Tungnafellsjökull – Tectonic Earthquakes

Photograph by our own Jamie. Tungnafellsjökull seen from Sprengisandur area. Notice that the Jökull is almost gone from Tungnafellsjökull, soon to become known as Tungnafjöll only.

There has been an earthquake swarm at the northern end of the Tungnafellsjökull during the evening and throughout the night. The swarm is still ongoing. There has been a lot of speculation out there in the blogosphere about it being volcanic in nature. It is not, it is purely tectonic.

As some of you know Iceland is divided by the Mid Atlantic Rift (MAR). The MAR in turn is divided in Iceland into two separate active seismic zones, the Eastern and the Western Icelandic Seismic Zone. Lately it has been the EISZ that has been most active of the two. But the WISZ is not in any way dead or dormant. Both of them are driven by the spreading of the MAR. From the WISZ the North American Plate is spread, and from the EISZ the Eurasian Plate is spread. In between them are two micro-plates that have formed by volcanism caused by the rifting.

The map is showing the Icelandic Volcanic Zones, where the MAR runs up into Iceland, where the MAR leaves Iceland and the more important volcanic features. The Icelandic Seismic Zones are corresponding to the volcanic zone.

Along both the WISZ and EISZ are lines of volcanoes spread, it is where the spreading causes magma to pour up and fill the spaces created by the spreading.

If you look at the map you see that WISZ runs from Hengill, up to Langjökull (2 known volcanoes), via Hofsjökull (at least one volcano), onwards through Tungnafellsjökull, and then ending up at the triple-junction at Bárdarbunga.

During the last few years the area of Tungnafellsjökull has been inactive, but there is ample evidence of it having been tectonically active, something that can be found in the Sprungur (tectonic faults) found in the area. The dormancy is likely due to the area having been locked at depth, probably by old magma that has solidified the area.

Various versions of tectonic faulting. Tungnafellsjökull is suffering from strike-slip faulting.

Lately the area has been subject to an uplift not seen in Iceland since de-glaciation after the last Ice age. This is due to the melting and diminishing of the glaciers of Tungnafellsjökull (almost gone) and Vatnajökull. This uplift process has accelerated during the last decade. It is now up to 3 cm year in the area according to Sigrún Hreinsdottir (source, private email). Yes, the famed inflation of Hamarinn is not happening, it is a combination of Grimsvötn motion and isostatic rebound.

This motion might have started to release the seismic lock at Tungnafellsjökull. If that is so, there is a risk that the swarm of earthquakes is just precursor quakes for a large earthquake.

This map shows the features discussed in this text in relation to the Bárdarbunga triple-junction and the hotspots location.

What makes this interpretation the more likely one is that there is no discernible evidence of any harmonic tremoring during the earthquakes. This makes it into tectonic seismicity, not magmatic seismicity.

If there would be a large earthquake that tears the rift-lock, then magmatic movements could start in the area, but not before that. Worst case scenario here is not a volcanic eruption; it is a 6M earthquake as the slip-lock disintegrates over a large area.

Another thing that I want to point out, the earthquakes are all of low probability and some of them are as I write this due to change after revision, and some of them will be removed due to being false representations of earthquakes, so called Ghosts. And as I wrote this IMO has started to revision the earthquakes, right now there is at least one at 3M.


228 thoughts on “Tungnafellsjökull – Tectonic Earthquakes

    • Those are associated microquakes that come along with the larger ones. On higher resolution they show up as miniscule quakes, probably as the larger ones causes the adjoining rocks to resetle.

  1. And now it is a 2.8M.
    Also note that as they go through and do the revisions they are also putting them at greater depth around the area where the probable slip-lock is. I believe that all of them will end up in the 12 – 7,3km depth with no pattern of motion upwards.

  2. Next post will be Alan tackling a Hypervolcano™. Of course if nothing blows up before then.

    • A good quake to discuss a bit.
      First of all it is of low probabillity and is thusly due for quite a bit of revision. It is also belonging to the Nyidalur swarm. So it is likely to be moved towards the rest of them. Also, the depth will increase substantially later.

  3. Magnitude Mw 6.0 Region NEW BRITAIN REGION, P.N.G.
    Date time 2012-04-07 11:58:08.0 UTC location 6.83 S ; 149.58 E Depth 45 km


    2322 km NW Brisbane (pop 1,843,392 ; local time 21:58:08.4 2012-04-07)
    155 km SW Kimbe (pop 18,847 ; local time 21:58:08.4 2012-04-07)
    69 km S Kandrian (pop 1,014 ; local time 21:58:08.4 2012-04-07)
    396 km NE Port moresby (pop 283,733 ; local time 21:58:08.4 2012-04-07)

    Source parameters not yet reviewed by a seismologist

  4. The goverment of Columbia are preparing for the possible erruption of the volcano Nevado del Ruiz..



    ,,Near 17.236 volunteers, technicians and professionals from Red Cross, Civil Defense and fire in Caldas, Tolima, Antioquia, Cundinamarca, Risaralda, Quindío and Valle del Cauca are ready to react to a possible eruption of volcano nevado del Ruiz, which is still warning Orange by its constant seismic movements. Thus reported it on the morning of this Holy Thursday the national unit for the management of the risk of disaster (UNGRD) which already installed 1.378 temporary accommodation in Caldas, Antioquia, Risaralda and Valle del Cauca to accommodate persons who are to be evacuated.

    Similarly, are lists 32 purification plants of water and sanitary batteries and 1,800 packages with emergency humanitarian aid to assist possible victims. Likewise are willing 83 vehicles and 129 teams to perform actions of air rescue,,

      • Shouldn’t had translated it…, it didn’t said almost anything new, and it was badly redacted, :/, but well, I did it anyway:

        Authorities report inestability in the volcanic activity of Nevado del Ruiz

        El Observatorio Vulcanológico y Sismológico de Manizales indicate that, according to the monitoring being done, the volcanic system continues showing inestability on the behavior of its seismic activity and the rate of emission of volcanic gasses.

        The Observatory reports that the seismicity associated with the movement of fluids and fragmentation of rock within the volcanic building (edifice?) has shown fluctuations in terms of number and magnitude, maintaining levels like the ones that motivated the change on the level of volcanic activity (risk level?).

        At the moment, it’s emphasized the ocurrence of an event of volcano-tectonic fracture, and it’s reported that sulphur emissions keep being high. (less than what was said on the previous paragraph…)

        Manizales stays calm, but on alert due to possible eruption of the volcano Nevado del Ruiz

        A report of complete normality gave the Mayor of the City of Manizales, Jorge Eduardo Rojas, regarding the orange alert that exist due to the possibility of a new eruption of the volcano Nevado del Ruiz.

        Added that, in these moments, the situation is under control in spite of the fear that exist within the population on the influence zone of the volcano.

        The head of state (…who wrote this?) explained that there is an alarm and monitoring system that watches 24 hours a day at Ruiz, with the finality of being attentive in case of any eventuality.

        According to Rojas, the aiding organisms are patrolling 24 hours a day the volcano’s influence zone in order to avoid last hour surprises.

        The mayor of the city of Manizales stated that, in spite of the complexity of the yellow alert, the situation is under control.

        On his side, Ingeominas manifested that, according to the seismological observatory of Manizales, it’s reported a strong sulfer smell in many sited of the Capital of the Department of Caldas.

        However, they clarify that the situation is normal, considering the actual state of activity on the volcano Nevado del Ruiz, which has been giving high unloads of gasses in the last days (high degassification, I guess).

        Contingency plans ready on the municipalities bordering Ruiz in front of an eventual eruption, reports the Government

        The National Director for Risk Management, Carlos Ivan Marquez, confirmed that the mayors of the municipalities bordering the volcano nevado del Ruiz activated the contingency plans in front of an eventual eruption.

        (He) said that there is coming an advancement on a plan of accompaniment on the Government’s part, with the end of establishing an integral work between the municipal authorities, departamental authorities and at a national level.

        According to Marquez, there have been meetings with the aiding organisms of Caldas and Tolima to establish the zones that could be affected in front of an eruption.

        Also, asked that they carry out constantly activities of community information, based on the reports from the Geological Service, and the indications of sensibilization and prevention defined by the authorities.

        Added that the National Government has established a plan of accompaniement of the mayors of the zone that may be affected (and here they invented a word…) by Ruiz to establish the weakness and adopt the respective corrections.

        According to the official, it was activated the First Ring of Reply and Intervention on the Departments of Caldas and Tolima, due to them being on the influence area of the Volcano Nevado del Ruiz.

        Regarding the roads, acknowledged that between the populations of Murillo and Manizales the situation is fairly complex. Manifested that in the other secondary and tertiary roads that were affected by the winter, there has been given resourced to the mayors so they can advance the respective cleanings.

        Announced that it was ordered a tecnical revision and maintainance to the System of Alarms in all the influence zone of Nevado del Ruiz.

        Finally, announced the delivery of help of 1777 millions of pesos to the Regional Committee for the Prevention and Attention of Disasters (CREPAD in spanish), Crepad Tolima, and the aiding organisms of the department.

    • Judith, a common mistake for anglophones is to spell “Columbia”, but the country’s name derives from the Italian origin of the Genoese navigator, Cristoforo Colombo.
      Thus, the correct spelling (only for the country) is “Colombia”.
      Thanks for the heads up!

  5. KarenZ,

    If you zoom in on the map at EMSC – CSEM, you will see that these quakes are north of the island of Sicily and not on Etna. As Boris often points out, the quakes that do occur on Sicily just to the north of Etna are tectonic.

  6. Special Bulletin activity of the volcano Nevado del Ruiz, 06 April, 8:40:00.
    With regard to monitoring the activity of the volcano Nevado del Ruiz, the Volcanological and Seismological Observatory of Manizales, reports that:
    During the last 24 hours, the various parameters of monitoring show that the volcanic system continues to show instability in the behavior of seismic activity and the emission rates of volcanic gases. The seismicity associated with fluid movement and fracturing of rock in the volcanic edifice has shown fluctuations in number and magnitude, keeping the same levels that prompted the change to orange in the level of volcanic activity. To be highlighted is the occurrence of some seismic signals that may be associated with small ash emissions, restricted to the active crater. The measurement of sulfur dioxide (SO2) values ​​ to the atmosphere remain high.​​

  7. I think this is an awakening of the volcano at Tungnafellsjokull. The area is really remote and also not far from Hamarinn to the south, Bardarbunga to its southeast or Askja to the northeast. There has been increasing activity at the hotspot center, which increases activity in all volcanic areas around. So, I would not be surprised to see an eruption in one of these areas in the next years.

    Let us remember that eruptions in Iceland can start often without little or no earthquakes (example of last eruption of Grimsvotn, eruption at Westman Islands, eruptions of Hekla…). So, I take it serious this increase in activity to the north and northwest of Vatnajokull. We have seen for some ocasions last year, tremor at this area. Can even be the case that magma from Bardarbunga has now intruded into Tunganefellsjokull, just like it did to Grimsvotn and Hamarinn in last years.

    • You missed the little tidbit that the Hamarinn inflation is not happening.
      I wrote a mail to Sigrún about GPS things and got among them the answer to HAMA. It is pretty much glacio-isostatic rebound caused by the melting of the Vatnajökull glacier. It has increased over the last decade or so as the de-glaciation has increased in speed due to the warming of the northern hemisphere. This effect around Vatnajökul is up towards 30mm annually, the rest of the motion is quite simply residual from Grimsvötn.

      So, there is definitly not any uplift in the Tungnafellsjökull other than the glacio-isostatic rebound from the by now almost all gone jökull ontop of Tungnafjöll.

      • I totally agree with uplift linked to deglaciation.

        But also take attention that the dead zone area in Veidivotn could also be inflating too because it is also running towards a future eruption, maybe not in soon, but in next decades or centuries. Inflation is not only measured in Hamarinn (which sits at edge of Vatnajokull – I do not know if the GPS is at the nunatak there or outside of the glacier), but inflation is also measured at Skrokkalda, which is outside of the glacier, but in fact it was covered by glacier probably some centuries ago.

        The other interesting point is that deglaciation often triggers and increases the activity of volcanoes in Iceland. So, with climate warming, we might been into some surprises, as volcanoes at edge of Vatnajokull become suddenly deglaciated at the same time as peak in hotspot activity is reached. These volcanoes at edge of the glacier are Tungnafellsjokull, Hamarinn, Kverfjoll and Thórdarhyrna. Bardarbunga is not very far from the edge of Vatnajokull but still under thick ice.

        • Actually the Dead Zone do not inflate per se. Why? Because it is not volcanoes on its own. The Dead Zone is dependant on magma being poured into the fissures as they break open due to the plate rifting apart, that magma is poured from the responsible mother volcano. Currently only two of the 3 mother volcanoes are inflating, and those are Grimsvötn and Katla. And Katla seems a bit sleepy right now to be honest. Bárdarbunga seems to not have inflated a lot on the historic data when taking glacio-isostatic rebound into acount.
          The HAMA is just on the outskirt, but SKRO has the same motion almost. The current motion is actually fairly new. Yes, the glacier has been diminishing steadily since the little ice age, but about 15 years ago it started to melt in an ever increasing speed due to the warming of the northern hemisphere.

          Yes, I think that the pressure load decrease will give larger eruptions, but this is just me guessing here.
          What you should remember is that the ice ontop also decreases, so it is not only the rand-volcanoes getting affected. It could be that the increase in Grimsvötns eruptivity is caused by less plate load, but that is again me guessing.

          • what about the earth is heating up from the inside due to rotation speed, water in the deeper parts of the oceans are getting warmer, so naturally it will progress upwards etc.

          • The earth is not heating up, it has actually been cooling down continously since being massed. What is delaying the warming is both the kneading by the gravitational pull of the moon (not that much, but enough to make a difference), but mainly it is due to UrTh transitioning. But the net energy released is a bit smaller than what is lost. Earth is slowly losing internal energy and heat.

          • sorry I used the wrong way saying what I wanted to say, I think.
            heat is raising to the surface under the oceans which in turn heats up the atmosphere, like a lot of fissures, most in places where there is no knowledge, all that and not enough salty water running into the oceans will cause slow down/stop of the currents.
            There is a large area of very hot water according nooa of the nort american coast for a long time now, fissure ?

          • The north american coast is very long, and also it runs on both sides of the continent.
            My guess here is that it is along the eastern seaboard. If so, it is the longest running movement of hot water, the Gulf Stream.
            Actually most of the heat that we on a daily basis are subject to comes from the sun, not from the depth. The crust works as a surprisingly good insulator. A large part of our planet is actually permanently frozen due to this phenomenon.

          • sorry, it is on the north eastern part not far of the coast, temps are well above normal, but I don’t think it is the gulf stream, if you look at the pattern for the gulf stream it is broken up and not reaching as far north as that. The sea pattern of above normal temps coincides with the tectonic plates

          • @ Ursh: gulf stream it is broken up and not reaching as far north as that.
            The Gulf stream reaches far far north, it travels along the east coast of the US, crosses the Atlantic and goes up to Scandinavia and curls around the Nordkapp – way norther than you think! It’s the reason that Northern Europe has much less harsh winters than North America at the same latitude!

      • But its great Carl, that you have asked him about HAMA inflation and clarified that.

        We certainly do not wish for a Veidivotn fissure here 😀

        • I am still not giving up on that one. Bárdarbunga could have had many inflative periods before the CPGS network got up. And also, we know that it do not take a long time for hyperinflative mode to bring a volcano to bursting. Just look at what happened at Eyjafjallajökull.

      • Tungnafellsjökull is far too small to cause any kind of isostatic rebound, even locally, even if it melted instantaneously. Vatnajökull is a different beast. But if you check this figure here ( http://strokkur.raunvis.hi.is/~sigrun/GFUMa.png ) and remove the Grimsfjäll part, you’re left with an uplift that has slowed down during the last 25 years. I do not buy your reasoning, I think Irpsit has the correct clue in this…

        • Well, I do think that Sigrún has a clue on this.
          According to the linked info from Sturkells page in this thread (should be under Treasury) the actual uplift due to glacio-isostatic rebound is 29,7mm per year for Vatnajökull (Sturkell). Same data is also given by Sigrún in related papers.
          It is not my “idea”, it is the collective opinion of the research comminity backed by several GPS-campaigns.

          • You’re not reading me correctly. So, I’ll ask a very basic question: How do you make a difference between rebound due to deglaciation and large-scale magmatic hot spot inflation in the GPS data?

            Exactly! There’s no way to see the difference in the GPS data alone. Hence, you have to look for the other signs. And they point to the direction of higher volcanic activity in the future.

          • You can do that by checking for A) gravitetic shift, B) inSAR imagery, C) data from high-density GPS campaigns.
            And I did not read you wrong, you said that the rate of annual uplift had decreased for 25 years. Now you say that an increase in hotspot activity will cause the increase in uplift. You can not have it both ways.
            According to available GPS data the only active volcanic uplift is at Grimsvötn, but that was not a big surprise. If it was a general uplift one would assume that Bárdarbunga was being uplifted, and also assume that it would be inflating.

          • Well, not exactly. I said the uplift had slowed down during the last 25 years, not for 25 years. In any case, if it were true for the entire Vatnajökull, it can not be only due to deglaciation (which should have caused an increase in uplift). All those other methods are reliable only when interpreted with other data (e.g. eruption history, etc.). And, those GPS values are always local, unless proven otherwise with high-resolution campaings with several stations.

            My point is: You have to check the whole picture. To me it looks inconsistent with only deglacial rebound taken as the root cause..

          • Well, they have done high def campaigns.
            But, this argument you will have to take with Sigrún who is heading the research into it.
            Formulate a couple of specific questions and post them in a few days in the appropriate (by then) post about GPS:es and you will probably get an answer.

        • Also I would like to point out that the link is only covering the last 15 years, not 25. And I think that Sigrún knows what she is talking about when she says that the rate is increasing. But, you are welcome to your opinion.

  8. [Euler’s theorem] … states that the movement of a portion of a sphere across its surface is uniquely defined by a single angular rotation about a pole of rotation. The pole of rotation, and its antipodal point on the opposite diameter of the sphere, are the only two points which remain in a fixed position relative to the moving portion. Consequently, the movement of a continent across the surface of the Earth to its pre-drift position can be described by its pole and angle of rotation.

    “Global Tectonics 3rd ed”., Kearey, Klepeis, & Vine

    In “Plate boundaries, rifts and transforms in Iceland” Páll Einarsson notes that one of the requirements for a crust blocks to be described as a defacto microplate, is that it must have definable rotation poles. He then goes on to note that relative poles that fit the Hreppar Microplate.

    Specifically, 65.2°N – 20.1°W (North American Plate – Hreppar) and 62.8°N – 21.3°W (Eurasian Plate – Hreppar) relationships.

    While the boundary is easy to spot in the lines of activity and faults, specifically which chunk of dirt belongs to who gets vague when you pull in close.

    This is a rough layout of the boundary and the rotation poles (from Einarsson)

    I mention all of this since the Tungnafellsjökull quake activity is along the lineament moving into the triple junction area at Bardabunga.


    • Could we have here an explanation for the strange earthquake series which have taken place sometimes during the latest years south of Blöndulón (the lake to the north of Langjökull)? Because, if we stretch the western lineature of the Hreppar plate northwards, we could exactly lend at the spot of these quakes. So that they would be tectonic and explained by stresses caused by movements of the Hreppar plate around its western axis as shown in this very informative plot (thanks to GeoLurking). 🙂

        • I think Inge is right on spot, explaining both earthquakes in Blöndulón, as if the northwest corner extended northwards, and earthquakes in West Langjokull, as if the northwest corner extended westwards.

          I add another interesting insight, that the most tension is placed where the microplate sinks under the Eurasian plate (as Carl often speaks), under Hekla (the opposite corner), with tension extending towards Katla.

          The other two corners are also very active: earthquake-wise in Hengill, and volcanic and earthquake-wise in Bardarbunga, with the corner activity extending into Grimsvotn.

          We can also see one side of the plate causing a side-slip motion, along the SISZ, and another strange kind of movement, also in what seems the microplate slipping over or under the Eurasian plate over the dead zone.

          My only question is: is the microplate oceanic crust or a piece of continental crust? But it clearly explains all the SISZ, Hekla-Katla, dead zone, and Bardarbunga neighborhood activity.

          If this is so, then we must expect, when something happens along the microplate, a readjustement of tension over the other sides and corners in years following.
          For instance, Hekla has been active over past decades, and the SISZ side readjusted in 2000 and 2008. Obviously, there is a lot of tension that needs to be released in some sides (over the western side, between Langjokull and Hengill, but on this area, the tension is probably of a spreading type). And also tension has acumulated over the dead zone side. If the plate is twisting/rotating more anticlockwise over its southern side, then we expected most of the tension still to be released just around Hengill and north of it, and to the east of Hekla and in Torfajokull.

          • It is magmatic crust, the plate was creates ad the MAR divided into two volcanic rift zones.
            The eastern zone extrudes towards the Hreppar and towards Aurasia, and the western towards Hreppar and the north American plate.

      • There is the map re. (a.m.) the earthquakes I am talking about: http://www.vedur.is/um-vi/frettir/bigimg/2109?ListID=0 (the red cluster between Langjökull and Hofsjökull)
        Could it perhaps also be an explanation for the quakes in Tvídægra? (to the west of Langjökull)
        IMO (monthly report from Dec. 2010): “Þann 5. desember hófst jarðskjálftahrina við Tvídægru í Borgarfirði og mældust þann dag tæplega 60 jarðskjálftar. Jarðskjálftahrinan hélt áfram fram til 10. desember og þá varð skjálfti að stærð 2,7 sem var stærsti skjálftinn í hrinunni. (…) Við sunnanvert Blöndulón voru staðsettir fimm jarðskjálftar og var stærsti skjálftinn 2,5 og mældist á gamlársdag.” (my translation: “On 5th of December began an earthquake series at Tvídægra in (the region of) Borgarfjörður and 60 quakes were registered on the same day. The earthquake series continued til 10th of December and then there was a quake of magn. 2.7 which was the biggest of this series. (…) South of Blöndulón were 5 quakes and the biggest of them was magn. 2.5 and registered on Sylvester day (31th of Dec.).”) http://www.vedur.is/um-vi/frettir/nr/2109

      • Because, if we stretch the western lineature of the Hreppar plate northwards, we could exactly lend at the spot of these quakes.

        Won’t work. But don’t be disheartened. North of the Hreppar is the purported Tröllaskagi Microplate. It’s western boundary, though not as well defined, is believed to run through that area. The existence of the Tröllaskagi Microplate is not as well accepted (uncertain western extent) but it fits the bill. It is also possible that it’s western boundary is the old MAR lineament before it moved to it’s current location down through Bardabunga. (that actually makes sense to me) Even if it is not a full blown microplate due to being partially sutured to the North American plate, it is at least a crust block unto itself and has some range of motion due to the prevailing stresses.

        Which leads me to something I have been thinking about.

        As mentioned, microplates have a rotational axis that they pivot around as they are shoved across the surface of a sphere. This point doesn’t have to be in, on, or near the actual plate, just somewhere on the surface of the sphere. But that’s only thinking in psuedo 2D. (surface of the sphere) There is a 3D dimension. Shouldn’t there be some vertical aspect of the blocks movement? One side being lifted while the other drops?

        I have thought about this quite a bit with the Souther California crust blocks in and around the San Andreas/San Jacinto/Elsinore/Yuha-Wells faults. As some of you know, I was tracking quake clusters moving up and down the San Andreas/Imperial fault system. Once the cluster arrives at Yuha-Wells (a transverse fault that cuts across from SW to NE) the ability to track them goes to shit. It’s as if whatever energy/stress that is propagating north hits that cluster of rubble and is lost in the mess.

        We know that the transverse mountain ranges there are due to the locked configuration of the San Andreas… (wrench fault) The locked portions pushes up the mountains and the other end of it stretches and subsides (Salton Sea basin).

        So why could a crust block not experience a few mm of lift or subsidence? That would take up a farking arseload of energy and could explain why the “stress waves” tend to disappear in the mess. It would also give Carl a source mechanism for the oddball magma chemistry of Hekla. That slight push down may be all that is needed to increase the melt of pre-existing continental crust that is embeded under or in Icelands seeming “crust plat on crust plate” configuration,

        Ehhh… just kicking it around in my head.

        • Yes, I think it makes sense to visualize a anticlockwise twisting/rotating microplate, while it tilts up over Vatnajokull and sinks down on its southern side, resulting SISZ bookshelfing slipping and Hekla where the plates meets a squeezing with the spreading Eurasian side. The microplates uplifts to the eastern side, creating a thick crust under Vatnajokull and big eruptions there as well, extending between the dead zone and Askja. The slipping down motion starts somewhere at Hengill and moves eastwards, but its only at Hekla that it meets an opposite spreading plate and makes a subduction volcano. I also think that Katla abnormal intensity is also explained partially by being near the squeezing of the microplate, the subduction near Hekla and the uplift under the dead zone. North of Hengill the tension is very minor, only spreading and a subtle sinking as we move past the spreadinf rift (actually very clear when you drive past Hengill eastwards, you see the terrain suddently sinking, where the largest earthquakes happen).

          • are all those type of tec plate converging only happening in the northern part of the globe, but then there is a lot more land mass then in the south ??

          • Southern Hemisphere has it’s share.. more so in some cases.

            At the Galapagos, there is a plate fragment that is slowly rotating in a circle, spun by the monster primary plates on either side of it like a ball bearing.

          • @ Ursh, here’s a map of the large plates:

            There are also smaller plates, like these in Iceland and e.g. Mediterranean is split into several smaller ones, but the general outlies are here.

      • That earthquake series is because of friction between WVZ and SVZ (Skagafjörður Volcano Zone) from what I can tell. Both volcano zones are getting extinct with time (takes few million more years). This earthquake swarms are interesting, as they suggest that more activity might be in the pipes in the future, next 10 to 50 years or so. Until it goes dormant again for unknown amount of time.

        Yes, I do know my geology.

  9. And for those who want to see a giant lava field in Iceland:

    Þjórsárhraun is the largest lava field on Earth, since the last Ice Age. This huge eruption of Bardarbunga about 8500 years ago, created a fissure at the Veidivotn region (our “dead zone”), and lava just flowed all the way down to Hekla, and from there to Selfoss, very close to Hengill. It actually passes just where I live, between the rivers Hvitá and Þjórsá. So if I would be here 8500 years ago, we could watch a lava river of about 150km long, and up to 20-30km wide! It would probably have look like the end of the world 🙂 Its quite amazing to follow the extent of this extremely long lava field. The lava rocks still look quite recent. In my house, a little bit of Þjórsárhraun, there are some similar lava rocks, but very round and eroded, so I guess there was even a larger Bardarbunga eruption before that one.

    The Þjórsárhraun Bardarbunga eruption makes Laki much smaller. Laki flowed about 60km southwards into the sea, and is already a huge lava field, one that is very worth visiting, because of its immense size and still very clearly visible, but small compared to Þjórsárhraun from Veidivotn fissure. Another large one is Eldgjá, which came from a Katla eastern fissure, but now partially covered by Laki lava field. The Eldgjá canyon is a geological piece of art, it is the largest volcanic fissure/canyon on the planet (at least it is one that you can clearly see).

    This long weekend I also went not only to these lava fields but also to the mighty and little known Oraefajokull, which deserves more attention that it is given. This mighty volcano is on par with Hekla by having the largest historical eruption in Iceland, in 1362, with 10 cubic km of tephra. That is more than the 1104 Hekla eruption (but less than the pre-historic Hekla H3 eruption). I went there and discover to the southeast base of the mountain a huge pumice field. I am now happy to have found the third pumice volcano in Iceland, after Hekla and Askja. Askja 1875 also ranks very high on the top of the largest historical eruptions in Iceland.

  10. The Þórsáhraun flow is all grown over. As you drive East from Selfoss you notice a hill, drive up it and a few minutes later you drive down it. And then its flat driving until you get just west of Vík. But if you knew what you had just climbed over, you would be impressed.

    • You missed a lot of it. From the ring road, you only see a bit of the lava field and probably you would miss it if you do not stop and look. In some parts you can see the lava field covered by moss, and if you walk on it, you see that those are recent lava rocks.

      They are easier to see between Hvitá and Þjórsá. There are many exposed and quite clear parts of it. Even inside the town of Selfoss. Its easy for me to look at it, because I am here every day. Its also easy to spot at the beach to the south. And in many instances along the margins of both Hvitá and Þjórsá. I will update one of these days a good photo of it.

  11. Any idea what the red glow is on top of Etna. residual heat from last paroxysm or heading for a new one?

  12. Thinking it all over again, we could gather all the information provided by Carl + Lurking + Irpsit and risk some speculation about the outcomes of present deglaciation and consequential rebound.
    Yes, quakes in Tungnafellsjokull are tectonic, but it doesn’t mean that they couldn’t be a sign of reactivation due to deglaciation.
    Hreppar Microplate, yes! Cool stuff !!!! Reminds me of the excellent series of posts Boris has written about Etna, where he explains a similar mechanism called “slab rollback” (similar, at least in my poor understanding of things). http://scienceblogs.com/eruptions/2010/08/mount_etna_-_brief_anatomy_of.php (already in treasure?)
    Still never forgot Carl’s vortex-theory applied to magma, and I tend to think of Bardarbunga’s geodynamics as being a mix of microplate rollback + rotation and subduction + mantle plume all squeezed under a great mass of ice. If it weren’t for that reason, I think Bard would function pretty much in a similar way as Etna.
    Now, if we remove the coating, we could be seeing another Þjórsárhraun Bardarbunga eruption in the coming centuries, as Irpsit holds.

    • I should though note that I was wrong on that theory.
      But it was fun, and it in one small part was correct, it had the microplate spin built into it. 😉

      But, the microplate I know the spin-direction of is spinning clockwhise with Theistareykjarbunga as the pivot point.

  13. Two very shallow earthquakes directly underneath Mount St. Helens.

    M 2.0, Mount St. Helens area, Washington

    Date: Saturday, April 7, 2012 02:27:12 UTC
    Friday, April 6, 2012 07:27:12 PM at epicenter
    Depth: 0.60 km (0.37 mi)

    M 1.9, Mount St. Helens area, Washington

    Date: Friday, April 6, 2012 16:41:41 UTC
    Friday, April 6, 2012 09:41:41 AM at epicenter
    Depth: 2.30 km (1.43 mi)

    • thanks for the head’s up Tyler!

      ‘Lo everyone! just dropped in to see what was shaking, spewing or whatnot.

      Found most of my relatives on mom’s side in the census release, once I get dad’s tracked down i’ll be able to get back to the present.. well, maybe a little side trip to the PNW seismo blog first.. 🙂

    • Ah, thanks a lot for that Renato. Now I can take painkillers and try to sleep. I just wanted to watch for a while in order to be first to see an eruption, just for once. 😉 *sigh*

      Night all.

        • After seeing how much SO2 Etna produced during the last eruption I think that Mamma needs to eat more bean-stew before the next appearance. Gódabunga how it must have stunk at point zero.
          I am actually wondering if the decrease in between eruptions could be linked to an uptick in more gaseous magma arriving.
          *enter Boris hitting me with a stick*

    • How so? Check the time of the (blue) spikes with the time of the earthquakes listed on the IMO Vatnajökull chart.

  14. Newby and everyone,
    Let us all give some time to think katabatically about the hidden meanings of these Lent days.
    With Persephone and her yearly descent to Hades, spring returns when she rejoins her Olympic mother, Demeter.
    Subducted crust disappears in the mantle and returns in the form of lava.
    Such are Nature’s cycles.
    To all of you, volcanophiles, Merry Easter!

    (and awaiting the return of Mots Fo). 🙂

  15. Now I think I will have to go and read for a while after getting waffled halfway into oblivion… 🙂

  16. There is a lot of discussions this evening on Avcan Facebook about noises being felt on the island and one person has been feeling dizziness today.


    ‎21:39 leve. con un ruido extraño, como un eco, “rodar piedras”

    mild 21: 39. with a strange noise, like an echo, “rolling stones” (Translated by Bing)

    47 minutes ago · Like · 2

    Goodnight, not much leermelo in disconnect, only to tell you that today has been a day quite moved, no, are not as in days gone by, so sudden, these are short and often dry, the feeling of dizziness to been more accentuated that days and the pressure of the ears at times, manifests, but mild… have filled about 5 Parties so far inspecific hours and all clarified that you notice continuous vibration.

    • Another person has said there is a smell of rotten eggs in La Restinga


      ,, Ojalá no se equivoquen en esconder lo que sucede en la isla del Hierro y sea cierto que el volcan se esté apagando, pero lo que se comenta y no por personas que aquí escriben habitualmente, es que en la Restinga, aún se huele a huevos podridos, que se ve el pescado sobre todo grande muerto flotando en el agua…

      Hopefully make no mistake to hide what is happening on the island of iron and it is true that the volcano is shutting down, but what he says and not by people who write here regularly, is that in la Restinga, yet is it smells like rotten egg, which is especially large fish dead floating in the water… ,,

      • “Shutting Down” is a misnomer. “Quiescence” fits better. All it takes is a minor shift in the forces at play and those who loudly proclaim “nothing to see here” will have a bit more to worry about than where the next check comes from.

      • Hello Judith, how is hubby doing? (thanks gain to Geo for my ability to do the Alt 63).. I see from Earthquake-Report.com that Armand, usually so impartial and calm, seems to be getting a bit hot under the collar with the authorities in El Hierro.. see quote below copied from his site:
        “The blocking of the webcam is another example of the narrow minded spirit of local politicians. The island of thousand volcanoes does not want to show any stirring in the Las Calmas sea anymore. The reason they gave for it is simply ridiculous. What will they decide if on a certain day the cone gets above the surface and stays active for several years like in Hawaii. Would they close the webcam view also ?”

        • By the way Judith, how is the weather in Fuerteventura today? We are having a lovely Easter weekend…..it is incredibly , …RAINING in Tenerife today – although not very cold @ 15c this evening,although rain has been way overdue, and I expect the farmers at jumping with joy…..we have spent absolutely ages without rainfall.I just feel sorry for all those tourists that arrived on Friday expecting wall to wall sunshine…

        • Hmmm…………….but Armand does have a point. A working webcam would enhance tourism & the cost should be minimal.

      • Uhm…
        That translation hid something important.
        “In La Restinga it stinks of rotten eggss, and there are very dead fish floating in the water.”
        Note, the fish are floating in La Restinga.
        There has never been dead fish floating in the harbour before.
        Wonder if there is gas sepage in under the city. Because as far as I can get the wind is not blowing from Bob towards the port.

    • Have you accepted this at face value? In a population as large as that of Hierro, I’m surprised that only one person feels dizzy as I can assure you that there are far more who do here where I live, every day of the year, without the need to blame a volcano. Also, there are effects known as logical complementation and psychosomatism where those affected genuinely belive what they have seen/felt as well as there are people who have experienced nothing but need to satisfy their desire for attention. With all the talk on the web about the Hierro eruption not being over, I’m not surprised about this development.

      Next thing that will happen is that I will get slammed for being an insensitive so-and-so, vilely accusing people genuinely afflicted etc.

      • I did not see any slaming 🙂
        You are quite right, there are probably 1 in 100 that are dizzy at any given moment at El Hierro. Hm… 1 in 10 if we count in the imbibing.
        It is natural for humans to blame other things than the obvious culprit in cases like this. Instead of going to the doctor dreading to her that you are sick, blame the volcano.

        If and when the volcano picks up speed, it will not be noticed like this.

  17. Here’s another one.

    08.04.2012 00:16:17 64.764 -17.807 2.7 km 2.0 90.02 13.1 km ENE of Nýidalur

  18. A lot of stuff happens in an earthquake.

    Drifting back to my musing… by my estimation, the crust block that is bounded by Yuha-Well, the San Jacinto, and the Elsinore fault (topped by the furtive San Andreas as it turns west at the locked segment) is about 225 km long, 40 km wide, and according to


    is somewhere around 13.9 to 16.2 km thick… at least to the bottom of the seismogenic zone (that part that makes quakes). So, for the sake of argument, 15 km. (the average listed in the paper).

    That defines an area of about 135000 km³. If you assume a density of 2700 kg/m³, (granite), then the mass of this block is about 3.645 x 10^17 kg.

    In order to lift this block by 1 mm, you would need to expend about 3.645 x 10^14 Joules of energy… or about the size of a Mag 6.5 quake.

    Not that a single 6.5 could do that, stress vectors are all over the place during a quake, but that is about the amount of energy that would be needed.

    That is.. unless I screwed up the math.

      • Happy Easter.

        I have hidden easter eggs in the garden for my nieces in previous years. This year there isn’t enough leaf cover to do so (also the nieces are a bit older). The January / February flowers were late – got them in late February / early March with the March flowers. But the trees are only just getting leaves now.

        • Got to be careful of those eggs. One grand kid learned what H2S smells like when he found an intact egg from the previous year.

          Scared the carp out of him when the egg ruptured and gassed him when he grabbed for it.

    • Thanks for the good wishes Diana, what a stupid time to hurt oneself, just as all the gardening needs doing. When you see the garden growing and eggs hatching and the lambs being born you can understand how much of the Easter celebrations were borrowed from the Pagan fertility celebrations pre-dating the Christian celebrations. Fascinating to consider.

  19. Interesting earthquakes at Vatnajokull, it seems to be like a ripple effect, and there seems to be earthquakes at Tungnafellsjokull, Askja, and actually on Kistufell.

      • I do think that this means an increase on the hotspot activity. Magma is pushing from deep under Vatnajokull. It will find a way up sooner or later, in some place around Vatnajokull, probably more than one time, and probably in more than one single place.

        I do not believe in the conventional view that these volcanoes are not related. I think that their source is only one, the hotspot, at least the ones in 80km distance around the hotspot centered somewhere under Bardarbunga. We often see volcanoes in Vatnajokull erupting in relatively proximity in time, over a couple of decades, and then sleeping over longer periods. For example, look at the 1720-1730 decade for an interesting example, or for the 1862-1885 period. I think we are approaching one of those periods again.

        • I think you are not alone in this. It’s just one of these volcano-tectonic episodes depending on scientists like Páll Einarsson etc. 🙂

          • So the source of the volcano-tectonic episodes are Páll Einarsson?
            Sorry, could just not shut up 😀

          • No, just meant that he was talking about it.

            Could be a bit force exhausting to agitate these mountains so that their magma comes out! But if we all get together… – it could always be worth a try with Hekla at the summer barbecue! just so to get it over with!

          • I would though not rule out that there is a certain volcanologist on El Hierro who could achieve critical mass…

        • If Inge’s take on the quakes at Blondulon (sp?) is correct, this is just rotation at another junction. The interesting part is if and when the inferred rotation of the Hreppar microplate leads to an upwelling of magma (probably thousands of years, 😦 unless, of course, if you’re a bhuddist…).

  20. Happy Easter everyone, from a content dragon who just ate some more spam. ( burp)
    I think something is on the move. But the Grimsvotn eruption clearly showed on many tremor graphs and even though sau is not working correctly and grimsfall seems to be disconnected, i dont think there is volcanic activity going on right now. That would look different.

    • Spica, I hope you breathe fire on the spam and fry it before eating it. Much more tasty and a deserving end for any spam that tries to get past you. 😉 Thanks for you good work guarding us all.

  21. The problem is guessing what will the next spot to really erupt. We know where magma is pushing upwards, under Katla, probably under Veidivotn but more certain under Hamarinn, under Grimsvotn again, under Kverfjoll for several years, even Esjufjoll, and under Askja and Tungafellsjokull recently.

    Iceland shows us that volcanoes do not need much inflation or earthquakes before an eruption.

    The 1973 Westman Islands eruption occurred without any earthquakes, and in a volcano that was sleeping over more than 5000 years, and this was right on the middle of a city, in the middle of a winter night! The only warning was probably the eruption 10 years before in another volcano southwest of it, Surtsey, which had just a bit of tremor and minor earthquakes a few days before its eruption. This is how suddently things can be in Iceland.

    These tremors at Askja and at Skrokkalda are indications that magma is pushing upwards, and those might be close to places of a future eruption.

    • Almost all of the SILs in Iceland have been showing an increase in microearthquakes in last 2 days. The source seems to be somewhere around the northwest of Vatnajokull, where it is mostly visible.

    • The known inflators are in order from Jamies house:
      1. Krisuvik (spouts of it)
      2. Hekla (slow and steady)
      3. Katla (Close to Austmannsbunga)
      4. Grimsvötn (Ever the Usual Suspect)
      5. Upptyppingar (Had an inflatory period)
      6. Askja
      7. Theistareykjarbunga

      The rest of the volcanoes are either not inflating, or inflating on a scale that drowns in the general noise of all the other signals disturbing the GPSs.

        • Thank you!
          I also forgot Hromundartindi that had a rather long inflatory episode.
          And, I would not be surprised if Svartsengi did not have a bit of one earler this year, but this is speculation on my part.

          • I think it was in 2007 that I was hiking at Ölkelduháls and the guide (not me in this case) who had been there very often, explained to us that the hot springs there had developed a lot during the last years (more of them, and bigger ones). – Photo of one of the hot springs:


      • Those are inflating and clear suspects, but I think many other volcanoes do not have GPS measurements. I think we do not have data for Bardarbunga, Oraefajokull, Tungnafellsjokull, Hofsjokull or Torfajokull.
        Even Askja is apparently measured only once a year, during the summer. Not so much data…

        For some other spots, data is lost to the deglaciation uplift, so measurements are not so reliable to predict magma uplift.

        I am not sure if eruptions can happen without any uplift at all. I guess yes, if the chamber is already full when measurements started. So, with that with mind, surprises can be expected if we only look at GPS readings.

        • Yes, an eruption can happen if the chamber had been filled well, but it would take some increase in pressure like a final spout of inflation. Like happened at Eyjafjallajökull.
          Regarding Heimaey it did not have a GPS station, and most likely had an inflation before erupting. And that was a rift eruption, not an eruption in a central volcano. And those behave a bit differently.
          Torfajökull would show well among those that you mention since it would be picked up on the stations around Katla, Eyja and Hekla. Also Bardarbunga would show as it would make a rather distinct signal on HAMA and SKRO, you might miss a small car, but Bárdarbunga is a huge truck.

    • IIRC, the Vestmannaeyar eruption was preceded by quite a lot of earthquake activity that started far out in the ocean and as it got shallower moved towards Vestmannaeyar. The last few quakes were offshore, so there was little indication that the volcano would erupt almost in the churchyard. If I recall correctly, that is.

  22. The main bulk of the earthquake activity during the night was tectonic, even those that are close to volcanoes (Kistufell and Kverkfjöll). It is the time for the seasonal ice load diminishing as the Vatnajökull start to melt. The quake swarm at Tungnafellsjökull (Tungnafjöll) rattled things loose.

    The obvious exception are those two quakes over at Herdubreid. Those where magmatic as far as I can tell. And that would not be so odd really with an slowly activating volcano.

    • I do not know if the ice load diminishes that much. At most it melts a few meters on the surface of a 600-1000 thick ice cap. At most the glacier might retreat 1000 meters at its edge, but volcanoes are mainly well into the ice cap.

      I never understood why the summer seems to trigger the activity in Katla for example, because the ice cap is always there, the thickness of Myrdalsjokull maybe decreases from 610 to 600 meters thick, lol 😉 But eruptions there occur much more often during summer and autumn than the other seasons.

      • It actually makes a rather large impact. At the center of Vatnajökull the seasonal swing is a whopping 37 millimeters on an average year.
        The same thing also goes for Myrdalsjökull, even though the seasonal shift is smaller due to the jökull being smaller. So it could probably have something to do with the likelyhood of summer eruptions.

        • And results of scientific studies show that there was a significant up in the number of volcanic eruptions after the last Ice Age, in Iceland around 10.000 years ago.

          • Hm, quantitative analysis, I wonder…

            How do scientists identify and date eruptions? By looking for the by-products of an eruption; lava fields, tephra layers, scoria cones etc, then dating it. Since we’re talking 10,000 years and more ago, the only reliable dating method is the Argon-Potassium isotope method which has a margin of error of+/- 10%, meaning that two separate eruptions 9,500 and 10,500 years ago fall within each other’s error zone and unless physically distinctive may be interpreted as a single eruption. During glaciation, this is much more likely to happen than after de-glaciation.

            The main problem though is that most volcanic eruptions do not posess the power to break through a uniform ice-sheet kilometers thick, so they would have been subglacial and not left behind easily identifiable, distinctive indicators of the vast majority of eruptions, so most likely the number of eruptions pre-deglaciation is severely under-estimated.

            Take Herdubreid as an excellent example of this. Herubreid is a tuya, a mountain built by subglacial eruptions. The only visible eruptions post-glaciation is small lava flow on the flat summit with an itsy-bitsy, teeny-weeny little scoria cone on top. Just compare the volume of those two, the tuya and the scoria cone! The tuya was not built during a single eruption!

            If we assume an average erupted volume of 0.02 ku cm, similar in size to the Fimvörduhalsi eruption and likely to judge from the miniscule lava flow and scoria cone atop Herdubreid, and guesstimate the volume of the Herdubreid prominence to be on the order of 10 ku cm, we arrive at a figure of 500 eruptions to account for Herdubreid tuya. If we push the figure up to the 2010 Eyjafjallajökull size, it’s 40 such eruptions. This gives us a minimum score of pre-deglaciation 40 against post-deglaciation 2.

            The idea that the number of eruptions will increase after deglaciation is a hypothesis currently in vogue. That being the case, of course you will get scientific investigations that set out to prove this anc claim to have done so. However, as I have demonstrated, I’m pretty sure the results arrived at are due to muddled and wishful thinking.

          • You are taking it the other way, quite interesting take on it. But the rest went looking towards today.
            As far as I know, no studies have really been done for the glacial age, just for the reasons that you state.
            The theory that eruptivity was higher after de-glaciation is compared to todays eruptive behaviour, not compared back in time.

          • Saying that postglacial isostatic rebound generates more eruptions is a bit like saying “All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us?” :mrgreen:

          • And education (Athens), wine (summerians or georgians, about 4 000 years before the Romans, let them fight it out). Public order (the Babylonians)…

          • Then we have the 3 000 year old water toilett I used up in the Atlas mountains in an abandoned town. All houses had (still) functioning water toiletts constantly flushing away the products.
            On creek where run as toilett flusher, another to get fresh water. All houses had a hole to take up fresh water.

  23. @Bob:
    After going through the data for Bob I think that we will see a reactivation of activity in the next 3 to 5 days. After the earthquakes in first 4 days of April, the changes in combined motion of H101 GPS, and the renewed activity at EGOM and EOSO of the 0,59Hz and the 0,27Hz frequencies (large enough to show on all islands now) there seems to be new magma arriving from depth.

    I think we will see one of two things happening.
    1. Bob starts to erupt again.
    2. Pressure will build up in the system and a new fissure opens up closer to land, or on land. For this to happen we will most likely see renewed earthquake activity as pressure builds up.

    Since this is a fissure eruption there is a distinct chance that the only warning for a new fissure is that sulphuric gases increase. I hope that they are still actively measuring that within La Restinga.

    • The Sturkell write up is a very good popular science starting point to understand what the current research is about.

  24. Hello All,
    Newby; ouch x cracked ribs very painful, I did one of mine not so long ago, remember to breathe normally, keep active and cough even if it’s painful, pneumonia is the danger x
    I’m back from la Palma (was chilly at times, hope you enjoyed the heatwave in the UK, always happens when I go to The Canaries, that or snow…) We did some nice walks including Ruta de Los Volcanes and Teneguia/ San Antonio (I can confirm that la Palma is one of the 3 steepest islands in the world… It’s a function of land area x height so they not sure which is number 1, depends how you calculate it…) Guess what I found in a visitors centre… ISBN 9788472071902 is the google search for those of you into Canary Island volcanoes 😀
    Armand reports that the latest Bathymetry shows no increase in cone height…
    I’ve read the last post on BoB but there’s no way I can catch up on comments, any interesting schtuff been debated here? Any new plots I should know about etc?

    • Hi Schteve42. The warm weather was great. See you bought the cold weather back with you! Did you make it to El Hierro? When I checked travel out, it did not look easy to get to from the UK. Is the book you recommend available in English?

      • Oh yes, I read Spanish well enough for the newspaper, not well enough for scientific tomes… Didn’t do El Hierro (there was enough vulcanology on La Palma and too difficult/ expensive) , it’s pencilled in for the future… I’m kinda glad though that there was only a faint Jacuzzi to be seen… 😉

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