Special report: Rift zone eruption continues at El Hierro volcano

This is going to be a short blog post about what is going on in El Hierro. But I have a longer blog post planned for tomorrow.

The current eruption in El Hierro volcano is a fissure eruption. As such a new eruption vent can be expected for the time while magma continues to be injected into El Hierro volcano from depth (28+ km). When a new fissure starts to open it is pre-seeded by a swarm of earthquakes. Lack of this knowledge, or some type of ignorance about this fact has me worried that a eruption. As there is a real risk of eruption happening close to a populated area in El Hierro. It is also a fact that a new fissure can open up extremely fast and with no warning at all. Since when the magma reaches the surface there is no guarantee that the fissure is going to open up with a swarm of earthquakes. In most cases that I know about, the eruption fissure opens up with no earthquakes at all and with no earthquakes. The only earthquakes that take place is when the magma is breaking a path up to the surface.

Earthquakes during the last 10 days in El Hierro volcano. The new magma injection appears clearly with earthquakes ion this map. Copyright of this picture belongs to Instituto Geográfico Nacional.

All earthquakes in El Hierro volcano since July. The new magma injection appears clearly on this map. Copyright of this picture belongs to Instituto Geográfico Nacional.

At this moment it is unclear if the new magma injection has got into contact with the magma that started to inject under El Hierro volcano in July 2011. If that happens the two magma injections are going to merge. But what happens after that is unknown to me. As I have never seen that type of process happen before.

When the El Hierro island is viewed from above it is clear that there are eruption periods where the El Hierro Island is covered with eruption cones in fissure eruptions. It is close to impossible to know if that this the case now or not. But I fear that it might be the case, as it has been long time since El Hierro erupted last time and the Island grows in fissure eruption jumps that take some time to pass over. One such eruption period jump appears to have started on 10 October, 2011. How long it is going to last depends on how large it is going to be. But this is going to last more then few weeks. But there are going to be breaks in between eruption episodes in El Hierro.

The harmonic tremor in El Hierro just before midnight of 28 October, 2011. The spikes are earthquakes N to NW of El Hierro Island. Copyright of this picture belongs to Instituto Geográfico Nacional.

There has been some drop in harmonic tremors from the first (and only?) eruption vent just outside the coast of El Hierro. This means that it might be closing up. But that is normal for this type of eruption. When this eruption vent closes up or just before it closes up. A new eruption vent is going to open up at new location. As the magma inside El Hierro volcano supports that in my opinion. When and where is the unknown factor in this equation.

As for the question on how long this eruption period could last. I am hoping that it is going to be over when I move to Canary Islands (maybe El Hierro Island) in about 4 to 10 years time (at the latest). But this type of eruption take a long time to finish. So covering this eruption(s) is going to be ongoing for some time now.

268 Replies to “Special report: Rift zone eruption continues at El Hierro volcano”

  1. @Ayson, If you have not already found them, I have provided the plots you requested at the end of Jon’s previous post.

    May do some more for SW Frontera, El Pinar and Atlanticos Canarias to see how they compare based on the data downloaded from IGN so far, if time permits tomorrow.

    But I am heading for bed right now.

    1. Thank you Karen. They are brilliant.

      And thank you for this update, Jon.

      I agree with you, Jon, that this situation may be high risk for the people of El Hierro. I am watching the strengthening of the earthquakes, and linking this to Carl’s definition of rifting quakes drawing from the mantle. I have also not entirely dismissed the notion of El Golfo having been a much larger volcano which may have sheared due to a plethora of lava tubes through the sedimentary layer, causing collapse of a much larger island, before the main eruption millenia ago.

      The 3.0 quakes are now consistently at 22km depth today. What are they stretching/breaking through here? Where is the magma going from here? Is it breaking a circle in the area, around a previous eruption plug? This would tie in with what Lurking observed originally.

      I fear it may break quickly up, if it is pushing at a fixed ‘lid’, just NW and W Frontera, though as Jon points out, it may instead join with the pre-existing magma under El Hierro. The scale of the area affected is, however, potentially huge. Whether this happens sooner or later, or even at all, remains to be seen.

      I guess it depends on whether the concept of lava tube perforations is valid, and whether this caused the El Golfo slip, or even whether a much larger El Golfo volcano disintegrated at that time. I realise I am being alarmist, and I may be completely wrong. I state clearly I am not a volcanologist or geologist. The depth remains constant in N/NW Frontera, but the quakes are strengthening, and, as Karen/Diana noted, forming a circle and now filling it in.

      I apologise, Jon, if you would prefer I did not speculate in this way. Best wishes all.

      Anyone, if you think I am mistaken, please say.

      1. It is too really early to say how El Golfo (or remains of) fits into the picture.

        Whatever the cause, I would not only focus on NW and W Frontera – they are only part of the whole picture.

      2. Ahora a las 15:15 acaba de haber un temblor FUERTITO y lo sentimos aqui en El Mocanal y tranquilos que aqui no pasa nada 28/10/2011 15:31:11 Alias: Anónimo

  2. This little volcano is quite enlightening.

    From a statement/post by Armand Vervaeck a couple of threads ago:

    “Update 25/10 – 15:18 UTC : The image doesn’t look very spectacular but the
    findings are. The base diameter of the new volcano shape (as they call it) is
    700 meters. It has a present height of 100 meter and a crater of 120 meter.
    The base of the crater is measured at a depth of 300 meter.”

    The image is dated 24 Oct, if you cut a baseline across the central part of Bob (in the valley) at 700 meters, the peaks show a height of about 262 meters on the left side (from the POV in the picture) and 275 meters on the right.

    That works out to a slope of 44° on the left and 48° on the right (based on the length of the base to the point under the peak).

    According to one reference that I dug up, basaltic tephra (at Yellowstone, and not underwater) has an angle of repose of about 30° to 35°.

    Doing measurements of the angle of individual sections of the left hand slope, I get values ranging from 36° to 53°.

    The cone like shape on the far left hand side of the image… if it’s an old cone, seems to have similar angles.


    1. Note… the first image (discussed in the quoted text) was describing the top-down sonar based image and not the high res one posted in the last thread… the one I made the measurements off of.

      1. Had troble beliving comments about depth at the spot as “300 m”, but maybe now. I had estimated it started at about approx 596 m (many threads back), but then “North” lines were ´cut out´ from first published image, so placing was too inacurate to put onto makeshift map and try calculate anything m3 wise just for the cone. Now rift walley seems half full with lava and heavier pumice. Only half-a-second or so before 18 West remained visble, North is unknown.

      2. I only have 1 minute resolution bathymetric data from GODAS. That’s about 0.816 km (0.51 mile) point to point.

        30 arc second is available, if you sign up with GEBCO. I’m tired of giving out my email address so they can pack sand.

      3. Correction, 0.816 km (0.51 mile) is 30 arc second.

        Double that for on minute resolution.

      4. Will try again tomorrow. Now watching three critical EQs West of god station. This is about mid way between old eruption site at Fimm and god. Close to cryptodome. Scary feeling.

      5. Lurking, either I am to druck to understand this, but how the hork did you get this data? I will probably understand this with about ten beers less… 🙂
        Not really sober 🙂

      6. Though to be honest, it isn’t the easiest data set to work with. Any time you start making 2000 x 2000 cell matrices of gridded data, you are just asking for the computer or software package to puke on you when you start merging them.

        Thats why I do it a layer at a time and save often.

        By all rights, I should feed it into the MySql server and bite off a chunk at a time, but I’m impatient and want to plot rather than write queries. Since my spreadsheet can safely hold a sizable sheet open, I just do it there.

      7. Segun me han llegado informaciones muy recientes, la Grieta que va desde El Julan hasta el Tanganasoga, presenta niveles termicos muy altos, y los ojos de los cientificos estan puestos en esa zona. La observacion se ha hecho desde el aire con una camara termica. Saludos

      8. Just giggeled Karmela’s reply:

        “According to information I have received very recently, the Rift which runs from the Julan to Tanganasoga, has very high thermal levels, and the eyes of scientists are placed in that area. The observation was done from the air with a thermal camera. regards”

      9. Still drunk as a skunck…

        Pozo de la Salud at the north western of El Holfo
        is a whatever of similar of the Blue Lagun of Iceland with hot springs. Found one dude from the village, poored beer into him (and me), and he told me about the hot springs there at the hotelll. His desctiption was, Pozo de la Salud is center of El Golfo 1 nautical mile out of the coast..
        Many beers hard to decucribe.

    2. I thought that the more recent picture showed that there have more activity in the area so some must have preceded Bob. So there may have been previous smaller eruptions / rifting that did not show any evidence on the surface.

    3. The Ministerio de Ciencia e Innovación (MICINN) posted some new digital images showing the same region in 1998 and 2011. The cone wasn’t there in 1998, so it’s younger than that in any case.
      Images and Video:

  3. Jón, I only hope you are wrong about it, but I’m inclined to think you aren’t.
    It’s quite possible that you see less quakes under the island itself because the fissure is “strangled” by the islands weight.
    Hope no one in Hierro reads this blog post.

    1. This is what I think is the reality of the matter. Sadly this might change many things for the Island of El Hierro. But lets hope for the best.

  4. I added new iPhone feature to this blog. Please let me know if it works. I also added a user activation email code to this blog site. So new registered users have to confirm that they got a email before they can use there a account here.

    I am getting a bit tiered of obvious spam accounts, at least I think that they are nothing else.

    But I need to know if this changes work properly or not.

  5. Ok SO when you read post no comments show. When you hit comments you go comments screen.

    When you turn off mobile switch that brings you to the full site and you can see comments.

    It will work if maybe instead the choice is labeled full site eh rather than mobile on/off?

    1. There are two mobile sites now. One for regular mobiles and the one for iPhone that I just added and I am testing out.

      Reading comments on mobile has been a bit of challenge from start.

  6. Wunderground has a preview comment feature that might help some of the posters review their post to see how it may look or provide that 10 second count to avoid the wrong thought.

    Will add direct email re thoughts . Thanks Jon

  7. Hallo Jon from my new iPhone. I can’t do Icelandic letters though! Maybe I should ask Siri…

  8. Lurking your motto should be… Aude sapere = Dare to be Wise.

    There is Baby Bob! When there is a cluster similar to the North there will be the new fissure.

    Last night was quiet in Iceland. No Party. Maybe the Giants are waiting until mid winter when they can put on a light display!

    1. My “stupid” comment was about the follow up post.

      (It’s also the title to a Weird Al Yankovich parody of Devo)

      1. Since I have been hit with a barrel of Laphroig I will just quote a song of Devo before faintin in the sofa…
        Whip it!
        At all:
        If I seem silly, I have just been hit by my even birthday by evil horible friendss… bad friends…

      1. @ Diana, isn’t the circle-shaped scatter actually Bob? I thought it was south from Restinga.

        And I think the big cluster near the south coast is near Tacoron, the place that Jon and Lurking were pointing out as a possible eruption site from the very beginning.

        I think so at least. Any comments?

  9. Next Post.

    A while back, I hit upon a method of looking a bit more intently at the quakes.

    None of these quakes have focal mechanism solutions, at least none that I can find. The focal mechanism tells you what the fault plane is for the quake in question, and gives you information about the dynamics of how the quake occurred.

    What I have come up with is a way to at least get a sense of what the fault plane may be, more accurately, the trend of the possible fault plane. It’s not likely going to be very accurate, but there is a way to gage just how far out in left field we are with this method.

    First, the idea. (yeah, a bit of a repeat but this is only the second time I’ve made this plot so I really ought to explain it again.)

    Earthquakes have errors in their location. The size of the error depends on the gap in station coverage and the spatial orientation of the quake with regard to the stations in the seismic network. The quake is located in the three spatial dimensions… x, y, z.

    Error ellipses are the boundary of the positional “best guess” location of the quake. (it’s actually a pretty good stab at it). In order for researchers to have an idea of how accurate that position is, they consult the error ellipse.

    This is where I leave the tracks.

    The long axis of the error ellipse represents the direction (azimuth) of least accuracy. It is my contention that this is going to lie along the fault axis, or the plane of the fracture. Logically, the energy dissipation would be hardest to localize since the boundaries of the faulting area are going to be lease defined along that direction.

    There will be a less clear delineation of what is or is not the failure area.

    In order for this oddball view of the quake to be even half way valid, there has to be minimal quake to network positioning bias. This is where we try to do an validity check.

    Here are the quakes at El Hierro, quake error ellipse azimuth to coverage gap.


    As you can see, it’s pretty even. Nothing major that sticks out that states that we not only left the track, but fell off the bridge.

    So, lets take those quakes from earlier, and look at them while applying a couple of filterers to the data set.

    All quakes to date, with only those having an azimuth oriented from 000° to 150°. (0 to 180 scale, we are just looking for an orientation plane)


    Notice that the brunt of the new really deep quakes are not there. Only the main batch from very early in the year, and the cluster trending south prior to eruption show up.

    Now, lets look at the quakes with a 150° to 180° orientation.


    Well, there’s the new deep cluster. You can still see the overlying cluster since it had a pretty much even spread across the dominant azimuths. What is missing is where that southbound set seemed to hit a wall and bunch up before the eruption started.

    Now.. what does it mean? I don’t know. To me, it seems as if there is something intrinsically different about the deep set. It might be a different orientation of the strata or the mechanism of driving quake production.

    I did not make this set into an animated plot since I’m pretty far out in “unaccepted and unfounded theory” territory, and not every one looking at Youtube is gonna have half a clue about what I’m saying here.

    If you don’t understand it, don’t sweat it. I only have half an idea myself.

    Enjoy wrapping your noggins around this one.

      1. The problem is that unless a quake is of sufficient size and enough stations get good read on the waveforms in the various quadrants, no solution can be made.

        This is the reason that the small events do not have solutions. It is my belief that there is usable data there in those small events… at least from the idea of determining that something sets the different groups apart other than location.

        This last set of plots wasn’t intended for general consumption, that’s why I caveatted it so heavily as not having a sound scientific basis and being nothing but a stab into no-man’s land.

        The moment tensors are good, if the quake is large enough to be read and analyzed properly. We the public are usually getting pretty frantic when they reach that magnitude and have little use for a focal mechanism.

    1. Hi Lurking – so, to get this right in my head – are you suggesting that the magma where the new EQs are showing, is following perhaps a tough strata between the two sets – that their relationship may be limited ? Given the orientation of the EQs – might magma from these deep quakes find their way to the surface away from the island then – a new ‘Bob’ ?

      1. Lurking that’s just what I need to back up the crust+upper mantle ‘bending’ mechanism: a difference between the deep EQS and the earlier swarm of 8000. Here goes
        I hve previuosly postulated that the EQ pattern better supports a flexure/fracture process rather than a magma push from below. Thus the EQs started shallow (8-12km ) and trended deeper (25-30now). The shallow ‘zone of 8000’ is now quiet, yet below its northern tip deep EQs have started in past several days- that does not look like a magma push from below. We need also to explain also the 5km thick quiet zone above the resent locus and the bottom of the swarm of 8000.
        I propose that the cause is an upward flexure of the crust+upper mantle in a response to mass-reduction resulting from the Golfo/Julan/Playas landslides. During its formation the erupted mass of Hierro will have deformed the crust+upper mantle below into a shallow saucer shape over 1 million years or so, ending around 350k ago. The giant landslides have removed much of that mass, two-thirds of Hierro’s subearual eruptive volume has slid away. The biggest landslide El Golfo was the most recent 135ky ago. So I propose we are seeing a rebound event in response to this mass reduction. So the N-S line of the swarm of 8000 reflects the arc of an upward motion of the saucer’s centre ( the Frontera-Valverde side) compared with the periphery ( Sabinosa). I envisage the saucer depression as being in total about 35-40km thick, embracing all the oceanic crust (8km to MOHO at 14km) and upper mantle.
        A small reduction in the curvature of the saucer would put the upper layers under tension – and induce the swarm of 8000- and the lower layers under compression, whcih is where the EQs are now in the upper mantle. Could that difference between tension and compression explain Lurking’s latest data anlalysis? The quiet zone just above the present EQs at 22-27km would be of course the region in the flexure where there is neither tension nor compression – so no EQs.
        Time for a Plasticine model?

      2. Is this a similar effect as in Iceland when after the last Ice Age, glaciers were melting and there was an uplift of the land mass as a consequence? And I think it is occurring now again in Iceland and at a rather fast paste, if I remember that correctly. Whereas here in El Hierro, the process of uplifting took a longer time. And in Iceland the center of the upward bent would perhaps be under Vatnajökull. And could this also explain – I am just playing with ideas being no geologist – the existence of the Hot spot under these two locations because this uplifint process would permit hot mantle material to rise at these places?

      3. Broadly the same, yes.
        The best summary I’ve found is on Tenerife and how its mass has depressed the crust into a bowl or saucer shape:
        Landslide data in table1 here:
        –ther was big El Golfo landslide, 150 cubic km , only 15000 years ago. So that time scale is broadly comaprable with Icelands and Scandinavia rebounding after the ice-age.

    1. Bob is actually closer to the coast. That’s just where the quakes landed.

      Now if you really want to think about weird

      At the very outset of the El Hierro swarm, with about a weeks worth of data, the quakes all formed an almost perfect circle just north of the dominant cone in the El Golfo scarp. A region a few hundred meters across where there were virtually no quakes… yet quakes all around it.

      Now that was odd. My guess was that it was an old chunk of hard, tough magma. The quakes have since filled in that void in the plot.

      1. Unfortunately, I have really difficulties to understand the backgrounds of the plots, because I’m not a scientist, very bad at math and it’s very hard for me to understand all the explanations in english (Giggle is less than helpful). But I like to see graphics, which I understand, to be a clear way of “knowing” what happened. Therefore, many thanks to you!

        All guesses so indicate on the El Golfo region of the outbreak as possible?

      2. The only real knowledge that you need is how to read lat and lon. The rest of it is speculation.

        Based on a couple of papers I’ve read, El Hierro is a volcano sitting on top of Jurassic age sediment. Basically, magma poked a hole in it and built a volcano on top of it. The interaction of that sediment, and the underlying stiff but still pliable crust, are what drives how the island grows/rifts and/or suffers flank collapse.

        This sediment layer can be up to 5 to 8km thick. This is based on the oddity of there being a “dead zone” where there are very few quakes. How that magma got to the surface with nothing more that the roar of the harmonic tremor, and virtually no quakes, it what a lot of our discussion in this forum was about.

        It’s still an unresolved issue. No one can say with certainty what it is.

      3. Thanks for your explanation. So i think i understood your plots better and we will see in far or near future what will happen.

      4. This cartoon shows that small pockets of magma are connected by a mesh of sills and dykes lies under Hierro.
        (fig 11c on page10 of pdf)

        My guess is one of these pockets found itself near the surface after the Julan landslide and has found a route to the surface as a result of crust flexure ( see my post above). It might be being fed by the connections to its neighbour(s), creating the tremor.
        The important thing to note is there is no big magma chamber and no big conduit -so an eruption will be a bit like Fimmvorduhals or Hiemaey in character, quite localised.

      5. I regard the sedimentary rock as cushioning the erupted mass of Hierro from strain induced by rebound flexure of the crust+ upper mantle below it. The sedimentary layer includes shales and clays. These are not going to allow EQs but which also slide layer-upon-layer easily so accomodating strain imposed from below. That sedimentary layer protects Hierro’s mass above from sudden events.
        I do not believe the EQ pattern points to a magma push from below. I think the almost total absence this week of EQs in the zone that was active from July (8-12km deep, 8000 of them) indicates the strain has been accomodated in that zone and that Hierro’s erupted mass has been protected by its Jurassic sediments.
        No volcano in Iceland has such a sedimentary layer so our experinces there are no help in trying to guess what Hierro does next.

      6. Lurking You can still see a perfect circle on the plane view. It looks quite small though more like a fissure cone that is filled in.

        Bob is the intense cluster of quakes near the shore. There is a sea mount to the south west of Bob with a tail like ridge running away from that to the SW
        To the North where there is a sudden deep drop to a plain like sea bed there are no sea mounts… nothing that remotely looks like fissure craters. Maybe they were filled in by the slip or….that plain is where the main crater was… and it was big.

  10. Morning Renato , many spaniards is reading this blog, a few are from El Hierro . But it is a reality (the volcano) we can’t change, better to know all possibilities then can happen , don’t you? I prefer it. I go jogging a little to kill my distress 🙂

      1. Maria: buenos dias! I have already placed a reply to the recent comments at AVCAN’s. I feared that Jón’s straightforwardness would cause people to get more concerned. The idea was to make it sound less alarmist, but since it was too late when I posted, I should have had better watched my words.
        Still, I would very cautious about the “fissure” line, especially over populated areas along the fissure’s path, but just because it is an island and there aren’t many options to get away of an eventual eruption.

      2. I still think that there are possibilities to get people out in case of real problems and I am optimistic that they have been thought of.

        So I would just have some bags packed and for the rest try not to be overconcerned.

      3. I have just seen your answer in avcan, I know that you are cautious in yours analyses, I read you some time ago. And I agree with you, here are not many options on a small island and a very special orography.

    1. I’m sorry, I think this is actually right, there is a spike on all stations. Only place I can’t seem to find it, is at Jon’s helicorder… But could it be that the wind is too noisy?

    2. I think it is a little lower than 3.6 at least I think it will be when the IMO staff check it. It looks like a swarm though I think.

  11. @Renato, I hope many people on El Hierro read this post. Better one warning too much than no warning at all! And it does not seem likely that the authorithies will warn about anything yet. Very sad, if you know that things might turn to the worse very quickly. Better be prepeared. If you wait with giving warnings until an eruption close to shore or on land actually has started, the warning is too late.
    @Islander, same to you. I have been thinking about your reply on October 29, 2011 at 00:08 most of the night. You give people a lot of good information about what to do, based on your own experience. This information should be available for all inhabitants of El Hierro!
    @ Jón, same to you. So glad you dare to speak out your fear what might happen and made a special post about the rift zone eruption. So good you feel responsibility towards the locals.

    1. The following is recommended for yellow alert as per the Direccion General de Seguridad (and giggle translate, which did a very good job of it!).


      Once declared the yellow phase means that we must prepare for an unfavourable evolution of the phenomenon, and most importantly, be attentive to official messages of prevention and self-protection that will be specific to the areas of risk. The General measures taken in the areas of higher risk are the following:

      Listening to the radio or see on television the official reports of volcanic activity and its evolution. It is convenient to have a battery radio.

      Having always at home sufficient drinking water, first aid kit, usual medication in case you need, radio, batteries and flashlights. Make sure you have enough medication for the family members who use it regularly.

      Use the 1-1-2 only in case of emergency.

      For any additional clarification call to the 012

      The Internet of the Government of the Canary Islands and, in this case, the Cabildo of iron pages will also be available.

      Make sure you have the personal documentation of the whole family and housing organized and grouped to be able to transport the most important thing at home.

      It should be a suitcase small with a few changes of clothes, comfortable shoes, brush teeth and other articles of personal hygiene, small blanket, towel and mobile with your bootloader

      Cargador = Charger. Whats a bootloader??

      1. This is good, Jenny, I think it may mean to fill the boot of the car, pack up important papers, and be ready to move.

    2. I dont have concerns about a sudden eruption:
      The present EQs are deep – 25km – well below the crust/mantle boundary at 14km.
      The zone at 8-18km depth that had 8000 Eqs beginning in July is silent – that does not seem to me the pattern you would expect if fresh magma had intruded.
      There are no signs that EQs are appearing in any numbers above the sedimentary layers . These layers would offer little resistance to fresh magma and we should surely by now – 3 months after the shallow July EQs – have seen new EQ acticvity above the layer at about 3-5km depth?
      Icelandic volcanos lack that Jurassic sedimentry layer so are not a good model.

      And I dont subscribe to the suggestion that the activity resulted from a push of fesh magma from below.

  12. I can’t remember but… Is it quakes of about 5 that we will start seeing just before an eruption at katla?

    Or I heard somewhere that will start feeling quakes at Vik?

    1. Yes, last time before the big eruption of Katla in 1918, there were very strong earthquakes (see: W. Schutzbach, Katla). And the geologists think there could be some of these again, 1 day to some hours before a big eruption would occur (http://www.mbl.is/mm/gagnasafn/grein.html?grein_id=493134 – as says f.ex. the geologist Ari Trausti Gudmundsson). And yes, of course they would be felt in Vík í Mýrdal which is the village nearest to the volcano.

  13. Sissel: the poor people at Hierro are terribly worried. No wonder. I wished we could have a concrete answer to give them some reassurance.
    I don’t understand why the authorities keep looking at this situation as if nothing is happening. We’ve been chatting night and day about the events at Hierro, many different positions, but one thing is for sure: no one here is saying that nothing will happen. Neither at EB.

    1. Yes, unfortunately it is true what you say, Renato. It seems that the Canarian Government’s policy it´s not to inform people couse they believe that this information creats “alarm”, and they get just the opposite. That question, apart from terrible, it’s pathetic. I often visit your page, although I know you repeat constantly that you are not professionals in volcanology, however it seems you know more than those who handle our seismographs. Thank you all for giving us a little more light on these issues. Knowledge always gives peace of mind.

      1. Not necessarily more knowledge, only that we here are in a more comfortable position to speculate.
        But, indeed, speculations can also lead to misunderstandings and cause unnecessary alarm.
        That’s why people over here try to get as close as possible to concrete, available, facts.
        However, we are not so sure that all facts are unveiled.
        Things can change quickly, for the best or worse. Let us give credit to authorities and wait until they take the necessary precautions.
        I only wished that, if they are so sure that the situation is under control, why don’t they disclose the data that will prove there’s no reason for concern whatsoever?
        Muchas gracias, y espero que todo vuelva pronto a la normalidad .
        Al pueblo de El Hierro, toda mi admiración por su paciencia y bravura .

      2. If I were on Hierro I would certainly take the precautions the authorities suggest. But I would not be worried about small EQs nearly 20 miles deep. I would be reassured that the EQs have gone deeper with time. This is the opposite to EQ patterns that precede eruption of magma risng from the mantle. At Eyjaf thay started at about 20km and slowly trended upwards over two to three months. I watch the IGN EQ map for signs of a pattern of EQs appearing above the sedimentary rock layer, at about 5km depth.

      3. Peter you might be right.

        But these EQs could be the first EQs of a new cycle / episode. Note that they are bigger than those preceding the cycle that started from July 2011.

      4. Karen,
        Maybe, maybe not…
        The gradient in magnitude form shallow to deep was thrown up in Lurking’s earlier plot:
        -by now there will be more yellow/red spots (mag 3) in the lower clump at 25km, adding emphasis to the gradient. The diagonal EQ-quiet gap between the upper swarm and present focus is still there today. And the two swarms are parallel with similar dip. That also suggests to me a common mechanism – uplift rather than magma push. But its pure guesswork.

      5. Hi Peter

        Lady Eyaf was a very beautiful and photogenic eruption which Jon predicted very accurately.

        Mt Merapi taught me more about the scale of risks and dangers a known volcano can pose.

        El Hierro has an unusual history, and unfamiliar variables. If I lived there I would have packed up my valuables and my pets, and left with my family, for another island, or for the eastern end of the island, for until it calms down, or is over. This would be not because of known risks but because of unknown risks.

        I hope you may be right, in your interpretation of the readings. The quiet zone above 8km is where the unknown variables cannot be measured. If the quakes reach 9km then I would be more worried.

      6. Or maybe 14km, if that is, as you say, the point where the crust-mantle joins. There are a few at 16km, mag 2.0 and over, since yesterday. This is still extremely deep however.

      7. Hi Alyson
        I watch the IGN map for patterns of EQs shallower than the sedimetary layer – above about 5km.
        The reason is that fresh magma has to cross that depth to the surface from pockets that are much deeper, about 10-35km:
        – see fig 11c of this paper:
        So there is no huge magma chamber anywhere near the surface, no conduit, nothing like those structures in Eyjaf or Merapi.
        That paper allows an estimate of the time the magma takes to get from10km deep to the surface was “…. days to a few months.” (p11 of pdf). So its an eruption happens its not going to be a big explosive eruption ( no Ejyaf/Merapi) it will be more like Heimaey’s fissure:
        Nowadays Heimaey would be anticipated earlier – they had no seismic network then.
        And providing the EQs under Hierro that signal magma rising above 5km
        can be resolved ( bigger than mag 1.5) than ther should be plenty of warning and plenty of time to get to Valverde end of the island. So no huge localised pressure from a shallow magma chamber filling up, so hopefully no big shallow EQs. But the elephant in the room is an EQ that triggers a landslide, and that to me is the biggest uncertainty. That is what I would fear not a fissure eruption.

      8. Eyjafjallajökull eruption was’nt very beautiful when you where in the middle of the ash cloud at 50 km distance and ash entering by all the windows and doors even at 200 km distance from the source. We could hear the strange (explosion) noices even at Borgarnes at about this distance away from it.

        Explosive eruptions are only beautiful on photos, I’d say. My experience.

    2. When I read the information above (jenny, 10:53) I do not see this as a warning at all, just some practical advise (which is also important, of course) what to do before something happens. But a real warning would be more about telling WHAT might happen so people would be prepeared. Remember the Icelandic video related to an eventual eruption of Katla some time ago?
      I’m sure it was on TV in Iceland so everyone could see it.
      I do of course NOT mean that these pictures are representative for what might happen on El Hierro. But it shows how people are being informed and warned about a threatening situation in a another country. It is about communication and about responsibility; about feeling responsible towards people and taking action.

      A good warning on El Hierro would also be informing about the evacuation procedure, which signal will be given (I hope they give one, not only tell people to keep an eye upon http://www.something.somewhere by themselves), where to show up with the suitcase; how to behave for disabled persons, and what about domestic animals for instance? The best protection of all would of course be to start evacuation before someting happens.

      I can understand if a politican is afraid of making a fool of himself by overestimating danger. But I think it would be 1000 times better to do that, than underestimating danger and people getting hurt. Accidents happening because of a lack of caution are difficult to forgive and forget.

      I have been thinking a lot about what we possibly could to to help, from where we are. Writing on this blog and showing our symphatie is a good thing as it will be read by people there.

      The best idea that struck my mind, which is probably not at all the best thinkable idea, is: We could write a letter / email to the authorities (preferable in Spanish) and ask them to do more for the inhabitants of El Hierro. It should if possible be published in the media. A personal letter, each by him / herself, or all together. There are some very good writers on this blog and also very good translators. It must be possible to find appropriate (email) addresses.

      What do you think?

      1. I posted more at 18.36. Hopefully everyone concerned did what was expected of them and didn’t just pass it to the next organisation/association/committee etc.

      2. Thank you Jenny, this gives more confidence.
        They have now clearly stated some very important responsibilities toward the inhabitants, including informing about shelter and evacuation systems:

        “At this stage the Cabildo of iron will be responsible to inform citizens of the practical aspects of the plan of action according to the evolution of the phenomenon of the points of encounter, shelters and evacuation systems.
        The website is http://www.emergenciaselhierro.org.”

  14. Has the Hekla cam been down of late, my memory fails me? If so, it’s up and running but not much to see unless you’re interested in horizontal water droplets.

  15. Peter:
    Let me think out loud:
    Given the fact that El Golfo is highly affected by thicker layers of sediments from successive ancient landslides, I don’t know how much we can import from the behaviour of seismicity at La Restinga.
    But I really hope you are right. And probably, you must be, because I am no expert. 🙂

    1. Hi Renato,
      I’m no expert either. I’m just trying to fit as much of the data as we have to a mechanism that is consistent with what literature I can find on Canary volcanism.
      I’m not particularly interested in Restinga, its not that large. The plume covers an impressive area but may consist largely of clouds of calcium sulphate or carbonate precipitated by heating of sea water by the fumarole. (Ramon Marglef will know for sure by now whats in the plume). The IGN used GPS data a while back to estimate inflation at 50 million cubic metres, and little of that has come out of Bob.
      But I can understand why Hierro is fascinated by its first eruption in living memory.

  16. Why on earth would they not allow a local resident to attend the meeting.?

    Joke Volta reports from Tigaday (Frontera) – (she sits with her laptop in a restaurant with wifi connection) – that the green stain has encircled the coast of Tigaday (Frontera). The stain could be better viewed when exiting the Los Roquillos tunnel (yes, the tunnel who was closed far a while because of the rockfall danger). Together with Joke in the restaurant : 2 observers with laptop/binoculars – one from press agency EFE. So, Joke our local earthquake-report.com volunteer reporter, is amid the trained professionals . Thanks Joke on behalf of our readers. (ER: Joke was refused admission yesterday in a press meeting at Valverde – As a resident of El Hierro she really felt pushed away from the news. We can understand her…)

    1. Why doesn’t she simply get herself a press card from the organisation she is working for? Press conferences are intended for journalists, that’s normal.

      On the other hand, would perhaps also be time to held another conference open to the inhabitants.

  17. This new iPhone theme is really nice!
    We can even zoom! (a lot of mobile site don’t allow you to do this). This is great when you are looking at pictures.

    Concerning the comments, the only thing missing is to see them in a hierarchical way (like we do on the full site) and not in a flatten list where it’s hard to see what comment is another comment answering.
    I guess there is good technical reason why we don’t get this right now, but hopefully some theme update can get us that eventually.

    Nevertheless, thanks for the iPhone update 🙂

  18. Reply from Earthquake Report re the other site reporting the depth was 8km.

    Armand Vervaeck says:
    October 29, 2011 at 4:43 pm
    We trust on IGN instruments because they have a lot of material installed on El Hierro. please trust IGN on the El Hierro data.

  19. 2011-10-29 16:33:21.944min ago 27.77 N 18.04 W 21 ML 2.8 CANARY ISLANDS, SPAIN REGION

  20. http://www.humanityroad.org/_blog/Event_Diary/post/Hierro/
    provides a link to a History Channel programme about La Palma, which has a little bit about rifting re El Hierro.

    The only press release I can come across was the one on 29 September, which is reprinted in a few places:

    ‘Speaking to the El Pais newspaper, volcanologist, Juan Carlos Carracedo admitted an eruption on El Hierro would not be a major surprise.

    “It is the youngest of the Canary Islands,” he explained. “There is a ball of magma which is rising to the surface and it is stationed at the limit of the earth’s crust. At the moment we do not know if that ball of magna will break the crust and cause an eruption.”

    Rather than having one large crater, the volcano on el Hierro consists of around 250 small craters.

    “Any eruption would form cones on the high zones of the island and lava flows which would flow to the sea, although they would do so at a speed that would be slow enough for the population to be evacuated. It is something that could happen in days, weeks or months,” said Carracedo.

    El Hierro currently has a population of around 10,000 and regional government officials have begun informing them of evacuation protocols in case the worst should happen.’

    Perhaps residents are aware of evacuation protocols.

    1. This is from the 23rd September when the alert was raised to yellow

      The Government of the Canary Islands amounts to yellow light volcanic earthquake situation of El Hierro

      23-09-2011… 14: 07 – Presidency of the Government

      This phase involves more population and resource planning

      The Canary Island Government has established the yellow lights for the population of El Hierro to the variations of the earthquake and volcanic phenomenon is happening on the island since last July.

      This decision, on the basis of the specific Plan of Civil protection and emergency care by volcanic risk (PEVOLCA), has been based on the conclusions of the meeting of the Scientific Committee of the Plan, met this morning in El Hierro, who has reported on the changes in the seismic energy released as well as deformations.

      This phase of preemergencia by volcanic risk involves more information to the population and
      certain measures of self-protection in the still unlikely case that an eruption occurs.

      Also, the competent institutions in the field of security and Civil protection, and within the framework of the Technical Committee then held have defined this morning, the action plan which provides for effective procedures to ensure the integrity and well-being of the population which might be affected by a situation of emergency in the area of this Plan. The preparation of this document is an action that sets the PEVOLCA when the situation is in light yellow and assigns staff involved in the emergence of the groups of action, the review of contingency plans of essential basic services, the information continuing to population, the spread of the evacuation Plan and verification of the Communications Plan.

      At this stage the Cabildo of iron will be responsible to inform citizens of the practical aspects of the plan of action according to the evolution of the phenomenon of the points of encounter, shelters and evacuation systems. The website is http://www.emergenciaselhierro.org.

      The Government of the Canary Islands will weekly report on the evolution of the phenomenon, being the only spokesman for moving scientific information. It also enables a specific web page, which will be available at http://www.gobiernodecanarias.org/dgse/sismo_hierro.html

      The PEVOLCA includes different bodies, various institutions such as the Instituto Geográfico Nacional, Consejo Superior de Investigaciones Científicas (CSIC), the State Meteorological Agency; the delegation of the Government, the Cabildo of iron, the Cabildo of Tenerife and the Instituto Volcanológico de Canarias, in this case, also speakers of Civil defence forces and security bodies, and the mayors of the municipalities of El Hierro

      The data provided by the IGN seismic monitoring station can be consulted on the website http://www.ign.es.

      Recommendations to the population referred to in the PEVOLCA


      Once declared the yellow phase means that we must prepare for an unfavourable evolution of the phenomenon, and most importantly, be attentive to official messages of prevention and self-protection that will be specific to the areas of risk. The General measures taken in the areas of higher risk are the following:

      * Listening to the radio or see on television the official reports of volcanic activity and its evolution. It is convenient to have a battery radio.

      * For any additional clarification call to the 012

      * Also available pages Internet of the Government of the Canary Islands and, in this case, the Cabildo of iron.

      * Make sure you have the personal documentation of the whole family and housing organized and grouped to be able to transport the most important thing at home.

  21. GPS data from Nagoya for Frontera:

    So there has been no significant change in Frontera’s GPS location since these deep mag 2 to 3.5 EQs started. Which is another reason why I do not worry too much about them….but I can understand the alarm they create on the surface 25km above.

    1. The Professor’s last published readings for FRON at the time of writing this were yesterday (2011 10 28):

      2011.8232 0.0118 0.0315 -0.0063 2011 10 28 301 1
      2011.8232 0.0111 0.0298 -0.0119 2011 10 28 301 2

    2. Peter:
      “I’m no expert either. I’m just trying to fit as much of the data as we have to a mechanism that is consistent with what literature I can find on Canary volcanism.”
      This is far more expertise than I can claim to me, which qualifies yous with the rank “expert” status. See? I have not been doing my homework, just lurking here and there, and thinking loud, as I said before.
      I would really hope for some beautiful, harmless fireworks from this one. 🙂
      Thanks for the feedback.
      (Yet a bit concerned about the 8 km depth of the 3.6 M)

  22. @Lurking.

    You plots above are very interesting. The one showing the view looking East, especially so because they give a very strong impression of at least 2 arcs. The arcs may be fracturing occuring round the top of a magma dome(s). El Hierro is supposed to be an accretion of three old volcanoes so we perhaps we are seeing the top of two of the magma reservoirs; one reservoir having its top somewhere between 27.7 and 27.8 and the other somewhere between 27. 675 and 27.6.

    IF correct, we are seeing surface quakes round the top of the first dome but not directly over the top itself – may be due to old lava in the conduit of the volcano; but we are seeing surface EQS over the top of the second dome. The first volcano in question may be Tanganasoga and the second one close to the area Ursula called Tacoron.

    Does anyone know if there is inflation or deflation at Tanganasoga or Malpaso?

      1. For the record: El Hierro is a monogenetic volcanic area. Eruptions never occur within old cones.

    1. I really wish I could give you an answer. I can’t.

      I can’t even give you an updated 4D plot since there is too much ambiguity in the data.

      Before my last animated plot, I asked Carl if I should go ahead with the plot. There were a couple of reasons why I was hesitant to do the plot.

      One, it could scare the crap out of someone if they read it wrong.

      Misinterpreting a plot can lead to all sorts of trouble, and there is a contingent of the population which would make that leap of misinterpretation and run with it. Once they do that it’s pretty hard to extract the B/S data from the public’s mind.

      Two, the reliability of the data is in question. More that it was before the animated plot. HI04 data was growing more and more stale as time went on. It was the 26th, IGN data was current up to the 24th, and HI04 had a cut off of the 20th.

      At best, all I could to was to get a linear trend and use that to give us a clue about what was going on.

      Well, now the reliability is worse. IGN is up to the 28th in it’s data, and HI04 has lost data points. All the way back through the 15th. The last data point is now 14 Oct 2011.

      I don’t know why. It could be that the orbitals that were used have some unexplained error (the bars were getting larger) or that that end of the island is now going backwards in time and will soon disappear from our maps. (that was a joke).

      Whatever it is, it boils down to the data being questionable.

      I won’t hide data, but I also won’t put out garbage data if I can identify it as questionable. Likewise, if there is room for misinterpretation, I try to minimize that.

    1. I think it’s probably a good interpretation of the quake pattern.

      When the swarm ran south, it hit the other end of that keel and came to an abrupt halt. That fits the diagram also.

    2. It also could be a bit … interesting. Following that plot as a guide, and the pattern that the quakes have taken, I have this scenario. It’s not right, but just an idea.

      The El Golfo slide took out a sizable chunk of the island several thousand years ago. Decompression melting re-activated the mush and caused magma to push up and form the long dead cones that we see along the scar from that slide (Tanganasoga, the cone underneath Sabinosa etc…). Each feature forming as the magma becomes available.

      The stress stress load change from that slide alters the pressure on the underlying crust when a large load moves to the NW, this gives us the tension fracturing that Peter Cobbold was talking about. More of the magma in the mush goes to a liquid state and the melt percentage goes up. Being less supportive of the overburden fracturing starts and begins to propagate south along the keel of the island as the melt in that area stops holding it’s share of the load. Eventually, the far side of the islands “keel” is reached, the stresses accumulate, and any melt produced gets squeezed up at the closest available weakness… in this case, at Bob, just south of Restinga. The likely path? Along the weakest route in the debris field of El Julan.. probably the back side of the collapse scar. Most of it (the magma) never made it to the surface and now occupies whatever pathway that it was in. Material from the sediment was incorporated into the sputtering melt column and came to the surface as Carl’s oddly constituted floating Millosevichite like samples. Millosevichite can form from magma interacting with sulfate crust… which involves sediment basins and areas prone to the formation of coals. Think “Jurassic era sediment.”

      Now, with the festivities of the El Hierro keel stress changes… the underlying mantle area begins to respond with it’s own stage of stress adjustments and/or melt formation. This would explain the stark difference in the idiot(me) derived error ellipse azimuths since the bedding of this area is different that the hull of the island.

      Note for those prone to nit picking. I’m using boating terms (keel, hull) as descriptive of the island to mantle interface. I am not inferring that the @#$ thing is floating in water. Don’t go there, I am not a US Congressman like Hank Johnson. (who actually thought Guam could tip over).

      1. Yes, like it. Wish I’d spotted those curves!
        If the pointed keel were smoothed it would look like the flexure of crust and upper mantle reported under Tenerife, but on a smaller scale:
        You have the crust/mantle boundary at 14km at the periphery but flexed down to about 20km centrally.
        I like the concept of the magma being squeezed south during the swarm of 8000 and the other arguments that bring Bob into the picture. Could we have that swarm in another diagram?
        I still think the initial trigger in July was rebound-fracturing after mass-wasting by the El Golfo landslip 15,000 years ago. The transferring of that load ( 15 cubic km) away from the island to NW) would explain the GPS rise at Frontera, as the north of the crust was ‘levered up’. This is why the swarm started at the north where tension was greatest. And why the EQS at present are focussed to the north of the keel in the upper mantle.

        To me it does not look like any fresh magma injection is needed to explain the EQ patterns to date. That must be good for the outcome at Hierro, although we amateurs are completely at odds with what few comments we have heard in the media from the local scientists.

      2. The tension fracturing and subsequent settling arising from the gravitional collapse of the NW area of El Golfo must have happened some time back.

        And we could be seeing some tension fracturing again. But what would be the likely cause now?

      3. I have not been able to find anything on rates of crust rebound following mass wasting events- for Canaries or elsewhere. But Scandinavia is still uplifting today after ice loss 12000 years ago – similar to El Golfo 12to 15oooyears ago.
        There was no big EQ to trigger the swarm in July that I know of, but I have not looked in detail.

    3. Looks interesting. Assume the brown layer is the volcano. Could you clarify what the green layer is? And where would the sediment layer appear?

      1. @ Karen: I think if you split the brown area with a line coming in parallel to the bottom line, but about 1/3 up, then the bottom 1/3 would be the sediment layer and the top 2/3 the volcanic rocks that breached through the sediment layer in previous eruptions. What do you think?

      2. I honestly do not know. I would like to see the sediment layer and the ocean crust shown as well, if feasible.

      3. Alyson. Yes I think so. But it may only be a nominally sedimentary layer in the centre of the island ridge as past eruptions of magma penetrated it- it may be almost all basalt now. To the south near Bob there may be more sedimentries left, to allow as Lurking says above, the generation of the Millosevitchite (and maybe Bob’s gas?)
        The sedimentary layer tops the crust, so it is 8km down at periphery but about 6km deeper ( 14km) centrally. This is good news as it means that much of the swarm of 8000 occurred in what remains of the sediments. So I jave stopped regarding it as abarrier to be passed. The EQs at 8-14km have not spread shallower and have virtually stopped now. If there were fresh hot magma there I doubt EQs would have stopped at that level. I think now that the reson for that the swarm of 8000 happening at 8-14km may indeed be that the old sedimentary rock, previuosly wrecked ny old eruptions, is the weakest zone when the ‘rebound fracturing’ started.
        That diagram has changed my perpsepctive. There is no longer any barrier at 8km to worry about. The activity is over there, the rebound fracturing has been accomodated there. No worries.

    1. Thank you Karmela for that wonderful gallery of photos! Those rust red areas certainly show why the island is named El Hierro. Now I want to visit! I think I will wait until things have calmed a little though as I am now a pensioner and can’t run as well as I used to. 😉

    2. Great photos, thanks! Makes you realise how many cinder cones, lava flows and other volcanic markers are all over the island.

    3. Most interesting photos Karmela, thank you. It certainly shows how many small vents have opened in the past. Does anyone know if they were formed about the same time during one longish episode of activity?
      Some look faily new although well eroded. Others have much vegetation almost concealing their shape and origin.

    4. Amazing photos of craters, cinder cones and old lava flows in a spectacular landscape. Looks a lovely place to visit. Thank you for sharing them.

    5. Beautiful! Pictures like this make me think: that is a place worth to visit. Art made by nature – what a pleasure to photograph.

      By the way, if you want to see Tanganasoga from Google Earth’s point of view:
      Paste 27°43’42.41″N 18° 2’25.96″W into the destination field and zoom in until you see a small green mountainlike icon. Move the cursor to it and you see the text “Pico Malpaso”. Click it, then click “Tour” and you will take off for a little flight (35 seconds) above the highest mountain of El Hierro. It starts with a view to the NW including Frontera and then turns north. Tanganasoga appears on the right hand after about 23 seconds, Sabinosa is behind it.

    6. I was there in 1964 for 6 weeks, camping by Fuente del Lomo. I am amazed at the pace of change: you even have tarmac roads now! and an airport….

    1. I think this is because the earthquakes are stronger – magnitude is measured on a decimal logarithmic scale, so a 3M earthquake is 10x stronger than a 2M earthquake, a 4M earthquake 100=10^2x stronger than a 2M earthquake, etc. I think that’s why you see an exponential increase in released energy, but I don’t really think these cummulative energy charts are very useful. But, I am not a geologist, so this is only my own opinion.

      1. 10x in amplitude – but 31.6x in energy… from:

        “Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released, and each increase of 0.2 corresponds to a doubling of the energy released.”

  23. It appears there have been no quakes since 19.36 on IGN and there would seem to be too many people trying to get onto the Actualidad site.

    Yesterday they said: ‘Referring to the seismicity is occurring in the north of the island and is being produced at 20/25 miles deep, that Committee stated that it requires a thorough study “because the current data can not conclude anything” . Also emphasized that the constant presence of tremor difficult to locate earthquakes, necessitating the placement of a seismic array to characterize the seismic signals.’


    1. “…. requires a thorough study…”” …..current data cannot conclude anything”
      It would help if they cured H104 as requested by AVCAN.
      AVCAN via GiggleTrans:
      “”We assist with the reopening of shock tunnels Roquille, which lacks internal reinforcement structure, or the withdrawal of the Red Cross, while in the Gulf do not stop earthquakes occur each time of greater magnitude, which could affect safety of the tunnel. We recall that from the scientific committee said it knew it could be happening: “I do not know”, as the GPS H. .. I04 was out of use WiFi failure. Now, the new note of the Canary Islands Government today said that the deformation is stable in the north of the island, but not clear HI04 working properly. Nor clear the doubt as to what should be the new seismicity in the Gulf: if possible relocation or a new injection of magma. We must remember that, according to its own scientific committee, that doubt had been caused by the malfunction of HI04 station. Have you noticed? Has WiFi replaced by another station, HI01, for example? We do not know, but the official IGN still provide data HI04. What so far has been adequate action by scientists and authorities is becoming unfortunate. The population of El Hierro at least deserves respect. From AVCAN ask the Canary Islands Government and the scientific committee a response commensurate with the current situation. Transparency and data (AVCAN)”””

      Not a happy situation – the scientists are blind without measurements. Are resources being restricted? Surely if there is no-one in the Canaries with the ability to get H104 working there will be a few hours’ flight away?
      And where is the network of seismometers to allow localisation of Eqs below mag1.5 ? Cant be long before we see a resignation of a scientist from the advisory committee in protest?

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