Bárðarbunga… A restless giant

I got the honour and privilege to be the author of the first blog post of 2018. So let me take this opportunity to wish all our readers, visitors and the managing team a very happy and healthy new year.

 

The Bardarbunga eruption in 2014 was impressive in many ways. It was a rifting event, it took place more than 40km away from the magma source, it jumped fissure swarms, it was the largest eruption by mass and volume in Iceland in the past 230 years, it erupted ~1,6km3 of lava over ~85km2 area and it is responsible for one of the best recorded cases of caldera collapse in the world, and the first in Iceland since the Askja collapse in 1875. The gradual caldera collapse of Bardarbunga was very energetic, with many earthquakes above M4/M5 on the caldera ring faults, caused by the centre floor dropping, as the magma was transported out of the magma chamber under it, and lasted for the duration of the eruption.
In the end, the caldera floor dropped by 65m at the lowest point and over ~110km2 area in total (area of minimum 1m subsidence). But just a few months after the eruption, when all seemed to quiet down, the caldera ring faults have reactivated with a growing number of M3+ earthquakes, that continue till this day.

In this rather short installment, I would like to shed some light on the post-eruptive seismic patterns of Bardarbunga, compared to the caldera collapse seismicity during the 2014-2015 eruption, while keeping it as simple as possible with mostly my own graphical presentations. The data I am using is from the manually checked/corrected earthquake catalogue from IMO Iceland.

The intention of this post is not to make theories or over-assumptions, but just to present the data as objectively as possible. I am not a professional volcanologist/seismologist, but just an amateur/enthusiast, with the passion for volcanoes and geology, more specialised in producing plots/graphics rather than making deep theories and thesis’s.

There are 30+ graphics in this post (28 + 1 video of my own work), so give it some time to load everything.
Now that all the disclaimers are out of the way, we can begin. 🙂 

 

2014-2015 Caldera collapse

On August 16th, an earthquake swarm began between Bardarbunga and Kistufell. On 17th and 18th August, the swarm focused more on the area around Bardarbunga, specifically towards the SE end of the caldera, from where a lateral dike has formed towards SE. After going 10km SE it made a 90° turn towards NE, and by August 20th, the dike path was already 30km long, with an estimated volume of around 0.25km3.

Image by: Andrej Flis

The magma that was already in the dike and was on its way towards NE, most likely came from the magma reservoir under Bardarbunga. Judging by the seismicity signature, the magma source for the forming lateral dike was between 10-14km depth, as seen on the cross section below. Under B there is the likely inward dipping caldera ring fault, with a lateral extension of earthquakes between 10-14km depth, where the likely magma outflow path was. The direction and shape of the seismicity corresponds to a transport dike, with the seismic “tail” being only 0,5-1km wide, when going into the turning point. There is a possibility that some of the magma was also transported from a deeper source.

Image by: Andrej Flis

With the onset of the seismic swarm and the formation of the lateral dike out of the magma chamber on August 16th, deflation was also being recorded on the same day, as a response to the magma chamber being drained. But the caldera ring fault seismicity was low from August 16th and 19th, despite over 0.2km3 of magma already being drained. The reason was likely the initial elasticity of the intra-caldera floor/magma chamber roof, from here on being simply referred to as “the plug”. Another indicator of the elasticity of the plug, was the fact that it had a smooth deformation surface, meaning that it did not develop any visible concentric ring faults, which would also appear on the ice surface, and would also have a seismic trail at the surface. There was though seismicity within the plug itself as the stress fields were highly altered. Smooth deformation was also likely due to the high aspect ratio of the plug, being taller than wider (6-8km wide and 10-11km tall). Such an aspect ratio of the caldera plug, provides a better internal stability (support) and can withstand more deformation before developing bigger internal cracks/concentric faults. That is compared to a very low aspect ratio caldera plug/floor, like at Grimsvotn (4-6km wide and 1-2km tall), which is subjected to many cycles of rapid inflation/deflation, and can become a major problem down the line, when once such cycle of stress will exceed the structural integrity of the magma chamber roof, and a new larger explosive caldera forming event is possible.

Image by: Gudmundsson et al., 2016

On August 20th, the elasticity limit of the Bardarbunga caldera plug was likely reached and stronger earthquakes began appearing on the north and south ring faults. This was likely the date of the plug drop/slip onset. By August 28th, activity increased, as the full ring fault was fully activated. First to have major earthquakes was the southern rim, which was likely under a bit more stress since the magma began the outflow from the SE margin. The activity soon began on the north rim as well, and was alternating between north and south without any specific pattern, with more energy release on the north rim.

The eruption at Holuhraun began on August 31st.

Image by: Andrej Flis

At this point, the plug drop was acting as a hydraulic piston. It was responding to the reducing pressure and volume of the magma chamber due to the eruption, but at the same time, as it was dropping and pressing onto the magma chamber, it was increasing the pressure in the chamber and the outgoing dike due to compression. With the individual fast drops of 20-80cm, that were accompanied by M5+ earthquakes, measurable pressure waves were sent across the dike from Bardarbunga to the area of the eruption, from the pressure increase as the plug was pressing down. So simultaneously, the eruption was driving the caldera collapse, and the caldera collapse was driving the eruption. A rather rare, but perfect synergy.

Image by: Diego Coppola,  M. Ripepe,  M. Laiolo,  C. Cigolini & Sigmundsson et al., 2015

On September 13th, a GPS station (BARC) was set up on the caldera floor,  which was measuring the descent of the caldera floor, together with aerial radar and satellite measurements. The rate of decent was nearly exponential, and was perfectly correlated with the eruption rate at Holuhraun. This, combined with petrology and seismic analysis, is a solid proof that the magma source of the Holuhraun eruption was from (one of) the Bardarbunga magma reservoirs. The end and start of the caldera collapse was also well correlated with the eruption/magma transport.

Image by: Mariel Dirscherl, Cristian Rossi, 2017

 

Seismic structure

 

The seismicity during eruption was very energetic, and left behind a very distinctive pattern of ring faults. But ring faulting is never just a simple straight line. Nevertheless, two distinct general faults have appeared, on the north and south rim. The magma reservoir under Bardarbunga was modelled to be displaced/expanded a bit towards N/NE at depth, relative to the volcano surface. This is also likely the reason why the north ring fault has a slight outward dip angle (80-85°) and had mainly thrust faulting, while the south ring fault has a near vertical dip (85-90°), and had mostly normal faulting. And it is also likely why the west margin of the caldera had weaker subsidence gradients and less strain build.

The subsidence gradients were also strongest on the north ring fault, as the plug was being pulled N/NE under the rim, which also causes more strain with the surrounding crust. The NE outer rim actually recorded some uplift as the plug was sliding under it, and slightly pushing the overlaying crust upward. While on the south ring fault, the plug was being pulled straight down or slightly away from the rim and the surrounding crust, and had less strain, compared to the north ring fault.

On the next image we can see the approximate angles of the ring faults on the western caldera margin, and a very nice outline of the plug. B is the north rim and E is the south rim. The north rim is much more noisy and has an outward dip. The south plug has an average inward vertical dip, but is a bit more complex down lower. Some intra-plug seismicity is seen, as a response to stress fields within the plug itself.

Image by: Andrej Flis

Next image shows the same field, but only M3+ earthquakes. This outlines the fault orientations a bit better, since it shows the area with most strain build/energy release.

Image by: Andrej Flis

Going over to the eastern margin, things are just as complex. The fault angles are mainly the same, except for the north rim, which perhaps has a bit more outward dip down in the bottom half, especially in the bottom third, where the angle increases even more and where there is coincidentally more strain release. The south rim retains the same angle.

Image by: Andrej Flis

Storage…

When looking at seismicity, I can’t help not to look for patterns that might suggest where the magma reservoir is. The petrology, deformation and gas analysis for Bardarbunga have all put the magma source with confidence at around 10-16km depth. That is not the actual location of the magma chamber, but just the outer error margins.

Looking at the seismicity from two different perspectives, we can see a slight sign of a seismic discontinuity between 12-15km depth. It is not a seismic free zone, but it is a clear change of pattern between upper and deeper activity, and agrees with the model depths and sizes (ellipsoid-sill-like body). There was continued deeper activity under Bardarbunga during eruption, indicating a possible upward magma transport as the magma was flowing out of the chamber which was causing under-pressure in the chamber (though quickly mitigated by the plug drop).

Image by: Andrej Flis

A cross section on a W-E axis also shows a near seismic free zone around the same depth, and where the outflow conduit was towards E/SE. But magma reservoirs are never of a perfect shape and can be very complex.

Image by: Andrej Flis

Looking only at 13-16km depth, there is a void under the caldera, getting complex towards NE.

Image by: Andrej Flis

The eruption lasted for 181 days. Despite the plug acting as a compressing piston, the overall pressure was reducing as more and more magma was leaving the reservoir. The whole system reached an equilibrium of pressure, and the eruption ended on February 27th 2015, leaving behind a very bright seismic picture.

Plot by: Andrej Flis

 

The aftermath…

 

After the end of the eruption, there was continued low magnitude seismicity in the dike path, as the magma cools and slowly contracts. The seismicity also continued around the caldera, both around and at the ring faults. An M3+ earthquake was more an exception than a rule. But that rule changed in September 2015, when M3+ earthquakes became a regular occurrence. But it went further, with M3+ earthquakes that were getting nearer to the M4 mark. And in 2016, the M4 earthquakes became the new regular periodic occurrence. Till this day (2nd January 2018), the strongest post-eruptive earthquake at Bardarbunga, is an M4.7 on the north ring fault, at around 5km depth. There can be many causes for the increased seismicity, or all combined to some extent. Either the inflation under the volcano pressing upwards, the still active ring faults as the plug is continuing to adjust, general tectonic stresses, interactions with the stress fields of surrounding volcanoes and deformation, etc… The caldera collapse was a violent event, and it takes some time for the ring faults to fully release all the strain, especially since the ground in Iceland is constantly on the move.

Plot by: Andrej Flis

Plot by: Andrej Flis

North vs south, east vs west….

If we now take a look at the seismic profiles of Bardarbunga post eruption, we can see a similar but not the same picture as during eruption. Below is a vertical cross section of the west margin of the caldera. On the right display you can see how the stronger magnitudes nicely outline the caldera ring faults. I decided to use all magnitudes, to show a much better contrast between the ring faults and surrounding stress fields. On the left, I have outlined some of the vertical trends, mostly fault dip/orientation. It is of course much more complex that a simple straight line. The north rim has retained the same general angle, while the south rim got a bit of a deformed look, with an inward/outward dip complex from 6-10km depth. It almost feels like there would be an external force pressing towards the structure on a SE->NW axis. I have added possible chamber/sill outlines.

Plot by: Andrej Flis

Going to central area, things normalize a bit. The north rim has the known fault dip, and the south one is also closer to eruptive look. But there is still the dip anomaly below 6km. Here I have also added a potential sill location/s.

Plot by: Andrej Flis

Moving over to the east, this is the region that has retained most of its eruption days dip angles.

Plot by: Andrej Flis

Looking at the specific rim fault, they have a generally normal look, with a slight bias towards east with depth. It retains the same general shape and orientation as during the eruptive/collapse phase.

Plot by: Andrej Flis

The full profile on the image below, shows the deeper activity, likely magma transport, and we see the upper structure of Bardarbunga. The known magma storage is around 10-15km based on gas, petrology and ground deformation data. The new source of deformation and seismicity could be the same magma storage that provided magma for the 2014/2015 eruption which is getting rejuvenated, or could be a deeper sill storage. The whole deep system of Bardarbunga is not well known/understood. What is certain, is that Bardarbunga sits almost directly on top of the Iceland plume, and it regularly receives fresh material from the mantle, more-so during plume pulse phases.
Now another potential anomaly in all this, is seismicity that is a bit away from the caldera rim, but connected to it on the north side. It is a batch of seismicity towards NW, trending away from the foot of the ring fault. It looks like a continuation of the ring fault, or an associated stress field. But it is not entirely impossible that it is a response to the changes in the stress field due to an inflating body. Its orientation is NW/SE.

Plot by: Andrej Flis

The GPS deformation vectors (detrended) do confirm a deeper source of inflation around Bardarbunga. Iceland Met office has also confirmed that inflation has started soon after the eruption, based on all the data they have at their disposal. The closest station (KISA) has recorded around 80-100mm of uplift since the end of eruption. But the area is tightly packed with volcanoes, so the interpretation of deformation should not be linear. There are many potential sources of deformation, together with general plate tectonics.
There is no known (or public) information about the depth of the caldera floor or any potential recovery since eruption. Such accurate observations cost money, which is usually granted when there is a confirmed/realistic risk of an immediate eruption or danger to public safety. Bardarbunga is currently not posing an immediate eruption risk, but it is being closely monitored, since it is showing signs of a steady post-eruption recovery.

Background by IMO, post-eruption vectors by Andrej Flis

Trends…

 

Having a quick look at the post eruptive trends at the Bardarbunga caldera. We could see above that the magnitudes have a general positive trend. It goes the same for both the north and south rim. I have added simple linear trend lines on these graphics, just for the sake of better orientation. An interesting point is July 2017. After that, the amount of M3 earthquakes has reduced, but the amount of M4 earthquakes has increased on both rims. This generally means that the earthquake magnitudes and energy release has increased, despite the reduction of M3 earthquakes. Likely some colder/denser/stronger material is being cracked. Future activity will show if this is a new trend or a phase.

Plot by: Andrej Flis

Location wise, it is a very interesting story. Both on the north and south rim, earthquakes (M3+) have a slight NE trending. This likely has more to do with general plate tectonics, than anything coming from Bardarbunga itself. The strongest easterly trend is on the north rim. Sometimes this can be used as a “passive GPS” signal, but one has to consider all the tectonic factors that can influence such a signal.

Plot by: Andrej Flis

Plot by: Andrej Flis

Looking at depth, we had a general trend towards deeper earthquakes. But just like with M3 quakes above, after July 2017 the depths somehow reduced. After a 3-month break, the depths are slowly increasing again. Something has likely changed in July 2017, or some point was reached.

Plot by: Andrej Flis

As far as energy release goes, the north rim has a big advantage over the south rim. That is reflective of the caldera collapse phase. The northern rim fault has an outward dip angle, has thrust faulting and so interacts much more with the overlaying crust, building more strain. I used a basic energy release formula for this, and modified it a bit. But the numbers are not as important here, since the focus is mainly on the trend and ratio of the energy release between the north and south ring faults.

Plot by: Andrej Flis

Speaking of faults, I mapped approximate outlines of ring fault during and after the eruption. It is based on M3+ seismic data, and is just an estimate, since in nature, faults and especially ring faults can be very complex. So I call this a graphic of “potential” faulting. The collapse faulting had quite a circular shape, outlining the overall rim faulting caused by the caldera collapse. Since it is color coded, it shows the slight outward dip angle on the north rim, while the south rim is more uniform in angle by depth.

Plot by: Andrej Flis

The post eruptive faulting is a bit less circular and more disperse. South rim still has a similar angle at the eastern side, but it has anomalies on the western margin, just like I showed on the cross sections higher up in the post, 6km and deeper. The faulting here does not reach so deep, since there was much more motion and strain in the stress field during the eruption and during the caldera collapse.

Plot by: Andrej Flis

For the post finish line, the full profile image shows a comparison between eruption and post eruption vertical profile of the caldera, using M3+ events. The most obvious thing is that the southern ring fault has moved north by a full kilometer, which was also partially seen by the latitude and longitude trends on the graphics above.

Plot by: Andrej Flis

The best way to slowly end this (now rather long) instalment, is by putting everything into a seismic perspective. I made an HD plot, that shows the seismic past of Bardarbunga, back to 1995, or at least as much as it was recorded in the IMO earthquake catalogue. There is a general lack of weaker magnitude earthquakes up to around 2011. That is generally known as a “technological skew”, a term I borrowed from Carl. It basically means that the apparent lack of low magnitude earthquakes prior to 2011 is an artificial signal, because the seismograph network was not dense/sensitive enough to record lower magnitude events compared to recent years.

Nicely seen is the period of frequent deeper intrusions into the system between 2006 and 2011. It is reaching down to around 25km sharp. Why such a discontinuity at 25km depth? It is possible that the feeder system up to that point is semi-open, meaning that magma can perhaps creep upwards without much seismic noise, through pre-existing dikes/paths. It can also mean that the crust below that depth is hotter and more elastic/ductile, not being able to accumulate a lot of strain.

Plot by: Andrej Flis

And this would not be a fully graphical post without a video/animation. I have made a simple spin-around video of the Bardarbunga seismic profile, using post-eruption data. The M3+ earthquakes are magnified and have green-reddish colour gradients by depth, which shows the north-south ring faults.

Bardarbunga will eventually erupt again one day. That is (almost) a mathematical certainty (unless the magma source somehow cuts off). The fact is that the 2014/2015 eruption caused a few changes in the system and in the stress fields around the volcano. It will take many decades for Bardarbunga to replace all the lost magma volume with fresh material. But it will take much less time to get the magma reservoir pressure back to pre-eruption levels, thanks to the caldera collapse, and the plug which somewhat mitigated the post eruptive under-pressure in the magma reservoir. This means that once the reservoir goes into over-pressure, magma will likely try to find a new path out of the reservoir. Basalt magma is known to be hot and generally “liquid”, which gives it good flowing properties. It means that it is easier for basalt to find a weak spot and to crack out of the magma reservoir in a lateral (or any) fashion, rather than erupting vertically from a ring fault. At the end, just like water or air, basaltic magma will flow down (or up) the road of least resistance.

This gives two possible scenarios for future eruptions.
-One, is another lateral dike event, similar to the last event, with unpredictable development, since it depends on the size, depth and the direction of the lateral dike. 
-Second, is the possibility of an eruption upwards through the ring fault. There was a lot of motion and cracking and energy release on the both ring faults, north and south. There is a chance that once the magma reservoir is over-pressurised, magma can now move upwards if it finds or cracks a way. This largely depends on the strength of the host rock around the magma reservoir, compared to the integrity of the ring fault on the bottom. Both faults are much more fractured than before the 2014/2015 eruption, but at that point the magma was already flowing out of the chamber via the lateral dike/outflow, and had no chance of going upwards, while the lateral outflow was open. 
Another thing that favours the ring fault eruption is the faulting. If i had to chose which ring fault could transport magma upwards easier, i would go for the south one, no questions asked, and I will explain why… 

Looking at faulting mechanisms, we see that the north rim has reverse faulting and was pulled under the surrounding crust, heavily interacting with it. That is why it released much more energy, since there was also much more strain build, because it was under compression, while pushing/pulling the plug wall and crust wall together under a steep angle, really grinding each other away.
The south rim on the other hand, has a slight inward to vertical dip angle, and was sliding down and away from the surrounding crust, which was causing extension. There is still wall-crust interaction, but since there is normal faulting and extension, there is not as much strain build as on the north side where there was more direct and violent interaction between the plug and the crust.
This leads me to believe that it would be much easier for magma to creep upwards through the south rim, since as it is under extension, it would be easier for magma to find openings or to make its own path/cracks, opposite to the north part which is being pressed together. It is still possible for magma to move up on the north side, but it would take more effort. There are cauldrons in the ice on the south and east side of Bardarbunga, and even steam coming out of the cauldrons. That is also an evidence that the rims are geothermically active, with likely magma and heat transport.

An eruption through the ring fault would most certainly be explosive, at least at first, as the magma would intersect ice, which is always an explosive combination.

Bardarbunga caldera ring faults Plot by: Andrej Flis

Bardarbunga is tho more known for its massive fissure eruptions, like 8.600 years ago, when it produced the largest flood basalt since the end of the last ice age, with lava flows going over 100km, all the way to the south coast.
Just before the settlement of Iceland, Bardarbunga created a dike, over 50km long, towards SW, that reached all the way to Torfajökull volcano in 871 A.D.  It caused an explosive eruption, sending ash across Iceland. There was enough ash, that it left a distinctive mark in the soil, known as the “settlement layer”.
In 1477, Bardarbunga did it again, this time with another eruption from the Veiðivötn fissure swarm.

Another big flood basalt is always an option, but at this point it is not very likely. Though with another plume pulse arriving, or already beginning, one can never fully dismiss such an option somewhere down the line.

This brings us to the end of the first post of 2018. I hope and know, that there will be lots more to come over the year, and for many years to come….

For Volcanocafe,

Andrej Flis, (Down Under @Recretos)

110 thoughts on “Bárðarbunga… A restless giant

  1. A fantastic, detailed and informative read, Andrej! Many thanks for that. It must have taken ages to put together. Perhaps the IMO should hire you?

  2. Great observations Andrej. And awesome plotting! Thanks much.
    I’ll come up with some questions, but must read the article again first … ☺

  3. I’m being a bit of a jerk right now. I’m sitting here enjoying a hot cup of coffee and musing of how nice it is that I don’t have to stand quarterdeck watches anymore. The way it is lining up, it’s gonna be a horrible mid-watch for anyone on duty in Mayport NavSta over in Jacksonville. NWS has a winter storm warning out for Tallahassee all the way over to Jacksonville up into Valdosta GA area and out to the Atlantic. I’ve had my share of freezing my arse off late night watches, I don’t envy them. Up i Jersey, I used to keep the Messenger of the Watch occupied by having him go out on the brow to chip the ice off and lay salt. Don’t need any one going plop into the water ya know.

    • ever have enough to roll the boat?? Happens up here with crabbers… and You have all our cold weather… it was 44 this morning and it rained all night…. gobal hotting. 😉

    • The only time I was in a wind field that could have had that intensity, was in the formative stages of the 1993 ‘nor’easter. We had gone out for engineering training in preparations for certifications, and the pilot remarked to the captain about his temerity for heading out in such conditions. (It was clear and sunny when we pulled away from the quay) As soon as we cleared the outer channel marker, we had two full days of unrelenting wind and seas as we steamed south. With a pretty large “sail area” (the superstructure) some on board were musing that the reason that we wouldn’t turn around was because of the combination of seas and wind making it unsafe to do so. The entertaining bit was listening to the radio traffic of a Nato flotilla further out to sea trying to coordinate sending their smaller units to safe harbor. We had it fairly tough, so I am really certain their smaller unit were getting beat to shit and back. (we were 533 ft long and pulled 8520 tonnes displacement). I’ve ridden out a hurricane on a 441 ft Frigate (Hurricane Iwa – 1982), so I know they were pretty beat up. If you take a look at the USS Goldsborough Wikipedia entry, we were ship in front of them when they had that fatality. (Two others washed over the side, but they were recovered alive the next day. One on the beach, the other clinging to a buoy.) Rumor had it that one of them (the one on the buoy) was one of their deck division officers.

      Ref the ’93 Noreaster. I found out years later, that while we were putzing around out there, I had a cousin on her honeymoon on a cruise ship out in that crap. Word is she spent several days puking. Can’t really blame her though, it was quite rough. As for stamina, I have a step daughter who can get sea-sick while moored pier side. I’ve seen her do it. (Dependents day cruise. She was laid out on a bench in my shop puking into a trash can) The funny bit, is after we cast off and got underway, she perked right up as if nothing had been wrong.

      In my experience, the main issue with heavy weather is not hurting yourself as you are moving about. Rule of thumb, “Always keep one hand for yourself” That way you can at least avoid smashing your face into something that hurts.

      • Hubby had asked and he really enjoyed Your response and stories about Your jobs on the High Seas. 🙂 Best!motsfo

    • Heh… In port, engineers get stuck on in port deck watches occasionally. Sure, they usually wind up with engineer specific tasks, but when your section is strapped for manpower… well, things happen.

      (And yes, I was a twidget.)

      About the worst thing that I know that happened to our engineers, was when we picked up that floater outside of Jebel Ali. We stored the body just aft of the breaks in front of the ventilation intakes for the plant. Not a good day to be in main-control. We had figured that by recovering the body, they would bring us in to port quicker. It seemed they could care less and we still had to wait our turn. Turned out he had dissapeared somewhere along the river at Dubai about a week before.


      For those wondering what the @#$ we are talking about, MMs are Machinist Mates in specialty. Usually they work on things that require the judicious use of wrenchs and other implements of destruction. Their typical workspaces are quite hot and noisy. (Ships Power Plant sort of stuff)

      Their use in augmenting the watchbill is usually quite rare since they are better employed in engineering specific tasks. Underway, they stand engineering watches exclusively. Inport, they are generally part of your front line Repair Party members. (Fire Fighting teams) Along with any other engineering rates {specialties} in your duty section.

      • Why? → They (engineers) are the most familiar with the equipment and repair lockers on board and they receive extensive training in shipboard firefighting and damage control procedures.

        • The worst part of the job, was the heat in the engine room (engineering spaces are cooled from outside air which off the coast of Oman can be over 100f) and having to work only 2 hours at a time to minimize heat stress. The second worst part is that while in port and we had to keep the plants on line we usually only had one day off at a time (due to lack of manpower in engineering divisions) while other divisions could have multiple days off while in port.

          The best part was being forward deployed in Youkuska Japan and in 2.5 years at sea was able to visit 18 different ports, many multiple times, Including 5 ports in Australia, 2 in Korea, 3 in Japan, Diego Garcia, Hawaii, San Diego, Subic bay Philippines, Hong Kong, Pattya Beach Thailand, and Guam.

          I was able to watch the last active f-4 Phantom fighters to fly off the Midway before her retrofit to move FA 18s on board. We were the first American warship of size (DDG-9 USS Towers) to navigate inside the Great Barrier reef starting at Cairns and I think we came out at Brisbane. Our Captain and crew did not get much sleep during the transit. Oh, and the stars at night!

          Mac

        • I agree about the stars. One “fun” past time was spotting Iridium flares and spooking the lookouts about them. My bane was our EMC. He came up to combat once after a near load drop and was bragging to me that he had kept the 400 hz MGs spun up during the event. He “only” had a 540 VAC transit. (which literally cooked my spike arrestors and caused a CASREP for parts so we could dig a supply clerk up to go get it out of a parts bin.) I’ll not go any further than that, but it got complicated fast over the following weeks. (which eventually led to me unintentionally cooking one of his MG sets) {yes, it was actually unintentional and not “unintentional.”} I had warned him about changing his normal at sea configuration and he didn’t listen. The battle doctrine said to go full on in that circumstance, so I did. MG set go >>poof< <


          • For anyone following and Geo, a “mg” set should be a motor generator set? Those twidgets might have there own language.

            I also remember the (might not be the correct term) glow from the props disturbing the bioluminescent plankton.
            mac

          • Yep, motor generator set… but not a twiget term. That was straight from the EMs…. but, in the snipe world, I guess they are twigets also. 😀

  4. I can remember reading somewhere that the lava from holuhraun was very primative/ unevolved magma that was of mantle origin (I mean freshly arrived from the mantle and not stored in a magma chamber).

    The caldera data seems to be pretty conclusive that the eruption was from under bardarbunga but would that fit the magma composition? I have seen it suggested that the area that is now (on here) called greip might have been a second source of magma. If that last bit is true, because greip is apparently on the grimsvotn swarm then holuhraun would be an eruption fed by two different volcanoes.

    • Being so close to the plume head could skew Bardarbungas magma towards a more juvenile nature.

      • This is a likely option. Also during the eruption, there were deeper earthquakes, which could indicate an active magma transport of fresher material during eruption.
        But one thing to consider us that there were massive intruaiona under Bardarbunga from 2006 to 2011, and the magma wont evolve much or at all in just 3 years. Of course there is magma mixing, but not al the erupted material was fresh. And the analysis did show where the likely source was, based on pressure or gases for example, which gave a fairly good results of 10-16km. Now the bottom end for that is already likeky in the fresh material transport zone under Bardarbunga.

        As far as Greip goes, it is an individual feature, a discontinuity, and was actualy completely quiet during eruption. It is an unlikely source, since it doesnt have a seismic trail that would indicate that, and in the end it is tilted slightly away from the dike.

      • And I found an old quote from IMO: “The magma that comes up is a rather primitive basalt, with a chemical composition typical of the Bardarbunga volcanic system.”

        So the chemical composition was typical for that of the Bardarbunga system, and was rather new, which is likely from the massive intrusive period from a few years prior.

  5. Thanks Andrei, beautiful! Will take some nice exciting reading time to suck all of it in!

  6. So can any ‘predictions’ be made from the data about how the next eruption might play out?

    • In one of Jons old posts from about November, he uses the fact that there are ice cauldrons with exposed rock as evidence for magma within the caldera faults, which could erupt quickly without warning. I would tend to agree because it only started after inflation restarted.

      I guess the fact that inflation started only a few months after a major eruption shows the real power of this area. I would doubt the next eruption is more than a few years away. The next holuhraun-sized eruption probably is a few decades off though, and probably to the southwest because that area hasn’t rifted in a few hundred years.

      I can remember reading something that the 1447 eruption wasn’t actually much bigger than holuhraun (2-3 km3 magma) but because of the ash it was much more widespread. The paper that was from shows that eldgja and skaftareldar were much bigger volume-wise than any of the veidivotn eruptions except the one that made the thorsja lava. Seems like really huge fissure lava flows in Iceland aren’t entirely related to rebound depression melting, but lava shields are.

      (Il find the paper and put it in another comment below this one)

      If anyone knows more about what I said above I would like to hear it/expand my knowledge😉

      • The volumes of the largest fires are discussed in our Eldgja series: http://www.volcanocafe.org/the-eldgja-eruption-icelands-baptism-by-fire/ (see the third instalment). The model attempts to explain why the largest eruptions are all around the 20 km3 mark. About half of all Icelandic lava comes out in the Dead Zone. An eruption to the southwest from Bardarbunga can be larger than those to the northwest because the area there is at lower altitude.

        • In the paper I linked it says that actually about 70%+ of holocene lava is from the east volcanic zone, with about half of that from thorsja + eldgja + skaftar fires (which would be about 60 km3 of lava + about 10+ km3 of tephra).

          (This is all based on a table in the paper I am referencing) Apart from thorsja all of the major veidivotn eruptions (like 1447) are around the 1.5 km3 – 2 km3 of lava mark (like holuhraun), although the eruptions also had significant explosive activity which meant not all the magma erupted as fluid lava so there was more than the above numbers. I am assuming you used different and probably newer sources than the one I found which is from 2003. All the studies later than that were on payed sites which I cant really get to.

          I do agree that the lower elevation to the south is probably some of the reason for the bigger eruption size. I think Carls idea of direct mantle connection being a key factor why some of the eruptions in the dead zone are beyond anything elsewhere also fits my idea too, as the description of the start of the skaftar fires includes subplinian eruptions and 1.5 km tall lava fountains which seems more likely if the magma is very new instead of from a crustal magma chamber. Maybe bardarbunga does long dykes from near the hotspot, but the grimsvotn swarm behaves differently and skaftar was a vertical eruption?

          This is why I like posts on Iceland. The only other place on earth like it is in northern Ethiopia, but that is hard to study for lots of reasons and isnt really anywhere near the magma supply rate of Iceland (no flood basalts).
          Iceland volcanism is unique and new things are discovered all the time (last article is an example).

      • Before reading that paper I was under the impression that we were currently in the waning stages after the glory of the early holocene, regarding eruptions. But that data shows that if anything a big lava flood is actually more likely now than any other time really. But at the same time also shows that a veidivotn eruption isnt necessarily going to be bigger than holuhraun, just more ashy. Unless grimsvotn decides to do something unexpected in the near future after pulling off an almost-VEI 5 in 2011 (one of Carls posts about it had him say that it could be fully recharged from its caldera eruptions in the early holocene, as well as the 1783 eruption, I dont know if he would still say that though).

      • So I guess it seems that we’re (possibly) heading for an eruption scenario that we all thought was going to happen last time before the fissure opened (when the Aviation Code was put on Red briefly).

        • Well if the ice is thin (which it seems to be) then it will probably be more lava than ash unless the vent is within the caldera basin where the glacier is much thicker.
          I dont think an eruption from the central volcano would be that big though, definately not as big as big as some of the news was saying in 2015. If a big dyke goes southwest though it could be a different story but that is probably something for later this century etc.

  7. The elephant in the room is that we currently have a large influx of juvenile magma mixing into whatever lies under Bardarbunga. The questions is whether or not the pressure relief mechanisms (rifting and plug piston) are sufficient to prevent overpresurisation.

  8. I know I have been asking a lot of questions for this post, but I have one more 🙂

    Given that the cauldrons on the southern rim of the caldera actually have exposed bedrock, that rim seems to be shallow (or the cauldrons are way bigger than I thought). That might mean any substantial eruption either on the ring fault or just outside the caldera would probably last long enough to become completely subaerial. During the gjalp eruption I think the last bit was a little subaerial cone as an island in the melted glacier lake. But that was in deep ice between volcanoes. A similar event (but probably smaller) on the edge of bardarbungas caldera might actually get through the ice completely and make a new table mountain and little subaerial shield or cinder cone. Im sort of rambling a bit but with all the potential activity to happen in the near future its all for a good reason 🙂

    http://www.ruv.is/frett/gat-i-gegnum-jokulinn
    Here is the cauldron with exposed bedrock (from 2nd September last year so it might be snowed over a bit now but snow isnt much for an eruption).

  9. A very nice overview, Andrej! I would add two things: (1) the exponential subsidence jumped to a faster decline around early October (I will have to look for the plot – it was not noted in the literature). Is there any indication in the earthquake data for a change around that time? (2) The shift in location of the south earthquakes seems important. That puts the new stress inside the plug.

    Last time I looked (quite a while ago) the new earthquakes avoided the precise areas of the eruption quakes. So it was not just movement in the opposite direction. You suggestion of a horizontal stress field may fit that. The pressure inside the plug has decreased by rho*g*h where h is the amount of subsidence of the caldera, and rho is the density of rock, while the pressure outside has not changed. So there is now a net force pushing the rock inward.

    • I think it actually slowed down somewhere between mid September and early October. I also think the decline was quadratic and not exponential. This is most obvious when looking at the subsidence rate. The rate declined linearly (with a change in slope), which is consistent with a quadratic subsidence. The quadratic fitted model accurately predicted the end of the eruption, while the exponential model didn’t.

      I found an old picture I made, where I estimated the subsidence rate. I think that each point in the graph corresponds to the average slope over one week around the point. Sadly, the scripts and data disappeared when I changed my computer.

      • I did not go deeper into the subsidance rate. I did write that it was “nearly exponential”, since I was not too sure, and I dont have raw subsidence data to do my own modelling of the rate.

        What confuses me, is your graphic. You said that the quadratic model better predicted the end of the eruption. But on your plot it is actually the exponential line that accurately predicts the end of the eruption (end of February), while the quadratic one goes well beyond it. Unless you have an error in the line name. 🙂

        • Look again… 😉

          Blue is quadratic. Left plot is the subsidence given by the actual GPS level. It levels out right at the end of February. Right plot is the subsidence rate, i.e. the derivative of the GPS level. It reaches zero at the end of February, i.e. all movement stops. The exponential model still has a negative slope and a non zero derivative, which means it’s still alive and kicking.

          • Oh, its a bit confusing since the subsidence is in raw elevation and not in actual subsidence rate. 🙂

            Funny enough, Haraldur Sigurdsson, the boss of volcanology actually used an exponential model, and accurately predicted the end of the eruption within two days, and correlated the subsidence rate to 99% with the actual observations. I dont remember what exact formula he used, but it worked.

            But your data seems convincing too.

          • This is Haraldur Sigurdsson post from Dec 2014 thru Giggle Translate unfortunately.

            ‘ve previously mentioned in my blog that the Bárðarbunga seal follows an incredibly good curve or process, as shown in the graph above (data from the web site of the Meteorological Office). The curve is best described as a polynomial correlation with this equation: y = -0.0012x² + 0.4321x. The internal correlation of the curve is R² = 0.99946. This is an incredibly good correlation. If all the puddles lie on the curve, then R² = 1.0000. It is very unusual for events in geology to follow as well as on a regular basis any development line. Probably it will only happen when a very big event is involved, as the bottom of the Bárðarbunga caldera crumbles regularly into the crumbling deep into the crust. Probably this landscaping, which is about 10 km in diameter, is about 8 km thick, which smears, or more than 600 square kilometers of rock!
            It is noteworthy that this regular curve turns off, ie. It has been reducing the situation since the beginning. This gives us a unique opportunity to estimate when they leave, which is probably also the time when kvika stops out of the chamber and the eruption stops at Holuhraun. I have extended the curve to the development line, with the equation above, until it becomes horizontal when it stops. It will take about 170 days after the measurement began on September 14th. The curve predicts the eruption at the end of February or early March 2015. However, there are many factors that can affect the fluidity when reducing power, especially resistance to the dyke under Holuhraun and more. All these factors work towards the eruption of something earlier.

    • Thanks for the feedback! 🙂

      The rate of earthquakes does not seem to change much to be honest. It was constantly fluctuating. I guess one should do a plot of energy release to have a better idea.

      Here is the plot from the post for the eruption period for the Bardarbunga area without the dike.

      ?resize=1024%2C564

      “rho*g*h” – Thats a good one. Its interesting we got to a similar conclusion, by different roads. 🙂

  10. Gatorcicles? Snow in the Okefenokee. FHP reporting weather related road closures in that area.

  11. This is very very impressive work.
    Can´t imagine how much time you must have spend plotting. But big thanks. 🙂

  12. Below is my fit to the subsidence of the Bardarbunga caldera, made during the eruption. This is based on the GPS data, which is not necessarily the place where the subsidence was largest. The black line shows the data. The bottom panel shows the fit. There is not quite enough data to constrain the parameters completely. But as Tomas also noted, a single exponential can not reproduce the full decline. I used two. The first is up to day 49 of the eruption: here the time constant ( where the subsidence reached about 65% of the total) is 44 days, and the total subsidence at the end of time would be 24.5 meter. After day 49 the curve changed, and now the time constant was 72 days and the total subsidence 42.5 meter. It is as if something gave way inside the caldera allowing for a large drop but with more damping. That may have been only at the GPS location: it is always a problem if you only have data at a single location.

    The exponential decay comes naturally if the force pushing out the magma scales with the weight of the rock above. As the rock drops, the force gets less and therefore the drop become slower. This equation predicts an exponential decay.

    Now an exponential deca never completely stops. But physics introduces another limit. The magma has to stay liquid between the reservoir and the point of eruption. During the transport in the dyke, it slowly cools.If it goes too slow, it will solidify near the exit and the eruption stops. The speed of transport depends on the eruption rate which depends on the weight of the rock pushing it out. Both decline with time.

    The same process gives rise to the shield volcanic cone. As the eruption rate diminishes, the lava cannot flow as far above ground, because again it solidifies faster. So the lava now stays close to the exit point, and as a result the shield grows higher at the centre. You get a shallow cone. On Venus, you see what happens if this doesn’t work (in that case because the air is so hot the lava solidified very slowly): you get a pancake shield instead of a cone shield.

    Addendum: The equation given by Sigurdson, y = -0.0012x² + 0.4321x, is in fact the first two terms of a series which approximates an exponential function. His version gives a decay time scale of 140 days which is longer than I found. He probably only used the first 85 days of data (after that the GPS went off-line until after he gave this equation), and therefore the timescale wasn’t yet well determined. Also, the series ideally needs a cubic term as well.

    • I thought that the pancake volcanoes on venus were determined to be silicic eruptions, and that they would have been VEI 6-7 calderas on earth but the atmospheric pressure prevented explosive eruption?
      Pancake domes are big for lava domes but lava flows on venus can be gigantic in some cases so I think if pancake volcanoes are basaltic they would look like normal shield volcanoes.

      • The composition is not known. The suggestion that they are silicic (which is how wikipedia classifies them) comes from the appearance: it is easier to make such well defined features from viscous lava, and on earth that tends to be silicic. Whether that is also the case on Venus is not known. (and on Earth, silicic flows do not form pancakes.) Measurements on the ground by the Russian Veneras only found basalt, but those were not done on the pancakes. But is is clear that the biggest difference with Earth is the extreme temperature. Lava flows on Venus can extend for thousands of kilometers, purely because they cool so slowly. It is natural to expect that this has also affected the pancake flows. They behaved more like a lava lake than a lava flow.

        • “silicic flows do not form pancakes”
          That may not be true in all circumstances; I recall that the late Peter Francis described a volcanic landform in the Andes consisting of a roughly circular, craterless body of (usually) dacite, with a roughly horizontal top surface and steep margins – he named them ‘tortillas’ from their appearance. Haven’t got the reference to hand, sadly, but it was in one of his books

          • One of them is called the chao dacite, and it is 20 km long and over 500 meters thick. It apparently formed about 100,000 years ago. The Andes has extremely thick crust for a volcanic area so maybe that is where the volume of degassed silicic magma for this came from.

            Are the pancake volcanoes on venus in highland areas? If venus is like earth in composition then it is entirely possible that it had plate tectonics in the past and that highlands are continental. Continental crust is silicic which would provide volume.

          • http://volcano.oregonstate.edu/oldroot/CVZ/chao/ – chao dacite flow

            Pancakes on venus might also form on flatter ground so the lava spreads out instead of flowing in one direction. And silicic lava can flow under its own weight when cold, like a glacier, as shown at puyehue-cordon caulle in 2013 after the eruption stopped. Chao was apparently erupted over a period of (~150 years) and I dont think the lava at the front would even be hot anymore by the time the last lava was erupted. Venus is not much colder than rhyolite that is considered molten (600 C) so in effect silicic lava is almost an ambient liquid there and would flow further. Maybe some longer lava flows on tall volcanoes on venus are actually andesite or dacite which was effected by this.

            I think carl was planning to do another post on the altiplano supervolcano complex at some point this year and big flows like this might be important to know about. Chao is the biggest but theres WAY more of them around nearby (probably the ‘tortilla’ formations referenced above).

          • The pancake domes are found in the lowlands of Venus. Often they come in groups. Venus has no plate tectonics (and has not had any since at least its last global resurfacing event) but it does have continent-like highlands. Whether they are continents remains to be seen, and they are not related to the pancakes.

            Pancakes are often found near coronae. That may give a clue since those are thought to form when a large plume heats and melts part of the crust. Coronae are unique to Venus, although there are suggestions they could also form on icy moons.

            Venusian crust is basaltic. There are suggestions that basalt can behave as required for a pancake if the lava is very gas-rich. Basaltic lava is rarely viscous but it can happen.

      • I am not sure we know! The sigkatlar formed before the main eruption, above the southeastern dike but I think did not do much after the eruption began.

  13. A long time ago, in a place far far away (Jersey), I had a dog. “American Eskimo” breed. A solid white fluffy dog that originally had authority issues with me. Anyway, this is an excitable breed and pretty active. Before he died, he did have a stint at playing in the snow in Jersey. He was downright gleeful. He had finally found a situation where his coat blended into the environment. As he was frolicking, when he lay still, all you could see were his eyes and a little black nose.

    Here’s to you “Sparky.”

  14. I am finally thawing out a little bit, now I’m sitting here watching ice and snow in Boston and Virginia Beach, (yes I have better things to do).

    • Since the discussion has turned to the snow, I live in SE Virginia (Norfolk), and I don’t know what the official total was but we’re digging our cars out from about 8-10″ in our yard/driveway.

  15. A good friend of mine is a building manager on Long Island. According to him, he is growing quite tired of the “Bomb” characterization of this storm and hears it non stop in conversations and on TV-Radio. Sure, it’s a technical term that describes the intensification speed, but it has become a media buzz-word, much like that horrendous media term “Super-(whatever).”

    His main issue? Getting the snow removal contractor on site as soon as they get an appreciable accumulation in the parking lot… and keeping the slip and fall lawyers at bay by denying a place for their potential clients to have their much sought after calamity. That’s also the reason they have so much video surveillance and recording.


    Meanwhile, in Florida, it’s sunny. We have a “Hard Freeze” warning in place, so that’s good. (well, good come Spring, it lowers the bug population) We’ve been needing one of these for a while. The last time I experienced one first hand in Florida, I was still a firefighter. Nothing quite as bizarre as getting up to go change out your air bottle and finding that your turn-out gear has the pliability of plate armor. Some of us got our butts chewed out for leaving a remote part of the building burning so we could stay warm. County Fire relented and had a heated bus brought in for us to use.

    • The reason I posted this is due to the sign warning of possible Hydrogen Sulfide the area. Just up that road are some old “borrow pits” that are now used for the disposal of construction waste. Sheetrock usually has a high quantity of Calcium sulfate, as it decomposes, it has the potential to release sulfur gases. A more vexing problem is that since construction refuse goes there, it’s not uncommon for some idiot to use it as a place to (illegally) toss their household garbage. Due to this problem, many of those construction debris yards have video surveillance. Just before that small bridge is the entrance to a rock chipping operation that breaks up concrete debris. The photo was taken from in front of the local UPS distribution center which is to the right of the frame. Just beyond the corner of that road at the far end, is a favored registration check area for FHP. Unless you read about it being active in the paper, you don’t see it until you make the corner. Effectively, you are trapped and trying to turn around to avoid it is REALLY obvious to the officers there. That virtually guarantees that they will come get you to find out why you were trying to avoid them. The ones I encountered were actually quite nice. I didn’t have my paper registration handy so they just ran my tag and were happy that it came back a valid. (Printed on the decal is the actual registration number in small print along with the date code. Decal thieves usually don’t consider that. It’s a dead giveaway to being invalid or stolen.)

  16. What is going on in the Katla caldera? >10 km line of quakes spanning the caldera, most very shallow but one at 5 km magma chamber deep. No low frequency tremor but somewhat elevated at high frequency. Crack in the caldera lid?

  17. Heads up for volcano watchers. Monday-Tuesday might be active days if Sod’s Law has anything to say about it. I will be indisposed and unable to watch, monitor, calculate, or plot. (surgery) However, you do have Andrej Flis, there is more than enough skill there to keep a plotted eye on whatever happens.

    • Thanks. In keeping with the oddity aspect of it, maybe we’ll get a full on trap formation somewhere. Hopefully someplace relatively safe, like axial seamount.

      • Full on trap formation in two days? Must be some surgery. Good luck with it and hope the discomfort goes away swiftly.

        • Hekla erupts with little warning and probably with much less than 1 day in advance. It also looks capable of some pretty big lava flows – mini flood basalt 🙂
          If it has been able to erupt after just 10 years recharge then its already at a point where it could happen at any time. Maybe it is waiting until its surrounded by forest again so it can destroy it all >:)

          On its notoriously short warning signs, apparently before the 1845 eruption there were tremors and other signs of eruption up to almost a day before the eruption happened, which I guess is still very short warning but much more than the half hour of the 2000 eruption. That eruption was also after over 60 years instead of 10 though.
          Maybe heklas next eruption might happen to the north of the central volcano along its fissure swarm, like in 1878 and 1913, which were actually quite substantial eruptions with both being about the size (a bit smaller) of mauna loa’s 1950 eruption in volume and apparently relatively unnoticed so possibly with little warning. Even smaller ‘flood’ basalts…

          I went back to Carls hekla series before, and it looks incomplete/there was mention of a later part of the series on the last article.

      • Nix on the Axial Seamount, please!
        The Pac NW fisheries are in enough trouble as it is.
        There is decent “circumstantial” evidence that the near collapse of Salmon, Steelhead, Cod and other commercial species (estimates were that some offshore populations plummeted nearly 75% for many species) coincided with a large subaerial eruption(s) near the Axial Seamount in 2010 and again in 2012. Given that this area is also in the heart of the N-S flowing California current, it’s logical to consider that toxic, acidic effluent spread may spread throughout a large area of the NE Pac.
        That Salmon from all the west coast drainage areas suffered equally, and that even baitfish disappeared as well, the entire food chain was affected…so local stream/river conditions cannot be entirely blamed on the collapse. Note that EPac Ocean Temps were not unusually high/low then, which in the past has been known to disrupt the food chain, but apparently not in this case. Also note, that despite terrible inland river conditions, we’ve seen a decent recovery of baitfish and Salmon since then (with a big help from a 2 yr. fishing moratorium in 2013-2015).

      • Very true. But everytime I hear a percentage statement about outcomes, I can’t help but think of the law of large numbers. In a nutshell, the more times you test for a specific result, the more likely you will eventually find it. (Boolean trial) That tidbit of knowledge about stats drives me bonkers.

        My cousin told me to lighten up, and pointed out that the majority of my mom’s cousins and relatives, lived past 90. Baring misadventure and such, the odds should be in my favor.

    • Yeah, that is startling. But the mass ejection rate is not that far from a group of kids throwing rocks.

      • Caveat: A very large group of kids. The ejection rate based on the VAAC report is about 0.6 m³/s DRE… or about 1620 kg per second.

        Figure a large class of 30 kids throwing 54 one kilogram rocks per second… each.

        (Yeah, they would have to have superhuman speed and strength to keep that up for any stretch of time… but its still not a large eruption.)

    • Just like with last year, starting off this year with a volcano having its first historical eruption.

    • I gather from one of the links there is a village on the crater rim. I hope they move out – pronto.

  18. Agung has been steaming a lot today. There was a lahar earlier, so I expect there was quite a bit of rain around the summit.

    • Happy NY everyone and good article Andrej – many thanks.

      A quick Q wrt Agung. If we were to take the stance that the eruption stops right now, how long is the crater likely to continue steaming? It is half full of fresh lava and i’d assume that it would take sometime to cool down, so every time it rains we are likely to steam plumes. Would we be talking about weeks, months or maybe a year or more?

    • Mostly a rough guess, but I estimate that somewhere between 2 to 3 times the energy of Tsar Bomba was extracted/dissipated in heat energy from the top meter of the ocean along the trek of the storm along the Gulf Stream. Coupled with the shindig at Bezymianny on 20th Dec, it might make for a chilly spring in Europe.

      • I don’t know whether those estimations show how small our nuclear weapons are, or actually make them seem bigger. On one hand, annual natural events happen often and easily exceed nuclear bomb energy levels, but on the other hand the tsar bomba was only the size of a small (but very heavy) car, while to get that much energy out of a storm it has to be at least subcontinental in scale. Makes us seem small either way.

        On the topic of the tsar bomba, how big would an eruption have to be to reach similar energy release? I think I asked a similar question once but not as well put out.

        • A rough approximation can be made by comparing maximum plume heights.

          One thing to keep in mind though, is that a nuke blast is a single pulse of energy and a volcanoes full power output covers a longer period of time. Summing the power output rate over a volcanoes eruptive episode usually winds up being quite large. It’s akin to comparing one cars speed with how far another car traveled. They don’t compare well though both metrics are concerned with motion.

          • so nuclear bombs are much more powerful over a given time period than any eruption then, but because eruptions can last much longer they have much larger total energy.

            (I can remember a figure somewhere on this site that has krakatoa in 1883, pull off a 150 megaton explosion during its peak/when it went caldera, is that actually a thing?!)

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