Bárdarbunga, Gjálp and Onwards

Gjalp subglacial eruption (3 October, 1996). Photo taken by Oddur Sigurdsson, Iceland Geological Survey. See an airplane in the photo for scale. Photograph and text from http://rses.anu.edu.au/~hrvoje/Bardarbunga.html

Gjalp subglacial eruption (3 October, 1996). Photo taken by Oddur Sigurdsson, Iceland Geological Survey. See an airplane in the photo for scale. Photograph and text from http://rses.anu.edu.au/~hrvoje/Bardarbunga.html

Lately Iceland has suffered a long series of earthquake swarms that have ambled all over the island. Earthquake swarms are common in Iceland, that is not the issue, the problem is that they this time came in a swarm of swarms, all of them containing at least one earthquake above M3. Before we take a look at the latest earthquake swarm between Bárdarbunga and Kistufell we should take a look at the really broad picture of Iceland.

Magmapulse, riftcycle and deglaciation

A few years ago the authorities of Iceland issued a notification that Iceland would soon be entering a period of heightened volcanic activity, these periods of unrest comes at about a 130 year long cycle. One of the explanations given for this is pulses of uprising magma via the hotspot/mantleplume which is centered under Kistufell volcano.

At the same time we are closing in on the time where Iceland is most likely to have a rifting episode. These come with a roughly 270 year interval and are caused by buildup of tectonic strain as the North American plate and Eurasian plate are pulled apart at the Mid Atlantic Rift. The release of this strain is uneven in Iceland and a large portion of the spreading comes in fairly regular intervals. These heightened motion periods are well known to cause large scale volcanic eruptions like the Lakí, Veidivötn and Éldgja eruptions.

As our planet becomes warmer due to greenhouse gases and human energy release (rarely talked about component of global warming) into the atmosphere the glaciers around the planet have started to melt.

Iceland is home to Europe’s largest glacier, the Vatnajökull. Vatnajökull is situated on top of most of the Icelandic hotspot/mantleplume with Kistufell situated at the northwest corner of the glacier. As the ice melts the lost weight is tremendous, and this causes the entire crust to rise rapidly upwards. This in turn causes a diminished pressure at the mantle-crust boundary (MOHO) and depressurizing melt is more likely to occur.

Bárdarbunga

Bárdarbunga is the largest active volcano in Iceland, it was fairly unknown by volcanologists until satellite imagery revealed the true size of the volcano and the size of its caldera. It is responsible for the largest effusive eruption in the last 10 000 years, the Thjorsahraun lava field consisting of 25 to 30 cubic kilometers of lava from its extensive fissure swarm.

The last cataclysmic eruption happened in 1477 when the Veidivötn fissure erupted between 8 and 10 cubic kilometers of lava. That eruption ended with a VEI-6 caldera forming event.

The last confirmed eruption in the Global Volcanism Program catalogue was in 1910. That is though not correct. The last confirmed eruption from the main caldera happened at 1300 hours local time on the 6th of November 1996, the eruption was witnessed by volcanologists that was monitoring the ongoing Gjálp eruption and the eruption caused a 4km high column from Bárdarbunga. The eruption is believed to have lasted for only 30 minutes.

Gjálp

In the volcanic catalogues the eruption of Gjálp is assigned to Grimsvötn volcano, but there are reasons to doubt that assignment and nobody has ever given a really good explanation for assigning the eruption to Grimsvötn.

Most evidence instead point towards it being Bárdarbunga causing the eruption, or that it was an independent fissure eruption caused mechanically by Bárdarbunga. I am just mentioning this and I let everyone be their own judges on this.

Full moment-tensor point-source inversion results for the Bardarbunga event. Three-component displacement seismograms (radial, vertical and transverse, from left to right) are shown by solid lines and compared to one-dimensional synthetic seismograms (dashed lines). The lower-hemisphere projection of the P-wave radiation pattern is shown at right. The strike, rake and dip of the two nodal planes of the best DC solution, as well as the scalar seismic moment, moment magnitude, and percentage DC, CLVD and isotropic, are given numerically at right. Image and text from: http://rses.anu.edu.au/~hrvoje/Bardarbunga.html

Full moment-tensor point-source inversion results for the Bardarbunga event. Three-component displacement seismograms (radial, vertical and transverse, from left to right) are shown by solid lines and compared to one-dimensional synthetic seismograms (dashed lines). The lower-hemisphere projection of the P-wave radiation pattern is shown at right. The strike, rake and dip of the two nodal planes of the best DC solution, as well as the scalar seismic moment, moment magnitude, and percentage DC, CLVD and isotropic, are given numerically at right. Image and text from: http://rses.anu.edu.au/~hrvoje/Bardarbunga.html

At 10.48 on the 29th of September an M5.6 earthquake struck inside the volcano of Bárdarbunga. This earthquake was the last of a decade long series of a very peculiar type of M5+ earthquakes that caused no volumetric change. It is interpreted in such a way that fluid is changing places between two different and very large portions of the magma reservoir. A while ago a paper was published that argued that a large blob of fresh hot magma was pushed upwards and that displaced old magma downwards causing a no net volume change.

Map of where Gjálp, Bárdarbunga and Grimsvötn is situated, from the paper sourced below.

Map of where Gjálp, Bárdarbunga and Grimsvötn is situated, from the paper sourced below.

After the M5.6 earthquake a very intense earthquake swarm started at Bárdarbunga that quickly migrated towards Grimsvötn and Grimsvötn was in the end also covered by the earthquake swarm. Shortly before midnight on the 30th of September the amount of earthquakes abated a bit and harmonic tremor was detected. This was interpreted as onset of an eruption somewhere in the region.

The next day a reconnaissance flight discovered a depression bowl in the ice sheet and subsequent flights found more bowls in a line. The bowls was roughly equidistant between Bárdarbunga and Iceland’s second largest volcano, Grimsvötn. The length of the fissure that had opened up was between 5 and 6 kilometers in length. At the same time they noticed that the ice sheet above the Grimsvötn caldera had started to rise as water flowed into the caldera lake. A signal that a Jökulhlaup would soon follow the eruption.

The next day flights showed that the eruption had broken through the glacier and ash was explosively erupted.

On the 5th of November a violent Jökulhlaup burst forth from Grimsvötn with a peak discharge of 45 000 cubic meters of water per second, this was far more than the scientists had expected. As such it is the most powerful Jökulhlaup scientifically observed and in the end the Grimsvötn sub glacial lake was completely emptied out. It is estimated that the temperature in the Grimsvötn was 10 degrees Celsius prior to the start of the Jökulhlaup and that the unusually high temperature caused a wider than normal channel to form.

After 13 days of erupting the Gjálp fissure closed. The eruption had formed an elongated low ridge shaped like an overturned boat hull. The estimated amount of lava deposited was between 0.8 and 1.5 cubic kilometers. This is the second known eruption of Gjálp with the prior known eruption happening at 1938. As such it is possible that Gjálp is a unique volcano in its formative stage to become a new Icelandic central volcano.

The main reason behind assigning the eruption to Grimsvötn is that the eruption opened up on the southern end closest to Grimsvötn. This is though a bit of odd reasoning since historical evidence points towards Icelandic fissure eruption most commonly start at the point most far away from the responsible central volcano and then progress inwards to the central volcano.

The latest earthquake swarm

The semi destroyed Thuya of Kistufell. Photograph by Ágúst Jónsson.

The semi destroyed Thuya of Kistufell. Photograph by Ágúst Jónsson.

The latest earthquake swarm in Iceland is situated between Bárdarbunga and the Kistufell volcano. Kistufell has had no known Holocene eruption but a slow and persistent series of earthquakes started at that volcano 6 months ago. The start of the series was at 25km (MOHO) and has progressed upwards over time forming an earthquake stack to a depth of about 4km. It is likely that this is a dyke formation, but nothing is currently pointing towards an upcoming eruption since there is just not enough activity for that to happen in a volcano after such a long repose time.

140517_1810

The Bárdarbunga/Kistufell earthquake swarm (with the green star). Notice the still ongoing swarm at Herdubreid above. Image from Icelandic Met Office.

The Bárdarbunga/Kistufell earthquake swarm (with the green star). Notice the still ongoing swarm at Herdubreid above. Image from Icelandic Met Office.

In 2010 Bárdarbunga suffered its last major earthquake swarm. Even though the ongoing earthquake swarm had a M3.7 earthquake as it started the overall picture is that there is not sufficient seismic activity to point to an onset of eruption, nor is there any clear magmatic signals detected. So it seems to be yet another tectonic swarm caused by the building tectonic strain.

Conclusion

I firmly believe that the swarm of swarms that Iceland has suffered from is a sign that the tectonic strain is closing in on a condition where a rift eruption can occur, but the problem as usual is time-frame. It is quite impossible to say if it will happen within months or within a couple of decades. It is also impossible to say if there will be a normal Icelandic fissure eruption like at Krafla or Gjálp, or if it will be a larger rifting fissure eruption. There is of course nothing saying that there will not be either types, or nothing at all happening.

I do though think that something will happen, after all Iceland is nearing both a high-point in activity and the maximum risk zone for a large fissure eruption caused by tectonic strain release at the same time as massive deglaciation occurs.

It is where, when and which volcanic system that is so far written in the stars since the swarms seem to be jumping all over the place. But one thing is clear, it will start as an earthquake swarm, but that swarm will be intensifying over time instead of diminishing. So, if you see a swarm lasting for days with M3 earthquakes and it progresses towards M4+ earthquakes, then you can expect to live in interesting times. So far we are not there.

CARL

Sources:

Magnús T. Gudmundsson, Freysteinn Sigmundsson, Helgi Björnsson and Thórdis Hödnadóttir; The 1996 eruption at Gjálp, Vatnajökull ice cap, Iceland: efficiency of heat transfer, ice deformation and subglacial water pressure

http://rses.anu.edu.au/~hrvoje/Bardarbunga.html

http://earthice.hi.is/gjalp_eruption_vatnajokull_309_1310_1996

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76 thoughts on “Bárdarbunga, Gjálp and Onwards

  1. Interesting article, thank you 😀 Is there any tomography for what is under the Vatnajökull ice cap?

    Wonder where the next green star will show up.

  2. Thanks Carl! Enjoyable article. I was just settling down over Hekla and now I have other goodies to think about as well. That’s how I like it.
    Oh, PS everyone – I always post here as Clive but I may appear as clivetriggs as well. Sorry to confuse you. I don’t really understand computers.

  3. Seriously though, I didn’t know that the Gjalp Eruption was more related to Bardy. That is my new nickname for the volcano. Interesting as the Gjalp event happened at Grimsvotn but its source was not Grimsvotn?
    Many questions flying through.

    What are the chances of a Gjalp event happening there again? A possible new central volcano in that area.

    • Actually Gjálp is pretty much in between the two. And with the main seismic activity being around Bárdarbunga and Bárdarbunga coerupting I have my opinion about it pretty clear. I would though say that it is hard to state what happened with a 100 percent certainty. But in my world it is 80/20 in favour of Bárdarbunga on this one.

    • KarenZ, you will never be completely blocked out, but for some reason now and then WordPress and Akizmet seems to decide that you are a naughty girl… Hope you enjoyed the cookies.
      If it continues we will do the same thing as last. I upgrade you to Dragon for a few days. That sorted it out last time and I am certain it will do the trick this time.

  4. Causing a “peak discharge of 45 000 cubic meters of water per second,” it’s understandable how Gjálp seemed to be an appropriate name.



    According to Skáldskaparmál they were daughters of the giant Geirröðr. As Thor was wading across Vimur the river “waxed so greatly that it broke high upon his shoulders”. He finds out why.

    “Then Thor saw Gjálp, daughter of Geirröðr, standing in certain ravines, one leg in each , spanning the river, and she was causing the spate. Then Thor snatched up a great stone out of the river and cast it at her, saying these words: ‘At its source should a river be stemmed.’ Nor did he miss that at which he threw.” – Brodeur’s translation

    http://en.wikipedia.org/wiki/Gj%C3%A1lp

    For reference, the Mississippi River at max flow (Flood Stage) is around 86 791 m³/s.

  5. Fun stuff, Spica and Carl – food for beginners and experts! Keep doing the good job!
    BTW Anyone felt he 4.2 quake in Germany? Bruce?
    Lurking from behind, but always enjoying.
    🙂

  6. Cashing in….

    “A film about missing Flight MH370 is among the more unusual projects being pitched at this year’s Cannes Film Festival.

    The Vanishing Act, a drama by Indian director Rupesh Paul, features a cast of terrified passengers on board a doomed jetliner, and carries the tag line “the untold story of the vanished Malaysian flight”.

    http://www.mirror.co.uk/news/world-news/watch-flight-mh370-film-trailer-3559839#ixzz322hJOUPg


    And from the author that brought you;
    Sex Lives of the Popes, Sex Lives of the US Presidents, Sex Lives of the Great Dictators, Sex Lives of the Kings and Queens of England, Sex Lives of the Hollywood Goddesses, Sex Lives of the Hollywood Goddesses 2, Sex Lives of the Hollywood Idols, Sex Lives of the Great Artists, Sex Lives of the Great Composers, Sex Lives of the Famous Gays, Sex Lives of the Famous Lesbians and Sex Lives of the Roman Emperors, comes his latest work, a theoretical tretis on flight 370.

    “Flight MH370 – the Mystery, written by Anglo-American author Nigel Cawthorne, cites anonymous sources to suggest that misinformation was released so the search would concentrate on the wrong area, The Sun-Herald newspaper reported.”

    http://www.nationmultimedia.com/breakingnews/Book-suggests-missing-Malaysian-airliner-accidenta-30233919.html

    • Wouldn’t surprise me. I read somewhere else that groundwater is also a very important factor in the Low Rhine Graben (Limburg).
      Groundwater seems to influence eathquakes. Also in the Limburgian hills, the higher grounds have higher groundwater tables than the valleys due to rising water through the faults. etc.

      Some examples:
      “The most recent one was the 1992 Roermond earthquake which reached ML=5.9. Recent studies reported that active faults in the study area are characterized by recurrence periods in the order of tens of ka (Skupin et al., 2008; Camelbeeck et al.,2007), and that present day aseismic slip is assumed for the Rurrand Fault, resulting form the lowering of the groundwater level due to the nearby mining activities (Vanneste & Verbeeck, 2001). ”
      http://www.nug.rwth-aachen.de/media/Corinth/81_Winandy_Gruetzner_et_al__Corinth_2011.pdf

      “However, we do not observe any significant indication to atribute a tectonic origin to this signal for two main reasons. First, during large part of the studied period the most of the graben uplifts with respect to adjacent horsts at rates of ~1 mm/yr, behaving opposite to predicted by tectonics. Second, the deformation signal in this area appears to be largely related to water pumping. For example, we observe an uplift signal of about +4 mm/yr that matches in time and space with the cease of pumping in the Erkelenz Coal District, which is located in the Peel horst, adjacent to the Roer Valley Graben.
      Concerning the mines of South Limburg, we detect strong surface displacements (uplift) which appear to be centered on the old mines and constrained by tectonic faults. The signal is variable in space and time, with uplift rates up to 20 cm in 18 years, and relatively large gradients across faults (~5 cm/km), in the same time span. Laterally the uplift signal propagates towards the west in this period. The comparison of surface displacements with rising groundwater levels reveal a strong correlation between the two, suggesting the groundwater to be the cause of the uplift.
      Assuming that rising ground water levels in the abandoned mines are responsible for the uplift, we estimate the relation between the groundwater and the associated uplift. The skeletal storage coefficient, which directly depends on porosity, is on average 0.5±0.1·10−3, implying that 1 m of water level increase produces 0.5 mm uplift. As we expect that the water may rise many tens of meters, especially in the western side, this may result in several additional centimeters of future uplift.

      Essentially, the surface displacements that we observe in the southern Netherlands seem to be mainly caused by fluctuations in groundwater flow, which appear to be constrained by faults.”

      http://repository.tudelft.nl/view/ir/uuid%3A83aba703-de6f-46cd-9a0a-85af28bf4324/

      There is a discussion that the uplift, caused by groundwater, can rise the stress in the faults or not.

    • It’s all about the pore pressure. Generally, an increase in pore pressure tends to more energy release since it can act as a lubricant.

      But, on the whole, I am pretty sure that you will find that this is just another arrow in the quiver of those trying to cut down on food production. It’s almost like they have a de-facto industry set up around stopping food production.

      But… that just fits with the overall goals.

    • Thank you DFM!
      It is rarely I have to read up on things in Iceland more than checking facts, but this was such an occation. Bárdarbunga is still in part an enigma in need of more study.

  7. Great post, Carl!
    I got a question: “…historical evidence points towards Icelandic fissure eruption most commonly start at the point most far away from the responsible central volcano and then progress inwards to the central volcano.”
    Why is that so?

  8. You really had to come up with that question did you Cryphia? 🙂
    To be quite honest, I do not have even a half decent answer to your question.
    The historical evidence for it is overwhelming, Laki, Veidivötn, Éldgja, Krafla… the list just goes on. So there should really be an obvious physical explanation for it that I just can’t figure out.
    My very loose guess is that the central volcano will never be strained enough to rift due to regular eruptions sorting out any built up strain. And to continue on my guess is that the stress field around the volcano is continously lowered due to this, and as you progress further away from the volcano the stress field starts to rise making it more likely for a break to occur. Also I guess that the temperature in the crust would be higher closer to the main volcano.
    So in the end I guess it is higher crustal stress and more brittle crust the further out you go. And as the initial break happens it will start to unzip like the zipper in a pair of pants which are tight. I guess everyone has noticed that a tight pair of pants require a bit of force to open the first centimeter of the zipper, but after that it opens almost on its own downwards towards your personal volcano.
    But, this is just guesses. You found a Ph.D. dissertation question I think.
    Perhaps Lurking has a better answer, he is better than I am at faultlines and fissures.

    • Dunno about the “better at” aspect of it. Maybe on certain faultlines, but not all.

      KarenZ seems to be closer to the mark on the general reason. Since the central volcano is the most active feature, (which is why it’s the central volcano), there would be logically, more failed feeders and dyke structures there. They act as sutures to hold the wound closed. Also, the residual heat would keep the rock more plastic.

      That’s my take on it. (Not a geologist, not a Physicist, not a Brewmeister, but I’m pretty good with a multimeter.)

  9. Now I am going to play the game of where will the next swarm occur…
    As an earthquake swarm happens it releases the tension localy, but at the same time the strain can increase in the surrounding areas.
    Tjörnes is almost constantly releasing tension, but can still suffer from larger episodes and quakes, same goes for Reykjanes Ridge. They are almost constantly active with starmarked earthquake swarms. Lately we have also seen swarms in SIFZ, Herdubreid (several) and Bárdarbunga.
    But where will the released strain cause increased strain? And where have there not been any strain release? And where can we see intermittent earthquakes that might be a sign of an upcoming large swarm?
    Let us go from north to south.
    1. Theistareykjarbunga volcano is showing intermittant earthquakes and has been inflating since 2008. The pent up strain here is equal to 55 to 115 meters of unreleased strain. It is a likely place for a swarm.
    2. Fremrinamur volcano is showing very little or no signs of activity, the pent up stress here is between 45 and 75 meters. Question is how many years it will take before it start to “snap, crackle and pop”.
    3. The region spanning from Thordharhyrna down to Hábunga (the one under Vatnajökull) volcanoes. The area is having intermittent earthquake activity from depth between 20km up to 2km. Quite a likely area for a decent earthquake swarm.
    4. The Dead Zone, has started to have intermittent earthquakes as a sign of building strain. Should start to suffer swarms in the near geological future.
    5. Katla and Gódabunga. Was a while ago so probably going to go for a swarm soon.

    • Perhaps the central volcano temporarily acts as glue to hold the fissure together?

      Btw I am playing a game: how many attempts before WordPress lets me post? Right now it is 5.

    • Theistareykjarbunga, The Dead Zone, Thordharhyrna down to Hábunga, Katla, these are not small volcanic zones.

      They will have a massive local affect on Iceland if they decide to go for a fissure eruption. A an Island, snow and ice are becoming less of an feature. If we look back 200-400 years, glaciers were much bigger and thicker.

      Will this affect the strength, amount of magma and how quickly a fissure starts up, my thinking is yes.
      They did not have dams at that time, with all that lovely energy to create ash.

      The pulses that we have seen in the last year, are becoming stronger and more of them. maybe Months or years away.

    • 2nd attempt.

      Mýrdalsjökull seems to have been a bit quiet recently. Don’t know if she will go for a green star or not when she plays catch up.

    • Looking at the swarms from a debugging perspective, there’s been quite a fair share of parallel processing going on over the last month or so.

      Why didn’t the Reykjanes ridge make it into the list? The swarms have come back there several times, & its my top of the list wild guess of systems for break on this.

      Serge

      • I’m thinking that we are seeing waves of extension up and down the MAR. Sporadic Mag 5.0s have been happening up and down the length of the MAR, and it’s just a matter of time until Iceland has to accommodate it’s share of the extension. The difference is that with Iceland, we get a great deal more detail in that action due to IMO’s instrumentation efforts.

  10. To the other Dragons…
    I just released for of KarenZs comments out of the Dungeon. Keep an extra eye out for her comments.

  11. GL Edit: Brought forward so that we can address a question.


    Shane May 15, 2014 at 01:12

    Hi Spica. Thank you for putting all this together. Got loads of questions, but have no intention of boring you with all of them except,
    *What a volcano needs as a kind of “driving force” is a magma chamber deep below the ground.”
    Is a magma chamber more likely to occur in areas of weaker crust or weaker rock? (Maybe both of these are the same?) Or is it related to techtonics? And have all of them already formed, or could one develop under my feet today?
    I suppose what I am asking is, what makes a magma chamber?

    GeoLurking
    May 18, 2014 at 07:46
    Thanks to Ukviggen who’s response drug me here out of curiosity.

    Magma, more importantly, “melt” is formed from a number of processes. Typically “decompression melt” comes as the overlying stress from the sheer mass of overlying material is removed…. such as the melting of an ice sheet or cap. This lessening of the overleying mass can swing a region of really hot rock below the melt point. Its not exact, but its similar to the boiling point of water dropping if you put the water into a low pressure area, like on top of a mountain. Over timme this melt volume will increase and pool, or percolate upwards due to bouancy. Once it reaches an area where bouancy can’t push it any further, it can accumulate to form a magma “chamber.” As it slowly cools, crystals can form from the compounds in the melt. This can lessen the availible space in the chamber and overpressurize it. Once the pressure goes above what the rock can handle, a finger of magma can then start forcing its way up through the rock, making an eruption if it gets to the surface. Other ways are possible, this is just one example. Im on a phone and can’t write much more than this right now. Hope it helps.


    GeoLurking
    May 18, 2014 at 08:02

    And just a wee bit more

    Subducting slabs are a major source of melt. Water entrained in the cracks of the seafloor, and that incorporated into the molecular structure of the rock, (such as in serpentinization) can act as a flux and lower its melting point. Typically at around 125 km depth of the slab, melt percolates off and causes the formation of volcanoes in a line approximately over that depth contour of the subducted slab. These are arc volcanoes, like those on the Kamchatka peninsula, or the cascade volcanoes in the pacific northwest…. or the lesser Antilles.


    To All, feel free to chime in with your info and insight.

    • Additionally, one idea that stumbled out here in the discussion several months ago, is that a magma “chamber” is not necessarily a chamber or continuous pocket of magma. It could very well be a collection of tendril like cracks and crevasses holding a quantity of melt within it’s confines. A diffuse fuzzy “grid” of partially liquid melt.

      Now, in both models of this, the rock is what holds the melt in place. As the pressure rises, that region that is the weakest will fail first. How strong the walls of that “chamber” are is a function of the strength of the rock, and the amount of lithospheric stress from the overlying rock (which acts to hold the rock in place and preventing fracture). The less overlying mass, the weaker the overall “hoop strength” of the walls. That is why dikes tend to propagate from the top of the “chamber” and work their way towards the surface. I’ve seen some articles that indicate that in a sill like emplacement, as the finger of magma moves out through the seam of a discontinuity of the rock, it tends to curve upwards towards the surface. The “weaker rock at the roof” idea is what is probably behind that.

      The initial eruption of Tolbachik showed this quite well as the quake sequence for the start-up ran out from the nearby volcanoes and turned towards the surface.

      Speaking of quake stacks. As a finger of magma works it’s way to the surface, the breaking of rock will usually show up as a series of small quakes. Plotted out, they tend to show up as a literal stack in 3D. It can take several years of this sort of activity before anything eruptable accumulates. In addition, these quakes will tend to have a “wet” appearance (Carl’s term) that signifies a long period component in the frequency structure of the quakes. Carl can tell you more about that.

      Using a “MOGI” model of surface deformation (from GPS) can give you an idea of how much material has flowed into a “chamber.” But as a rule of thumb, only a few percent of that volume will actually erupt, if it ever does.

      The length of time that melt remains in a chamber will alter the chemical composition of the magma. Over time, the composition will shift towards a more silica rich magma as the material fractions out and crystalizes. The more silica rich, the more rhyolitic it becomes. (andesite is just one step on that path).


      Not all movements of magma result in eruptions. Godabunga is a good example of that. It formed a cryptodome on the flank of Katla, but no one really knows if it will ever erupt or not. One idea that was put forward was that the Fimmvörðuháls eruption could have been magma from that emplacement, but given that Godabunga has not been reported as deflating, that makes it unlikely. When Fimmvörðuháls was well into it’s run, a set of quakes shot across to underneath Eyjafjallajökull and it went off quite handily. It had been accumulating a variety of quakes underneath it for several years. My guess is that the quick injection from Fimmvörðuháls was what was needed to get it going. Another idea that bit the dust (in my opinion) was the alledged connection of the plumbing for Eyjafjallajökull and Katla. Non of the plotted quakes illuminated a connection as far as I can tell. Katlas quakes extend down and somewhat to the east. Eyjafjallajökull’s run straight down to the Moho.

      Mt St Helen’s also had a cryptodome, but a landslide catastrophically depressurized it and the gases in solution in the magma instantly came out of solution, yielding a lateral flank blast that took everyone by surprise. R.I.P. volcanologist David A. Johnston who was stationed at an observation post 6 miles away. (9.5 km)

      And if you want some entertainment, compare the narrative with the closed captioning text. It can be hilarious.

      And suddenly this immense black corruption cloud came pouring up out of the white player that the cloud tops

      • Johnston’s colleague, Gerry Martin, was also killed in the eruption. Martin was in the unenviable position of witnessing Johnston’s death before his own.

      • Well done, Lurk! Maybe this comment deserves the status of a post on its own, don’t you think, dragons? – a part 3 of Spica’s and Carl’s?

          • Actually, I was just putzing round and ran across Ukviggen explaining what the cookies and dungeon were all about to a perplexed commenter. The original comment appeared to have a really salient question and I tried to elaborate on it.

            I brought it forward as a way to fill in the learning aspect of the series. It could become a post unto itself, but I don’t have time to work on it right now. As for sourcing, well, it’s just stuff I’ve picked up along the way and don’t really have anything to cite.

        • I am so going to edit this together into a post… Unless Lurkmaster Himself wishes to do that? Perhaps better is Lurking does it…

      • St.Helens over-steepened.the northern slope until it failed. It had undergone some hydro-thermal alteration and that certainly helped St.Helens collapse.

        The area used to be quite scenic.

  12. Not sure that the magma that ascended under the neighbouring volcano did divert to the south and erupt at Tolbachik. Tolbachik’s lavas are more basaltic than her neighbours’; and, the neighbour was Klyuchevskaya Sopka who also erupted in 2012 and 2013.

    • I’m just following the quake pattern. Had it been destined for one of the main cones, it might have taken up residence and simmered for a while, changing it’s make-up.


      Sidenote. My wife is watching womens collegiate softball. One of the players from yesterday, Jacee Blades, an outfielder… is mind numbingly fast on her feet. Saw her field a ball yesterday that in my opinion, she should not have made it too. If you put that girl on a base, you had better watch her. Bungle a toss to another player and she probably could steal her way to home.

      Needless to say, I find her sprinting ability to be quite impressive.

      Now the odd part. Her field of study is pre-med. I wonder how she can put her physical talent to work in her chosen field. Maybe she will be able to out run the crash cart to cardiac events in the hospital. Or, put extra long leads on the shock paddles and just turn her loose.

      Get this… from what I can tell, she has made the SEC honor roll every year she has been in college. Not only is she a speed demon, she is quite bright.

      • Oops… according to my wife, she did just that today in a game. The opposing team bungled toss and from second, she made it all the way to home, scoring a run.

  13. Now Iceland is almost eerily quiet from an earthquake perspective. At least compared to the last few weeks.

  14. Poking at Carl again…


    New intriguing finds from the Late Iron Age have been found in Kvarnbo, Saltvik, on the Åland Islands, within the framework of a project led by Dr Kristin Ilves. Finds, consisting mainly of personal ornaments of silver and bronze, were unearthed in connection to what is believed to be the remains of a 40 metre x 12 metre building.

    http://www.pasthorizonspr.com/index.php/archives/05/2014/the-hall-at-the-crossroads-of-baltic-waterways

    Elsewhere, in Scotland…

    Some bones were found.

    Human predation led to the decline of the species, ensuring that by the middle of the 19th Century it had become persecuted and exploited into extinction.

    Yeah, by museums putting a bounty on any remaining birds so that they would have a stuffed animal for their exhibits before they went extinct…

    • Akureyri museum must have missed out – their specimen is a bitsa. Bits of guillemot, bits of penguin…..

    • Åland is an interesting place, it is almost a consecutive stretch of Islands between Sweden and Finland. So during the ages it has been the hub of commerce between the two countries. Apparantly for thousands of years.

  15. For those interested in hard core plate tectonics, I recommend Chris Rowan’s blog : http://all-geo.org/highlyallochthonous/
    He suggests that spreading oceanic plates through rifting can be determined by some not so intricate models, which in turn could have deep global effects on plate distribution (as far as I could understand. Definitely, food for thought!
    Have fun! 🙂

    • I made an update on Heirdubreid, but the data goes only up to the 16th.

      Otherwise, same settings as before, the quakes are shown from may 1st.

    • More will definitely be coming sooner or later. The last few weeks released tension in a large amount of hotzones for earthquakes in Iceland, that is why I suspect that next swarm will be at some unusual place (Or in Tjörnes or Reykjanes Ridge of course).

  16. Does someone has recent news of Nishino Shima (or Jima, choose your poison… 😀 )? I went to see the Modis hotspot site and there is one, but no pics or video since April 15th….

  17. I just cut open my forehead open last night. I walked right into the corner of the door on our circuit breaker box on the side of our house, resulting in a small gash and quite a bit of bleeding.

  18. A really quiet period indeed atm. And whats holding Katla back from a swarm? I cant even remember ever seeing a star there and a large part of the quakes in the area is at the darn God. cryptodome anyway. 😀

    • I think the last star there was in 2012…
      More or less there has been no intrusive activity at Katla or Gódabunga since Eyjafjallajökull, just a couple of smaller events.
      But sooner or later something larger will come. And when it does it will be noisy.

      • With no [further] basalt intrusions for a while, can the magma in the chamber cool more and extend the “sleep” period? Or is there enough “residual” heat left from somewhere to prevent cooling (relatively cooling). Or the heat cannot be transfered so fast to the rock around the chamber? I am not really familiar with underground “thermodynamics”, so I have to ask. 🙂 And what is the usual heat loss factor of a magma chamber of the similar size and composition like Katlas? If it is possible to say/estimate.

  19. The picture you have is of Kistufell in Esja, next in Reykjavík. Not of Kistufell in Vatnajökull.

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