El Hierro – Day 2

The face of El Hierran politics, Alpidio Armas.

This will just be a short update with the information that has come at hand.

There seems to be a full on war between Pevolca, Involcan and José Luis Barrera VP of the ICOG (Spannish Association of Geologists). Pevolca has stated that there are some reneval of tectonic earthquakes, with no risk for the population or any need for any measurments to be taken. They also point out that there is no increase in gases. They do though mention that they will be watching things. They have also stated that there is no inflation at El Hierro (GPS).

Involcan has stated there is inflation after studying the GPS system of Professor Sagiya from Nagoya. They also point out that the reason for Pevolca not being able to see any heightened gas levels is that they have not measured the gas since April 5.

http://www.facebook.com/pages/INSTITUTO-VOLCANOLÓGICO-DE-CANARIAS/134042953295772

José Luis Barrera and the ICOG have issued a statement that the more than 350 earthquakes are tectonic, but that they might be a run-up phase for renewed volcanic eruption. They also note that the activity is unusual.

http://www.europapress.es/comunicados/noticia-comunicado-colegio-geologos-muestra-incertidumbre-repunte-actividad-simica-hierro-20120626152109.html

Meanwhile in the real World

While the Spannish authorities and organisations are involved in their usuall pissing contest there are some things worthy of comment.

A little tidbit on the earthquakes during the 48 last hours…
Yesterday had the fifth highest recorded number of earthquakes (241), the highest recorded number is close to 454, and that was in August as the former wad of magma had it’s peak of arrival.
But what is really interesting is that if one take a look at how those quakes break down into size…
Yesterday first, then August number-record.
0-2M 55 (448)
2-3M 180 (6)
3<M 8 (0)

And that would have made yesterday into releasing 5 times as much energy and destroying about 32 times as much rock. It was the record of all time energywhise. This leads me to believe that the amound and speed of arrival is higher this time around. So, the last two days have had the largest accumulated seismic energy release since onset of activity at El Hierro. Energy record in short. And that is note noteworthy according to Pevolca.

LP 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

Image by IGN. The First LP Earthquake.

Second LP

Image by IGN. The Secong LP Earthquake.

Third LP

Image by IGN. Third LP Earthquake, and what is most likely onset of a heavy magmatic intrusion upwards.

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. The Long Periodicity Earthquake is caused by an initial earthquake that opens up a fissure, sill or dyke, after that magma moves in to fill the opening, and that creates and unusual type of earthquakes.

Conclusion

There is no reason that I should recant on what I wrote yesterday. I still believe that there is a rather high risk of a new eruption at El Hierro. I still see no reason to not believe it will be in the southern part of the island, or out in the ocean south of La Restinga. I still feel that La Restinga is not entirely safe for it’s population.

Update

While I was writing this post the signal changed sufficiently for me to believe that there is risk that the eruption is either about to start, or has already started. We are all waiting for news, and think about the unprotected civilians in El Hierro.

CARL

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576 thoughts on “El Hierro – Day 2

  1. Volcano discovery updates frequently on Bob too. We used to have an RSS feed but as long as theirs is still now working, i am not adding it again right now. ( Thought if i say this here now, maybe someone fixes it, i am checking if it works once a day on my testblog)

  2. Official Statement:

    THE PEVOLCA RAISED TO YELLOW LIGHT OF INFORMATION TO THE PUBLIC IN THE AREAS OF THE THE JULAN AND LA DEHESA27-06-2012… 13: 55 – Ministry of economy, finance and securityThe pre-emergency phase is set to alert in this area situation taking into account the volcanic riskThe Steering Committee of the Civil protection by volcanic risk (PEVOLCA) Plan has decided this morning raise the traffic lights to yellow for informing the population in the Julan and La Dehesa, in El Hierro. Also the pre-emergency phase is set to status of alert in these areas since it is where there is more volcanic risk.This decision was taken given the increasing seismic activity that is occurring on the island since last Sunday. Scientists moved to the Steering Committee that the origin of this seismic activity as well as the horizontal deformation observed, about 3 centimeters, can have an active magmatic process as the source to a depth of 20 kilometers.The meeting was held via videoconference between Las Palmas de Gran Canaria, where he was the Minister of economy, finance and security, Javier González Ortiz; Santa Cruz de Tenerife, with the presence of the President of the Cabildo, the subdelegation of the Government, the director-general of security and emergencies and the spokesman of the Scientific Committee; Madrid with the director-general of Civil protection; and iron, with the presence of the island and municipal representatives.The Steering Committee has taken the opportunity to remind the recommendations of self-protection by seismic movements which in their day were issued and which can be consulted on the http://www.gobiernodecanarias.org/dgse/sismo_hierro page.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.

    Source: http://www.gobiernodecanarias.org/noticias/index.jsp?

  3. @all:
    In a far away country from sunny El Hierro…
    A small earthquake swarm has taken place in the Laki fissure. The 3 earthquakes in the group have been 0.6, 0.7 and 0.9M in size. The earthquakes are checked by IMO.
    Even though this is in a very ominous and quiet spot of Iceland, there is nothing pointing to anything to exciting happening. That would take quite a bit more than that.

  4. Hi all

    Just reposting what I wrote above:

    I have been reading through the papers collected over the period of the last build-up and I think it is Muenn who focuses on gravitational spreading and flank instability, while Stroncik, who I provided a link to yesterday focuses on the different rates of crystallisation, which suggest that magma cools and plugs up previously used conduits, and so finds new ones through the sedimentary strata.

    I forget which paper suggests (Day? Carracedo?) that several cones erupted simultaneously 15,000 (mya?) years ago, and coated the flanks after the slips had occurred, but that historically, for the most part, magma doesn’t reach the surface. I speculate that this is because the island is so tall and narrow that it can cool the magma before it reaches the surface, and wonder if underwater cone building can occur on the flanks, while under the island proper the gases inflate but don’t allow any release, leaving magma pockets forming in the sedimentary strata.

    Vinuela at http://www.MantlePlumes.org gives a pretty comprehensive picture of the mix of geology.

    Lurking – your plots of the changing uplift last time were very informative.

    Apologies to anyone who read it before…

  5. Fresh magma – or not??

    The old aseismic gap between the upper and lower swarms from last year is almost filled in:

    ( the right hand vertical section).
    This is extremely well behaved for an injection of fesh magma from the mantle plume, isnt it?
    The pattern of a flattened N-S elongated conical ‘structure’ sloping upwards to the south is almost complete.
    So the classical interpretation of the eqs needs three fresh magma injections form the plume:
    The first injection caused the shallowest swarm, the second injection the deeper swarm, and the third slotted neatly into the gap between the first and third. in the middle.
    That’s one reason why I dont buy fresh magma injections.

    The upper and lower zones weakened by last years swarms of thousands of eqs are silent now – but are supposed to be swollen with fresh magma from last year. And all thats stopping this enormous area and depth of fresh magma intrusion from moving upwards is a layer of sedimentary rock at ca 5-8km depth, itself perforated by numerous small dykes,sills and conduits.
    Yet no-one on the island has reported any sulphorous smells or fumaroles (that could not be attributed to Bob).

    So I doubt there’s a fresh magma injection there now , nor last year.
    IMHO Hierro slid. Fron and Rest and Sabi rotated to NE about Valverde. The GPS reported it. Then the change in gravitation loading resulted in eqs resulted from fracturing of numerous small dykes etc ( Stroncik model) and the magmatic tremor was’is from compression-melting of emplaced rock.
    All we need to do now is fill in the details of how a saucer-shaped depression in the crust centred on the island but extending out to the limits of mass-wasting, responds to a plate tectonic drag ) (interestingy its directed NE wards). What movement would cause that cone shape? Its a 3D riddle. And remember the erupted mass sits on layers of clays, chalk, and other sedimentaries 3-5km thick. So if the saucer aquires a tilt a slide would be expected.
    Hierro has feet of clay – that’s why he’s different.

    Peter
    ( amateur )

    • The ‘saucer’ shape may even visible in the right hand vertical section in the eq map (URL given above)- as the curve in the lower limit of the eqs. And the red dots ae following it nicely- like a jigsaw. Some magma!

    • Peter, there are a few small details which cause me to question your otherwise eminently plausible theory. First, very few of these earthquakes have the clearly definable S and P wave signature of tectonic quakes. Second, since the density of rock is higher than that of water, if Hierro truly rested on clay there would be a depression where it sits and any movement would be against this depression. How much energy does it take to move an entire island several cemtimeters sideways and up? I suspect significantly more than that cumulatively released as earthquakes over the past few days.

      Furthermore, how could El Hierro slide up, against gravity? Isn’t “sliding up” a contradiction of terms? The only explanation I can find for the up movement is that the island has been lifted by a “hydraulic jack” in the form of magma – and the only way magma can do that is if there’s been a substantial fresh injection thereof.

      • Henri,
        I have been struggling for months on and off with visualising the forces at play on saucer shaped depression in the crust ( thats based upon Tenerifie data) acted on by drag from the mantle motion. Enormous forces there- the basis of plate tectonics – that are dragging the plate NE wards. So there’s no shortage of motive force to shift Hierro. I visualise in v.s. a saucer that deflects the mantle flow downwards by about 10km at the centre of the saucer, with the result that the leading edge of the saucer ( its SW arc) is subjected to uplift. So over time -200 yrs? – the island has been tilted from its crust upwards from the SW – the whole lot. As a result the erupted mass above the sedimentary layer ( ie above about 5-8km depth) becomes off-balance and imposes a strain on the sedimentaries. So eventually it slides , to the NE, down the saucer. The uplift is tricky. We have to suppose that the greater part of the sliding mass was sliding down the saucer, putting its central mass to the SW of the island proper below the El Julan slides, and pushing Fron,Rest, Sabi up the other side of the saucer. As Valverde stayed fixed, the motion may have been more of a rotation….its gets more difficult to imagine. Without subsea GPS it cant be proved.
        Peter

        • Basically you are talking about a slo-mo Bradyseism.
          If you just take into account the 3 armed faulting/fissure-zoning you might get somewhere.
          In this description I can actually see it infront of me, and it seems a bit less off now. The basic assumptions in this description follows the laws of physics, and also conform pretty much to what we know of the innards of El Hierro. But, as I said, I think you need to factor in that the Island basically are divided in 3 separate parts by the riftlines.

        • Hmm… Uplift caused by an off-centre situated El Hierro on a sliding (and rotating?) saucer. Provided you can balance the weight of EH with something more massive on the other side, possible. The other explanation is magma accumulation and if we consider the fact that the Canaries sit atop a hotspot, I’m afraid Ockham’s Razor is very much against the sliding and rotating saucer, even though it’s not physically impossible.

          • Henri,
            That’s just where it gets interesting. The saucer + sedimentary slide model does not require a plume hot spot. Once a small eruption has depressed the crust slightly further eruptions at the same spot are predicted, without fresh magma boluses arriving from a putative plume. There are seamounts all around the Canaries – on basis on a plume driven process we’d need to postulate one plumelet each.
            Occam is better at preserving status quos rather than questioning perceived wisdom – I’m not a fan of his.
            Peter

          • But Peter, a hotspot is so much larger, in fact so large that it can power several volcanoes at the same time as we see in Iceland and Hawaii. We also do have a hotspot to fit into any explanation model even if the elegant, I will grant it that and as a theory one I approve of, saucer & sedimentary slide can do without.

    • There is a magma chamber or simpler an area of magma accumulation under the El Golfo Bay at a depth of 16 – 28 km (area of the syneruptive earthquakes between Oktober and November 2011). Fast magma movement during the eruption caused these earthquakes.
      The preeruptive earthquakes are caused by magma migration. The magma tries to find a way to the surface and break the rock.
      What we see at the moment are earthquakes caused by an intense inflow of magma which is indicated by the rapid uplift. The earthquakes are at different depth because the old feeder tube is most likely blocked.

      • Vishy,
        How do you explain the intial (july-Oct) upper eq swarm at 10-15km depth? For magma to get up there from the mantle there it did do silently, through deeper zones that subsequently became seismically active ( in the second and third swarms).
        Its an upside down volcano!
        Peter

  6. OT: Don’t know if you guy’s have heard, but my home state of Colorado is pretty much on fire right now. One of the wildfires has burned over 87,000 acres and destroyed 251 houses. Another one down near Colorado Springs has caused the evacuation of 32,000 people! 😦

    • Yes, Tyler, it is an awful situation there. Many of your neighboring state are battling fires, too. The firefighters are dealing with so much – high temperatures, winds and extremely dry conditions. I hope you are not too close. Stay alert and stay safe.

    • Hi Tyler – No this hasn’t been covered by the news in UK so far. What’s the cause – drought? I always hate hearing about wildfires – is your home affected?

      • Thankfully, I”m not near the fires. One was caused by a lightning strike, and that one burned over 80,000 acres. The other one, the cause isn’t known yet.

      • It is al;ways so very sad when peoples homes and possessions are destroyed by natural forces. I think that applies whether it is one person or hundreds. Most important though is personal safety and this is what worries me with this situation in El Hiero too.

    • I feel for you, I know what fires can do and how fast they move, I was with Fire control (communications) in my younger days, also have been up for days on end watching and extinguish embers on my own property

  7. earthquake2012-06-27 13:12:47.6
    1hr 02min ago 27.71 N 18.11 W 19 ML 3.3 CANARY ISLANDS, SPAIN REGION

  8. Could someone please expalin why the area of El Pinar and Monacal are not on yellow alert as these were the main areas last night that were feeling most movements.

    I have just been reading comments on the Avcan Facebook page and again people are posting they have felt movements over the last hour again.

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