Volcano forecasts and Campi Flegrei

Solfatara crater in Campi Flegrei happily steaming away.

There are a few volcanoes that I do not feel comfortable writing about, and those are volcanoes that are far too close to large human settlements. The reason is obvious, it is far too likely that I will write about an event that will kill a lot of people.

There are two ways to increase the safety of those who live in these volcanoes, the first is mitigation. This can be divided into passive mitigation like evacuation plans, hazard maps and so on and so forth.

The second part is active mitigation, here the goal is to through engineering change the properties of a volcano so that it is less dangerous. This practice is so far rather uncommon, the shining example is of course the Ampera Tunnel at Gunung Kelud in Indonesia. The goal of the tunnel is to remove the crater lake that historically has killed ten thousand people. There is obviously more to be done in the fields of both passive and active mitigation.

The second part is accurately predicting if and when a volcano will erupt. But, before we get into this there is a bit of semantics I wish to clear up. I have over the last five years become ever more uncomfortable with the term “prediction”. It implies that you are using tea-leaves or fish-entrails instead of stringent scientific principles and empirical data to form predictive models.

I hereby suggest using the term “forecasting” instead, after all the common man is already used to weather forecasts, and forecasting volcanoes is in a way the same thing, and soon it will be as commonplace.

The science of volcano forecasting

Map of Campi Flegrei showing seismic activity and centre of uplift. From Chiodini et al, linked below.

There is not a single field in science that has advanced as quickly as volcano forecasting has done since professor Páll Einarsson accurately predicted the 2000 eruption of Hekla to within a minute of the actual eruption time.

Today forecasting of volcanoes are done on a routinely basis for many volcanoes. But, still far from all. The reason for the lack of volcanic forecasts for all volcanoes on the planet is due to lack of scientific research about them, or a lack of data-collecting equipment.

For well-studied and well-monitored volcanoes that we have a good track-record of and that does not erupt almost all the time we have at places achieved an accuracy of 8 out of 9 accurate volcanic forecasts. That number is better than weather forecasts, who would have figured that 20 years ago?

The first thing you need is a long track record of how that particular volcano acts during an eruption. Secondly you need data to analyse. Different volcanoes lend themselves to different types of data collection and equipment. Out of this data you make predictive forecast models so that you know what to look for before the next eruption. Then you sit down and wait.

The next part is to acknowledge that volcanoes can behave in unexpected manners, therefore you need to study how other volcanoes of the same type have behaved. This will give ideas for how to change your modelling if you encounter anomalous data from your equipment.

Volcanic gas changes at Campi Flegrei, picture from Chiodini et al, linked below.

There is a wealth of different techniques and equipment that can be employed against a volcano. The most common pieces of equipment are seismometers and GPS-stations so that we can look for volcanic type earthquakes or movements in the ground under the volcano. Quite often this is enough to forecast a volcanic eruption.

The golden rule for all forecasting, and almost all science, is that the more different types of data you have to work with the better your forecasts will become. Therefore there is a barrage of other equipment types used. They range from borehole strainmeters, gas-chromatography, water-sampling in real-time, LiDAR, magnetic resonance measurements, gravity anomaly data and so on and so forth. To put that into perspective, Páll only needed an old paper-seismometer back in 2000.

There is also another golden rule to remember, and that is that the more frequently a volcano erupts, the harder it is to forecast the next eruption. The reason behind this is that a volcano that has not erupted for a while will be “noisier” than a frequent erupter, just compare Bárdarbunga to Etna and you will get the picture.

After an eruption, a volcanoes conduit cools down and start to veld shut, the longer the time, the harder this “veld” will be. The seismic crisis at Tanganasoga in El Hierro at the Canary Islands lasted for months since it had not erupted for such a long time. At the same time Etna will just give away a little bit of a tremor increase before its paroxysms (at best).

But even at these frequent eruptions you can often see changes as fresh magma enters the system. Between the 29th and 31st of December 2015 I detected anomalous seismicity at Fuego in Guatemala that pre-empted the larger than usual New Year’s eruption.

This is not the time, nor the place, to write about every single detail of how to forecast a volcanic eruption. Instead it is time to move forward to the volcanic forecast for the Campi Flegrei area. In other words, will there be moderate lapilli-fall in the afternoon?

Campi Flegrei

The new fumarole at Acocella. Photo by Carmine Minopoli.

There is another reason that I do not like to write about some volcanoes, and that is that there is a high likelihood that certain expression able English tabloids will run amok with the story and unduly scare people. So, careful phrasings are of a premium in this case.

Lately there has been two highly carefully phrased scientific articles about forecasting of the Campi Flegrei caldera volcano. The first one dealt with changes in gas chemistry in the Solfatara crater and the other dealt with inflation in the caldera.

As magma intrudes into a large caldera system that is geothermally active the intra system pressure will increase and the gas chemistry will change. In the paper, they see gas volume increase and changed composition as a sign of increased pressure against the over-burden (caldera roof), and that is the same way (but different) that I used for Grimsvötn and Bárdarbunga. But, for those two I used Cumulative Seismic Moment to calculate the pressure increase.

The end result is though the same, that one knows that magma has entered the system and that the pressure is nearing a critical threshold where the roof of the magma reservoir can no longer withstand the pressure increase. Or in simpler words, boom.

On it’s own this is not enough to prove that an eruption is moving closer. Instead you need other tests, one of those employed at Campi Flegrei has been electric conductivity measurements, and those also point towards changed chemistry associated with pre-eruptive behaviour as water higher in electrical conductive materials is squeezed out of the ground.

Now, someone will be saying that these are not the normal things to look for in a volcano before eruption. And that would be correct, these are two new ways to detect and interpret changes in large caldera systems. Obviously, they need to be checked against the more mundane ways to predict volcanoes.

Changes in volcanic fluids. Image from Acocella et al.

If we instead look at changes in GPS-station trajectories we see that there lately have been an intrusion and subsequent inflation out in the bay part of the caldera. This is not that unusual for Campi Flegrei, there has been several quite large intrusions in the last 7 decades indicating movement of fluids or magma. The difference is that the previous intrusions has failed to change the gas chemistry indicating that the magma did not reach a sufficiently shallow depth to be an indication of an upcoming possible eruption.

There are more details in the papers listed below for those who wish to get a better grip on things. The interesting thing is though that there seems to be a consensus on the increased risk for a minor eruption at Campi Flegrei.

Or in other words, there is a forecast for Campi Flegrei that is spanning a very short geological timescale. It states that there is currently a 50 percent risk of a minor eruption occurring within the next decade.

I can feel a lot of our readers groaning here who wished for a more distinct forecast. But that is not the point of this kind of forecast. Instead it is a warning to the relevant authorities to prepare evacuation routes, prepare hazard maps, and to hold relevant exercises. Because whatever we do, we humans can’t stop a volcano from erupting, we can just try to find out when and where and prepare accordingly for how to haul ass away from the eruption when it occurs. It might also be prudent to move away artwork and statues that will be destroyed by the eruption. But, that is about all that we can do.

Aerial photo of parts of the Campi Flegrei caldera.

For those who wish for more distinct forecasts, I am certain that those will become more exact as we come nearer to the upcoming and rather inevitable eruption at Campi Flegrei. The final part is where the eruption will occur, and the size. Currently it is too early to pinpoint location and size of the eruption. But, still we can say a few things.

The level of current activity compared to historical data gives at hand that an eruption would not be large. This could obviously change if a new larger intrusion occurs. Currently we are most likely looking at a VEI-2 to VEI-4. Quite enough to ruin a portion of the town, but not large enough to endanger the region, and even less so the country.

There are currently two areas that are more likely than other areas, one if the hypocentre out in the bay. This would make it a subaqueous eruption with a minor risk for a local tsunami, and it would be likely to produce an ephemeral island, or even a new permanent island.

The other location would be an eruption at Solfatara since this is the point centre of the changes in gas chemistry. Either way, an eruption could occur at other places inside the caldera, and we would not know the exact spot until days or even hours prior to onset of eruption.

Final thoughts

Campi Flegrei is a beautiful place to visit.

Forecasting a volcano on the scale of Campi Flegrei, and with the population density of the city centres involved is like watching a train-wreck in slow-motion. There is nothing you can do to stop it, but since the speed is so slow there is time to prepare and get off the train by simply stepping off it.

Prior to the eruption there will be ample warnings given by the INGV, the risk is not that they will miss the eruption, the only risk is that they will give the warning to early, or that the volcano will quiet down again. And making an error on the side of caution is not good when the real eruption comes around the corner since people will be less likely to haul ass.

I just hope that the population and the politicians involved realises that we are talking about the evacuation of every single human inside of the caldera.

In other words, the INGV knows what they are doing, I am not so certain about the politicians. So, here is a suggestion. Politicians like to be sent on tax-money to vacation spots. Send them all to study Gunung Kelud and the stellar work that the local politicians did in Indonesia.

In Indonesia politicians and scientists working hand in hand mitigated one of the world’s deadliest volcanoes having a highly explosive eruption into only killing two people. There is no better example on the planet to study.

What is my personal opinion about all of this? Well, I believe that the risk is lower than 50 percent for the decade. But that is a belief and beliefs have nothing to do with science, so I will return to Campi Flegrei shortly together with Andrej Flis to remove the belief.









Last weeks riddles seems to have been a bit hard. Two of them are still remaining, so I am leaving them for this week. I also awarded to bonus points for giving alternate answers that fit the riddles, but was not the one I was seeking, but gave explanations that fit the tee.

This week also features one riddle inspired by Andrej Flis, and an image riddle. Good hunting!

Name Last week’s points Total
Daisaster 1 3
Bjarki 1 2
Thomas A 1 (bonus) 2
Albert 1 (bonus) 1
Bobbi 1 1
KarenZ 0 1
  1. Wild Rhomboid Whale (Draconian green coated whaling station in island nation, the real caper) – Brava in Cap Verde, answered by Spike Page
  2. Western Sunny Art (Pipes and drums exiting away from Macbeth in the land of the Queen) – Ardnamurchan i Scotland, answered by Chris Cookie Cooke
  3. The Feline Dreamer – Katla,
    answered by Albert
  4. Badly constructed (pythonian) towering (creosote) pig – Pico Basilè, answered by Spike Page
  5. Picture Riddle (Island sulphur mounds eating city) – Soufrière Hills in Montserrat, answered by Bjarki

128 thoughts on “Volcano forecasts and Campi Flegrei

  1. 2: Badly constructed towering pig. Guess
    Suswa volcano, a pig is an animal of the genus “Sus”, the mountain is somewhat towering at 2,356m in height. And the construction seems to be somewhat unusual.

    • Your explanation of your guess was almost as convoluted as my riddles, I had to read it thrice. Me like, but no… 🙂

  2. Leave it Dai. Don’t look.
    Oh damn can’t help it.

    5. Picture riddle

    He’s a fan and the castle was used for the Tale of Sir Lancelot in Monthy Python.

    Cue Carl ….’Nope not even close’!

  3. 2: Badly constructed towering pig. Pico de Orizaba.

    Considering your unhealthy love for puns/wordgames, Pico=Pig. It’s Mexicos highest mountain, and it has had several edifice collapses during its construction.

  4. 3: The Feline Dreamer : St. Catherine.

    Cat(and such feline) is short for Catherine. St. Catherine is the patron saint of young bachelors, maidens and students (who always dream of a bright future).

    I’ve fallen into the same hole as Daisaster(although he seems to have better brains for this kind of stuff than me), this is addictive and you Carl is cruel.

  5. 3 – The Feline Dream

    Santorini – they have lots of cats and there is a fable that they dream of being worshiped again as they once were in Greece.
    There is a also a luxary hotel call Dream Island here.

    I am guessing too simple for Carls mind!

  6. Great post Carl. But just to play contrarian, I want to debate whether small intrusions = small eruptions all the time.

    Lets take a different hypothetical scenario where there is a large magma chamber that is 99% primed, close to a point of overpressure. In this scenario, small intrusions could cause small earthquakes and small changes in the volcanic system that would indicate a forecast of a small eruption. But what is not readily apparent is that the greater volcanic system beyond the intrusion has been at capacity and ready to erupt for a while. When said intrusion breaks the surface and the volcanic system rapidly transitions to a state of under-pressure, that could potentially lead to a bigger eruption for the existing volcano, beyond what the intrusion would lead on to believe. Now just to be clear, I do not really think this is the Case at Campi – history tells us to expect small to medium sized eruptions here by and large, but I hesitate to say anything at all conclusive.

    • Hello CBUS!
      Contrarianism is what brings knowledge and furthers science, so I am game.
      In this case we fairly well know the amount of magma that has entered the system during the last few eruptions thanks to the steadfast work of those pesky archaeologists. Ie, we know well how much uplift there has been, at what times those uplifts has occurred and during which times deflation has occurred.
      We also know the magma composition of the last eruptions.
      That magma was fairly depleted of volatiles and more consistent with dredge from the large VEI-7 eruption with partial fresh melt intrusion.
      Comparing the small intrusions that has happened now with let us say the Monte Nuovo eruption gives at hand that so far the magma composition should be roughly the same, even though the amount of intruded magma now is less than what intruded back then.

      That being said, if a VEI-4 occurred at the center of uplift and that part of the caldera is weakened there is the risk, albeit small, that water could enter the magma reservoir at the end of the eruption and a Krakatau event would happen. The risk for that is though small.

      I would also like to point out that I am not into writing things that could make the Daily Fail et Ilk go ballistic scaring people needlessly by hyperbolic writings.

      In the end, I am quite convinced by the reasoning in the papers cited that a larger eruption is highly unlikely. But, I will just in case do a bit of heavy lifting together with Andrej in a while and see if I come up with anything contrarian to the papers.

      • Good reasoning, and I definitely tend to agree. Especially in this case where there is historical evidence to back up the somewhat more frequent mid-sized eruptions.

        With that said, I tend to believe that for certain volcanoes, this is far less clear. Especially an under-studied volcano that doesn’t have the historic eruptions. Documenting past intrusions is a real thing for Campi Flegrei, but take a volcano like Agua (near to you), we simply wouldn’t know if there has been constant historic intrusions dating back 1000 years. If we were to see a new small intrusion in this example, we wouldn’t know if this was the first of said intrusions, or one of hundreds of similar intrusions that has occurred over the past 10,000 years. With this, we also wouldn’t know whether the magma chamber has a lot of eruptible magma or if it’s much more solidified. But alas, such is the trouble with volcanoes – we can’t really peak inside the magma chamber in any easy manner.

  7. Alas, no luck as of now with the riddles. I will be off in a little while to do my friday prayers (drink beer and play darts), so dings will be handed out tomorrow.

  8. #3 Is it Michoacán-Guanajuato volcanic field..there is a pyroclastic cone there called Cerro Gato (the cat hill) and it is asleep..perhaps dreaming of being polygenetic?

  9. Number one: I offer Sverrefjellet which is in Spitzbergen. Not erupted for a long while. Greenland whaling had a bit of a punch up between Dutch and English, and the Danish, too. Town of Smeerenberg and Bowhead Whales figure. OK I’m clutching at straws…

  10. Picture puzzle: Rabaul on New Britain. It was called ‘fortress Rabaul’ during the war. I don’t need to point out the similarities between Rabaul and brexit.

  11. …that moment you realize you’ve spent a half-hour looking for riddle answers and forgot to have breakfast.

    3 – Komakatayama –…though a cat in a coma would likely not dream.

  12. #5 Etna? But that’s only based on one picture, of Bodiam Castle (is it Bodiam?). There’s a poem references Etna so probably wrong.

  13. 4. Kelimutu volcano on Flores Island, Indonesia. Flores is a breed of pig. Kelimutu has 3 craters and 3 lakes that change color. I don’t know if that qualifies for “badly constructed” but it sure is weird

  14. #4 Ol Doinyo Lengai. Thinking pig iron which is poorly constructed, brittle, and full of carbon

  15. I think Solfatara itself is unlikely to be the location of the next eruption. It is a place where ground water circulates deep enough to become heated and come out as fumaroles. That does not in itself provide a magma pathway. From the number of craters in the area it seems that eruptions tend to break new ground. The earthquake swarms may give a better indication of where the pressure was building. Near Monte Nuovo may be another option. That is if it does develop into an eruption. It may still end as a failed eruption. Failure is an option.

    • Personally I agree with you on this Albert, but the papers stated it as one of the likely spots.
      I think that Campi Flegrei will follow pattern and have an eruption in a new spot inside the caldera, or adjacent to the caldera wall.

    • Bearing in mind the size of the at-risk population, Naples area does not appear to be over-endowed with GPS stations. Or have I missed a map ?

      • It is actually quite well endowed, but they are sneakily hiding most of the endowments.

        • I wonder why…
          Ever the cynic….. are the authorities who issue eruption alerts as free from over-arching “business” interests as they should be? My expectation is the dead hand of cam***a holds sway.

          • Oh they are, and there is a map somewhere that I have lost. The INGV is fairly straightforward, albeit not as publically determined as the IMO.

  16. Ok, apologies in advance for any duplicate answers as I haven’t quite caught up on all of last week’s post but could #2 be Hatton Rockall basin /ridge … There’s quite a lot going on in that area as we all learnt recently.

      • I know there is an Icelandic legend ‘Katla’s dream’ although I don’t know what is in it (vikings and violence?). But I may have had an unfair advantage on this riddle! Should I donate the ding to charity?

        • Nope, since it was A cat in lala-land, alleging to the Sandman-mythology.
          You are not getting away from your points Albert, and you did not know the answer or have any undue advantage.

  17. Did I get a DING or a smoke-free cigar for my guess at No 1 back on 00:18? I’m really keen! (my first potential successful answer… 🙂 )

  18. Im having a wild guess here for number 4. “The volcanoes of Workington ” where the cliffs of pig iron have made a feature around the local feature “castle ” house. I was thinking of Edinburgh castle but alas, it had been taken

  19. #2: Vulcano? There’s a Sunny Art Center in London that is located in a former home of Sir Francis Bacon *and* a site where Shakespeare once performed his plays. There has been speculation that Bacon may have *been* Shakespeare. Shakespeare’s last work of solo authorship was The Tempest, which takes place primarily on or near Vulcano, part of Sicily’s Aeolian Islands.

    On the other hand, Bacon was an opponent of Scottish independence in his time …

    • Oh… If you had kept to the theme but avoided Vulcano you had probably gotten it. You have given yourself all the clues ever needed in your own answer. 🙂

      • Google isn’t finding me much. There isn’t (apparently) one actually beneath the Sunny Art Center itself. Sir Francis Bacon had some early musings about plate tectonics but isn’t associated to any specific volcano, it seems. There was a film made of The Tempest that used Hawaii as a filming location, but that raises the question of which volcano?

        The “pipes and drums exiting forever” clue fits only one on Hawaii: the Punchbowl, located near Pearl Harbor and site now of a cemetary with a lot of dead WW II soldiers. Taps is traditionally played at military funerals using pipes and drums. The problem is, it’s not a Tempest filming location: it’s on Oahu, and the Tempest filming locations are all on Lanai and the Big Island.

        So color me stumped here.

        • I am very much amused at how you are running in a completely wrong spatial location with this one.

          “The pipes and drums exiting forever” has a quite literal meaning that is quite closer at hand than the punchbowl.

        • Authors Seat near Firth of Forth? Perhaps Castle Rock, an ancient volcanic plug? A friend of mine sent me a small chunk of basalt from there. 350 Million Years ago it was non unlike the Canary Islands.

  20. I noticed a longterm uptick in tremor registered by the sil stations Grimsfjall, Jokulheimar, Husbondi and Kalfafell. Is that weather related only, or has it the signature of a smaller Jökulhlaup?

  21. Could it be that a new central volcano will develop inside the Campi Flegrei Caldera and slowly fill the whole caldera?

    • Unlikely since there has never been a central volcano to begin with. Large caldera volcanoes work on their own imperative.

      • What’s the reason that there has never developed a central volcano and what are the conditions for developing a large caldera volcano instead of a central one?

        • That is a really good question why large caldera volcano rarely originate out of a central volcano, or has a very diminutive central volcano (like Uturunku).
          But I think it is more of an item for a rather large article than a brief comment in here.

        • To get a large caldera, you need to empty a large magma chamber. A large magma chamber will push up the ground over a large area, so you get a plateau rather than a mountain (e.g. Yellowstone). In general, the caldera will be smaller than the volcano that caused it. Tambora was a huge volcano and the largest eruption over 500 years, but it is still a caldera on top of a mountain.

  22. 1: Quadrant Peak on Vindication Island?

    It is certainly draconian, it looks like both a rhombus and the rhomboid muscle in your neck, and it is mostly ice free considering its location.

    Only thing I have not found yet is a whaling station there – but there were several of them close by (Candlemass, South Georgia, etc.)


        • If you had found a reference to Macbeth and Pipes end drums exiting you would have gotten one 🙂

          • Macbeth for number 1? Am I reading these wrong?

            Is it 5 clues for one thing or 1 clue for 5 separate things?

          • No, it is me being confused.
            Macbeth is obviously for number 2.

            “Wild Rhomboid Whale (Draconian green coated whaling station in island nation)” and every single word is a clue as it is, and every word together is also a clue. The volcano in question has a relation to all those words 🙂

  23. A big thank you to Carl , Albert, and to everyone who contributes to this site. For me this is armchair travel to wild and wonderful places while we wait for a teleportation device. I’ve been lurking for a while, but this quiz has prompted me to have a go.

    1. Deception Island – discovered by whalers in 1820. Eruptions in the late 60’s lead to an evacuation of the British and Chilean research bases.

    The photo I found looks like a humpback whale with snow on it Wild Rhomboid whale.


    Deception Island is famous for its flora – including Schistidium Deceptionense. Mosses are often green.


    There are draconian rules in place for visitors – an Antarctic Specially Protected Area.

    Whether I get a ding or an NNEC, I’ve learnt about mosses, lichen and liverworts!

    Our spam deamon decided this needed approval from and admin, as often happens with first comments. Future comments should appear instantly – admin

  24. Picture riddle. (far out guess) Qualibou on St. Lucia. The man in the first pic is a Briton-Piton, the castle shows a drive in, and the Sulphur springs is the only drive in volcano in the world.

    • Yes, Spike is free of the Dungeon Troll and our cookies are safe 🙂

      But, alas… No… I am surprised that people are so far off. 🙂

  25. Let’s try another angle. What if pig is an acronym? What could it mean? Well, one interesting meaning is Plume-In-Grid. A method to model pollution. Made me think of a certain Icelandic volcano. Did some googling and found that John Cleese did pay £3300 to travel from Oslo to Brussels by taxi when the planes were grounded because of a certain ash cloud. The reference to Faulty Towers and Monty Python is obvious, so clearly the answer to number 4 is Eyjafjallajökull.

  26. #1 has to be Rusheen Island, in the Inishkea Islands, Ireland.

    It is Rhomboid, covered in machair (green), wild (no inhabitants), and was home to a Norwegian whaling station in the early 20th century. Draconian because, well, because it is Irish.

    Come on….if wrong, a bonus point at least!!! LOL

  27. 2: Laki? Laki is an Indonesian folk band, Laki was known as the entrance to Hell (the pipes) and Hecate in MacBeth was from the Underworld and was preceded by *THUNDER* (drums), was responsible for the bright red sunsets featured heavily in period art.

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