Update on the weekend activity


This weekend was quiet in Iceland. There was almost nothing going on. There was only one small earthquake swarm in Krýsuvík volcano. But this earthquake swarm was tectonic in nature, not volcanic. The largest earthquake in this earthquake swarm was about ML3.2 in size. Few earthquakes where in Katla volcano, but less this weekend then many others. But it is normal for Katla volcano to be quiet during November to March each year due to snow that is added to the glacier. But that increased the pressure of the glacier on top of the magma chamber (floating balance laws at work here).

Mainland Spain

There was a flurry of earthquakes on Mainland Spain during the weekend. None of this earthquakes where felt, from what I can gather at IGN web site.

Canary Islands, Spain

The eruption at El Hierro volcano continues as it has done for the past almost two months now. The harmonic levels are about the same as it has been, but there seems to be minor intermittent in activity from El Hierro volcano. IGN has setup a picture web site with images that show the activity since this eruption started clearly.

Erik at Eruption blog has good blog post about the magma mixing that appears to be taking place in the eruption in El Hierro volcano.

Other then this. Is is all quiet in Iceland for the moment. But frost-quakes should be expected in the next 48 hours or so in Iceland. As the ground freezes over in a really cold weather.

98 Replies to “Update on the weekend activity”

  1. I said that the thickening ice in winter, with snowfall would help keep pressure on Volcanoes in Iceland a few days ago, now i know it would not stop a developing eruption but i would help maje eruption less likely, where as as the ice melts in Spring the extra pressure released from the ice melt would make eruption easier.
    But i was told it made no difference at all.
    I take it Jon, that my theory is basically right and those who ridiculed it are wrong.

    1. This has been well known for some time now. There is no study on Katla volcano directly. This has been observed in Vatnajökull glacier and after the last ice age.

      There is a difference, because the ice is heavy and thick. This increased the pressure on the top of the volcano. Making it less likely for the magma to be able erupt, then it otherwise would be able to.

      Here are two papers on this type of subject.


    2. “Has an effect” and “is the determining factor” are totally different beasts, also here. If you can not make the difference between the two, you’re lost.

      Ice does certainly affect the pressure (see e.g. Lurking’s plot), but the effect is minor on the Earth’s surface, and even smaller on to the magma chamber. The extra pressure due to ice affects the eruption probability only when the volcano is close to, i.e. on the brink of eruption.

      Grimsvötn is a nice example of the more typical situation: When the volcano decides to erupt, it does so, with or without the ice. Why? The volcanism is the determining factor, the ice is only “an environmental condition”.

    3. There is also a possibility that the annual change in pressure, as slight as it is, may speed up the fractioning process and make the magma evolve more quickly as the pressure shifts back and forth.

    4. Pyro-Not really and its not incorrect either. As published and mostly accepted when magma gets to within 3-5 kms from the surface as a boiling mass of gases and liquid rock it starts to release that vertically. Gases break the rock, the magma exploits them and because of the lowering of the pressure it starts expanding into higher volume and really starts the process going.

      Higher pressure from rock, ice, ocean or a combination of all of them would serve to keep that gas from expanding. But also as widely accepted is the 3-5 km magma buoyancy equilibrium. Remove the ice, or the ocean or even allow a vent tube to come up 100 meters and it can tip the scales.

      There is so little that is known about the earth and its processes that we likely will never get a handle on it with only the general stuff being accepted. We have seen groups like the IPCC use information, without verification and accept it because it came from some previously held in high regard scholars. Now branded charlatans we are rethinking things.

      Its the open mind that accepts theories and then works to disprove them. By elimination they came up with the magma equilibrium theory and it may or may not be right. It would be acceptable to assume just one thing about Katla ..The general idea and that is when the pressures below exceed those above it will erupt. I think we can all agree on that. Everything else is conjecture and I can laugh about it and say …What do they do if the ice turns to water and runs off and there is no eruption? Or if it does?

      I dont think if it does that anyone is going to give a care about that until years after a Katla eruption is well over.

      And then the new theories will abound.

    1. Great pic & at night as well! When i think of the amount of times in the passed when i visited Iceland & went to the Skogarfoss waterfall, only once did i see the rainbow & it wasn’t a particularly good one!!

  2. Still Katla has more earthquakes towards the autumn, when ice is at minimum, and also most of its historical eruptions have been around that time of the year.

    However, I do not see any pattern for Grimsvotn or other volcanoes.

    1. The ship will soon appear in the web cam view. Their main objective will be to map the seabed with sonar equipment I think.

  3. Hi, this is my first post! Wonderful site by the way, lovely to read such informative discussion.
    Please may I ask you all a question?
    I have noticed a sudden burst of activity at Santorini Volcano in Greece:
    2011-11-26 20:39:02 2.6 10 Km
    2011-11-26 19:08:34 2.4 10 Km
    2011-11-24 16:22:41 2.3 5 Km
    2011-11-23 11:41:48 2.3 4 Km
    2011-11-22 22:56:48 2.6 11 Km
    2011-11-21 18:41:17 2.0 10 Km
    2011-11-19 02:40:26 2.4 23 Km
    2011-11-15 14:25:38 2.5 10 Km
    2011-11-14 23:42:20 2.1 1 Km
    2011-11-14 15:47:52 3.0 17 Km
    Would it be possible for those of you that know about these things to explain to me about whether or not this is something to worry about or just a Supervolcano having a cough! Thank you in advance, Victoria x

    1. I do not monitor volcanoes in Greece and I know little about them. But this is a active volcano. How knows what it might be up to. But I am sure that it is not something that needs to be worried about.

      1. Additionally, during the Minoan eruption (that destroyed the Minoan culture approx. 1650 BC) is estimated to have erupted approx. 50-60 km3 is ejecta. The Pinatubo eruption on 1991 erupted about 10 km3 of ejecta. For a supervolcanic eruption, at least approx. 500 km3 of ejecta is needed.

        So, Santorini is not a supervolcano. It is only “as small as Pinatubo is”. 😉

      2. Isn’t the term supervolcano eruption commonly used for the VEI 8 rated eruptions and at least 1000km3 of erupted material?

      3. Yes, but there are always uncertainties in determining the erupted volume. Hence the limit value differs between authors. I intended to give a safe lower limit for the “at least”.

    2. Well, I can tell you that they lock up the Santorini quake catalog quite well. I can’t do any historical pulls on their small quakes or conduct any trend or graphic analysis.

      My guess is that they don’t want anyone to have an independent look at their volcano.

      1. This is a list that contains some of the quakes and updates from a grid set about 1o k N,S,E and W of the caldera. Took about five tries.

        2011-11-29 15:41:15.6 36.43 N 25.47 E 20 2.7 DODECANESE ISLANDS, GREECE
        2011-11-29 15:36:48.6 36.42 N 25.41 E 2 2.3 DODECANESE ISLANDS, GREECE
        2011-11-24 16:22:41.0 36.41 N 25.42 E 5 2.3 DODECANESE ISLANDS, GREECE
        2011-11-23 11:41:48.8 36.42 N 25.43 E 4 2.3 DODECANESE ISLANDS, GREECE
        2011-11-14 23:42:19.0 36.41 N 25.38 E 1 2.3 DODECANESE ISLANDS, GREECE
        2011-11-14 23:01:21.1 36.42 N 25.43 E 7 2.7 DODECANESE ISLANDS, GREECE
        2011-11-14 09:33:21.0 36.40 N 25.40 E 4 2.8 DODECANESE ISLANDS, GREECE

        Search on USGS came up empty.

  4. Look at la Restinga webcam now. The middle one shows a lot of material floating on the sea but the lower one has just started showing what looks like a new jacuzzi, can anyone else see it?
    A white patch to the left of the picture and close to the edge. Wasn’t there half an hour ago. Wonder if it is a new vent?

  5. Can someone please tell me what the massive mound is in the La Restinga Harbour? Where’s has it come from and what is it for? At first I thought it was a cinder cone!

    1. Thank you! For a moment I thought they may have been planning on filling in our Bob! 8-o

    2. Most of these roads are in the north or east of the country. People normally travel more to Reykjavík and around the capital area or to the south of the country at this time of year.

      But anyway, take a fourwheeler with spikes and talk to the natives about current weather conditions in the area you’d like to go to. 🙂

  6. oops that should be 8 +-+O or eight plus dash plus capital O 😯
    Sorry about OT but I needed to sort it out.
    blush. 😳

    1. ummm anyone know what might be causing that ? or could it be a glitch/echo type thing ?

      1. It is very regular. First a short burst with one pulse every 15 seconds or so, then a much longer run at about one pulse every 2 minutes. I can’t imagine a natural process that would do that. On the other hand, that oceanographic ship has been in the area. I wonder if they are using an air canon to generate pulses, and monitoring the echos from the seabed and below.

      2. Yes, earthquakes can produce such regular signals. That’s why in this very specific case they’re called “drumbeats”.
        This one seems to be very typical, with a short burst of a high number of very small earthquakes, becoming more regular in frequency as time passes.

        They aren’t necessarily related with volcanic activity, but they might be since we’re speaking of El Hierro. Also, I don’t want to fuel speculations, but it could be the indication of a slow, but progressing magma intrusion into shallow ground as rock stress gets slowly relieved in a semi-self-controlled way.

      3. I would go with natural tremor signals. This is apparently a well documented phenomena in other volcanic areas.

    2. I think it is from the boat
      “El Sarmiento de Gamboa va a realizar unos perfiles de sísmica multicanal (una penetració…n bajo el fondo de más de 15 km). ” (from the blog todogeologica.com)
      “The Sarmiento de Gamboa will perform a multichannel seismic profiles (a penetration below the bottom … n more than 15 km).”

      More information (spanish):

  7. Supervolcanoes are eruptions larger than 1000 km3 (VEI8).
    In this cathegory, we have the most recent Lake Taupo 26000 years ago (1100 km3) and Toba 75000 years ago (2800 km3) which nearly caused our extinction. Toba eruption was actually larger than the largest Yellowstone eruption (2500 km3), and we survived.

    Interestingly, Lake Taupo seems to erupt often (geologically speaking). The last large eruption was in the year 180 AC, with an eruption as large as Tambora (VEI7, 120 km3), but more violent (with a third of ejecta erupted within the first minutes !!!). It turned the sky red over Rome (on the other side of the planet). These eruptions are about a tenth of the size of Lake Taupo or twenty times smaller than Toba.

    Santorini was a perhaps near VEI7, with at least 100 km3 of ejecta (source wikipedia), actually the size of the Minoan eruption was initially underestimated by scientists. That was 4 times larger than VEI6 Krakatoa (22 km3) but only a bit smaller than VEI7 Tambora in 1815 (160 km3) and the former spoken Lake Taupo.

    Krakatoa also seems to have large eruptions quite often. It is theorized that Krakatoa was the responsible for the large climatic disruption after 535, which was a disruption much larger than the one following Tambora.

    To put this into further comparison:
    – Paraná traps 8000km3, 132 M years ago
    – La Guarita 5000km3, 27 M years ago
    – Toba 2800 km3, 75.000 years ago
    – Yellowstone 2500 km3
    – Lake Taupo 1100 km3, 26.000 years ago

    – Tambora 160km3
    – Lake Taupo 120 km3
    – Santorini 100km3

    – Krakatoa 22 km3
    – Laki 15 km3
    – Pinatubo ~10 km3
    – Bardarbunga 1477 /Oraefajokull 1362 ~10km3

    – Katla 1km3 (usually)
    – Mt St Helens 1km3

    – Grimsvotn 0.7km3 (2011)
    – Eyjafjallajokull 0.3km3 (2010)

    This can put things into comparison!

  8. It’s nice to share… so here ya go.

    First the wedge in the direction of the two small quakes out under the El Julan slide area.


    Now the calculated and interpolated S-wave speeds for quakes inside that wedge (in white) that occurred in November.


    These speeds apply to the region inside the wedge at below about 15 km. I can’t go any shallower with out introducing a lot more uncertainty in the data. As it is, the quakes that contributed their phases have depth accuracies of about 4.6 km.

    This means that you this isn’t hard and fast, but it’s about as good as you can get with the available data.

    1. Interesting: not too sure of the geography but it looks as though there may be something hot in the top left corner.

    1. Or maybe a long effusive eruption will continue. A weak one, but lasting long. Like in Hawaii.

  9. off-topic: its very cold now in Iceland. about -10ºC and conditions to go way lower. Also a strong freezing wind.

    expect several frost quakes

  10. I saw the ship hauling a device with a cable and consistent with performing a seismic mapping of the eruption area.
    Will the station (CHIE) on El Hierro pick up the seismic signals generated by the seismic shooting of the ship?
    I wonder at what detail level they will get for det sub surface mapping.

    1. a close station should be able to pick it up, it will be a much broader band signal than a regular earthquake … would expect freqs up to 50-70 Hz, or more

      1. would EGOM pick it up though? And it did pick up the drumbeat signal, thats why i find it hard to imagine it was generated by a ship!

      2. I wonder.
        1 instrumental artificats.
        2. Station being in dense populated area of Teneor, where lots of water wells. Borhole Pumps or other man maid. Hard to belive this has anything to do with El Hierro

      3. That’s interesting Wagabond. I just measured from center of Eh Hierra to center of Gomera. 85km. Possible then.

      4. Yes it was hard to belive as I had to us > 100 kg dynamite to reach just 60 km.
        Part of it is that they have very good control over the pulse shape and f.spectrum by those tools.
        I think most of the seismic energy comes from the “implosion” when ehe expanded gas bobble collapses.

      5. seismic can travel far in water, after all i think Iceland listening station picked up the destruction of the USS Scorpian nuclear submarine in the azores in the late 60s

      6. Now THAT really is far. And of course I was forgetting about it travelling through water but was just thinking of it travelling through the earth.

      7. i think i should have said Iceland and North-east (Maine ? ,and or Newfoundland?) North America, as the U.S. Navy actually triangulated the position and last path of the Scorpion as it was dying (some controversy why it died, a bad torpedo running hot internally (bad battery design) , or just maybe a Soviet reprisal for ….) , any-ways, lots of fun reading (google it)

      8. i have no problems believing it could, i will talk to my buddies in marine seismic processing downstairs tomorrow to make sure (if i get a chance ..)

      9. My only issue, is the loss in transferring of energy from water to ground. I know it happens in T-waves, but I have no idea of the amount of loss of signal strength when that occurs.

        At about 1.5 km/s, if you could localize an artifact in the CHIE signal and then find it in the EGOM spectra, the travel time should indicate a water transmission. If it’s seismic then apparent speeds of 3.5 km/s or faster should be evident.

        I can find the seismic distance if anyone wants to take up the look for artifacts in both spectra.

      10. It is known that al low energy sound from subs and whales can travel hundreds of miles along the so callesd “SOFAR” layer in the oceans. (Google please :))
        I think we ar talking here about the P wave travelling in a similar matter along highest velocity layer along the crust (by refraction if you like) given the deapth/distance proportions.
        I must state that Im no expert on this, but I happened to act as as shotmaster for many geophysical projects for the last 35 years.

      11. well , we use seismic sources in water to image the subsurface all the time… the issue would be how much energy is lost by the time P-Wave gets to Gomera .. coupling should be reasonable/good through ocean/land interface … I think if seismometer reasonably close to ocean, no real problem (can’t prove it though …)

  11. Thanks for your answers ladies and gents! x
    I was looking at the RSOE EDIS site which lists Santorini under the ‘Supervolcano Monitoring System’ not the standard volcano list x

    but you have taught me loads in just a day – Thank you xxx

    1. That site is a bit of the scaremongering type, it would be better to steer away from it.

  12. Good morning everyone.
    Those are speculations , mostly.
    Ramon Margalef is underway and will arrive at Bob ~ 05:00
    For ? Multichannel sonar, chemical /gas sampling ??
    Sarmiento de Gamboa is on the north side probably doing deep seismic reflection measurement + Gravity, Magnetic.
    Regretably it is probably in a shadow from the AIS responder in Velverde just like seems to happen in the La Restinga area.

  13. Good morning everyone. Checked El Hierro seismic charts this morning and those drum beat signals were clearly there again during the night. Would the ship really be working with seismic surveys during the night? Is it that urgent? Check these charts between o2 and 04 hours.
    On the other hand are thry just too regular to be natural?

    1. With a large seismic vessel charging up towards USD 100 000 per day they are more than likely to run on a 24 hour schedule.

    2. 16 hours with no earthquake in el Hierro only the strange “drum beat” until now. 30/11 09:00 2.6 @ 23k

    1. This is from “The Bible”
      New Manual of Seismological Observatory Practice NMSOP
      Maybe heavy but even though I don’t understand the math’s there are lots of good explanations
      Take note of chapter 13
      CHAPTER 13: Volcano Seismology (J. Wassermann)
      Good site for downloading, chapter by chapter is:
      You can also search the manual on site.

      1. yup, somewhere between undergrad and grad level seismology , at least from what i can remember of it …

  14. Something is happening just outside the entrance to the La Restignia Harbour now, new vent of the right side?

    1. That bright oval mark on the general view, that looks a bit like a plume of steam? I think that is just a reflection of the sun off the camera lens.

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