Volcanic unrest in Iceland

Fagradalsfjall, image from ferlir.is

Iceland suffers from eruptions on average every 3 to 7 years. And in between we tend to look at other volcanoes with interest. And as time goes by we forget that Iceland at any time can have larger and faster eruptions than pretty much any other spot on earth.

During this phase of volcanic unrest we got a lesson about the breakneck pace that Iceland can put in during a period of volcanic unrest. At other volcanoes we can at a sedate pace follow volcanic intrusions and magma movement counted in anything from 100 meters per day, to a kilometre, or so.

But, once more, we are talking about Iceland. And today we got that reminder as Iceland decided that 5 kilometres in about 4 hours is a good pace for magma to ascend. That is by all means a new world record.

Image from Icelandic Met Office.

This is also an intrusion that will give scientific data for the next few years, even if there will not be an eruption. The reason for this is that we have never seen a large powerful intrusion at a Mid Oceanic Ridge at such a well instrumented place. We already have accumulated more data today, than at all other places and intrusions put together at a Mid Oceanic Ridge.

We now know that the initial swarm rapidly transformed from tectonic earthquakes, via volcano-tectonic, to earthquakes consistent with moving magma in a surprisingly short timeframe. As such this is turning into a potential eruption, or a state of volcanic unrest.

This does not mean that it is certain that an eruption will occur, just that the conditions are there for an eruption, if the seismic crisis continues for a length of time. According to previous knowledge an eruption would still be days to weeks away, even for Iceland. But, today we learned that there is indeed a higher gear on occasion for Iceland to put in.

Drumplot by the Icelandic Met Office.

This means that we must shorten the timespan from the start of the intrusion to a possible eruption considerably, if it happens. The normal timespan is 2 days up to weeks, months, or even years. In this case it is though more likely that it would continue at speed.

As such an eruption could be just hours to days away. That being said. If the current unrest stops in the next few hours there will be no eruption, at least for now. In that case we would end up with a Herðubreið situation with continuous small swarms, that ever so slowly moves magma towards the surface at the weakest point.

My personal musings

Let me state that it is the Icelandic Met Office that will make the call, and then it is up to the police and the Almannavarnadeild ríkislögreglustjóra to communicate and enforce it. They are the authorities in charge. I repeat, those are the ones to declare officially what is happening.

That being said, it is time to write what I think is going to happen. Currently the intrusion may end without an eruption. But, at the intensity and force of the current seismic unrest it is likely that an eruption will occur if the seismic crisis is prolonged.

If the earthquake swarm continues at this level an eruption could occur at any time from 8 hours to 72 hours from now. But, remember the IF here.

If an eruption would occur it would almost certainly not be explosive, at worst a VEI-1 to VEI-2. Instead it would be effusive with a fissure opening that could be anything from 500 meters to several kilometres in length.

Lava fountains would be between 100 to 700 metres in height, but fairly rapidly the fissure would shorten to one or a few main craters. At the same time, the eruptive rate would diminish to something between 50 to 500 cubic metres per second.

Intrusion viewed from North/South. Image by Andrej Flis.

Eruptions in this area are known to last for quite some time, so an eruption could cause problems for the road leading from the airport and nearby residents for a prolonged time.

If I was forced to put numbers to a likelihood for an eruption I would say that it is currently below 50 percent, but that number is increasing by the hour. If the hubbub is still going at this rate in the morning I would give a higher number.

We will be following this event closely if it continues, and we hope to publish new seismic plots tomorrow as IMO divulge new data.

Happy volcano watching unto all!

CARL REHNBERG

https://www.facebook.com/Almannavarnir/

 

181 thoughts on “Volcanic unrest in Iceland

  1. I should be arriving at Keflavik on Wednesday morning for a twelve day trundle around the country anti-clockwise. It looks as though the trip could be even more interesting than expected!

  2. Carl, have you chosen which hat will be sacrificed under the watchful eye of the dalek cam? Looks like the odds that the BBQ coals might need lighting soon has increased 😀

    I’ve got 4 weeks of leave to use before the end of the year, think I’ll be looking for cheap flights to Iceland at this rate.

    • Tony the Scar is probably going to whack Steve the Sleeve… Otherwise there are not that much in the news as of today.

  3. As an extreme volcano enthusiast, I can truly tell you that each and every word you’ve written here is absolute bullshit.

    We see these swarms, these exact swarms, each and every year in south-west Iceland. This is Tectonic/Magma unrest at its finest, different from the rest, but well known to us. This is a relatively small swarm when compared to the swarms we’ve had in the past 20 odd years. This is a highly active area which is constantly being torn apart, and while it’s volcanically active, I can honestly tell you that We’re not going to experience an eruption here until we get a groundbreaking earthquake.

    As to the “magma moving upwards”, these are the plates tearing apart. They’re not going to break apart beneath the surface and leave those gaps open, are they? Sure, magma Might try to force its way in there. But it will take a helluva lot more than what you seem to be aiming at. As for the “eruption within hours”, absolutely ridiculous, and clueless.

    To be clear on what I’m getting at: I’m Icelandic. I experience all this shit every day. Swarms bigger than this one, almost every year. Nothing is indicating a possible eruption in the near future, since this is the most active part of Iceland for earthquake swarms, you can expect to see at least 10 of these swarms before it can even be considered a possibility that it might pop.

    As for which volcano this belongs to: Krýsuvík is a very large volcanic ridge with tens of mountains to its name, among those, Fagradalsfjall.

    Magma movement=debunked.

    Held up for approval by the system (always happens for first-time commenters). Hereby released. Your opinions are welcome but be aware of our first rule: ‘be nice’ – admin

    • I Might add, since you also went into detail about how shallow the earthquakes were getting: Most of the earthquakes located on the Reykjanes peninsula are at depths between 1.5-4km. Not an interesting plot line, for sure. But something to reconsider, given that this is all normal here. No two parts of the world are the same when it comes to earthquakes, tectonic swarms and general unrest. This is unique. And we know it well.

      • Your questions are perfectly valid, but as a user of this site, can I ask you to tone down the language?
        I read these posts precisely because they do NOT play any sensationalist games. If in doubt… I don’t know how many previous posts you have followed, but I would suggest you have a look if you have not done so already.
        Those such as myself who are not experts in any way could learn a great deal from a more respectful discussion between yourself and others, as you clearly take a contrary view.
        There is absolutely nothing wrong with such a stance, especially when it is founded on evidence , or as in your case, experience of actually living there.
        Thank you.

      • And your point exactly is? Well, the same as I made.
        In the plot you would notice that the stack formed between 10 and 4.5 kilometres. Significantly deeper than your shallow tectonic swarms. It is the depth that is intriguing.

    • Your opinions are appreciated, and of course there was indeed no eruption. I am also aware that swarms like this have happened before in this region (western side of the Reykjanes peninsula), albeit not at this particular location, and they tend to last two days reaching up to M4. The eastern side has single, much bigger earthquakes so clearly the western rift is better lubricated. The signal did show that fluid was involved, and magma movement was implied. And note that the initial swarm was focussed in an area of barely 100 by 100 meter, and started out deep. (Much deeper than 4 km.) That looked like a stack, a volcanic warning sign. Later, the depths became much more uniform and the location started to migrate. There are a lot of short faults here perpendicular to the rift, and I guess one (two?) of those broke.

      I wouldn’t be too convinced that nothing will happen here, ever. Up to 1300AD, eruptions were frequent in this area. Something changed, perhaps a shortage of magma. Doesn’t mean it will stay that way!

      The post mentions that an eruption is (was) far from certain, and was more cautious than perhaps yit was given credit for. The UK newspaper that broke the story did not cite those cautions.

      We try not to cry wolf. You will note we have not pushed the story of the possible eruption yesterday at Katla. We are sure it will erupt (properly) and is in the process of building up to it. Same for Hekla.
      We discuss these indications, but do not predict the end of the world!

      I hope you will continue to contribute.

    • I will for the sake of argument answer your comments and explain things. After all you have a few points.
      Of course there have been quite a few swarms in the last 20 years and far longer back than that, but for swarms older than 20 years we at best have spotty instrumental data. Some of them have been larger, and many of them have followed the same tectonic transforming into magma-tectonic regime. I didn’t in any way write anything else did I?
      Instead, what caught my eye is that there has been no swarm at this exact location. And that is what I found intriguing.
      The tearing apart bottoms upwards is exactly what a dyke intrusion entails. There is no magma above the MOHO here (with the few exceptions where there are residual pockets of magma from previous intrusions). This is the classical dyke-intrusion model, do not argue with me about it, it is after all the classical model in science.
      In regards of it needing 10 intrusions to form an eruption, the point here is exactly that we do not know that. Nobody alive has seen an eruption here. Instead we can only go on what instrumented data says, and in this case it said rapid magma movement upwards from the MOHO. Fast enough to make it into a possibility that an eruption would be possible.
      Now to Krysuvik. Volcanoes are often lumped together due to vicinity to each other, but there is no real data on them being the same actual volcano. During seismic crisis and eruptions it is not uncommon that this changes. During Holuhraun this happened, prior to the eruption it was believed to be Askja, now we know it was Bárdarbunga. Same thing here, no earthquake pointed towards a relation to the central volcano of Krysuvik, instead we saw a separate feeding mechanism form.

      Magma movement = debunked. Sorry, but the instrumental data is poking a hole here in your reasoning. At 13.55.10 on 2017-07-26 a M3.9 earthquake started that turned into a 2 minute 40 second long HT-coda of the earthquake, as such making it highly probable that magma started to move. Several earthquakes after that also where of VT-type. I am sorry to say that magma moved, nature and instruments proved that.

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