Grindavik dropping into the sea

Mount Thorbjorn


Like minds and all, both me and Albert set out to write an update article unbeknownst to each other. I guess that Albert has not yet fully come to grips with me returning back to “life”. But, this is a good thing for you as a reader, you get twice the fun from two different minds as a nice weekend surprise.

Albert is the top part of the article, and I will be down far into the bottom.


Thorbjörn Update by Albert

Credit: Astrograph. Click here to see a high resolution 360 degree panorama in Google Maps of Grindavik, taken on 4th July 2021, with the first Fagra eruption in the background

O what a night.. At the last count, there were 252 earthquake of magnitude 3 or more, the largest at M5.2. That is 252 stars on the map, scattered all over the place as the automatic locator cannot cope with this amount of shaking. It is Christmas come early, with 252 stars of Grindavik. The evacuation of Grindavik adds another semblance of that first Christmas story. But so far, it is a lot of noise but no action. The magma has (so far) remained underground.

To recall, this all started with inflation over an area centred roughly on Thorbjorn, ‘child of Thor’. Thor, according to wikipedia, is a “hammer-wielding god associated with lightning, thunder, storms, sacred groves and trees, strength, the protection of humankind, hallowing, and fertility”. We get our name for Thursday from it. There is certainly a lot of thunder and hallowing going on at the moment – but the protection of humankind has been deferred to the lesser gods of the Icelandic authorities. They are rather good at it and overnight they evacuated both Grindavik and the power plant. Work to protect both against future lava flows has been started, by building embankments of several meters high. It worked for the flows two years ago, although in one case only because the lava did not actually reach the wall. The sign ‘lava – no access’ appeared to be sufficient. The risk, of course, is that a wall may deflect lava onto some other property, raising questions of liability. But not knowing where lava will surface makes planning more difficult.

The following map was uncovered by one of our commenters. It shows how far lava needs to travel to get to Grindavik from various locations. At the moment there is no ‘most likely’ location along the rift. The further north, the better, obviously.

It started mid October when inflation took off. A sill formed with an inflow of 5 m3/s. Over three weeks, that amounts to 10 million m3, or 0.01 km3. It added to previous intrusions which had been happening since 2020.

Why a sill? A sill is a horizontal magma layer, which pushes up the layers above it. This is what is causing the earthquakes and the inflation. The earthquakes happened at 5-6 km depth, suggesting the sill was just below this. How does it form? Magma in rock has to find a weakness, a crack where it can insert itself. This can happen at a place where two different layers connect, for instance where the lava pile which has build Reykjanes lies on top of the oceanic crust below. The two are already a bit separate and magma can prise them apart. This happened over an area of up to a few square kilometer: the sill would have been 10-20 meters thick, in my estimation. There is minor magma around than is in the sill: it has a feeder system below although we don’t seem to know where this feeder is.

Yesterday the sill found another weakness. To move up, it has top break rock and that is not easy in such an old, cold lava pile. So it looks for another connection which goes up. This can be a fault, but in this case it found something else: an old fissure system. The fissure sits on top of an ancient dike, and this dike means there is a vertical discontinuity between the rock and the dike. The first earthquakes along the fissure were several days ago, but yesterday it took off. The magma began to build a new dike along the side of the old one.

The magma moved up by 1-2 km but mostly moved sideways. The dikes here run along the direction of the rift, which in Iceland is SSW-NNE. Because of the spreading, it is easier for magma to insert itself in this direction. And now it went fast. As of this morning, the dike extended over 18 km, from a few kilometer off short to far in-land. That does not mean the magma has traveled all this distance. It means that the old fissure dike is breaking away from the surrounding rock.

So where is the magma? The GPS shows an indications. As this morning, Thorbjorn has sunk by 40 cm. This happened because the dike is forcing the rock apart. That the sinking is so much indicates the magma has shallowed. How shallow? My guess is 2 km but it is only a guess. Both Grindavik and Thorbjorn are moving northwest, but that is harder to interpret. Where would an eruption be? Impossible to tell. It can be anywhere along the line. The highest probability is in the original location which is east of the Blue Lagoon. There is a bit of a gap in the earthquakes and that can be a sign – or not. The second probability is indicated by the deflation – that would put the eruption in the harbour of Grindavik!

RUV put out the following (again taken from a comment)

The signs of magma movement include significant subsidence in the Sundhnúkur craters, indicating that the magma might be shallow below the surface.

The southern end of the crater row is about 1 km from the nearest buildings in Grindavík and approximately 1500 meters from the Svartsengi power plant.

The Icelandic Meteorological Office notes a substantial change in seismic activity, moving south towards the town of Grindavík. According to the Icelandic Meteorological Office, there is a likelihood that magma movement has extended beneath the town of Grindavík.

The volume of magma involved is considerably larger than seen in the major magma intrusions related to the eruptions at Fagradalsfjall.”

Here is the onset of activity, with M2+ magnitudes twice per minute at one point.

An interferogram (thanks Gaz!)

And here is a list of cameras mentioned by our contributors






View of power plant from Thorbjorn

A Thorbjorn view

A multiview

Live from Iceland has views all over iceland, including:

Fagradalsfjall and

Albert, 11 Nov 2023


Grindavik update by Carl

Grindavik, photograph taken by VC FB regular Roman Zacharij and used under Wikimedia Commons.

I promised everyone an update today, so here is an update about why I and every other volcanologist should go and drink some tea and ponder why we underestimated a volcanic risk. I will get back to this below.

This will mainly just be an update that I will edit as things unfurl, and I will throw in a little prognosis of what will happen, and where it will happen, based upon the situation at 11.00 Icelandic Time on Saturday.


Short Recap

Roughly two weeks ago Thorbjörn started to show signs of an eruption being possible as a secondary intrusion started, and a sill formed where magma accumulated.

On Sunday evening I felt confident that the prerequisites for an eruption was there based on GPS-data, spectrography over seismic data, earthquake locationing, etcetera.

And based on that data I pointed at a possible location for the eruption to break out, if activity had continued like that I would probably not have been far off, nor would IMO either, we are after all talking about as little as 800 meters between assumed centroids from our individual models.

IMO weighted GPS-data higher than I did, I tend to weight Earthquake-locationing higher. Both methodologies are solidly based on science, and give similar results most often, well similar enough to give an 800-meter difference. Something that in the greater scheme of things is not a lot.

Earthquake map by the Icelandic Met Office. Note that there are loads of “ghost-earthquakes” that never happened, this is caused by over-saturation of the system by signal reflections.

Yesterday at around 12.00 Icelandic time, Iceland decided to kick those models in the proverbial nuts and a dyke started to form that was NNE/SSW trending, putting the most likely location of breakout at Sundhnukagigar, East of Bláa Lonid (Blue Lagoon) and the Svartsengi Powerplant.

This later led to the powerplant evacuating the workers and going into remote controlled operations after some sort of minor accident that was probably caused by strong earthquake activity.

That part of the formative dyke rapidly stalled out, and the bulk of the activity switched down the other dyke leg towards Grindavik.

This forced the evacuation of Grindavik Town itself, a decision that was proven to be a very good idea, but perhaps not for the reason it was based on.

Right now, the dyke is hammering away South of Grindavik in under the sea.


What We Forgot

Let us leave aside the risk for an eruption, and the earthquakes, and even the dyke, and instead look at another side-effect of the earthquakes and the propagating and dilating dyke.

Iceland is truly spectacularly good at moving about, it is extending itself in all sorts of interesting tectonic ways. Faults spread and drift apart, micro-plates dance about and rotate… it is a mess of simultaneous movement.

One of those movements have a scientific name, and that is Graben-formation. It is when due to spreading-movement a lineament of land is dropping down into the void created by the spreading land.

Some Graben like the Eldgjá-Graben form sharp sides, and if you have your house on the exact spot where that side form your house will start to lean, or even fall on its side. But if your house is in the middle of the forming graben you might end up with your house remaining perfectly straight if you are lucky.

This happens in large caldera volcanoes; I saw a house topple over in Amatítlan in Guatemala in a single night from this phenomenon. So, obviously it is well known thing among volcanologists, and something we take into our risk-calculations.

This time though it had an effect that I am pretty certain that nobody had considered, but that we will do in the future when applicable.

Let us phrase it as a question. What happens if a Graben form under a town adjacent to the ocean, and the Graben continues extensionally into said ocean?

Let us begin with numbers as of 11.00 Icelandic time, the Graben has dilated 120cm and the Graben floor has dropped a whopping 96cm (I will edit this as often as I can).

This means that conversely the ocean level has risen permanently 96cm in Grindavik. Obviously, it is not the water level that has risen, it is the town that has dropped.

Grindavik is built so that 96cm is not drowning houses, there is a margin to account for storm surges etcetera, but that margin has shrunk with said 96cm, meaning that storms are more likely to cause flooding along the shoreline and in the port.

Obviously, this is now. If the Graben continue to widen and drop it will get worse.

My favourite Graben in Iceland is Eldgjá, it is 8.5km long, 600 meters wide and 150 meters deep. Obviously the Grindavik-Graben will not become nearly that wide and deep, but a meter or two more depth is obviously not out of the question.

So, there is an idea to look at those Volcanic Hazard Maps and see if another town is at risk of Grabening itself into The Big Fishtank in the Ocean.



Station GRIC 4-hour solution. Image from Sigún Hreinsdottir’s page.

Remember that this is based on data at 11.00 on Saturday, so take into account that conditions could change with time, it is a snapshot of “now”, and based on future trends that are realistic and congruent with previous eruptions of similar nature in Iceland.

I am writing the above paragraph so that even Charles Gregory can understand, hopefully, that a prognosis changes over time and with shifting data. I do though not have great hope of that.

Eruptions are statistical games based on data, and the length of a dyke is indicative of where it will erupt. Thorbjörns dyke has two dyke-legs based on the breakout point (feeder), the shorter leg is the one running East of Bláa Lonid, and the longer leg is running out into the ocean south of Grindavik.

On a purely statistical standpoint it is more likely that a longer dyke-leg will encounter a weakness that the magma can use to pop up to the surface.

What we know so far is that the Northern leg up to now remains dry (uneruptive), but there are faults that way that may in turn end turn up to be the weakest spot along the dyke.

There are also faults and weaknesses on the longer Grindavik leg of the dilating dyke, but they are a bit more spaced out. There is though one thing that is probably going to affect things more than everything else.

It is that the ground level is constantly dropping as the Grindavik dyke-leg extends and dip its Grabening foot into the water. This means that the distance a breakout needs to travel to the surface is decreasing since the overburden become increasingly thin.

Let us assume that the top of the sheet-dyke is 2km deep at the breakout point from the sill near Bláa Lonid, as the dyke goes south in Grindavik the height of the overburden drops around the point it hits the water and it slowly get deeper until it hits the continental shelf, and it drops below the top of the dyke. But the continental shelf margin is quite some ways out.

On top of that the Graben itself is fertile ground for an eruption to pop up, and on Graben margins you often get a formation of a crater row, see Eldgjá and Lakí just as a couple of examples.

In other words, based on current data a breakout is most likely from about a kilometre north of Grindavik down to a couple of kilometres out into the ocean.

As magma rushed into the dyke, overall systemic pressure has dropped, so for the moment the pressure is probably somewhat to low for continued lengthwise progress, and to form an upwards directed conduit, but the last is depending on how firm the overburden is and how much resistance it can put up.

Eldgjá Graben, photograph by Andreas Tille, Wikimedia Commons.

The diminishing systemic pressure is why we are seeing a drop in the amount and strength of the earthquakes (11.00), it is though still quite impressive.

As magma continue to enter the system from the bottom feeder conduit from the mantle pressure will though go up, and we will get increased activity again, and probably the expected breakout. This can happen anytime from a few hours, up to a few days.

But, at this point it is pretty much a sure thing that something will pop up.

Here I would like to make a point, normally the initial breakout is 10-20 percent from the furthest point of dyke propagation, it is not clearly understood why really, it might have to do with some sort of fluid-dynamic hammer-effect, but why and how is not well understood as I said.

If that will turn out to be true here, we will see the eruption start outside of the port. It would be a tad ashy as it breaks the surface and “rooster-tails” form, but as soon as it is above the surface ashfall will rapidly decrease.

In other words, do not expect the end of the world, well perhaps the fishermen of Grindavik have a different opinion, for them it might end up as the end of the world.

I have seen people “biggying up” the upcoming eruption to proportions it just can’t take. No, it will not be even remotely near the size of Holuhraun. That being said, judging from magma-influx and previous eruptions a likely figure would be a peak average discharge rate doubling that of Fagradal eruptions.

If memory serves that was 40 cubic meters per second during the fountaining phase of Fagradal II eruption, so perhaps as high as 80 cubic meters per second during the peak hour, and then slowly falling to 10 to 20 cubic meters per second.

If we assume the length of the eruptive episode to be somewhat equal of Fagradal eruptions, we end up with an eruption at around 0.1km3, and that is not a bad figure as sizes go. In other words, it will most likely be a fairly impressive tourist eruption, but nothing more.

If the influx is steady and continue, we could end up with a longer eruption and the amount of magma would slowly climb upwards. At the extreme end of probability, we get a small shield formation that lasts for up to a century, but that is a very low probability indeed.

As a final thing I would mention that I seriously hope that Grindavik will be affected as little as possible, and that the lives of the inhabitants soon can return to normal.


P.S. Charles Gregory, “Told you so”. It is now the third time you have been rude and wrong and gotten “I told you so’d”. I suggest pulling in your attitude and stop trying to bully people. I am definitely unbullyable if nothing else.

1,132 thoughts on “Grindavik dropping into the sea

  1. Yesterday I came across the Insta page of Jürgen Merz named Fire and Ice. Jürgens accountname is glacionaut.

    He introduces his page as “Creative mindset documenting abstract landscapes of glaciers and volcanoes”.
    He has captured many retreating glaciers as the dramatic vanishing of the Pasterze. Also Ice and Fire themes are pictured in Iceland, some beautiful drone shots of Fagradalls Fires as well.

    Recommended when you’re tired of commenting or reading…. 😑 or just feeling sheepy 🐑🐑🐑…

    For those who don’t do Insta:

  2. The M3 earlier tonight was in the middle of the dike, close to Thorbjorn, and a bit shallower. It is far too early to talk down the chance of an eruption. The opening of the rift underneath the ocean create enough space to hold the intruded magma, but over time the rift can close a bit again and begins to squeeze the magma. If that happens, activity will increase again but more localized then before. The other option is that the sill reforms and at point re-opens its connection to the dike. That would be a slower process. The biggest problem for the population is the uncertainty.

    • If the magma is still flowing into the area where the sills were then it wont backflow that way, so if the rift starts closing off at the ends things could get quite dire. The most intense seismicity is just north of Grindavik, not far south of where the dike started from, an eruption would probably happen here.

    • With Geldingalir, the eruption occurred near the middle of the earthquake swarm, which had extended from Keilir to SW Fagradalsfjall (near to where FEFC is).

      How does the position of the current swarm compare to known local faults?

    • Hi Albert. Does the magma’s liquidity/pressure/temperature stay the same for months/years? Would this pose a thread for a long time? Laypersons like me would guess that things ‘calm down’ after a few weeks…

      • No real change in composition is expected over a time scale of weeks. But magma can solidiy, especially in thin dikes. A layer one meter thick without a heating source may solidify in a week, or slower once it has heated the surrounding rock.(Rock is an excellent insulator). In a long dike feeding an eruption, this can eventually end the eruption as happened in Holuhraun: once the flow rate is slow enough that it takes longer to traverse the dike than the time needed for solidifying, the magma freezes on the way and the eruption ends quite suddenly. (It may restart closer to the source but that did not happen in Holuhraun.) That is one reason not to expect an eruption at the very end point of the dike: the magma there is a thinner layer (otherwise it would have extended further) and quite quickly freezes. At the moment, the inflow into the dike seems to be on-going or has resumed, and that brings new heat so other than the end points, I expect that the magma will continue to be liquid. Note that convection will occur in magma (as long as the layer is thick enough), with hotter magma rising, so don’t expect the top to freeze first. The cooled liquid sinks to be re-heated. Gas bubble formation can also induce convection but if that happens we should see it on the tremor charts.

        One thing to be aware off: at the Fagradalsfjal eruption, season I, the individual eruption sites formed as doubles, with one twin exterminating or cannibalizing the other over time. I wonder whether that would happen here as well.

  3. How do the current sill and dyke interact with the previous one of 2020? I remember that there was an intrusion around Thorbjörn that didn’t erupt. But the cooling magma should still be there underground. This is the news about the events in Spring 2020:

    How much has the magma of 2020 cooled/evolved? Imagine that the new magma intrudes into the old dyke and pushes it out first. There were some historical eruptions which first had an output of old magma, before the new hot magma came out (f.e. Leilani Estates 2018 or some Hekla eruptions).

      • The center of the present graben is nearly the same location of the strongest uplift 2020. So it seems likely that the new magma meets the old magma somewhere somehow.

    • The lava of fissure 17 was cebturies old. The best guess is it originated in the Kahawali eruption that was somewhere between 1550 and 1650. A more common but probably less likely option is it was from 1924, or the 1950s. But even in that case it is about 60 years. The magma under þorbjorn was until a few days ago still at least 4 km deep and mostly under 3 years old, it most likely has not evolved at all.

      Hekla seems to evolve its magma at depth, which is pretty weird among volcanoes in its setting. It is probably why it erupts mostly effusive fast flowing lava despite it being andesitic, its very hot for that composition. Hekla does erupt basalt at some flank vents, its relationship with the neighboring Vatnafjoll volcano is unclear, but they are clearly interacting.

      • Hekla recently erupted frequently, so the last eruptions had relatively little evolved magma. The next eruption of Katla can be different. It’s now 105 years after the last eruption, and during 10th century Katla did many eruptions, after Reykjanes Fires began …

      • There is no known direct link beetween Hekla and Vatnafjöll.
        Hekla is though a bit problematic since it has several differenc magma reservoirs that it draws on.
        The flank eruptions are not really Hekla eruptions and are sourced directly from the mantle.

        Hekla also have the very weird distinction of being the only volcano that is basalt derived that was born as an ash only highly evolved magma volcano, and have over 7 millennia gone towards less evolved magma.
        And on top of that it holds the distinction of being the world’s only Stratofissure Volcano.

        It is one huge honking mindfuck of a volcano.

        • It is not the only stratofissure volcano, there is also Dubbi in Eritrea.

          I have read somewhere that the same Fe-Ti transitional basalt that Katla and Vatnafjoll erupt has been identified from part of Hekla, although predating most of the mountain it postdates the first silicic activity and was erupted from the Hekla fissure swarm and not elsewhere. More recent basalt is different.

  4. Yes I have a new article… its a general tour of the subject… later I will write more investigative stuff

  5. Department of Civil Protection and Emergency Management issued a warning for those entering the area, reminding people of the risks.

    „Eldgos er talið líklegt á svæðinu. Almenningur má alls ekki fara á einkabílum inn á það svæði sem talið er hættulegast sem teygir sig austur fyrir Víkurbraut. Eingöngu verður farið inn á það svæði í fylgd viðbraðgsaðila. Hratt landris mælist við Svartsengi.“

    “”Eruption is considered likely in the area. The general public must not drive private cars into the area that is considered the most dangerous, which stretches east of Víkurbraut. That area will only be entered when accompanied by a responder. Rapid inflation measured at Svartsengi.”

  6. Am I being a little premature in saying that the last 90 mins seems to be showing an uptick in seismicity ?
    It seems to me that the number and intensity of quakes has been dropping steadily over the last couple of days… until just over an hour ago.
    Any thoughts ?

    • Later after the eruption is over I could write a few articles about geothermal energy.
      And why some versions of it might not be a godsend, while other definitely are a godsend for humanity.

  7. Credit to Kristinn Magnusson and Iceland Geology | Seismic & Volcanic activity in Iceland


  8. Met Office: unchanged probability of eruption
    The Icelandic Met Office have just published the latest information and assessment.

    Since midnight, 700 earthquakes have been recorded across the magma intrusion, the largest of magnitude 3.1, at Hagafell.

    Last night there were also earthquakes at Kleifarvatn, the largest was a 3.8, at 9.09pm.

    The vast majority of earthquakes are at the magma intrusion, most of them small and at a depth of 3-5 km.

    Measurements show continued land movement. They are consistent with magma still flowing into the intrusion.

    The [magma] flow on 12 and 13 November was measured at 75 cubic meters per second, and the depth down to the magma is about 800 m. These numbers are based on model calculations and are subject to uncertainty.

    The main focus on seismicity monitoring is in the area of ​​the intrusion, and Grindavík. New GPS stations have been installed in the town and the surrounding area. They show that the sinkhole, or depression, that has formed is still active.

    The probability of an eruption is therefore still high. In the event of an eruption, the most likely location is, still, along the intrusion. There is no evidence of otherwise in the data.

    • Then it seems rather certain it will erupt somewhere, thats a rather high magma inflow

    • 75 m3/s and there is still inflation beind detected in the sill once more. Unless that signal is a false signal or a bad translation, this is pretty serious. There must be a lot if magma being dredged up from the depths of the volcano, or maybe this rift was in part fed by the magma accumulating under Fagradalsfjall before.

      It is a hard situation. I kind of want it to erupt now if only to remove any doubt. Grindavik is not safe to live in while this rift is active anyway and that may be the case for years.

      • I think the same (or nearby) sill was being intruded into over the past few years, it then reached a point where it needed to release pressure and formed the dike. It could well be that the next intrusion causes the eruption, and it isn’t yet at fully capacity. Either way bad news for Grindavikians as they are not going to be able to go back in the meanwhile.

        • If the sill deflated by outflow to the dike, wouldn’t that tend to reduce pressure overall, allowing an increased inflow rate?

        • That explains the ongoing and increasing damage that is Happening to houses in Grindavik, It makes me think it could be a very long time indeed before people can go back to some areas of the town.

      • There’s still a huge void to fill.
        It will probably take a week before pressure goes up again.

  9. The Thorbjorn Live from iceland camera did a pan on the summit next to the ‘clock’ and focused on some, what I assume to be fresh, substantial evidence of ground movement, huge long cracks, running the length of the mini escarpment. 11:20 14/11.

    • That side of the mountain is on the edge of the graben that is forming so that side is subsiding while the rest of the mountain is not..

      No idea how steep or tall the other side of the escarpment actually is but you have to wonder if there is now the chance for a very significant landslide to occur down into the valley on to the #43 roadway?

  10. Does anyone else get the feeling that things are getting pretty serious soon? With the land inflating again and the continued dropping of Grindavík something surely will happen.

  11. The Grindavik 8 hour time series showed a 270mm shift north during the recent event but is now moving back south by around 90mm since. Not sure quite how to interpret assuming my analysis is accurate.

    • Thorbjorn is moving back west at the same time. It could be a response to rifting along the graben. Grindavik is on the european side while Thorbjorn is on the north american side – the graben cuts along the Reykjanes fault to affect both sides. Or it could be magma movement in the central part of the dike. Or it could be relaxation after the sudden jumps. It is hard to tell.

  12. Volcano Watch 2023: Escorting Grindavík Residents Home For Essentials

    The Reykjavík Grapevine

    • I recommend this video!
      The film maker accompanies his parents to Grindavik to pick up their belongings. I can’t express how calm and composed people seem to be. Driving over big cracks in the road to pick up belonging from a home they don’t know they’ll ever see again.

      • It makes it very real. It’s interesting that the reporters parents said they left expecting not to go back so took more than others. And also saying they felt like the magma was moving under their feet during the shaking that didn’t stop was quite evocative. While everyone was calm, noone was hanging around more than they need to.

        Question for anyone here familiar with the pipes hot water – there was a shot of what looked like one of the hot water pipes that had lost a man hole cover and water was boiling in it. Would it be normal for the hot water in the pipes to be actually boiling?

        If not boiling then the only alternative I can think of is that it gas bubbling out. Surely either boiling water or gas bubbling is an indication that magma is very close to the surface?

        • Communal heating systems are often at 100C, or even slightly above if they are pressurised.
          The one I have at home is at 104C.

          So yes, it would happily boil if let out in larger volumes.

          • Thanks for the reply Carl. Useful to know. Bubbling water at the side of the road is not a common site for those of us not used to communal heating systems.

            I wonder how much damage boiling water leaking out of broken pipes might do to some houses? Water is the worst for damage (I’m not counting lava in my cohort of damaging items there!). But least of everyone’s concerns at the moment.

            Has there been any news from anyone about raised borehole temperatures from anywhere like we heard about before one of Fagradalsfjall eruptions? Is this something people will be looking out for or just was that just a coincidental anecdote?

        • The local utility company (for the entire peninsula) pricelist does include delivery temperatures of both 80°C and 90°C. I’m not sure which one is used in Grindavik.

  13. This is for Carl:

    I’m going to respond here, because the comment you made, which I took issue with was too deep.

    So here it is: this is not a Thorbjörn situation. Leave Thorbjörn alone! 🙂

    If anything, that huge blob of cold basalt is going to apply downwards pressure that will force magma to the sides. Hopefully towards the old fissure system called sudur-something.

    • I am using that name since it was where the initial intrusion began in 2019, and not based in any hatred against this, or any other Thorbjörn, au contraire I like my Thorbjörns. 🙂

  14. How well can we compare the present day with the days before Fagradalsfjall’s first eruption on March 19th 2021?

    Peak of earthquake activity was on March 10th with 2500 earthquakes. Afterwards it decreased to 400 earthquakes on March 18th. It took more than a week after the peak of swarming until the eruption began!

    On March 19th they wrote:
    “Earthquake activity in the region of the magma intrusion has been lower in recent days, and there is presently no intense seismicity occurring in the region. Earlier in the day, several low-frequency earthquakes were recorded below Fagradalsfjall”
    Were the low-frequency earthquakes a possible indicator for the later eruption?

  15. Icelandic breaking news

    Rescue teams are evacuating from the area.
    No reason pointed.
    But an eruption is even more likely now.

    I wonder what information or event made them evacuate suddenly.

    • See link below – “Met Office’s gas meters showed an increased SO2 value. “

      • So we do have gas meters there, just as Carl said. I bet that they have CO2 meters too. It would be very interesting to see the intensity measurements across the graben, that would be a good indicator of the proxmity of magma to the surface.

        • CO2 is more dangerous than SO2 that it has no smell and can build gas lakes in depressions or cellars where humans and animals can get suffocation. A very famous threat in Wine Cellars …

        • CO2 was the cause of the only death during Eldfell eruption at Heimaey as a drug adict broke into a pharmacy and went into the basement where apparently “the hipper stuff” was stored.

    • Does SO2 smell like the smell of fireworks? Burning Black Powder releases SO2 as well as volcanoes.

        • That’s H2S that smells like rotten eggs, not S02. S02 smells like a burnt match.

          • From experience of it in the absence of the other things you get from a burnt match ( unfortunately) i’d say rotten eggs is a fair description albeit a rather acrid version, odour is always rather subjective however. The smell from fireworks is very much the sulphur present being oxidised.

          • @Swebby

            Thanks. I stand corrected. I had always understood H2S as having the “rotten eggs” smell, but from your comments I guess that S20 can have that as well.

          • No worries, H2S is indeed a proper rotten egg smell and is the thing you tend to smell if you visit a volcanic site. Nearly all volatile sulphur compounds are “eggy/rotten” to a greater or lesser extent – i.e “sulphury” but as i say, it is subjective for each individual.

  16. They are evacuating Grindavík as we speak. Volcanic gas has been detected in the area.

    • They say sulfur.. then magma is just below the surface .. looks like an eruption is pretty certain ( almost )

      • Does it say any quantities being measured (tonnes/day)? I remember Taal regularly doing 9000+, different system of course

        • I interpret the (translated) text, that the SO2 meters are new, i.e. as soon as they were used they measured SO2 – the SO2 might have been present for some time, and it has just now being measured… so maybe not a sudden change…

          • I would be incredibly surprised if they had let residents in without checking SO2 levels first so I am assuming this is a change.

          • If it had been present for sometime, residents would have been complaining about it; it is not pleasant even in small quantities. So my guess is that it is relatively new (at least since Friday night when they initially evacuated).

          • the measuring devices were installed two days ago, and are powered using solar cells (!!!) as sunlight, and even daylight is sparse in this corner of the world they only work for a short amout of time each day. Due to this circumstances it cannot be determined if today more gas has been present than yesterday. (summarized from:

          • Apparently they first detected it yesterday and again today. They describe the instruments as having been installed “earlier this week” which I presume was longer ago than yesterday. So my guess is that when they initially installed and commissioned the system they didn’t see SO2. However they could clarify this a bit more. They do point out a possibility of it coming from elsewhere due to change in wind direction.


            Earlier this week, IMO specialists installed two DOAS remote sensing instruments on Húsafell. These instruments can measure the presence and the amount of SO2 in the atmosphere. One of the DOAS instruments detected SO2 yesterday and today at the newly formed graben, located between Sundhnúkagígar and Grindavík. Because of the low amount of daylight, the measurements can be imprecise, and it took time to review the data and interpret it. In the last two days, eastern winds have been prevalent in the area, so it cannot be ruled out that recent strong seismicity has caused the release of SO2 from beneath Fagardalsfjall, as magma at that location has not solidified yet since the eruption in July 2023.

          • Astrograph:
            Not sure that these are really solar-powered.
            Those might be MAX-DOAS (“multi axis differential”) measurements, which is a variant that requires actual sunlight for the measurement process itself, not just for power.

            However, to set up a MAX-DOAS in November in Iceland does seem slightly weird, even weirder than solar powering an active DOAS. But maybe it was the only device available?

          • There were some that refused to evacuate the Volcano island in 2020. One died if I recall. Fortunately Icelanders aren’t as silly

        • Icelandic volcanoes tend to be the gassiest mommas on the planet, so I would expect a lot as the eruption starts, but right now my guess would be less than 1000MT per day.

    • Be prepared for a lot of burning moss, buildings and steam/smoke on the cams… heart goes to people of Grindavik.

    • On the new gas meters, not the older ones, but they said they were taking precautions anyway.

      • Agreed. SO2 is a pretty familiar smell in much of Iceland (it was evident occasionally in Grindavik last summer), even tap water smells of it sometimes, so it would have been newly installed meters that caused the concern.

  17. Grindavík town is undergoing a swift evacuation as a precautionary measure due to elevated sulfur dioxide levels detected by the meteorological office. The police chief in Suðurnes has confirmed the ongoing evacuation for safety reasons, emphasizing that it is not an emergency evacuation, and residents are required to leave the area promptly.

    • Is Grindavík the only site where SO2 has been detected? & is the SO2 from under Grindavík or is being blown in from nearby?

    • I have the impression that the Webcam already shows some vog, but it also could be meterological mist due to rain. The rain drops on the webcam cause optical illusions.

  18. Iceland is going to build (Dutch) dykes around critical infrastructure now, after Iceland’s parliament decided so yesterday. They expect to do so around Powerplants and the Blue Lagoon. It looks like a quasi-experiment whether this well help …

    • It saved the road during Fagra II if nothing else.
      And, Vikings tend to want to fight stuff in a very direct manner, so they will start with building dirt walls, and end up spraying water on the oncomming magma.

      So far it is Vikings 2, volcano silch.

  19. Sometimes the translation of Icelandic fails catastrophically …

    “The emergency responders have gathered with all their sea urchins in the parking lot at Fagradalsfjall. They are now awaiting decisions on next steps.”

    Honestly, I wouldn’t know either what to do with those urchins. 😀

    • Those images are of Litli-Hrutur in July 23. And the fissure is longer than those of Fagradalsfjall 21 and 22.

      If an eruption begins under the sea it’ll be ashy – which irrc Carl mentioned in his post. On land it could be like Litli-Hrutur, but much will depend on where it starts and on the flow rate. But I am not a scientist, let alone any kind of earth scientist, so take this with appropriate caution.

  20. In reading recent comments, I came across this opinion “since the earthquake activity has resumed back down to the 5 km depth at the transition zone between brittle and ductile, the magma will flow into sills, so we’re safe now as that is what is happening” I am a bit dubious about this? It seems plausible, but I believe we still have a lot of mushy magma in the dike yet. Your opinion about this assertion?

    • My take on that is that magma is still feeding into the system, and therefore exploring the limits of the rock around it. Some additional, low-level rock cracking is inevitable.

  21. What does it mean, sulfur emissions? Where there sulfur emissions before? Did they increase?:
    “The release of gases acts as both a warning sign and an effect of volcanic eruptions. Their release can indicate an eruption is soon to follow; however, the contents of the gases should be closely monitored because many active volcanoes steadily release gases even when not close to erupting. Changes in composition can be indicative of an impending eruption. For example, just two weeks before Mount Pinatubo in the Philippines erupted in June 1991, the sulphur dioxide content in the emitted gases increased roughly tenfold.”

    Tenfold for Pinatubo.
    When the measuring station is new nobody might know the increase. On the island of Ischia and Campi Flegrei SO2 is emitted all the time.

    This is an earthquake zone belonging to the South Iceland Seismic Zone (SISZ/RP), western part,
    figure 6, link. So, panicking is justified, but not necessarily for a possibly effusive eruption, rather for a larger earthquake San Francisco style.

    When I emptied my empty bottle today….
    Some things are bad reporting. Was Grindavik evacuated or not? How can you evacuate a place that has been evacuated before like my bottle yesterday?

    The article is from 2006, but as brillant as an old bottle of Château Lafite Rothschild, one of the authors Páll Einarsson, PDF, free download, concerning the MAR figure 2, seismis zone figure 6:

    • Seems that news spread even if it is not news and if it is news even if it is wrong. And if it is new and right then in the wrong way and if …

      • exactly, and the MSM still confuses Iceland with Norway, and still cannot get its geography correct flashing pictures of the Litli-Hrutur fissure eruption and claiming it’s Fragradalsfall volcano erupting, so many things wrong in the MSM about this episode.

    • They were asking the people, who were allowed back in briefly to collect pets and belongings, to promptly leave before the actual deadline. From RUV:

      (This morning)
      “Today’s plan for controlled return to Grindavík
      The police chief in Suðurnes has published a plan for how people and companies can save valuables from Grindavík. Special emphasis is placed on the fact that the schedule can change without notice and that only those residents who did not make it yesterday will be allowed to enter the town. Businesses are now operating in the town and have time to do so until 12 o’clock. From 12pm to 4pm residents can go home. Each household gets 5 minutes.”

      (This afternoon)
      “Sulfur dioxide measured in the atmosphere at Grindavík is an indication that the magma lies very shallow. The town was evacuated just before 3pm when new meters from the Icelandic Met Office recorded elevated levels of the gas.”

      – Precautionary measures based on the SO2 reading; although it was acknowledged that the SO2 could have been blown from degassing lava at Fagra on an easterly wind. They weren’t going to take the risk, regardless of source, timeframe or amount due to the underlying dyke.

      From the paper you linked:
      “The westernmost part of the peninsula, i.e. from Kleifarvatn to west is characterized by intensive swarm episodes, where normal faulting earthquakes are frequent. The largest magnitudes observed there are estimated around 5.5, and it is assumed probable that they will not exceed that limit.”

      Grindavik is in this area of the RP zone, within it a fair way to the West. An obliquely spreading part of the mid-Atlantic plate boundary with normal faulting. So the main risk is without doubt from volcanic eruptions due to the spreading nature here, and especially with a large dyke now underneath it, rather than the transform fault derived large earthquakes that occur mainly in the SISZ and, to a limited extent, in the eastern part of the RP zone.

  22. Today’s quakes (this time with Krisuvikis). You can save the gif and let it run outside the rbowser to get an endless loop.

    • Yeah, let it lie where it wants to lie. The decisive question is was there an increase in the emission of SO2?

  23. About the meters, copied from RUV:

    The meters were installed two days ago and use sunlight for measurements, so they are only useful for a small part of the day now in the middle of November. There is therefore not extensive reference data to build on. It is therefore not clear that the gas is there to a greater extent than yesterday.

    • That may be slightly misleading as IMO says they detected SO2 beginning yesterday but that was only analysed and confirmed today.

    • Seltún, geothermal area, 25 km east of Grindavik, near Krýsuvík:

      Solfataras, fumaroles, mudpots and hot springs

  24. While Thorbjörn is in cliffhanger mode, we have time to see what HVO says in last daily update:
    “the Sand Hill tiltmeter, located southwest of the caldera, has paused over last 24 hours suggesting inflation of a source south of Halemaʻumaʻu. Overall, the summit of Kīlauea remains at a high level of inflation, above the level reached prior to the most recent eruption in September 2023.”

    Also MANE station near “Hilina Palina Road” has vital deformation:


  25. Tuesday
    14.11.2023 18:26:20 63.866 -22.411 0.9 km 0.7 90.01 3.4 km NNE of Grindavík
    It could be interesting if this small (micro?) quake gets proven.

    • There was a confirmed one nine hours ago, 3,6 in the Reykjanes Ridge, 19 km WSW of Grindavik, nearest volcano Eldey, submarine.

    • If you see strange lights on that cam it is almost always the geothermal plant.

    • If it’s the Thorbjorn cam it could be the workers building the defensive wall around the geothermal plant in their CATs (or JCBs). You’ll know if it’s volcanic because there’ll be a flood of bright light shoots straight up in the air and flickers like a flame, that is if it doesn’t erupt through Thorbjorn and kill the cameras…

      • I reckon you are correct there Andy. There are a lot of headlights from what look like large trucks.

    • This is indeed interesting:
      “erupted within a 400 year period, between about 940 and 1340. The series began in the east, in the Brennisteinsfjöll volcanic system, with a series of eruptions, a few decades apart and ending before 1200. After 1150 eruptions began further west, in Krisuvik, also lasting until about 1200. Now the Svartsengi and Reykjanes systems joined in with a series of eruptions, from 1211 to 1240. The 1226 eruption was part of this group. Then it all ended, and the area has remained quiet ever since.
      This behaviour of progressive eruptions turned out to be typical. There had been a similar series of eruption 1000 years earlier – and the same another 1000 years before that, and again before that one. In this region, eruptions move from the east to the west over several hundred years, terminate, followed by 700 years of volcanic sleep before it restarts.”

  26. New IMO update

    Updated 14. November at 19:20 UTC

    Earlier this week, IMO specialists installed two DOAS remote sensing instruments on Húsafell. These instruments can measure the presence and the amount of SO2 in the atmosphere. One of the DOAS instruments detected SO2 yesterday and today at the newly formed graben, located between Sundhnúkagígar and Grindavík. Because of the low amount of daylight, the measurements can be imprecise, and it took time to review the data and interpret it. In the last two days, eastern winds have been prevalent in the area, so it cannot be ruled out that recent strong seismicity has caused the release of SO2 from beneath Fagardalsfjall, as magma at that location has not solidified yet since the eruption in July 2023.

    It is hard to estimate the depth from which the SO2 is being released as the process is influenced by magma pressure. However, it is thought that the magma needs to be in the upper hundred meters of the crust in order for SO2 to be released. This is one of the reasons why the DOAS instruments have been sited close to Grindavík.

    DOAS (Differential Optical Absorption Spectrometer) is a tool that can detect sulfur dioxide in the atmosphere. The method relies on visible light, which travels through the atmosphere, hits a sensor in the measuring device, which is then analyzed for certain colors (wavelengths) that are missing from the spectrum. Sulfur dioxide absorbs certain wavelengths of light, which means that light hits the measuring instrument in a different way if SO2 is detected. The probe scans certain sectors of the sky, and it provides information on the concentration of sulfur dioxide within the area scanned. DOAS measurements need daylight to work, so operating such instruments in the wintertime in Iceland can be challenging.

    • Thanks for sharing!

      Now a stupid question: why can’t they set up a directional, full spectrum light source on a neighbouring mountain and point at the sensor?

      Wouldn’t this produce the necessary light for the gas to absorb? 🙂

        • SO2 absorption is as you know in the UV around 310nm. Most commercial spectrometers are for column amounts in the atmosphere (pollution etc) so this would have to be a specific bit of kit for purpose but probably can/has been done

        • Yes, so based on the description it really seems to be a MAX DOAS device, which does require sunlight to operate (in the previous post I was speculating about this only).

          It is a bit strange to use one of those in November in Iceland, so presumably they had only those around at the time, from some measurement campaign in the summer.

          I suspect you can not easily convert a MAX DOAS to an active DOAS (the types that use lamps), because the collection optics are going to be a bit different.

          And even if you could, the lamps that are used for this type of measurement seem to be quite hard to get by – I once witnessed a project being cancelled because the necessary light bulb could not be obtained in time (with many weeks lead time). That was long ago though, not sure how the situation would be now.

          I have always wondered though, whether, when in a pinch you could jerry-rig something with an aviation landing light or similar (before they all went LED).

          • Actually, I guess I have to correct myself already – passive DOAS yes, but not MAX (multi axis), if the picture that showed up on Facebook is correct, which claims to show the two devices that they set up.
            Those are pretty much the most straightforward possible DOAS setups; single axis detectors from the looks of it, and also presumably passive, so only for daylight use.

            The issue with optical SO2 detection is that it is normally done in the ultraviolet as mentioned before, thus not just any old lightbulb will do unfortunately. But if this is how they do it here, also this means that for low sun angles I would expect the UV availability from sunlight to also be very low – making measurements in Iceland even harder at this time of the year, even when the sun is up.

          • Yes, extremely difficult measurements at low sun angle (lower than 30 deg above the horizon). A bright artificial light source at this wavelength would be dangerous to people, or at least to their eyes

          • It would be possible, but very difficult to achieve the required light intensity on a large area with artificial bulbs, especially in the UV part of the spectrum. This is usually achieved with deuterium lamps and they are very expensive (I work with such lamps on a daily basis in my laboratory).

            And as Albert pointed out, the irradiation of a large area with high intensity UV lamps would be very harmful in close proximity to the lamps.

            For a focused measurement on a very small area, artificial light sources are a good option, though.

          • Tanning bed tubes.

            Those go down to 300-odd nm and they might be quite abundant in a subarctic, cloudy place like Iceland …

    • Perhaps Jesper it is better to wait as then people will not be so preoccupied and will likely appreciate you article more then. Sometimes waiting has benefits. I am often tempted to buy something when I see it but when I wait and research the item I can find a better quality item for cheaper, Waiting is always easier when you are older though and you are young.

    • Yes Jesper, as I’ve said to you a few times now. I appreciate you’re keen to have your article published, but the situation in Iceland is a higher priority at the moment and we haven’t even uploaded and reviewed it yet. We dragons are a bit busy balancing daily lives and answering VC comments at the moment. If things calm down in Iceland, or if a possible eruption continues for a long period of time without significant changes, then we’ll publish it. You’ll be the first to know when there’s a suitable time to blast off to Io. 🙂

      “Patience you must have, my young Padawan.” – Yoda

    • According to MBL, these are members of the SAR teams that have been given permission to enter town to get their own personal stuff. These folks have been very busy lately so they have no been able so far to visit their own homes like most locals have been able to.

      • Thanks. Looks like most are leaving now by the road on the far left of the picture.

  27. My apologies if this has been already posted on VC, geophysicist Páll Einarsson said that there is a good possibility that nothing is going to happen. (yesterday’s news) He stated that in the Krafla eruptions 1975-1984 there were 20 dike intrusion episodes but only 9 reached the surface and the 2 biggest events were duds.(no magma release)

  28. I couldn’t find it in the comments, but someone pointed out that the graben subsidence scarp is visible in the 1950s photos of Grindavik on – before they built over it.

    The latest update from the Icelandic Met Office refers to “The newly activated graben”.

    Well done, Holmes!

    • The clue’s in the “The newly activated graben” quote – The (existing) graben, that’s been newly activated (and made larger and deeper). Now please pass my deerstalker, Watson… 😉

      • There is also the big graben in Thorbjorn itself! Small grabens are common on Reykjanes but this one is very wide. Grabens can reactivate quite easily, given nearby magma. The Eldgja eruption occured in a deep graben that predated the eruption. I also noticed that the cracks in some places in Grindavik followed the side of the road. Presumably what gave way was the fill-in used to bury the hot water pipes.

    • For those interested, for example this one: never ceases to amaze me.

  29. Does anyone know whether there has been any high-resolution photogrammetry being done in the area recently? Like, has their survey aircraft been spotted flying around there?

    After all, the relevant area is quite small and has been pretty much well-defined for several weeks now. I wonder if they sent the survey aircraft with the LIDAR, or iwth the cameras, or alternatively the drones that they seemed to have used in the later phases of the previous two eruptions, to survey the area – that would make it possible to really precisely map the deformations now, like the new graben, and during future deformation phases. Would be amazing to have that data in combination with all the other stuff int his very well instrumented active zone.

  30. Irreparable Damage Already and Sadness – Grindavik Awaits the Final Chapter

    Just Icelandic

    • Some Icelanders compared it with Christchurch. There the quake was more severe, but also more deep.

    • Wow, I just posted this, but for some reason the graphic did not appear. I am glad that you posted too.

      • When you post a youtube link and want it to auto-embed don’t put any text after the link – so the youtube link must be the last line on its own.

  31. I’m going to start with a disclaimer that I’m not a geologist or volcanologist (different kind of -ologist, but with an unhelpful science background) nor am I an expert on geothermal plants. I’m also not new here, though I rarely post at all. I tend to lurk whenever Iceland starts another eruption and have been around since 2014.

    The evacuation due to volcanic gases got me wondering today, though, and I haven’t seen something along the lines mentioned. Maybe it’s way out there and totally ridiculous. Feel free to tell me – straight and blunt 🙂

    SO² is getting measured in an around Grindavík in a concetration that is obviously worrisome enough to tell people to get out of there faster than originally planned. SO² is related to magma relatively close to the surface. We know that there’s a magma sill currently refilling underneath the power plant in Svartsengi. We also know that plant provides electricity and hot water for Grindavík (among other places). Grindavík has lots of broken hot water pipes.
    So we have a power plant with bore holes (??) down to where magma may or may not be collecting fairly close to the surface. We have a broken pipe system. We have SO² in the air. Is there a connection? Does the power plant – which as I understand is not turned off, just set to an automated work modus – dredge up the volcanic gas in a higher than usual amount and is it getting released through the broken pipes? Is that even a remote possibility?

    • That is an interesting suggestion. Effectively the power plant would act as a fumarole distributor. I think the amounts you’d get from the hot water in Grindavik would not give a significant concentration in the outside air – an Iceland is quite windy. The detector will be looking south, over the sea (direction of the sun..) so not see across much land. The SO2 will be local, and the concentration was evidently high enough to raise concerns. If there is a broken pipe right in front of the detector, I guess this should be considered. Otherwise, I expect we are seeing degassing from the magma

      • Just minor comment: I believe you would not point DOAS towards the sun (certainly not at it), but more like 90 degrees from it. Might be different for close to surface measurements though.
        The picture looks like these two particular devices are pointing towards the west or south west, measuring along a line crossing the “graben” north of the city.

        But since somewhere in a video (Just Icelandic if memory serves) it was reported that SO2 was detected close to a specific house or housing area, there are clearly more devices around.

    • The thing is that the hot water piped from Svartsengi is not coming driectly from the deep boreholes. The deep boreholes supply steam that is used to heat up ground water through heat exchangers. This groundwater is retrieved from much shallower holes in the area and does not come into contact with the stuff from the deep. Also, it would be noticed in Keflavik as well if hot water from Svartsengi was suddenly carrying SO2.

      • thank you for posting this. S02 in steam is actually quite corrosive, steam pipes are not going to last long, if S02 contamination exists.

    • I can’t answer your question. I prefer that people have interest in a subject with little knowledge than if people have a lot of knowledge but no “hunger” for a subject. Therefore it’s always good to speculate on a layman basis if it’s driven by interest. The entertainment to talk passionate about volcanoes is more than cold knowledge.

    • Velvakandi
      I will take a quick shot at this, I am no expert. Geothermal plants deal with lots of suspended stuff in the water that they extract from the earth. Raw water from these wells would be unsuitable for use in a residential or commercial hot water heating solution. I would guess that the residual heat from the power generating process (also the electrical generating fluids, steam) is passed through a heat exchanger to “clean water” that is used to heat the towns and provide the electricity.

      I know that there is at least one person on this site that could add more information if I was incorrect.



      • Macusn, I believe your comment is correct, that the original geowater/steam has to be isolated from the distribution steam.

    • thank you to everyone who so kindly replied to this, much appreciated 🙂

      Of course I could have figured myself that they wouldn’t take the water straight down from the depths and into people’s homes. It probably contains all kinds of undesirable extras.

  32. The Iceland Meteorological Office (IMO) is VERY much aware of current discussions on the internet. In fact they had to post a response, see where they stated “It is hard to estimate the depth from which the SO2 is being released as the process is influenced by magma pressure. However, it is thought that the magma needs to be in the upper hundred meters of the crust in order for SO2 to be released. This is one of the reasons why the DOAS instruments have been sited close to Grindavík.”

    There are people posting on Facebook and other social media outlets that the evacuation of Grindavik due to the SO2 readings is due to the nearness of the magma to the surface and the corresponding fissure eruption. For one person who posted on FB, I had to actually countermand his post, because it was not entirely factual. (lots of people following this person)

    Again, I can see that the IMO is trying to be (super) responsible here, but some people unfortunately give into criticism, and want to dispute or disagree with what is being stated.

    • One more thing, if I might add, we need to let the IMO know that we appreciate their willingness to use the new DOAS instruments to get on top of the situation at Grindavik, instead of making false conclusions or assertions about what is happening.

    • I just read it as IMO were explaining the use of DOAS and its limitations. The SO2 may have come from Fagradalsfjall. I did not read it as being defensive.

      But SO2 was detected near Grindavik and there is a good chance that magma is close to there, the authorities cannot take unnecessary chances.

  33. About the eruption being slow, maybe we shouldnt be so hasty to expect a tiny lava spring. Holuhraun was intruding for weeks before erupting and took off hard. Laki was much the same, over a month of strong quakes and yet we all know how fast lava flowed out of that first vent, once a vent does open pressure is reduced to only what the magma itself weighs and that is negligible compared to needing to break the crust and shove it sideways.

    I dont think there is much else in common with Laki ir Holuhraun, its not about comparing the scale, those were massive rifts fed by central volcanoes, this is not exactly, an eruption will be volumetrically small by comparison. But the expected eruption now might start off with quite some force and die back quickly, the initial eruption rate could well be comparable to Holuhraun for a few hours and that is all that is needed to do the damage. Lowering flow rate into an intrusion can be a sign of there being inadequate magma from the source but it can also be a sign of high pressure, magma is an incompressible liquid basically so a full chamber at its limits will basically have 0 supply rate. In reality the surface will deform so it wont get to 0, but the principal is unchanged, a low apparent supply in a highly active system isnt a sign of decline it is a sign things are reaching the limit…

    Really it makes sense, if magma is flowing in then eventually it will erupt. It took only 3 years to reach this point, and possibly much less even. There is still anywhere from 30 to 300 years left of this cycle… If I had any say about it, I would rather it actually does erupt at this point to make things obvious, if it doesnt then Grindavik will be left in an uneasy limbo where great expenses are required to fix the damage all while knowing the exact same thing can and probably will just happen again in a few months or years anyway. At least if an eruption does happen those resources can be spent on proper relocation of the residents.

    • This eruption (if / when it happens) is likely to be fed from the mantle. There may have been some accumulation under the lower crust for a period, allowing some mixing / evolution.

      • Given that 99.9% of all the lava erupted along the Reykjanes zone is primitive basalt, I think coniudering evolution in the magma composition is unnecessary. From a geochemical standpoint it is important but regarding its physical behavior at eruption it isnt.

        It also isnt quite so simple as in 2021, because the magma here does go into storage unlike early in the 2021 eruption where it just seemed to go straight up. Storage of magma in the crust removes the mantle generation rate as the limit for the intensity of an eruption. An eruption now is likely to be more powerful than the last 3. A future eruption fed by a similar dike as now going into the same rift would find most of the rift occupied, so the magma would erupt at enormous intensity. I probably sound like a broken record repeating myself about this but Svartsengi is a completely different sort of volcano to Fagradalsfjall, you saw the dike and how it began, nearly 20 km long in a few hours, it was basically moving at a light jog laterally underground. If it did so but upwards then we are looking at a swarm beginning and then a curtain of fire within an hour or two. The volume may not approach that of the giants if the central highlands, but the intensity does, 1000 m3/s is the same here as it is at Bardarbunga.

        Seriously this is not a tourist volcano.

        • Re: “Seriously this is not a tourist volcano.” That’s clear to all but the braindead. That includes both locals and ‘off-islanders.’ There are all ‘sorts’ getting bent out of shape when one suggests, in Facebook conversations, that travel plans be put on hold or cancelled. The cry is ”Iceland is open!”

        • Fully understand that this is not Fagaradalsfjall 1,2 and 3, and that this is in all likelihood a lot bigger.

          But what are the chances that the reactivated graben was formed by triggered earthquakes along an existing fault to accommodate magma rising nearby, e.g. Svartsengi?

    • Well said Chad!

      I feel so sorry for those residents who have been affected by this , especially for those for whom this is a second relocation. However, I believe it would be reckless of the authorities to allow then back into the town if this does all die down for the simple reason you stated.

  34. Have they started constructing the barrier wall around the geothermal station yet? I am thinking I am seeing lot of traffic in that direction …

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