Future calderas

Ilopongo lake. 2000 years ago, this was a mountain

Volcanoes erupt all the time. It may seem a quiet time to us but that is because most eruptions are small and low impact, and stay below the radar. An excellent daily overview can be found on http://lechaudrondevulcain.com/blog-spotlight-two-column/ As I write this, it lists on-going eruptions at Sinabung, Etna, Stromboli, and Sabancaya. Volcanodiscovery also lists Nishinoshima, Suwanosejima, Semeru, and Kerinci as being active. Volcanoes with long-lasting lava lakes may be added to this: Erebus, Nyiragongo, Erta Ale, Masaya, Yasur, Mount Michael. This is a normal level of activity for our planet. Only Sinabung has really made the news in the past few days. It had a decent size explosion with ash falls in local villages and the government recommended that the people should wear masks. (Where have I heard that before?)

Large eruptions are much less frequent. The largest effusive eruptions of the last 20 years have been Holuhraun and Nishinoshima, the first one the largest by eruption rate, the second one (probably) larger by volume. The largest explosive eruption was Puyehue-Cordon Caulle in 2011, a borderline VEI-5. On average, there is one VEI-5 eruption per decade but the last few decades have been below par. Before the 2011 boom, the last such eruption was Mount Hudson in 1991. Admittedly this was less than two months after Pinatubo, so the current lull came after lightning hitting twice within months. Chance is like that. VEI-6 events occur on average once every 40 years or so. In the last 200 years, we have seen Krakatau, Santa Maria, Novarupta, Quizapu, and Pinatubo.

And VEI-7’s are even harder to find. In the last 2000 years, we have suffered Tambora, possibly the 1452 eruption (cautiously attributed to Kuwae), Rinjani, Baekdu, Ilopongo (recently upgraded to VEI-7) and Taupo. VEI-7’s happen about once every 300 to 400 years. Only 8 eruptions are classified as VEI-7 between 2000 and 10000 years ago: either the last millennium has been exceptionally active, or much more likely), we are missing another 20-25 VEI-7 eruptions in the holocene. It is not easy to measure the VEI scale of a prehistoric eruption.

VEI-8 eruptions have been covered elsewhere. They are so rare that we don’t need to worry about them for now, and they also are very different type of eruptions. A VEI-8 is more than just a bigger bang.

Where were those VEI 7’s of the holocene? Two were in Indonesia (the most recent ones, in fact), 1 in New Zealand, 1 in Korea, 1 in Japan, 1 in Europe, 1 in the US, 1 in Central America, 1 in South America – you get the idea: they are fairly equally distributed across the world. The Aleutian arc and Kamchatka are probably the most productive. But with perhaps two-thirds of the missing, it is hard to be sure. Indonesia and PNG may have had far more than they are credited with. The scars even of a VEI-7 can be healed surprisingly quickly.

Looking through the list, it is striking how unfamiliar the names of the VEI-6 and VEI-7 volcanoes are. The list of currently active volcanoes at the start of the post contains many names that readers here will readily recognize. But the largest eruptions have names that you would not expect to see in the daily headlines. Krakatau is of course famous, but that is because of its eruption and the publicity it received. Tambora was bigger and more deadly, but its eruption happened before the era of daily world news and it remains far less well known.

And before their cataclysmic eruption, these mountains were even less known. Krakatau was not recognized as potentially active until the eruption began. Tambora was not even recognized as a volcano until 5 years before its eruption when it first showed some sign of activity. This was in spite of it being one of the tallest mountains in Indonesia – but we do not know the exact height as no one was interested in it at the time! Tambora’s last known eruption before the big one in 1815 is dated to 740AD (+-150 years). Pinatubo was just a hill, until the USGS raised the alarm weeks before the explosion. Santa Maria had been inactive for at least 500 years, i.e. there was no known activity in historic times. The first indication of something building was nine months before the eruption with an earthquake swarm. Novarupta was a flank eruption from Katmai; Katmai had no known eruptions before the big one, and was only known to occasionally ‘smoke’ in the decades before. For older eruptions we lack historical records, but we know that Vesuvius was not known to be volcanic before its VEI-5 eruption (although some writers did suspect it to be): it had been quiet for at least three centuries. Santorini was inhabited before its big event, suggesting it too had been inactive.

The link between explosions and dormancy makes sense from an explosive point of view. Young, fresh magma tends to be effusive. Over time it becomes stale and more explosive. The ash from big volcanic explosions tend to be white from silicates, while the lava from effusive eruptions tends to be black. Magma turns white with age. A slow cooling by a magma chamber is a danger. Like the Beirut explosive, the substance of volcanoes becomes more explosive as it ages.

In some cases, there may have been a seismic component to the eruption build-up as well. Vesuvius had a major earthquake 17 years before its eruption. A report of ‘tainted air’ at Pompei after the earthquake could be due to gas emissions from Vesuvius after the earthquake although this is speculative. Krakatau suffered a major earthquake five years before it went boom, and seismic activity in the area increased after that time. Pinatubo suffered a major (M7.7) earthquake a year befor its eruption, and steam emissions were first reported shortly after this. Santa Maria suffered a major earthquake (M7.5) 6 months before the eruption, although it should be noted that seismicity at the volcano had begun already 3 months earlier. The VEI-6 eruption of Huaynaputina happened a year after a major earthquake. Archeology at Santorini indicates damage from an earthquake some time before the eruption.

Does this mean that the earthquakes caused the eruption? That is hard to prove. These large earthquakes are tectonic, not volcanic, and they were not caused by the volcano. Large earthquakes are also not that uncommon. The events seem to be normal for the region, to happen perhaps once a century or so, but close enough to the eruption that people noticed it.

Can we make it sound plausible? How can an earthquake cause an eruption? Charles Darwin was the first to suggest a relation, when he noted that four volcanoes erupted in Chile shortly after the major earthquake (M8+) that he experienced there. Not all of these four eruptions may have been related to the earthquake though. An earthquake can’t cause eruption directly. Even a large earthquake does not destabilize the magma chamber by shaking, nor does it squeeze the magma upward. What can happen instead is that the earthquake causes fracturing at the surface: this can cause a flank collapse, and release magma that is already close to the surface. Slopes of volcanoes can be at the limit of their stability, steep and with poor cohesion. An earthquake can do notable damage.

The Hoikkaido earthquake of Sept 2018 (M6.6) caused landslides across this mountain range. The soil came from pyroclastic flows from a large volcanic eruption 9000 years ago (Tarumae caldera) , topped up by a further eruption 3000 years ago. It was loose, porous, and had been thoroughly wetted by a very wet August, followed by a typhoon one day before the earthquake.

A second way an earthquake can cause an eruption is by unlocking a fault. A locked fault does not give way easily, and will not allow magma to intrude. But unlock it, and the stress reduces dramatically. It may now be possible for magma to get in, and open up a pathway that allows it to migrate up.

The typical time between a large earthquake and a large eruption seems to be a year to a decade. (This assumes that the two events are related!) That is not enough time to fuel a VEI-6 (or even VEI-5 – it might just do a VEI-4). Magma supply rates are normally around 0.001 to 0.01 km3/yr. Instead, rising magma can re-heat an existing reservoir, one that has been cooling for some centuries. The magma will have turned to a slush, filled with crystals. The new heat re-melts the silicic mush, and much like microwaved honey, it becomes mobile. This happened in Yellowstone, where its last eruption 70,000 years ago(!) came 10 months after reheating of the magma.

Reheating is a common cause of large eruptions. The VEI-5 Quizapu eruption of 1932 (on the flank of Cerro Azul) came after a reheating episode. The funny thing here was that the same thing had happened at the same volcano in 1846, but the earlier eruption was effusive while the second one was explosive. Other than that, the eruptions were the same size (5 km3). Why this difference? In both cases a dacite, cooled magma chamber was recharged by andesite at 1100 C. In 1846, this led to an increase of the magma temperature by 50C, which made the magma less viscous. The gas in the magma chamber escaped, and the remaining fluid magma happily fed an effusive eruption. In 1932, a smaller amount of andesite entered the magma chamber, and the temperature increased only by 20C. But now the gas had already gone and this changed the response by the magma to the heating. When gas bubbles take up a significant part of the magma volume (say 10%), the heat that causes the magma to expand compresses the bubbles. The bubbles take up much of the excess pressure. Without gas bubbles, the magma can’t expand because the volume is already full. This causes a rapid rise of the pressure, something that didn’t happen in 1846. The larger pressure (from a smaller recharge event) led to a strong explosion.

From Degruyter, W., Huber, C., Bachmann, O., Cooper, K. M., & Kent, A. J. R. (2017). Influence of exsolved volatiles on reheating silicic magmas by recharge and consequences for eruptive style at Volcan Quizapu (Chile). Geochemistry, Geophysics, Geosystems, 18, 4123–4135. https://doi.org/10.1002/2017GC007219

The following videos shows how an explosion deep underwater can cause a much stronger shock wave than one near the surface. This is because of the same effect: a liquid such as water (or magma) is not easily compressible, and it gives very strong pressure shocks.

To summarize what we found: large eruptions are more likely to happen in volcanoes that have been dormant for some centuries, letting the magma chamber become cool and stale. When new magma recharges the magma chamber and reheats it, the pressure can shoot up because there is no gas to soak up the pressure. The explosion can now happen within months to a decade. An earlier eruption can make the next one worse by degassing the magma further. A large tectonic earthquake in the region can trigger a recharge event, and can set up the volcano for the big stage. (It should be noted this is still a a rare event. Most large earthquakes near most dormant volcanoes don’t do this.) As an aside, the fact that the eruption is triggered by reheating suggests that there may be little inflation until close to the eruption itself. Don’t expect an extended warning!

Future calderas

The big question is now whether we can see this coming. Phrased a little better: if you were to look at us in the year 3000, which 3-4 volcanoes would have been replaced by new, large calderas?

A VEI-7 evacuates a lot of volume. That means that we should be looking at decent-sized mountains which have this volume. That won’t catch all, since some smaller mountains may have a surprisingly large amount of magma underneath but you have to start somewhere. Tambora was a stratovolcano over 4km high, and was among the highest peaks of Indonesia. Rinjani also must have been a large mountain. VEI-6/5 progenitors, on the other hand, may be less striking. Pinatubo and El Chichon were not that notable. We want a volcano that is listed as dormant. A good sign of this is the presence of erosion; a smooth stratovolcano like Fuji suggest a high level of activity, even if the most recent eruption may have been centuries ago, and that is not what we want. A weakness in the edifice may ‘help’. Large eruptions are often associated with flank collapses, and these are more likely to happen in (overly) steep volcanoes. The region in which our dormant volcano is located should still be volcanically active: the UK Lake District is an impressive old volcano, but it does not qualify fur us. Finally, other large calderas in the region are a good sign, as the potential for VEI-7’s may be build into the fabric of the local volcanoes.

Let’s give an example. Kamchatka has a history of large eruptions. Are any mountains there looking risky? Well, yes. Bezymianny is often mentioned, as it suddenly became active in 1955, after a long repose, and has been doing decent explosions almost like clockwork since. But it is a bit small. There is in fact a better candidate right next to it.

Kamen is the second tallest volcano in Kamchatka (4579 m), is dormant, steep, has erosion features and a flank collapse scar that is a little over 1000 years old. The flank collapse left a slope of up to 70 degrees. The other slopes are 30-45 degrees. This is a seriously steep volcano. Kamen is flanked by two highly active volcanoes, Bezymianny and Klyucheskaya Sopka. The latter is a beautiful Fuji look-alike, 180 meters taller than Kamen (making it the tallest volcano in Kamchatka), and active every few years – the last eruption ended only in July. And this world-class volcano (Klyucheskaya Sopka) is only 7000 years old. With such neighbours, what is the risk of another magma recharge in Kamen? 1000 years from now, will Kamen still be there or will Kamchatka have gained another lake?

Kamen, with Klyucheskaya Sopka behind it

When we asked the same question a few years ago, cbus came back with some suggestions. I will re-issue his candidates here, for you to consider.

1. Kronotsky – Kamchatka

Kronotsky is not quite as tall as Kamen but still reaches a respectable 3528 m. It is steep, with slopes of around 35 degrees. It seems to be in a long period of repose, with the only reported activity of the last century a small phreatic explosion in 1923. The summit crater is reportedly plugged with a volcanic neck (whatever that means). The edifice is likely weakened by glacial dissection, and it sits in a region where every other nearby volcano has gone caldera in a large manner. As such, if it wakes up, it very well may go boom in a dramatic fashion, possibly due to a large slope failure, leading into a caldera eruption.

2. Ulawun – New Britain

Ulawun follows a similar trend: a tall conical edifice in a region of many caldera large eruptors. It is located about 130 km from Rabaul and at 2334 meters is the highest mountain in New Britain. Similar to Kronotsky, there is evidence of slumping and existing edifice weaknesses at Ulawun. In fact the risk analysis for the volcano specifically identifies slope failure as a concern. It states that Ulawun is 400 meters higher than most of the volcanoes in the Bismarck and may be at the limit of structural stability. If it is anything like it’s neighbours (which is fairly likely), it could be approaching the end of its life-cycle. This would result in a caldera eruption, where it would then start to rebuild in a new cycle afterward. It is an active volcano, with a significant eruption as recent as 2019.

Ulawun, 2019

3. Agua – Guatemala

Agua, seen from a distance of 80 km

Not much is known of this Amatitlan somma volcano, but it’s enormous (3760 meters tall), steep, in a region where many massive flank collapses occur, and in an extremely active volcanic region even though there are no known eruption from Agua itself. The magma supply may have simply been diverted to another nearby volcano, but it also could just be plugged up after growing so large, which may not be a good thing.

4. Almolonga – Guatemala

Almolonga breaks the mold from the previous candidates. It is not the type of volcano that builds a large edifice, and instead is a dome complex that does not have one central vent, and has some very sticky and viscous magma. It features a ring-dike configuration of dacitic and rhyolitic lava domes. In a lot of ways, Almolonga looks much like a resurgent dome complex of a large caldera, but the only caldera it has is a small 3km caldera which may be more of a crater than a true caldera where the magma chamber was destroyed. Another worrisome part of Almolonga is that it sits in a very similar tectonic environment that produces other large calderas – one with both extension as well as subduction magmatism. Amatitlan and Atitlan both sit to the south of it, and I wouldn’t be surprised if it were very similar to those volcanoes.

5. Laguna Del Maule – Chile

Del Maule has been inflating significantly for quite some time now. It covers a large area, and quite a few publications have noted that it could be a large eruptor if it decides to go. Luckily, it’s in the middle of nowhere, so not so many people will be affected. Against it, the very fact that it inflates may indicate that the magma is behaving fine and that the next eruption will be a normal (for this volcano) VEI-4. Who knows?

6. Novarupta – Alaska (USA)

Yes, Novarupta had a huge eruption just over 100 years back. With that said, I have a suspicion that this could be more of a Crater lake type situation, where we see a large VEI-6 that is more of the precursor than the end-result. The alignment of the Novarupta vent in the middle of 5-6 volcanoes suggests that the primary Novarupta magma chamber is very large, and located centrally away from the small Katmai Caldera. This could mean that there is still a lot more down there that could re-erupt with a decent bit of recharging. Certainly not out of the realm of possibility within 1000 years.

7. Ata Caldera – Japan

Ata caldera with Kaimondake in the background

Most people here know about Sakurajima and Aira Caldera, but Ata may be the one more worth worrying about right now. It is located at the head of Kagoshima Bay, 40 kilometers from Aira. Ata is just as large, and unlike Aira, has not been releasing pressure since 885 A.D. Prior to this date, the somma KaimonDake would have frequent VEI-4 eruptions, but everything in this area has gone quiescent since then. That to me is somewhat worrying. Ata also seems to love creating large phreatoplinian eruptions that form maar caldera structures, which would be a disaster if this were to happen.

This completes cbus’ list. But what do you think? Which volcano keeps you awake at night, either in fear or in expectation? In 1000 years time, which volcano will unexpectedly be missing, and will have been replaced by a large caldera? Let us know!

And if you like this, you may be interested in the NDVP list as well, available at https://www.volcanocafe.org/the-new-decade-volcano-program-ndvp/

81 thoughts on “Future calderas

  1. A magnificent, if rather disturbing, post. It almost demands that the VC community supply their own possibilities for a volcano which will at some point go Boom in a serious way. So, here’s mine in no special order

    IOTO. Nothing needs to be said – VC itself has rated Ioto as well up there, with its sustained inflation.

    TAJAMULCO (Guatemala). A Very large (prominence 3980m), youthful-looking cone yet with no historic activity apart from (poorly reported) phreatic explosions. If Agua is on the list Taj should be too.

    SOUTH SISTER (Oregon USA). Last active acout the 13th-14th Cent., but these eruptions were fissure fed dacites, more silicic than the bulk of this volcano’s history; add to that the recent episode of uplift in an area a little south of the main cone – in fact, not too far from where the 14th C activity came from

    TULUMAN/ ST ANDREW STRAIT. A curving chain of small Rhyolite cones . At least two historic eruptions, but the GVP says it “may represent an incipient caldera ring fracture” Which would be -in the VERY long term- Very Bad News Indeed

    ILIAMNA ( Cook Inlet, Alaska)Heavily eroded with scars of flank collapses, and very little in the way of confirmed historic eruptions; most of the frequent eruption reports are thought to be just unusually vigorous fumarole plumes. Because despit Iliamna’s shortage of the red stuff, it has a sustained and powerful record of fumarole activity for several centuries at least. So there’s still heat down there. And its Cook Inlet beighbours are a violent bunch (Spurr, Redoubt, Augustine)

    Anyone else got thoughts on likely offenders? BTW I wouldn’t have Ulawun as a caldera candidate. Flank collapse, definitely -over-tall, steep, with evidence of structural instability, but with frequent eruptions, some including fairly fluid lava flows. Ulawun’s quiet neighbour Bamus might be worth looking at, though.

    • Mount Jefferson, at the Northern end of the Oregon Cascade Range volcanoes. Despite being quiet since the last ice age, and being heavily eroded as a result, geological studies by the USGS have found ash deposits some distance from the mountain, strongly suggesting that it produced large, explosive eruptions prior to its current, lengthy period of quiet. It is also flanked by the recently active Mount Hood, 40 miles to the North, and other ,more recently active volcanoes to the South. The USGS, despite Mount Jefferson’s long period of quiet, are very reluctant to call it extinct, especially given Mount Mazama’s 20,000 year dormancy before its catastrophic VEI7 eruption which caused its collapse into the present Crater Lake caldera 6-7000 years ago. Like Mazama, which the USGS also do not consider to be extinct, Jefferson is a long-lived volcano which may be going through a similar, long dormancy….

      In the Northernmost part of the Cascade Range, in British Columbia, Canada, lie 3 volcanoes which may be candidates for future calderas. All are significantly eroded, but not extinct:

      Mount Meager – only 2,400 years ago this volcano awoke, producing a large, explosive eruption of VEI5 size from the still visible Bridge River vent on its NW flank. It is still the most seismically active of the 3, and has active fumuroles near its summit and hot springs near its base.

      Mount Cayley – heavily eroded, but still has hot springs close to it and some seismic activity.

      Mount Garibaldi – only 40 miles from Vancouver and built by Pele’en style eruptions, making it very unstable. It also sits at the centre of the Garibaldi Lake Volcanic Field, with recently active volcanoes such as Mount Price and the Opal Cone in close proximity. The Opal Cone produced a large dacite lava flow since the last ice age. Seismic activity has been detected in the area recently, although unlike its 2 neighbors, Garibaldi does not seem to have any hot springs.

      These 3 volcanoes are clearly not extinct, and as Mount Meager proved, are still capable of producing dangerous eruptions – a future eruption of Garibaldi was wargamed only a few years ago to explore its potential impact on the surrounding area. Given their long lifespans, explosive natures and eroded states, they may be capable of producing future caldera-forming eruptions, in a similar way to Mount Mazama.

      What do you think Albert?

    • Frequent eruptions don’t preclude caldera forming behavior, especially if the frequent eruptions are not effectively reducing pressure build-up.

      But for Ulawun, the bigger risk is that flank collapses can easily turn into caldera producing eruptions, or simply act as extremely large eruptions on their own regardless of a formal caldera forming or not. Removing a flank from a volcano causes sudden and massive depressurization, which can basically activate a lot more magma than what would have normally been expected without a flank collapse or destablization.

      • Semeru is the tallest mountain on Java, adjacent to the Tengger caldera complex, and very active. It is also a conical stratovolcano. But it has mainly done VEI 2-3 eruptions.

        I guess the question is how tall can a volcano get on Java before it goes boom?

        • I think Semeru is close to the stability limit for height. And with the current active (dome extruding) vent at the head of one flank rather than at the actual summit, flank failure at some point would be a distinct possibility. Maybe one day adding another caldera to the Tengger complex?

  2. Thanks Albert, another great post. Somewhere on the Aleutian Arc would seem plausible. Lots of conical stratovolcanoes and a number of calderas. Maybe not one quite large enough to make the grade though.

    • Yes, that is absolutly possible. Think about Anak Krakatao, and there wasn’t this much of activity as on Nishinoshima. Actually the eruption slowed significantly down, but if it increases to his phase in June/july, sooner or later it will be a flank collapse on Nishinoshima.
      The ejected material was a lot more than on Anak Krakatao und this in a shorter period of time.
      Yes, it will collapse….

      • I am going to be pedantic. The old volcano was called Krakatoa or Krakatau. The new one grew up after the Portuguese empire, and has an Indonesian name. It is Anak Krakatau only. Other than that, I agree, a partial collapse is likely although I would not want to put a time scale on it.

  3. Corbetti is the volcano that will always be on the top of my mind when it comes to future caldera forming eruptions. It is under a large and protracted intrusion, probably has a melt volume around or above 16%, and has a large magma chamber.

      • That is very large. Yellowstone large.

        I just typed in “dacite-rhyolite” in the search by composition box. It pulled up a number of large calderas such as Ilopango, Asosan, Akan (Hokkaido), Aira, Emmons Lake, Coatepeque, and Toba.

        This is like a “who’s who” of calderas, and only 28 search results

        Other search results not mentioning having a caldera: Edgecumbe in Alaska, Bulusan in the Philippines, Atitlan, and Mocho-Chosuenco (Andes), Pacaya (Guatemala), Rincon de la Vieja, Santorini (it has a caldera but not as described by VOGRIPA), Tokachidake in Hokkaido, and Toya in Hokkaido.

        • Africa, and the Andes are very under-covered when it comes about general knowledge of the very large caldera systems.

          It’s relevant to keep in mind that the caldera from the Tambora eruption is quite small in the grand scheme of calderas that you can find around the world. Even crater lake, which is something larger and well known as one of the largest eruptions of the last 10,000 years is probably about average for a caldera.

          • True. And the largest recorded earthquake was in Chile-Peru in 1960.
            Magnitude 9.5. It is a very active subduction zone.

          • More under-covered regions, and for self-evident reasons, are the calderas of the Tonga-Kermadec and Izu-Bonin arcs which are mostly submarine.

      • I just had a thought. What if the volcanic-like conditions described in the biblical Exodus story were caused not by Santorini (the date is off) but something in East Africa?

        • I think it’s more likely the date is off due to biblical inaccuracies than that there were two VEI-7 events within the same region and within only a few years of each other. The bible has gone through all manner of translations and we’ve changed calendar systems multiple times since Thera blew its top.

          Consider that Jesus was actually born in the summer of 4 CE, not shortly after the winter solstice of 1 CE. If dates for biblical events are that far off by 2000 years back, think how much worse it might be nearly twice as far back.

          At the same time, Thera is just too neat a fit in every other respect. Part of Egypt’s troubles came from the sudden loss of their trading partners. The biggest merchant marine operating in the Mediterranean at the time was the Minoan fleet, half of which was obliterated on the spot by the Thera tsunami. The Minoan civilization collapsed (and gave us the Atlantis myth) not long after. The Aegean and parts of the wider Mediterranean were rendered unnavigable for years by pumice rafts (there go Egypt’s other sea-borne trading partners) and the Minoan civilization had been heavily dependent on such trade. It was easy pickings for Mycenaean conquest in its crippled post-Thera state, between the direct damage and the loss of its main source of economic productivity.

          The Plagues themselves fit a combination of a “year without summer” type climate disturbance (though without a pronounced cooling, not that close to the equator) and excess nutrient runoff effects (perhaps phosphorus from the ash). The latter could have caused red tides and other blooms of microorganisms. Rains of frogs and other strange things have been known to occur after severe thunderstorms that produced waterspouts, so if the odd weather included such storms even the more seemingly outlandish Plagues are explained.

          Consider, too, what the people must have witnessed: even that far away the eruption column likely extended above the horizon during the earliest, most vigorous phase of the event. To a bunch of scientifically illiterate Bronze Age people it may well have seemed that the hand of God had reached up over the rim of the world and started flinging stuff down from the heavens, shortly after which calamities began, ranging from weather anomalies to vanishing sea-trade. It’s no wonder the priests of the time made such a huge fuss over it! Judaism especially seems to have been strongly influenced. It is clear from many passages that its god is a volcano god. I mean, one of his manifestations is as a burning bush on a mountaintop, not to mention his penchant for helping produce fecund crops when he’s not all wrathful (volcanic soils?), his wild swings of temper, and his methods of destruction when he does get wrathful (flood, rains of fire, pretty much everything the poor people of Sebesi got from Krakatau).

          The predicted events for the End Times in the bible also seem volcanic in character, excepting the ones that are political in character instead. Rivers and seas turning to blood (contamination and/or red tides), earthquakes, the blackened sun and blood moon … the latter could be eclipses, but not at the same time. Lunar and solar eclipses can never come closer to each other than two weeks. But volcanoes absolutely can blacken the sky and can also cause all manner of weird sun and moon colors. Again ask witnesses of Krakatau. Most likely the apocalyptic passages in Daniel and Revelation are just as volcanically-inspired as those in Exodus, and most likely they refer to past events. It is notable that scholarship has rather strongly tied the Antichrist figure to the Roman emperor Nero, during whose reign there was a very large VEI6 in Vanuatu, a Krakatau-sized event that could likewise have caused apocalyptic skies seen around the world …

          • The Biblical god is not a volcano god.
            However, parts of the Bible, including the prophets, describe events past and future that resemble powerful volcanic events (dim light at noon, sun looks red, so forth) and in the Book of Revelations, what appears to be a meteor strike.

          • One of the reasons I thought this is that Moses and the gang, once they crossed the Red Sea, headed south into the Sinai desert. If they were guided by a column of smoke by day and fire by night (this is very obviously a volcanic eruption) would that not be in front of them?

            There are also volcanoes in Yemen to consider.

          • I’d say it looks like the Old Testament god started out as a volcano god, but later theologians and philosophers shifted their concept of god to a more abstract one. Probably associated with the shift to a non-intervening god. The writers of those Old Testament passages describe a god frequently intervening in their affairs, usually through what look a lot like volcanic phenomena. Later writers (from Roman times through medieval to modern) clearly have a different concept, of a god who intervened long ago but does not now, and view this god differently.

            Of course even that simplifies. There will have been branchings of belief during all of that time (3600 years!) producing numerous splinter sects. The ones that added whole new books and renamed themselves (Christianity and Islam, and more recently Mormonism) are just the most overt ones (and themselves have major internal splits now). Every single branching of this family tree of belief systems brings with it a branching of their concept of god … there’s probably quite a lot of variation now, even just within the portion of that tree that still considers itself to be Judaism.

  4. The Nisyros/Gyali centre that looks extremely akin to Santorini and has had temperatures, quakes and gas output creep up in the past 20 years could come up with something that affects nearby Kos/Turkey.

    Uturuncu seems pretty dead on given the rate of magma accumulation there and the surrounding area.

    How often do volcanoes that grow on the edge of calderas go caldera themselves? Seems to happen a fair bit in extension areas like the Taupo Zone. And do we consider these separate (whakamura/taupo for instance) bearing in mind they probably have a common deep source?

  5. Queen Mary’s Peak. It has decent size, 2062m above sea level. There have been a few small eruptions during the last centuries. Including one subsea in 2004, which indicates that the hot stuff has access to water. Throw in a surprise large earthquake, crack, water inside, Boom!.

    Do I rate this as being high on the list? Nope, but for some weird reason it was the first one that popped into my head after reading the article.

    • Probably better to call it Tristan da Cunha, as the mountain and island is named, as Queen Mary’s Peak is just the summit of the mountain.

      • These atlantic chains seems to be linked to perpendicular fracture zones east of the MAR with shield growth and collapse their main forte – Tristan, Cumbre Vieja or Fogo for instance will have a significant landslide/flank collapse at some point. Although Teide’s caldera is huge I wonder if they have the firepower to majorly erupt without being set off by some sort of gravity failure allowing the water to broach the magma chamber a la Anak Krakatau.

        • Fair point but Anak Krakatau did not have a magma-water encounter. It was ‘just’ a flank collapse. I do think though that Daddy Krakatau did do just that – a flank collapse led to its final explosions. We’ll never know for sure.

  6. Excellent article. Here are some guesses:

    Taupo could go again some time in the next 1000 years, as it has been quite a long time since the last VEI7.

    Popocatepetl worries me just because of its size and steepness.

    It would not surprise me if Rinjani had another large eruption, it has a rebuilding cone.

    There was a paper in Nature a couple years ago arguing that Sinabung was accessing the Toba magma supply. Which other volcanoes in that area can do the same? That area is prone to very large earthquakes.

  7. Illiamna is a good guess. i tried to comment earlier but maybe pushed the wrong button… Best! from still covid free motsfo (Thanks, God)

  8. Etna is a good guess for a future drainage caldera: only problem its erupting all the time now, letting off pressure. But Etna haves a massive magma supply, and have ammounted a pretty sizable magma chamber.
    1669 was like Holhuraun and Leilani but placed in Catania. Souch an eruption woud cause astronomical material damage today. If Etna goes caldera it coud be a drainage event or a basaltic plinian.
    If the 1669 rift drainage caused a caldera collpase at the summit: I dont know that yet.
    The last major caldera event was plinian summit long ago.

    • Etna is extremely rich in magmatic water vapour and other gases and that can drive large tephra eruptions despite being relativly fluid basaltic.

    • Etna is a rotten volcano , with all those summit craters degassing for at least a century all it will take is something low on the flank like 1669 and the outline of the caldera is already proscribed. The Val de Bove will get a little bov-ier!

    • Log time lurker, I think the central crater that existed at the summit until the 1940s was the collapse from 1669, it was quite small considering the 1669 eruption volume ranges up to a high of 1 km3 and a lot of that erupted very fast in the first week or so. Is indeed a very rare but scary scenario of a lava flood inside an actual city, Cantania was beyond the initial high volume flow in 1669 and only invaded later but today would be a different story.

    • Etna haves a pretty astonishing magma supply
      80 million cubic meters every year is pumped into Etna.
      Thats far more than any normal subduction zone volcano. Etna haves a massive supply at current.
      Etnas geolgical setting is complicated: But probaly is decompression melting of mantle materials, the complicated geological setting there. Etna is extremely active and open conduits too.
      The productivity of Etna is more in line of mantle plumes than any subduction zone.

      Etna is NOT a mantle plume
      But is the result of the complicated collisional – tectonics and rifting in mediterranean that includes decompression melting.
      Why etna exists is very very complicated.

      • Since 1971 the supply rate has gone up, along with the southeast crater complex being created. with a supply of at least 60 million m3/year over that time about 3 km3 of magma has been erupted or at least intruded into Etna since then.

        Right now the summit is weakly active so the magma column is very high, well over 3 km above sea level. The december 2018 eruption was fed out of shallow summit magma but there was also a deep eccentric intrusion under the south flank in the same place as a similar intrusion in 1989 so things might already be getting close… The 1669 eruption started very fast and erupted lava that was as hot and liquid as lava in Hawaii, about 1160 C, during the first week before stuff from the upper levels of the volcano drained through afterwards and Monti Rossi was created.

        • The system gets stuck in a feedback loop, increasing supply, increasing flank movement (slow-slip events), increasing rift activity until something brings an end to it, like the 1669 eruption. So eventually the grand finale is coming…

          This behaviour is very common in very active shield volcanoes, each does it a different way but Piton de la Fournaise, Kilauea, Karthala, Ambrym, Ambae and possibly others seem to follow the same general pattern.

          • There was an eruption in 1030 that was similar to 1669, though not as large. Back then was a long time ago though, the record is poor, so its precursors are not known. In general fluid magma at high elevation is a recipe for a big lava flow.

            One place stands out in particular to me, im only new but if I can submit article entries I have something for that.

          • If it plays similar to the cycle ending in 1669 I would expect long-lived effusive eruptions from upper flank vents that produce tube-fed flows, like the Bronte flows. In that case we are still not in the final ramp-up but things are sure to become gradually bigger at Etna over the next several decades…

          • Eruptions in the 17th century were not quite so continuous as recent decades though. Erupted volumes since 1971 is probably comparable to that of the 17th century, maybe a bit less.

          • Impressive indeed: probaly will be a large Etna drainout soon.
            In the geological future ( 100 000 years Etna may reach a conciderable size ) but the supply can vary alot, Etna is 600 km3 and 500 000 years old, so its been fairly slow during earlier times, during the slower times the system been more stale and sillic and explosive.
            Andesite – trachyte was common products during the more stale times.
            Now in modern geological Etna times, Etna haves a massive supply and is fresh basaltic and effusive. Etna seems to be feeding from the complicated tectonic settings there.

            Etna and the Mediterranean are in the long term doomed.
            Africa is moving towards Europe and Mediterranean is dying.
            Once the strait of gibraltar is closed, the sea will start to evaporate very quickly in the hot dry climate. The clear blue Mediterranean will become a wast salt desert. And later the whole area will be pushed into oblivion as a iran like mountain range belt forms in Europe when Mediterranean is pushed to a close.

            I wonder how long volcanism in Mediterranean will edure…

          • Read somewhere that Etna is slipping east a few centimetres a year, think a large collapse has happened in the past (affected Lebanon?). You can’t fight gravity!

      • https://m.youtube.com/watch?v=SiYp84QT9ks

        Etna is erupting all the time now: the basalt looks a kind of viscous as it often is for Etna. It coud be the upper magma column thats cooling and convecting.
        2015 – 2016 paroxysms had hot ( 1100 C ) fresh magma that had an extremely high gas content with mainly water as volatile agent. Since 2017 its been getting somewhat cooler.

        But Etnas basalt magmas are a bit cooler and often far far more viscous than the stuff that comes out Iceland, Galapagos, Africa and Hawaii. Etnas magmas haves a similar viscosity to Pacaya in Guatemala.

      • Yup thats true: you almost never finds any pahoehoe or smooth fluid splash marks or ”smooth glass skinns” on Etna.
        Most of Etna is Aa lava and its channels and spatter cones haves a kind of rough texture. Its because of Etnas higher viscosity. Cinder cones and scoria dominante on Etna as fountain products.
        Etnean Aa lava can be massive 10 meters thick fronts that crushes everything in their path.

        https://m.youtube.com/watch?v=Cz1U-jeUf3A
        Etna haves her hawaiian moments too with fast moving lava channels and splashing fountains and gushing vents.
        But its always more viscous than Hawaii and Galapagos, and the white steam clouds that shows its much higher water content. Its rich in magmatic water vapour and CO2.

        The only ”real” pahoehoe field on Etna can be found near Bronte on its west side. And its rather sizable and certainly lasted a few years. The lavas their are full of small crystals and are known as ”pea lavas” because of that.

  9. Regarding the subject of earthquakes causing eruptions.. the M6.9 May 4, 2018 quake in Puna seems to have triggered the half-Holuhran sized eruption. I wonder if there ever will be a major slipage on the Hilina slump. After all, didn’t Maui Nui have a major one?

    • I wouldn’t say the earthquake triggered the eruption, but the other way around:

      The intrusion from Puʻu ʻŌʻō down towards Leilani started on April 30. Deflation of Kilauea’s summit started on May 1 and the Halemaʻumaʻu lava lake started to drop. The first eruptive fissure opened in Leilani on May 3. The earthquake happened on May 4, so the eruption was already ongoing and not triggered by the quake.

  10. Surprised to see one of my old caldera lists pop back up 🙂 .

    The reality is, there are a LOT of potential caldera-producing volcanoes out there. But there does seem to be at least a few general characteristics a lot of these volcanoes have in common, depending on magma composition.

    Alaska, Kamchatka, and a lot of Indonesia are littered with large remnant caldera systems. It’s hard to scroll through these regions on Google earth, see the large stratovolcanoes that have not yet gone caldera sitting next to 4-5 other large caldera systems and not think that they’re up next if they’re anything like their nearby bretheren.

    • The math bears this out. If there is a VEI7+ roughly every 300 years or so, and any given one takes several tens of thousands of years to recover to where it could do it again, then one would expect several times 30 volcanic systems to be, at any given time, at some stage of the build-up to such an eruption, and maybe 30 to be “getting close” (as in, only a few thousand years left at most). Those last would tend to show the signs described: steep, eroded edifice, lengthening dormancy, but in a still-active region. So the number of them we have identified in this thread is about what ought to be expected.

      • Am I correct in thinking we’re missing a fair few identified VEI6/7 eruptions over the last few thousand years? I think it’s quite possible that many of these eruptions have been carried out on the sea bed, there’s a lot more water than land and particularly around the Vanuatu/Tonga areas and in the deep arctic there seems to be a huge amount of hidden volcanics.

        Is there anywhere I can find information on unidentified spikes found in Greenland ice etc. from years gone by that haven’t been attributed to a volcano yet?

        • As was proved by the Skaftar Fires, it’s possible for a significant sulfate spike and even a mild “year without summer” climate disturbance to result from an effusive eruption, if that eruption is large and gassy enough. That complicates things, as neither short-term cooling events nor sulfate spikes necessarily arise from explosive events.

          Although such effusive events will make or enlarge a caldera, as was seen recently at Kīlauea and Bárðarbunga, the eruption products do not blanket said caldera, so dating summit tephras will overlook the effusive events and give you the most recent explosive event, or at least the most recent summit eruption. For example, an attempt to date the Kīlauea caldera in this way will likely get you the late 1700s and the Footprints Ash, even though there were dust plumes at the summit during the Leilani event, as those dust plumes did not involve new magma, only preexisting summit rock being rearranged.

          Thus there might be a known caldera with a known date earlier than some sulfate spike, assumed therefore not to be responsible for that spike, and it still could be, if an effusive flank eruption of large enough scale from that volcano caused the spike.

          Add in shallow-sea calderas, calderas that were prolific enough to already be obliterated by a younger event, and calderas that might have become well-hidden by erosion and other processes, and there are lots of ways the source of a spike or climate disturbance can elude us, especially for older events.

  11. A general comment: if you are a first-time commenter, or perhaps have been quiet for so long the system forgot about you, your comment is likely to end up in a ‘for approval’ queue. This is also known as ‘the dungeon’ by those people who spend more time in it than average. Please be patient and your comment will appear: it can take some hours if the dragons are having a nap. Once you are approved, further comments should appear without delay

  12. Axial Seamount haves a massive drainout caldera! whats the size of the lava flow that was produced from it?
    That lava flow is of course now buried under more recent flows.

    • Hard to know that, but it seems to be result of one single collapse ( clear cut )
      This is also on a mid ocean ridge where perhaps only 10% of the drained volume erupts.
      Its still huge, many times larger than holuhraun. But multiple collpases cannot be ruled out.

  13. New green stars at Reykjanes peninsula. Comments by IMO says likely due to magma intrusions during the last months

  14. Can anyone here estmate the size of the drainage event that formed Nyiragongos caldera?
    While not the largest, it must have been impressive, the crater is 1,5 km wide and as deep as 800 meters when its fully drained out as it was 2002. Today its filling up very quickly by lava lake overflows.
    The summit caldera cannot be very old, perhaps only a few 100 years old ?
    Looks like we are talking about a holouhraun sized event here…

    • And the volume may have gone underground, last collapse in 2002 happened after the eruption during a rifting event under Lake Kivu, if I remember correctly.

    • There is a big area of lightly forested lava that is exposed on the west base of nyiragongo, the volume is probably not that high but it must have been like the eruption in 1977, only a few times larger. Still probably pretty small volume wise given the typical <1m thickness of lava flows here but if it was anything like recent flows it must have been quite a frightening experience.

  15. I dont know if theres a sort of waiting list or something regarding how long you have to be an active commenter in order to contribute an article, but I have something. I was actually going to submit it ages ago but it is about Mauna Loa and the interest in Hawaii fell off after 2018 so I left it. It keeps with this articles theme of massive eruptions though 🙂

        • Sure. email them in and someone will have a look. You mentioned at one time you had send something in earlier but I don’t think we have anything from you that isn’t published. At least I don’t.

          • Just today.
            I have sent one candidate to that email several times in the past two weeks and I haven’t gotten a response so I just assumed it’s wasn’t up too snuff until I saw your comment.

          • Apologies Tallis, I’ve been dealing with redundancy at work for the past few weeks and I’ve been ill this week so they completely slipped my mind. I’ve put them both in draft for the dragons to peruse.

  16. https://imgur.com/a/PuhXGwX

    I think it wont be too long before we get some more lava on the Big Island, all the deep quakes are still there that took off in the last year, but now Kilauea is lit up like a christmas tree with dots, and not just its summit but also its upper east rift zone all the way to Pu’u O’o.
    Mauna loa too, its summit is covered in dots nearly all of them at the top of its magma chamber. Now we have both Grimsvotn to look forward to and Hawaii which is like Grimsvotn without the ice 🙂

  17. More green stars in iceland. Its cracking on a line now. Is this harmoni tremor or rocks cracking on the fracture line

    • Yes, this is an interesting and puzzling sequence of earthquakes, as they stand, but they haven’t been checked yet, so I suspect they’ll make better sense once they have. (The faults in this area are *across* the NA Ridge, to put it in a very amateurish way. Someone will put this in proper “geology speak” in a while, I hope.)

Comments are closed.