Eruption warning for El Hierro

The earthquake that started either the pre-eruptive run up, or a new eruption.

On the seventeenth of June a new phase of increased earthquakes was observed by commentators on this blog. The level of seismicity was both larger and more numerous than during the previous 3 months. The location of these earthquakes corresponded with the place where the first earthquakes happened during the run up to the previous eruption.

As I have said before, when new magma comes up from the deep via the mantle plume we would see earthquakes at this spot. On the twenty-second of June low frequency harmonic tremor started at two distinct frequencies (0,29 and 0,59Hz) that previously has proved to be related with renewed activity. The frequencies are believed to be a sign of new magma arriving from the deep.

At 21.23 hours on the twenty-fourth of June (yesterday evening) an earthquake of magnitude 3.1 occurred, and within minutes the harmonic tremor had increased in sufficient numbers to herald movement of magma up the magmatic conduit system. After that there has been 49 earthquakes ranging from 2M to 3.8M, which is a rather good sized earthquake swarm for an already active volcanic system.

It has been noted that the earthquakes are not at the exact spot where they were during the previous eruptive phase. The answer is rather simple, the previous earthquake loci have by now gone above the solidus point and is not any longer brittle enough; therefore the renewed pressure breaks the adjacent rock. In other words, the magma chamber has matured and evolved.

As the pressure started to build up from the recently arrived new magmatic material from deep it started to move towards the old conduit. This conduit is by now fairly blocked by solidified magma at the opening.

A renewed eruption will start somewhere along the old conduit leading south from the Tanganasoga volcanic system towards the old eruptive vents that build up the edifices of Bob south of La Restinga. The question is if the new eruption will take place at the original pillow lava and pumice cone of Bob, or up at the new vent slightly closer to La Restinga. Another option is that the old vents by now are to plugged for the lava to be able to escape that way. Then the most likely place is somewhere along the route of the old conduit. And that means closer to the town of La Restinga, or even on land close to or inside the town.

Currently I would say that there is a high risk of an eruption starting, or that it already has started. Visible signs of the eruptions should be coming within the next 3 days judged on previous behavior. The eruption will most likely not be larger than the previous one due to the pressure being lower, but if it happens closer to shore, or even on land, the effects might be more dramatic for the residents.

My judgment would have been to immediately evacuate La Restinga until the eruptive locus has been confirmed.

IGN and Pevolca has declined to comment on this.


Regarding why I wrote that unusual and stark warning directed to the residents of La Restinga. I want to clarify why.

1. From the current signs and previous behaviour of the Tanganasoga volcanic system I judge that there is a 2/3 risk for a new eruption soon.
2. I am fairly certain that Bob and the newer vent on the ridge above Bob towards La Restinga is congested by solidified lava and not viable any longer as eruptive vent.
3. During the end of the previous eruptive phase there was anomalous gas ventings closer to La Restinga, and 2 earthquakes located close to the port of La Restinga (one was inside the actual port).
4. We know that the conduit leads from Bob towards a magma chamber under Tanganasoga. The usual behavious for volcanoes of this type is propagating vents erupting ever closer to the central part of the volcano.
5. From all of this I judge it to be about a 50 percent risk that the new eruption would be sufficiently much closer to La Restinga to cause risk for the inhabitants, or even on land close to or inside La Restinga. One should remember that there is a scoria cone 100 meters outside of La Restinga.
6. The current harmonic tremor episode is of the broadband type that is normally associated with sudden heavy degassing caused by the earthquakes. This can in a few eruptions increase the likelyhood of a non benign type of eruption. Ie, that the next eruptive phase may be having a more vigorous start than the previous due to a lot of gas pressure building up.
7. IGN and Pevolca is not the most warningsome agencies on the planet, to put it mildly.

All of this put together gave me a bit of a judgement call crisis. Based on my consciense, my experience, and so forth I decided that someone should issue the warning that IGN and Pevolca most likely will not give. So, I gave a warning that I myself would adhere to. I personally would not be inside of La Restinga right now. I would rather have someone say I am an idiot and should shut up, or even in the end try to sue me, than feeling that I through being quiet was part in people dying.

I would though like to say that those who so far have questioned me (privately) have been quite correct in doing so, specifically since I was in a hurry when writing and therefore a bit vague.

Pevolca has notified that there will be a statement after their meating this afternoon, and also commented that the afternoon today was the fastest possible oportunity for the meeting regarding the current new activity.

Update 2

People have noticed down in the comments that the harmonic tremor is higher in frequency this time and look different. That is because it does.

Click on the image for a bigger view. Do not be alarmed by the text, what is stated there is about volcanoes that have had a long repose period.

The earthquakes have knocked off a lot of gas from the lava, and this causes something called a Broadband signal. These are normaly associated with more vigorous eruptions. The text in the image states the limit here as being a VEI-3 eruption following a broadband signal. But that is for a volcano that has been dormant for a while. At Tanganasoga the plumbing system is still in large parts open, so the pressure can not build up sufficiently to produce a VEI-3 eruption, and that most likely gives the broadband signal for a smaller possible event.


446 thoughts on “Eruption warning for El Hierro

  1. Latest statement from Pevolca.

    ,,New note information officer of the PEVOLCA on the page of the Government of the Canary Islands (Henry)IGN CONFIRMS THAT THE SEISMICITY STARTED SUNDAY CONTINUES ALTHOUGH IT HAS DECREASED THE NUMBER OF MOVEMENTS26-06-2012… 15: 46 – Ministry of economy, finance and securityThe activity has moved into the area between the dorsal West and the slope of El Julan.The Instituto Geográfico Nacional (IGN) has confirmed, at the direction of the Plan of Civil protection by volcanic risk (PEVOLCA), that the seismicity that started on June 24 in the sea of the Gulf continues; While it has fallen from 12 noon on the day of yesterday. They also indicate that activity has shifted, mainly, to an area that includes the dorsal West and the slope of El Julan.In this regard it should be recalled that he remains the normal phase in situation and green light of information to the public, which does not require the adoption of any measure of civil protection.More than 300 earthquakes, most of magnitude greater than 2, and with a recorded maximum magnitude 3.8 and a maximum felt intensity of IV (EMS) were located until this afternoon. The depth of the earthquakes located in this series is maintained around the 20 km (between 17 and 21 km), not watching migration to the surface.To perform a correct interpretation of the process that gives rise to this seismicity has to continue with the surveillance and analysis in real time of the data, obtained by the volcanic monitoring system of the operating IGN in El Hierro.From the Director Plan Committee recalled that official information was which is emitted from the PEVOLCA releases containing the conclusions of the scientists who are directly working on the study and assessment of the data & page = note. htm & id = 149614,,


    • Something has just happened in El Pinar

      El Pinar , sentido a las 17:15 y otro más fuerte a las 17 :16 como una sacudida

      El Pinar, meaning to 17: 15 and another stronger at 17: 16 as a shock (Translated by Bing)

      4 minutes ago · Like · 1.

      Javier Gonzalez Herrera ‎17:15 los Mocanes
      3 minutes ago via mobile · Like.

      Paco Storm Se ve muy largo en el espectrograma ese de las 17:15
      It is very long in this spectrogram from 17: 15 (Translated by Bing) Avcan

    • Pevolca at it’s finest…
      After two days of the highest accumulated seismic release, they say that things are not really happening, and that there is not need for any measurements to be taken, but they are watching it closely as hell.
      Wonderfull, moroons.

      • And with highest I actually do say that it is the highest recorded values since onset of earthquakes in july 2011.
        Double moroons.

  2. Jose Luis Barrera has made a statement .

    José Luis Barrera, Vice President of the Association of geologists “Still is risky making a prognosis”, indicates.Madrid, 26 June 2012.-the Bar Association Officer of Geologists (ICOG) has concerned today about increased simica activity on the island of El Hierro. “More than 350 earthquakes have occurred in recent days, some of them have been felt by the population,” says José Luis Barrera, Vice President of the ICOG and volcanologist.In particular, there were already 24 microterremotos June 24, but yesterday June 25 produced 241 earthquakes, of which 180 exceeded 2.0 on the Richter scale and 6 exceeded the 3.0. “Earthquakes are tectonic in origin – explains barrier – IE breaks the rock and they have a depth average constant, between 18 and 20 km”.”The epicentre of most of the earthquakes is located in the municipality of Frontera, although some have been found at El Pinar, which is the municipality which belongs to La Restinga”, he adds.”It is still risky to make a forecast, but what is clear is that this unusual seismic activity could be signs of an upturn in the volcanism of the island although there have not been so far on the ground deformation or other physical abnormality in the territory,” concludes José Luis Barrera.Bar Association of Geologists ,,

    The full report can be read on :

    • Does this not contradict what Pevolca has said in their statement earlier as they have stated there is a decrease in the movements !!

      • Yes, it does contradict Pevolcas statement.
        Barrera is though the more likely one to be correct.

    • Interesting report.
      Barrera is pretty much saying what we have been saying, but more turned down.
      “can be signs of pre-eruption in the volcano”…
      Also that they have not detected any inflation yet could be either that they do not have a clear reading yet, or that the bolus is still flattening out against the crust and the lift will come in a few days.

        • Involcan and Pevolca fighting?
          That was a new one…
          But it is interesting that they point out the lack of gas measurments.
          I would love to get some from the caves.

          • I find it somehow funny that the pevolca says no changes in gas emissions even if there were no recent ones to compare them to, funny because I am imagining our friend nemesio trying to explain this to our local politicians who in turn are only interested in tourism revenues, I guess the show will go on until Bob decides what to do…

    • I really do like Barrera. He is very respectable and says things clearly. He should speak more often (M.Barrera if you read this blog….)

      As fot the gases it is as I feared, if they stopped doing the monitoring (probably for financial reasons). This is very stupid to say the least.

  3. They are still commenting whats happening near El Pinar at the moment.

    Y parece que tenemos un poco de tremor de nuevo…. coincidiendo con un máximo de sismicidad (3 temblores seguidos)

    And it seems we have a little tremor again…. coinciding with a maximum of seismicity (3 followed by tremors) (Translated by Bing)

    about a minute ago · Like.

    Javier Gonzalez Herrera ‎17:25 muy muy largo los Mocanes
    See Translation avcan

    • Henry from Avcan has just made this comment:

      Hola Paco, mira el sismograma, no es tremor, podria ser un LP, pero su espectrograma no coincide con eso..asi es un tren sísmico o varios sismos encadenados, como cuando se rompe una tabla e indican rotura de roca, primero un crack, luego crujidos hasta llegar al limite de rotura y partirse.. ( Enrique)
      3 minutes ago · Like · 3


      ,,Hi Paco, look the seismogram, isn’t tremor, could be an LP, but its spectrogram does not match that…This is a seismic railway or several chained earthquakes, as when breaks a table and indicate breakage of rock, first a crack, then crackles up to the limit of rupture and break out… (Henry)3 minutes ago · Like ·,, Avcan

      • Whatever it is its still ongoing !!!

        ‎17:36 otro fuerte
        14 seconds ago via mobile · Like.

        Julia Sisi ‎17:36 temblor largo en Los Mocanes
        See Translation

  4. Just posted on Avcan Facebook page.

    Important. Please, to all the correspondents of the island of El Hierro, in case of detecting any strange symptoms, strange smells, changes in the taste of water, noise or rumors, feeling of dizziness or vertigo, behaviors strange animal (for example, insects or rodents), of course, seismic movements especially the side or wobbling and long-lasting, landslides, cracks, fractures of walls, walls, roads, outcrops of gases, changes in the temperature of the water, appearance of fish dead in coasts, etc… that immediately made it known to the authorities of Civil protection in their localities or respective city councils. Any information that the citizens can contribute, by peregrina that may seem to you is very important. Thank you. ,,

  5. Short comment on the earthquakes!

    The earthquakes today has long amplitude component to them normally associated with magmatic movement into the cracks. These LP earthquakes is considered to be magmatic. There has during the last 8 hours been at least 3 of them. The 17.16 is one of them.
    I believe this is onset of movement upwards of magma into the actual system of Tanganasoga.

    First LP

    Second LP

    Third LP

    The third LP seems to have opened a conduit somewhere, most likely from the crustal boundary (MOHO) up to the chamber under Tanganasoga, or directly towards Bob.

  6. Tanganasoga what kind of volcanic structure is it that makes its so important? is it a small stratocone where new eruptions could happen in the (geologic) future or is it simply an oversized monogenetic cinder cone?

    • It is THEE volcano of El Hierro. All activity sprout out from that central volcano. It is the part that has the magma chambers.
      The rest are just sideshow vents from Tanganasoga. It was Tanganasoga that erupted during the winter. Bob was just the name of the vent.

    • I’ve been keeping an eye on them and wondered what was up. The weather appears quite calm. I trust one of our Iclanders will tell us if they think something’s happening.

    • earthquake2012-06-26 16:35:57.9
      52min ago 27.70 N 18.07 W 19 ML 3.5 CANARY ISLANDS, SPAIN REGION 2012-06-26 17:17
      earthquake2012-06-26 16:15:30.2
      1hr 12min ago 27.70 N 18.09 W 20 ML 3.1 CANARY ISLANDS, SPAIN REGION

  7. Sorry, folks, but we are about to witness something nasty at El Hierro if precaution measures are not taken. Better prevent than find a remedy come too late!
    If this graphs are still rescaled, the strength of these tremors is much bigger than it seems…
    I’m amateur and still, I wouldn’t wait for the scent of sulfur or whatever…


  9. Pingback: Canary Islands Rattling For Eruption? : Marygreely1954 – altoego

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