The Urban Volcano

Guest post from Tallis

If you were to ask a volcano enthusiast “What is the most dangerous volcano on the planet?” you’d get a range of answers. From a novice, Yellowstone, from someone who only knows of American calderas, the Long Valley caldera. The generic but not wrong, Vesuvius, Mt Rainier, Campi flegrei, Paektu, Santorini, Nevado del Ruiz, and more. Many candidates for this title exist to the point where I believe unless either of these volcanoes is actually likely to produce a major eruption soon, no one can truly say conclusively what is the most dangerous volcano.

I am sure all of us have our personal picks backed by facts and reasonable propositions and I am sure we all have that one volcano that we wished was more studied by the scientific community and had plenty of data to pick apart and analyze. I am letting Chiles-Cerro Negro go so don’t worry it is not the subject of this article. I have passed over another volcano that has been restless as of late and has a large magma chamber. In hindsight, I should have done this article a long time ago.

I am sure a decent bunch of us are anticipating the next volcanic catastrophe; while there is no guarantee, it is possible that we could see large sulfate expelling eruption in the near future. Statistically, it is not very unlikely nor would it come as a big surprise.

Humans have suffered the power of volcanoes since our emergence into the world,  It is unfortunate that many people do not respect the power of a volcano. People don’t truly understand a true volcanic catastrophe, No man-made weapon has ever matched even the modest VEI 6  let alone VEI 7 or 8. No densely populated area has been threatened by a VEI 7 and we have never seen a massive caldera-forming eruption with our modern technology.

 We would like to believe once the signs that it could happen appear, people would spring into action and the government with civilians would prepare to the best of their ability. As much as I would like to believe that, history has shown us that this is not always true. Not just with volcanoes but with Tornadoes and Pandemics   Even when the writing is on the wall, a lot of people won’t respect disaster until it affects them and by then it is too late to prepare.

The volcanic event that we are anticipating will not be respected by everyone and depending on how it goes, it might not be prepared for. There are a significant amount of volcanoes that threaten millions of people and are monitored closely. An argument could be made that the volcanoes of East Africa, the Philippines, Japan, Central, and South america, the Mediterranean, or Indonesia are the most dangerous as there are a great deal of volcanoes in those areas that threaten large urban areas. But in my opinion, what I believe to be the most dangerous volcano in the world is the Tatun Volcanic Group.

I have only given this volcano the briefest of introductions in one of my first articles, I will give a more deserving introduction into this volcano here.

The Background

Located in the northwestern part of the densely populated island of Taiwan, the volcano looks unimpressive compared to others. After all, it is ‘just’ a group of lava domes, Tuff rings, and cones. Barring a small eruption in 2014, it hasn’t erupted in over 1300 years. It’s first eruptions can be traced back 2.8- 2.5 MA ago. The second period began 1.3 Ma ago and ended 100,000 years ago. Most of the domes and rings were constructed  0.4–0.8 Ma ago. There have been some eruptions confirmed by the GVP to have happened 648 CE and 4095 BC but the scientific papers I have looked at don’t mention those.

The domes are dominantly Andesite and Basaltic Andesite, with some pure Basalt as well. The group consists of 20 major domes and cones. It was mostly built by effusive eruptions and there has only been one Plinian eruption known to have happened at this complex. Most of the pyroclastic material has been produced by Vulcanian and Pelean eruptions.

The geological setup that has produced this volcano is complex and has not been settled, it has access to very deep and volatile magma and an extensive plumbing system consisting of a magma chamber and a large hydrothermal system. It is on the Western edge on the subduction zone as the Philippine plate goes under the Eurasian plate.

However the subducted area is deeper than the usual 100 km.  This volcano has been associated with the volcanic arc related with this subduction zone but isotope analysis has shown that it has no arc signature but the magma is like that of continental rift but there is no rift here. It has been propositioned that this volcano is fed by a lateral leak of the mantle fluid from the Philippine plate but this hasn’t been confirmed.

Despite a surplus of signs such as hot spring, fumaroles, sulfate deposits, uplift, and seismic activity. There are still some who would consider this system extinct but this system is almost definitely active. The hydrothermal system is large and it’s chamber lies 0.5-2.5 km below the surface. It has been shown that this chamber is being currently supplied with material from the mantle, however, if this volcano is regularly fed by fluid from the mantle this might not be an anomaly but the norm.

One important portion of this volcano has not been well studied and that would be regional tectonics. Unfortunately, I could not find a great deal information on regional faults at all and the state of regional faults would play a valuable role in understanding the volcano’s unrest. Not only in the sense of caldera-forming events or even regular eruptions but also the state of the hydrothermal system. Even if this volcano were not to produce any type of eruption, the unrest could produce a shallow magnitude 6+earthquake in a densely populated region.

The volcano’s magma chamber is massive, more massive than most people would think. In 2017, an extensive study was done to find the size of the magma chamber, and while it didn’t give an exact number, it gave us a rough estimation. Dr Lin, one of the researchers conducting the study, estimated that the area of the chamber was ¼ the size of New Taipei city with a depth of 4 to 10 km. I don’t know if he means a quarter of the city proper or municipality but calculating the volume of all the known potential variables yields 1,140 km3  2,052 km3 2,850 km3 and finally 5,130 km3, a HUGE spread in numbers

That’s what he gave in a Taiwannews article but his Study gives something different. In his study he estimates, if the chamber is 40% molten the volume would be 350 km3, and if the chamber is 14% molten, it’s volume could be 936 km3. Not as massive as what I calculated using the information in the article. Both sources state that another study shall be made soon so you will have until for a more precise figure. This mystery is, in my opinion, without a doubt one of the greatest and most interesting in this field. My anticipation is almost pouring out of my mouth.

Thankfully you won’t have to wait too long as that study was released a few months ago and has given the chamber up to 504 km3 of melt which would be 16.5% of the total chamber. Giving the chamber a total volume of 3,048 cubic km. While this figure is not super concrete it is much better than whatever was going on above. It should be known that this figure is the maximum volume based on the information based on the study but this still shows a lot of magma lies beneath this system; enough to trigger a high-end VEI 7 or even a low-end VEI 8. Whether the volcano could actually produce a caldera-forming eruption in the near future is a different issue.

The Threat

So many people live close to this volcano, more than a million people are less than 5 km away from this volcano and almost 10,000,000 live within 100 km of this system. Even a more modest eruption could threaten a quarter of the entire country’s population.

This volcano is dangerous and I am sure no one would object to that statement, this background hosts a laundry list of threats. All of which I will break down now but the geological setup, as well as the plumbing to the system, are not clearly defined or even understood. This complex produces almost every type of eruption known, various types of lava flows, Vulcanian eruptions, Pelean eruptions, Plinian eruptions, submarine eruptions, and probably has the potential to produce a caldera-forming eruption.

The most likely event to take place in this system is a small hydrothermal explosion or phreatic eruption, in fact, this has already happened. This volcano had a small phreatic eruption in 2014 that was only recognized after an analysis of seismic data. Even a small eruption or explosion like this could kill people. The death toll likely wouldn’t surpass 50 and it would definitely not be a regional or global catastrophe but that doesn’t matter. An eruption like this would be almost unpredictable and could realistically happen at any time but it would have to take place in a specific place in order to be deadly. There is nothing much to this eruption and there is nothing much to be done to prepare for this.

A deadlier and still reasonably likely event would be a large hydrothermal explosion, phreatic eruption, or small Vulcanian eruption akin to the recent eruption of White Island.

Whakaari / White Island eruption: Tourists share video of eruption …

 This and the previous style of eruption would only be deadly if it were to hit a populated area within the complex proper and be limited to local impacts. This should not be a huge issue for this volcano.

Fortunately and unfortunately, There would be some warning but that warning may not be enough to generate the appropriate response. There was a decent bit of seismic activity that took place at White Island before it’s eruption along with other signs but the restlessness was par for the course for a volcano like this. The government and tourist agency didn’t stop it’s routine and 21 lives were lost.

This situation was an avoidable tragedy and will not be the last of its kind. A situation similar to this could happen at Tatun. This volcano is constantly restless and has people still questioning whether it is alive or not when it is almost definitely alive and kicking. If this eruption were to happen within the city proper, only the best monitoring and planning would evade death, a difficult feat even for the best.

One way that can give more data and some insight into this possibility is to study the plumbing and dynamics of the hydrothermal chamber. A potentially important part of this would be the aforementioned regional tectonics. The hydrothermal chamber is often mentioned as a side note to the magma chamber, and generally only receives modest attention as it doesn’t threaten a large number of people. This is not the case here, not only is this hydrothermal system large, it might have highly volatile material from the mantle.

A Vulcanian eruption would produce similar issues. The predictability would probably go up as the eruption would get larger, however, this doesn’t have to be the case. This volcano doesn’t have what would call a well-grasped history and it’s existence seems to be special. It’s magmatic eruptions could be very predictable or very unpredictable. But after 1 deadly explosion, there would be mass evacuations and prep almost immediately after. These eruptions wouldn’t be extremely dangerous for normal volcanoes but this isn’t a normal volcano. The inherent difficulty of giving an accurate volcanic forecast is maximized with the nature of these eruptions. They would not be extremely deadly like Nevado del Ruiz or Pelee but relative to their size they could be some of the costliest and deadliest eruptions of their kind.

Lava flows have taken place from this system, and they have been relatively voluminous. The average effusive lava eruption would release 0.1 to 0.6 km3 of magma. It wouldn’t be very deadly due to the amazingly slow speed of the flow and it would most likely be more intermediate then mafic. However, it is possible that this volcano, tapping into its rich and volatile magma, could produce a lava eruption on the scale of the recent eruption from Hawaii. The chamber has the volume but does it have the high-quality magma?

According to the aforementioned recent chamber study, 2.2% of the magma is basaltic while the rest is intermediate. That is 60 km3 of available basaltic melt, not only that but an intrusion would likely add to the available magma. Lava flows are common at this volcano but nothing on this scale has been confirmed. It seems to be a possibility and it would be a sight to see an eruption like that at a volcano like this. Even with this volcano, an eruption like this would not be very deadly and it would be one of the best-case scenarios.

Lava dome construction and destruction is very common at this complex which would lead to Pelean eruptions and voluminous pyroclastic flows. These eruptions usually contain 0.4-0.8 km3 of material but eruptions could be smaller or bigger. There is no complexity to this process, it’s simple enough, the lava dome is built, the lava dome collapses, a pyroclastic flow. The eruption’s death toll would depend on preparations and the size of the eruption.

A quick collapse of a small lava dome would not be very deadly with the right preparations. However with the small size stature of the dome could lead to the underestimation of the situation resulting in death. A major disruption to an economically vital city for a benign-looking eruption may not be something the government would be willing to risk.

Another scenario with even more foreboding potential would be a long multi-year construction of a dome. Only after several years after it’s birth would it collapse. One of the deadliest parts of this type of eruption is the fact that no one would know when the dome will collapse. If the collapse happens quickly then the adequate preparations might not be made and if it takes place after a long time then preparations would be relaxed.

A pyroclastic flow from a large Pelean eruption could travel over 15 km and destroy all life within its path. If this situation were to be poorly prepared for, tens of thousands or maybe even hundreds of thousands will die.

The final and most destructive eruption that could take place would be a Plinian eruption without any doubt. This system has produced large VEI 4 Plinian eruptions in the past and if this were to happen, the preceding eruptions would give ample warning, and the most likely cause for death would be from the ashfall. There hasn’t been any VEI 6+ eruptions confirmed to have happened in this complex but it’s not impossible for it to happen now.
This system has more than enough volume to produce a large caldera-forming eruption but does it have the quality magma? Well since Masaya produced a caldera-forming eruption with mafic magma, I’d say maybe. That doesn’t mean that it is likely per se. The Intermediate magma is partly a result of the very hot magma melting the rocks surrounding the magma chamber. It is possible that some silicic magma could get in the chamber but not a large volume at the current period so I don’t really think that should be the dominant concern. It is possible though.  It is actually amazing that this volcano’s products can remain so youthful despite this volcano being around 3 million years old.  There is no point in discussing the effects of a large VEI 7+ eruption as it would cripple the entire country and lead to a Hollywood-esque disaster with horrific destruction and death.


The Present

Such a wide range of possibilities from an incredible effusive eruption to a devastating explosive eruption, the current situation should speak to which one seems likely. Unfortunately, there is no public data for this system, but according to most studies on Tatun, the current activity points to a hydrothermal origin. Some material from the Magma chamber is entering the hydrothermal system but that doesn’t mean that the magma chamber itself is under intrusion and the deformation in the area has been associated with the hydrothermal system.

In such a large complex, any eruption could happen anywhere but it wouldn’t happen everywhere.

 A volcanic vent has formed at this volcano giving a surplus of evidence of life at this volcano. The vent extends down 2 km, exactly where the hydrothermal chamber would be. There is no definite proof of magma intrusion but a surplus of hydrothermal activity. At this point, a magmatic eruption doesn’t seem likely but a hydrothermal explosion can be just as deadly.

Currently, an alert system is being created by the government of Taiwan, as thanks to Dr Lin’s extensive studies on this volcano leaves little doubt to its potential.

This is an interesting volcano, to say the least, but what makes it the most dangerous? In my opinion, the volcano doesn’t have to produce a large Plinian or Pelean eruption to be deadly all it takes is a tiny, poorly placed phreatic eruption to cause fatalities. There is no shortage of people living in the volcano. A seismic crisis on par with Mt Agung recently could cause panic and lead to significant economic disruption to the city.

Just on it’s on it is already dangerous but another variable that makes this volcano even more threatening. There are not one but two nuclear power plants near the volcano. Needless to say a volcanic Fukushima, Chernobyl, or worse would be absolutely horrible but it is possible here. I don’t know much about nuclear meltdowns so I’ll save that issue for later.

Tatun volcano group has been seen as dead for years but it’s more alive and expansive than most volcanoes. Regardless if you agree with my opinion on this volcano, scientists and government officials should no longer consider this volcano extinct and take it just as seriously as Campi Flegrei or any other widely known dangerous volcano. (And give me us some public data)


2020 paper on Tatun

116 thoughts on “The Urban Volcano

    • Thank you. I first found about this volcano just reading an article on and thought “Hey that’s kinda interesting but it seems a little boring.”

  1. I have heard of Tatun volcano but didnt realise there was so much magma there, I thought it was a field of lava domes that was infrequently active but this seems to be the real deal and a big find at being so recently active and even right now. I think if most past eruptions were effusive andesite flows then that is probably what will happen next time, not that that is a great option exactly in such a populated area and with possibility of pyroclastic flows in steep areas. I guess maybe something a bit like Colima or Reventador, long duration andesite flows sometimes explosive activity, not viscous enough for true dome growth, both those volcanoes I think are probably in that volume range by now in recent activity. Its lucky the Tatun system seems not evolved enough for anything massive yet.

    • I wonder what type of monster this volcano will be in the distant future but something on the smaller scale seems way more likely right now.
      This could be the scene for a possible VEI 8 in 525,020 AD so call your descendants.

    • Well it is probably close enough to the ocean for that to be a concern, so you get Krakatoa on steroids 🙂 I dont know what will still be around then or evolve by thay time, the first million years after the K/Pg extinction saw a lot of really weird animals evolve very fast alongside some things that took the extinction like a champ, so maybe Tatun will do its VEI 7 to the spectacle of a bunch of very strange creatures. I personally like the idea of water monitors or sea snakes evolving into mosasaurs again, but that probably wont happen in only 1 million years, or at all if orcas still exist then. I guess for that to happen we probably have to go extinct on Earth though so we wont ever know 🙁

    • To be honest I would not be remotely surprised to find bacteria able to thrive in this environment. The atmosphere is incredibly dense and well supplied with sunlight and CO2 and as on earth the limiting atoms are probably nitrogen and phosphorus. We do ourselves a disservice to believe that life can only follow the water-based terrestrial blueprint because evolution makes no such distinction. IMHO all that is required are reasonable temperatures (say 0C to 300C) a supply of energy and a set of building blocks and a LOT of time.
      Also note that once you consider the greenhouse effect, and the size atmospheres can get to, the planetary ‘habitable zone’ is rather large. Note that if mars was a few times the mass of the earth with a thick CO2 atmosphere it would be very habitable. Earth is probably unusual for a planet of our mass and position in having a very thin atmosphere, possibly due to loss of volatiles when it collided with its sister.

    • 54 kilometers above
      Venus surface the pressure and temperature are very similar to desert days on Earth. And the CO2 skies are blue.
      Humans may live there in floating blimp cities, but If you falls down from the gondola,
      its very very bad indeed 😆. Venus clouds is told to be very thick, but not opticaly very dense ( great kilometer visibility in the clouds?? )

    • And thats the thing…
      In venus upper troposphere, you do Not need a spacesuit to survive, only oxygen supply and perhaps cooling system, when you go outside. Floating human colonies may float above
      50 kilometers for even more comfortable temperatures. You are also safe from meteors unlike
      the moon and mars, with very thin or no atmospheres .Moon colonies needs to be built underground, to escape the constant mini meteor erosion. Venus will be a weird life, but possible.
      But nothing for those who are afraid of heights.

      • As usual SF got there first; Lando Calrissian where are you when we need you?

    • The microbes will be hiding inside droplets of sulfur – acid dixode and using the minute ammount of water thats present in the atmosphere. Its also possible that the microbes are based on sulfur – carbon and use liquid sulfur dixode + carbon compunds to run their metabolisms. But Im no chemist.
      They must be small enough to float in the CO2 air too.

  2. Laacher See Volcano in my neighbour’s backyard is very dangerous too due to its proximity to cities like Koblenz, Bonn, Cologne, Frankfurt, Mainz and the Ruhr District. In case of any eruption Koblenz can be threatened by pyroclastic flows from the Laacher Volcano, Frankfurt, Mainz, Bonn, Cologne and the Ruhr District by ash fallout.

  3. Great article. Not sure that we can claim that VEI7s have not threatened heavily populated areas; they tend to have a global impact.

    Homo sapiens arrived in Eurasia between 125,000 and 60,000 years ago and the Americas 15,000 years ago (Source Wikipedia) It is possible that they witnessed some of the following VEI7s: Phlegraean Fields 37,000 BC; Aria Caldera 22,000 BC; Mount Mazama 5,700 BC; Kikai Caldera 4,300 BC; Thera 1620 BC; Baekdu 946; Samalas 1257; Tambora 1815. They might have missed Taupo 180 as they arrived in New Zealand later. Before the VEI7s, there might have been some desirable real estate near the volcanoes or within reach of the ash etc..

    • True. Global impact threaten more people but I am talking about the direct major impacts affecting large population center whose size are akin to the modern metropolitan areas.

      • There may not have been large conurbations near the volcanoes but there may have been an equivalent population within the damage zones – e.g. the Eastern Mediterranean had tsunamis from the Thera eruption and the Minoans took a hit.

    • It is beyond possible, it is archaeologically proven that all of these eruptions except Taupo were witnessed by our species, Mazama actually still lingers on in a legend from that area I believe, obviously after 8000 years or so it has warped a bit but still, its a record 🙂 Kikai must have been terrifying, a moving mega mountain of glowing ash billowing over the ocean from beyond the horizon to wipe out half of Kyushu, and this was not in some primeval past, this was 1000 years after we discovered how to write, we had metal tools, cities, advanced (for the time) technology, civilisation, agriculture, all in all not so different to today… We talk about how huge Hawaii and Iceland are, but Kikai was 2000 years worth of eruptions in Hawaii in one go, sure it wont repeat for many tens of millennia but this was a thing that really happened and so recently nonetheless.

      Actually, while genetics has long suspected our species evolved a very long time ago at the same time as Neanderthals (half a million years ago), recent fossils have extended our range back to at least 330,000 years ago, and over at least the entirety of Africa even back then. This means that our species both saw and survived the probable VEI 8 eruption of the O’a caldera in Ethiopia 240,000 years ago long before we sat through Toba and striking right at our origin. In addition to that we probably also bore witness to the formation of all of the currently active volcanoes on the east africa rift zone including what appear to be a number of flood basalts, large scale VEI 7s, and apparently also equally huge lava floods of more evolved composition, some really serious scale volcanism. We also probably witnessed a few of the major eruptions in the Tibesi Mountains, like the VEI 6 eruption of Era Kohor crater 116,000 years ago, and the much more recent (still ongoing?) formation of Tarso Tousside in the Holocene. We are a creature of the volcanic environment, even today, we are drawn to them like moths to a flame even though we know the risk.

      • Very good points. Would be interesting to see a full post on this subject!!

        • I agree, some of those locations are unfamiliar to me, going to have to spend some time on wiki…

  4. Thanks Tallis! yes I never knew there was souch large ammounts of melt there.
    But the magma body coud be a mushy sponge like zone rather than a true liquid.
    Most magma chambers are mushy and perhaps only quite molten at the top.
    Not at all like the childerns version of a volcano. Mush Zone perhaps with a jucey top?
    How this voclano in the article looks like at depth, is likley very complicated

    The only volcanoes that are like kids versions are open lava lake volcanoes, they are very molten and open inside.

    • Yes thats true very few volcanoes are really liquid and open inside.
      The laka lake volcanoes are in that very rare class of open nearly completely molten systems.
      Nyiragongo, Kilauea, Masaya, Michael, Erta Ale, Villaricca, Yasur, Stromboli Shishaldin,
      and perhaps Etna and Grimsvötn and Galapagos are in this rare class. Open and molten plumbing systems all through. These volcanoes erupt very often or constantly, and highly active volcanoes can shift into this style off activity. Relativly simple open plumbing systems, with open conduits.

      Most basaltic volcanoes and even sillic volcanoes are like this
      Axial Seamount is a “decompressing melt lens” with minerals that are melting and an upper region of more and more molten matter. At upper parts there is a relativly more melt. The upper melt region feeds dykes and sills and often central magma chamber with basaltic or sometimes more evolved melt. The systems can have many magma chambers and dykes and sills.
      These systems are typical of Katla, Askja, Bardarbunga, Medecine Lake, most volcanoes in african rift and many other volcanoes.

      Volcanoes and magma systems are incredibley complex, some magma systems are simply a chaos of sills and laccholiths, dykes that forms no central structure. Sillic volcanoes and sillica rich centers are also complicated as heck, with slow supply of basaltic magmas( many injections episodicaly ) feeding more evolved sillica rich resovairs, that can grow into a very large size. Volcanologists still dont know exatcly how the giant sillica rich resovairs, of VEI 8 tephra eruptions form. It involves a slow evolving supply of more mafic melt, that keeps a large batch of sillica rich magma eruptible.
      How large sillic calderas looks like on the inside is very complicated.

    • Magma systems are so complex that even relativly open and simple systems,like Etna and Stromboli haves many graphs and many interpretations of how they looks like.
      So complex that, Im happy to not work with this in imaging and translating data to graphics.
      Just look in old mountain walls and you can see a chaos of sills and dykes

    • These are great! thanks alot some of these cones are indeed very young looking

  5. More about the Volcanic Eifel District in Germany:

    * “Geodetic evidence for a buoyant mantle plume beneath the Eifel volcanic area, NW Europe”;
    * “New hints of volcanism under the heart of northern Europe”;
    * “Deep low-frequency earthquakes reveal ongoing magmatic recharge beneath Laacher See Volcano (Eifel, Germany)”.

    • I’m not convinced Eifel is a plume, there seems to be a trail of volcanic activity extending northwards from the alpine orogeny especially in central france and right through western germany, the most recent of which was at Laacher See.

      I think any further north and these zones of weakness the magma is seeping through hit the baltic shield and can’t penetrate, but I imagine upon the initial african/eurasian plate impact and the continued collision has created lines of cracks in the crust further north much like when your windscreen gets hit by a stone on the road. Could be that magma is pooling there because it can’t go any further.

      If it is a plume then you’d have to describe the massif central as a minor plume too?
      There’s also a smattering of volcanics in spain, switzerland, poland etc.

      • It is caused by a bit of rotation of western Europe, caused by the Italy collision. This has caused a line of extension running across Europe into Spain. The volcanic activity is mainly along this line. The extension itself can help pull up some hotter magma.

        • Was the Adriatic microplate always separate from Eurasia or has it been partially severed? Seems that the Eurasian plate is a big meld of old plates with old ‘boundaries’ like the Pyrenees and the Urals.
          I’m also curious about the Aegean & Anatolian plates and the odd tectonics around the Black Sea.

        • Apologies, Switzerland apparently does not, although Romania has a few sizeable ones. I wonder if those Netherlands volcanoes were related to the North Atlantic Igneous Province? Those dike swarms travelled thousands of miles, right out to the farne islands in the north sea at least.

  6. Some larger quakes at the Husavik Flatey transform Fault today.

    15.09.2020 17:06:45 66.123 -17.729 11.6 km 4.0 99.0 6.9 km SE of Flatey
    15.09.2020 14:52:11 66.127 -17.723 11.3 km 4.6 99.0 6.8 km SE of Flatey

  7. I know that the VEI scale is magnitudal, going up by factors of 10, but I think there is way too much variation in what constitutes a VEI 7. A 7 at the lower end can simply be a very big normal eruption, Tambora is still a mountain today and mostly intact. A high end VEI 7 is basically just a VEI 8 that stopped a bit short of that 4 digit threshold really. Long Valley is rated the same VEI as Tambora but whatever was there before was utterly destroyed by an eruption at least 7 times larger than Tambora. The same can be said of Kikai, almost as large as Long Valley and as I said on the other comment that was within our civilisation epoch. Kikai was also just as big as the Henry Fork caldera at Yellowstone which is by contrast usually termed as an actual supervolcano because of its location…

    I think there needs to be a VEI 7.5, there is clearly a fundamental difference between these borderline VEI 8s and something like Tambora.

    I guess if you make the E in VEI stand for effusive instead of explosive you can measure lava flows fairly too, and in this case there is also an obvious point where a VEI 7 can be both a bigger 6 or an 8 that didnt quite make it, a 900 km3 flow is very different from a 110 km3 flow, one is about 10 lakis and has probably happened in the Holocene somewhere, the other is about 60 and probably needs a deccan traps level event to happen… that 900 km3 flow however is only 10% smaller than a VEI 8 flow, there is clearly not a hard line.

    • The VEI scale is defined in several different ways. Based on the volume, it is quoted to two digits, e.g. VEI 6.9 It is difficult to measure the volume that accurate though.

      • I understand, but it still seems strange to lump such a range because of a number. It is not to say Tambora wasnt enormous, but it really doesnt hold a candle to something like Long Valley or Kikai, 500-800 km3 in one go. The scale works up to VEI 6 but for 7 it needs to be shorter intervals than just being 100 km3-1000 km3, otherwise you get an eruption of 990 km3 being directly compared to an eruption 1000% smaller rather than 1% larger because that 1% is just over the line into the next level up. I guess maybe just expanding ‘supervolcano’ to all eruptions that destroy their edifice entirely is an easier move.

  8. I was trying to think what the most dangerous Volcano would be – my first thoughts outside the standard ‘actual destruction’ idea and the ‘global winter’ idea – were ‘are there any volcanoes that could accidentally start a nuclear war, or which would cut off a huge chunk of oil supplies (which might not be bad in terms of environment – but worst case scenario the instability might instigate a war) – or which might ruin the water supply to a really large area (resulting in crop failures – the global rice/corn/wheat harvest?, and thus produce lots of refugees – and resulting instability) – I think the water table in the central US states is all aquifer related ? – quick google gave the name Ogallala Aquifer – so a volcano that could poison the Ogallala Aquifer, I’m guessing that would have as big an impact as the dust bowl. I don’t know if there are any ‘active’ volcano candidates there (or worse spots to have eruptions?) ?

    ps.FAO dragons – ongoing issue (a month or longer) if you have a wordpress profile and then try clicking ‘change’ and connecting to facebook – it still gets stuck ‘connecting’ and you have to cancel out of the post, so I think anyone trying to post via facebook logins will be having problems

  9. Thanks for the post Tallis. Personally, if I were gauging the “danger” of a volcano, I think you have to account for the likelihood of an eruption to actually occur as well as the likelihood of an eruption to be large enough to cause harm.

    I wrote a long post and series on my own website (now defunct) trying to put together a “most dangerous volcanoes” list based on some rough estimates of:

    – Nearby population
    – Eruption probability in next 100 years (this is the most difficult thing to gauge)
    – Potential magnitude of said eruption if it were to occur

    The second two items are particularly hard to gauge due to the fact that volcanoes are not predictable and they are often prone to doing things we don’t expect. But with that said, some volcanoes have a long history, and also have a tendency to behave in at least a somewhat similar way.

    On that note – I strongly believe the most dangerous volcano in the world that is not really discussed much at all is Apoyeque. This was of course mentioned in the Volcanocafe decade volcano list at #2 (appropriately)

    It checks off just about all the boxes you would look for in a potential disaster.

    1. History of recurring large eruptions (including a significant repose between the last large eruption)

    2. Water nearby, increasing potential dangers via tsunamis (on lake managua), extended base surges, and potentially increased explosivity.

    3. Large nearby population center of over 2 million people (Managua city + surrounding regions)

    4. Other large caldera centers nestled in the region, suggesting the propensity for this to go even bigger.

    • FWIW, sharing that list I created based on the above logic. Keep in mind that this ignores the super important second-order effects volcanoes may have on the climate since that is simply too difficult to predict or understand the impacts of. Laki was supposedly one of the deadliest eruptions ever, but only because of how it influenced climate, thus inducing famine and disease to spread in Europe.

      Tier 1 Volcanoes – These volcanoes are the true ticking time bombs, where you know there will eventually be a major disaster, but you just can’t predict precisely when that disaster will occur.

      Campi Flegrei – Italy
      Taal – Phillippines (Luzon)
      Mayon – Phillippines (Luzon)
      Aira – Japan (Ryukyu Islands and Kyushu)
      Apoyeque – Nicaragua

      Tier 2 Volcanoes – Tier 2 is reserved for volcanoes that still have a ton of potential to form a megadisaster, but the odds of that happening in the future is significantly lower.

      Ata – Japan – Kyushu
      Tolima, Nevado del – Colombia
      Guagua Pichincha – Ecuador
      Pululagua – Ecuador
      Cotopaxi – Ecuador
      San Salvador – El Salvador
      Agua – Guatemala
      Almolonga – Guatemala
      Vesuvius – Italy
      Merapi – Indonesia – Java
      Amatitlan – Guatemala
      Guntur – Indonesia – Java
      Tacana – Mexico
      Rainier – USA (Cascades)
      Tatun Group – Taiwan
      El Misti – Peru

      Tier 3 Volcanoes – Tier 3 is more of a watch list of volcanoes that have a large population nearby and a lot of uncertainty around them. These volcanoes can all turn into major potential disasters, but there are a lot of elements that cast doubt as to whether that type of scenario would unfold.

      Baker – USA (Cascades)
      Tenerife – Canary Islands
      Galeras – Colombia
      Chimborazo – Ecuador
      Cayambe – Ecuador
      Izalco + santa ana – El Salvador and Honduras
      Santa Ana + santa ana – El Salvador and Honduras
      Shikotsu – Japan – Hokkaido
      Fujisan – Japan – Honshu
      Nantai – Japan – Honshu
      Cereme – Indonesia – Java
      Merbabu – Indonesia – Java
      Slamet – Indonesia – Java
      Agung – Indonesia (Lesser Sunda Islands)
      Malinche, La – Mexico
      Colima – Mexico
      Mt. Unzen – Japan (Kyushu)
      Soufriere Guadeloupe – Guadeloupe

      Tier 4 Volcanoes – Tier 4 includes volcanoes that you can see a possibility for a large scale disaster, but the likelihood of that arriving isn’t all that high in the geologically near future.

      Aso – Japan (Kyushu)
      Hakone – Japan – Honshu
      Galunggung – Indonesia – Java
      Raung – Indonesia – Java
      Avachinsky – Russia – Kamchatka Peninsula
      Koryaksky – Russia – Kamchatka Peninsula
      Matutum – Phillippines – Mindanao
      Cameroon – Africa (western)
      Madeira – Portugal – Azores
      Agua de Pau – Portugal – Azores
      Sete Cidades – Portugal – Azores
      Ruiz, Nevado del – Colombia
      Hokkaido-Komagatake – Japan – Hokkaido
      Kuttara – Japan – Hokkaido
      Toya – Japan – Hokkaido
      Harunasan – Japan – Honshu
      Akagisan – Japan – Honshu
      Adatarayama – Japan – Honshu
      Myokosan – Japan – Honshu
      Azumayama – Japan – Honshu
      Iwakisan – Japan – Honshu
      Asamayama – Japan – Honshu
      Iwatesan – Japan – Honshu
      Bandaisan – Japan – Honshu
      Niigata-Yakeyama – Japan – Honshu
      Baluran – Indonesia – Java
      Batur – Lesser Sunda Islands
      Buyan-Bratan – Lesser Sunda Islands
      Orizaba, Pico de – Mexico
      Pelee – Martinique – West Indies
      Chiracha – Africa – Rift Valley
      O’a Caldera – Africa – Rift Valley
      Corbetti Caldera – Africa – Rift Valley

      • Most, if not all, of the list have some monitoring in place and are in areas where volcanic hazards are well understood. So while an eruption may be economically very damaging to the area, there should be time to evacuate the areas most at risk.

        • Forgot to say, a useful list; it should be given more prominence.

      • So many options for the title but the question is…Why is Corbetti on tier 4?! It would not be surprising, If it were to erupt soon (relatively speaking) Maybe I’ll write article about that one but I would like more data.

        But i must say that’s an extensive list but arguably the most dangerous volcano is the one which no one thinks is an issue when it really is. Unfortunately those don’t make for good articles! Not a lot of information on unnamed volcano here!

        • Corbetti is not well-researched, and when writing the list 4+ years ago, I did not have enough information to make any real conclusions on it.

          Beyond that, it is not a frequent eruptor from what we currently know. So it’s hard to rank it towards the top when the intervals between eruptions are few and far between. It’s hard to put a volcano that hasn’t erupted in over 10,000 years high on a danger list that utilizes eruption frequency as one of the primary inputs.

        • Well it’d be boring if we knew everything about volcanoes, life needs a little mystery.
          Corbetti has around 0.1 km3 of magma entering it a year which is the largest intrusion i know of currently happening at a caldera.

      • That is one amazing list!

        Is it the complete version of it? I would expect to see volcanoes like Taupo, Okataina, Masaya, Awu, Ambae and others high up the list.

        • Taupo (or really, the taupo volcanic zone) is kind of a wildcard. It probably should be in here somewhere, but I’m not really sure what to add (maybe just the TVZ as a whole).

          Okataina + Taupo have had significant eruptions in the last 3000 years. Taupo itself is not likely to create another VEI-7 eruption within 2000 years of it’s last VEI-7. And anything smaller is not likely to cause major issue since there isn’t that much population nearby.

          The northern part of the TVZ is probably riskier due to closer proximity to Auckland + the fact that this area hasn’t erupted as recently if you ignore Okataina.

          As for Okataina itself, it had a VEI-5 eruption less than 300 years ago. Given, I wouldn’t doubt it could do something similar again even now, but recent large eruptions decrease the likelihood of another large eruption in the somewhat near future.

          • What about the Auckland volcanic field? That seems like a ticking time bomb as it is directly under the city.

            I notice you did not include Tambora or Rinjani, presumably because they had comparatively recent VEI7 eruptions. Rinjani is still (even post disaster) one of the tallest mountains in Indonesia, so to me it hasn’t really gone caldera.

          • Aukland field is dangerous for sure – but it’s a monogenetic field, which lends itself to smaller eruptions. Given, it can create explosive maars in a dense urban area which can be hugely problematic by itself. Probably should be on here somewhere however.

            As for Rinjani, what you’re saying makes no sense. It absolutely, 100% went caldera within the last 1000 years. This is not a debate, and you can just look at the thing and see the gaping caldera it created. The reason it’s still quite tall is that the caldera formation occurred adjacent to the rinjani mountain, and only partially sheared off the edifice of Rinjani itself. The rinjani eruption was actually an eruption of a now defunct volcano called Samalas, but their magmatic systems are the same.

          • Yes, the “Anak Samalas” is called Baru Jari, and it is active.
            Sunda arc volcanoes have multiple magma chambers. Will try to find the paper. Just because it blew out one magma supply, doesn’t mean there aren’t more down a bit lower.

            It is 3726 meters, second highest mountain in Indonesia (according to Wikipedia)

          • It is just our association with the idea of ‘it happened here once so it can happen again’ that makes us see risk, in reality this is nearly exact opposite for a VEI 7. VEI 7s destroy a volcano so thoroughly it starts again from scratch.

        • Virunga Volcanoes are dangerous too, despite being almost completely effusive.
          But we disscused them before. I think 3 million? persons live in close proximity to two highly active volcanoes. Goma is turning into a dangerous city, larger than some european cities. Just 10 kilometers away from it are two extremely active volcanoes, infact Goma is built directly on a volcanic field. Lavas from both Nyiragongo and Nyiramuragira can easly reach into Goma. The city itself haves many cinder cones and tuff cones, so eruptions in middle of the megacity is a possibility. The 2011 event, coud easly happen in middle of Goma. Goma is built in a very uncertain place for the far future, its dangerous. Even a small eruption in the streets woud cause huge mayhem. The Lake Kivu is also dangerous with as much as 300 km3 of CO2 avaible in the deeper lake waters. Its a potential gas bomb if its disturbed. Goma is growing rapidly and almost out of controll.
          Nyiragongo and Nyiramuragira coud be the most problematic effusive volcanoes?
          But the volcanoes and gorillas also makes alot of tourists, and income.
          Million inhabitants of Goma and Gisenyi (Rwanda) continue to live with the threat of new lava flows and other eruptive hazards as well as political instability.
          An eruption in the lake floor woud be a risky thing.. Lake Kivu is CO2 charged and unstable.

          • Can they install degas-geysers, as done for those two ‘Death in the Night’ lakes in Cameroon ?? Nyos & co…

          • They have already CO2 degassers installed I think.
            But a lakefloor magmatic eruption is this the largest hazard.
            Lake Kivu is perhaps the worlds most dangerous lake

        • Quite impossible to think of the Nyiragongo volcano without considering the social and humanitarian context of the region in which it sits in.
          One of Africas most hazardus regions, with many hazards and problems comming togther to make an uncertain future. The city is toast in the long term, lava flows and gas eruptions. Humaniatrian hazards are making the situation uncertain.
          Volcano – wise its hazardus and threat to material stuff. but on the VEI scale this arera is pretty low on that scale. Not explosive

        • Nyiragongo and Nyiramuragira are one of very few effusive volcanoes thats really problematic, Mauna Loa is also a very large lava hazard for the steep Kona Side and for Hilo even if it moves more slowly there.

          But Goma and Kivu region is my opinion on the most problematic effusive volcanoes, they are not fun at all when they flows in the wrong place or erupts in the lake. Kivu region have lots of volcanic dangers acossiated with volcanic activity. Lava Flows, gas eruptions, acid rain and limmic eruptions.

      • I also find the pair Masaya-Apoyeque as possibly the most dangerous, either those 2 or the pair Vesuvius-Campi Flegrei.

        • That said it is unlikely any of them will do anything big on our lifetimes. Stromboli will probably end up killing more people this century. But if they really go big Napoli or Managua could be flattened.

          • Exactly. You can look through the tier 1-2 lists here and see that 3 of the volcanoes listed had eruptions in the last 5 years. But they were so small that it didn’t make much of a difference.

        • Of those two, easily Managua is in far deeper trouble. For all the probability of destruction there is at least a serious effort to monitor the bay of Naples and which has a proven history, no such thing exists at Managua. I dont expect Masaya to blow up any time soon, I suspect its pre-caldera behaviour was probably not at all like it is now otherwise probably every basaltic shield can randomly go VEI 6 and yet that is not evident. Apoyeque on the other hand is basically a recurring Krakatau… I also dont expect a caldera there as its style seems to not be quite big enough for that but a solid VEI 5 or 6 is likely.

          • Even with all the monitoring Campi Flegrei can still end in disaster, I wouldn’t assume it will givo off clear precursors far ahead. For example when Rabaul erupted big in 1994 it had just 2 or 3 days of precursor.

            I don’t know much about evacuating cities but I doubt it would be easy to realize something is wrong, then communicate to the population and evacuate it in such a short time.Things can also get complicated if large earthquakes happen or deformation cuts roads (in the intrusion stage the caldera floor will start rising like a trapdoor).

            But yes, Managua is possibly in greater danger.

          • Campi Flegrei seems to be heading for a period of eruptions, based on deformation and eruptive history, and Vesuvius is unlikely to be dormant for more than a few centuries. So unlike Managua, it is certain Naples will get threatened not too far ahead.

      • I made a notepad save of this list the last time you posted just to gradually research each one – some very interesting and quite unheard of systems.

        I honestly think the biggest danger comes from a sudden recharge at an already evolved system – think it was Tarawera that had a speedy basalt dike set off a VEI6 (correct me if i’m wrong?) – any old magma chamber with an andesitic mush that gets reheated with fresh salsa!

        Unfortunately this is almost unpredictable and you only get precursors just prior to eruption.

        • Fuji is on here, listed in “tier 3”, although I would probably move it to tier 2 now.

          Rabaul isn’t near large enough population centers to be a major disaster risk.

      • Also missing Krakatau, it kills by having landslides that form tsunamis. It is also pretty close to Jakarta. It will have another landslide at some point. We just don’t know when.

        • Anak Krakarau looked pretty much the same as it does right now in 1960 or about then. So if nothing changes with its magma supply (probably unlikely but its made it this far) landslide #2 in 2080 🙂

        • Krakatau is not nearly close enough to Jakarta to cause any major issues. Even a VEI-7 from Krakatua (extremely unlikely any time soon) would have a difficult time affecting Jakarta.

          And yes, it may have another landslide, but this is not something that would be large enough to cause a significant disaster. Would it be deadly? In all likelihood, yes, but not deadly in the magnitude of hundreds of thousands of lives at risk.

          • I concur. Even the original Krakatau eruption had little impact on Jakarta. The tsunami was confined to the Sunda Strait

          • The original eruption did dump some ash on Jakarta and the ash cloud was large enough to block out the sun completely for a short time. Not seen any record of how much ash actually fell on Jakarta.

      • Nothing from New Zealand about Auckland, built on monogenetic volcanic field ?

        Upside, Kiwis are *not* Neapolitans, so have wary systems & plans prepared. Still, even if every-one gets clear, losing NZ’s biggest city would hurt…

        Back to Taiwan: if that field pops, the Chinese would be *very* willing to lend a hand. Like Hong Kong, they’ve wanted the territory back for a long, long time…

        • Auckland monogentic field is Not famous for any large large productivity.
          In 300 000 years the arera have only produced perhaps 7 km3 of materials of small cinder cones. And most of the historical volume is the large Rangitoto Island eruption. Eruptions are rare and almost always small. The magma is highly alkaline basalt and formed in small ammounts.

          But a monogenetic eruption in the middle of the city is of course an enormous problem when it happens.

        • During the same time Hawaii have produced many many tens of thousands of km3 of materials!
          For comparison in productivity as a volcanic arera.

          But Auckland is indeed a threat to a large city

          • Rangitoto is I think believed now to be quite a bit more than 3 km3 so the total volume is probably at least 10 km3, and it also appears to have been created out of many eruptions since the mid Holocene. I think this has included gaps longer than the current interval too so it is better classified as dormant, and probably there is a good chance the next eruption will be on or near Rangitoto than just randomly located. This is probably the best case scenario obviously, the long term effects would be very much the same as most of the last 50 years in Hawaii but that is manageable.

            For being as accessible as is actually possible for a volcano to be, theres probably a lot we dont know about Auckland volcanic field. It does sound like the field may be transitioning from a wide monogenetic field to a single volcano though, marked by increase in scale of eruptions.

          • The reported volume for Rangitoto is 0.7km3. For the entire Auckland field (including Rangitoto) it is 1.5 km3. It is an effusive field, so volumes are reported in DRE. If you prefer converting it to tephra equivalent, that is around 2km3 and of course Rangitoto never produced that much ejecta volume.

          • Auckland volcanic field is laughable in volcanic productivity!
            But indeed a huge problem If a Basanite cinder cone pops up in the city. That woud be world news totaly! Imagine the chaos and the news.

          • Auckland volcanic field next time.. will be the real life ”volcano 1997” thats Tommy Lee Jones huge cheese fish show. ( unwatchable b film 🤮). But If Auckland erupts it will be the little like that terrible film in real life for soure.
            When Auckland erupts lava coud flow on the streets

  10. The unmonitored volcano that is not considered an active volcano may well be the most dangerous. it would have to be in a seismically active area so any earthquakes in the run up to an eruption would not be unusual. How many of those are around?

  11. RE: The “CBUS List”:
    I’m surprised Laguna del Maule didn’t make any list, nor for that matter, none from Chile? Both the recent Chaiten, and Puyehue-Cordón Caulle (VEI5) eruptions (and to lesser extent Calbuco) had detectable impacts to the Southern Hemisphere climate. Of all the places on earth, considering that almost all of the Chilean west coast has had MAJOR subduction quakes since 1960, I’d think that inland volcanoes are becoming increasingly prone to experience a major/rapid decompression event from all the new material (water rich) that’s been pushed down into the “melt zone”. It’s only logical therefore that the overlying volcanoes, over time, are going to receive an influx of new material from below. While the latency time for new melt to migrate to the surface is uncertain….perhaps many decades (or maybe next week)…. there is little doubt (in my mind) that at least one of Chile’s volcanoes are going to pop a “big one”…most likely sooner than later.

    • His list I think included potential direct danger too, meaning threat to human life, which Laguna del Maule has effectively none being where it is

    • No doubt, Chile has a lot of volcanoes that can go “big”. But the list I provided requires significant population nearby. The risk of direct life loss when very few people live within 100km of a volcanoes is very low, even in the event of a vei 7.

      • A remote VEI 7 would kill by changing the climate. Does his list exclude climate impacts?

        • Yes, because defining climate change from a VEI-7 and quantifying the human impact is extremely difficult. Also, counting on a VEI-7 is not a easy task.

          • IMHO,
            As we’re noting, there are many ways a major eruption can impact/destroy human life. It all depends on the “definition” of what is direct cause and effect. Whether you get fried by a pyroclastic flow or get frozen like a popsicle from the ensuing nuclear winter effects, your dead either way…and it was the direct result of the eruption that caused it. That’s why potential climate effects should be equally considered as a potential “risk” when talking about VEI-6 and above eruptions that could put millions (billions?) in jeopardy….both nearby and afar.
            Regardless, thanks again for the list and the time and effort to do all the research! 🙂
            Much appreciated.

      • Doesn’t that depend on how far tephra goes? It does not take a lot to decimate farmland (only a few inches). And how far volcanic gases and ash go. Laki was only a VEI 4 but caused a lot of damage in Iceland and Europe.

    • Hmmm, a prolonged tremor episode followed by rock fracturing events and increasing background noise. Sure looks like magma’s on the move.

  12. Increased quakes under the summit and on the rift zone since June. Then the recent abrupt halt in DI events in the last 2 weeks coinciding with a flurry of small shallow quakes that are outside the normal calibration but displayed anyway, since about 10 days ago. Now there are visible changes on the cross caldera GPS that unlike some previous events are not correlated with an increase in movement on the south flank. Mauna Loa has also gone mysteriously quiet in that same time frame.

    I think I may be able to say with some degree of confidence that the gates of mordor are about to open 🙂

    • That would be nice, to see an Eruption starting again on Hawai’i

      • Yes its about time, I hope we get a new Pu’u O’o east of the original so you can drive right to it, I will call it Pu’u Nui o Chad 🙂

    • The gates of Mordor begin to open, and Mount Doom prepares to blow its top! Also brings to mind “A Journey to the Center of the Earth”. Wonder what a subterranean explorer would see if they were able to be beneath the summit of Mauna Loa (without being turned into a cinder)?

    • Yes this is looking promising. Chads big hill is go for construction starting October 4 2020. That is its official name on this site if the eruption begins on that date now 🙂

  13. Campi Flegeri is my opinion on the most problematic volcano for now.
    Even a small eruption woud cause alot of distribution!

    • Campi flegrei is definitely up there, I think it has an edge on sillic magma and has a higher chance of producing a caldera forming eruption then Tatun. I think Tatun is more likely to produce hazardous smaller eruptions in the short term. Tatun has a huge chamber, so I think it is reasonable candidate for a VEI 8 in the next 500,000 years or so.

  14. Popocatépetl has 26.5 million people within 100 km of the volcano and 634,054 within 30km. She’s 5,393m high. While she is a frequent erupter with mostly small eruptions, she has done a couple of VEI5s and a few large debris avalanche flows.

    • I thought Popo was a he, not a she. Need to check the mythology.
      Both Indonesians and Native Americans assign gender to volcanoes.

      Rainier is a male, as is Semeru and Agung.
      Krakatau and Batur are females, as is Kilauea and maybe St. Helens.

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