The Grimsvötn eruption of 5 May 2021

Grimsvotn, with the ash layers of eruptions past

38 per cent of all eruptions in Iceland come from Grimsvötn. It is an amazing number: this hidden volcano, invisible and unreachable to all but the most hardy explorer, is among the most active volcanoes in the world. Not the most active: the volcano with the highest frequency of eruptions is Mayon, which has erupted 47 times (I think) in the last 500 years. Grimsvötn has ‘only’ had 64 known eruptions since 1200 AD, mainly identified through tephra layers around Vatnajokull. On average, it seems to erupt once every 13 years. But not all of its eruptions leave much tephra and more events may have been missed. The 2004 eruption left no tephra outside of the icecap and such an eruption would have been too small to have been counted in the 64! Even if only a third of its eruptions have been missed, it would erupt more often than Mayon. So perhaps Grimsvötn is the most frequently erupting volcano in the world? (Comments welcome!)

In fact this volcano is so dominant that the reported periodicity in Icelandic volcanoes (with a peak every 140 years or so) is almost entirely due to this one volcano.

So it is not a surprise that we are watching the Grimsvötn seismographs like a hawk chasing a mouse. (Or would that be the mouse watching the hawk?) And it is not only us. IMO has daily updates of number of earthquakes in the area. The total number during February was the highest since February 2011, and that was not long before its largest eruption in recent years. Could it be ..?

Monthly earthquake rate, for magnitude above 0.8. The dashed line shows 23 earthquakes per month; everything at or above this level is yellow. Source: IMO

Carl and I have had a friendly tussle about this for several years. We tried to predict when its next eruption would be. Carl felt that it would be last year. Courageously, I decided to wait until after that before making a new prediction. I don’t mind Carl being right, but I don’t like me being wrong. Delaying allowed me to hedge my bets. But now the race is run, Carl owes me a beer (not Carlsberg, please), and I can safely take the risk of being wrong.

My approach has been to forecast the future (a risky endeavour: it is better to wait until the future has become the past and go for hind-casting) by looking at the seismic moment plots. These are being carefully maintained by IMO, and the upward trajectory implies the future is nigh. Dinosaurs of the world, take heed! The asteroid comes! To quote L’Internationale:

La raison tonne en son cratère
C’est l’éruption de la fin

But it is not all plain sailing. Like a volcanic Dr Who, IMO has quietly been changing the past, and updated the plots, backdated. It is hard enough to predict the future without the past being changed. What is going on? Is this a momentous change? Or a micro tremor?

Changing the past

To see how the past has changed, let’s compare the old versus the new plots. Below they are shown together, one retrieved in September 2019 (top) and the other in January 2020 (bottom). The IMO-induced change happened at some date in between, and it caused the numbers to go up across the board, for all times. It is not just a scaling factor since the blue and green lines now cross over, which they did not uses to do. It is also not a complete overhaul since most features of the lines remain recognizable. So what happened? We could just ask them. But that is boring. Can we figure it out? (And while they are capable of changing the past, can we ask them to have a go at the UK Brexit referendum as well?)

It is easier to show the difference if we plot the old and the new together on the same plot. That is done below, for the post-2011 data. Black shows the old data, and red is the new. The left panel shows the raw numbers, obtained by digitizing the plot. In the plot, the numbers at the top axis indicate the day number, and the numbers at the bottom axis show the corresponding year.

The red (updated) line runs above the black (old) line at all dates. Did all the measured earthquakes become more powerful, back-dated? Perhaps. But let’s first see how the numbers changed, before asking the ‘why’ question. The right panel shows this: if we multiply the black (old) data by a factor larger than one, the two plots overlap very well. But the factor that we need to multiply it by changed with time. Before day 1800, the ratio is 1.5. Afterwards, it is 1.25. (These numbers are not very precise. I picked them because they seemed to work.) There are some small remaining differences but these may be related to how the plots were digitized, as that procedure is not perfect. And of course, my procedure of a simple scaling factor may not be fully accurate either.

But to come back to the question I did not want to ask: why? The easiest explanation would be that IMO is correcting for either incompleteness of the earthquake measurements, or for variable sensitivity of the seismograph network. The cumulative plot includes all earthquakes with a seismic moment magnitude larger than unity. (Note that the limit used in the daily earthquake count is different, and counts everything above 0.8.) This limit corresponds to a very weak earthquake, unnoticable by anyone without instruments. But (as an example), if the seismographs only detect earthquakes down to M=1.5, then some earthquakes will be missing. We can guess how many would be missing since there are known relations for how many weak earthquakes there typically are for every stronger one, and so we can correct for that. Another reason why earthquakes may be missed is if it was not possible to measure a location for the event. Again that is more likely to happen for weak earthquakes.

A second reason for why the numbers may have changed is if a different conversion is used between the measured strength and the seismic moment. Several different equations exist for this and IMO could have changed the definition they use. But this would not explain why the factor changed midway through the sequence. The change in scaling factor occured around day 1800. This is approximately late May or early June 2016. It is not a very accurate date, but it is plausible that at this time (the end of winter on the glacier) maintenance was being done on the seismographs.

How about the pre-2011 data? The same procedure works for those data as well. For the the build-up to the 2004 eruption (the green line on the first plot), the new and old line overlap well if I assume a scaling factor of 1.1 before day 1750, and a factor of 1.3 for quakes afterwards. Day 1750 corresponds to October 2003. For the red line, going towards the 2011 eruption (the big one) the adjustment is more drastic: the scaling factor is now 2.2 until day 1400 (October 2008), after which it goes down to 1.4. It may be a coincidence that in both cases the change happened in October, but it may also just be a good time for maintenance, the last time the instruments are easily reachable before the winter storms come. (It may also be a coincidence that 2.2 is close to 1.52..)

Predicting the impossible

So now we know why the past is not what it used to be. How about the future? Has that changed too? And can we turn the improved (hopefully) past into an improved prediction? Before doing this, we first need to do a reality check. If you want to learn to predict the future, it is advisable to start with predicting the past.

I am using an equation that describes cumulative failure, such as metal fatigue. The idea is that the increasing pressure in the magma reservoir causes microfractures, which grow and make each next fracture easier to make. Obviously this may be a poor model for volcanoes that keep all pressure inside until they suddenly blow up, a bit like some people I know. (Those are often also the people with the most interesting thoughts and ideas: bottling things up can give highly developed ejecta.) As far as I know, a similar equation has been used to model volcanoes using number of earthquakes, but it has not been done with cumulative seismic moment. It seemed an obvious thing to try. I did this first in 2017 and at the time it seemed to work. Those fits suggested an eruption in 2020 or 2021. So far, that is not wrong.

However, this approach is certainly not infallible. It can be thrown off by many things, for instance a larger earthquake (a fault failure). Grimsvötn is located along the main Iceland rift, and a rifting event would also overrule any events inside Grimsvötn.

The equation I used is shown below. In the equation m stands for the cumulative moment, A0 is some constant (a scaling factor), t is the elapsed time, and t0 is the time when the seismic moment m goes off the scale. This is the last possible time for failure! In practice, you would expect failure to happen a bit earlier.

We first try out the equation on the developments leading up to the 2004 and 2011 eruptions. The data, m versus t, is read off from the plots above, and I have fitted it with the above equation. The fit predicts the appropriate values for A0 and t0. At early times it is hard to calculate these separately: you can get very similar results if you increase A0 and decrease t0. (Mathematically, you measure the ratio between A0 and t0.) As the line curves upward, the values become better determined. But you don’t get fully accurate values until it is too late.

And here are the results for the Grimsvötn history. The equation can fit the overall shape of the curves very well. But there are deviations. Between 2002 and mid-2003, there were fewer quakes than would have been expected. The curve rapidly recovered the missing seismic moment in the second half of 2003, building towards the eruption in 2004. The left fit has constants of A0=1.45 and t0=2200 days. The run-up to the 2011 eruption can also be fitted well, but now there was an apparent excess of earthquakes during 2009, followed by a less active period before it rejoined the model curve mid-2010. Here the constants are A0=2.0 and t0=2600 days. Note that the build-up was slower than in 2004.

So predicting the past seems to be possible. At the very least, the model curve more or less worked, and Grimsvötn followed a similar curve and erupted at a similar point on the curve (corresponding to 4.8 on the axis) on both occasions. Using the new past, can we now predict the future?

The post-2011 curve shows a slow increase, becoming faster from 2015 onwards. The main problem with fitting this curve is the largish earthquake that happened during 2016, which increased the cumulative moment in one step from 1.7 to over 2. There is some doubt whether this single event should count towards Grimsvötn. Thomas has pointed out that it happened on a different fault system which happens to be just inside the box that IMO uses to identify Grimsvötn quakes. So perhaps we should take a cue from IMO, change the past, and delete this earthquake.

I tried two fits, one with this earthquake removed from consideration (shown on the left), and one with it included (shown on the right). With it included, I cannot get a decent fit. The curve is distinctly different in shape for what the model produces. So I am happy for it to be left out as a distraction. If the model doesn’t fit the data, the data must be wrong!

My best attempt is therefore the plot on the left. It has constants of A0=1.8 and t0=3900 days. If I assume that an eruption will happen when the seismic moment reaches the level ‘4.8’, as it did before, Grimsvötn will blow around day 3630, or 5 May 2021. The faster fit on the right, which includes the deleted quake, gives an eruption at day 3455, or 12 Dec 2020.

These precise dates dramatically overstate the accuracy of the fits. More reasonable is to take a three month uncertainty either way. Based on both models, I predict that the eruption will happen sometime in the period from September 2020 to August 2021. Within that period, Spring 2021 is the most likely.

There are quite a lot of assumptions here. It assumes that Grimsvötn will continue to behave as it has done before. It assumes that there won’t be a sudden event which breaks the fault, opens the floodgate and gives Carl ammunition to withhold my beer. It assumes that IMO will not change the past again. And it assumes that Grimsvötn doesn’t just change its mind – volcanoes don’t like being predictable!

Most importantly, it is still a bit too early for a unique fit. By giving less weight to the earlier parts of the curve, I can also make a slower fit, as shown below. This one pulls the trigger on day 3772, which is 24 September 2021. So we could even move the eruption to the autumn of 2021. Time will tell.

A slow fit

Grimsvötn interruptions

One question is left unanswered. There have been several periods where the cumulative seismic plot stopped increasing as fast as it should, after which it quickly recovered the lost amount. Why is this? Was Grimsvötn hibernating for a few years? It turns out that the cause is simple and interesting, but also hard to explain.

There have been two significant seismic episodes around Vatnajokull since 2011. At VC we know these well! And they correlate nicely with the Grimsvötn seismic interruptions.

The first of these was (of course) the Holuhraun eruption. Grimsvötn became very quiet from 2012 to mid 2014, corresponding to the run-up to Holuhraun. And ss soon as the eruption started, Grimsvötn began to recover from its seismic holiday. Apparently, the increasing pressure in Bardarbunga had calmed down Grimsvötn, and as soon as the break-out began, Grimsvötn recovered its stress.

The second recent event was the seismic crisis in Öræfajökul. While Öræfajökul was building up in 2018, Grimsvötn entered a quiet period. Grimsvötn recovered at the time that this crisis peaked; afterwards, while Grimsvötn’s actvity accelerated, Öræfajökul calmed down again. You win some, you lose some.

But how did these other volcanoes affect Grimsvötn? The first point to notice is that in both cases, Grimsvötn fully recovered the lost earthquake moment. This means that no magma was lost to these other volcanoes: the interaction was one of pressure or stress, not a direct connection causing magma leakage. When Bardarbunga was preparing to erupt, it reduced the pressure in Grimsvötn. The rising magma in Bardarbunga acted as a safety valve. But as soon as the eruption started, that safety valve shut close again. Now Bardarbunga is not very far from Grimsvötn, and a deep underground connection is not implausible. But Öræfajökull is a completely different system, and very likely completely unconnected. So how could Öræfajökull possibly affect Grimsvötn?

The most plausible suggestion seems to be that there is indeed no direct link. Instead the volcanoes interact through their effect on the spreading rift that runs through Vatnajokull. As magma accumulates in any volcano under Vatnajokull, it changes the stress on the rift. The rift relaxes, and this reduces the squeeze on the Grimsvötn magma reservoir. As the volcanoes settle down, the rift becomes stressed again and the squeeze on Grimsvötn’s inflating magma reservoir is re-instated.

This model explains why there is long-distance interaction between non-communicating volcanoes, and it explains why Grimsvötn fully recovers from its holidays. The precise mechanism remains a bit vague. And the dip around 2003 does not an easy cause: Bardarbunga was becoming active in this period, but so was Katla. Neither was as dominant as the ones last decade. However, Katla is really too far way, and Bardarbunga may be the only plausible cause.

Going up

The fit shown above predicts that the eruption is still a year away. This seems surprising given that the monthly number of earthquakes is already so high. Perhaps Grimsvötn will change its mind and go faster. But for now my prediction is 5 May 2021.

Although I predict it, I don’t believe this date myself! The uncertainties are still much too large. We really can’t say much more than ‘probably sometime in the next 18 months’. But to nail my colours to the mast, and to give Carl a target to shoot at (he is very good at shooting, apparently), I have put the date here anyway. It is even in the title of the post. If it is a fail and I need to deny the existence of this date, the only way for me to ever get around it will be to do an IMO and change the past. If the future does not perform to expectations, the answer always lies in the errors of the past.

Albert, March 2020

C’est la lutte finale
Groupons-nous, et demain
Le cratère de Grimvötn
Sera la fin du genre humain.

(A little over the top, I know, but the 19th century was like that.)

The future? Iceland, 6 May 2021

108 thoughts on “The Grimsvötn eruption of 5 May 2021

  1. The volcanoes with highest eruption frequency are probaly Etna, Stromboli and Pacaya.
    But these volcanoes mostly do small eruptions and small lava flows.
    They are not very productive in short timespans.

    Grimsvötn is a giant behemoth that may have the largest magma resovairs of any basaltic volcanoes.
    There maybe 600 to 800 km3 of basaltic magma in the very deep depths of Grimsvötn system.
    Of course most of that is passive and cannot erupt.

    Question: whats the km3 volume of magma in Grimsvötns upper magma chamber?
    thats inflating towards eruption.

    Very fun times in Grimsvötn now

    • Semeru in East Java produces a minor eruption every 20-40 minutes, with explosive eruptions including pyroclasic flows and significant loss of life every few years. It may not make the list because the activity since 1967 is classified as one eruption. Merapi (central Java) issanother frequent explosive erupter which closed down Jogjakarta airport aw days ago.

      • Yes thats true… but its not very productive in materials as most very frequently with small eruptions that some subduction zone volcanoes are. ( but it also depends on the volcanos oldest age, how fast the edifice formed to estimate productivity )

        Grimsvötn tops Semeru in long term productivity
        But these volcanoes are so diffrent in geology setting
        Its like comparing Planet Jupiter to an Apple

        • I think that the most frequently erupting volcano is Piton de la Fournaise, the most often quoted number in papers is 1 eruption every 9 months on average. I don’t think there is any volcano that can top that, the second place migth go to Etna.

          However which volcano is the most active would be a something very relative and depending upon which criteria you use, like for example: number of eruptions, number of paroxysms, supply, productivity, time spent erupting… The longest known erupting volcano is Yasur, 246 years according to historical evidence or 800 years according to geologic evidence, but Erta Ale and Erebus have been erupting for an unknown amount of time, unlikely to be longer but who knows?

          The most productive volcano I think is Kilauea but I am not sure what would the exact rate be, Nyamuragira and Bardarbunga are also very productive from what I know, Grimsvotn would score high if you pick a recent period that includes the Skaftar Fires in but is probably below the previously mentioned in the longer term.

          • Grimsvötn maybe the basaltic volcano ( in holocene ) with the largest eruptive absolute capablity for large basaltic events
            Sakursunarvatn thoeltic basalt eruptions where insane

            But Grimsvötn is not a good contester in long lived productive activity
            There Kilauea and Mauna Loa winns.

            But Grimsvötn is a true beast in eruptive power of todays basalt volcanoes

          • Question: whats the km3 volume of magma in Grimsvötns upper magma chamber?
            thats inflating towards eruption.

            The papers says 30 to 40 km3 of Grimsvötns upper magma chamber
            Is this really true? thats pretty impressive
            ” a sill boulge a few kilometers deep with an upper 2 to 3 km thick pure melt lens, feed by an open conduit at depth”

            I wonder if this is true nature of Grimsvötn

          • Sounds reasonable. But the volume of the magma chamber is not necessarily the same as the volume of the magma.. A magma chamber will have compartment or sills, and some fraction of the volume is filled with solid rock which separates those magma pockets. And not all magma is eruptible. But it takes a big reservoir to feed Laki.

          • Albert But what about lava lake volcanoes? They are signs they are very molten and liquid in their magma systems

            Very few volcanoes are like that

  2. Yeah lets talk Iceland, volcanoes!
    Splendid article Albert, thanks a lot.

    Maybe one should keep in mind that a change in magma volume causes earthquakes, not persé increase of pressure… In my opnion part of the cumulative seismic moment building up can be taken out of the diagram, because part of it is caused by B (2014/15) and the expansion of Grims volcanic system to the north (“tip boathull” Greip!).
    Second is very speculative, I know. My guess(taken out that part mentioned) we’re not far over 2 nm csm now, and that matches with the diagrams 2004 and 2011 quite well. With the curve the two past build up’s have made taken in account, about (at least) 400 days are ahead till Grims nears 5 nm.
    So, I am with your prediction… 😊

    And may I recommend a Duboisson beer to cheer… Cuvee des Trolls!


  3. Thanks Albert. With all the other excitement going around, it’s easy to forget Grimsvotn is bubbling away quietly (or not) to another eruption. Perhaps a Volcano Cafe moneyless bet on the eruption date might be on the cards?

    • The end?? LOL!!! The EU is already collapsing. We have our sovereignty back. For once, it is Britain First. Project Fear is dead. Special thanks to Nigel Farage- a true patriot

      edited to remove the name calling. discussion is fine, insults are not. admin

      • I kind of like the term “great snowflake meltdown” to describe a conservative victory in the face of an overwhelming, nigh-hysterical barrage of political BS from well-funded leftists who claim to be exclusive champions of the “people.” Things are collapsing in any case but we need a good solid VEI7 to push us over the edge.

        edited to remove a potential insult. admin

          • Hey there is no reason to say it can’t be both! Then again I don’t have a political group but I don’t hearing people rag on the Orange Haze or Pocahontas.

          • To all in this thread – Please keep it nice and on topic. If you want to discuss politics head to the bar and get yourself a drink.

  4. Albert, couldn’t you move your prediction back one day? It would be a magnificent way to celebrate 2021’s Star Wars Day!

  5. Excellent article as per Albert, thank you!

    A question though; given the evidence pointing to an expansion of Grimsvotn’s magma chamber (I believe an article mentioned it in here a while back), would it not be reasonable to expect a greater threshold CSM will need to be reached for the next eruption to occur, and therefore an even lengthier inter-eruptive period than you have suggested here?

    • That is possible. The last eruptions happened at similar CSM. But that may not repeat. But if a larger value is needed, it might not postpone the eruptions by that much because it increases quite rapidly around that time. For instance, to go from 4.8 to 5 would take less than a month, on the projected track. Carl has pointed out that the eruption could also happen earlier, if a particular weak spot develops. The next eruption will add valuable data, no matter what happens. The forecast for the eruption after that may become more accurate.

    • Grimsvötn probaly haves the most molten and liquid magma system of all volcanoes in Iceland.
      Very few deep earthquakes suggest that, and its high productivity.
      its materials are also suggestive of that.

  6. About the ongoing Covid-19 eruption which is wreaking havoc on the financial markets, economy and society. Which VEI-scale could the Covid-19 have potentially have?

    • Covid19 is a huge problem. I suspect this is going to be the biggest problem the world has ever seen since WWII, and whilst not as bad as that event, its going to be damaging enough.

      Look at the economic impact it might have? To mention a few: many airlines collapsing, trading businesses having disruptions because of the supply chains and going bankrupt, a crisis potentially bigger than 2008, whilst at the same time, the health systems will on the edge and perhaps 0.5-1% of world population will die (which is a number of deaths similar to WWII!). And although it kills mainly older people, it also kill young and fit people too.

      Anyways, this sort of disasters happened frequently during the past centuries, so there is no reason to not expect them to repeat again. Its nature mechanism to keep our population reduced.

      To answer your question, a large VEI7 would do the same effect. The unknown eruption of 536 might have killed a third of Europe back then. It was a huge event. I dont think covid is going to be in the scale either.

      Usually volcanoes dont kill a lot. Other disasters (wars, pandemics, tsunamis) kill far more.
      Last century, the world wars cause the greatest destruction in society.
      The Chinese famine in the sixties too.

      A small VEI7 like Tambora, caused a year without summer, it might have killed 100.000.
      Laki, which was only VEI6, might have killed more, due to SO2 poisoning and famine.
      A similar disaster, the 2004 tsunami, killed 230.000.
      But these disasters killed around 1% of what world wars killed or some of the worst pandemics in history (like the Spanish Flu or the plagues of 536 and 1347).

      • Volcanoes might not kill many people by an eruption, but with the after effects of it another kettle of fish

      • Quite. Also there seems to be widespread ignorance on the fact that for viruses once caught and recovered you are immune for a period, usually at least a year, and longer if you are continually challenged by the virus. Basically because its infectious pre-symptoms its going to spread quite readily and this is made worse by reports that some carriers did not even feel ill whilst shedding the virus so the number infected may be very many times the number with symptoms severe enough to be tested let alone died. It seems to be reported that all those dying have pre-existing rather severe medical problems too so I’m hoping that 1-3% mortality is about right and this is concentrated on old and susceptible (like me) rather than most of the population. Since everyone looks like getting it the number dying is rather independent of how much you slow the disease but on cost deaths due to infrastructure failing may be quite significant. For example if you close schools, parents must stay at home, pharmacists cannot make up drugs and people die as a result.

    • I was checking which coronavirus clusters are appearing around Europe and the US, so we could expect where will the next quarantines appear (after north Italy):

      In Germany there are two focus around Dusseldorf (Aachen and Essen)
      In France the region of Oise, north of Paris
      In Spain, Torrejon de Ardoz (city east of Madrid) and Basque country (Vitoria-Gasteiz)
      In Austria, in Vienna.
      In the UK, near Brighton in Sussex and maybe Manchester region.
      In Switzerland, near the Italian border.
      In the States, in California (near the bay area) and Seatle.

      Some of these cannot be quarantined as they are large cities, but some smaller regions might be the next unlucky ones
      Here in Scotland I seem to be located in the region where most cases are appearing, and they are all just 15km away, so I am naturally concerned with this.

      • I’m with you on the Bay Area partially shutting down. Just this week many of the tech companies have told their employees to work from home. My school (Sacramento City College) will eventually have a student or staff show up infected,I’m just hoping it’s after the midterm which is this week.

        Waiting to show signs of illness myself as I’m near 100% I’ve been exposed in some way. Will be thrilled to come out of this unscathed.

      • New wrinkle. Sac City College emailed all of us today to say “we’re still holding in-person classes, but having our staff prepare to convert all in-person classes to online.”. Sierra College, another CC in Rocklin (a Sac suburb) has had 3 students test positive over the weekend and is shuttering campus through the end of March. I’m going to assume SCC and then other campuses of Los Rios aren’t far behind. Meh.

  7. Sometimes volcanoes can be predicted scientifically with an astonishing accuracy.

    Hoiluhraun was forecasted (in Sept 2014) to terminate its eruption around the first week of March 2015, based in the curve of decrease of earthquakes and caldera collapse. It was amazing to see it happening exactly like predicted with an accuracy of a few days.

    Before that, Carl predicted the eruption.

    Grimsvotn can be predicted based in what this post writes about.
    It was expected to erupt in 2020-2021 several years ago, and it seems its going to fit that prediction and erupt sometime in the first months of 2021.

    The hotspot / plume increase in activity in Iceland and predicted by me and also by the Icelandic scientists, to happen between 2010 and 2030, based in a historical cycle of 130-ish years. Its developing right on schedule and as expected, and more big eruptions are expected this decade.

    And some weeks ago, we predicted that Reykjanes will start a cycle of eruptions this century, that will continue for 200 years. We remain to see it happening.

    Hekla seems to be a black sheep and it erratically shifts between different temporal patterns of eruption, but I noticed its tendency to disproportionally erupt in late winter and spring months.

    I keep saying that some volcanoes are more likely to erupt than others. My candidates are Askja (small eruption), Kverfjoll, Oraehajokull, Reykjanes, Hekla, Hamarinn, and Grimsvotn and southwest neighbours.

  8. Albert, if you manage to hit the luck jackpot of nailing a prediction like this, and a Grimsvotn eruption happens within two weeks of 5th May 2021, then I would challenge you to book a flight to Iceland and have a dip in the cold Icelandic ocean waters and post a picture of that in here 😀

      • Its not that hard. You can run towards the ocean, dip for 20 seconds in the 4C water, and then quickly leave and dress warmly afterwards. Its a form of severe self-inflicted suffering but quite exhilarating afterwards. Going under half a minute is very important to prevent risk of hypothermia. I did it twice, the first time was the fishermen festival in Iceland (people have fun games to see who ends up falling into the freezing waters, and then at the end some people go dipping nevertheless) and we were all surrounded by medical staff and a rescue helicopter, to prevent any mishap.

        • Medical staff and Helicopters?!
          In Finland the municipalities keep wakes open in the lakes so that people can take their daily Ice baths.

          Then again; Sauna & Sisu…

  9. That was brave but will it wait that long? Interesting development, was it listening?!

    06.03.2020 23:55:38 64.424 -17.244 1.6 km 3.2 99.0 2.6 km NNE of Grímsfjall

    Pretty shallow for a 3.2… top of magma chamber?

    • Who would have thought, ol’ grimsy is following volcano cafe…?
      Or maybe it’s just albert’s sense for a good topic.

      • I blame Carl. He had a word with IMO to push for a faster eruption. Similar events happened in the two previous run-ups. In those case, the area grew quieter for a short while afterwards, so we need to wait a few weeks before we know how this changes the projections. It does make the slowest model (eruption second half of 2021) less likely. But not impossible.

  10. Back to the peninsula swarm for a moment. The early EQ’s formed a nice vertical graph showing rising magma. Now that the focus has shifted, is another vertical stack forming, or is magma doing some kind of lateral shift? (or is it shifting stress on the faults from the uplift?) A previous article mentioned that eruptions along the parallel eruptions zones tended to happen at around the same time. Are multiple magma bodies rising?

    • That shifting activity to Reykjanes could be a response to the uplift of Þorbjörn, or not. It is an active seismic area after all. But something more is going on right now. The nearby, normally very consistent GPS station Nylenda did get a little push to the north during past weeks activity.

    • I think this whole area is a series of faults I’ve seen described as bookshelf faults. To me the initial intrusion started east of Þorbjörn ran towards it and the response we are observing is the books all shifting around.

  11. Having Icelands highest magma influx
    Whats the temperature of the magma in Grimsvötn ?
    Is it around 1180 C ?

    • Do you mean in the magma chambers, 2-15km below ground? Or the eruption temperature? If you extrapolate the crystalization temperatures (which give temperature at a particular pressure) to zero pressure, you get an eruption temperature of around 1080C. The mean magma chamber temperature 2 km below ground was 1118C for the 2011 eruption.

      • Thats really cool … pretty cold for souch a volcano
        I belived it woud be like Holuhraun 1180 C

        Whats the temperature in Grimsvötns deep magma resovair?
        Kistufell was 1270 C in its magma chambers

      • I doubt these numbers
        Kistufell over at Bardarbunga had 1240 C Early holocene magmas erupted
        The hottest magmas ever found in Iceland

        Grimsvötn should hover at around 1200 C in its magma chambers: This is the hottest part of Iceland

        • Slight digression, but… hypothetically, if it were to happen, in what kind of geological setting, I wonder, could komatiites be erupted today?

          The youngest known komatiites are ‘only’ 89 million years old (which surprised the heck out me when I learned it, you tend to think of them as pretty much exclusively archean!). If it could happen as recently as 89ma ago, it’s just barely possible it could still happen today, in exactly the right conditions.

        • Does Grimsvötn have the highest influx or does Bardarbunga?

          At least to me it seems that Bardarbunga has a more impressive history with frequent large eruptions from the Veidivötn, Dyngjuháls and Holuhraun fissure swarms (like Thjorsa 20-30 km³, or Trolladyngia 15 km³…). Compared to Grimsvotn which has only done 2 eruptions its fissure swarm during the Holocene: the Skaftar Fires and Núpahraun/Rauðabergshraun, Bardarbunga feels more impressive to me. but idk.

          • In 1910, there might have been 3 Vatnajokull volcanoes erupting at the same time: Hamarinn, Grimsvotn and Thordarhyrna. Hamarinn seems that it erupted from 1909 to Oct 1910, and either or both Grimsvotn and Thordarhyrna erupted sometime in the year with ash fall reported but no details about the timing.

            In 1902 and 1903, there were also two simultaneous eruptions: somewhere near Bardarbunga, possibly Dyngjuháls near Herdubreid; and at the same time, somewhere near Thordarhyrna.

            This happened just 25 years after the Askja big eruption, and it marks the end of the last plume maximum in Iceland, some 120 years ago.

            By the way, in 1725 there were also 3 eruptions in Iceland, but not sure about their timing.

        • Thanks to Carl for finding this kistufell link!

          Iceland plume is probaly just as hot as Hawaii
          Around 1500 C deep down in the upper astenosphere
          Vatnajökull arera is toasty as heck

          Kistufell lavas erupted at 1240 C and was stoored
          in a 1270 C crustal magma chamber.
          Deeper down in the astenosphere its much hotter.
          1240 C eruption temperature is really really hot

          ” Kistufell (64°48′N, 17°13′W), a monogenetic table mountain situated directly above the inferred locus of the
          Iceland mantle plume. Kistufell is composed of the most primitive olivine tholeiitic glasses found in central Iceland (MgO 10·56 wt %, olivine Fo89·7). The glasses are interpreted as near-primary, high-degree plume melts derived from a heterogeneous mantle source. Mineral, glass and bulk-rock (glass + minerals) chemistry indicates a low average melting pressure (15 kbar), high initial crystallization pressures and temperatures (10–15 kbar and 1270°C), and eruption temperatures (1240°C) that are among the highest observed in Iceland. ”


          • That is mainly a matter of depth. The Grimsvotn magma crystallizes at a pressure of 2-6 kPa. Things cool when the pressure goes down. Extrapolate Grimsvotn to a pressure of 15kPa and you get a temperature of close to 1250C. But that is not where its magma is stored. Note that the text you quote distinguishes melt temperature from crystallization temperature. What it talks about is in effect the depth from which the magma ascends to the surface.

          • Thanks Albert What depth is? 15kPa?

            My math dyslexia is so bad that I still cannot read a clock despite Im 24 ( Im a classical looser zero intelligence ) Im a Sauropod

            So a little help here:
            15kPa: But what depth is that in kilometers?
            And how many bars is that in Atmospheric pressure?

          • My mistake: it is not kPa but kbar. They differ by a factor of 10^5.. 15 kbar is a depth of 40-50 km, so the bottom of the crust.

          • 1250 C is what I expects for deep magmas in Vatnajökull over the hotspot

            And in the astenosphere its close to over 1500 C in Vatnajökull

            What depth in kilometers is the 1250 C stuff?

          • The Iceland Plume is at 1490 C to 1510 C according to some papers

            Not far behind Hawaii thats
            ( 1530 C )

      • Kistufell erupted Thoelitic Basalt at 1240 C
        Above the full liquidus of a Thoelitic basalt mix

  12. Tonight there were a couple of quakes just south of Madeira:
    07/03/2020 20:58:05 21:58:05 32.5035N 16.7636W 20km 5.5 M(mb)
    07/03/2020 21:22:31 22:22:31 32.3292N 16.8562W 29km 4.3 M(mb)

  13. You can’t edit a post once it’s posted. Obviously the site administrators can since they’ve got access to the database back end, but we can’t.

    • Very small. That is a once-in-a-millennium event and it does not seem to me that the area is ready to feed another one of that size. A rift eruption in the dead zone is not impossible, but it would be expected to be smaller than Holuhraun. Grimsvotn tends to erupt in or close to the central crater. It does do rift eruptions, but infrequently.

      • If there is any part of volcanic eruptions that I have little confidence in my knowledge, it would be rifting eruptions. So I will take your word for it. Assuming that Iceland is going through a mantle pulse the chances might be higher then usual.

      • Interesting discussion here:

        Given the ‘once in a millennium’ criterion, perhaps Katla is the likeliest candidate for the next large rifting fissure event, since it hasn’t done one since Eldgjá ~1070 years BP.

        Also interesting to note that it states Katla has erupted a larger volume of magma than Grimsvötn in historical times; I didn’t know that. (Although that is largely because Eldgjá rather than Laki, so one eruption in historical times has skewed that stat, I suspect)

          • Yes, it is based on single eruptions but telling nonetheless. Grimsvotn is not a massive lava producer on normal eruptions. It is an interesting contrast to Bardarbunga with its quiet summit and tendency to do rift eruptions. In fact I would assume that Bardarbunga is the most likely candidate for a large rift eruption.

          • Eldgjá is Katla’s only postglacial Dead Zone eruption. Almost all large eruptions in this area have come from the Veidivötn swarm, so Torfajökull-Bardarbunga.

            This geologic map shows the age of lava flows and other units in Iceland:

  14. Greip active again this afternoon.

    First one is deep! 28.1 km. It is part of a series starting 14:42 and lasting 3 – 4 minutes. Just one of them in the list.
    The second series starting 15:42 lasting 3 – 4 minutes too, is less deep, 4 eq’s reported.

    The trolls down there are skimming stones on the magma…

    10.03.2020 15:45:04 64.598 -17.185 19.7 km 1.4 99.0 17.0 km ESE of Bárðarbunga
    10.03.2020 15:44:07 64.596 -17.186 16.5 km 1.1 99.0 17.0 km ESE of Bárðarbunga
    10.03.2020 15:43:17 64.611 -17.172 16.7 km 1.1 99.0 17.3 km E of Bárðarbunga
    10.03.2020 15:42:53 64.600 -17.158 12.8 km 1.0 99.0 18.1 km ESE of Bárðarbunga
    10.03.2020 14:42:03 64.626 -17.241 28.1 km 1.0 99.0 13.7 km E of Bárðarbunga

    Credits list and graph IMO

      • I love that tool. By moving the point of view and time slider you can really imagine the plumbing of these volcanoes. Regarding the Grimsvotn predictions, can you discount the effect of the recent nearby activity at Greip? Maybe Greip’s stealing some of the magma. Maybe some of the seismic moment comes from tectonic changes due to changes at Greip? Greip seems new to the party.

        • In theory neighbouring volcanoes can influence each other. Take a basket filled tight with pressured baloons. Let out some gas of one of that balloons (named Bardarbunga) and the other loose pressure too.
          After eruption of one of the volcanoes it takes time to load pressure and get one of the neighbours ready to erupt.

          When the deeper magma reservoir is expanding to the north a new volcano might be in the making mode. I took a graph from Beardy Gaz from the fabulous Greip expectations article .

          Figure 11. Cross-section of the Grímsvötn fissure swarm based on the boat hull magma reservoir theory championed by Carl. This differs from the gravity fed model championed by Albert. Graphic by Gaz, theory from Carl.

          An interesting part of the article is about the magma source of Bardarbunga and Grimsvötn. Are Greip Bardarbunga connected? Are Greip Grims connected? Remember Gjalp.

          Greip stands out by the deeper activity below 12 km; is it perhaps a dominating pathway from the plumehead to the volcanoes surrounding?
          It is interesting for sure to see what the interaction between the Vatnajökull volcano bunch is before/during/ after the next eruption.

          • This is an awsome cutaway of Vatnajökull magma region.
            But the dead zone wedge is shown in the wrong angle, in this cutaway.

            The MOHO here is close to 1500 C as its the Icelandic Hotspot.
            maybe as much as 1000 km3 of passive basaltic magma resides at the astenopshere under Vatnajökull.
            Mantle in Iceland is a few 100 s degrees hotter than mantle at a normal oceanic spreading ridge.

            Laki may have been feed from that deep resovair?
            but the a bit lower temperature of Laki suggest that its been stored for a short time before erupting.

  15. As expected, Grimsvotn has gone quiet after its big quake. But the number of earthquakes this month is already approaching the ‘yellow’ line. With more than half the month still to come.

  16. In order to assess the usefulness as a prediction, you could always fit the previous run-ups using incomplete data. Start with one year of data, fit the curve and take note of the predicted end date. Add one month of data and repeat, each time noting the predicted end date. Does the prediction stabilize and if so, how far ahead of the eruption does the method give a reliable prediction?

    I also noticed before, when I tried to recreate the curves using the listed records of quakes together with a simple conversion formula between magnitude and seismic moment, that I couldn’t get the curves to match. It never occurred to me that the scaling might have changed somewhere in the middle.

    • I think that is a technical term that requires set responses that may not be appropriate here. There was a new scientist article in recent months.

    • They didnt want to give the sense that the battle of containment was lost, so not to disencourage those containment measures.

      Now that containment is out of the question and the spread cannot be stopped by mild measures, they declared “pandemic”, so that government can go ahead and take dramatic measures, like whole country lockdowns, which is what will happen in soon all across Europe.

      I am not so sure that the lockdowns are a good measure. But who knows whats the best? No one.
      The economic consequences of this will be severe. I fear it might be worst than 2008.
      So 10 more years of recession ahead?

      Oh dear… I think all my adult life is going to be lived in recession mode….
      Those glorious 1990s, when I was a child and life was uncomplicated…

  17. New earthquake swarm at Reykjanes peninsula in the last few moments.
    Two stars – mag 4.3 & 3.0

  18. Renewed swarm at Reykjanes peninsula. Green stars this morning preceeded by something that looks like an intrusion event some hour before..

      • hmm, looks quiet before the 5.2 and aftershocks thereafter. big uplift short time Rocks don’t bend too well, they break.

        • At an earlieer time poit the red line above the “green big one” showed an around ten minutes long connected low amplitude sequence. Not visible now. Changed scale or maybe IMO removed noise?

  19. 10 green stars today so fare. I guess it might be a few more before midnight 🙂 That’s the only uplifting news on this black thursday for us in Norway. We are badly hit by the virus hysteria. I guess the next step will be: forbidden to leave home

      • As my daughter and partner have mild symptoms technically they cannot leave the house, as per new UK advice.

        I can still go out but I am avoiding exposing myself unnecessarily. There are people sneezing and coughing without having any respect or mindfulness for those around.

  20. from what I see Norway is hit pretty bad and ahead of curve (per pop). I hope the public health measures work and are followed. Good luck.

    • Was nearly emty everywhere yesterday after 5 pm in my city Bergen, and few people on buses ,trains and light rail. And nearly everything except from stores, cafes, some restaurants and pharmacy are closed down from yesterday afternoon ,and public transport still goes as normal but with limitations.

  21. For info a friend in E.Asia (age 71) sent me this, but I have removed homeopathic remedies used. Just some rather more graphic symptoms for the elderly.

    “Did I have coronavirus ???

    21st January– rough, sore throat – which always means a cold is coming on. I have not had a cold for a few years. sore throat better and no cold followed. Forgot all about it.

    5th March– very dry, burning cough in the night. Slight burning and dry cough in the morning felt OK in the daytime.

    Friday 6th March- no appetite, very thirsty, nose dripping like a tap, no sore throat, very conscious of heart beating regularly – so it was a cold ??? Felt rough. THEN . . .

    Rapid progression – cough became very painful, wanted to sleep and not be disturbed. Felt very sick. The usual cold and flu remedies did nothing. Burning in lungs.

    Recovery underway – voice deep and breaks when attempting high notes – eyesight blurry, eyes sore when moving them

    Saturday 7th March much better – went to work without problem.

    9th and 10th March continued improvement – still not much appetite.

    11th March 99.9% better – lungs clear – it was very, very nasty. To all those who say “It’s just a flu” and “Symptoms are very mild” – WTF is ‘mild’ ??? “

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