14 comments on “Volcano & Verdelho – PICO – Azores Part 5

  1. I apologize to everybody who went back to our previous Azores posts and found – no picture captions and some other inconveniences. I am working on it… I had originally set some text to black instead of the WordPress light gray, for better readability on the white background. Which of course doesn’t contrast well on our new black background 😦 That concerns some of my other older posts too, I hope to have all fixed soon.

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    • Bongo’s new island is very, very soft and the wave action is strong. Don’t think it is going to retain its new shape for long. It is the very definition of an ephemeral island. I don’t recall watching something like this before. Cheers –

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  2. Some interesting papers out online today!:
    Post-supereruption recovery at Toba Caldera
    It says that Sinabung’s lavas are very similar to those of Toba, and therefore it could be possible that S. is tapping the same magma reservoir. – Of course I cannot judge the scientific results, but… I would like to see the opinion of other experts on that.
    The second is for the subduction enthusiats:
    South-American plate advance and forced Andean trench retreat as drivers for transient flat subduction episodes
    And another one on Campi Flegrei!:
    Progressive approach to eruption at Campi Flegrei caldera in southern Italy

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  3. And Bogoslof aviation alert has been raised from Yellow > Orange > RED, and the Volcano Alert to WARNING today. A pilot reported that the eruption has produced an ash cloud as high as 34,000 ft asl, and the Worldwide Lightning Location Network has detected lightning associated with the cloud. – 1h:20min later, the update was that seismicity had declined.

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  4. crikey, if the theory postulated by Kilburn, de Natale and Carlino in that last paper is corroborated by events it will be a truly seminal paper. And kind of scary. But it makes a lot of sense out of the mixed signals coming from calderas and why eruptions often occur some time after a period of intense seismicity. They say that recent subsidence in the caldera could simply be relaxation of stress through the geothermal field. This is occurring because of a large number of microfractures forming due to the underlying bedrock reaching the limit of elastic deformation. Another sill intrusion would presumably push through this threshold and result in failure of the overlying bedrock and allow magma to ascend possibly to the surface through dikes etc. making the chance of eruption much higher. The main point being that accumulated stress in the caldera is still very high and recent relaxation is no sign of the situation easing, rather, the contrary.
    They really should work on their town planning down there in Naples and move people out of the caldera rim proper. This would at least mitigate the loss from any small eruption. The good news is that the recent sills are likely to be thin and will rapidly cool down below the point where they are eruptible. What we seem to be looking at as the most likely scenario is a dike intrusion resulting in a small surface eruption.
    The worst case scenario is a magma chamber above which you have a fractured roof that is close to failure as it has reached the limit of its elastic deformation and a surface eruption that evacuates enough magma from the main chamber to depressurise it sufficiently to turn crystal mush into eruptible melt. Bubble nucleation will do the rest -> fragmentation -> roof collapse -> ignimbrite sheet. This is by far the least likely outcome, but a distinct possibility.
    Much more likely is an eruption like the recent ones at Rabaul or Taal.

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    • and because that piqued my interest, I read this paper, released in March:
      http://onlinelibrary.wiley.com/doi/10.1002/2016GC006569/full
      which states that the degassing is now from a deep (7km) magma source and that the shallow magma body intruded in 1982 – 84 has since crystallised.
      In other words the roof over the chamber is under strain and close to the limit of what it can accommodate by elastic deformation but at present there is no sign of an eruption from a shallow body. However, should a new injection of magma occur from the deep source, it will have an easier job of reaching the surface.

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    • Hi Bruce, thanks for food for thought, I have been away for two days and have yet to read the CF paper. I think it has caused some panic in the population already, which it shouldn’t for the time being. There are no signs at the moment different to what has been seen the last couple of years.

      Do you know this website? http://meteovesuvio.altervista.org/ It’s in Italian; you’d need a translator for websites, and then you’d need to be able to concentrate hard and really understand what google spits out on one hand, and what the author is trying to convey on the other. Go back in the archive and read the unfolding of the story around Dr. Natale. I am not going to utter an opinion of my own, but I would like to see what other, trusted scientists, have to say about the new paper.

      Apart from that, I wholeheartedly agree with what you said about mitigation and planning for the worst. It should have been done decades ago.

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    • I’ve read it now and still need to digest chunks of it 🙂 So, if I got it right, we are completely wrong thinking that if a bulge goes away, after a good inflation, the stress in the crust would relax to its previous values. It does not, especially not as not many VT quakes have relieved much stress under ‘quasi-elastic’ behaviour. Further uplift will add to the already accumulated stress and therefore change the behaviour of the crust to ‘inelastic’. Under rigid conditions, stress will be relieved by faulting = VT earthquakes become frequent, paths for hydrothermal fluids will crack open…

      I wonder if this applies to all volcanoes or just to those that have prolonged periods of repeated inflation? Perhaps all volcanoes have them, even if not particularly noticed. Anyways, it shows to be doubly vigilant whith volcanoes like Iozan now, which has been inflating for many years. Don’t know about deflating though; mostly the reports say, inflation has stopped – alert level goes down, people breathe more easily.

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      • Hi Granyia, that is how I understood it too. But it made me go and buy “The Fundamentals of Physical Volcanology” by Elizabeth Parfitt and Lionel Wilson.. The first three chapters are precisely on magma genesis, diapers and dike propagation are great.. When I get my act together I’ll try and write an article on it (best way to learn!!). But it has explained precisely the thing that has bothered me for years: why more dense rocks (mafic) rocks sometimes rise and erupt over less dense rocks (crust) and also the role of gas, which came up recently in connection with Kimberlites. Great book.

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        • .. and she explains the difference between flow (diapers) and elasticity (silly putty) that stretches then snaps.. (quakes) .. which can be a source of confusion when reading de Natale because he uses inelastic to mean when the strain can no longer be accommodated by country rock and it snaps. For Parfitt this is part of elastic behaviour (as opposed to flow).

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          • Sounds like a good book, but gosh, that’s pricey on Amazon too, as is my favorite: Schmincke, Volcanism. I am reluctant to buy any of those, though, because they are from 2008 and 2005 resp. I fear, with volcanology being such a relatively young science, that some stuff in them is becoming outdated or obsolete altogether. But none of the newer books seem to be so comprehensive and have the great user reviews as those older ones.
            As I was searching for the book I stumbled over this, I thought you’d like to know a bit about one of the authors: https://www.theguardian.com/education/2005/nov/22/highereducationprofile.academicexperts

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  5. btw, great article Graniya! sorry I got kind of distracted by CF. What amazes me about Pico (same holds true for Teide over in the Canaries) is how steep they are for fairly primitive magmas.. is this because they are not as hot when they erupt as, say, compared to Hawaii?

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    • Thank you! Yes, I have wondered a bit about that too. The explanation for the steepness of Pico AFTER it has started to build a cone seems convincing enough: continuous small eruptions trickle small amounts of lava from the summit, which cools while still running down the slopes. It’s like building a sand castle on the beach by sprinkling watery sand on top. The sand solidifies before the flow reaches the foot and the castle gets steep. My question was, why – Topo having been a shield volcano on the same island – did Pico become a stratovolcano in the first place? It did not have explosive eruptions producing tephra, so, what are the strata? I can only think of lapilli/lava bombs as the “rubble” between lava layers, perhaps spattering from Strombolian eruptions. The logical follow-up question would of course be, why does spatter etc. not produce stratovolcanoes in Hawaii? The temperature for Pico lavas were calculated as 1100-1200°C which is normal for basalts and similar to Hawaii (1100°C)

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