Posted on by Jón Frímann

Special report: Update on El Hierro volcano eruption

While everything is quiet in Iceland. I am going to continue my coverage of the eruption in El Hierro volcano. Information in English also seems to be lacking for some reason. Please note that I have little understanding of Spanish, so I am just using the data that is available to me on the internet to figure out what is going on.

First I want to say that I am not a expert. I never claim to be one. My knowledge of volcanoes and earthquakes are the result of hard work and studying them on my own (reading research papers and other sources).

It is bit unclear what is going on in El Hierro. But from what I can tell least two things have happened during the past 24 hours. The first thing is that a eruption started at ocean floor around 04:18 UTC yesterday (10 October, 2011). This eruption appears to have been small and was not noticed on the surface of the ocean. Around 06:10 UTC this morning (11 October, 2011) a large movement of magma started to take place inside El Hierro volcano. Where exact break up of this magma is going to take place is unclear at the moment. But it is clear that a eruption is taking place and it is more chance then less that magma is going to find it self a new pathway up to the surface soon. As I do not think that the current eruption vent is keeping up with the current magma that is under El Hierro. But it is worth to notice that El Hierro does not seem to have a magma chamber, like Eyjafjallajökull volcano in Iceland so the eruption size is terminated by the current inflow of magma.

Here is a comparison of harmonic tremor charts from yesterday and today (10 and 11 October, 2011).


The harmonic tremor as it was on 10 October, 2011 at 21:08 UTC. Copyright of this picture belongs to Instituto Geográfico Nacional.


The harmonic tremor as it was on 11 October, 2011 at 20:29 UTC. As clearly can be seen it has grown by a margin or more (I can’t tell for sure) in the last few hours. Copyright of this picture belongs to Instituto Geográfico Nacional.

What is however really interesting is how this eruption is changing fast and without any warning at all. But this is however something that might be expected from a volcano like El Hierro. I see in the news that they are expecting earthquake activity before new vents or fissures open up. That is wrong assessment in my opinion. As new eruption vents and fissures can open without any or much earthquakes activity at all. Earthquake activity before a fissure vents open up depends only on the rock that the magma has to break trough. In many cases it does not have to create any earthquakes before a eruption starts. Good example of this is the eruption in Heimaey Island in the year 1973. Only a small earthquake swarm was detected before a eruption started. All I personally except before a eruption in a new place on El Hierro volcano is a minor earthquake activity. It is also hard to know if that earthquake activity can be detected based on the amount of harmonic tremor taking place at the moment.

Here is my personal assessment on where eruption might take place in El Hierro. Please note that it might be completely wrong. But I base my assessment on the data out there, that assessment might be wrong.


The most chance of the eruption in El Hierro in my personal opinion marked by the two red circles. Copyright of this picture belongs (original) to Instituto Geográfico Nacional.

There have been some deep earthquakes in El Hierro volcano over the past few hours. This deep earthquakes mean that new magma is flowing under El Hierro volcano. This means that the flow is steady (pressure pulse in the magma creates the earthquakes). So this eruption is far from being over it seems. How long it is going to last is a good question that currently nobody has a answer to at the moment.

I am going to update this blog post if I have to or if something new happens in El Hierro.

597 Replies to “Special report: Update on El Hierro volcano eruption”

  1. Thank you for this update Jon. You are very modest. Your knowledge of Icelandic volcanoes is second to none.

    1. For those not used to English sayings. The above means Jon ‘s knowledge is excellent

  2. carlosxabier on Twitter (#elhierro) just now
    “Carmen Lopez from National Geographic Institute has said that a new eruption closer to the coast would be ‘more explosive’.”

    I favor the top circle personally

  4. Thank you Jon.

    Your prediction of possible eruption sites seems sensible based on EQ patterns. How do the red circles above match the plots of EQ activity that Lurking has been doing?

    Could the lack of a large magma chamber be because EL Hierro is a new volcano forming in the remains of El Golfo’s caldera? But I found the following hypothesising about the magma system under El Hierro; it seems to be made up of small magma chambers not a large single one.

    http://adsabs.harvard.edu/abs/2009CoMP..157..593S

    1. There is nothing such as a magma chamber, they are all different versions of intricate magma reservoirs, consisting of various odd features in a fairly tubinged spoonged way.

  5. “El País”, one of the top leading newspapers in Spain, has an English edition, with a brief summary of the spanish news.
    Maybe, you can find there some information.

  6. Hey Jon. Nice blog! I am in constant contact with my friends in La Restinga, that has now been evacuated. I may not be able to inform you any further then what you can yourself on the actual volcanic activity or eruptions, but i can give you fast firsthand info on procedures on the Island. Please fell free to get in touch with me via e-mail if you are interested.

  7. I don’t agree with you Jón. El Hierro isn’t shaped the way it is without a reason. There are 3 main ridges along which eruptions occure. In this case this seems to be the southern-northern ridge. An eruption perpendicular on this would be really odd.

    1. While eruption often go into the way of the fissure swarm in question. That might well not apply in this case. Given the earthquake patterns in question.

      1. They always do. There is no central vent. These cones are al monogenetic and eruptions always origin from fissures. There are three main rifts. Also, earthquake patterns can never ever predict a fissures direction when the earthquakes focus is at least 12km beneath the surface. In that final 12km the magma can turn a lot. But it will always end up in the direction of one of the three axis.

    2. Does the nature of the eruption affect the location? Note that when you look at Google Maps (satellite image), El Hierro is riddled with small volcanic cones.

      1. Yep, these form as a result of the fissure eruptions. Remember La Palma 1971? Started as a fissure, resulted in a couple of cones. Fimmvorduhals last year? Started as a nice fissure and resulted in cones.

  9. Also I’m still not convinced there is an actual eruption ongoing at the moment. In order for a significant pocket of magma to penetrate non-ductile crust there has to be more seismic activity. Up from 14km depth to the surface is one hell of a distance, which will accompanied by more than just a small dozen of earthquakes <12km. My guess? Degassing.

    1. I don’t think that they can tell exactly what is happening on the sea bed. The only facts reported with any certainty aat the moment are dead fish, de-gassing and magma movement.

      However, if a larger eruption is pending, it may be better to say now that there is a submarine eruption to keep people out of the area and to facilitate an evacuation. They can always update the facts later when more is known; failure to evacuate is more difficult to correct.

      1. I do agree on that partially. Though I do believe that honesty will always prevail, so evacuate people, no doubt, but don’t draw unconfirmed conclusions.

  10. I too favour the top circle. If I recall one would see a cinder(?) cone in that vicinity and the red dots earlier were looking more vertical on that line, though still few and far between. El Hierro appears to be a huge volcano, since the initial vent was said to be 900 metres deep at 5 kilometres from the shore.

    Wasn’t the earlier discussion more towards a toothpaste kind of eruption, though? If it can be extruded from the undersea vent that would be so much better.

  11. I’d go for somewhere above La Restinga and assume that the magma will follow an old route – perhaps one of the cones on the ridge around El Julan

  12. This link http://www.vanguardia.com.mx/erupcionenelhierropuededurarunasemanaopocomasvulcanologo-1119300.html

    News from Joan Marti a spanish geologist working for Consejo Superior de Investigaciones Científicas- (about an 1hr ago) reports (my rough translation)

    The IGN seismographs began detecting yesterday morning a type of wave that clearly indicate the exit of magma.
    The instruments detect a submarine eruption at 5km from the coast at 900m depth.
    Which is the best scenario for the population’s safety

    “what evidence do we have of an eruption?”
    The signal on the seismographs is really clear and on top of that we have the deformation of the terrain (which has been up to 40mm)

    Yesterday evening a helicopter saw dead fish.
    So what has happened is magma has erupted (estimates of 1.200 or 1.250 [presume this is VEI?]) and with that were gas emmissions (such as Carbon dioxide) and it’s these gasses that have killed the fish.

    “so what’s going to happen now?”
    We can’t know the rythmn of the magma eruption because it’s quiet deep, and because of that we can’t know how long it will go on. But for the type of volcanism we have today in these islands it is most likely that the eruption will last for a week or slightly more. Until the pressure falls and thats it till the next crisis

    “and what happens if the magma reservoir reactivates?”
    same sort of thing as we’ve had these last months

    “so we can lower our guard?”
    Always be on guard, but this crisis has shown that things can be done well. Volcanologists are very pleased to have been able to follow this crisis from the beginning. In addition the management and carrying out of plan has worked well.

    1. The guy who gave those answers should have his head examined, really…
      It hasn’t even really started yet, and they are starting to pat their own backs.

      IMO, take over the show there, emediatly, please!!!

  13. 23:23-Current situation: From 19:54 hrs this afternoon there have been no earthquakes greater than magnitude 1.5. Se ha evacuado en la jornada de hoy al pueblo de La Restinga y se han cortado todos los accesos por carretera. Have been evacuated the day today in the village of La Restinga and have cut off all road access. Se ha prohibido navegar y bucear por aguas próximas a la Restinga. It has been forbidden to sail and dive in the waters near Restinga. El presidente del Gobierno y Paulino Rivero han mantenido esta tarde contactos para saber la situación. The Prime Minister and Paulino Rivero have maintained contacts this afternoon to see the situation. Los expertos señalan que son altas las probabilidades se la formación de una segunda erupción explosiva próxima a la Restinga, pero no peligrosa. Experts say the odds are high the formation of a second explosive eruption near the Restinga, but not dangerous. Los vecinos seguirán evacuados hasta nuevo aviso. Residents evacuated continue until further notice. También continuará cerrado el Túnel de Los Roquillos. Also continue to close the tunnel in Los Roquille. La Restinga está en alerta máxima y con el semaforo volcánico en Rojo para esa zona, continuando en nivel amarillo para el resto de la isla. La Restinga is on high alert and the volcanic red traffic light for that zone, continuing in yellow level for the rest of the island. No es posible concretar ni donde será la erupción ni cuando. It is not possible to specify where it will be an eruption or when. Pero pronto sabremos el desenlace. But soon we will know the outcome. Seguimos ampliando. We continue to expand.

    1. “23:23-Current situation: From 19:54 hrs this afternoon there have been no earthquakes greater than magnitude 1.5. Have been evacuated the day today in the village of La Restinga and have cut off all road access. It has been forbidden to sail and dive in the waters near Restinga. The Prime Minister and Paulino Rivero have maintained contacts this afternoon to see the situation. Experts say the odds are high the formation of a second explosive eruption near the Restinga, but not dangerous. Residents evacuated continue until further notice. Also continue to close the tunnel in Los Roquille. La Restinga is on high alert and the volcanic red traffic light for that zone, continuing in yellow level for the rest of the island. It is not possible to specify where it will be an eruption or when. But soon we will know the outcome.
      We continue to expand.”

      Sorry for the spannish/english mixitude!
      If they are continuing to expand they should eat less cake… 🙂

      1. I just saw this http://www.elnortedecastilla.es/v/20111012/espana/alerta-roja-evacuado-hierro-20111012.html (in spanish) 5 mins ago saying almost completely the opposite – predicting a further eruption closer to the coast at shallow depth – with magma containing lots of volatiles likely to have an eruptive plume of 40-50km high (due to the water making the eruption more explosive) – raining stuff down over a large area.

        Its from another CISC scientist – and it seems a bit fear mongering, but I guess it depends whether they are trying to tell people to stay calm, or tell people that they actually do need to go along with the evacuation plan what they tell the journalists at the time.

        Or perhaps they tell the balanced story explaining the two extremes of the story and the choice of story the journalist wants to sell – gets written and some stuff that doesn’t fit the tale gets left out.

      2. I doubt that the eruption plume is going to be 40 to 50 km high. That is almost double the high of the plume that was in Grímsfjall volcano eruption this spring. But that did top around 21 km high. That was the largest eruption in Grímsfjall volcano in about 140 years.

      3. Haha one is pooping his brains out. A column 40-50km high? Never ever, I’ll eat my shoe, -no-, I’ll put my mema on stake, betting that that will not happen. Yellowstone had a probable 50km plume, Tambora might have been 40km. But this potential plume will (if it will even be visible/exist) not exceed 10km.

  15. Jon & Co.
    AVCAN (Enrique at least) seem to be considering possibility of a surface event involving Tanganasoga volcano system (given the NNW-SSE trend in seismic activity since the start of the swarm)… Not necessarily an event at the Tanganasoga cone, but somewhere in the plumbing or rift/fault zone alignment…

    Some background info on Tanganasoga volcano:

    Location –
    http://www.facebook.com/photo.php?fbid=2204726116549&set=o.295435897139324&type=1&theater

    Blog with photo of cone –
    http://www.facebook.com/photo.php?fbid=2204726116549&set=o.295435897139324&type=1&theater

    Geology map of island –
    http://img835.imageshack.us/img835/2751/geology96.jpg

    PDF version of same map (on second page) –
    http://www.google.ie/url?sa=t&source=web&cd=23&ved=0CCwQFjACOBQ&url=http%3A%2F%2Fdigital.csic.es%2Fbitstream%2F10261%2F4431%2F2%2FGeological%2520maps%2520La%2520Palma%2520and%2520El%2520Hierro.pdf&rct=j&q=Tanganasoga%20volcano&ei=7bCUToiPEoSZhQe9i9GhBg&usg=AFQjCNEvAPNsUpOcMz7io1l5B4wunPACOA&cad=rja

    Geology and volcanology of the island of El Hierro (from Carracedo, J.C. et al. 2001. Geology and volcanology of La Palma and El Hierro, Western Canaries) –
    http://digital.csic.es/bitstream/10261/2343/2/volcan2.pdf

    Video of flyover of Tanganasoga landsscape –
    http://www.youtube.com/watch?v=RXBmh-qND_8

    Abstract of 2009 AGU meeting poster “Ankaramitic Lavas and Clinopyroxene Megacrysts From the Tanganasoga Volcano, El Hierro Island (Canary Archipelago)” –
    http://adsabs.harvard.edu/abs/2009AGUFM.V51A1662L

    1. Some good links Andy- I was sceptical given that all off the activity has centred in the South of the Island. However, checking out one of the papers you linked to, this volcano was the orginal that started the Island with the southern ridges more recent so may have the depeer structure – I’m guessing of course. The EQs now seem to be much deeper than earlier – who knows.

  16. I’ve been puzzling over the GPS data.
    http://www.ign.es/ign/resources/volcanologia/html/deformacion.html
    Most of the GPS data point ( I think – not an expert) to a marked movement of most of Hierro compared with its western end. The GPS show an accumulated separation of about 35mm between H103 (the western GPS site) and H102 to its east, which are maybe 10km apart. But it may not be H103 that has shifted.
    Frontera (against which H101 to 103 are referenced) has also moved closer to La Palma ( Mazo) and Gomera ( Alaj) and Tenerife by similar amount. To me that suggests that the western GPS station on Hierro H103 has moved a total of 35mm away from its neighbouring station H102. But that separation is due to the rest of Hierro including Frontera (and H102 and H103 with it) moving closer to the other islands.
    I conclude that the GPS data reflect a big shift of most of Hierro to the North West
    but the western end of Hierro staying stationary along with H103 on it.
    Interesting that this zone of maximum motion, between H103 and H102, is above the central focus of the deep EQs so beuatifully depicted in GeoLurking’s 3D displays.

    1. Interesting. Might help to explain the perpendicular nature of the EQs that Pieter has queried.

      1. Well it actually confirms what has been suggested. The deep earthquakes were caused by a magmatic intrusion. That’s one, second question, how will it find its way up? Magma does not neccesarily go straight up. I think in this case it follows fault planes formed by the three rifting structures, and the fault plane you can see in the earthquake pattern. is orientated from north to south. Over time it has moved some to the east, perfectly aligning it to the south axis of the island.

  18. correction:
    “…..big shift to the north east……”
    (Its late, brain fade)

  19. From http://www.gobcan.es/dgse/descargas/volcanes.pdf (Spanish to English)

    The island of El Hierro, is of volcanic nature. Volcanoes are the protagonists of our terrain and have been in our history. El Hierro is the youngest in geologic age, with just a million years old.

    Unlike the rest of the islands, which lie in a third phase of creation, El Hierro has continued over the first. When the magma broke the seabed, it created
    a gap in a “Y” for which she began pouring lava. The lava covered the coastal areas of southern and western the island, but also from the north. The various eruptions were expelling materials that were expanding island size of the building.

    El Hierro is the most densely (populated) volcanic island in the Canary Islands. There are over 500 open pit craters and a large number covered by recent lava flows. There are 70 caves and volcanic tubes labeled, highlighting the Cave of Don Justo, 6 kilometers in length.

    Historical eruptions in the Canaries (in the last 500 years) show that we fortunately with a similar to Hawaiian volcanism, where its population lives in
    daily with active volcanoes.
    Living with volcanoes has been part of our past, but also the present and the future of this alive island.

    1. No, thats it. I didn’t have a good starting angle so I just took a slice from somewhere on the southern ridge off to the deep ocean. That’s why I called it a representative slice.

      1. I meant that the area in the graphic is the area that my trace was for.

        I had a fairly busy day today, but did do some ruminating and put together my best guess for the location of the tremor source (lower on this thread).

        I’m pretty sure they want animated stuff, but right now I don’t know what I can add to the sequence to make it worth the while.

        (I’m open for ideas… other than having them appear on the plot in time sequence order, I haven’t mastered scripting to the program yet and haven’t had time to deal with it due the onset of the tremor)

  21. Tanganosoga would probably fit both with the GPS and with location of EQ events during the period of GPS motion – the central zone of GeoLurking’s plots. EQs during the past week have moved east ( and gone shallower) but have not contributed to GPS motion. So a location splitting H103 from H102 GPS stations would fit well- but where exactly are they?

  22. That fly-by was distressing – tarmac roads , traffic…
    When I was camped there in ’64 in the cloud forest the road was corrugated dirt, and no road up the escarpment….I suppose its progress.
    But great links, thanks.

  23. Tuesday
    11.10.2011 22:59:59 64.652 -16.713 3.1 km 2.7 90.03 4.8 km WNW of Kverkfjöll

    1. This was just before that one, low quality. Maybe a ghost?

      Tuesday
      11.10.2011 22:59:58 64.452 -16.449 18.5 km 2.2 37.91 22.1 km SSE of Kverkfjöll

      http://en.vedur.is/earthquakes-and-volcanism/earthquakes/vatnajokull/#view=table

      This from Mýrdalsjökull but low quality.

      Wednesday
      12.10.2011 00:03:42 63.687 -19.121 1.1 km 1.1 33.74 8.2 km NE of Goðabunga

      Useful to note this from IMO:

      A strong gale (more than 20m/s) is expected with strong gusts by mountains in southwest and west parts from tomorrow morning until after noon. Valid to 13.10.2011 00:00 More

  25. Geology map of El Hierro from above shows a candidate for an exit vent with recent scars at the top of the ridge called Mna Cueva del Guanche seen in the opening frames of the video fly by. This vent is on the outskirts of the recent events. It was formerly connected to the chamber. Everything else has ground cover.

  28. The Spanish news link posted by Jón, shows nothing new, except that they reaffirm their confidence in the preventive measures being taken and according to them, no explosive eruption will take place, except if the new eruption occurs at less than 200 km depth, albeit a phreatomagmatic explosion wouldn’t be as dangerous as, for instance, a Vesuvius eruption.
    OK.
    I would be gladly flying back to Rio’s usual summer landslides if I were there right now…
    Denise, nothing else from me, I am just astonished with the high level of discussion provided by this blog.
    Thanks everyone!

      1. Vince:
        Parabéns! Congratulations! This is a MUST for everyone interested not only in El Hierro, but also in Icelandic (effusive) volcanism. The footage on Tenague volcano reminds me so of Fimmvörduháls. Parabéns!
        Já tenho uma ótima leitura para o feriado de amanhã!
        Obrigadíssimo!

      2. @Diana – I thought “parabens” was reserved for happy birthday? I’m have said Beleza, muito bem and that kind of thing. 🙂

        @Vince that’s a really good collection of the info so far, lots of good images. A couple of the ones on page 2 – the maps from above with just the most near surface quakes are interesting. Muito obrigado 🙂

        @Anyone else might be worth a look even if you don’t speak portuguese 🙂

  29. Gracias, Renato, y ¡buenas noches! (I know it’s not Portuguese, but maybe close?) 🙂

      1. Thanks Vince, now I can say it in Portuguese! I actually know a fair amount of Spanish, and am getting a lot of practice with all of the El Hierro news.

        Renato once called Spanish and Portuguese “twin languages”, so I thought it might be reasonably close. I don’t generally trust Giggle but think that Portuguese would be muito interessante.

      2. Well, not really twins, the real story is very confusing to tell here. It’s a long history replete with violent wars and conquests 🙂

      3. Será um prazer visitá-los.
        Um professor universitáro de teatro cheio de alunos poderá dar conta de seguir tantos blogs sobre vulcões? 🙂
        I can hardly help with the translations, although methinks Giggle does a better job in Spanish than in Icelandic.
        I don’t know if there is such a Brazilian Forum, but I could check it for you.
        Thanks for the invitation.

      4. Sorry for the “twin languages”. But since I also speak some Spanish and both languages are very similar, I thought “twin” wouldn’t be that far from true.

  30. The other lurker yesterday 23:29 mentioned the Cueva de Don Justo, a cave / volcanic tube near La Rastinga. Here is some more information on it:
    http://myelhierro.com/en/cuevadonjusto.php

    CUEVA DE DON JUSTO

    Cueva de Don Justo is situated on the south-eastern part of El Hierro (El Lajial), in the direct neighbourhood of La Restinga, in municipio of El Pinar.

    This cave stretching over the slope of the hill of Montaña de Irama o de Prim (254 metres above sea level), on the lenght of 1360 metres and height of 135 metres. Its interior is a real labyrinth. The corridors, created as a result of prolonged volcano eruption, often crosses and intersects. In some places there are even eight parallel arranged tunnels. The whole underground passage has a total length of 6315 metres, what makes it the longest on El Hierro, the third longest on the Canary Islands and the 13th longest in the world (accoring to datas from 2005).

    Cueva de Don Justo is characterized by the high air humidity and one of the higher, of the all recorded in the Canaries caves, temperatures, which oscillate between 21 and 22 degrees. The cave’s fauna is very diverse. Here were discovered many species of troglobits – all of them endemic, and few of them occurs only in this cave.

    Owing to the protection of occuring species and the numerous acts of vandalism currently the entrance to the cave is prohibited. To visit it you’ll need a permission from the Cabildo de El Hierro in Valverde – but in principle it’s given only to the researchers and scientists.

  31. Okay… did a couple of hundred miles of driving today, and had time to think about the harmonic tremor.

    I had mentioned yesterday, that if we could localize the tremor, we might get a clue as to where whatever is going, is going on at. The problem is that seismometers use the P and S arrival times among a few stations to localize the quake, and a tremor doesn’t give you that… at least not in anything that is easily picked off.

    My idea was that since the tremor is now seen by a seismo gear on a couple of other islands, we might be able to cheat our way to a semi-intelligent clue/guess about where the tremor is at.

    Before I go into this, remember that this is not standard practice (as far as I know) and is not sanctioned by anyone or agency whatsoever.

    On top of that, there is a lot of room for error. This “outside the box” approach takes a little bit of thought from antenna beam forming theory and target localization using unconventional means.

    The first thing we need, is a feature in the spectral waveform that is common to all three stations. (CHIE is included, since that establishes our reference point).

    http://i54.tinypic.com/90x9o8.png

    Next, we establish a ratio between the arrival time of that feature at EGOM and EHIG (La Gomera and La Palma) The signal arrival ratios work out to 48.5% and 51.5% for those two stations.

    We then find a point between those two stations that fits that ratio, and then cut a bearing to CHIE. Theoretically, any signal along that line will generate those arrival ratios at EGOM and EHIG.

    Since CHIE is the starting reference point, we can’t really use the travel times from there to the other two stations. I tried that and the range to the source can’t be nailed down. That’s why I used the arrival offset ratios to get the midpoint.

    http://i56.tinypic.com/10fdnoo.png

    Logically, the signal is going to be somewhere SW of CHIE since that is where the quake activity is at. I’ve thrown in some of the quakes on the 10th of October for reference.

    http://i52.tinypic.com/1195rsy.png

    My guess is that the source of the tremor is somewhere along that line, southwest of CHIE. (This also fits the Eastern area of Jons southern ellipse.)

    I’m not saying it right… but it’s the best guess I can offer.

    1. Additionally… that is just the estimate of the location of that particular glitch in the waveforms. It could actually be a structure several kilometers long or deep

    2. Good thinking. It is a question if you can use the harmonic tremors nature to locate the source within margin or error (+- 2 km) by refining the time difference between stations.

      I think that you can do that if you focus on the 2Hz oscillation of the harmonic tremor. As the magma signal is the most clear at that frequency.

      1. The hard part was finding a common feature. If you can identify a nice clean common artifact I can probably can get it tighter, but it’s still gonna be just a guess.

        I’m limited by the size of a pixel. For this image set, a single pixel is about 5.03 seconds.

        I don’t think I can get depth off it though. Maybe with a third non CHIE station it’s doable. (CHIE is by starting reference point for time offsets)

      2. The problem with “common” feature in harmonic tremor is that there isn’t any. But if you use a segment of 5 min then you should be able to do a decent location estimate.

        That is at least how my brain does this. As I am no good with graphics programs and to edit pictures. But I need to learn it clearly.

      3. With the raw waveform… that might be doable.

        The “common” feature that I looked for was an abrupt drop in power at CHIE that I could identify in the other two stations by them having the same sequence.

        Ideally, multiple events like this would be needed to refine the guess. As you have mentioned though there isn’t really anything common about them.

        Note to all; Don’t worry about trying to find me the raw waveform, I don’t have the kind of gear needed to pull that off.

      4. You don’t need the raw wave form I think. In the spectrum or the images there are features that can be used.

        It is also worth noticing that this type of harmonic tremor does not happen when gas release happens. There is a eruption there and it is in full power right now. But I fear that it might increase its strength soon. Given the pattern in the harmonic tremor.

      5. Tremor and gas- I can buy that. I don’t have a place for the gas to go and that would have to be an awful lot of gas to make that much noise.

        I don’t think they have that many legumes on the island. So, I stand corrected.

      6. 5 seconds, roughly 5 * 5 km then. Still actually very good result due to data-format.
        As Lurking said, with raw-data and a high time-frame resolution, and a wave-form recognition program you would still be lucky to get better than 100 x 100 metres at frequencies between 1 – 2 Hz with a probable inexactitude of the instruments.

        Good thinking Lurker! Very good. I would say you are pretty much as close as is possible.

      7. Forgot to say, the real value of it is that we due to Lurker know a heck of a lot of where things are not happening.
        If you could now get a signal that is clear enough from a yet another station you should be getting yet another line so that you can triangulate a bit… 🙂
        Ahem… Could you plot that? 🙂

    3. Good morning!
      What a shame I have to be disturbed by a professional activity and a private life. 🙂 This is just so cool reflecting and thinking. Anyone who can take time to really contribute and put some serious work in is lucky to participate at something that feel like making sense.

  32. What analysis, other than pure guesswork, did you use to predict the location of the eruption, then?

    I think you should start an appeal for a 1st class ticket to the Canaries. Whilst you’re at it, start a campaign for a second home there.

    1. Is that at me or Jon?

      For me, my initial guestimate was based off of something I call a “stack” of quakes. In the rotating 3D and 4D plots, you can see a space grouping of quakes that snakes their way up to the surface near the southern ridge. On top of that “stack” is a cluster of quakes. Viewed from the top, I picked the centroid of that group, leaning towards the area where they were tighter.

      Is it a guess? Yes. Fully. I’m not saying that it will erupt there, just that it is a pretty good candidate for it.

      I based that method over watching the Eyjafjallajökull sequence. Grímsvötn did a similar thing though the quakes and eruption were months apart.

      This latest thing I did on the tremor isn’t predicting where it will erupt, it’s just an attempt to figure out roughly where the tremor is located. (Again with the opinion) My opinion is that the tremor is from degassing. As the magma moves upwards it’s coming from a high pressure area and anything in solution that is gaseous in nature, will come out of solution. Sort of like popping the top on a carbonated soft drink. That hiss of the bubbles forming likely has the same mechanics of the tremor generation.

      Find that and you find the magma.

  33. About PSD, see graph on the right side of the spectral image at http://www.ign.es/ign/head/volcaSenalesAnterioresDia.do?nombreFichero=CHIE_2011-10-12&ver=s&estacion=CHIE&Anio=2011&Mes=10&Dia=12&tipo=2n .
    Some information from
    http://www.cygres.com/OcnPageE/Glosry/Spec.html (this website gives much more information):

    “What is power spectral density function?

    Power spectral density function (PSD) shows the strength of the variations(energy) as a function of frequency. In other words, it shows at which frequencies variations are strong and at which frequencies variations are weak. The unit of PSD is energy per frequency(width) and you can obtain energy within a specific frequency range by integrating PSD within that frequency range. Computation of PSD is done directly by the method called FFT or computing autocorrelation function and then transforming it.”

    Energy seems to move slightly to a higher frequency:
    The PSD graph now (wednesday morning) peaks at ~ 1,25 Hz. Yesterday it was a little lower and monday it ended at ~ 1 Hz.

    2. Nice explanation. Thanks. If I understand you this would allow finding the spot with the highest energy in the system, but the difficulty for the next phase is to know where and how pathways to the surface will form. And this doesn’t necessarily have to be where the energy is highest. Much more, it depends of which weaknesses in the underground strukture fill open ways first, and from there how fissuration cas evolve. And the jump from one weak part of the structure to the other will not have to be linear, but rather chaotic as the whole system changes with every step of it’s evolution.

  34. @ Jimmy James
    Spotted marks olongside the GPS stations on your map of Hierro: the university of Nagoya is collaborating with Grafcan and has more GPS data here:
    http://www.seis.nagoya-u.ac.jp/sagiya/Sagiyas_Page/Canary.html
    – including elevation.
    Still cant find good map locating thier six GPS stations, and dont think they correspond to H 101-3. So need time to digest their data
    Iceland has the march on Spain – vastly better organised.
    Peter

    1. The coordinates for the inst. Location seem to be at the top of the data summary called ‘ neu ‘ First sett is based on some system like our North American Datem ( horiz.) , then Lat, long are given in decimal deg,

  35. Jon, since when (time) would you say the tremor there clearly is related to an eruption?

    1. I did wonder if the various altitudes of the seismographs are quite seperated

      and it looks like the max difference might be about 1000m

      whether it was possible to do the “Lurking semblance” calculation on the vertical line to get a depth determination in the same way that it gave a direction earlier.

      Then perhaps following the semblance line of direction (for a particular wave feature) at that inclination one might be able to ‘discount’ any section of the line that was further north than point at which the estimated depth determination was above the altitude of the terrain?

      or is that (as I’m beginning to suspect whilst writing this) not possible ?

  38. Got friends leaving for Tenerife this week, I’ve told them to be careful. I’m quite envious to be honest, from a volcanic point of view of course.. nothing to do with 90’f sunny weather, really..

    1. Yesterday, coffee break, a colleague of mine tells us “I’m so jalous, a friend of mine is leaving for Frontera this sunday.” I just told him “no, he wont.”
      “Why not?”
      “They will soon evacuate the island as everything shows we’re heading for an eruption…”
      “But the travel agency didn’t tell him anything, so I don’t think you’re right about this eruption…”
      Well, yesyes, whatever… I love “people”. I’m not sure the colleague understood why I couldn’t stop smiling for the rest of the coffee-break. Anyway I guess they think geologists are weirdos since Eyjaf’s eruption. “Oh my god, the aeroports are closed…” – “You mean we can’t use EasyJet for 3 days – hm, well whaaaaat a catastrophy just came over mankind… Wait for a fatter volcano to burp…” Probably geoholics really are weird, they must be right – exept for the probability of making holiday in Frontera this sunday… 🙂

      1. Had that before from people … not just for geological things but weather / disease etc . “but they wouldn’t let us book it if it was dangerous..” .. LOL…..

        In the UK the earthquakes +/- subsequent eruption have not hit the radar of the TV or radio … odd article in some newspapers but most would not have a clue. press here tends to be very parochial unless affecting brits … or americans … but europe??? never!

    2. Or is this almost deafening silence in the UK to protect the tourist industry?

      The Daily Mail did run a story of the earlier evacuation on 29 September but was accused of scaremongering. Unusually for the Daily Mail, the story was straight factual reporting.

      4. Thanks! So the swarm of EQs in September lay right under the zone of maximum spreading, between Sabinosa and Frontera.
        Not sure if I’d want to be in either place right now, al though the small number of EQs are still deep.

      5. This uplift area seems to fit relatively well with the location of the Tananasoga volcano, as on the map someone posted above.

    1. Only 7 quakes all day yesterday, yet 5 recorded already today. looks like things could be picking up?

      1. They are still too deep.
        IMHO, the big questions are:
        * Are there shallower quakes taking place disguised in the thick band of harmonic tremor?
        * Do we really need the shallower quakes to get magma sneaking through the surface, as Pieter points out?
        * If we don’t and we do have an ongoing submarine eruption, will it be enough to release the pressure?
        * Could this spreading behaviour mentioned by Cobbold respond for a weakness of the deeper swarm zone as to let magma fill in and erupt through that area?

      2. Thanks for pointing this out – in all the tremors I had given up looking to see if there had been any actual earthquakes…. some people earlier were suggesting that there might be some more before any signs of further eruption

    1. The guy there thinks the deep quakes could be because the reservoir is still having big influx from below.
      Sounds somehow ok to me. I’m still not sure what to think of the strong tremor. Understand Jon an Lurking when they say that it hardly can be “only” degassing, but I’m not so convinced that it has to be an eruption. Why couldn’it it be the signature of a high influx of magma in the reservoir? I agree that this means we’re filling this thing up like crazy…

      1. I suppose the puzzle is that there could be more than one event in the lead up to an eruption: de-gassing from a fumerole and movement from the magma. Both events produce tremors.

        My uneducated guess is that the larger tremors are produced by magma movement (pressure fracturing rock); and the smaller ones are more likely to be associated with de-gassing and / or magma movement. De-gassing contributing towards the smaller tremors because as other commentors have pointed out, we have not seen a lot of gas bubbles.

        Given the potential complexity of the magma reservoir, the magma may be in more than one location or widespread, which would add to the compexities of trying to predict an eruption site(s). Especially as there is little known history of eruptions at El Hierro.

        Lurking’s excellent work, and that of others, shows just how difficult it is to predict an eruption.

        If I were the local authorities, I would be playing it very safe now.

    1. There has been alot of EQ activity in the Mediterranean area recently, presumably along the plate edges. This EQ could be an extension of that.

  43. There is probably quite a lot of quaking hiding in that harmonic Without wave-form recognition analyzis we will never be able to see them.
    To steal a line from Lurking, if we only had raw data access I could sample the harmonic tremor, remove that from the sound file, and then we would have quakes and unknown left. Then I need a variation of quakes to compare with (have those) and then all suspected quakes would pop out, then I would hand check them, and every time the adaptive recognition algorithm would improve it’s ability to find quakes untill it automatically can disregard the unknowns. (Think Jóns Helicorder here during weekends, beer keggs bouncing is an unknown, doors slamming, so forth).

      1. It does, that is how we found subs outside the port of Amsterdam. And if you can do that a quake is piece of cake.
        I am a bit rusty at this, but I created that location algorithm, so… 🙂

      3. One of these moments I’d like to be the master of the world to give you the data…

  44. Good Morning Jon et Al.
    @Lurking. I am watching this discussion with awe. I cannot join in as I am too much a novice. It is humbling to watch Masters at work.
    OK so some people on this blog may not have formal qualifications in Earth sciences but by golly! They certainly have excellent brains that think laterally, vertically and evrey which way!
    For those people who are joining us just recently because of the events at El Hierro.
    Jon, Lurking, GeoLoco, Carl le Strange and many others are all professionals in their own rights. They may not have paper qualifications in Vulcanology but as true scientists they question, and seek answers by using their wealth of knowledge from other fields of science.
    Please remember that it is only in the last 20 or so years that the monitoring of Volcanoes has been becoming more of an exact science with the introduction of new technology. Animated diagrams such as Lurking so cleverly produces are only possible by the use of Computer programs. We may all be able to now understand a little more about how volcanoes behave but, as we cannot compare like data to past erutions, we can still as yet, only observe , learn, and record.
    I ask of the media especially who may read this Blog….
    ” Please give credit and mention if you use materials from these pages. Also a small donation would be of enormous help to Jon, who is setting up new equipment for the monitoring of Katla volcano in Iceland. Jon is a student and amateur Volcanologist, but don’t let the word amateur fool you!
    His Blog, THIS blog, is read by professional volcanologists around the world , so I assure you here you will find only scientific discussion, (Along with some friendly banter ). You will not find Scare Mongering, You will not find sensationalism. You will find ideas discussed and often disproved by the use of logical reasoning.
    So use and enjoy but please give credit where credit is due. Thank you.

    OK I will put away my soap box and go for my third coffee of the morning and check out Katla and friends or they will start feeling ignored!

    2. Here here and well said, Diana! I have been reading this blog for months and months, and I have learned so much, one day I may pluck up the courage to comment too!

      Thanks Jon, Monsieur Le Strange, GeoLoco and the King of Lur for your valuable, wonderful knowledge. I have had many a late night getting cleverer from your teachings *Nods heads in respectful way*

    3. A special hooray for the friendly banter! Makes life worth being lived. 🙂
      Oh Di, I see a long haired beauty coming out of her shower, putting away her soap, taking a light towel to cover a part of her nudity and walk to the kitchen where a cup of coffee delicately steams while waiting to be drunk… Wonderful pictures generated while consuming this blog. I officially declare you our muse.
      Had to be, I’m the bubbly one in the club. 😉

      2. Oh My Geo!
        Errrrmmmm! Got to be honest! Short hair……
        For the rest of your dream I would not be so cruel as to shatter your illusions.

        (…. Goes off to iron her thermal underwear and clean the mud off her wellington boots…..)

  45. It is hard to point out but in the spectrogram there are traces of micreseismicity if you look close enough. Not a good tool at all but it does indicate that smaller quakes do take place. In the graph there are some which are visible (vertical yellow).

    http://www.ign.es/ign/head/volcaSenalesDiasAnterioresHora.do?nombreFichero=CHIE_2011-10-12_05-06&estacion=CHIE&Anio=2011&Mes=10&Dia=12&tipo=2n&hora=05-06

    Hard as hell to see but there are 20 or so which looks like smaller mb1.0-mb1.5-ish..

      3. The more interesting thing in my opinion is that you can clearly see the “redish” goint “upwards” (forgive the enormous simplification). Let it fill the line over 7 – mmmmmh…

  46. NOTE AVCAN 255 – EARTHQUAKE VOLCANIC SWARM— EL HIERRO ISLAND – 12 OCTOBER 2011-11:00 h peninsular – Seismic activity remains high, with few earthquakes located and continuuous strong harmonic tremor signal since 4:18 pm yesterday still growing in amplitude and force. Moreover, it is lasting too long. The magnitude of the earthquakes are between 2.4 and 1.4. New earthquakes, 5. Depths to 10, 18, ​​18, 20 and 23km. The day before yesterday 31. Yesterday 8. Now go 5. A total of 10,017 earthquakes are located in El Hierro by IGN from 9:00 am of July 19, 2011 (Enrique).

  47. At Lurking…
    Doppler shift obviously.
    We are seeing doppler shift of course! I am stupid! I should of course have spotted that!
    The doppler shift components should vectored in, it should be consistand over time (visually if it is going straight for the station on El Hierro, if it changes visually it should be veering off from the location of the station, so far it is not. So it is heading towards something like five to ten degrees to either side of the station (not calculated, no time today, but a good guesstimate.) As it gets closer it should change if it is going to either side.
    So…
    It should than be possible to cross reference this to your plot to get a rough Y component to vector the location of where it is going to end up.

    I am stupid!

    2. “Doppler shift forgetting” has cost me half a point at a physics exam in the faaaar away past… Let’s officially name it a bitch! 🙂
      Lurking take 5°, it’s really not that far.

  49. Feeling lousy (comparable to Hengill!!) and off Canaries topic; has anyone been to the top of Herdubreid, ‘cos Google earth (apart from asking ‘do you mean Iceland near Europe’) shows a water filled-ish-crater and a deep depression to the north – which is the true vent location please?

  50. I’ve got a question:

    If the Volcanic Tremor is related to Magma-Degassing, possible submarine degassing, wouldn’t all this gas, an if you look at the tremor signals a lot of gas, cause some kind of gasbubbles which could be measured?

    In my Brain I have the image of a Bottle of minealwater. If there is a small particle/uneaven surface in the inner side of the bottle, the gas (CO2) will collect on this spot an rise, similiar to a chain of pearls.

    So if there is massive degassing, wouldn’t this create some kind of expression on the sea, like bubbles or a higher concentration of volcanic gasses on the surface of the sea above the area of degassing, which then could be measured (via satellite-imagery which measure atmospheric gasses?)

    any ideas?

    thanks and greetings
    Stefan

    PS. Diana: You’ve said/written wonderfully what i think would be the least the Media should do when they take content created from the users of this blog!

    1. Gasses are normaly soluble in water, especially under high pressure… So, most of it would be stuck in the water killing yer fishes.
      But yes, some come to the surface.
      There has been pictures of gas surfacing. Pure nice bubbles without discoloration. That lack of discoloration is telltale, there should have been crap following up in the gas-bubbles if there had been an eruption. There seems to be none.

      2. Absolutely same here. Could of course, we like to be “politically correct”, but I just can’t “feel” it…

      3. To be politicaly correct, I “feel” that by now we should see something brown and smelly coming out of the orifice, and some of that should be “floaters”.
        At least one helicopter should have seen traces of the “products” by now.
        I think the volcano is still just sitting on the stool contemplating life with a newspaper in hand, this is after all a male volcano, and males take their time when sitting on the throne.

      4. nicely said Carl le Strange!

        It seems to me, that there is quite a riddle here, which awaits beeing solved. ; )

    2. Even if not exactly put the way you point at it, that’s part of what makes me wonder/doubt about the strong tremor being mainly related to something “eruptive” s.l. If there was massive “outflux” of whatever related to such a stong tremor, we should have some perceptible consequences of whatever the kind.

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