Here comes Katla?

By John Conway | July 20, 2010 4:43 pm

Being kind of a volcano/earthquake geek, I regularly check in on the recent California earthquake records, the Kilauea activity, and, in the past couple months since the Eyjafjallajokull, the earthquake activity near it that might presage an eruption of Eyja’s big sister, Katla. Historically, eruptions of Eyjafjallajokull are followed by eruptions of Katla, which are an order of magnitude larger. The eruption of Eyjafjallajokull disrupted air travel in Europe for weeks. It’s interesting to consider what a big volcano Katla might do. There is also the fact that Katla erupts every 40-80 years and hasn’t erupted since 1918, making this a potentially bigger buildup to an eruption. Some of the Katla eruptions in the past have gone on for months.

Since I have been watching, the number of earthquakes near Katla has been small, with a few periods of a dozen or so within a 24 hour period. Almost every time I have looked it’s been very quiet, perhaps one or two a day. I was away the previous two weeks, and apparently missed a day with 11 earthquakes on July 10. I checked again today, and I got the map below, with over a dozen earthquakes! Now, clearly, these are all small earthquakes, with magnitude near 1, and there are no reports of steam or ash as yet.

I bet it’s coming, though, fairly soon. The president of Iceland does, too.


  • Andy J

    One of the Eruptions bloggers is saying it’s probably not imminent:

    “I am no expert on seismicity at Katla, but most of of the current earthquakes are very shallow (1 km or less), small (most < M1) and really, only 14 in the past day. If you're looking for a signal of a reawakening Katla, we should expect increasing magnitudes, earthquakes starting at depth (10s of km) and working their way upwards, tens if not hundreds of earthquakes a day and volcanic tremors, all of which are missing right now."

    (I agree with what you've said – that it will erupt in the near future, just thought I'd post this in case anyone thought "soon" meant "this week")

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  • Erik Klemetti

    Yeah, no. The number of earthquakes is only part of the picture. The depth and trend of the quakes is much more important. I’m betting these current earthquakes have much more to do with the ice load on the volcano – all the quakes are ~1 km depth – pretty shallow.

  • Smiler

    I’ve just checked this and it’s not correct to say that all of the quakes are around 1km deep. Out of the 16 showing this morning, two were at 5km depth, one at 11km and another at 24.3km depth (although admittedly the epicentre of this final one was located a few km away from the main group). Also, reading the guidance for using these figures, it explains that, if there is more than one earthquake at the same time, the combined magnitude is equivalent to a larger earthquake than the raw individual data measurements state.

    Having said that, I agree that a lot of the movement is probably due to the Myrdalsjokull glacier on top of the volcano shifting. Iceland is currently in its “midnight sun” season with near 24 hour daylight, and they are having one of their warmest summers for years. So there is likely to be more melt than usual from the glacier. If you look at the Katla webcam, you can see that the ice covering, which was quite visible on that side a few weeks ago, has all but disappeared which would seem to support this.

  • Mark P

    Well, once it happens I guess we can look forward to some dramatic sunsets, at least in the northern hemisphere.

  • A

    Once Katla erupts later this year Europe will become Earth’s second moon.

  • Edwards

    I’ll be nice and just say that if you are going to comment that something is going to erupt ‘fairly soon’, perhaps you should quantify what that means. For the general populace it could means days. For those of a more scientific bent on geology, years..decades?

  • John

    I have tried to find out what the interval between the three previous Eyjafjallajokull eruptions with subsequent Katla eruptions was, but haven’t found that yet.

    I think it’s clearly difficult to predict whether it will be days, weeks, months, or a year. A wild-ass guess would be weeks to months, though, rather than years.

    Though it could be sooner – I would note that there has been no letup in the rate of deep (5 km or deeper) earthquakes of magnitude 1 or greater for the past several days!

    I think it will be spectacular when it does happen.

  • onymous

    I solipsistically predict that it will erupt the next time I’m in Europe, about a month from now, thus trapping me even more successfully than Eyjafjallajökull did in April.

  • RexAlan

    Well onymous I would say your probably right. Murphies law determines all chance, apart from Russia where it’s known as the Sandwich Law. Meaning whichever way you drop your bread it always lands butter down!

  • Ramenth

    The general delay between Katla and – Guðnasteinn, the other volcano under Eyjafjallajokull that just erupted, is believed to be somewhere between 8 months and 3 years, according to teh intarwebs.

    of course, given that we’re all watching it, it probably wont happen on that schedule. Is a volcano really that different than a pot of water?

  • Michael

    According to Shakespeare, Julius Caesar was warned to “Beware the Ides of March”.

    I wonder if that applies to volcanoes too?

    Anyway… my guess would be March 15, 2011.

    Seriously… I’ve been watching the earthquake data too.

    Swarms? Yes.

    Sufficient magnitude? No.

    Depth? Only check that when “smater-than-me” guys mention it in their blog responses.

    Stay tuned.

    Mýrdalsjökull – earthquakes during the last 48 hours:

  • Ian

    I agree it will go soon, but for me soon will be either within the next 3 months or in about a year. I read (can’t find the source – sorry!) that it has always erupted in Autumn (Fall for the Americans) from what they can tell.
    Based on that and the increasing activity, I guess it is coming. However, before Eyjafjallajokull erupted, there were reports of hundreds to thousands of earthquakes per day. Seeing as Katla is much bigger, surely that’s the least we can expect when an eruption is imminent?

  • Julie

    With the iminent eruption I cannot believe there is no ‘plan’. Living in Scotland it really concerns me and I am going to stock up on some masks so at least I can go outside when the air around me looks like Moscow’s does just now. I think the UK government is stupid to ignore Iceland’s President and I will lol at them when they go running to him for advice once the emergency has begun, when the emergency planning information was available to them all along. They really have NO IDEA what is coming. I can’t begin to imagine what it will do to Europe. If the effects will be visual in California, it’s pretty scary for a Scot.

  • Stuart Vyse

    first of all its important to note that I LOVE GEOLOGY and that i tend to not stop going on about something so good luck reading this! I believe that a careful eye should be noted on Katla over the next few months. i have been monitoring strain, earthquake and tremor measurements over the past few months after being in Iceland when the volcano erupted (actually less than 11miles away in Dyrholaey). during my studies i have noted that their has been a stark increase in the frequency and magnitude of earthquakes and earthquake swarms at the katla volcano over the following months. the significance of their shallow focus may be of 2 causes. 1 the annual fluctuations in glacial weight caused by the ovelying myrd… icecap. and the influence of magma intruding beneath the caldera producing shallow-focus harmonic tremors. any more increases in these shallow focus earthquakes could indicate rapid intrusion of magma. what everyone should be watching for aswell as these are longer-period earthquakes that are indicative of gaseous build up in the magma chamber creating enormous pressures. i believe that attention should largely be focused on the WESTERN FLANK of Katla that has shown the most earthquakes than anywhere else on the volcano. careful note should also be taken in changes of the overlying icecap. as proved in previous eruptions. geothermal activity is shown to cause deep depressions in the ice due to melting of the ice below. causing localised “glacial outbursts” as the melted water below bursts through ice dams. we know from previous eruptions of Katla that it erupts on the VEI scale of 4+ on most occasions. e.g. pelean/plinian. this can produce an eruption column of between 10km to 25km in height. whereas an eruption of 3 e.g. the previous eruption at eyja….. kull produces typically between 3-15km in height. devastation once again for the airline industry. it is also important to note the effect of the magmatic differentiation at katla. we know that katla typically erupts every 40-60 years. katla hasn’t majorly erupted since 1918. the eruption may be more than 4 as the long period of magmatic differentiation may create larger amounts of andesitic lava and perhaps trachytic magma which are silicic and intermediate lavas that are much more viscous than toothpaste making it hard for gases to escape. EXPLOSIVE!!!!. on the plus side though scotland will get some beautiful sunsets!
    Stuart Vyse- 17


    I am a father of 5 and have been following your conversations about Katla for some time and have to thank you for some great and to the point info..most sites I’ve visited often sound like prophetic doomsayers….I find it refreshing to hear an open minded and mostly educational side to the story…We homeschool our children and to follow natural occurences like this from their beginings is more educational and awe inspiring then any book can offer…..thanks again to all of you…jb

  • John

    Thanks for all the great comments – since my post, there has not been a day without a dozen-ish earthquakes under Katla. If you click on the tab that says “Table” it lists the characteristics of the earthquakes, including their depth. Many are quite deep, 5 or more km. I have not seen any above 2 in magnitude yet. I have no idea how to interpret this but it definitely looks different since mid-July than it did previously. I do think it’s a matter of when, not if, Katla will blow and when it does I bet it will indeed be very disruptive for air travel.

    Come on leaders! Now is the time to prepare!

  • monkeywrench

    “Come on leaders! Now is the time to prepare!”

    Unfortunately I’m afraid all of out leaders have their heads stuck in the sand. All they seem to be concerned about is a temporary disruption of air traffic in Europe. They seem to be totally oblivious to the fact that a large eruption of Katla could lower temperatures enough to cause crop failures in the Northern Hemisphere. Not to mention Russia just lost most of its crops due to drought and fire. We’re kind of ‘running on empty’ already….

  • Ian

    Stuart Vyse:
    The fact that the majority of earthquakes take place on the Western flank could indicate magma flows between Eyja and Katla, as opposed to where it will eventually erupt, could it not?
    Wouldn’t this explain the link between the two volcanoes? When Eyja erupts, it somehow breaches Katla (hence the Western earthquakes), and “tops it up” with magma triggering an eruption from it’s bigger brother?

    I agree entirely, just look at what happened in 1755.

  • Stuart Vyse

    it could well be, i was just intrigued to still see that the majority of earthquakes are on the western flank even after the eruption has stopped. it could well be the effects of the magma link between the 2 volcanoes. i don’t know the ins and outs of the eyja and katla volcanoes. i’m just a school geology student at the moment and i’m fascinated by everything geology related. but we must not forget that everything should be considered! geology is not always by the books.

  • dirk bruere

    If Katla looks like erupting, buy shares in ferry companies!


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