-track pretty closely. Which means, Grimsvötn should erupt today or during the night (IF the trend continues along the track).

  13. One thing I’ve learnt over the past year is that vulcanology is such a complex science that even the most learned vulcanologists rarely dare make predictions more than a few hours ahead of an event as they usually turn out to be more or less inaccurate.

    Daniel’s theory – the hlaup has released pressure which has allowed the volcano to expand again, therefore there will be an (apparent) drop in activity – is a good one, but the opposite might be equally true: The pressure from above acts as a reinforcement of the fragile crust. When that support is removed, the surface cracks and there is an eruption. Either hypothesis – or even a third: the pressure of the glacier has no influence on the timing of eruptions – can be made to fit the observed data. Even if Daniel’s theory seems to be the best current explanation and future development will make him appear to have nailed it, it may just be coincidental all the same.

    That said, I like his hypothesis!

  14. Here is one just to prove the point that things can be confusing. Remember that this has nothing to do with a volcano at all. At least not one yet existing (this is Iceland after all).
    You can get decreased tremor measurements at the same time as you have a nice increasing swarm in an unexpected place (Krisuvik).

    First the tremor-measurements. They have fallen with 50 percent during the same period that we have a nice pulsating swarm pattern of quakes in the exact same area.
    Tremors: http://hraun.vedur.is/ja/oroi/kri.gif
    Quakes: http://en.vedur.is/earthquakes-and-volcanism/earthquakes/reykjanespeninsula/

    This is probably all hydrology-induced activity since the lake of Krisuvik is a bit strange since it was cracked by a large quake and now looses water at a leasurely pace.

      1. You can change your nickname after logging in. Only your login name cannot be changed, although your the only person to use it.

  15. I noticed that, but still having a lake that is refilling after having emptied out is probably what is causing the quake-swarm. We are after all talking about big mac-sized quakes here:)
    But it is still fun with a quake-swarm that exists at the same time as the tremors are falling.

    1. It hasn’t really emptied out – I think it lost something around 20% of its volume. Something you notice on the beaches, which are getting bigger but only, when you know the area pretty well. There are some reports about new hot springs next to Kleifarvatn, I hope I will have some time in the near future to visit them. This area is pretty active. There is also a solfatara field close by, Seltún, which got more active in the last years.

  16. Yes, after all it among the most geologically interesting spots on the planet.
    Actually you could see the lovering of the surface quite easilly, at least back when I was there.

  17. Anybody notice that is steady inflation upward going on at gps stations near Katla volcano? Is that normal or that indicate that Katla is going to become unrest at some point in the future?

    1. It is business as usual at Katla, and that business is as always to get ready for the next burp. When she burps is the question, not if. The same goes for Askja, Grimsvötn, Hekla, Krafla and Bardarbunga. I have probably forgotten a few others. Or it might be an unextexted volcano like Eyja, or an entirely new one. This is why I love Iceland, all you have to do is sit down, drink a beer and just wait for the next big *boom*:)
      I would though say that she is making progress towards the news headlines sometimes within the next five years.

      1. Yes I know it will eventually erupt at some time, probably even in near future 🙂 (few years maybe). But from what i see, Katla’s gps stations shows biggest inflations upwards, than any other volcano in iceland currently (except of Grimsvotn). But as i’m not watching volcanoes in Iceland for long time (or volcanoes at all), i didn’t know it that inflations normally happening with that rate, at Katla, or has just begun in past year or two.
        I hope that you guys who have more knowledge in volcanoes that i have, (i didn’t even know that tremor is or stuff like that before april when i first found old eruptions blog, and then volcanoes-specially iceland ones-started to interested me)
        don’t mind if i ask from time to time few, for you ”stupid” questions 😀

        PS- you wouldn’t even believe what i do for a living 😉

      2. I just took a deeper look at Katla and nothing really seems to be out of the ordinary there. Infation progressing nicely, no tremors really, and no quakes.
        Here is a good page for Katla:)
        http://hraun.vedur.is/ja/Katla2009/

        I have given up on guessing what people do for a living.
        I myself is a physicist thats gone corporate and retired early… Well, semi-retired… hm… well, trying to:)

  18. All active volcanoes have an Up trend. It is their nature when magma pushes from beneath and then eruptions occur and the mountain deflates. Its like mother earth breathing just that each breath takes a very long time. 🙂

    Katla will erupt for sure. When is a good question that i think noone can really answer. The inflation at Myrdalsjökull is a part of the cycle. But there are no signs of extraordinary inflation, tremor or any type of activity.

    I believe Jón said once that when Myrdalsjökull gets hit by mag4.0 or mag5.0 earthquakes its time to start looking at Katla to erupt.

    1. You forget that Katla and Hekla are beer-volcanos. All they need is a beer to get going, and the only warning you get is the popping of the can.
      Ie, they give scant or nor warning about an hour before they go *boom*
      Pretty much if there is a warning sign and you are ontop and don’t have a helicopter in you back-pocket you will need to sprout wings on your own to get away.

      1. Another metaphor might be that they are both professional drunkards with beer-filled stomachs ready to barf in an instant.

        Ie, their throats (conduits) are conctantly clear and ready due to them erupting so often, and they are always having well-filled magma-chambers. The rising is pretty much just some topping off in the system.

      2. Haha good analogies Carl. Hats off to you. 🙂 But what you say is true..The conduits are probably quite clear due to alot of activity. But then the large EQ theory becomes even more plausible.

        If magma has an easy path it rushes upward faster and when it meets the top it will produce a very large shake due to the sheer inertia and pressure i would assume.

        And here you got yet another point. if this is how it would be there would indeed be less pre warning before she pops her top.

      3. Yepp, I totally agree with you.

        Same theoretical ground that makes professional drunkards being able to hurl so far:)

        In this case you just need one 4 – 5 quake to break up the “throat” and thar she blows.

  19. And since I am going for a few beers this weekend here is a good name for the next new volcano cropping up in Iceland.
    Rautthraunbrýturöllmálefniskera, that what kill newscasters all over the globe…
    Sorry if it is not grammatically correct;)

  20. Haha Carl you made me laugh at that one. 😀

    I can picture the newsreaders trying to get their heads around that one.

      1. Well in swedish the name isnt much easier to read out. Good thing we dont have any active ones. 🙂

        “rödlavaharsönderalltklippan”

        😉

      6. :o)

        There is an old joke in Finland: When all people die and arrive to Heaven, only Finnish is spoken. Why? Because, it takes forever to learn it!

  21. Nah, but we should probably try to start one for tourist reasons.
    I think the best place would be that large fracture zone called Schläppträsk. You know just south of Lapplands-Väsby… And there I just proved the point that noone english speaking can pronounce anything nordic at all…

  23. Looks like the tremors over at Grimsvötn have stabilized at a new plateau 50 percent above normal level (background noise). 24 hours at that level and counting.
    My take is that the high level before was half water running and half volcanic tremor, and now only the volcanic tremor is left.
    If it follows the pattern for the last eruption it should start sometime between tonight and sunday. But this is just hyberbole on my part.

    1. Yes I had a theory in the last post regarding the pattern of the tremors and recent activity. Lets see if it play out..

      However if i have learned one thing about volcanoes it is that they cannot be predicted. More than one time i have been surprised by a volcano NOT erupting when all signs pointed at an eruption and vice versa…

  24. Tremors seems to be subsiding a bit now…Maybe this was just Grims way of saying “Gotcha!”

    1. Nja, not subsiding, it just dropped of a couple of percent really. I would say the volcanic tremors are still in full swing and it is just the lack of large masses of gushing water that makes us believe that the volcanic tremor is down.

  25. @ Jón – Is there any reports about magmatic intrusion beneath Torfajökull? I saw an EQ today at over 5km depth. It last erupted in the 15th century and since it is a rhyolithic stratovolcano it can be a nasty piece of eruption where it to happen in our lifetime.

    1. Far as I know everything is quiet there. But there is a increasing earthquakes happening there. But that has happened before without anything special happening at Torfajökull volcano at current time.

  26. I´ve seen it manny times, and wonder what´s up at Grimsey.
    These swarms over and over again, is this normal?
    Great blog Jon!
    And great job everybody in digging for info!

  27. Friday
    05.11.2010 21:11:45 64.500 -17.469 1.1 km 2.3 90.02 14.2 km NW of Grímsfjall

  28. The “swarms” at Grimsey are normal…Bear in mind that Iceland is on top of the mid atlantic ridge. It means alot of creaking in the fracture.

  29. Ok tanks Daniel!
    One at grimsfjall now, wonder if that gives more.
    But treamor dosen´t show anything.

  30. No Tremors at Grimsfjall is actually starting to reduce to normal levels. Maybe it was just a failure at one of the containments..

  37. Electrical
    conductivity has increased to 560 μS/cm
    (From Iceland)

    I do not know what this is or what is going on with this.. Can you please explain..

    what would this have to do with an eruption, and what could they possibly figure would be happening as far as an eruption is concerned..

  38. @Shane Johnston

    Electrical conductivity is the inverse of resistance. (unit is the “ohm”)

    Siemens are the SI unit for conductivity. Old school used the term “mho”

    As acidity goes up, conductivity goes up. (and resistance goes down)

    Siemens = 1/ Ohms
    Ohms = 1/Siemens

  39. As for what it has to do with an eruption, if there is SO2 or H2s being released, when it mixes with the ambient moisture it forms an acid. (H2SO4 for example). So, if the conductivity is going up, more volcanic gases are being released.

  40. Were I a brown trout, I’d consider becoming a salmon so I could migrate to another river. Pesky volcano.

  41. Sort of reminds me of when the grandkid was hunting easter eggs. He found one that had been placed there a year earlier. It popped. He ran. It stank.

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