Posted on by Jón Frímann

Bárðarbunga volcano weekly update for 25-February-2015

There hasn’t been a lot of new information about the eruption in Holuhraun this week. Earthquake activity continues in Bárðarbunga volcano as before, but at slower rate and earthquake with magnitude 3,0 and larger have almost stopped at the moment.

150225_1415
Earthquake activity in Bárðarbunga volcano for the past 48 hours, no earthquake above magnitude 3,0 has been recorded for the past few days. Copyright of this image belongs to Icelandic Met Office.

Earthquake activity continues in Bárðarbunga volcano, but at far lower level than just few weeks ago. Subsidence has slowed down considerably at the moment. It has not stopped. There are earthquakes along the dyke from Bárðarbunga volcano, suggesting that pressure might be increasing in it. That in it self might not lead to a new eruption.

The eruption in Holuhraun continues, but at low level. The only remaining vent that is now open is building a new crater inside the big crater that has now stopped erupting. The eruption might continue at this low level for many more months. Current status of the eruption is not known due to extremely bad weather in Iceland at the moment. The eruption is not over, it is however really small at the moment.

Due to bad weather I am expecting that my geophones might go offline due to loss of power or other connection problems that might happen due to this bad weather. Information about the storm can be found here. This is not a weather to travel outside. If you are in Iceland, stay where you are and don’t travel until the weather has passed over Iceland.

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Article updated at 16:35 UTC.

39 Replies to “Bárðarbunga volcano weekly update for 25-February-2015”

    2. Hi Lukas, where are the new pictures. I have seen those months ago, and these are from the very beginning of the eruption. Any recent pictures? Would be great!

    1. I understand it’s probably due to wind, but still it looks more like EQs to my rather untrained eye.

    1. Looks to me like a spike in water height. It shows also at Húsbondi station http://hraun.vedur.is/ja/vatnajokulsvoktun/hus1_trem.gif

      Interestingly, the hydrologic measurements show this also (Núpsvötn) at around the same time. And they also show (1 mánuður) still higher levels on the 2.Feb. – if the measurements are correct, the water height then rose within just 1-2 hrs. by around 5 meters in the river Núpsvötn on the Skeiðarársandur. On the other hand, the specialists warn that ice is very probably disrupting measurements at the moment, …

  4. Hi!
    Something I just found out, or think I have. 🙂
    The strainmeter-graph of Hekla:
    http://hraun.vedur.is/ja/hekla/thensla_hekla.html
    fits nearly perfect to something, which is linked on the same page.
    Here http://www.heklubyggd.is/vedur.htm you find a barometer-graph.
    This one: http://www.heklubyggd.is/vedur/BarometerHistory.gif

    So the quick fall of the strainmeter is 1 to 1 related to airpressure. (Strong low pressure system arriving.)
    Sorry, if you have already known that, but it was new to me.

    2. Interesting find. A computer could subtract one from the other, I suppose, to show a flattened, corrected measure?

    3. I would be very surprised, since the units are deployed into deep holes specifically to avoid environmental influences. I monitor the uncorrected data out of personal interest, however the IMO corrected data takes account of any anomalies and is very accurate. Borehole strain gauges are usually 2 to 3 orders of magnitude more accurate than GPS derived high rate strain data.

      There has been discussion in here also of the accuracy of subsidence readings from bb. This is what the IMO have told me –
      “The accuracy varies depending on atmospheric- and on site- conditions, but generally we have good location constrained within few cm. Although there are (usually short lived) periods where you have few meters of scatter. But over time periods spanning minutes and hours we have location accuracy within 10 cm or so.

      the reference station is the Continous GPS site in Vonarskarð VONC approximately (15 km away from it)”

      I hope this helps and thank the IMO for their help.

    1. Hi Jon
      Arriving in iceland tomorrow morning, is the weather still likely to be bad then and is the expecation that there will be road travel problems? Rout 1 east.
      Noticed that yesterday the helicopter trip to the eruption are being reduced because of customer complaints that the lava and eruption is now very small. Some even asking for payment rebates such was their disappointment.

  6. Heklubyggð geophone is offline due to some technical problem. I don’t know what is wrong, but I can’t log-on into the computer that handles this task. I don’t know when it is going to be fixed.

  7. @Jon…or others

    How can you tell if earthquakes in the dike are due to increase in pressure…or due to relaxation due to loss of pressure (which would have been my interpretation due to loss of outflow at eruption site)

    1. Your question includes already the answer. As we have a strong decrease of volume in the dike, the earthquakes can’t really be coming from pressure, rather from cooling and retraction.

    3. When magma flows freely eqs are reduced, when it is constrained pressure increases and so do eqs. Rock being an excellent insulator, I doubt that cooling is likely to cause them.

      1. Well, if you take into account that we had a rather sudden temperature drop from large heat exchange of constant magma flow in the dike of lately 50-70 m3 when we still had a lava lake, to now now more magma flow in the dyke with very limited heat exchange (no more flow), cooling can’t be discarded, as contraction of the rock walls must happen with rather sudden temperature decrease. The dyke might even be sucked empty (back flow) so I’m not sure about your explanation of earthquakes still coming from pressure increase in the dyke, Scots John

      2. I’m not criticising stefan, the temperature drop only needs to be gradual for crystalline fractionalisation which will close it up by deposition, as it closes near the surface in an Icelandic winter then the surface area will harden. The magma beneath holuhraun and enroute to source will remain very hot for a long time.

        You mention back draining and that cannot be ruled out, but would not generate earthquakes in these patterns. I personally think there is pressure, but that does not mean a resurgence from any area along the dike, it may cause higher pressure elsewhere in the veidvotn system. Jon has already pointed that out.

        The bad weather is a pain as the accuracy of data is compromised, but IMO are doing a good job processing this. I see subsidence is back on stream. Nothing is set in stone though and opinions are just that.

      3. In this case we cannot talk about crystalline fractionation, as this is a much slower process in a magma chamber. Here we talk about fast cooling (in geologic time frame extremely fast) in a dike which is a couple of meters wide. The result is fine grained basalt. The weather has no influence on the earthquake measurements along the dike as we can see a clear pattern of distribution. When you have a back drain, you sort of create an empty space where just a couple of days ago was a constant magma flow in the dike with pressure built up. So, empty space has to be compensated, most probably by little earthquakes and movement of the rock walls. We will see in the next days how these little earthquakes will show up along the dike. This is a new interesting episode and we might see and interpret new things which haven’t been seen before like that. I mean the propagation of the dike away from BB at the very beginning. Have a good night, I go sleep now 😉

      4. I’m curious Stefan, Bowen was able to produce these reactive series under lab conditions in the 1900’s over very short periods, on what basis do you think this could not have happened at holuhraun?

      5. Hi John, we can go on and on. Crystal fractionation (that’s how it’s written) is happening in magma chambers or larger sills. It does not apply to a narrow dyke. The numerous dikes I have seen in the field (I’m talking about many hundreds) were fine grained volcanic rocks. For sure you can have the odd dyke with larger phenocrysts, but those then originated from earlier crystal fractionation in the source magma chamber feeding the dike. Like we might have Olivin crystals in the fine grained basalt of Holuhraun. Experiments are often done under different parameters and different (small) scale. So I wouldn’t compare Bowen to actual field geology.

      6. The latter process, and please note the spelling –

        http://www.umanitoba.ca/faculties/science/geological_sciences/faculty/sherriff/website/277/05/Lecture%2012%20magma.htm

        It is this process I am speaking of at the surface, not in the dyke itself. Hence the dyke can remain active whilst its outlet has sealed itself off.

        I hope we can have a conversation without correcting each others spelling. The spell corrector when I use my tablets is insane and frequently interferes with my spelling.

    1. It appears to have happened a power supply problem in the seismometer twice during the night. (Before and after midnight.)
      Every time power comes back, there is, for that very second, a strong noise signal.
      —> http://hraun.vedur.is/ja/drumplot/djk.png
      These false signals show up, too, in the plot you linked to.

  11. On the IMO site they wrote about that in helicopter flight today they didnt see anything. It seemed that the eruption has stoped. But there is still gas coming from the eruption site

  13. Icelandic Met Office just made it official.

    The eruption in Holuhraun, which began 31 August 2014, has come to an end.

    The area continues to be closely monitored.
    Gas contamination is still detected around the eruption site.
    No changes have been made to the restricted area north of Vatnajökull.
    The Civil Protection still operates in alert phase.
    Aviation Colour Code for Bárðarbunga has been downgraded from orange to yellow.

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