The (ash) history of Iceland, in my backyard – Part I

This week I was lucky enough to have a recently dug square hole (10m per 10m, about 2 meter deep) some 200 meters from my house in Southwest Iceland.

Needless to say I spend the past bright summer evenings of Iceland inside this hole, which has nothing else but dirt and rocks. To us, volcano lovers, having such a hole in a volcanic land is like finding a mine of gold!

The soil shows many layers of colored material, which is nothing but the ash that has fallen from the many eruptions that happened in Icelandic history. This is a science called tephrachronology and it became my newest hobby.

Photograph and copyright belonging to Irpsit, used on explicit permission by Volcano Café. An excavation near home. And I stayed until late night to look at its strange layers.

When an eruption happens (if it’s the explosive type) the ash usually drifts according to local winds. In Iceland, the wind can blow from every direction depending on the kind of weather. This results in ash being deposited in a space-specific way for every different eruption.

A large eruption such as Askja in 1875 (VEI5) blew almost entirely to the northeast (so since I live to the southwest, I cannot find any Askja ash). In practice this means that the absense of a famous eruption does not mean it did not happen, just that the ash blew somewhere else. Likewise, a smaller eruption can deposit plentiful ash if the same wind keeps blowing in one direction (example of Eyjafjallajökull blowing southwards towards Europe in 2010).

In one single spot, the ash from different volcanoes accumulates over time, giving a profile of layers, that correspond to a time orderly of eruptions of different volcanoes. Usually, famous eruptions such Vatnaöldur in 870 (when the settlers arrived) can be used as markers for less known eruptions. The identity of a volcano can be roughly identified by looking at its color. We know that few volcanoes in Iceland produce white tephra, only Hekla and the rarer eruptions of Öræfajökull and Askja. Grimsvötn often produces brown ash, while Katla or Eyjafjallajökull black ash.

But enough of introductions! Let’s go for the real thing.

Photograph and copyright belonging to Irpsit, used on explicit permission by Volcano Café. The history of many eruptions is recurded as different ash layers.

The walls from the hole reveal, at instant glansing, two bright WHITE layers (figure 1). At close inspection, the upper white layer (at 25cm) is actually a double of two light colored layers, while the lower at (49 cm) is a single thick layer. Obviously these layers seem to come from Hekla.

The Hekla 3 white layer
To confirm whether or not these are from Hekla, there is a scientific paper of a soil profile done very near to where I live, around Grimsnes volcano (just 5km from where I live). They found only one large white layer at 50cm which corresponds to the largest eruption of Hekla during Holocene, the Hekla 3 eruption (a VEI5+) of 1000 BC. This is probably our second and largest layer.

Picture taken from Wikimedia Commons. Hekla is the source of much white ash in Iceland (as observe from the deposits on its flanks).

So, imagine, an eruption that deposited a layer of about 4cm thick ash here. That is pretty astonishing considering that a normal Hekla eruption barely deposits ash here (I am about 50km from it). This euption resulted in a 18 year climate change in Europe, observed in tree rings. It should have been one big huge eruption.

Now, if we look at the top white double layer, that is surrounded up and down by two thick DARK bands. These are actually a pinkish brown. Both are about 3cm thick ash (impressive too), the lower band is especially large at some spots.
The two dark Bardarbunga ash bands
According to other studies (and to Inge B), and also my conclusion, these are both the Veidivotn ash (1477) and the Vatnaöldur ash (870 AC), known as Settlement Ash (because it happen around the arrival of the vikings to Iceland). At least the Vatnaöldur ash is widepread reported everywhere in Southwest Iceland. Furthermore both have orange colored deposits underneath (actually light pink in Veidivotn ash, and bright orange in Vatnaöldur ash) which is expected. Both eruptions started with rhyolite ash from Torfajokull followed by the greyish/brown color of Bardarbunga fissures. The Torfajokull ash in 1477 was erupted from Brennisteinsalda, which is a mountain very colorful but mostly pink and orange.

Brennisteinsalda is the volcanic cone that erupted some colorfull rhyolite in 1477 (within Torfajökull).

The “double” white band of Hekla 1104 and 1341
If these are correct (I don’t confirm they are), then there are 2 white tephra eruptions in between. It’s easy to ascribe one to Hekla in 1104 (the largest eruption of Hekla since settlement (and second largest of all volcanoes), a very destructive one, but the ash during that one, was reported to go mostly northwards). The other one could either be the eruptions of Hekla in 1300 or 1341 (both with heavy ash) or less likely the 1362 eruption of Öræfajökull, which was the largest eruption of all, since settlement! Yes, larger (in tephra and intensity) than all Katla eruptions, Laki, Veidivotn, Askja or Hekla. Few of you know that Öræfajökull is a mamoth volcano, the largest in Iceland (and tallest).

However, I do think that this more recent white layer, was most likely the 1341 eruption. In 1300 the ash blew mostly northwards resulting in a famine, but in 1341 it blew westwards, and quite far away (towards Akranes). In 1362, the ash of Öræfajökull blew mostly to the southeast, opposite of where I am (and I know little ash felt to the west, in Vík – information from Skaftafell national park).

There is so much I write in a second part. All the minor layers in between (that you only see in close-ups) and all the broad bands below Hekla 3. Until then, let’s us discuss what we have so far.

IRPSIT

593 thoughts on “The (ash) history of Iceland, in my backyard – Part I

  1. I will put this in here instead.

    I have received an email from Erik Klemetti at Eruptions.
    He is kindly asking everyone who is having a problem with Disqus to contact them directly via the link below. There not anything more he can do about things apparantly.
    Personally I find Disqus to be a despicable data-kraken. But I know that many of you would like to be able to get back online at Eriks place and comment there. And let me state that my opinion about Erik is equally high as my opinion about Disqus is low. Just so nobody thinks I am beating up on Erik, I am decidedly not doing that.

    In many ways this entire blog would never have existed if he had stayed in a more user friendly environment…

    http://www.wired.com/wiredscience/2012/07/support-for-your-commenting-issues/

    • Same problem as always…. either you are a member of Facebook or Twitter or Google or Disqus or you are not allowed to send anything. Erik wont get any responses he would like to have this way.

      • Could you please leave Eriks email here. I will contact him and tell him that only the users he already had over the last year, can answer this call.

          • You can only leave a comment if you are a member of facebook google or twitter!! So all people like me who have neither are not even able to leave a comment.

          • I know, I am not either able to leave a comment there.
            So, for me it means that I will never be able to get online again at Eriks place.
            But, if that is the prefered way of not getting any feedback, then I will leave it at that.
            Personally I would prefer to see Erik move somewhere else, or perhaps maybe not since every move have been for the worse.

  2. OT but hope this is factual !!

    The big thaw: NASA scientists stunned as satellite pictures show ‘unprecedented’ melting of Greenland’s ice sheet .Three independent satellites find that almost the entire ice cover has seen melting at the surface this month
    Melting has spread rapidly, from affecting 40 per cent of the ice sheet to 97 per cent within a week
    It comes as Greenland sees unusual ‘heat dome’ weather patterns

    Read more: http://www.dailymail.co.uk/sciencetech/article-2178540/NASA-scientists-stunned-satellite-pictures-unprecedented-melting-Greenlands-ice-sheet.html#ixzz21dgVxrMx

    • Why would it not be factual?
      I am not surprised, but one should keep in mind that this is well withing 100-year weather extremes. One should not holler hell in the hole for a once occurance.

      As I time after time say without anyone listening. Weather changes are tracked globally over time, not due to single observations, nor by looking at the local weather (especially if you live closer to the equator).

      • Because this paper has been called the dailyfail many times so I just hoped it was factual and not a load of tripe.

        • I never read the Daily Fail thingamabit. I read the actual JPL report.
          http://www.jpl.nasa.gov/news/news.cfm?release=2012-217

          What is says in brief is that the surface of the Greenland ice sheet is melting at a larger percentage of area then JPL has seen before. One should though not that this is since the late eighties.
          I still that this is a statistical quirk and nothing to bother with, global temperatures can only be judged over time and if you use measuring points from the entire planet. Nothing else. Local weather is only interesting if you are there, not for science really.

    • We don’t know that this is an unpresedented melting as we have not had the satellite technology for long enough to know what the long term weather cycles are and Greenland does not have a big population

      Wonder if these heat domes have been what pushed the Jet Stream so far south this summer?

      Can the topography of what has been lurking under the ice-cap be seen now?

    • Funny thing about the source paper.

      They state in there that there is a 150 year cycle and that this melt is right on schedule.

      How you get “unprecedented” out of that would probably make for a very interesting story.

      • Well, I actually read about this in Slovenian and Swedish news (which are serious and not daily-fail style) and they BOTH mentioned that this is “on time” for the 150 cycle. No mention of unprecedented anywhere!

    • And since the fail had taken a paper and twisted it a bit… I’ll take some data and throw a trend line on it.

      This isn’t ice, and it’s not the glacier. It’s the snow cover. Snow is what eventually becomes ice… and the accumulation of it become the glacier.

      You tell me which way things are going.

      • Lurking, you are interpreting it wrong since you are not familiar with cold climates.

        Snow is actually the result of warmer climates when you are in the extreme north. As it get’s warmer here the heat creates more water vapour in the air that falls as rain in the summer, and snow in the winter. As temperatures here has risen so has the snow, all according to the models.
        What you should do is take snow fall and pair it of with melt rate.

        Let us say (fictive numbers throughout excercise) that we before had 1 meter of snow falling, and 1 meter of melt across the year. On a cold summer the melting would be less acreating ice, on a warm summer the opposite. Why the summers? Well, surprisingly summer temperatures are fairly not increasing here. It is winter cold that has diminished around ten degrees around the globe at my latitude.

        Now comes the fun. Nowadays we do not get 1 meter of snow, we get 1,5 meters of snow. 0.75 of this melts DURING winter. Bummer, that leaves to little for the summers to melt of, so the raw ice comes out to quickly, and then that one starts to melt.
        This is actually what has been happening during the last 20 winters, fast and rapid increase in winter temperatures in the far north.

        So, cause and effect was wrong on this one. Guess why we are buzy as bees fortyfying hydropower dams lhere in Sweden? We are getting much more water on our heads now than 20 years ago. And the models are sofar spot on. (I know, I am talking local weather here), and the same is being done in Russia and Canada, for the same reasons.

        • Even if the amount of snow is a product of more moisture, the fact is that each year the temperature rises enough to generate melt. That trend line based off of how far it melts back each year… and at that rate, (should it continue) there will be little to no summer melt in the future… despite how the snow got there.

          • Today’s news is nothing special.

            This is not 97% of melting, it is melting occuring in 97% of Greenland ice surface. But that is a normal situation at the end of summer, the only thing is that is that holding a bit longer than usual (and over a wider area) now in 2012.

            This is melting of the top few cms of a 3km thick ice sheet.

            This also happens in Iceland. Vatnajokull is melting at its top (when day temps go above zero) and mostly on its edges. As the edges melt, the melting speeds up inside.

            By some estimates, and assuming current rate does not stop (a big if), Vatnajokull will then disappear by 2300. By 2080 (when some of us are still around), Vatnajokull will be nearly diviving in two halves, one to the south, another to the north.

            Just to finish, about 1000 years ago, Vatnajokull was shorter than what it is today, but not by a big difference. And it might have been much smaller about 5000 years ago, at the peak of Holocene warmth (warmer than today). The big question now is whether warming will continue (due to manmade forcing), or by any other reason (low solar output or feedback mechanisms) the warming eventually reverts to a new cool period.

          • About that warming thing. I wouldn’t get my hopes up.

            Every time real, objective looks are made at the available data, it tends to show tendencies that are in clear opposition to what the models and politically connected wish it to say.

            I’ve been farting around with Eureqa’s Formulize on the NGRIP temperature data back to 40,000 ybp, and each mathematical model that it spits out points in different directions. I had one that said we are gonna freeze our collective asses off in about 100 years, and another that said that you will be able to collect rock specimens while wearing a thong in Greenland in 500 years.

            The general trend is a slow decline in temps there.

    • And in the real world that is not a part of AVCAN the East, North and Uplift components are remarkably stable and show nothing exciting more than that the magma has happily stabilized in it’s position.

      BREAKING NEWS!!!
      AVCAN has found a volcano in a bathtub. It showed itself through water draining out since the plug was removed.

        • You are quite correct…
          Sorry on this occation AVCAN.

          But, the thing about values being stable is still vallid. No changes, at all, anywhere. Trendlines… 🙂

  3. Irpsit,
    I made my diploma thesis in sedimentology. I just love what you can get out of analyzing stone-layers. When I’m at the beach you see me digging a trench to look at the recent history of the site. Might it be for some weeks or month, and if I’m lucky we go much further back in time.
    The way sediments are deposited, structure details, their content… This all tells you so much about the regions and earth’s history. Superb.
    Simply loved that post.

    • Oh my…
      I just saw you wearing sunglasses, your huge smile, small swim-trunks, hard-hat, and the twin holstered hammers… …digging away at a beach.

      • Suggestion: replace the swim-trunks by a leather string-panty. The image should now be bad enough to stick in your brain for hours…
        Trying to become a master of inception… No matter the price, even if it’s my own dignity… A man has to do what to do a man has… Ehm, yep, wellwell, you know what I mean…

        • And now as the Ladies have the image of leather-thonged Swizz man with hard-hat and sunglasses, hammers and huge smile… I have seen an image… Ladies, you have missed something.
          And on the matter of geologists, Alan… 😉

    • <<<<<<<< makes a note not to spread her beach towel next to GeoLoco on the beach…..The last thing I want to see when I am relaxing is a manic, randy, geologist digging a trench that keeps filling up with sea water……
      My children used to do that and they never did understand why it kept filling with water when the tide was out. 😀

      • Yeah well it depends on why exactly you build your trench. Then you chose the spot carefully. Of course it is very interesting indeed to study erosion if you make it where you can later build a channel to the sea and look how the water processes the morphology at that very local scale… Especially for the kids.
        But one should always be aware of the dangers that go with trenching. If the hole is of decent proportions, it can really be something to think of. A kid in a 1m deep whole that collapses is a very, very bad situation. Just meant to add this as we’re funny people but also use our brains when it counts…

        • Another danger for kids is if they successfully build a lake on the beach by damming the residual drainage from the outgoing tide and the dam breaks. People sitting below the dam don’t take too kindly to being caught in the outflow…..

    • Great!!
      This has got to become my new hobbie now.
      If you are more knowledgeable than me on these matters, please really feel free to challenge the identity of the layers I assign. I am pretty confident regarding Hekla 3 and the Vatnaoldur (Settlement Ash) and Veidivotn layers. But not so confident for all the other layers.

      Basically, we do know in Iceland, that usually (not always) an Icelandic volcano tends to erupt a specific ash color (Hekla/Askja/Oraefajokull: white, Katla/Eyjafjallajokull: grey/blackish; Grimsvotn: brownish; Torfajokull: pinkish rhyolite). On Hekla there is a pretty detailed history of its eruptions (even as referring to where the ash went), but many Vatnajokull eruptions are not confirmed. And I have no idea of what ash might other volcanoes erupt, if any (Hengill, Langjokull, Vatnsfjoll, Bardarbunga….)

  4. Very good post, Irpsit! Would be great if Birgit could make microscope pictures of each layer..
    (sorry, but I’m so terribly greedy!)

  5. It always humbles me to read these reader contributions, the truly vast amount of knowledge available to this community they display. There is science everywhere, even in a hole in your garden and like GeoLoco toddling at the beach, we should never forget that. Thank you Irpsit for these insighs!

    • This is science, not toddling!!! 🙂

      Oh, and as you seem as horny as I am for some real action – might the 6.5 at Solomon Islands be the start of a pole shift? 🙂 Pfffouahahahaaaaa…

      • Pole shift: Can refer to either the migration of the boundaries of the Polish state or the extensive relocation of the ethnic population referred to as Poles performed by Germany and the U.d.S.S.R during the years 1939-46. I very much doubt an earthquake at the Solomons could have such an effect, m’dear.

  6. Thanks for a brilliant post, Irpsit. I can just imagine you in that hole – never wanting to leave!!

    I wish I could add something of use, but I can’t, so I’ll re-read it and wait anxiously for the next instalment!

    • Yep, as soon as there’s a hole there’s something starting to fill it. As said so many times in here, nature hates voids. That’s the reason for volcanic activity, and might even be the reason for marriage (needs some large interpretation of “the whole thing”).
      Ehm. did I actually write that? Yes. So what. Life is too short for regrets, isn’t it…

      • That’s the nature, and we are a part of this. But it costs a bag of money to fulfill our (The Man) needs. So this is it. (Yes that’s right, I’ my girlfriend doesn’t read this)

        • Bear with me, as I have a dry sense of humor, I often can’t resist to comment. I hope I’m not interfering you too much, and I will say I appreciate the high level of knowledge present, as the science of the nature is in my field of interest. 🙂

          • We seem to share that “problem”. I can’t resist fooling around. Until now it seems people tolerate us. It’s comments and views. Good for the statistics… 🙂

          • And again that session thing that regularly makes me jump to my “serious” Shadow-profile.
            No need to hide anything. It’s me, Loco. Just in case someone wonders…

          • Ah Shadow aka Loco, good to see you are struggling with the same as me. But I’ve never think about to make any shadows, that may be my swaddle. Being serious in combination to not write ridiculous comment is really really really (Really?) really a hard thing to do (?). And if this isn’t enough, I’m not a native English spoken person, so that’s the reason my grammar often fail. But this is me 🙂 But I follow every post here, and sometimes there may also be something serious comments around, and at least I hope so…

          • Well they had fun mingling around the concept.
            I never get tired of it. Beginning of darkness / the obscure, last bit of light / hope.

      • Yes, the hole is currently being filled with foundations for something. But heard its not going to be house. But some sort of artistic installation. So, there is a sort of hope for the layers to remain there as “museum”

        • Ideally, section off a part of it behind a clear wall in the basement so it can be appreciated. Maybe get someone such as yourself to identify the various layers.

  7. A brilliant Post Irpsit and I just love that photo of Brennisteinsalda. What amazing colours. I am looking forward very much to the next instalment. Thank you Irpsit.
    I didn’t realise how big Öræfajökull is. No wonder the IMO made mention when it showed a little activity late last year!

    • Little is known about it due to its long repose times. GVP lists two eruptions, the big VEI 5 of 1362 and a VEI 4 in 1727. Selbekk & Trønnes investigation of the 1362 eruption ( http://folk.uio.no/rtronnes/Publ-peer-review-articles/JVGR07-Selbekk-RhyoliteMagma-Or-1362AD.pdf ) say that, based on the amount erupted, a conservatie estimate of the magma reservoir is 20 – 40 cu km but there seems to be no such chamber using modern identification techniques. From U–Th-series disequilibrium studies that yield a 10-100 year constraint, they conclude that the lead-up time from a first intrusion to an eruption could be as little as a hundred years.

      Nasty!

      • I am starting to have actuall problems with the interference patterning recognition techniques use to discern magma chambers. This problem is only existing in Iceland, and not for other volcanoes.
        The basis for my conundrum is that the rock in Iceland is hotter than common making any transition boundary (and that is what is actually detected, as sharp boundary works like a mirror, a “hazy” one does not reflect away the waveforms).
        There is actually “proof” of it not working in Iceland. And thar is Hekla. A swarm of very good scientists have written very good papers. Problem is that they are using the same technique from the same data-set, and still get ridiculously different results. So, either there are 20 something magma chambers AND counting under Hekla, or the data is way off due to the methodology not being viable.
        And since part of the methodology is using my algorithms I am starting to lean towards the hork-option here.

          • Yeah, it would make about 15 out of 20 papers on Hekla irrelevant.
            The algorithms in question is regarding refraction index countabillity. Ie, how much a given boundary refacts a wave-form.
            Those algorithms was mainly made for water purposes, but they have migrated into both volcanology and oil-geology. They are very exact for thermo-halines and salines in the ocean. Using them you could de-defract the waves reflection and look through the “mirror-effect” caused by the halines and salines seeing subs that previously was invisible.
            Problem here is that a thermocline is very sharp edged as the water works as it own insulator and the timeframe is short. In iceland you have tremendous uprising background heat, long timespan, and myriads of old intrusions. So, the thermal-boundary get’s insanely fuzzy. And also, the thing with upwelling back-ground heat. A thermocline is most often colder below the boundare, and heat rises upwards…
            This line of thinking comes from a long line of bouncing back and forth an idea that I and Lurking have done that pretty much got stuck due to us not being able to come up with a temperature curve at depth in Iceland. And surprisingly not being able to find an accurate lava temp for the hotspot lava of Iceland.
            Without a correct temp-curve you can not calculate the fuzziness of the boundaries correctly, and then you get huge numbers of “ghost” chambers in the reading. Why? because in the original algorithms you needed the temperatures on both sides of the thermocline to see through it….
            I wonder why I love hiding tidbits like this in comments instead of writing up a post. Perhaps I don’t want to hork up so many lovely but false theories that have been done about Heklas chambers by so many respected volcanologists? Hm…

          • I’d love to put models with several chambers under Hekla away.
            So it’s complexity comes back to chemistry and simpler feeding / stock questions. I’m set back of more than one year, but I like it so much to come back to my initial fantasies…

          • After pondering it I think there are two, or tops 3 chambers.
            The top chamber is well inferred, and exist where it is comparably cold. And that is the one residing right below the edifice. Then you have the deep chamber that we know the 2000 magma came from due to earthquake trace evidence that is not iffy. Nice and clear quake-stack there.
            From the lower there is probably a very hot channel running all the way up to the fissure like chamber at shallow depth. There might be a smaller chamber around 5-6km depth, that one is inferred from the borehole strainmeter data, so it is also not based on totally iffy data due to missused algorithms.
            So, basically we down to 3 chambers, or two chambers that are permanently connected via a tube, but with a fattening at around 5km. Take you pick.

            There is also probably some large dykes there too.

          • Phew. That is a relief. I had such a hard time imagining many and many chambers, and it didn’t fit with the sudden character of the eruptions. Here we have a nice link to the feeder source, but stuff on the way that allows speculations about whatever a way to mix that magma up a bit and create all these types of lava.
            I like that a lot, really.

          • Spelling is of no interest for a brilliant mind as yours masters. There’s more to your words that grammar and the right letters. Nothing troubles the source of wisdom from which we are allowed to drink.

          • Master, not plural.
            Anyway this was way too much slime? Or could you live with something like that?
            Need a shower – feel dirty… 😉

          • oh, juicy, juicy, we go from tephrachronology to seismic tomography in five easy steps. Maybe you could do a piece on this Carl as I, for one, am pretty much walking around in the dark on this. There seems to be so much conflicting information out there. One report stated that there was a huge area of melt under the TVZ and, as I recall, also under the Bay of Naples, then you get papers like this one:

            http://www.unc.edu/~leesj/FETCH/Papers/Lees_Magma_VolGeo2007.pdf


            which seem to contradict the others.

          • @Bruce:
            I will in the end write one.
            Now at least you know why all those contradictions do exist. Horked up data due to flawed usage of standard algorithms.

          • ‘It’s sad that governments are chiefed by the double tongues. There is rhyolite in your words of chambers for all Comanche to see, and so there is basalt in your
            words of strata. No signed paper can hold the magma. It must come from depth. The words of Ten Bears carries the same magma of chambers and strata. It is good
            that warriors such as we meet in the struggle of life… or death. It shall be effusive.’

            That ought to confuse the hell out of Outlaw Josey Wales fans doing phrase searches…

        • I’m inclined to agree. In the case of Öræfajökull, a 20 – 40 cu km magma reservoir does not simply disappear between eruptions in order to miraculously reappear and begin to refill a century or so prior to an eruption. The magma IS there. Now! Since they can’t detect it, there’s fault with the method used.

          This leaves us with an interesting situation. The reason Öræfajökull takes so long to build up to an eruption is the size of the magma reservoir, which acts as a thermal buffer against smaller intrusions. It takes a really large intrusion to heat that amount of magma, or rather, a sufficiently large portion of it to the point where there is an eruption. On the other hand, Öræfajökull won’t go away as it takes tens of thousands of years for magma resovoirs as large to cool below the point of no return.

          If this reasoning is correct, then the signs that an eruption is geologically speaking imminent ought to be very clear. We’d need an injection of at least 0.5 cu km of hot, basaltic magma which will result in unmistakable tectonic activity, ground deformation and tremor. Sigh… it won’t go off during my lifetime, no matter how much melange I consume.

          • I wonder what the melange might be for you… 🙂
            You forget that the hotspot is whonking up something like 5 and 50 cubic kilometers every year. So, all it would take is just a percentage of the yearly up-put lofted by the Icelandic hotspot to heat it up sufficiently.
            A few months of Theistareykjarbungas inflation should do the trick.

          • So if you have coputer time, then you can try to match that hypothesis by doing multiple simulations wih different temp profile both sides of the thermocline. If one or two profiles gets to fit….

        • Great thoughts on Hekla, Carl!
          I can imagine easily the 3 chamber system, with a significant tube connecting them. Only a few hours EQ warning at most !

    • Yes, Diana. Brennisteinsalda is the most colorful mountain of Iceland (actually I heard there is another one even more colorful somewhere in Snaefellsnes peninsula) but this one is top tourist attraction in Iceland because of its colors.

      The eruption in 1477 (Veidivotn and Brennisteinsalda) was actually one of the things that interest me most in Iceland. Apparently, the eruption started first in Brennisteinsalda, which is located at the north edge of Torfajokull system (still within it) but just touching the southern end of Bardarbunga/Veidivotn fissure region.

      From Brennisteinsalda flowed a thick lava that did not travel much far, but had an impressive depth on where it stop (about 30 meters thick) see here http://mw2.google.com/mw-panoramio/photos/medium/12380811.jpg

      And this is the view from Brennisteinsalda itself.

      Brennisteinsalda also erupted a pink rhyolite ash that is deposited on the top dark layer in fig.2 of this post. Afterwards, from what I read, the rest of Veidivotn erupted (with lots of dark brow ash and also plenty of lava). The nearest craters of Veidivotn are just a couple km north from Brennisteinsalda.

      Hence it remains the question whether these eruptions at Veidivotn are triggered by Bardarbunga, by Torfajokull, by both, or are independent from either.

      The rest of Torfajokull system is still very colorful and rhyolite rich, and makes the largest caldera in Iceland (larger than Katla) but its a subsidence caldera (probably by emptying of these amounts of magma). There is also a famous obsidian mountain in the center of the caldera, called Hrafnisnusker (if I spell it correctly); I think that was early Holocene. Next to Brennisteinsalda, there is also a volcanic peak which is entirely black, greenish-blue and violet colored rocks, called Blahnukur, but that was about result of an eruption 70.000 years ago.

    • Öræfajökull: yes, its the largest and tallest volcano in Iceland. And the most violent eruption of Iceland in last 1000 years is from it (larger than Katla or Hekla). Its dangerous in that it sleeps for centuries and then erupts very violently. To its bottom, last time I was there, I saw a thick deposit of white pumice some 1-2 meters deep.

  8. Last night I was wondering what became of Irpsit’s findings.
    There you have it!
    Great post!
    I have a question: last Eyjafjallajökull eruption doesn’t appear at all? I mean the XIX century one?

    • In 200 years from now, Eyjafjallajokull will not appear in a hole like this, if it would be dug again here. That is because 1) the ash blew mostly southwards, it never came here, 2) it was a relatively small eruption, for example in nearby Katla there is currently more ash from Grimsvotn on the ground than from Eyjafjallajokull, which is right next door. Because Grimsvotn erupted 0.8 cu km of ash, while Eyjafjallajokull only 0.3 cu km. It was almost 3 times more.

      But even so, in 200 years from now, you will only see a tiny thin brown ash from the 2011 Grimsvotn eruption. It will be almost imperceptible. The average deposited here was 1-2mm, that is something but it is tiny. Compare with Hekla or Veidivotn 1-2cm thick layers.

      • Please note that there are no changes in the tremor pattern, if that was volcano related there would be an almost explosive increase in tremor levels. Even a small gas-vent is surprisingly noisy.
        I guess this will go the same way as the last little stain spotted, the fisherman of the island will debunk it as a normal subsurface rock.

        • This is the aquatic version of…
          “Oh my God there is a small cloud at Hekla/Katla/Etna/Yellowstone, We are all going to die!” As little as any of the online volcanoes start an eruption with a small bit of smoke, neither does a sub-aquatic eruption start with a miniscule stain.
          First you see it big time on the SIL. You have large quakes. Volcanoes are the noisiest things on the planet…

    • The shallow earthquake which was originally located in the El Golfo bay was recalculated and the position of now 4 earthquakes is now about where already shallow ones have ocurred on the 1./2./7./11. of July.

  9. @ Irpsit
    Very nice!
    You can’t beat a good bit of tephrochronology!
    It’d be interesting to find if the differing layers are lithic/vitric/crystal tuffs or a total admixture!
    Brief visit today – Been away for a few days – back a few days then off again for a few weeks from Sunday!!

      • Nice feature! Do you think you can run the same analysis of other references lines, and after find an average out of a few lines? This is just what we need!

      • I selected one that was representative. See, the picture is at a diagonal and a pain in the arse to do that with. If it were a flat profile view it might be doable. (face at 90° to viewing angle)

  10. Have you noticed something? Or rather, noticed the absence of something? I haven’t heard much about a certain Icelandic volcano for a while. Nor about what really was up with the unseasonal ice free state of Öskjuvötn come to think of it.

    • Öskjuvatn is interesting, I had almost forgotten about it.
      But I know that our favourite blond icelandic volcanologist is up thereabouts. So, we will probably get to know what is happening there.

      Katla is just gone from the radar because it has finally sunk in that nothing is happening there. That will come back when something actually happens there.

        • It is coming. It has gotten side-tracked by my sabbaticals and her field-working.
          We will get back to it when she is not standing in striking poses on rocky out-croppings in Iceland. (Totally disregarding that she is doing a heck of a lot of other things that are more important).

  11. *Snicker*
    Someone just wanted to buy Volcanocafe…
    I am trying to phrase an answer to the guys inquiry.

    “Dear Sir!
    I do not give a crap about money, this is my zen-garden.
    So, you decidedly do not have enough money to make me even remotely interested.

    Yours truly!
    Grumpmaster 5”

    • You should have sold – a fool and his money… (The individual does not realise that you can’t buy the interest of the people who make this blog what it is.)

    • Sell it, and then we create le café volcanique…
      With the money you buy the meat for next years BBQ and open an account with the rest, for your future kids.
      And the other dude will learn an important lesson: there are things you cannot buy, no matter what economists might believe…

      • Hello all, I agree with “Shadow”, i think you should take the offer to buy Volcano Cafe as a compliment….but I think it would not work for anyone else than you Carl, because this site has a “heart that beats” and as we all know, we follow our hearts wherever they take us….we would quite easily abandon Volcano Cafe and follow “le café volcanique”…..if the heartbeat stopped, .because once the heart on Volcano Cafe stops beating, it will be nothing….I would like to say a big thanks to Irpsit for a very interesting post, your backyard is far more interesting than mine…and thanks too for the beautiful photos.

        • Hm, his backyard for sure is a treasury, but don’t underestimate yours. If you once have a “hole”, because someone builds a house in your neighborhood or something, take a picture of the profile and let us play with it a bit. Every square meter of our planet has a history, and the underground reveals a lot of it. As soon as you go back thousands of years there are signs for just incredible things that happened. Rocks are the book that tell us our world’s tale. We just have to take the time and learn to read it. And this story is so astonishing… Monstrous climate variations, volcanic eruptions, meteor impacts, sea level extremes, orogeny accompanied with all the landslides and rockfall stuff… Signs of it found everywhere in shape of a structural, mineral, chemical, biological detail. What only pollens and spores teach us about the past climate, reconstructing the world’s paleogeography and trying to understand what has lead to the composition and shape of the bit of earth we are standing on…
          No need for Irpsit’s exceptional layers to start having tons of fun.
          Near where I live there’s a millions of years old sandstone wall. A sequence of 14 days is preserved there. You exactly see the coarser deposits when the water rises from low tide, then the fine stuff that sets when things are calm during high-tide… Every day, and you can easily see the direction of the waves and current (I love inter-tidal environments). The sand grains containing microfossils and pollens/spores give you so much info on the climate and fauna / flora… The you exactly see the surface where good storm eroded several month of deposit, just above this perfect 14 days. Above that you go on with 5 days – storm – 2 days preserved – storm surface again…
          People walk by, tell you they would so much like to find a fossil once in their lives… You tell them “look left, a good part of the sand grains in that stones are skeleton bits… You see their big eyes, but also know they wanted a T-Rex skeleton and not some crushed foraminifera… 🙂

          • His backyard is a treasury, i wish mine was a little less of a treasury as it is. My ancestors seemed to love it to dig their garbage up in the garden. And where my garden is now, used to be a brickfactory producing all kinds of ceramics. Try to dig a hole to pant and appletree… almost impossible. You find all kinds of shards.

          • Well, sometimes recent history makes it hard to access the older stuff… Some trash dumps must also represent a bit of a handicap if you want to see more natural witnesses of the past…

          • Well my forefathers obviously did not want to waste old things. We found 100 year old broken beerbottles and even socks with giant holes when we rebuilt the floor in one of the flats.

          • It was hard times. Really, if they had to use old socks as building-material… 😉
            Now I’m getting afraid to spend my holidays in Austria…
            (Not really, I have family there and know you are a civilized country…)

          • Dont know Loco. I dont think my family had that hard times in 1894 when my house was built. (Later yes ) They used steel and had arches cemented . I dont know how to say this in english. ( Heck i dont even know what that is called in german.) Anyway. I wanted to connect 2 rooms and when they tried to tear the wall down they found a bow. Because we were nosey we checked the other walls too… bows everywhere. The architect said this was not exactly cheap and the steel would not have been necesary. I think it was just their hobby to dig trash up.

          • I have been looking at the Tour de France in a different light this year, because of all the info and landscapes.There are also some unique rock formations almost on my door step, once the weather warms up, I will be exploring some of it with camera and scraping some stuff as well, a metal detector which needs fixing will be by my side as well

          • I think that my backyard is going to be a bit tricky as when we were building the house, we needed one of those great big digger machines to break through the solid rock below and even when we were trying to clear space and make a flat area for the garden the guy “driving” the digger machine, said we would be better giving up at a certain point as he was hitting what he called “living or “live” rock, which was not brittle enough to be broken easily and it would have started to cost a lot of time (and money) to keep going….

    • I am sure all of us here would understand if you sold as none of us are fools. What would he buy? A Blog site. What would we do? Go where we can freely discuss, laugh and learn. The buyer could write educational and factual posts IF he was a volcanologist, geologist or a very knowledgeable amateur.
      He could not buy the goodwill, the”chemistry” and the uniqueness of the individual commentors.
      Interesting one though. I am presuming he would use the site to place adverts for a fee and possibly also demand a subscription…….
      Would I stay and contribute my time and ruminations if the site had no dreadful Dragons, Randy geologists and hat – eating sheepy daleks ? Now let me think…………….NO!

        • If I might ask a favor – leave a trace so we can follow at least for looking at the plots. It ranges from interest to fun. One can live without it, but it’s such a nice peace of entertainment.
          How “simple” (in the negative way) must one be to think you can buy the free minds of the people in here? We’re like water – fluid and gassy when bantering around, but hard and cold when taking decisions… 🙂

  12. Thanks to everyone for your kind comments 🙂
    I am joyful to share this so we can learn something, hopefully, new.

    Please feel free to challenge the identity of each of the layers because 1) I am just an amateur and 2) for most layers I am not sure about their identity (volcano and eruption)

    • Newsflash – the scientific method/approach works wonderfully well even for amateurs such as ourselves. 😉

      • Oh, ehm, wanna try contributing with newsflashes: Kim Yong Un seems to have got married…
        Yeah, as said, was a try. Maybe I’ll come up with something else another time…

    • I think your post is great, gives me ideas as well, one never knows what one finds in a lucky country is a saying down here

  13. YELLOWSTONE ALERT!….

    Whats the alert? That I brought it up. Nothing more.

    This is a plot of the quake depths at Yellowstone over the past few decades. I’ve always liked this plot. You can see the point at which water crosses the supercritical point (pressure/temperature) and causes an increase in quakes.

    And for what lies deeper, all I can do is point you at Chris Rowan’s excellent 2010 post about it.

    http://all-geo.org/highlyallochthonous/2010/08/yellowstone-what-lies-beneath/

      • As I write this, Sakura-jima is having another big hick up.
        Lurk, a question, hopefully a less stupid than the former one:
        “…a large reduction in the rate of plate convergence, could be linked to this splintering of the subducted plate, and the reduction in slab pull that would have resulted.”
        Would there be a counterpart of this reduction in the rifting activity in the ocean? I mean, is it measurable?

        • Hey Renato, I am working on the premise that stupid questions will give this site an edge over the competition, so I think it is fine when you and I keep rolling out the stupid questions. As for Sakurajiima, it looks like it has forgotten to stop for a breather and is now in constant eruption (well, at least the last half hour I’ve been watching).

        • Yeah, I think it shows. Juan de Fuca and it’s two friends (Gorda and Explorer) do not subduct at anywhere near the rate that the Japan Trench does. Likewise, the Ridge that feeds the backside of them is no where near as prolific as the East Pacific rise… and it has the Subduction zone along south America as well as the Japan trench system pulling on it’s plates.

          More this later if I can remember to look up the numbers.

        • Okay, the per side rate of the Juan de Fuca Ridge is 29mm/yr, the East Pacific rise (Nazca and Pacific plates) is 75mm/yr.

          The Nazaca plate is dropping under the South American continent at about 79 mm/yr, and the Juan de Fuca plate is dropping under the North American continent at about 39 mm/yr.

          Both subduction rates are driven by how fast they are being pulled along, as well as the movement of the over-riding plate. I know that the North American plate has a rotation pole somewhere near Lac Madeleine in Canada. This is evident from the transform faults in the Gulf of California. (that’s about where they line up if you plot a great circle path off of them)

          Rotation poles are the point that the plate seems to rotate around and you can use transform faults to find some of the relative point of rotation. I think the Hreppar-North American Plate rotation pole is at 65.2° -20.1°W and the Hreppar-Eurasian Plate pole is at 62.8°N – 21.3°W. Relative rotation is going to figure into the actual speed that stuff happens at the boundaries. (Hreppar info is not part of the discussion, and was only mentioned since it’s a related tidbit of info)

          The big difference in those two subduction regions, and the feeding ridge, is the mass of the subducted part of the plate pulling it along. The ridge provides some push, but based on what I’ve read, slab-pull is the dominant force.

          • I have never really grasped the information about the ridges in the Pacific. There is lots about the subduction zones but I always feel the information about the badly named Mid ocean rifting areas is a little “hazy”. probably because these ridges, especially those in the south towards the antarctic may have been mapped but not studied really closely.
            There is also the Darwin Rise that may or may not be a Hotspot. Still lots to discover and explore I think.

    • Such a neat presentation, I wish there were such profiles available for many more well-known volcanoes (nudge-nudge, a wink is as good as a nod). How about a topic with nothing more than a graph for some six or seven volcanoes with no more info for each than what you’ve just presented? Please?

      (I must be a nutter. I mean really, to find such stuff exhilarating…)

      • Well, if your pokin’ at me… I have no problem doing the plot… provided there is data to be plotted.

        What I usually run into is a serious lack of data.

        Yellowstone is good in that they have a pretty large flat file of all the data. El Hierro is good in that respect, though nothing much was happening until it started getting noisy. Iceland is another good site, but there is so much stuff going on there that it’s really easy to get lost trying to make out one system from another. Hawaii is good, but it shows up pretty much as a bunch of tendrils feeding up off of the plume into the volcanic system (I think I still have the Hawaii system on my Youtube channel, look for Geolurking, animated rotating plot and very cool once you realize what you are looking at.)

        As for the rest of them… not very easy to find data on. I had wanted to do nice Santorini one, but they keep all the small stuff locked away so the general public can’t see it in flat data file format… (almost as if they have something to hide.) The small quakes may not signal a catastrophe, but they allow you to see nuances in the way a system works.

        Since you are into stuff like this, here is an old plot that I did of the SISZ from west of Hengill to East of Torfajökull, these are the quakes in a rectangular box represented as the expended energy per event.

        It’s one of the plots that make you go “eh?” Since what appear to be interference patterns show up in it. We kicked around the idea of what makes it do that for a few weeks and even had a few heated arguments about it.

        The one clear thing is that those patterns are the spitting image of interference bands… why they are is a different story. A lot of mechanisms could be in play… but one thing you need are energy waves. Electromagnetic doesn’t really operate on this scale (well, that we can easily see.) Acoustic might. Acoustic waves have a shared characteristic with Earthquake P-waves. They are both compressional.

        Mainly, it’s just freaking weird.

        • I remember those discussions. I learned so much ,it was during those that I plucked up enough courage to start asking questions. Not being laughed off the site I am still here and still asking questions.!

        • Beautiful plot! But to return to the original one, what I liked about the Yellowstone one was how clearly you could see the various layers due to the number (%) of eqs. I think the profile such a plot provides would reveal a lot about the nature of the activity around Herdubreid, not to mention how clearly Katla’s boundaries (glacier – surface, surface – hydrothermal, hydrothermal – magma reservoirs, magma reservoirs – crust) ought to show up, especially if only 99% quality quakes were used.

          Actually, I think that such profiles may turn out to be a useful identification tool as long as there are enough quakes. Take Hierro day by day and make a movie of how the profile changes. Possibilities are great!

          Anyhoo, that was my reaction to the first plot you provided, cheers!

  14. Good morning/ evening/ G’day to everyone
    Sakurajima is very active right now. I like this camera shot as it is interactive and you can see the craters in detail. It can be seen that now the larger eruption comes from a vent behind the ash cone that has been active these past months.
    I do wish I could read Japanese.! Google tries!
    http://webcam-svo2.pr.kyoto-u.ac.jp/local/camera.html

  15. {snicker}…. (actually, I’m laughing my ass off, but that’s not important.)

    Earlier, I posted a song by Tool called “46 and 2” in response to the Lurking shadow critter. The idea being that the song is about the “shadow,” a manifestation of our subconscious. Specifically, that which we repress.

    Tool is a good group, and they have some very good music. A bit more thought goes into their lyrics than you typically find in popular music. However, some of the stuff is on the periphery of accepted knowledge about the way things work… if you are into “New Age” ideas you will recognize some of topics in their music. Part psychology, part loon stuff.

    Anyway. One of the central things that the guy that made the accompanying video brings up, is the idea that we have 44+2 chromosomes. The song goes on about “46 and 2 being ahead of me.” The video author goes on to note that there are three types of people… and that they perceive reality in distinctively different ways. The first type has 42+2 (total of 44) chromosomes and essentially shares one consciousness or experience of the world. We have 44+2 (46 total) and live in a disjointed chaotic vie of the world. The ultimate goal is to have 46+2 (48 total) and to ascend to a higher level of conciseness.

    So… me being me, I looked into the claims… specifically the chromosome numbers. (diploid numbers)

    Many primates have 48 chromosomes. Orangutans, Chimpanzees, Gorillas etc. The largest difference is that human, with 46 total, seem to be missing a pair. Well, we aren’t. Chromosome 2 in humans, is longer than in other primates, it is essentially as if number to is a fused version of two if the primates ones. Thats the largest difference.

    http://www.indiana.edu/~ensiweb/lessons/chr.bk1.html

    So… if the idea is that we are to “ascend” to this 46+2 state… we would be going backwards. That is unless browsing the vegetation for fruit and making overnight bedding our of leaves and fronds is the ultimate in human existence.

    Eh… go figure.

    Know what else has 48 chromosomes?

    A potato.

    • It looks like they upconverted the spectrum into the audible range. Easily done if you can get the raw waveform.

      I’ve done this with other earthquakes, that echo sound is the one that un-nerves you. It’s almost as if you can sense whatever it was as it passed.

    • Dude!.. that channel has an even better on here

      The upconverted signal allows you to hear the tooting of the resonant feature that makes a harmonic tremor a harmonic tremor.

      Sounds like someone blowing on a whistle and the wheezing for the next breath.

      • I think the spanish translation at the start of the video says something about a well greased waterbomb !!

      • Sounded amazing with 25Kwatts…
        If anyboody is wondering, a friend of mine bought a large nightclub, we are testing the soundsystem.

  16. Speaking of a treasury. One thing i wanted to discuss with my fellow dragons and most especially the wordpress- guru Ursula. I have noticed over the month that most spam arrives on the page treasury which is only treasury via the link it is really Gems in the menu. Would it help if we renamed it to something less obvious, like xyz or whatever. Would this help getting less spam. Does anyone have experience with this?

    • Hi Spica: you could disable comments on the top Treasury page. They are disabled for posts 15 days after post publication, but they are not disabled on pages. I think this would work, but no time right now to check how to do it (have a crazy day today, plus just got a rejection from a funding agency, grrrr… ok, maybe not too catastrophic, I can reuse bits of proposal in other proposals, but just really really annoying!! 😦 ).

          • Always did it that way. But i dont know how. There is an app, but then you d be rid of all comments on all pages. And what wordpress describes on thier site…. check the edit page and look for the discussion ,,, Huh where??? cant find it. Sorry. Once you are not as busy… Ursula please help and explain it to an ancient dragon,

  17. I am just watching Hamarinn area ( Western side of Vatnajokull for any who do not know Iceland). There seems to be a lot of activity going on under there. Skrokkalda is usually looking busy but this SIL also is joining in. I don’t think this is ice I think it is magmatic. Shout at me if I am wrong .

  18. Great post, thanks. Lovely to see those rhyolotic colours again as well.

    We’ve got some applicable tephrochronology in our backyard over here as well (Mid-Norway). One layer is named the Vedde ash layer and probably originate from what was a pretty huge Katla eruption. It’s dated to aprox 10,600 yr BP (14C) and we find it buried (even as a visible horizon at some locations) deep in bogs and lake sediments. Now, what makes it applicable is that it’s located outside the Younger Dryas ice sheet margins – so whereever we find it, we know that area was deglaciated at that time. A really good tool when combined with moraine chronology and stratigraphic studies. However, it’s one of the few ash layers we find distinctively visible in facies, so I bet the eruption must have been rather big. Prevailing wind conditions means alot though, of course, but still ..

    • Well, at least from the last ashy eruptions I have seen in Iceland, Norway has been one of the first affected places, so , it makes sense to dig a hole there too. 🙂

      • Need to go deep to find the visible ones, so I need to move my shovel and tent into Irpsit’s backyard 😉

      • Actually Carl that will make MUCH more sense than the common accepted hypothesis of Vedde ash coming from Katla. They often say Vedde ash is whitish, but Katla never erupted ever a white ash, but only Hekla, Oraefajokull and Askja (and Torfajokull to a minor amount). I think it is likely that Vedde ash was either a caldera from Askja or any other of these volcanoes (but Askja is the most likely candidate)
        One could analyse the Vedde Ash. Hekla has specific composition of its pumice, different from Askja I guess. And Oraefajokull probably too. To me, naked eye speaking, they all have large deposits of similar looking white pumice around them.

        • Odd thing here, I have never even heard that it would be Katla. And at around that time you have a rather cataclysmic eruption at Katla… The large caldera. And that should have been the largest post-glacial eruption at Iceland ranging in around a heavy VEI-6.

          • It said here http://en.wikipedia.org/wiki/Vedde and actually in some papers I read too.

            You were the first person I heard suggesting it was Askja, but I think you are correct. Askja did have a large eruption 9000 BC, and I cannot see the Vedde ash (being white9 coming from Katla). I think the source must have been Askja or Hekla (or Oraefajokull but that is less likely).

          • I haven’t seen it stated for sure that it’s from Katla, so it still might be up for grabs. I know they did alot of collaboration with Icelandic researchers back in the 80’s and alot of geochemistry tracing, but I’m unsure on whether they came to a solid answer. I haven’t seen Askja mentioned anywhere though, but I’ve heard Krafla been brought up. I doubt the last one though. As we’re in mid YD both Askja and Katla will be situated under thick ice covers, hence alot of ash production is possible.

            It’s dark grey-ish to black when saturated over here, and grey to dark grey when dried, so not whiteish, Irp.

            “The basaltic component of the Vedde Ash is very similar in composition to the basaltic ashes erupted from Katla .. Particularly the high TiO2 content (about 4.5%) of the Katla and Eldgja basalt lavas and tephra …” It states however that Katla only has erupted basaltic tephra in historical times.

            So as I mentioned, maybe up for grabs. What about an Eldgja fissure eruption when glaciated? Fire away

    • Can’t get that one to load. But Sakurajima has been emitting vapour clouds most of the day (maybe all but I have not watched all the time) so the air quality may be poor, depending on the wind direction.

  19. Boris has just declared on FB that strombolian activity is likely to have reinitialized at Bocca Nuova Etna’s crater. Rising tremor confirms that possibility.

  20. Thanks for the great post Irpsit! I’ve been away for a day so missed it coming out. I love tephrachronology and context layers (from my archaeology days). Like GeoLoco I’ve enjoyed happy hours in the mud. One cautionary tale: when I first started to be interested in archaeology I happened to be on the Severn Estuary one day and saw a newly exposed cliff area. About two metres down was what looked like a bit of pottery and I dug it out. In the river valley where I live the Roman contexts are buried under about two metres of colluvium so I was quite excited to think that this pot might be Roman, or mediaeval at least. Severn mud is very bad – thick and sticky – so it wasn’t till I got home and gave it a good scrub that I realised it was a bit of thick plastic – dated from the 1950’s at the earliest! So the moral is to always check the local conditions.

    @ Spica: I’d love to have an old rubbish heap in my garden! All I’ve ever found was a bit of pot dating to 14th century. The rest is modern or Victorian – and there’s very little of it. 🙂

    • The place where this excavation is, has been always wild land. This is a region where some farms have existed and remained at their places for centuries and most of surrounding land is wilderness, just tundra basically. I doubt I could find a plastic two meters below as the land has been mostly intact (human-wise). The walls of the excavation show the intact ash layers dating at least since 1000 BC and probably way more behind. If some human activity had occurred it would disrupted this, as is next to my house (if I dug in front of my house, I see nothing because it was a construction site 30 years ago, and if I dig 50 meters away, it was a forest that was planted 80 years ago. But away from the farmland and forests, its basically untouched tundra below ground. You even find 2.5 meter below lava rocks, from what it was the eruption of the nearby shield volcano Lyngdalsheidi (which was pretty large one). My concern is only when I hit around 8000 BC (1-1.2 meters deep), a thick mud layer appears (above the ancient lava rocks – you can actually see this dark mud in Figure 2 at its bottom), and this is part of the discussion I will do in part II. I think it might have been caused by higher sea levels, an ancient river flowing here, or glacial activity.

      • Hi Irpsit: This is what I mean about knowing local conditions. You know your local volcanic layers “like your own backyard” as we say. The problem I personally had was that I had learned about my local conditions and thought they would be the same 30 miles away. Now I know, like you, that conditions can be very different depending on rain, wind, and climate.
        I’m really looking forward to your next article – especially the deep mud layer at around 8000BC. 😀

    • @Lucas, LOL! Time Team are very fussy about where they go. The town I live in goes back to very early Anglo-Saxon times and there’s lots of Roman stuff around – a big villa nearby etc. so I had hoped for a bit more. Part of my house was built in the 16th or 17th century and I guess it was farmland before then, so I should be pleased with my one little bit! 🙂

  21. ER are reporting that the Atlantic Explorer is back in the area of the lighthouse and that SABI is rising in the vertical deformation.

    ,,The University of Nagoya’s deformation stats are showing a strong climb in Ultra Rapid vertical deformation at SABI (more than 1 cm). The other stations are stabilized.
    – We do not know whether we are the only ones having trouble in reaching some data from the IGN website.
    – The Atlantic Explorer (chartered by the ULPGC or in long words the University of Las Palmas de Gran Canaria) is back in town and is doing some research in the Las Calmas sea (also in the Lighthouse area).,,

    http://earthquake-report.com/2011/09/25/el-hierro-canary-islands-spain-volcanic-risk-alert-increased-to-yellow/

    • Sakurajima is hard to put a VEI on since it is pretty much permanently at a low level eruption. If you add it up it is around a VEI-3, but that is the combined value for 3 years. Last few days is still a VEI-0.

    • I’d be interested in learning more about SakuraJima and the larger Aira caldera system. Southern japan is a unique and interesting area of volcanic activity with 3-4 large VEI-7 eruption events occurring within the last million years. (Aira, Ata, Kikai, and Aso calderas). Some call ASO a “supervolcano”, but to me, it’s all relative, and it’s simply one of the “bigger” caldera systems in hihgly active volcanic area.

      While Sakura-Jima is unlikely to do anything particularly large, it’s had some large-scale eruptions in it’s past history, including VEI 4, 5, and 6 (if you include Wakamiko Caldera as part of Sakurajima). I’d be interested in learning how activity changed from less common more powerful eruptions to the more vulcanian type activity we see now, and the ways in which activity could change or evolve in the system.

      From what I’ve read on SakuraJima, it has a magma chamber which is fed by the larger magma chamber beneath the more northern Aira Caldera, but also may be fed by another magma source to the south.

  22. Fredrik: on Vedde ash (which me and Carl were kind of postulating it might have been a large eruption of Askja rather than Katla, but I also suggest there is a change of belonging also to Hekla or Oraefajokull). What color do you have in your Vedde ash?

    In my own spot, we have a thick brown mud at below 80-100cm, (which is around 8000-10000 BC), so I guess it is less likely that we might find the Vedde Ash. This mud might have formed by an ancient river flowing in my current location, higher sea level (I am now at 70m altitude, this spot might have been closer to sea), or just glacial activity (anyway I don´t know what to look for glacial activity, which covered my spot during ice age). But in the 10mx10m excavation, I found one spot with a part of what it seems to be a white layer around that depth and estimated age (100cm, around 9000-10000 BC). This will be part II which I am currently finishing writing.

    PS: there is also another famous European wide ash, the Saksunarvatn ash, which is even larger than Vedde ash, and dated 8000 BC (Vedde is 10000 BC). The Saksunarvatn probably came from the largest Grimsvotn eruption in Holocene, and its brown, which means it is probably from Grimsvotn or Bardarbunga (no Katla, no Hekla, no Askja). But Vedde, if its whitish, doesn´t look Katla to me, it looks Askja or Hekla.

    To those that don´t know this; its nice to travel around Icelandic volcanoes. Around Hekla we have a vast extent of white pumice, and so around Askja (and even larger white pumice desert). Around Katla we only have dark grey ash. Around Oraefajokull we have white pumice too. And around Veidivotn we have plenty of grey material and colorful rhyolite within Torfajokull caldera. There is some large ash deposits also around Langjokull.

    • It is easier to find the source of the Vedde Ash (relatively easy).

      One must do a soil profile in just a few places in Iceland: north, east, west and south, quite away from the main volcanoes, then find where the Vedde Ash is, and then move inland towards any of the volcanoes, and do soil profiles there and see how the Vedde Ash appears. If its large near Askja, then we know it. It is easy to suggest this, more difficult to do so.

      I must drive a lot and take a shovel with me. Dig in the four corners of Iceland.

      • Suggestion.
        Get a piece of the Vedde ash and one from Askjas Ultra-plinian caldera formation. Then you only need to dig twice… And, if we are lucky Birgit can SEM the crap out of it for us.

      • Didn’t see this one – comment up there with the others. The Saksunarvatn is not found here I’m afraid, but I’ve read an article where it’s found and excavated on the Faroe Islands. I can send it to you, along with some local Vedde ash material but how do we get in touch through this system?

      • Not too easy. You need to go outside the YD maximum, elsewise it’s just deposited on ice and redistributed. And you should try in the prevailing wind direction, so towards Norway from whatever volcano you start off with 🙂 And you would have to dig deeeep, there’s aloooot of tephra covering a 12000 years old layer.

      • And the 1875 ash was dachite close to rhyolite with the actual explosion ash being rhyolite. So that one would be fairly close to the Vedde Ash.
        And then comes the massive rhyolite caldera formation that happened 9000 to 10000 years ago. It gave a very thick silicic ash that is smack bang in Lurkings plot of all things geolavatic™.
        Guess what colour it has?

    • Evidence for glaciation is morraine deposits, heavy erosion, indentations on rock left by the ice and rock debris, u-shaped valleys; and, for volcanoes – tufas & pillow lavas?

      • I was meaning “how do I see the evidence of glaciation on the soil profile?” How much soil should I expect between both interglacials? Because the trouble is that I see lava rocks 2.5 meters below that can only come from Lyndalsheidi that erupted in former interglacial.

        • You can look for traces of “tectonics” due to the weight of the ice – actually in the picture in your post it looks overridden, but I think that’s due to the man digging the hole rather than a glacier 😉 You can’t say how much is deposited or eroded during glaciations, but usually the material is removed and redistributed when it is overridden by the advancing glacier and then there is some basal till deposited. So you probably have that at the bottom, maybe with some ablation moraine just above. As for the Vedde ash bed, I think you need to go pretty far towards the coast, as the YD margins in Iceland were located far out. In brief 🙂

          • Yes, its a quite complicate puzzle. Basically I am 30km away from the coast, at around 70m altitude, and it was just a few kms away where the sea levels reached during early post-glacial. Although I can look at the evidence of ancient beaches in lateral side of nearby mountains, what should I look for in the flatland valley?

            Also, there is a near ancient moraine, just a few kms north of here, where a large glacier from what is now Hofsjokull/Langsjokull spread until almost here. But I also know that at peak of ice age the ice cap was much more: it was actually covering the whole current Iceland because you have 300m high tuyas until the coastline. So I was basically under 300m+ thick ice. I found this big 1 meter thick mud deposit at the bottom of the excavation, I think it might have been caused either by the presence of ice but also probably due to water running (or actually both).

            Also the Hvitá river, one the largest in southwest Iceland, which runs from the glaciers, runs near here, so this is a old glacial valley, where glaciers advance, glaciers receeded, floods happened, and sea level advanced. I think because of this I cannot find a clear band that I would say it’s the Vedde Ash. But there is a big dark brown band at around 80cm, which could have been the Saksunarvatn ash. It actually makes sense as this dark band is just above the mud sediments (which correspond probably to Young Dryas glaciation, or the melting that followed). Below this mud, its a lot of volcanic rocks. Ok, they might not be the Lyndalsheidi lava that flew here, but just carried from the highland volcanoes.

            Second question, if there is a shield from interglacials before the ice age, should I expect it something specific, other than being more eroded than usual? I often see that the lava rocks in those are all rounded, eroded, and with their gas holes almost eroded away. Is this a correct observation?

        • Irpsit:
          The content should be very low in organics.
          Since it should be material created by pure ice grinding if it is glacial you would have hardly anything organic in it.

        • What kind of magma does Katla and Hekla usually erupt? If I remember well Eyjafjallajokull was andesite. Sorry to ask, I am trying to see if there is a trends of most central Vatnajokull eruptions (Veidivotn, Laki, Grimsvotn) being basalts, while those of Askja and Torfajokull rhyolite.

        • Its definitively the most poorly understood big volcano of Iceland. And in being the largest volcano in Iceland, and having had the largest eruption since settlement that is a BIG lack.

          So far no one knows what kind of eruptions Oraefajokull had prior to settlement. But in my soil profile study, I found all few white layers to be probably Hekla eruptions (its about 4), no Oraefajokull in some 8000 years analysed, at least here in the southwest, but plenty of evidence for plenty Grimsvotn eruptions.

          • Not to forget our dead discussion on which volcano had the largest lava-barf on Iceland after Iceage. At the same eruption Askja barfed mightily and created the largest lava plain on Iceland, the Odhadhahraun. I am still trying to get data on that flood basalt, but something tells med that is should dwarf both Bardarbunga and Theistareykjarbunga.

          • Its actually difficult to know what is biggest discussion. Because things get eroded quickly over time. Looking google earth, one sees the largest white pumice deposit in Iceland just NE of Askja. That occured in 1875, you don’t see the pumice from 8000 BC Askja eruption any more. It is burried. But you see the remains of the 1104 Hekla white pumice eruption (or one the big ones following it) to the NW of Hekla in Tjorsádalur valley. It looks it could have been as big in scale as Askja 1875. Curiously you don’t find as much white pumice around Oraefajokull from its 1362 eruption (it fell to its SE, probably most went to sea).

            Lava field wise: Askja has this 8000 BC second largest lava field in Iceland. I say second largest because largest is the Tjorsáhraun from Veidivotn fissure. Just go to Google Earth and look at the area from Veidivotn following Tjorsá river to where it ends towards the sea, and spreading westwards to Hvitá river and Selfoss. You don’t see it in satellite image any more because unlike Askja lava field, the Tjorsáhraun was covered by much Hekla ash for centuries, and also grassland. But its still here and I can assure you by personal experience this is largest in Iceland, followed by Askja one. Ah, the Askja one, I am not even sure if Odadahraun even came from Askja, it could have started from the northern side of Bardarbunga and flown all the way to north coast.

            Other very large lava fields includes Edlgja (now covered mostly by Laki which is also very wide but not as wide), and others include Hallmundarhraun and Kjalhraun (Langjokull volcanoes, but they are pretty “recent”). The trouble is that lava fields get covered by vegetation, ash and other lava fields, and so in places like Hekla or the dead zone, it becomes complicate to measure them.

      • Say… you don’t suppose that we are seeing an awaking Öraefajökull do you? The 1362 eruption was rhyolitic as hell, and the 1727 eruption was mostly trachyandesite… a more primitive magma. Maybe this is a really really slow re-awakening and the next one will be more mafic.

    • I think you have the 14C dates for the ash beds – Saksunarvatn is aprox 9000 calibrated years (8200 14C?) years old and Vedde aprox 12000 cal. yr (10,300-10,600 14C). I can calibrate them more accurately tomorrow, I’m waay too tired right now

      • Sorry, the Saksunarvatn is aprox 10,000 cal yr BP (aprox 9000 14C yr). And it’s found in western Norway, only not as a visible layer.

  23. Hello All,
    just finished a stint at work, followed by the pub…
    Been finkin’
    Since the Burfell barbeque is at least suspended…
    If people would like to get together and put faces to names, why don’t we do it on the Canaries?
    Why the Canaries? I hear you cry!!!
    There’s a few reasons; in no particular order:
    1 El Hierro; we could at least do a field trip in Geoloco’s schteam powered hyper schonic helicopter…
    2 The rest of the Islands; they are an arcaevolcanological paradise…
    3 They are the crossroads of the world; Cristobal Colon stopped off there several times…
    4 It would be somewhat more affordable for many of us and a lot of our commentators live on the Islands…
    5 Y’ never know; Teide might blow it’s top while we’re there 🙂

      • 7 If you find the right restaurant the y cook a mean goat/rabbit/mutton/veal/meatballs/arepas/calabicin estofada (for the vegetarians) 😀

        • 8. The Beaches (for a days relaxation) Fuerte has in Jandia Beaches that are as good as the Caribbean.

      • I’ve been; he may have had some “illicit” tryst’s with the “Lady” of La Gomera and stayed on that spot, but as far as I can make out it’s not a Columbus era house…
        9 La Gomera is well worth a visit, there are sone awesome plutonic emplacements and every Palm tree is accounted for in an regular census!!! (That s true) They make a wicked palm wine from the sap, it’s “tapped” a bit like rubber or maple syrup…

        • La Gomera is also famous for it´s people being able to communicate accross the mountains by whistling to each other(I don´t know if this is unique in the world, but certainly very rare) – they can have proper conversations just by whistling,I saw a documentary on it a few years back and it was absolutely facinating…., however it is a “dying” language – they are really trying hard to teach the new generation so that it does get lost forever.

          • Judith, ooh yes, I belive Fuerteventura has the best beaches in the Canaries, however I did come accross one beautiful stretch of beach in Lanzarote, which also has a really lovely National Park where they will barbecue you a meal over the direct heat from a vent of the Volcano….La Palma (called the pretty island) is also apparently a stunningly beautiful place…good for those who love walking…Gran Canaria also has those stunning sand dunes that take your breath away by the sheer size of them – makes you realise just a little bit of what a real desert must look like… but I would say point 9 i¨: The Canarian people are so warm and friendly and very welcoming to any visitor……….

          • 12 Silbo Gomero: Last I heard it had been protected as a local “dialect” by the EU, it’s not actually a langauge, it’s a way of speaking, it works for english, german, swiss etc (once you’ve tuned in) I believe it’s taught in the schools now. It’s a variation on the “two fingers, really loud and piercing technique” which I never mastered…

            This video is in Schpanish; but the subtitles “fit” the whistling…
            Enjoy x

          • I was going to say the same! Only last week I saw a show on Brazilian TV about that whistle-language. Amazing thing! Formerly it was based on Guanche speech, than they “translated” it into Spanish.

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