Signs and portents of Iceland – Revisited

Steam and gasses coming out of a vent on the summit of Hekla in 2005. Photograph by Borkur SIgurbjörnsson.

When I planned to write this article about the current states of Iceland I only wanted to write about Katla and Öraefajökull. But, as things turned out a third volcano got my attention.

In the end this article will be about how hard it can be for a layman to see what is important and not when overwhelmed with the plethora of information that is available for our beloved Icelandic volcanoes.


On the importance of importance

Crustal depth map of Iceland, Mohorovic discontuity. Image by Andrej Flis.

Not all volcanic signals are equal. And not all volcanoes are behaving the same prior to an eruption. Some volcanoes like Bárðarbunga are incredibly noisy between eruptions, prior to eruptions and during eruptions.

For Bárðarbunga it is a completely ordinary thing to throw a moment-magnitude earthquake of M5 with a follow up consisting of a heavy earthquake swarm, without it being a sign of an impending eruption. If the same thing happened at a more quiet volcano of the same size and capability, like for instance Grimsvötn, it would be time to run for the hills.

It’s the same with uplift and inflation, what would be big news for one volcano would just be a yawn for another volcano. If for instance Askja would be inflating at the rate and persistency of Iwo Jima it would also be time to run like a bat out of hell. At some volcanoes a few centimetres is a tell-tale sign, whereas at some volcanoes hundreds of meters are normal.

Some volcanoes are consistent stinky gas bags at all times, while others barely fart even during an eruption.

This is why it is so important to know your volcano well before trying to understand what it is doing. And, this is also why new data can be misleading as it comes to light.



Myrdalsjökull Glacier in 2005. Myrdalsjökull is the glacier covering Katla Volcano. Photograph by Chris 73.

Katla is quite likely the grand volcanic master of producing fake news, only rivalled by Yellowstone. Anything, including figures on ice cream consumption, will inevitably lead to war time headlines belting out that it is about to explode and destroy life as we know it.

Before we start with the latest news I would like to state the state of this volcano.

For as long as we have been able to instrumentally track and record this volcano it has suffered from intermittent intrusions visible on both seismometers and GPS-stations. Problem here is that it has not erupted for a long time, so we do not know that well how an upcoming eruption would look like, due to lack of anything to compare with.

All we know is that it is at times a rather noisy volcano, and that it can withstand a lot of big intrusions without erupting. A qualified guess, based on historic records from previous eruptions, seems to indicate that the last couple of days prior to an eruption would be quite memorable. So, expect to see something close to what you saw at Bárðarbunga prior to onset of eruption.

That means hundreds or thousands of earthquakes per hour with, some reaching up to M5 in strength.

Now let us turn to the latest news item. A group of scientists published a paper on measurements of free air CO2 released by Katla. The results are really intriguing since the values was quite literally sky high.

As far as we know Katla is ranking in at number 3 in the world in this regard. This is an anomaly in and of itself, since figures that high are normally associated with calcium-carbonatite volcanoes, or volcanoes that are erupting through heavy layers of carbonatite bedrock.

There is obviously no carbonatite lava in Katla, so we have to look for some other solution to explain where all that CO2 is coming from. My personal guess is that it is a function of fresh basalt percolating through a slab of oceanic crust partially consisting of calcite.

Calcite crystal on bedrock from Brazil. Photograph taken by Rob Lavinsky.

We all know that as you heat crushed calcite to produce cement you get an enormous release of CO2, cement production is the second largest source of manmade CO2 after consumption of fossil fuels. We also know that oceanic crust contains quite a bit of calcites.

What we know is that CO2 normally is an indicator gas pointing towards that magma has moved closer to the surface, so the world press jumped on the band wagon that his meant that Katla would explode hugely in the next couple of weeks. Problem is just that Katla has probably had a tremendous output of CO2 for millennia.

But here is the thing, we do know that the magma has risen closer to the surface lately, so a small part of that CO2 is probably related to an upcoming eruption. What the world press forgot is that even though that part is true, we are not actually seeing any signs that an eruption is close.

In Katla’s case we would see a tremendous amount of earthquakes for a few days coupled with rapid intra-caldera inflation. At least if it will erupt in the normal way through a caldera vent. If instead we get a rifting fissure eruption the noise level would reach unprecedented levels recorded in volcanology and there would be very funky GPS movements to the NNE of Katla proper.

But right now all we can say is that Katla will erupt one day. That is after all what volcanoes do. What we can’t do is accurately forecast when the volcano will erupt, since there are no current signs for an upcoming eruption. But, we will be able to forecast the eruption in time to give warnings to the local residents.



Havannadalshnúkur and Öraefajökull volcano. Photograph by Kristinsteff.

This easy to pronounce Icelandic volcano is currently my main cause for concern. In case anyone from the press is meandering about I should probably state that as far as we know today, the upcoming eruption is quite some ways away.

At the same time the current level of activity has never been seen at this volcano. We do though know from historic records that this volcano is quite noisy prior to an eruption, so what we are seeing is nothing at all compared to what will be visible on the seismometers when the volcano erupts.

After being dormant and almost entirely quiet since the last eruption in 1728 the volcano started to show signs of re-awakening in June 2017. To explain what we are seeing I need to fire off an analogy to put things into perspective.

What we are seeing is a heavy weight boxing champion waking up on a match day. The signals we have seen is the first initial fluttering of the eyelids. We have not yet even gotten to the first yawn prior to the morning cup of coffee.

In other words, do not expect The Rumble in the Jungle starting tomorrow.

Gravity anomaly map indicating where there may be magma reservoirs. All known Icelandic magma reservoirs show up as negative anomalies with the exception of Grimsvötn. To date there is no explanation why Grimsvötn is a positive anomaly. Image by Andrej Flis.

The reason for me being so interested in Öraefajökull is it’s eruptive history, as far as we know every single eruption after the last ice age glaciation has been a VEI-5 eruption. In 1362 it belted out a major VEI-5 eruption, and the one in 1728 was a minor VEI-5, and as far as we can see all other eruptions has been around the same power level.

During the two last eruptions the residents near the volcano was wiped out completely, making this particular volcano Iceland’s deadliest volcano after Grimsvötn. And today there are once again residents living near the volcano. This is why this is a volcano that science is not allowed to misjudge prior to an eruption.

That being said, I am confident that science will accurately forecast this volcano in time to perform a mass evacuation.

The thing that makes this volcano so dangerous is that it is old, and that it erupts far apart in time. This has led to the magma fractionalizing at a high degree leaving a large reservoir of rhyolite. And as fresh basaltic gas-rich magma intrudes into that reservoir it will in turn expand.

Gas rich rhyolite has a tendency to erupt violently at the best of times, but in this case there is a lot of glacial ice, and as that melt it means that there is ample amounts of water at hand to further increase the level of explosivity.

During an eruption air travel between Europe and the United States would become impossible, and the weather in the northern hemisphere would be affected.

Summary map of eartquakes at Öraefajökull showing how the amount earthquakes increases over time. Image by Icelandic Met Office.

What I find interesting is how relatively smooth and persistent the increase in seismic activity has been. In June 2017 we saw 13 earthquakes larger than M1.2, and last month we saw 25 earthquakes larger than M1.2. Compared to Bárðarbunga this is of course a pittance, but the trend is clear. Magma is at a steady rate entering the magma reservoir and it is showing quite nicely on the GPS-plots.

So far we have not seen any large earthquake swarms, and we know that prior to an eruption the swarms will be continuous and contain earthquakes large enough to topple houses. At least that is what we know from written historic records.

Without giving any firm timeframe I say that it is a safe bet that we will over time see earthquake swarms developing, that in turn will increase in size, duration and energy level. Between these we will see the background seismic level increase.

So far this is almost a picture perfect start for the ramp-up period prior to an eruption. And as time progress we will be able to produce better forecasts, because all we can say now is that this volcano will erupt again in a not too distant geological future. And with geological future I mean anything from a month to a century in this case, with a month being highly unlikely at the current state of affairs.

Now that we have discussed two volcanoes that we can forecast days, or even weeks in advance, it is time to go to another extreme. A volcano only possible to forecast an hour in advance, at best.



Tephra layers in southwest Iceland showing the various tephras of Hekla. Photograph by Dentren.

In some ways Hekla is the most boring volcano on the planet, since it is not giving away a lot of information before erupting. At the same time this just increases the mystique for the true volcanic connoisseur.

Between eruptions all we see is a slow and steady inflation without any spurts of activity, it is almost like watching paint dry on a wall. You know it will be finished sooner or later, and that the result will be pleasing, still it is quite boring to look at.

The same thing goes for seismic readings from the seismometers. Now and then you get a couple of earthquakes, but not more than 5 or so a month. None of them are big, none of them are really significant in any volcanic way.

And let’s not even get into measuring gases. Your Friday ale is more interesting than Hekla when it comes to producing gases between eruptions.

In regards of Hekla we can’t even complain about not having an instrumental record of how it behaves prior to an eruption, because we have two good ones. And those two are stunning examples of pretty much nothing.

Progress over time of Hekla earthquakes since the major upgrades of the Hekla seismic network started in 2011. Image by Icelandic Met Office.

The only thing we know from those two is that roughly 60 minutes prior to an eruption there will be a small spattering of minor earthquakes, and then the mountain pulls apart and the gates of hell opens up in vivid colours and fury.

In the end what makes Hekla such an enigma, and such an interesting volcano to watch, is that everything has significance. A small earthquake can at any time get a few friends and fire and fury unleashes a few minutes later. Any earthquake can truly be The One.

Today the monitoring network around Hekla is 10 000 times more sensitive than during the eruption in 2000. This means that we see quite a lot more earthquakes, both smaller and at greater depth and in far more detail.

This time around we should be able to pick up what the signs and portents prior to a Hekla eruption are. Hopefully and perhaps.

One of the guesstimates is that prior to onset of an eruption we should see a few deep earthquakes between 25-30 kilometres depth heralding influx of fresh magma at depth. According to the guesstimate these should be almost directly below Hekla proper. And from 2011 the network has been sufficiently sensitive to be able to pick up those deep earthquakes. And on Tuesday two of them appeared.

Hekla in 1893. Photograph from the British Library Archive released under public commons.

Let me be the first one to state that there is a bit of conjecture that an eruption at Hekla would be heralded by those deep earthquakes. But Eyjafjallajökull 2010, Grimsvötn 2011 and Bárðarbunga 2014 was indeed heralded by such earthquakes. At those volcanoes it took between a year to several weeks before the actual eruption occurred.

We do though know two things about Hekla, it is an open conduit system, and we also know that the fastest speed with which magma has ever risen in Iceland is 2 kilometres per 24 hours, so if we would accept those figures the fastest possible time to eruption counting from today would be in ten days.

I am obviously not stating that Hekla will erupt in ten days, it might be in ten minutes or in ten years. I was just guesstimating the fastest possible time that fresh magma at depth could cause an eruption.

Those two small deep ones has since been followed by another 3 minor earthquakes at depth between 1.5km and 10.7km. The most shallow earthquake was probably caused by the weight of the mountain causing downwards pressure, and the one 5km is probably near the magma reservoir. But the most recent one occurred at 10.7km and may in some respect be associated with an ongoing intrusion.

Hekla is absolutely infuriating. I suffer from an almost perverse pride in my ability to accurately forecast Icelandic volcanoes based on scientific theory and raw data. Bárðarbunga was easy, I had that lamped a year prior to the eruption, and accurately predicted when and how it would erupt days in advance. For Hekla I might as well don a robe and rub tea-leaves on my bald head and go about chanting. So, all I have written above about Hekla is conjecture at best, but still a scientific conjecture based on raw data and a tea-leaf toupee.



If we now look at Iceland as a whole and try to see which volcano will erupt next time we have two well known candidates, and only one of them is on the list above. Grimsvötn is the most likely, but currently it is a bit far off from erupting according to data, so Hekla would be the best candidate for the next eruption.

But after the likely culprits of Grimsvötn and Hekla the field is surprisingly open. Katla is not a bad bet for an eruption in the next decade, but it might hold out a bit longer.

Öraefajökull is the big unknown, currently it is ramping up nice and slowly and should at the current rate also erupt in the next decade. Problem is just that the current and ongoing intrusion of fresh magma might stall, and it could take a few decades more until it is ready.

The conclusion might be unsatisfying, but in the end all we can say is that deep into the future Grimsvötn will erupt a couple of times, and that a couple of other volcanoes will pop an eruption. Perhaps not so bad after all, there is fire and fury looming in the distance as volcanoes do what they do best, erupt.


168 thoughts on “Signs and portents of Iceland – Revisited

  1. That was informative, interesting and useful. Thanks Carl.
    Going back to another previously discussed Icelandic volcano, do you have a view on the state of play with Herdubreid since it was discussed here a year or two back?

    • It is interesting since it is teetering on the brink of becoming able to erupt. But, I do think it will need a second intrusion to go over the top.

      • I’ve noticed that over the last year it has seemingly had several small swarms of small quakes at similar depths. Never quite quiet, but not really kicking off either. A magma chamber forming at about 4-6 km depth perhaps?

        • It’s quite likely that there has been one all along since it is a central volcano that has erupted during holocene, but the new intrusion has increased the pressure in the old reservoir.

  2. Can we be so lucky to have more then one eruption at the same time. Like katla and ørea or all the monsters under the vatnafjøllglasier? You are the best carl!

    • It has happened a few times during the last century. On pure statistics about 1/8 eruptions should be a double eruption. So, it is far from impossible.

  3. Wow Icelands crust is 40 km thick!
    Thats oceanic crust as thick as some continetal crust. Normaly oceanic crust is some 10 km thick.
    Iceland haves No litosphere being spreading boundary combined with mantle plume

    • That astonishing thickness is why some of us think iceland is a stack of crustal slabs. Way back before iceland was here, there was a subduction zone in the area (Iapetus Ocean and the Caledonian orogeny), so mechanically, it is possible for the stacking to have occured. Next door is the Jan Mayen micro continent. It was sheared off and rotated into place from Greenland. The island of Jan Mayen is just a volcanic feature on its extreme north end.


    There are some new pictures of kilauea showing the recent lava flows compared to the same position from 2014. It is also interesting that you can actually see the outline of the 1790 and 1840 flows in the vegetation on the before image at the top.

    As far as the predictions in this post, I am most interested in hekla erupting. Deep quakes, rather inflation of the ground over a short time period, area where eruptions have occurred in similar locations within relatively recent time. All of these seem like sure signs of an eruption there one day and possibly in not too many days either. However considering this area isnt the hekla rift itself, it could be more prone to announcing itself with earthquakes before erupting.
    Would it be silly to assume that with about twice the repose time of the past 3 eruptions before it that an eruption now could be about twice as big? 1970 was after a similar length of time and it also involved a basaltic flank vent like this activity suggests is possible so this could be a similar scenario which would be interesting. hekla is also way more accessible and visible than holuhraun so an eruption there would be sure to draw a lot of attention, and a basaltic flank vent would be a lot more tourist friendly than a rifting fissure opening phase and plinian eruption.

  5. Nice overview! Öraefajökull is closest to an eruption, I think.

    Hekla’s deep earthquakes have two causes. One is tectonic, caused by the settlement of the deep crust underneath Hekla. The volcano is so young and growing so fast that the lithosphere hasn’t fully adjusted yet. This quakes will probably be a bit spread out rather than closely centred on Hekla. The second is magma changes. The eruption begin with a stack of quakes from 10 km upward. So yes, it is concerning to see both some deep quakes and shortly after a 10-km quake, but in this case it dd not lead to more.

    The silence in the run-up to an eruption is a recent phenomenon. Before the 20th century, Hekla did show strong quakes in the day leading up to an eruption. I think this is because at that time Hekla erupted infrequently. in teh 20th century it erupted much more often, and this has kept the conduit warm and open. Now there has been more time since the last eruption, and it is possible we will get a bit more warning. A bit.

  6. Why is why Grimsvötn is a positive anomaly??
    Its where ”all iceland hotspot magma comes up”
    Thats a mystery should be a strong negative signature there instead

    • It’s a whopper of a mystery that nobody has a good solution for.
      I think it would take something on the order of me and Albert and a full case of beer and bottle of whiskey in a warm pub to crack that one…

      (And no Albert, do not write a solution now until the beers have been drunk together 🙂 )

          • Could the plume be that huge negative anomaly slightly northeast of Grimsvotn?

            It’s also where the unknownabunga is located and also Gjalp.

  7. And since Albert pointed to it above.
    What I found so interesting is that Hekla was so much smaller in 1893, that image really shows how much mass that has accumulated in the following 125 years. What is almost perverse is that during the first half of Heklas illustrious lifespan she did not have an edifice at all due to everything coming up as tephra. It’s only during the latter half that there was lava flowing out, and that has increased over time.

      • Not that much: perhaps 10km3. That does not include distant flows or the part that has sunk below ground level.

    • was it really smaller or is it the angle of the camera?? Just asking… Best!motsfo

  8. If magma starts to rise more quickly/ be supplyed more quickiy to Hekla .. less diffrentiation will occur and lavas will be more mafic.
    Hekla may follow that route.
    Eruptions will be hotter and more basaltic
    Instead of the typical viscous basaltic-andesites that Hekla typicaly do. In 1948 late phase she was completely basaltic with etna viscosity
    The first phase was basaltic andesite suggesting old material on top and fresher magma came up later

  9. It has been a pretty quiet year for Iceland so far I would say. Looks like the wait for Grimsvotn could end up being longer than thought, I guess the 2011 eruption knocked the wind out of its sails a little. Bardarbunga seems to be quieting down somewhat, maybe it’s not going to return to regular eruptive activity just yet. Iceland remains fascinating and frustrating! On a different note, I don’t know why the media isn’t paying more attention to the situation in Indonesia, over 380 dead….. More interested in US soap opera BS!

    • I very much agree on that last point. Ryder cup was the top story on the BBC website, with Indonesia way down the list , well off the headlines. Sometimes I think our priorities are somewhat twisted.

      • BBC news 24 has been headlining with the Tsunami all day.

        • I generally look at the website rather than watching broadcasts.
          Yesterday I had to use their search engine to find it. Today is better, but still not great.

        • And scratching their heads over the size of the tsunami. Coastal topology ? Offshore land-slip ?? Complex faulting, perhaps…

          • Well in 2 dimensions at least, the bay looks much like a classic tidal bore estuary, so it could well be (depending on what is happening with the bathymetry re: depth) that the bay is indeed a natural amplifier.

            In 2 dimensional shape it looks much like the estuary of the Petitcodiac in Mew Brunswick. Until the building of the Moncton causeway in the 60s, that was the site of a tidal bore that reached 4-6 metres in height. The siltation caused by the causeway more or less killed it. Now that the causeway gates have been removed the tidal bore has returned, although it has not attained its former size.

            But if the shape of the bottom is such that the water level becomes very much shallower just after the sea enters the bay, it could easily amplify a modest surge into one which creates waves of 4-6 metres , as some of the witnesses are claiming .

          • That would be NEW Brunswick !
            I really should type with my glasses on.

          • There were a number of surprises. Reports stated that the tsunami came 30 minutes after the earthquake. That seems very late – the bay is only 20 km or so long. The tsunami warning was being lifted as it arrived. The video shows something that looks much more like a bore than a classical tsunami: a solitary wave. The two surprises were perhaps related. Was the tide going out?

          • Albert, I think we would also need to be clear about the location of the event that caused the surge. Given the time difference I don’t think any assumption can or should be made that it originated from the quake’s epicentre.
            If, as has been suggested, the quake or an aftershock caused some form of collapse below the water’s surface (or potentially this was rock falling INTO the bay?) that would also have a significant bearing.

            The wave looks to be travelling at a good pace over exposed sand flats in the video I’ve seen, which could be evidence of a tide… an enhanced tide… coming in, or it could be that the sands were exposed as a result of drawback. But in at least one video I’ve seen there appears to be a second wave that comes in as the water of the first is receding. No tidal bore does that. Tide comes in….and that’s it. One wave. So I take that as proof positive that it was not a tidal effect.

          • I have to retract my hydraulic jump idea from the back channel.

            The double wave works against the idea. Now I’m thinking a section of shelf calved off to initiate the tsunami, similar to what likely caused the 1929 Grand Banks tsunami.

            I still maintain that any tsunami warning system is going to be very ineffective if the causal mechanism is sitting right next to you, no matter how well maintained it is. This little issue is why the Cascadia tsunami is going to be a high casualty event when it happens. I think the only intelligent person there understood that threat and moved.

            As for warnings being lifted prior to arrival… in a way I can sort of understand how that happened. The focal mechanism (strike-slip) is not generally associated with tsunami events. In this case, the quake probably dislodged a section of shelf next to the island, and no one was looking for that.

            Standard Caveat applies → Not a geologist, and I did not stay at a Holiday Inn Express last night.

          • It was certainly a tsunami. But a tsunami acts as a tidal wave, and could also give rise to a bore in the right circumstances. That would make the initial wave much higher, and also change the speed at which it comes in. I hadn’t noticed the second wave. A secondary landslip near the mouth of the bay would have contributed.

          • Albert, if you’re suggesting that the tsunami tipped the balance such that a bay NEARLY the right shape or with NEARLY the right tidal range to have its own bore suddenly had one, I think that is eminently plausible.

            In the past I have spent a good deal of time talking online to people like Don Thiederman of the Tidal Bore Research Society, who seem to concern themselves chiefly with cataloging and describing the World’s bore phenomena . They made me aware of a large number of bays and estuaries which are very much on their radar because they may produce a tidal bore just very occasionally, at the very peak of the tidal range, or in extreme conditions such as storm surges and the like. The River Usk, Newport, South Wales is one example. It rarely happens, but it has been observed and recorded on a couple of occasions in the last decade.

            It is very easy to believe that this bay has that sort of characteristic.

            I also recall a conversation with Antony Colas, tidal bore surf explorer, just after his first trip to the “Bono”/ “Seven Ghosts” tidal bore in Sumatra. He recounted how they had lost a boat in the open sea between Riau and (I think ?) Singapore because they had underestimated the power of the tides. He said that there were several areas around Indonesia that were similar , with powerful tidal races and such, that warranted further exploration. I wonder if he was thinking of Sulawesi when he said that ? Perhaps I should ask him.

          • I DID ask Antony Colas, and he has come back to me with some very interesting information.

            Firstly, he told me that only last year he visited a previously undocumented tidal bore across the Makassar Strait from Palu, on the East coast of Kalimantan. He said that the tides are likely to be powerful in a bay of the shape of that around Palu, particularly in that part of the world.

            He also provided me with this link to a paper on the local tidal dynamics, which (to me at least ) makes interesting reading.

            Consequently, it seems all the more likely that an extreme tidal regime may well have played a hand in the generation of the tsunami.

          • The main earthquake hit at 6:02pm. High tide outside of the bay was at 6:41 pm. It was the highest tide of the day.

          • Now that makes things very interesting indeed. A smoking gun, perhaps. Time will tell.

  10. An interesting thing about the deep Hekla quakes is that they happened in exactly the same spot and depth as two even larger quakes, M2.5 and M2.2, that happened on Jan 28, 2017. This is certainly a spot to keep an eye on.

    Another thing about Hekla is the proximity to the SISZ. I’m wondering if stresses from the seismic zone can cause the mountain to suddenly be ripped open? The strainmeter at Burfell dropped like a stone when Hekla opened in 2000.

  11. I have to comment that Volcanos and industrial process equipment have some striking similarities. Especially some oil and gas processes. Both have a gas entrained fluid and a pressure vessel of some sort. Engineers can control their processes. Volcanologists can just look on with awe at mom’s nasty side.
    In both processes pressure is involved. Both fluids if brought to 15 psig quickly ( I use this pressure because in the end that is what the volcanic systems push against, atmospheric pressure. Oil and gas processes differ in that they are engineered with pressures included for a defined end result) will release most of their entrained gases explosively. Oops don’t want to lead you wrong here about the oil and gas part. Think no fire. No Hollywood. The gas molecules expand and are released and the fluid usually turns to a mist. Think coke bottle on steroids. Add heat and the system becomes more efficient. Hence words for equipment like heat treaters, separators, distillation towers. All this to take out the gas component and don’t blow up towns in Quebec. Volcanos do this by themselves and get you best the heck out of the way.
    Add in water and you have really volatile element in volcanoes. A (1) cubic foot of water will become 1528 cubic feet of steam at 15 psig. Restrict the ability of it to spread and you build pressure. Currently boilers are up to the 5000 psi level. Nothing compared to the pressures in a volcano. Water can continue to pick up heat as the pressure builds too. I worked with one that had 900 degree F superheated steam @ 1500psi. Believe me it will penetrate any weakness in the equipment. It can wash out steal if allowed to leak long enough. Raw static energy. Gas and steam are by far the most dangerous component in volcanos. Vapour basically, pressurized and heated. Once you have a pressure building up it will push in all directions equally.
    Bare in mind the term ‘line loss’. Basically it is friction and it applies to flowing fluids. Hence pumping stations or compressor stations. Necessary or Alberta oil wouldn’t make it to the border. ( I refuse to get drawn into any climate change/pipeline debate. I’ll leave that to the converted. We in little Siberia have seen a marked cooling in the last three years.) My point being that dyke systems will only carry fluid so far before the pressure from friction restricts it. Besides that the piping/ plumbing has to withstand tens of thousands of psi? Something will have to give. Static fluid though would act much like a Hydro test. As much as pressure as you can put on it till it breaks. Then it will flow till the pressure comes down to equalize
    Lastly Hydraulic pressure. I’m thinking of the Bardabunga article in Jan. Correct me if ‘m wrong but my impression was that it had a plug that acts in some ways like a syringe. As it re-inflates the plug rises.The lifting of the plug then converts to static energy. Add entrained gases and water to this equation too. My point being as the plug rises it gains energy in the form of gravity. It is released as it falls when a rift or an eruption occurs that is fed by Bardabunga system. I’m probably wrong on the article and I apologize if that is so. One should point out fluids tend to find there own level. I have no idea if magma is above the lasted rift eruption at Bardabunga or if it had a gravity factor, the plug may have been the agent. I remotely remember the figure of 5K being the depth of the plug. However other volcanos with shallow magma chambers will show this effect. I think Kilauea probably emptied this way, through gravity.
    PS I view Katla venting as a positive thing. Every molecule out is one you don’t have to worry about. It’s pressure released. Quite the opposite of the doom and gloomers. A venting volcano is like a well fed Pitbull. I’ll put up with a little gas if it doesn’t turn on me.
    Sorry for my Sat morning sermon
    Best to all Harley

    • Avoid feeding the dog pork trimmings and the gas issue is not as dire. A truly cruel “friend” will feel his buddies dog as much trimmings as the dog wants, and then giggle his arse off at the resultant odoriferous results as his “buddy” gags through out the evening.

      When growing up, my mom had a habit of whacking the doberman sleeping on the floor with a newspaper if it had gaseous emissions. Over time, the dog developed a Pavlovian response any time anyone passed gas. As soon as it happened, the dog would be out the door at a quick gait. This basically left us with a rather imposing guard dog… right up until someone farted.

    • Hydraulic pressure is a good way to view it. Atmospheric pressure is less relevant as the magma is typically a few km deep where the pressure is tens of MPa. At that depth there aren’t many weaknesses but any faults that there are will be taken advantage of. Otherwise, excess pressure will lift the rock and create space to flow that way. Viscosity is important in how well it moves. In the case of Bardarbunga, the exit point was a kilometer lower than the mountain above the magma reservoir. That is a lot of pressure differential.

      As to climate change, the minimum time period to define climate is normally taken as 10 years (and 30 years is better). Variation over three years is dominated by weather.

    • Neither…
      Grímsvötn is the lake system inside the caldera of Grímsfjöll. But… Nobody knows that so I use Grímsvötn to not confuse people overly. Not even the IMO calls it Grímsfjöll. 🙂

      • Hmm, you sure about that? According to futurevolc, Grímsfjall is the southern rim of the Grímsvötn caldera. Much like Hvannadalshnjúkur is a peak on the rim of the Öræfajökull volcano.

        • Grímsfjall is indeed the peak rim of the caldera wall encircling the largest of vötns in Grimsvötn, and it is all part of the fjöll.

          And now time to attain world domination via a secret language.
          Tänk såhär, Grimssjön ligger bredvid Grimsfjäll som är toppen av Grimsfjällen. Undrar vad Giggles Översättning blir av det här för alla andra. 🙂

          • Missade böjningsformen 🙂
            Men heter verkligen vulkanen som massivet? “Alla” källor jag hittar (förutom vissa artiklar på VC) använder vattnet som namn. Inte för att det spelar någon större roll 🙂

            Oh, maybe it’s time to switch back to the official language. Got a bit carried away there.

          • And that is pretty much why I also tend to stay watery when naming the volcano. 99.99 percent of humanity knows it as Grímsvötn after all. 🙂

      • “Nobody knows that”

        I do.

        And I still want to know why Grimur’s wife cursed his favorite fishing lake. If it’s due to him killing her father, why did he kill him?

        {And don’t tell me it was penis envy. The giantess married him so he at least had something going on}

        And is this the same guy as Grimur Geitskör?

        • How did people before modern time even know there was a lake there at all, I know Iceland was warmer and more habitable back then so was it possible that grimsvotn was actually not subglacial at that time?

        • I don’t think so. Human nature is to go look at stuff. Grimsvotn may have had an incident and someone went looking around to see where the steam was coming from.

  12. Stinkvötn since that Geothermaly heated caldera subglacial lake contains Icelands most powerful geothermal systems. The smell and taste of that water sourely is yucky
    Grimurs farty lakes

  13. Yes I had it happen to me. Darn dog would lay on your feet and welcome you to his house.

  14. Been a while since I posted here.

    Would it be possible that Hekla resembles what Tindfallajokul or Torfajokull were when they were young? IE, Hekla’s evolution will eventually resemble those two volcanoes? Seems like based on positioning, the tectonic strain could have simply shifted west, giving birth to the current location of Hekla.

  15. I wish I had put up a few tables on my dads farm. I could have Huckleberried all those darn rocks instead of doing it myself

    • To post an image, it needs to be on some other website first. Put the web address to the image in the post and it should show, either as image or as link (which one depends on WP). Note that the link should be to the image itself, not to a webpage that contains the image.

  16. Nope the mac doesn’t like that. JPG took over the chrome and refused to budge. I sometimes call the old girl, ‘Mule’. I’ve stopped whipping her, I found it only frustrates me more.

    • I’ve had occasional success using to host image plots. You just have to make sure that the link you grab is the actual image and not the host site. They tend to return garbage if it’s not the image itself. What you do is keep working with the site until you have just the image displayed, then copy the URL for it from your browsers address line and drop that in your comment.

  17. notice to the powers that be: daughter redoing computer tonight….. have no idea how it will impact here. Best!motsfo

  18. Something I have been trying to do recently is actually find out how fast lava in a lava fountain is going in order to reach 600 meters high (original discussion was from the kilauea iki lava fountain).
    This has got me wondering, for really huge fountains like this it is pretty clear the degassing is not a surface phenomenon, it occurs at depth in the conduit and is subject to the same ‘gun barrel’ analogy used to describe a plinian eruption. This has actually been confirmed for kilauea iki 1959 and so it is very reasonable to assume lava fountains of similar or larger dimensions are analogous. Now the main question I have been thinking about is how deep the conduit would have to be in order to have the lava accelerate to the (likely supersonic I haven’t done the maths yet) velocity it needs to get to that height. This is mostly to find out more about some of the ways these systems work. Most drawings from HVO show kilauea iki as a shallow side cent of halemaumau but I have a hard time believing it would have had such a powerful eruption if that was really the case. In my view there must be a deeper connection that is rarely used but can erupt independent of halemaumau.

    Same with the dead zone eruptions, I can’t see why some eruptions there are gigantic and very violent while others are fairly benign and I think the difference is the depth of the feeder. The skaftar fires could have even been fed from a dike moving along the Moho boundary,
    I don’t think the simple 300 meter difference in elevation between holuhraun and the dead zone is enough to explain why one was a voluminous but fairly standard hawaiian eruption but the other was a 20 km long fissure that erupted the entire spectrum of basaltic volcanism and involved more lava than every other eruption in Iceland within 500 years of it put together…

    • Luckily its easy to calculate the muzzle velocity for a vertical gun! It doesn’t even need to know the density of the material but this expression ignores air friction.

      velocity= square root (20h), where the 20 is 2g. All in m/sec.

      so 600m/sec has an exit velocity of about 110m/sec, about 36kph pr 22 mph.

      In passing thats why fairground rides actually don’t go that fast, it just seems like it.

      This one is fun, note you are suspended.

      • 110 m/s isnt 36 km/h, its about 400 km/h…

        Anyway I found a calculator and calculated that in order to have a height of 600 meters the lava fountain at kilauea iki in 1959 would have had to have had an eruption velocity of about 1100 km/hr, or mach 0.9. This is also factoring in that it took place at an elevation of about 1.1 km above sea level. The real value would have had to be a bit higher due to air resistance and also what appears to have been very high wind during the eruption when that fountain happened.

        (from HVO/USGS)

        For the 1600 meter tall lava fountains at the start of laki the fountains would have had to be going over the speed of sound to do that when you factor in air resistance, meaning this eruption would have created a sonic boom and probably not been effusive at all when it started.

        • The initial opening would have been faster still since we know that it injected ten cubic kilometers of material into the atmosphere as evidenced in drill core samples and other ash samples in the northern hemisphere. Lakí was truly the mother of all farts.

  19. I think this might be what you are looking for:

    I haven’t read it yet but does seem to go into the things you are asking about, it studies the relationship between the descompression rates that are related to magma ascent speed but shows for the case of Kilauea faster descompression rates from the shallower reservoir feeding the 1500 reticulite than for the deeper source of the 1959 Kilauea Iki fountain.

    They put the source of the 1959 eruption at a depth of 4 km, so clearly not coming from Halema’uma’u and it is also a little deeper than what usually considered for the south caldera rim magma reservoir. The 1877 eruption is also a good example of why Kilauea Iki is not just a product of Halema’uma’u magma intruding east, the 1877 eruption affected both Keanakakoi and Kilauea Iki craters, also there was a small vent in the caldera wall between the two so it fits with an intrusion happening along a ring fault of the caldera and since eruptions in the Keanakakoi area are related to the south caldera rim reservoir it probably was an intrusion feeded from this magma body at a depth of 3 km. Anyways Kilauea Iki is weird the mechanisms behind the three most recent eruption are probably different, 1868 was triggered by a magnitude 7.9 earthquake and happened at the same time as an small eruption in the volcanic SWRZ, I think this would better fit the scenario of the SWRZ-Halema’uma’u-Kilauea Iki line (which is the one HVO usually portrays) rupturing and the magma of Halema’uma’u intruding along it.

    • This is pretty much what I expected but it is interesting that the 1500 tephra is from a shallower source while probably having higher fountains, it must have been very gas rich magma.

      I guess gas content does matter because of that reason but it seems like the fountain height of primitive basalt magma is about 1/8 of the height of the degassing column of magma. That puts the degassing sources of 1959, 1969 and 1983 at about the same elevation within kilauea, about 4 km deep, with the relative heights of the tallest fountains of mauna ulu and kilauea iki being about the same due to similar elevation and pu’u o’o being slightly smaller being a bit further from the summit with slightly lower pre-eruption ground elevation. These vents could have all been fed from a common source as a horizontal conduit that initially formed in the 50s and grew rapidly after 1959. This conduit is deeper than the main magma chamber that deflated during the recent activity, about 1 km above the level sea floor around the islands, and about 7-8 km above the boundary between kilauea and the bedrock.

      1960 had similar fountain height to these other eruptions, 500 meters, but it was erupting from near sea level. Accordingly its conduit must have been a lot deeper, maybe 4 – 5 km below sea level. This could explain why some of its lava was picritic, as an alternative to it being kilauea iki magma that went all the way down the conduit. Like 1924 this event could have been relatively unexpected in the long term trend.

      1840 was definitely deeper than 1960, its lava was completely picritic, so its dike could have been possibly around 10 km. Accordingly it could have in theory had fountains 1000 meters tall, but it didnt so it must have been relatively gas poor, or that it was erupted so fast at the start that by the time a single vent had formed on the fissure it was already too wide to confine a high fountain, leading to passive high volume effusion like observed at pu’u 8.

      This years eruption in Leilani estates on this scale would have a degassing source of maybe only 1 km deep or less, this is indicative of a dike starting at pu’u o’o that went up at a slight angle to about 1 km deep under the Leilani area before finding an easier path straight up, if a lot of the pu’u o’o conduit is lower in elevation than this then that makes sense that the rift is not drained out yet. It probably requires a deeper intrusion like 1960 to fully drain, and this would probably create either a big cone or an extremely vigorous lava flow, although likely not a lot of new damage as most of this area is already buried. This also supports the rift reactivating, it isn’t dead yet. There will probably still be summit activity in the very near future, just enough to fill in some of the deep hole in halemaumau, and it could be pretty impressive but I think there will still be some more rift activity before things go full caldera filling/possible overflowing later this century. This rift period was much more voluminous than the 1700s one, or the 1500s one, so it might require a bit more than one terminator eruption to finish the job. The first sign of this could be lava erupting in pu’u o’o again, not like before with tube fed lava flows but just a lava lake, indication of magma at high elevation. The next would be earthquakes under the kapoho area and some deeper quakes under leilani as the dike extends and becomes deeper, then it would be wise to avoid the area…

      Extrapolating this to Iceland, skaftar fires probably had a degassing zone starting around 12-16 km deep, and possibly deeper because the lava was probably more fluid and hotter at eruption than the lava from kilauea and also erupted violently enough to fragment the magma into ash at the start. The underside of the crust of the dead zone probably contains long fissures and ruptures that are filled with magma or fertile mantle material, these roughly mirror the surface but much more dramatic angles, so the magma from this eruption probably seeped from the vatnajokull area along these boundaries within the gaps and eventually caused a rifting event where magma surged up this rupture and erupted violently at the surface. This also eroded the vents and lead to the pressure dropping enough to erupt as a lava flow.

      • This is what I mean. This is meant to be more to scale.

        1840 is the deep gray-blue activity at the bottom, moving at about 10 km deep.
        1955 is the blue area, it also includes the 1977 eruption because that is believed to be magma intruded in 1955 that got remobilised.
        From that dike stems the 1960 dike in purple, which probably went fairly deep. 1959 is also shown as a branch that went up through the summit to kilauea iki.
        The red is the active east rift system that started forming after 1960. Mauna ulu and pu’u o’o were both fed from this, and it is centered around 4-5 km deep. In orange are eruptible magma chambers, one under mauna ulu, makaopuhi, napau and pu’u o’o. The other orange is the 2018 dike, which was probably fairly shallow and above the deeper plumbing (but under the shallow halemaumau/SWRZ plumbing). The yellow is the fissure 17 andesite magma body which is of unknown origin but possibly from 1924.

        As it can be seen, despite the damage this years eruption caused, and how big it was, it hasn’t drained out the whole system, only the upper part, and the conduit is still intact. Reactivation of the east rift is likely. The area near heiheiahulu is showing deformation, and a dike did nearly erupt early in this years eruption not far from there, so a new slower/sustained eruption could happen from the highway area. if not, then activity will probably return to pu’u o’o. Either way this lava might rise up until the same thing as this year happens, a new deeper intrusion to the LERZ like 1960 and this is what actually takes out the rift conduit, forming pit craters and possibly leading to subsidence or collapse of the south caldera and koae faults too, and maybe also more of the pu’u o’o complex, basically anywhere that magma has been emplaced at high elevation in this eruptive episode.
        An intrusion of this scale would be on the order of between 0.3 and 1 km3, a big range but one that would definitely lead to another large eruption in any case, probably near the ocean at cape kumukahi.

        • The 1840 dike or dikes also reached the surface at the upper and middle ERZ, it was a huge intrusion along the totality of the rift zone that erupted at multiple spots along it, something that hasn’t hapened since then. To compare the dike of Leilani started from Pu’u’o’o, 1840 was almost twice as long. It was also a deeper intrusion than usual cause it has an unusually high olivine content, but I dont think it needs to go as much as 10 km deep to reach the olivine cumulates of the deep rift.

          I would see reasonable the 5 km depth for the east rift conduit, there was an article where from inflation following the 2011 Kamoamoa eruption inferred a magma reservoir 4-5 km underneath Napau crater. It maybe represents the aproximate depth of the upper ERZ reservoirs and shows a conduit that gets gradually deeper from the south caldera sources that are at 3 km deep. The reservoir under Napau would be the one associated to the Pu’u’o’o dike which is actually parallel to the main rift line before 1983 and would also make sense that it started reinflating after the Kamoamoa fissure. But the usually accepted depth for the east rift conduit is of 3km, same as the south caldera source so an horizontal conduit in that case.

          I am guessing that height of the fountains will also depend on how much pressurized the magma at the source is, not just depth and gas content, and that would vary a lot.

        • I read somewhere that the 1840 vents apart from the lowest main one were actually normal tholeiite, probably a combination of lava within the caldera at that time (the entire caldera was a single deep and vigorously active lava lake, similar to nyiragongo in 1977) and also magma in the 1832 dike. The lowest vents erupted picrite. The upper vents were also fairly small and more typical in size of a rift eruption than the high volume flows in puna. The dike that fed the upper vents would probably be within the same area that has fed mauna ulu and pu’u o’o recently. In that picture I also probably should have drawn the 1840 dike just underneath the other stuff, it is a bit too deep for that to be to scale.

          I also don’t think it is likely that the rift conduit slopes downwards from the summit so that the far end is at a lower elevation than the start, it is probably completely horizontal or slightly sloped up in general as that is the way it would settle under gravity. The chambers at 3 km deep in the summit area are probably above a general conduit complex that also feeds the rifts and which settles at about 5 km deep. The actual magma chambers which contain liquid magma bodies are probably above an area of hot but semisolid rock that magma leaks through easily and which extends through the seismic SWRZ and east rift up to probably just past pu’u o’o, maybe to heiheiahulu, the area currently experiencing deformation. It likely doesn’t normally extend past there because the distance would probably prevent a dike that long staying open indefinitely.

      • In passing note that in a rising column of lava it may start with no gas in it. As it rises is suffers severe decompression which (if there is enough dissolved gas) cause the gas to precipitate. This reduces the density increasing the uplift force considerably and effectively increasing the vertical acceleration. So a lava that is in complete equilibrium at say 10km is NOT when it gets to (say) 5km, it is very buoyant and exerts considerable upward pressure.

        In my opinion this explains most volcanic systems except the low-gas effusive ones.

        A 10 km (or even a 1km) column of lava with a density less than half of the surrounding rock will gave a very significant vertical force.

        Yes, I know this has been said many times before but I’m not sure everyone grasps the concept. Its rather well shown here (this is CO2)

        and a nice explanation here

  20. Sorry for the rant but Brit journalists are horrible. They drive me to distraction. I’m thinking revenge. I know a press conference in London. Draw them all in and lock the doors. Have Carl and a band of mean and intrepid volcanists lay into them with some good irish oak shaleighlas and teach them whose boss. Not?

    Ps thank you geolurking I’ll try tomorrow. Been one of those days.

    • I think that would be bad for my already high blood pressure.

      Unbeknownst to most people I grew up in a newspaper family business. The paper was one of those small morning newspapers that exist in most Swedish towns and cities. All of those pride themselves of having high journalistic standards and try their darnedest to write as unbiased news articles as possible.
      Most countries with the exception of the UK has that kind of morning papers, even in this digital age.
      What most people don’t understand with the newspaper business is that at a specific time in the night hours you have to have a finished product at all cost, and that product contains enough words to fill a rather sizeable book.
      That fact gives for some rather gnarly decisions having to be made in the late evening in regards of what will be published, and also what length those articles should be given. If there is a lot going on you will end up with many shorter pieces, and on a slow day you perhaps have to milk one or two real news items for all they are worth.
      Then comes the problem with people, because journalists are people. However hard you try you will end up writing slightly biased articles. So you need to know your individual journalist. Also, newspapers over time attain a culture and it’s own set of quirky traditions. This also biases things a bit. Still that kind of newspaper will always try to serve their readers with as factual articles as possible, always ever so slightly failing for what is written above.
      On top of that, journalists are not experts, so errors will crop up now and then.
      The best bet is to read two different newspapers if you are lucky enough to live in a city with two.

      Problem with the UKian press is that they do not even try. Either they fib up an article completely, or they wrangle things until they get the shock and awe effect they wish. I hate it.

      I grew up in an atmosphere where we tried to reach journalistic perfection on a shoe-string budget, well knowing that each day we would fail. The UKian press has enormous resources, and doesn’t even try.

      Now it’s anecdotal time.
      In Northern Sweden during summer time not much news worthy is happening. People are on vacation, happily BBQing if the weather is nice enough. This leaves all the newspapers struggling, secretly hoping for a summer murder, or something.
      If that doesn’t happen you end up writing big center-piece articles about things that normally wouldn’t make even a short notification.
      Those articles are in the Swedish press rooms called, “Olsson’s Cow”.
      If there is an actual cow involved it will have run away from the farmer, and the story will expunge on how (equally summer bored) police officers valiantly chase the happy cow around, trying to catch it before it runs into someone’s kitchen. There will be several pages of interviews with the crying farmer, shocked witnesses, scared kitchen owner’s, the full presidential shebang, on nothing.
      Because in the morning the fat, happy, vacation-lazy, post-BBQ reader will want his big fat newspaper to read. After all, the reader has paid in advance for having his paper delivered every morning.
      Now you know why you sometimes read about cows in the newspaper (or some such importance of local nature).

      • 🙂 somehow just summers full of “Olsson’s Cow” seem to be a blessing now. “How Now? Olsson’s Cow?” my childhood was full of moving and everymorning trying to remember where i was as sleep left me. On to another adventure== Best!motsfo

  21. sometimes it would be an idea to not look at the past of a volcano so much as what it would be like in the future, to work out the present

  22. Interesting article Carl, as usual. What’s your take on Askja? It seems it is responding to Herdubreid (which is a rather loud neighbour to have), and surely is building up to an eruption in the nearby geological future or is it the other way round? It would be a super interesting article about the correlation between Askja and Herdu, perhaps some plots by Andrej? (Just hoping, I know you’ve got a whole lot on your plate)

    • Definitely a nice set of volcanoes to pair off against each other.
      Depending on Andrej I will try to do my best to get something with it.
      Thank you for the suggestion.

  23. ” My personal guess is that it is a function of fresh basalt percolating through a slab of oceanic crust partially consisting of calcite.”

    Could this slab of oceanic crust be an old subducted slab which was subducted during the closure of the Iapetus Ocean?

    I think that a major eruption of Öraefajökull could also pose danger for the shipping traffic south-east of this volcano. Pyroclastic flows can travel over many miles of water.

    • “…subducted during the closure of the Iapetus Ocean…”

      That’s where I put my money at. The neat thing is that it helps to explain the really thick Icelandic crust.

  24. Kilauea seems to have stoped deflating except maybe some very slight deflation that continues at the summit. The JOKA GPS in the upper part of the LERZ (and near the Heiheiahulu shield to be more specific) has been picking up some inflation since the Leilani eruption stoped.

    This supports the idea that the East Rift Zone has not closed after this year’s eruption and that is starting to recover from it. This would also mean that the phase of ERZ activity that has been dominating the summit for the last few decades is not likely to end, this could also mean the LERZ will be affected by future eruptions endangering what is left of Leilani.

    • If an eruption results from this activity I think the highway fissure that didn’t erupt in May is definitely a point of concern. This is very close to the GPS showing inflation and is probably a point where magma reached within a few hundred meters of the surface but stalled out when the dike went downrift again. That magma is still there so it wouldn’t take much, that shallow depth might mean eruption from that location could begin fairly quietly and quickly.

      If it is a small eruption the lava will likely go south to the ocean and possibly just make a small cone like in 1955, it could be similar to the activity from fissure 17, but if it is any bigger then the possibility of lava flowing over leilani again is very high. It also might threaten other areas too as the fissure 8 flow has basically dammed that entire area so the flow will end up going over lava tree park and northwards more towards nanawale, or possibly be diverted south over the southern part of leilani. If this becomes a sustained shield then there is very little chance of anything surviving in either location.

      • In only 1 month the inflation has reached a total of about 10 cm, pu’u o’o took until about 25 cm before it ruptured. That was in part caused by summit pressurization but this inflation center is also closer to a shallow intrusion that is likely still hot enough to be active, which would likely cancel out the former effect.

        This could indicate that an eruption will probably happen somewhere before the end of this year, maybe only about 2 months from now in early December. There is a fairly high chance of it occurring around the highway area, and also becoming a sustained shield vent. At the very least an eruption like the 2011 fissure could be expected, maybe not something huge but probably quite voluminous and with fast lava flow to the ocean and/or over the rest of leilani in a short time period. There would be no significant older magma there now, the new stuff is well within this area so activity there would probably start a lot more strongly than this years eruption did.

  25. Katlas largest holocene eruption is the Vedde Ash event 10 000 years ago. Likley a fairly good sized VEI 7 plinian event that spread ash over large areras of western europe. That event formed Katlas current caldera

    • Actually eldgja was katlas biggest Holocene eruption, vedde ash was its biggest explosive eruption.

      • Both are though small.
        And both are correct. The Vedde Ash is the largest tephra eruption of Katla, and Eldgjá is the largest effusive eruption. But, both are small. Let me start with a correction before expounding a bit on large Icelandic eruptions before you two make Katla into a large volcano. 🙂

        First of all, the Vedde Ash is not the largest ash eruption in Iceland, nor was it even close to a VEI-7. It was a borderline VEI-5 to VEI-6.
        The largest ash eruption was one of the Saksunarvatn Tephras that was a very large VEI-6. Of the five Saksunarvatn Tephra events from Grimsvötn (that gouged out the 3 calderas) 3 of them ranks as VEI-6 and two as VEI-5s. All of them within 500 years.
        In the rest of the world that would have been a small VEI-7, but the Icelandics are stern and go for the 100km3 DRE as a VEI-7 boundary.

        Now over to the Hrauns, or rifting fissure eruptions. The largest such was the Thjorsahraun eruption of Bárdarbunga at 35 cubic kilometres.

        And now to the largest effusive eruption regardless of type. That is the century long eruption at Theistareykjarbunga that consisted of the initial 20 – 25km3 hraun and a following 35km3 shield volcano building phase.

        • A hraun is a large fast fissure eruption
          Laki / Holhuraun

          while a shield in icelandic is a slower Puu Oo like eruption
          Trölladyngja skalderbreidur right?

  26. Katla will likley do a strong VEI 4 or small VEI 5 Next time, it will be similar to Grimsvötn 2011

  27. Back to what icelandic volcano that will be next to go off. It is interesting to look at gps data from around Hekla. If anything, they signals a deflation trend during the lat 3-4 years.
    If that is true, were is the magma going?

    • Maybe that magma is going towards the area experiencing inflation.

    • Ah, Hekla inflation is not looking like normal inflation.
      Just going by the UP-component will fool you.
      Hekla is spreading apart more than it UPs, so you are better off measuring the distance between two stations on either side of Heklugjá (the rifting fissure).
      Secondly, Hekla is sinking at a rapid rate since the edifice is to heavy for the bedrock under it, so one has to deduct that too.
      Few think about it, but Hekla has lost several meters in height since the last eruption in 2010 due to the edifice going down.

      GPSes are marvelous, but they can be a 3-dimensional headache to grasp around volcanoes.

      • Yeah, that wad of magma that wandered off to the South East was weird. I never expected that.

  28. Thx for your insight Carl. I think the problem is deeper though. Trump’s famous fake news. Not quite. More plain laziness in the industry. In Canada almost all the major papers are owned by by one family. Hence the feed is the same. The poor quality is the same. Weeks can go by without a single article on say a country like India. Lots out their it just doesn’t see the light of day in the western press. Basically omission for what ever reason. Lately the printed versions have become so thin and devoid of news as to be undesirable. They have taken to not putting dates on the articles too ( digital versions). Stuff 2 weeks old that the are trying to pan off as new(s). So you end up with history not news. You get old(s) not new(s). That’s the problem with the industry. They have got them selves into a tailspin. Falling revenues and rising costs so something had to give. The papers no longer carry current news in any significant amount. Simply advertising vehicles without the attraction of the New(s). Plus add in the stupid popups and other gimmicks that they use to advertise. Crap. Garbage in garbage out. I use Al Jezeera a lot simply just for this reason. New(s).

    Thx Harley

  29. Im curious on Hekla too.. been 19 years soon since that volcano was erupting.

    LOL And I dreamed of that the chicxulub impactor hit Iceland last Night ( luckly everyone was evacuated )
    The impactor hit vatnajökull, the impact vaporized a 35 km deep.. 190 km wide arera of earths crust.
    Sending a large plume of hot rock vapour 4 times hotter than the suns surface into space.

    Souch an impact woud burrow into the plume head. Imagine the weeks after the impact, crater rapidly buried by flood basalts. Souch an impact in Iceland hotspot woud cause a major eruption after the impact I think.
    Of course the country woud be ruined. The first seconds of impact: earths crust behaves like when you throws a large stone in water. The initial peneration woud burrow into the astenosphere unroofing the plume head. The aftermath woud be fun.. huge release of lava.
    Some of the rock ejecta woud reach escape velocity.. and maybe a piece of Katla ends up on the Moon 🙂

    • Well Your dreams are much more entertaining than my dreams of trying to find a price on a can of beans in a dimly lit grocery store…. 🙂

  30. and there is how Iceland horses walks the moon tomorrow.. how they got there without rocket 🙂
    Jespers sunday planetary geology joke

    And poor Grimsvötn became cratervotn

    • My beloved Icelandic horses will take me to the moon and back any day – you just have to ask them and they’ll do anything for you. Marvellous animals. That’s what caused my love for Iceland in the first place. Then Bárðarbunga threw a party and opened my eyes to the amazing world of volcanoes. Now Iceland is a favourite place on earth for more than one reason…

  31. i Love the education, information and discussion on this board…… Thanks, Everyone! Best!motsfo

  32. … and with no canopy…

    Summary; while taxiing around troubleshooting the electronics, he inadvertently engaged afterburner.

    • Fascinating! I probably walked right past that aircraft at Duxford when I last visited. Thanks for the video.

    • I imagine that this guys pucker factor went off the scale when the afterburners lit.

      Riding 142.34 kN of thrust blasting down a closed runway would scare the crap out of anybody. Pulling back on the stick as he ran out of runway is probably what saved his arse. From the video, a previous (actual) pilot had already had it trimmed for take off. That was also a stroke of luck.

      • Well technically he was an actual pilot as well. The catch was that the fastest thing he had ever flown before was a piston engine tail-dragger training aircraft!

    • Thanks for the link, one of my favourite youtube channels ‘the history guy’ ! Also ‘the infinite monkey cage’ featuring Brian Cox is always worth a listen.

  33. Its a quite crazy and fun topic to think about😂
    Lol its me thinking too much, just some humour.
    Today Im weird.. just having fun. I needs to relax.
    If a KT boundary size asteorid hit Vatnajökull
    Very intresting stuff woud happen
    Of course that will never happen.
    But if it happens there coud be pieces of Katla and Hekla on the moon.
    and whole horses and puffins sent into solar orbit

    The whole Vatnajökull arera and up to Askja and Katla will be erased. The areras outside that will be covered by 100 s of meters maybe a few kilometers of hot ejecta.
    Loots of central Iceland blown to rock vapour.
    It gets much hotter than surface of the sun kinetic impact energy perhaps 24 000 C first seconds.
    And hotspots plume head exposed during the first 2 seconds of impact. The initial peneration woud go down almost 60 km ( crater at 2 seconds )
    But the ground woud spring up seconds later
    When an asteorid hits the crust Earth behaves like a when a large boulder gets town in water.
    This is the process that forms a central peak

    It woud cause a massive eruption, the whole site will flood with impact melt and lava after the crater forms. The impact melt sheet alone are thousands of km3 and Then the later flood basalts thousands of km3 erupted rapidly

    • That would destroy rather more than Iceland! You are talking about a continent-sized sterilization event. Kangaroos would inherit the earth.

        • Oh Lurk, you do realise the extra lyric added to that songs chorus that most Aussies, myself included, can’t help but sing 😉 And let’s not mention Rolf.

          On a different note. I’m currently in Crete and there was a 5 earthquake today – too deep to be felt – but has got me thinking again about the Hellenic trench. Also off to Falassarna tomorrow so the the 365AD earthquake is forefront of mind.

          Examples of Tsumami’s in the Mediterranean are so recent but all but forgotten. Scary to think how an event like that would be today.

    • Transient Crater Diameter: 49 km ( = 30.4 miles )
      Transient Crater Depth: 17.3 km ( = 10.8 miles )

      Final Crater Diameter: 81.7 km ( = 50.8 miles )
      Final Crater Depth: 1.11 km ( = 0.692 miles )
      The crater formed is a complex crater.
      The volume of the target melted or vaporized is 713 km3 = 171 miles3
      Roughly half the melt remains in the crater, where its average thickness is 378 meters ( = 1240 feet )

      At 500 km from the impact site:

      The air blast will arrive approximately 25.3 minutes after impact.
      Peak Overpressure: 384000 Pa = 3.84 bars = 54.5 psi
      Max wind velocity: 437 m/s = 977 mph
      Sound Intensity: 112 dB (May cause ear pain)

      Damage Description:
      Multistory wall-bearing buildings will collapse.
      Wood frame buildings will almost completely collapse.
      Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.
      Highway truss bridges will collapse.
      Highway girder bridges will collapse.
      Glass windows may shatter.
      Glass windows will shatter.
      Cars and trucks will be overturned and displaced, requiring major repairs.
      Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

      • And if it misses and hit water 2000 meters deep, will generate a tsunami 203 to 407 meters high

  34. So thats what woud happen
    If the dinosaur asteorid impact event attacked Grimsvötn😂😏
    now its sleep time here, Im up too late


    Finally after 3 months, a picture of the cinder cone at fissure 17 up close, the most unique cinder cone on kilauea. Still no real sense of scale on how big it is but it looks very sizable, probably at least in the 10s of meters high (probably 40-50).
    It looks like the 2010 fimmvorduhals craters, a strombolian type ashy tephra cone that is rather atypical of kilauea, hopefully something is done to preserve it in some way.


      Also a nice vid of one of the higher lava fountains. I roughly found the time it took for the lava to fall from its peak height was about 6 seconds, so this fountain was about 175 meters high, rather a lot more than HVO said later that day. That also might put the cinder cone at as much as 70 meters high based on other observations and seeing this same fountain on the livestreams and comparing through the tree in the foreground. This is about as good a guess as can be made until someone actually goes and looks at this area properly which might not be for a while until the main road is rebuilt probably some point next year (why does it have to be bulldozed through the new lava instead of built on top of it???)

      • 6 seconds in free fall would indeed give a height of 180 meter. But it should be measured going up rather than coming down as the raining down is clearly not in free fall. I estimated the rising time as 4-5 seconds which is around 100 meters but it is very uncertain.

    • Looks like Etna! And some landowner will want to quarry it, unfortunately.

  36. Actually it was Tom Sawyer in Huckleberry Finn. Painting fences

    • The phrase typically meant “I’m the one you’re looking for” in the time period of the scene. However, it is generally assumed that Johnny Ringo died from a self inflicted wound and not at the hands of Doc Holiday, who by some sources was physically several miles away.

      What I like about this scene, is that the dialog almost exactly mirrors their dialog from earlier in the movie.

      Despite the nit-picking, Tombstone is generally considered to be pretty accurate in it’s portrayal.

  37. Both fissure 8 and 1959 s vent haves a cinder cone look. That’s because the high lava fountains deposited many cooled clasts and not hot spatter

  38. Reading some of the commentary ongoing recently – I didn’t realize how dangerous lake Kivu is…

      • As I said in a previous comment a while ago, “tropical Iceland + flammable version of lake nyos on steroids. It isn’t currently known to have had eruptions this big but nyamuragira is very similar to Hawaii and Iceland and very big eruptions have happened there so it would be reasonable to expect nyamuragira to have the same potential.

  39. Must be city folk piling those rocks. If you’ve every had to move them you don’t want to again. I ran into a heritage book that the local govt. published. Ox trains were running into Canada from Benton Montana at the time of Custer. They had a picture of a group of men around a fire eating with the bald prairie behind.The captionread. Bull whackers on a grub pile. The oldsters had a good sense of humour.
    Thx Harley

  40. Your easy to pronounce volcano just popped a green star…

    • Quality of 90.12… interesting to see what happens when it gets reviewed.

      (Mag 3.2 at 1.1 km depth right now)

      Funny bit is Gurgle translate for Öræfajökull is “The Volcano”.

      Isolating the quake stack from the IMO list under Mount Button {deprecated}, and plotting the list related to time, I get this.

      Maybe one of you Scandinavians can enlighten me. Splitting Öræfajökull into Öræfa jökull, Gurgle yields “Wasteland Glacier.” WikiPokeAtYa mentions Öræfa meaning “without a harbor.” Obviously, Gurgle is going to be lazy and cough up whatever hairball it’s algorithm has to say. Could one of ‘yall provide a bit of meaning and/or context to what the name actually means? Dunno where I ran across it, but I think the name before it destroyed itself was Button or something similar. Probably related to it’s shape before the eruption.

      • After the 1362 eruption, the previously fertile region known as Litla-Hérað was completely destroyed and the region was renamed Öræfi, meaning wasteland/desolation. The mountain/glacier then became Öræfajökull. The old name of the mountain was Hnappafell, literally translated as button-mountain.

      • So it was likely named for it’s shape. I like that. Thank You very much!

      • “After the settlement of Iceland, the fertile plains on the southwest of Öræfajökull were called Litla-Hérað and although isolated, the area was densely populated with twenty or more farms and several churches. (The name ‘Hérað’ was used for a wealthy parish, so Litla-Hérað was a ‘small major parish’.) On the southeast side of Öræfajökull was Breiðamörk, also well-off, where around 900 AD, the settler Þórður Illugi built a farm at Fjall. The farm did well, acquired a church (or the church acquired the farmstead – both happened at times), and a large number of other farmsteads came. At that time the glaciers were much smaller than they are now, and between the glaciers and the coast was a prairie-like landscape with lush grass, copses of trees, and rivers. It must have seemed like heaven.

        And than the disaster of 1362 struck. Afterwards, the land was left empty for over 40 years. When people returned, they called it ‘Öræfi’, meaning wilderness. The glacier took its name from this. Today, the fluvial sand desert of Skeiðarársandur borders where once the paradise of Litla-Hérað was.”öraefajökull/

    • I noticed the liquefaction.

      Based on Alberts provision of the high tide time (albeit outside the bay, which is relevant) and the information provided to me by Antony Colas, I think we have a stronger possibility than landslide with the addition of extreme tides and local bathymetry.

  41. Hi Folks, Good morning from Dublin.
    Im usually playing catchup on reading this blog in the morning but did anyone else spot the two Mag 3 quakes under Öræfajökull this morning/last night. Here are the details

    Date Time Latitude Longitude Depth Magnitude Quality Location
    01.10.2018 23:24:16 63.990 -16.634 0.1 km 1.7 99.0 3.7 km SE of Hvannadalshnjúkur
    01.10.2018 23:19:36 64.000 -16.640 1.1 km 0.6 32.18 2.7 km SE of Hvannadalshnjúkur
    01.10.2018 23:15:40 63.999 -16.597 1.1 km 3.2 90.12 4.5 km ESE of Hvannadalshnjúkur
    01.10.2018 23:15:40 63.992 -16.638 0.1 km 3.1 99.0 3.4 km SE of Hvannadalshnjúkur
    01.10.2018 23:07:39 63.997 -16.648 4.2 km 1.2 32.86 2.6 km SE of Hvannadalshnjúkur

    The quakes look quite shallow so possible the ice/glacier re adjusting? However they are associated with a samll swarm with some deeper dept (4km) picks up yesterdays star in Bardy and a samll swarm following it.

    Regards to all from a long time reader and just an occassional poster.


    • I think it’s only one quake. It appeared first as M3.2 with a quality of 90.12%. After manual checking, it became M3.1, but the old entry was not removed. This happens from time to time and usually the one with lower quality disappears later in the day.

    • One thing that is good to keep in mind is that IMO never includes ice quakes in their lists. Many of the larger quakes have been really shallow. It has been suggested that they might be small phreatic blasts, but I think the most likely cause is simply tectonic quakes caused by stresses induced by the ongoing inflation.

      • Will be interesting to follow Ørae will continue to ramp up its activity!

    • In an eruption, the flow is mainly liquid with some gas. In gas wells, it is mainly gas with some liquid. An eruption can stop when there is too little gas left to provide buoyancy, when the pressure drops too far to keep the dike open against the pressure of the surrounding rock, or when the head forcing the pressure drops below a critical value. The latter seems to have been important for Leilani because the eruption began to stutter before stopping completely.

  42. bardy is jalous “Today the 2nd of October a M3,6 earthquake was located at the north-eastern caldera of Bárðarbunga volcano” (IMO).

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