El Hierro – Day 7

Photograph by Cestomano. The lighthouse of the Orchillas was once known as the end of the world. Under this lighthouse is where the new magma chamber is forming.

This will mainly be a short update. Not much new has happened during the last few days, I will just try to explain why.

What we are seeing now is the formation of a new part of the magma chamber(s) under the island of El Hierro. The progression of earthquakes that we have seen moving roughly from Tanganasoga volcano towards the WSW is magma following a weak seam between two rock layers in the crust. This is creating a rather low, but wide, layer filled with magma. You can think of it as a cake, where the magma is a layer of custard cream between two pieces of bread.

Initially I thought that this layer would not be able to take a lot of magma before the magma would break through into the two older layered magma chambers that were created before the last eruption. My line of thinking was that as soon as that happened magma would move up into the old feeder channel leading towards the volcanic vent known as Bob south of La Restinga.

Image by IGN. The darkblue and read area is where a new magma chamber has started to form like a stacked layer in a cake.

Instead a large quantity of magma has gushed into this new formative magma chamber, which is continuing to grow. There is a rule in fluid dynamics that state that as a bladder (balloon) grows the rate of growth will decrease as the volume increases. This is why it takes more and more magma to keep the pressure at a constant level during the expansion. This is why we see fewer earthquakes as the size grows. It takes a larger amount of magma going into the system to create the pressure for the earthquakes to happen. We will also soon see that the rate of rapid uplift will be decreasing. Do not take this as a sign of the risk for an eruption decreasing. It is quite the opposite. Why? The rate of magma arriving is still constant, so, in due time it will break through.

Magma seems to have entered into the old feeder channel to Bob, how far up though is anyone’s guess. But, it seems to have stopped flowing upwards now, probably due to the opening being plugged up.

Instead we are now seeing a small amount of earthquakes entering into the zone between 16 and 8 kilometers from the surface. What is most likely is that we will see more of them during the next 48 hours; with a bit of luck we will be able to pinpoint the formation of an earthquake stack. That would be good since that could point towards a general area where there could be an eruption. Currently that is pointing towards the western area of the island, but that might change rapidly.

Image by IGN. A few earthquakes have started in the 16 to 8km depth range.

When the magma enters the region 8 kilometers and above the earthquakes will most likely stop, or be few and far apart. The reason for this is that there is a layer of old sediment there. Then there will be a brief flurry of earthquakes as the magma breaks through to the surface, unless it finds an old lava-tube, then it would be a quiet onset of eruption. The eruption would be of basalt or basanite, so it would most likely be a quiet effusive eruption. In the beginning it could be more vigorous due to gas pressure release.

I would still not rule out that the eruption will happen somewhere along the old feeder channel that lead out to Bob. If that happens I believe the eruption to happen somewhere closer to land than during the last eruption. It could also happen on land.

During this second phase of the eruptive cycle the level of information given out has been much improved. IGN is now giving out real GPS data instead of cumulative data. That is a huge improvement. Also Pevolca has started to write reports that are filled with technical details that helps a lot, and removes any chance of people accusing them of hiding data. If IGN and Pevolca keep up with this new openness they will find that people will be much happier. So, from us a big thanks for this new approach.

I would also like to point out to the political establishment of El Hierro that the last eruption will in the end be a big boon for the Island. Before nobody pretty much knew that El Hierro existed. Now many do. And that should in the end raise the number of visitors, especially from the rather large cadre of volcano aficionados. So, instead of trying to hide your volcano, flaunt it a bit. Be proud of it, and people will come to watch your beautiful island.

CARL

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980 thoughts on “El Hierro – Day 7

  1. just in, there is 16km dept 2.8 almost 1/2 hour after the last 4.2, quakes are smaller no and back to 19+km

  2. Sorry for not posting the links. Judith and Luis are missing right now. So many posts. Just got back home and didn’t change clothes to read all the news. And now this one at Etna. Tomorrow is another (long) day.
    BBGN

  3. I’m pretty sure Carl would call this a “wet quake”

    Notice all the spectral banding when you look at it up close.

      • “Reason” he says…

        On the plots I am posting in a moment, the “human check” word was “Motley Crew”

        So…

        some Motley Crewe 😀

    • Lurking what do you mean by wet quake? All I can come up with is, a dry quake is one associated with tectonic quakes, and wet magma. But I am not sure if I am missing something here.

      • But the zoomed picture in detail shows a nuance of coloring, meaning it’s a wet one – not a single event, but a long period of varying magnitudes. They are connected if that’s what Lurking is trying to say…

      • “Wet Quake” is not really a technical term… at least I don’t think it is. In Carl’s parlance, it’s a quake with a magmatic signature. In other words, and LP (long period).

        In this case, you can make out individual spectral banding which are likely akin to harmonic tremor, though that’s not what it really is.

        As you push air through an organ pipe, tuba, trumpet, trombone etc… what you get for a tone depends on the shape and length of the pipes or tubing. In this case (I believe) the individual cracks act as a semi resonant chamber as they fill with magma.

        Now… advancing my idea of advancing magma, a few plots, 4D, (sort of, if you look at it with one eye closed and bottle of whiskey)

        Plan view

        Notice how the quakes originate in June, and progress south westward as an advancing, and expanding front. To me, that’s magma seeking a path… and being quite successful in doing so. As is spreads more and more, that is likely the cause, or one of the causes for the recent decline in elevation for the swollen areas.

        Now to complete the picture, the view looking North.. in profile.

        And East, also in profile.

      • Wet as in opposite to the Dry quake, which is a term for a purely tectonic event.
        What I am talking it as Lurking wrote a Longperiod earthquake. And the wet part, well magma is molten so it kind of looks like the signature a fluid makes in tubes.

  4. On Avcan facebook page there are so many comments by frightened people on the island after all what happened last night and this morning .

    El último gradísimo de las tres y media, creo, me ha sacado de la cocina, donde estaba tratando de dormir un poco y he sacado la colchoneta afuera, pero ha sido tan tremendo, que no puedo dormir y ahora estoy tomándome un chocolate y escribiendo estas lineas. Espero que no haya más así de grandes. He oído caer alguna piedra, pero nada importante. Buenas noches a todos.

    The last three and a half gradisimo, I think I got the kitchen, where he was trying to sleep a little and I have taken the mattress outside, but has been so tremendous, that I can not sleep and am now taking me a chocolate and writing these lines. I hope there not more so large. I heard fall a stone, but nothing important. Good evening to all. (Translated by Bing)

    http://www.facebook.com AVCAN

      • Hi Ursh I am actually in the UK at the moment but my family are still there.
        I am very worried for eveyone at the moment .

        • I know what it is like being far away, worse then being there, take care they will need you in times like this

    • Judith, Good morning. You are the one to be here in such a moment.
      I cannot cope with all translations, there are so many testimonies…
      Some of them made me sleepless… I wonder how those poor people are feeling…
      And now CHIE is showing signs of a new break of the lull. I see an eruption coming…

      • Hi Renato

        I know I felt the same when I have just read them.

        I will only be able to post on an evening for a while but will try to pop in during the day to keep in touch .

    • Well… if I’m right, the magma will find a place to either settle down and cool into another plutonic emplacement, or vent out to sea… based on the progression of the quake front (where they are occuring) and that GPS based inflation seems to be slacking off… provided it’s not an error in the system.

      Would it frighten me? Yes and no. Freak me out, hell yeah. Cause me concern? You betcha. The greatest fear is the fear of the unknown.

      I can’t say that it won’t erupt on land, but right now it seems to be seaward bound.

      • For the record… I’ve been in a 3.2. The quake didn’t scare me. The reaction of the apartment building did. I could sense the framework of the studs and rafters shifting back and forth. Then it was over. The next day the geologists announce that they had “found” a new fault line that ran up the middle of San Diego bay and up through the airport.

        Before that, they didn’t know it was there.

    • Hi Judith, good morning. Thanks for the posts. It must be pretty scary for the people of EL Hierro, my heart goes out to them.

      • Morning Hattie

        Yes it has been a very scary night for them we can only just watch and wait and hope the authorities take action soon.

  5. there has to be HT there, if you look at the other islands, but having a large quake then the next one 5km up then going back to deep ones, there must be a lot of holes in the Swiss cheese, plus I think the hot spot must be in a very active phase, someone compered the Canary hotspot to Hawai, so it thinks I show you

    • I do not like large things close to Pantelleria…
      But, it is most likely a purely tectonic quake. They do occur there frequently.

        • There have been a few around 2+ pretty near to Pantelleria these last few weeks but this is the biggest.

          Odd thing about the Med is most of the quakes are much less than 20km and then a few are 100 km – just the odd one in an active spot.

          • I didn’t save it but think I recall a 2.4 at 2km depth just north of Pantelleria, a couple of weeks back. That would be tectonic, I guess.

  6. Well I am starting to fall asleep at the comp, so going to call it a night. BBGN everyone. My thoughts are with the people of EL Hierro.

    • 1153751 03/07/2012 07:04:36 27.6967 -18.1532 19 2.5 mbLg SW FRONTERA.IHI [+]
      1153754 03/07/2012 06:53:56 27.6883 -18.1514 19 3.0 mbLg SW FRONTERA.IHI [+]
      1153747 03/07/2012 06:47:00 27.6858 -18.1480 19 2.9 mbLg SW FRONTERA.IHI [

  7. Yesterday was a new record regarding the number of medium sized earthquakes at El Hierro. 24 earthquakes happened that was larger then 3M in magnitude.
    So, althought it was the lowest total number of earthquakes, it still was the day with the highest energy release. This due to the stupendous activity before and after the 4.4M earthquake.

  8. the last one on the SW tip of the island, it will be quiet for a bit now, before the next….at least it will be day time for the islanders.

  9. Regarding rescaling.
    Imagine a 3M quake, it is fairly substantial if it is within a volcano. A week ago we jumped at every 3M. Even I did jump a bit about them. A 3M is normally something that tells us things. During the last days we have seen even larger earthquakes that than. Up to an earthquaked that knocked on the door wanting to be let into the “large volcanic earthquakes club”, ie. it was almost a 4.5M quake.

    Now, picture a mental image of how the 3.0Ms looked last week.
    Now look att this link 06.53 quake is a 3.0M quake.
    Looking fairly piddly is it not?
    So, they have rescaled again to encompass the rather schtumping quakes we are seeing now. A scaling that is good for a 3M is making the 4Ms to hit the roof, and vice versa. I for one rather like to be able to see the 4Ms well and have piddly looking 3Ms.

      • That would make Renatos Day. Following the slug of magma moving towards Brazil for the next 20 years.

        • And us here scaring the hell out of brazilians by making scenarii and predictions of what will happen when the Hierro magma surfaces in Brasilia or Rio de Janeiro… Within 20 years we should finally gather a bunch of nice ideas…

      • Nope.
        There is a slab reversal at this hotspot (ancient microplate). That’s why sedimentary layers can get mixed with magma at great depths. And that’s how Restingolitas were formed. We are witnessing another of these reversals and when it is accomplished, we’ll have again magma spewing out in Lazarote and then further NE, to join Laacher See hotspot.
        As you see, you’ve been wrongly pointing this towards S. America.

  10. Good morning /evening everyone. To the people of El Hierro. My thoughts are with you. What a dreadful night you have had. Be strong and be very safe. If it helps, you know now that many in the world are watching with you.
    I think the unknown is the worst thing. Once someone can SEE something then people can accept the reality.
    Thank you to all of you who stayed up watching, Carl, Henri, Lurking, Renato, Hattie and Ursh. I am sure your comments have helped many who are trying to understand what is happening.

  11. Indeed Diana – I agree so much – and if only Elvis can put on his show out at sea, without rocking the house down… We watch and wait.

    And I trust they are monitoring Tanganasoga very carefully…..

  12. Good Morning/Evening lovely people! Once again the events of El Hierro are keeping me awake at night and distracting me from my own personal volcano of a pile of ironing (Hierroing??) With baited breath…

    • They don’t mess about in Brazil. A colourful country full of tropical exuberance:D

      PS My spell checker is weird….I can choose English from American English or Australian English! So I either have to go with “Hi Folks and Howdy!. Have a good day y’all ” or ” G’day Blue. Have a bonzer time and watch out for the roos.”
      I am afraid that “Good afternoon. I trust you are well. Despite the awful weather I do hope you all have an enjoyable day” no longer is acceptable on the internet! So one had better forget Her majesty’s English unless one is dining at Buckingham Palace.
      😀

  13. Because of the depth of the magma, could this just be the beginning of a weeks if not months long process of EQ’s to get the magma to the surface? Like last summers swarm it took several months to get it to eventually bob. I know the energy is well in excess of last summers, but if it is discovering a new path could it take just as long?

    • Hi there, most people are on another page.( What did Elvis have to do with the island). Your post might get overlooked here, sorry I can’t give you a very good answer to that question.

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