El Hierro – Signs of a possible coming eruption

Lava field on El Hierro with a couple of volcanic cones in the background.

Lava field on El Hierro with a couple of volcanic cones in the background.

As Christmas moves towards Boxing Day it looks more and more as the volcano of Tanganasoga on the island of El Hierro in the Spanish Canary Islands is closing in on a new eruption. Since the last eruption the seismic activity has continued in a subdued fashion, but not in a way that really was pointing towards a new eruption starting. Well, at least up until the last few days.

I remember quite well the run up to the last eruption, it started with a large earthquake swarm as magma from deep down either formed or moved up from depth via the mantle plume. This swarm continued for quite a while and waxed and waned for months until harmonic tremor at low levels set in. The harmonic tremor slowly built in strength as magma moved into the system and pressurized it.

Suddenly a conduit opened up that lead from the central magma reservoir under Tanganasoga. The conduit was deep and followed roughly the southern fissure line, via the village of La Restinga out into the ocean where it burst forth from a new vent that we named Bob after a character in the TV series The Black Adder. As the conduit opened up the harmonic tremor went quite literally off the chart within just a few seconds. Between the earthquake swarm and the conduit opening up there was an episode of significant uplift.

The location of the latest swarm, reaching from Tanganasoga out towards the eastern side of the fissure swarm leading to Bob.

The location of the latest swarm, reaching from Tanganasoga out towards the eastern side of the fissure swarm leading to Bob.

As the eruption out in the ocean ended no significant deflation was noticed, a sign that the system was still fully loaded with magma. This will most likely explain a few things that we see now.

The Current Situation

A few days ago an earthquake swarm started under El Hierro, it is so far the largest swarm since March 2013. That swarm was significantly larger, but did not in and of itself entail any significant risk for a return of eruptive activity. Most likely the March swarm was internal movement of magma in the system.

After the current swarm a few other signs started to show. One was the onset of inflation, and the second was a steady rise in Radon being emitted from the bedrock of the island. Currently the inflation ranges from 30mm to 50mm in the affected areas, with the peak following the same fissure line that leads towards Bob. Also the current level of Radon is now ten times higher than the baseline level at El Hierro, with a current reading at 2250Bq/m3. I will get back to the Radon at the end of this piece.

What differs are the shape of the earthquakes, this time they have a distinct signature that has 3 significant indications. I will here describe the earthquake shown below. It has a magmatic component, and on the drumplot we see that it is a Long Period event so it is pressurizing the system. On top of that it has a very interesting coda, as it progresses the frequency starts to drop dramatically, and that is a sure sign of increased volume, ie that it is opening up a new conduit, sill or dyke. This was a very telltale earthquake that proved that new magma moving into the system.

Notice how the frequency rapidly shifts towards a lower frequncy, this is dopler shift due to a pressure drop due to a volume increase. This only happens if there is fluid medium filling a system.

Notice how the frequency rapidly shifts towards a lower frequncy, this is dopler shift due to a pressure drop due to a volume increase. This only happens if there is fluid medium filling a system.

Almost picture perfect Long Period event with an initial stress loading face, and a latter part that is stress release. Clear magmatic event.

Almost picture perfect Long Period event with an initial stress loading face, and a latter part that is stress release. Clear magmatic event.

After that earthquake harmonic tremor slowly started to creep into the picture, so far it has increased slowly but steadily with a couple of highs and lows.

It is interesting that the pattern is repeating itself so much for the volcano, only real difference is that the pattern is progressing faster, and that it showed quite fewer earthquakes for the other signs to show up. This is most likely due to the fact that the bulk of the eruptible magma that arrived during the previous eruption still is down there in the magmatic reservoir of the Tanganasoga volcano.


This is the highest level so far of harmonic tremor.

This is the highest level so far of harmonic tremor.

If the uplift continues, the radon stays at the extremely elevated levels, and the harmonic tremor continues to increase, there will most likely be an eruption. If so it could happen anytime from within a few hours to a few weeks. It is currently hard to say what will happen, where it will happen and when it will happen. I do though not think an additional earthquake swarm is necessary for an eruption to start, since there is already a lot of magma in the volcanic system.

Currently it looks like the most probable spot, if an eruption occurs, is along the fissure line leading from Tanganasoga past Bob. I guess that an eruption out in the ocean is more likely, but that it probably will be closer to land than the last one. There seems to be a bit of evidence that the eruptions along this fissure swarm has moved progressively closer to land. I would though like to point out that there is a risk that an eruption could take place on land, and in that case La Restinga might be in danger.


Notice that the radon count increased before the March 2013 earthquake swarm, and that it later fell down, and then it started to increase steadily during an almost aseismic phase leading up to the current levels that are rather extreme. This is indicative of continued magmatic movement into the system, and upwards towards the surface within the system.

Notice that the radon count increased before the March 2013 earthquake swarm, and that it later fell down, and then it started to increase steadily during an almost aseismic phase leading up to the current levels that are rather extreme. This is indicative of continued magmatic movement into the system, and upwards towards the surface within the system.

Radon is a heavy radioactive gas that causes an assortment of cancers if inhaled in large doses. It has a short half-life and is created as uranium or thorium decays. The most stable isotope of Radon has a half-life of 3.8 days, but most other isotopes have a much shorter half-life time. This means that high concentrations of radon is almost exclusively found near natural uranium ore deposits.

The only other natural place to find elevated levels of radon is around volcanoes that are receiving fresh magma from a very deep uranium or thorium rich source, such as the deeper parts of the mantle. We already know that the mantleplume under the Canary Islands reach at least 4 000 kilometers down. So, as fresh magma moves up from the depth it will cause a large increase in thorium and uranium in the volcanic system, and as they decay radon-gas will be released and as it seeps out of the ground the levels will rise as the magma gets closer to the surface. As an eruption ends, or if the rise of the magma halts the levels will quickly start to fall towards normal levels. Remember that the ground level was down at 250Bq/m3 after the last eruption as this latest magma moved into the system.

Now, how bad is radon for you? Well, radon is a heavily regulated gas. A residence home is allowed 200Bq/m3, an underground mine is allowed 1300Bq/m3, a basement work area is allowed 400Bq/m3 and a nuclear reactor is allowed to have a level of only 300Bq/m3. The current level of 2250Bq/m3 is really high.

I started my career as a nuclear physicist before I moved on towards being some sort of geophysicist. Take this into account when reading this. Prolonged exposure at those levels is dangerous for your health. If you live on El Hierro you should avoid being in a basement, and you should open the basement up so that air can move freely in and out so the gas does not pool in it. You should keep the windows in the house as open as possible at all times. If you live in a house containing more than one storey you should sleep as high up as possible. Since the gas is very heavy compared to regular air it will pool in the lower places of the building.

In an unaired basement the level of pooled up radon might easily reach tens of thousands, if not hundreds of thousands of Bq/m3. At those levels you can be in serious health problems in a very short time. Personally I would not spend even a second in a basement that might contain pooled radon gas. After all, getting lung, lymphatic, pancreatic, bone marrow and assorted other cancers and or leukemia is an over-rated experience that should be avoided.


Update by Geolurking

Today, Harrie brought attention to the spectral traces from CTAB. Looking at it, and piecing together the last couple of days plots, you get what appears to be the onset of a tremor event.

This is not too dissimilar to the plot on CHIE (located in the La Playa scarp area) when the vent (Bob) south of La Restinga began. I don’t know the exact location of Station CTAB, but it is one of the augmented stations that IGN put in back in the early days of the seismic crisis. If this is the signature of degassing magma, it is likely near the station since it is most prevalent there.

Update2, KarenZ located the station graphic. CTAB is closest to El Golfo. The interesting part of this is that there were indications of a lesser reported 2nd vent offshore in this area. I believe that the survey ship even noticed it. (this is based on recollect and may be inaccurate).

The location of CTAB:

Correction, evidently KarenZ caught the first spectral plot showing what it likely tremor. (December 26, 2013 at 00:11 post) I didn’t catch that until later. (sorry).

214 thoughts on “El Hierro – Signs of a possible coming eruption

  1. Carl. thank you for the summary. What is the likelihood of property damage from the uplift, which is up to 5 – 6cm near HIO8 and HIO9 and nearer to 4cm elsewhere?

    • Not that big really since it would be uniform uplift over a large area. It would take almost unrealistic bad luck for someone to own a house that was affected by more than 1mm of uplift differential. More or less you would need to have built your house directly over a fault line for any damage to happen. And really, you kind of notice faultlines in the ground.
      A shallow earthquake on the other hand could of course damage a house either via the vibrations or through a crack opening up.

      It took 280 centimeters of uplift in just a few days to damage houses in Campi Flegrei, and similar uplift and movements in the Amatitlan in Guatemala city has been known to wreck, or even swallow houses. But, that is a very much larger motion than at El Hierro. And both of those are real supervolcanoes. El Hierro is comparatively puny.

  2. Long time ago i was here, but now it looks as we will see some more action at El Hierro. My personal opinion is that the Golfo and the Sabinosa will start to shake again, but i agree with Carl that every scenario is open.

    • Merry Christmas Armand!

      I agree, I would not rule those places out either, or even that the central volcano itself get into it.
      But, judging from the location of the most uplift it looks more like the Tanganasoga-La Restinga line. Sofar… But, then I was surprised at the location the last time. I had expected El Golfo then.

      • Merry Christmas to all of you too
        Take a look at stations Ctan, Ccum and Ctab to see much more tremor which gradually increased during the 25th

        • Especially it increased in the 0.26Hz range, and that is the mantle plume moving. I speculated last night that one could by using all 3 axises of those 3 stations track the exact location of the mantleplumes whereabouts using the 0.26Hz band. Intriguing possibility to do a quick down and dirty tomography.

  3. Thrilling developement!
    There is a paywalled 2013 paper by you-know-who on radon emission prior and after the volcanic crisis 2011/2012:
    And in this abstract I read that prior to onset of seismicity 2011 elevated radon values of up to 1.6 kBm-3 were measured:
    Here a map of the monitoring stations:
    As for ventilating the buildings, it is fortunate that temperatures have been mild 14 to 20°C today.

    • Interesting that You know who was hiding this tidbit and saved it for a paper. Hiding that half of the island is risking getting cancer is bad, really bad. But, then I am not surprised.

      • I need to figure out what the bq/min exposure rate to radon you guys are talking about so I can compare it to the flux standing on the ground in Denver (above 6,’000′ of atmosphere). Cheers .

        • One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1.


          So, my rough guess would be to multiply it by 60 to get a per minute value.

          How that translates to Seiverts I don’t know. That would allow you to compare to Fukishima.

          “The sievert represents a measure of the biological effect, and should not be used to express the unmodified absorbed dose of radiation energy”

          Each decay instance of Radon releases 8.94 x 10-13 joules of energy. (Alpha decay process, each alpha particle is the equivalent of a helium-4 nucleus. Probably moving at a pretty good clip.)

    • Given the nature of the person… it fits quite well.

      Ya know, given the spread of the deformation and max uplift areas… I would not rule out something in the La Playa scarp area either. There of offshore. And don’t forget, one of the more well known caves has an opening along that face.

      • You did, that would be a “pool” figure though. If I remember corectly that measuring station is indoors in a hut. Aireating is the key to health with radon.
        Here in northern sweden we have gigantic uranium deposits, so in the 70s and 80s pretty much every house in large areas was tested, and many where sanitized with added ventilation in the basements. It is amazing what two small ventilation openings did to the radon count.
        There was one house where they measured well into the Mega-Beqerel, the entire family died from skeleton-cancer.

        • Ah! Thanks for the explanation. Measuring in a situation that encourages accumulation almost seems like cheating, but measuring in a particularly open and windy spot would give a false low reading. It seems that there should be some standard method for this e.g. an inverted funnel over a measured area of ground that is flushed with clean air at set time intervals. Just a thought…

          • There is actually a set standard for measuring. Both for the instrument, and for the environment. But as soon as you get out into the real world and leave the laboratory it gets messier by the minute.
            The important thing in this case is not really the values, it is the changes. Both a closed space and a fairly open spot of ground would still give changes over the baseline for that particular instrument, and sometimes a semi-closed space gives more distinct changes than a non-closed space.
            That is why gut feeling and using several instruments is necessary. Then you can discard whacked out figures, or just use the trendlines.

    • Good measures to prevent radon (when emitted from the ground beneath a building) from entering buildings:
      – permanent ventilation (to outside space!) of basement or any space beneath the ground floor;
      – the ground floor should be as gas tight as possible, better NO openings. Spaces around tubes/pipes in drilled holes in the floor need special attention to be made gas tight.

      • Problem is that you can’t retrofit houses to be gas tight…
        If you have a house on a gas tight concrete sole, then you are fine, otherwise you still have to go with aireating the lower floor…

        • Yes, these measures (like a dense concrete floor) are of course easier to apply to new buildings. However, improving or even replacing a floor is not impossible, only expensive. – Drilled holes are easier to fix. They are very often left unfinished. And ventilation openings (to outside space) are often being shut in order to increase thermal insulation / lower heating costs.

  4. Merry Christmas to you all!! The radon emissions are worrisome – but I also was wondering whether in the Golfo area, with that huge wall of stone and the wind blowing from the West, is not building up much larger concentrations than other places would do , because the gas has nowhere else to go?

    • Since the gas is so heavy it behaves more like a liquid, so it would flow down out over the ocean anyhow. But, in crevasses you would get pooling.

    • Yepp, started out with trying to figure out wave patterns in subatomic particles, then moved on the wave-patterns in general, and that made me go into making radars, sonars and so on… And others migrated my work into seismometers and the like. So, later on I got into that type of equipment myself and had to learn geophysics.
      But what sent me into physics in the first place was actually music (composition studies and audio technology) as I wanted to figure out why sound behaved as it did.
      There is actually a red line in my weird ambling studies.
      I still though envision magma reservoirs as cathedrals with magma being pressed through a church organ playing various notes. I was therefore rather stumped when I saw that tv-clip of Boris talking about Etna as a musical instrument and volcanic music. Kind of proved in my book that Boris is a bright chap :mrgreen:

      • Just got me thinking if how every volcanic eruption was likened to music.

        Would a Plinian eruption be likened to a violent, loud rock song where they destroy all in their path?

        • The mother of all drum solos 😉
          I do not think one should over-indulge on the music analogies. But it works pretty well to get a mental image while you try to understand the pressure changes within a magmatic reservoir. The drawback is though that you must have a pretty good working knowledge on how sound functions to use, understand and work with that analogy.
          Remember that I do not believe it is functioning exactly like music, it is just a model that makes it easier for me to grapple with a few concepts. I guess others have other models.

  5. A short comment on the state of harmonic tremor measured.
    Over night the amount of harmonic tremor energy release has quadrupled in a very slow and steady increase. Very interesting really. If the rate of increase continues unabated we will have the tremor levels seen at onset of the previous eruption somewhere tomorrow. And when I write that I mean the continuous HT measured during the hours before the onset of eruption. The onset itself gave a 32 fold increase in tremor within seconds, so it was pretty obvious back then. I guess the pattern will be the same this time around if we get an eruption.
    Anyhow, something is moving down there.

    • And the GPS is now up around 60-65mm of uplift on the 08 and 09 (La Restinga) stations. The North component gives maximum values on the line between these stations. 08 is being pushed north and 09 is being pushed south. That could mean that an eruption could occur somewhere between these two points. No east component is detected, so the maximum uplift is on that line basing from the publicly available GPSes.

  6. Hi Carl, thanks for a great summary of events. One question about the LP event. To me it looks the frequentie is actually going up. But i might have misinterpreted the sectogram ofcourse.

    If that’s the case, this could happen in a gasfilled vertical collum that’s plugged of. If for some reason the gas is suddenly allowed out, for example a crack forming in the plug, magma could rapidly rush in causing a tremor. As the gas filled area gets smaller and smaller the frequency could go up quickly. I read about this in a paper a few days ago, but i can’t seem to find it anymore 😦

    • I had not noticed that one before. You are of course correct. That would probably be the same magma that first rushed into the new area (dropping frequency), and your formation is when it had filled it and was halted and you get that rapid pressure rise.
      Nice doppler effects at work in magma 🙂

      • The paper suggested a different mechanism. A interaction of compression and decompression of the gas colum slowing and accelerating the inlow of magma. As the gas pocket get smaller the frequency of this oscillation goes up. Sort of an airspring

          • I guess you’re right. A gasfilled cavity at a depth of 10km is rather unlikely. I’ve been reading up on harmonic tremor, but there is so much to learn, so many different mechanics at work, difficult stuff.
            I found this one quite interresting. It suggests that even very small conduits careing high presure steam can cause a very low frequency tremor, 0,63 Hz, by turbulant slug flow. Or better an oscillation between laminar flow and turbulant flow causing an ritmic velocity change.
            I should have gone to university 😦

            • Trust me, you are doing quite well anyways.
              I don’t get it all the time and I have Ph.D on the subject of how waves behave and what might be the cause.

            • All that uni teaches you is how to learn and assess by yourself. You are doing fine! Not many undergraduates would read original research articles except during project. Keep up the good work!

            • ditto on the uni comments arjanemm.. and, hey, you aren’t dead yet. I must be the most stupid one here amongst us as I actually went to university and chose to do philosophy when right next door in the Geology faculty a certain G.P.L. Walker was doing seminal work in volcanology at the very same time. Talk about missing the bus!
              And what you are talking about sounds kind of familiar to “magma wagging” which was proposed by Jellinek and Bercovici as one source of harmonic tremor:
              (and yes I propose to go back and do Earth Sciences as a night-time hobby once I get my life sorted)

            • Thanks for your nice words everyone ! What a nice place this is.This is really a subject of my liking. I play gitar, i was a sound engineer. I built a few small concert halls and i build a tesla coil producing 10 meters of ligthning, I love the subject of resonance.

          • Tend to lurk here (all the time….) rather than comment but this morning’s musings have been fascinating. I agree about the organ and Cathedral: I spent three days at carol services in an English cathedral last week looking at the great organ and, when looking at the pipes, my thoughts always move onto harmonic tremor. This is especially the case on the last verse of Once in Royal David’s City, when the deep bass comes in and you can feel it through your feet! Not religious at all but this still gives me goosebumps as I think about (and feel) HT!
            Interesting thoughts about the radon too Carl – must read that paper when I have the time: Oh that’s right I do, I am on holidays….
            A Happy New Year to you and yours on this site.

  7. Is it tme for flagging “Get ready for next eruption” post ? Here are some saved links from my favorites. http://www.ign.es/ign/layoutIn/volcaListadoTerremotos.do?zona=2&cantidad_dias=10
    Shows there are still near continiues earthquakes, possible wad on its way, I think.
    Anyone have any notion how much CHIE is scaled ???

    • I rather think that CHIE is at the same setting as it was before the first eruption, ie on baseline setting. The larger quakes kind of implies that.

  8. There are intermittent powerfailures at CHIE right now (blue bands), and that is nothing to worry about. Even thought it is a bit irritating.

  9. Hi

    Here is the latest animation for the quakes in El Hierro. Last event is ending at 11h31

    The first part of the video shows an event by event animation starting on the 22nd.
    The left side of the colorbar gives the date.
    Dot size is proportional to magnitude. The scale is given on one side.
    Terrain elevation is shown (see right side of the colorbar)

    The following sequences are a 360 rotation showing all the events and some vertical rotations.

    The last sequence is a zoom centered on the last event.

    Data is from IGN and NOAA, made on Gnu Octave.

    • Thanks DFM,
      Very helpful as always, I think we can confidently say that the head of the plume is located undersea in EL Golfo, initial EQs there have been a common feature of all the previous magma injections/ seismic crises.
      If this is indeed the beginnings of a new eruption, then maybe we shouldn’t be too surprised at the lack of EQs right now, if I remember rightly there was an aseismic phase prior to BoB’s blowout. There was a lot of discussion about a “dead zone” between about 6- 4 km depth as magma moved through pre- existing conduits, so not having to break through, therefore not causing earthquakes. If we begin to see EQs at shallower depths (< 4kms) then we can say with increasing confidence that an eruption is imminent…
      Please remember that these are the ramblings of a VERY amateur volcanophile, albeit one who has followed events at El Hierro closely since near the beginning.

  10. For some background, I found this paper about radon mapping of La Palma:

    “La Palma is one of the most volcanically active islands in the Canarian archipelago, with two eruptions in the last 50 years. At this island, a radon mapping was carried out in order to determine the normal levels of his gas in soils and in the underground environment during a quiescence period and to investigate possible active geological structures. Radon values are in general low, both at surface and in the underground, although weak anomalies were detected into a gallery in the north of the island (200 pCi/l) and at the southern rift (>180 pCi/l), the most active edifice in recent times.”

    Interesting remark:
    “… on Tenerife, another island of the Canarian Archipelago, 80 km to the east (Fig. 1). On the latter, high radon anomalies (>2000pCi/l, local background of 3500 pCi/l). These nomalies are associated in a first approximation to structural features of the Tenerife volcanic edifice and with areas of CO2 degassing (Coello et al., 1993, de laNuez et al., 1995, Martín et al., 1997; Martín, 2002)”

      • So if we add the background radiation of 3500pCi per liter air and ad the anomaly of 2000pCi/l we get 5500 that we convert into Bq 203,5. Now they seem to say that it is a per liter value, but that I do not give a rats bone about, it is plain wrong since that would put the background radon count to 129 500Bq/m3… Background at 129.5 I can buy, not the other value.

        So, now compare Teides values of 203.5Bq/m3 (counted as anomalously high) with El Hierro at 2250Bq/m3.

        • Do you think there is likely to be any equipment on the island that will enable the residents to have the radon levels in their homes tested? I know that in the UK you can get kits for £49.80 from http://www.ukradon.org/ so it would seem a good precaution for anyone living there.

  11. I am still missing the weaker quakes in the list (like they were listed prior to the 2011 eruption). They gave a great clue of were the magma was moving. Now they are constantly filtering them out (to avoid panic i guess). Same with CTIG (who is replacing CHIE). The CTIG seismograph is located on the only location were nothing is going on – no deformation at all – great line to keep the people happy. If you get into the website the normal way, CTIG (former CHIE) is the only graph you get to see, so : np at all right

  12. From the Landslides Blog – paper presented at the AGU Fall Meeting that blames the severity and unusual behavior of the tsunami following the 2011 Tohoku earthquake on an underwater landslide that moved an estimated 500 cubic kilometers of stuff downslope. This is about 5X the volume ejected by Tambora in 1813.

    This may help size the potential threat of tsunami from flank collapse of volcanic islands (Hawaii / Canaries). Cheers –


    • Flank collapse on a volcanic island is going to be point source event. The wave from the displaced water will loose power as a function of distance until the wave adopts a more planar structure, at which point little power will be lost. As for the 2011 tsunami, the entire wave formed as a planar structure when the the equivilant to the entire above sea level volume of El Hierro was uplifted along the fault line in just a few seconds. (or about twice that).

      I think it’s a bit humorous (and a bit pathetic) when the landslide doomers get onto a tear.

  13. Well, one line of thinking from some of the papers is that El Hierro and La Palma swap back and forth as to which one is volcanically active. I don’t think that is what is happening, but it could be a manifestation of the process.

  14. Well, I don’t know what to think. All the seismographs are showing a constant buzz, but none of them corroborate with that sharp jolt at La Palma which should show up at El Hierro too. I don’t know if they are working or not working. If they are working, it looks like Carl is right, and a new vent may have formed (probably off the coast somewhere).. but then again, maybe they are not working. Kind of frustrating.

  15. Okay, after checking all the stations…
    The peak tremor is just to the north of Tanganasoga, there is pretty much no tremor at La Restina. So, judging from the tremor it looks like we might get the long saught after main act of the volcano. There is also a possibility that there will be a northern oceanic eruption.

    • No. Can’t see any recent chatter from them on AVCAN’s FB site either. But would the Christmas festivities divert their attention?

    • There is this blog by Manfred Betzwieser. As far as i know he lives in La Palma but he has connections to El Hierro and visits it frequently, this blog gets updated daily, especially in times of crisis. it is german but in case translation is needed , i could do that ( or chryphia) or quite some others 😉

  16. Synchronicity is the experience of two or more events as meaningfully related, whereas they are unlikely to be causally related. The subject sees it as a meaningful coincidence, although the events need not be exactly simultaneous in time. The concept of synchronicity was first described by Carl Gustav Jung, a Swiss psychologist, in the 1920s.

    The loon sites have been discussing a reported Mag 22.0 earthquake put out by a USGS application. This is obviously an error, but from my point of view what if this is a prelude to an event steeped in synchronicity? Note: There is no real scientific data that supports the idea of synchronicity, just anecdotal evidence. (I’ve seen to too, it just sort of raises the hair on the back of you neck when you see them)

    • FYI… a Mag 22.0 would be capable of producing a surface rupture 977,237,220 km long. (based on Wells-Coppersmith)

      So I’m pretty sure that someone would have noticed it had it actually occured. As an example, the Chixilub impactor that ended the Cretaceous only generated a seismic pulse of about 10.6, and that is larger than anything recorded in history.

    • I don’t think so, or at least it would be problematic. Wells-Coppersmith took the parameters of historical quakes and ran a regression over those parameters to come up with their equations. Once you get above about Mag 9.0, the correlation starts to fall apart. For the sake of argument, and assuming that the correlation can still yield a half ass reliable indicator of the physical attributes of a quake above that level the surface rupture length is greater than the Circumference of the Earth. (40,075.017 km)

      Now… in order to get up into that realm of energy release, you pretty much need an asteroid or cometary impact. Scenarios that release energy of that magnitude, generally leave behind a melt pool since a large part of the impact area is vaporized and thrown into space. Even if it were possible, not many people would be left to care.

  17. Having close look at spectrogram

    I think there is not a big vent open yet in El Hierro, or very small one, at least very deep, out at sea, but I could be wrong. Not on land. I remember noise at Eyjafjallajökull (March 2010) was very high, even before it began erupting (at Fimmvörðuháls.) I think this oonly shows it moving, but not up on surface or in sea yet.

    • CTIG is up by Ville de Valverde, on the flank of Tinor. The original volcano that predates El Golfo. From what I have read, the magmatic system for that one straddles the last chron transition. The greatest hazard there (in my opinion) is the San Andreas failed collapse structure.

  18. So nice to be focusing on El Hierro again. I know it is a tiny blip in the grand scheme of volcanoes but it seems a personal blip to me after following Bob through his birth pangs. Would be fascinating to see son of Bob arrive. New year, new eruption would be great for me, with of course the proviso that it caused no harm to anyone, although there would likely be some disruption to normal life of course. If only the officials of the island could see the tremendous increase in tourists it could bring rather than the other way round. Another Bob would be good, breaking the surface of the sea would be great!!!

  19. Sort of side note… an image I found lurking about on my computer. These are some of the caves on El Hierro. There are also quite a few that open up underwater that have been used for dive expedition destinations.

    I really wish I knew the source of the image. I think it was in a PR pamphlet.

  20. FOX News have some info about the event and the sealed-lips-management:

    MADRID – Spain’s National Geographical Institute says the Canary Island of El Hierro has been rocked by more than 50 tremors in 24 hours, two years after a new volcano began to appear off its southern coast.

    So far the resurgent seismic activity has caused no damage, a regional government spokeswoman said Monday. She spoke on condition of anonymity because she was not authorized to be identified in the media.

    FOX News Link: http://www.foxnews.com/world/2013/12/23/seismic-activity-restarts-on-spain-island-el-hierro-2-years-after-new-volcano/


  21. http://www.ign.es/ign/resources/volcanologia/html/eventosHierro.html

    My guess would be that the magma will continue heading south as it moves towards the surface. It does seem to be further east, nearer El Pinar this time. The lumpy bumpy quakes that preceded Bob were the most worrying manifestation of the unique geology of El Hierro, with the risk of land-slips. The gas is most likely exiting via the tubes and caves already, imho, but the magma I think will soften rock and find its own pressure build-up, wherever it is most concentrated. Diapirs are a feature of this really deep source as it rises towards the surface. Much of it may cool before actually erupting as the island is in deep ocean. I would guess the authorities are counting on it slowing again, like it did last time…

    Thanks guys for the very informative sources – an interesting end of the year for El Hierro!

    • I think diapir time is over. We had that one large fill event that had the leading edge heading off towards Renato Rio, and then a second phase seemed to fill in a sill to the north of that, then it grew quiet until recently. Now the activity is back above the original area where it all started at. If there is no discontinuity between the layers to take the fresh load of magma, the only place left to go it up.

      The way a pressurized system works, is to crack and push apart the grains of the confining walls of the “chamber.” It does this by overcoming the tensile strength of the rock, as augmented by the confining pressure of the material above it. The hoop strength is less on the top region of the “chamber,” so if you have brittle failure, that’s where it’s at. (and the source of “poppers”). As of yet, I havn’t seen any poppers, but they may be hard to locate and won’t show up in any listings until the waveforms are examined by seismologists. The ones for “Bob” didn’t show up in the list until after it was already going.

      Seeing as it is dark there, it is possible that it has already started… somewhere out in the bay. (It’s also quite possible that nothing has happened at all)

  22. There are times I wish I was Lurking… Seriously… If I could plot things it would help.
    Anyhow, a few hours of noodeling on paper works too.
    If you have read Lurkings update up above you will see where the station he is talking about in the update is located. Now, guess where the hypocenter of uplif is? Ta-Daa! It is right down under the star on the map… Go figure.

    • I was thinking on the lines of this wad must follow path of least resistance, following on in south or south east direction, where star appears.. SW and NW sectiors already ‘taken’

  23. I think they have fiddled with the station again. 24th is last day individual quakes can be seen, am I worng the tremour has reached value of 2 mbLbG
    Last biggies’ were these and shallow *only 10 km = might indicate front had reached that depth?
    1251947 24/12/2013 15:04:08 27.6490 -17.9332 10 2.4 mbLg SE EL PINAR.IHI
    1251775 24/12/2013 15:03:41 27.6818 -17.9347 10 Sentido 2.6 mbLg SE EL PINAR.IHI

    I wonder if there is second interface, hidden away from us

    • Hi Islander

      if you look at the fases information, the 15h03 is given at 10 by default (depth 10f) so in fact they did not achieve depth calculation. Its rms is 0.3 making it a “bad quality” quake. The other one is given at 9.6 km with a rms of 0,23 so “passable”.
      So for the 15h03 let’s say it’s “indicative”

  24. Meanwhile, up at CTAB. To me, it looks like its sputtering.

    Not a geologist, not a seismologist, hell I can’t even play trombone anymore. But I did, and that’s where I came up with my idea of what it’s doing.

    • “bloody deep quake!”

      Yep.. and likely on the subducting slab. Some equate these to a phase transition to of olivine to a spinel configuration. I’m a bit dubious though, that’s an awful lot of energy for a crystal transformation… unless the new configuration forces a re-alignment of the stress field as one version could be weaker than another.

  25. Just wanted to dat Hi to you all. I was a regular reader (didn’t post much though) here during Bob’s appearance and just like many of you I spent hours looking at the webcams, looking for activity and at the restingolitas. Loved that. After the birth of my twins I did not have much time to read here anymore, but how convenient of el Hierro to now get active again during my Christmas Vacation, so I have plenty of time to read here again. Its like I haven’t been away 🙂

    (I’m guessing Frances is Newby? Or am I wrong about that?)

  26. Is this showing something other than background noise?

    Sorry cant find out how to post a picture!! Yes, but there be dragons…

    • “Terremotos de los últimos 10 días en las Islas Canarias de magnitud igual o superior a 1.5 o sentidos:
      La información de terremotos de magnitud inferior se puede obtener en Catálogo y boletines sísmicos.”

      They say it.

      Also it is not the first time I have noticed that the numbers are not in a “logical” sequence.

      I think it takes some time to review the quakes and do some calculations, hence the sequence

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