Posted on by Jón Frímann

Grímsfjall volcano inflates after the large May 2011 eruption

It can be sad that Grímsfjall volcano did not waste any time starting to prepare for next eruption after the large May 2011 eruption. But that eruption was the largest one in at least 140 years or so. This large eruption did mean that there was a large deflation that took place during the eruption. Where the most deflation was around 250mm down, and around 300mm north, and around 350mm east.

Since then Grímsfjall volcano has however been inflating at interestingly high speed. Currently the GPS data shows that it has reached around 250mm east, north and 200mm up since the eruption. But the magma chamber is going to expand horizontal before it expands upwards (think of this in 3D). So it is going to be a while until a inflation upwards is going to be seen.

The GPS data is clear on this as can bee seen here.


Current inflation at 27. July 2011. Copyright of this picture belongs to Icelandic Met Office.

It is hard to know when Grímsfjall volcano is going to erupt next after this big eruption. But it might take few years until we see a new eruption in Grímsfjall volcano.

43 Replies to “Grímsfjall volcano inflates after the large May 2011 eruption”

  1. Jon, might the movement there on the GFUM GPS plot be from the gound slowly returning towards where it was before being shifted a large amount by the Grimsvotn eruption?

    That sort of slow rebound movement can be seen on most of the Eyja GPS plots post eruption, for instance …

    http://strokkur.raunvis.hi.is/~sigrun/THEY.png

    1. It is inflating, so it is filling up. Current status is the result of loss of large amount of magma.

      Eyjafjallajökull volcano was different, as there was a inflation spike before the eruption. This is long term inflation before a eruption in Grímsfjall volcano.

      1. Jon, does this plot show motion relative to Reykjavik? If so, it isn’t detrended and would include the motion on the east plate relative to the west plate?

      2. Far as I know all GPS stations in the GPS network that IMO runs are relative to Reykjavik. At least that is what they say on there web page about GPS network.

  2. Having seen these odd earthquakes around Hekla last night, I thought I would read up on Volcanoes other than those under Myrdalsjokull .This paper may be useful to read to remind us of suggested magma chamber sizes and depth .
    I found it quite fascinating and may suggest reasons why Hekla gives little warning of eruption and it’s non relationship with nearby Torfajokull .
    The paper has emphasised the complexities of trying to predict behaviour for the Volcanoes in the South Iceland area, Even those within a few Km of each other may not share similar properties.
    Maybe Grimsfjall has not been studied in detail long enough to understand post eruptive behaviours. So more surprises in store!

    http://www3.hi.is/~heidi/Data/Article-richard/SoosaluEinarsson04.pdf

    1. Thanks Diana – this is really interesting and gives good background 🙂

    1. mr Moto ,It looks good butI can’t get the darn zip file to open!!. I’ll have another go later. Are you on Microsoft ? I have Vista.

      1. OOps Sorry Mr Moho! Brain and fingers uncoordinated here this morning!

      3. Nice plot!

        Congratulations on learning gnuplot so fast!

  4. According to the news, a glacier flood is starting in Skaftá river. It is estimated that the glacier flood is going to be in the low land after about 24 hours. This glacier flood has is source in a hydrothermal area in Hamarinn volcano.

    Glacier flood also took place there last summer. I am going to have more details on this later today.

      4. Why would you want one?

        Floods are not entertainment, or not to me anyway. Just interesting to note the geothermal activity. There has been a lot of that already this year.

      6. Helena:

        Interest and understanding =/= entertainment

        I’d be interested to see it.

      7. I LOVE watching the icebergs and the tides going in and out of the lagoon at Jökulsárlón webcam. The narrow (and apparently shallow) mouth of the lagoon has a lot of dynamics going on there – very interesting to witness the interactions. The icebergs look small until you realize they dwarf, many times over, the large vehicles parked on the overlook. I wonder if Katla will affect this area if she goes berserk.

    3. Hmm! Jon , you have been aware for sometime that something has been happening around Hamarrin. Well done for spotting this!

      1. This was in the news. So I did hardly spot it. Last glacier flood in this area took place last year, so they do happen frequently there.

        But if anything more happens now in relations to this glacier flood is a question nobody has a answer to yet.

  5. Hi Helena. Yes, not entertainment but allways interesting. Anyone knows if this one is small or big?

  6. Hi John.
    Do you have any idea about the very regular short period spikes in the tremor graph of ALF are caused by?A spike every 4-4.5 hours for at least the last two days. They are also triggered by alert system but seldom localized. I have used the Fbreaktime to calculate the last 4 events (today 0201, 0612, 1028, 1512UTC) and have calculated with epicenters to be (fixed depth 4km) 63.50-19.09, 63.50-19.09, 63.51-19.10, 63.50-19.09, about 5 km east of the station ALF. All almost at the same spot. Are these man-made detonations or natural, if natural how come the regularity in time?

    1. This are natural earthquakes, and really interesting ones at that. This is not the first time this earthquakes have been seen. I wrote a blog post about them few days back (or was it a week?).

      This earthquake activity stopped for few days. But seems to have restarted again. I do not know why the earthquakes are taking place there. But all clues suggest that magma is responsible for this earthquake activity. How and why is unknown to me at this time.

      1. Let’s see the next earthquke will probably take place between 1910UTC and 2000UTC. The magnitude of the quakes also seem to be about the same.

  7. There it came, the next earthquake at 1849UTC, a little earlier this time but not much earlier. No epicenter automatically calculated. With my program the epicenter is near 63.50N 19.10W almost exactly as the earlier events.

  8. Could Hekla be getting ready for a fissure eruption north of the volcano?

    It looks like Hekla is inflating rapidly again. This time with moderate sustained upwards inflation and rapid southward movement at Isakot located north of Hekla. I guess this is weird on three accounts. First Hekla doesn’t normally inflate or give signs before an eruption, but I guess that mainly applies to a central vent eruption where the path is cleared every 10 years. Secondly Isakot is located north of Hekla so I guess it should move northwards if it was the central volcano the was inflating. Thirdly Haukadalur south of Hekla is not inflating nearly as fast. And then we have had earthquakes north of Hekla recently something I cannot recall to have seen the last year or so where I have been following icelandic activity. I guess we need a lot more activity before anything breaks the earth through a novel pathway but could something be brewing? What do you think?

    http://hraun.vedur.is/ja/gps/predorb/isak_enu_p.png

    1. The movement to the north is indeed interesting but I guess we need to wait some more days to see if it continues, it happened more if you look in the graph.

      Meanwhile earthquake activity in krysuvik area has increased again

      Sander

    2. Really weird data at Isakot GPS station. The sudden (extreme) movement south makes no sense at all. My best guess: data glitch. Can’t make anything else of this. I can’t imagine any situation in which this is related to volcanic activity in Hekla. One because this goes against anything known of volcanoes inflating, and second because of the sudden appearance of such a relatively great movement measured quite far from the volcano itself. (keep in mind that Isakot is still about 15km from Hekla central volcano and about 5km outside the volcanic system of Hekla, so that includes all fissure systems and related volcanic features)

      Interesting developments, Hekla keeps surprising me.

      Oh and it is known for Hekla to normally inflate in the year preceeding an eruption. So that is nothing unusual.

  11. While looking at Hekla and Alftagrof, I’m curious about the continued tremor plot at Skrokkalda (Northwest of Grimsfjall). This station sits out in between the volcanoes, but am I seeing a harmonic tremor on this chart? It’s been like this for some time. Perhaps Jon you could advise on what I’m seeing here. Thanks!

    1. This has been present for some time while no other signs of volcanic activity is observed in this area or the surrounding area. From this we can only conclude that this pattern is most likely not caused by volcanic activity.

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