The Hunga Tonga eruption of 2022

Volcanoes can be quite predictable, in a general sort of way. We know that Grimsvotn will erupt – just not when, although it is fairly likely to be within the next two years. Similarly, Mount Rainier will erupt some day, although this could be centuries or millennia off. Six years ago, we predicted that Mauna Loa was 50% likely to erupt within 8 years. We were right, by dumb luck. On the other hand, our original prediction that Grimsvotn would erupt by 2022 is best quietly forgotten.

We have talked here in the past about which volcano would be the next large eruption. The consensus was that it would be one we had never heard of.

The consensus was correct. Hunga Tonga was this bolt from the blue.

Before the eruption

The volcano’s full name was Hunga Tonga-Hunga Ha’apai, often abbreviated HTHH. (I will here use the short-hand Hunga Tonga for the entire volcano.) It consisted of four islands, two larger and two miniscule. The hyphenated name combined the names of the two larger islands. The islands were on the rim of a submarine caldera. There were 8 such submarine volcanoes within about 80 km, of which this was the only one which reached the ocean surface. The map is shown above: note that the volcano to the west has had an impressive flank collapse. Seamounts always live precariously. The two islands were in effect elongated cliffs. The image below shows the cliff of Hunga Tonga, greened by vegetation which shows its age.

Hunga Tonga cliffs before the eruption


Our volcano was remarkably active. There were three reported eruptions in the 20th century, and now three in the 21st century. The activity had been increasing and eruptions were closer together. The 1988 eruption build up cones southeast of the islands. In 2009, a submarine eruption just south of Hunga Ha’apai lasted one week and build up new land which joined up with the older island. It did not last: wave erosion took it back below sea level where it formed a new shallow platform.

In December 2014 activity resumed, after weeks of earthquake activity. Now it was centred between the two islands. Over a month it build up a 1-km wide cone which came to connect the two islands. Now there was only one large island. Although erosion reduced the new land, the connection remained. This was the situation depicted above. Bathymetry now revealed that there was a pattern. There was a shallow caldera, less than 200 meters deep; the islands were on the rim of this caldera. The 2009 and 2014 eruptions had been on different locations on this rim. The location of the southern edge was not clear: the minuscule islands (or reefs) show a smaller ring, whereas the 1988 eruptions line up with other cones to form a larger one. It actually gives the impression of two overlapping calderas, a northern one and a southern one. However, this has also been interpreted as a larger caldera with some infill on the south and the north.


The series of eruptions since 1900 all ocurred around the caldera rim. This suggests that there is a magma reservoir that is deeper than the caldera is wide. The age of the caldera is not known, but ignimbrites on the island have been dated to about 1000 years ago. It has been suggested to be associated with a large tropical eruption in 1108 but this is highly speculative. We don’t know how large this eruption was, and whether it created the full caldera or only the northern one. In either case, it does not seem large enough for the claimed 1 degree cooling from the 1108 eruption.


On 20 December 2021 the eruption resumed in an explosive fashion. The ash column rose to 15 km, and the island was covered under 0.1km3 of new ash. This was probably a VEI-4 eruption, making it by far the largest explosion we had seen at this volcano. After this throat clearing, the eruption continued in a more typical fashion with small explosions which build up a new cone. The eruption centre was in between the 2014 cone and the original Hunga Tonga island. In the sequence of images below, panel b shows the island at this stage. Half of the 2014 cone had been blown away. The original coast line below the 2014 cone can still be recognized, but the ash ejections had greatly extended the land.

January 2022 started calm, and it seemed plausible that the eruption had ended. No such luck. On 13 January 2022, at 15:20 UTC a second big explosion occurred; the eruption lasted 22 hours. It destroyed all the remaining 2014 cone but left the 2021 cone in situ. The cloud now reached 18 km. The aftermath is shown in panel c. Much of the new land had gone, although some of that may have happened already before the explosion. Hunga Tonga again was two islands. From the location of the gap, we can see that this explosion had happened at the position of the 2014 cone, not the 2021 eruption centre. Now the eruption column reached even higher, at 20 km. The damage done to the island also suggests that this eruption was larger than the one from 20 December. One can guess that it may have been 0.3 km3 ash volume, in mid-VEI-4 territory, based on the fact that the cone that was destroyed contained a volume of 0.1 to 0.2 km3 above sea level. As there was now little of the new island left, it seemed plausible that this would be the end of the eruption, with perhaps some activity continuing at the bottom of the hole.


The cause of the January 13-14 explosion is not clear. How could pressure have build up in the old cone, while the new cone was providing a steaming, thus open conduit? Were there two channels active to the surface, and had the new one collapsed? And where did the pressure come from? In an oceanic environment, water is the most likely source. Had the 2021 eruption cracked the older conduit when it removed around half of the old cone? Somehow, the removal of the old cone had started the lead-up to the Jan-14 explosion. It is notable that the two VEI-4 explosions of December 2021 and January 2022 were the only eruptions since 1900 which initiated above sea level, on dry(ish) land. All other eruptions had started below sea level, as Surtseyan eruption. Is the difference just from the excess weight of rock above the conduit? Or is there another reason?

While it was assumed this was a good finish to the eruption (which after all was almost a month old by now), the volcano begged to differ. Completely unexpectedly, the next day there were real fireworks with several explosions close together in time. Two clouds reached 31 and 17 km height, and the plume reached 58 km. By the end, nothing was left of the new land, and very little was left of the old Hunga Tonga island. Hunga Ha’apai was also much reduced though not quite as badly damaged. The two miniscule islands or reefs were also gone.

It took days before we realized how large this eruption really had been. It is now a year later and papers on the impacts are still coming out. This was the most unusual and most difficult to characterize eruption since Krakatoa. Just one example – the two people who died in Peru were the most distant casualties of a volcanic eruption in recorded history. This was not normal.


Life – but not as we know it

But first, let’s look at an unintended consequence of the eruption. The 2014 eruption had created new land. Over time this should become occupied by a variety of life. The don’t have it easy. Volcanic ash contains little or no carbon, a rather essential requirement for food. There may be poisonous gasses coming from the eruption site. How does life establish itself in these conditions? This was last studied in Surtsey, but only decades after the eruption. After 2014, we had a new opportunity to learn: this was only the first case where such a new island survived for longer than a year since Surtsey. And so brave people (in hindsight, very brave) ventured out in 2017, to study the re-emergence of life in such a desolate post-eruption landscape.

They took samples across the new cone, the beach and the edges of the old vegetated islands. As expected, there was little carbon in the new material, at 0.3mg/g, ten times lower than the old edges which had received some organic sediments. Sulfur and iron were high, but there was also significant amounts of copper, vanadium and cobalt. The authors compare it to metal-contaminated industrial sites!

The life they were looking for were bacteria. And those were found, but of rather uncommon types. Cyanobacteria capable of photosynthesis and normally the first to colonize new surfaces, are absent here. Other types are similar to those found in Icelandic basalt. But the dominant types were those that are so-called autotrophic chemolithotrophs, which can obtained energy by oxidizing sulfur and iron. The authors note that there were similarities to bacterial communities around hydrothermal systems. They suggest the bacteria came either from within the subsea volcanic system of Hunga Tonga itself, having been brought up to the surface, or were blown in from nearby volcanoes.

This strand of research met a sudden end (luckily in absence of the researchers) in the 2022 destruction of the new cone. We will have to wait for a new long-lasting volcanic island to form which is safe enough to explore.

Water, water everywhere and not a drop to drink

The events of 15 Jan 2022 were remarkable. When the explosion was caught by satellites, I did not believe the reports of the height of the plume, of 58 kilometers! That isn’t normal. That is the top of the stratosphere, even touching the mesosphere. This height was reached only in the central part of the column, but still. Imagine what it takes to reach that height.

The column is not ballistic, by the way. The volcano does not throw out particles with a speed high enough to reach this far up. Air fiction stops the small particles very fast. Instead, the plume is carried up by heat. It is similar to how a thunderstorm forms, but in stable air. Convection comes from the difference in temperature at the bottom and the top. It is easier in a humid atmosphere, because as the air rises, it cools and the water vapour condenses. This releases heat, and this helps to keep the air warmer. Convection normally stops in the stratosphere, because here the temperature increases with height which suppresses the convection. Big volcanoes generate enough heat to get into this region, but rarely more than 20-25 kilometers. Hunga Tonga reached the stratosphere and kept going. Why? It was an extremely wet plume: somehow the explosion had evaporated enough water to be saturated.

Most volcanoes pulverise rock and produce ash. This one did that to some degree as well, but it also added quite a bit of ocean to its ejecta. This is something the VEI scale had never considered!

How much water are we talking about? The eruption increased the water in the stratosphere by 10 to 15%, or 0.15 km3 of water! It ejected 300 times more water than SO2. The stratospheric water came from the upper umbrella cloud in the picture above: it was injected at about 30 km altitude. We are now living with the consequences. Stratospheric sulfate has a cooling effect on the ground, because it absorbs incoming sunlight. Stratospheric water has a warming effect because it reflects outgoing radiation back to the ground. It is a fairly small effect of around +0.035C. In comparison, the ejected sulfur has a cooling effect of -0.004C – it was not a major eruption as regard to sulfur. But the water is not uniformly distributed. At first it mainly affected the southern hemisphere, later it spread to the north. The water will take several years to be removed, and it may take as long as a decade. The water warms us but cools the stratosphere (there has to be a balance).

Is the peculiar weather we have had last year and now caused by Hunga Tonga? We don’t know – but it is possible. It is difficult to know what of our weather is caused by Hunga Tonga, what comes from the rapid global warming, and what is just weather. There was a suggestion it would cause a colder winter in Europe, but in fact we are seeing the opposite, with a cold winter in central and east Asia. Was this the reason for the strangely subdued Atlantic hurricane season? Again, we don’t know. We have never seen an event like this before! For more discussion, see


But how large was this eruption really? Shortly after the eruption, we estimated VEI 5.8, based on the damage done to the islands. That is still a plausible number, and would make this the largest eruption since Pinatubo. But larger estimates also exist.

The best values would come from measuring the size of the hole. That is now possible: detailed bathymetry was obtained late last year, which shows the increase. It can be compared with the measurements taken in 2015. This can of course not separate the impact of each of the three large eruptions. The assumption is made that all of the change was due to the final bang. That seems reasonable but the reader should be aware of it!

Comparing the images, it is clear that there has been considerable reshaping inside the crater rim. The hole is much deeper now and the inner ring in the south (or the infill platform) has gone. The outer rim has survived relatively unscathed.

A better view can be obtained when making a profile. The east-west profile shows that the central region is now 850 meters deep, whilst it was close to the surface below. Comparing the two profiles, and assuming this difference holds across the entire caldera, gives a volume of 8 km3, larger than what we calculated.

In principle this is the rock volume. To get the ash volume that is used in the VEI scale, it needs to be scaled by a factor which depends on the density of the rock. The ratio of rock density to ash (tephra) density is a factor of around 2 for basalt. But the old caldera was likely filled with lower density material, mainly ash from previous eruptions. The shape of the new caldera, in between a cylinder and a bowl, may also suggests that the eruption was in somewhat lower density material and did not penetrate the denser material of the surrounding rock. I will therefore assume a factor of 1.5. This gives us an ash (tephra) volume of 12 km3, making this eruption a low VEI-6. There is still a large uncertainty, but it seems likely this was only the 4th VEI-6 eruption since Krakatoa, and was probably a little larger than Pinatubo. Krakatoa was larger, though.

This classification gives a problem, since the atmospheric ash was nowhere near this amount. We know that from the ash fall on the Tonga islands, and the rather low sulphate in the stratosphere also hints at this. It turns out, the answer lies underneath the sea. Much of the ejected material is on the outer slopes of the mountain. Some even was deposited in underwater pyroclastic flows which reached almost 100 km distance. It was these underwater flows which cut the communication cables to Tonga, some 40 minutes after the eruption.

So only about a quarter of the erupted column made it into the atmosphere. Surface-based measurements made it a VEI-5 – but the full story was bigger.


Only recently has the precise sequence of events become clear. There was no nearby camera (and neither would that have shown much, after the first explosion), but the explosions produced earthquake waves, and these were measured across the world. It has taken a long time to decipher the sequence of P waves around the shores of the Pacific ocean. It has now shown the following timeline.

The eruption started at 4:02am (UTC) with a small explosion, followed by a second one at 4:10. At 4:12am the ramp-up began, with a major explosion at 4:15, followed by ones at 4:18 and 4:20am. Now it ramped down, with smaller eruptions around 4:24, 4:17 and 4:30am. Note that these are measured from earthquakes, and not all of these events may have broken the surface. Of the 30 separate events are detected, 14 are classified as eruptions and the others are ‘not known’. And in reverse, not all explosions may have caused measurable earthquakes.

How does this compare with the satellite measurements? Interestingly, the ash cloud was first detected at 4:10am, before the large explosion. This cloud must have started around 4:00am and is likely related to the first, small P waves. However, the atmospheric waves agree that the main event was around 4:18am, around the time of the three main explosions.

After 4:30am all seemed quiet on the western front. (This may not have been entirely true: the seismic noise was now limiting the sensitivity.) Four hours later, there was a small replay with a larger explosion at 8:41am, but not at the same scale as before.

But what really happened? The ‘weak’ explosion at 4:02am may already have been larger than any of the previous historical events at this volcano. Somehow this explosion set the scene for the Pinatubo-sized eruption that followed. the first event was likely aerial or at very shallow depth, since it pushed ash out into the atmosphere and didn’t shake the earth so much. The very large eruptions were below sea level, as indicated by the fact that only a quarter of the ejecta managed to get air-born. The picture that suggests itself is that the first explosion cracked the conduit or dike to the surface, and water rushed into the hole. Water turned to vapour, pressure increased, until the bottom of the caldera cracked. However, this pressure-build requires a sealed chamber which means water could not have gotten in. Perhaps a better picture is that the water was already there, in the form of wet rock. The first explosion removed some of the weight of the overlying rock, the reduced pressure lowered the boiling temperature and all of the water in the wet rock instantly vaporized. Now the big explosion was underway.

The shape of the caldera suggests this may have happened at something like 600 meters depth. Note that this was not directly below the previous eruptions: the Jan-15 explosions happened near the centre of the caldera. The water-rich plume pushed through the original ash cloud and reached towards the mesosphere.


Although the ash was mostly deposited under water, much of the energy went into the atmosphere. The pressure waves break the water surface and set up a powerful atmospheric wave. The energy of this has been estimated at 60 MT of TNT, a bit of a silly unit since volcanoes do not use TNT. It amounts to 2.5 times 1017 Joule of energy. I have no idea how many Olympic swimming pools this is – ask NASA. For a better comparison, this is the same energy as released in a magnitude 8.44 earthquake! But the measured size of the earthquake was around 5.8. Even if we assume this was a severe underestimate, it means that only 0.1% of the energy of the explosion went into seismic waves in rock. It is another indication that the explosion did not take place in solid rock but in material that was very good at damping. Wet soil would do nicely.

What can this amount of energy do? It is sufficient to vaporize 0.15 km3 of water. That is about how much was put into the stratosphere! It means that the explosion could indeed have been caused by explosive vaporization of water.

Volcanoes easily have this amount of energy available. The energy is in the magma: the energy in the heat of molten rock. St Helens, an eruption that was rather smaller than Hunga Tonga, produced 1 times 1017 J in thermal energy. The problem is, though, to get this energy to do something explosive. Water provided that opportunity.

What else could this energy do? Imagine 10 km3 of rock: this amount of energy would be sufficient to raise it 1 km into the sky. Fragmenting solid rock into ash is, of course, extra.

The energy of a volcanic eruption is not normally published since it is too hard to measure. Hunga Tonga provided a unique opportunity.

The explosion caused big waves in the atmosphere. In Manchester, we saw the pressure wave pass 7 times (in my recollection) about twice per day. The ringing of the atmosphere in fact continued for a week. Nothing like this had been seen since the heyday of Krakatoa. That was a bigger eruption, but the effect on the atmosphere was apparently similar.


The explosion caused a large tsunami. In fact it was quite unexpected. Much of the destruction of the old islands of Hunga Tonga was probably due to the water wave which took tens of meters off of the rocks. It is hard to know exactly how high the wall of water was. Waves of 1 to 2 meter high were reported widely across the shores of the Pacific. These caused the two casualties in Peru. Closer to the eruption much higher waves were reported. Not everywhere: in the capital of Tonga, waves were a little over 1 meter. But other islands were hit by waves over 10 meters tall.

How high was the tsunami at Hunga Tonga itself? This is now estimated at 90 meters! No wonder so little survived. We were in fact very lucky that Hunga Tonga was in such an isolated location. Remember that on the island of Sebesi, 15 kilometers from Krakatau, everyone of the 3000 inhabitants perished. There were no survivors. This time, such a catastrophe was avoided purely by distance.


Records were set. The plume reached 58 kilometers, by far the highest every recorded. The explosive energy is the largest on record: even our very own Tsar bomb did not manage that. We have never seen such an amount of water in the stratosphere.

A more mundane but perhaps more impressive record: during the half an hour of the main eruption, half of all lighting on Earth occurred within this single eruption plume.

Bottom line

We were waiting for the next big volcanic eruption on Earth. We had it in 2021 – but it has taken a year to recognize this! There are typically 2-3 VEI-6 eruptions per century. In the 20th century we had Santa Maria, Novarupta and Pinatubo. In the 19th century there were Krakatoa, Tambora and the unknown volcano of 1808/9. And now we have Hunga Tonga to start off the list for the 21st century.

But there is a warning here. We had no idea how precarious a deep-ocean volcano could be. We have warned in the past about Iwo Jima (Ioto), the top entry on our proposed list of dangerous volcanoes. Reading Henrik’s post on this, it is striking how close his imagination came to Hunga Tonga. Unlike Iwo Jima, Hunga Tonga showed no sign of the impending events. How many others are there like it, waiting in the wings?

Albert, January 2023

Tranquility Base. Hunga Tonga (right) and Hunga Ha’apai (left), as seen by Sentinel on 22 January 2023: a peaceful scene of destruction

111 thoughts on “The Hunga Tonga eruption of 2022

  1. Really nice summary of a truly spectacular event. Imagine what tales an ancient mariner would tell about such an event 😉

  2. Excellent reprise, condensed review and summation. Many thanks.

  3. Will say anecdotally that this summer has been generally not as hot as I remember last year. Still 20+ C days but most nights are 10-15 sometimes even less, which is not usually the case.

    • Tasmania is a very oceanic location so should not be a place of extreme heat or cold along the coasts, but its large enough and tall enough that there Maybe some continetality in interior

      At latitude 43 to 40 in the South Ocean it should be very mild like New Zeeland or Western Europe and perhaps subtropical at the North coast

      Is it still possible with volcanism in tasmania ?

      • Theoretical climate is mild, but that doesnt take account of the terrain, Tasmania is basically everything atypical about Australia, not a flat spot in sight and it is at best grassy, and usually pretty green. There are seasons but all seasons can occur at any time of the year, it has snowed on the mountains nearby on Christmas in some years while other years it was almost 40 C the same date, and last year we got a 30C day in winter. Several times in the past two weeks there has been a daily temperature variation of over 20 C… 🙂

        Should also mention too, there is absolutely nothing whatsoever inbetween Australia and Antarctica, there is not even any seamounts, just abyssal 5 km deep ocean going right to the Antarctic Circle and the edge of the icesheet. Tasmania is closer to the equator than most of the Mediteranean, but is more like northern Europe in climate, the southern hemisphere has very different latidudinal climate to the northern hemisphere. I recall you live in the Lapland area of northern Sweden, presumably near to Finland. There are large parts of Antarctica that are still in the ice age while further from the south pole than you are from the north, that is how different it is 🙂

        No volcanism. I once played with the idea but that was under assumption the volcanism of east Australia was hotspot derived, it is much more random in reality so chances are it will be a long time before another eruption here. Chances are highly likely an eruption in the near future will be at a presently active location, but a new one would only have a 5% change to be in Tasmania anyway.

      • Yes the Huge Antartic Icesheet cools everything down in Sourthen Hemisphere plus the cold ocean around there.

        Even places like Kergulen at latitude 48 are near are polar climate Thats how dominant Antartica icesheet moderation are. Sourthen Hemisphere never really left the Ice Age I guess.. althrough Australia was colder and even much drier during the LGM.

        Sourthen Mediterranean sit at latitude 29 to 32 so defentivly Subtropical.

        Currently I live in South Sweden moved south, at latitude 59 it woud still be a polar climate in Antartica Ocean at those latitudes. Stockholm warmed by the Gulf Stream is similar to the very coolest interior parts of South New Zeeland with a warm summer

        Antartica Ocean lacks any large landmasses or warm seacurrents, to soak up the little summer heat that exist and thats why summers are so cold in that ocean

        Northen Europe and Euroasia are large landmasses that gets solar warmed and thats why we have warm summers at Arctic latitudes and the Gulf Stream keeps us mild in winter

    • Antartica Ocean like volcanic Heard and McDonalds Islands must be the most awful wet cold climate that you can ever imagine .. even worse than Iceland … the most bone chilling wet nasty cold year around .. only liked by raw rough fishermen

      Constant winds and freezing spray from the ocean and wet snow and a summer that may never reach +5 C even … and winters that sit at around – 8 C Thats a Marine Polar climate and its perhaps the worst type of all.

      Constant snow blizzards and freezing rainstorms this is an ideal place for a prison colony .. in that climate

      Thats so drearly and nasty that I woud rather die than be forced to live there for rest of my life

      • Antarticas interior is way way even more extreme .. But Thats a very dry cold also and No humidity that gets into your brain

        In general the Sourthen Ocean moderated by the Antartica Icesheet seems to be the worst type of all weathers bone chilling humidity … Im freezing just I think of heard Islands cold water .. and wind

      • It also ewokes the most dramatic imagery in my head
        A dark cold ocean under a dark gloomy overcast winter day sky .. but the Ice capped volcano rises up in the distance into the cloud layer and sunlight in a break shines down on the Islands Glacier … almost like biblical paitings ..

        The is is full of millions of seabirds and waves that can crush a ship

        Souch sights inspired the Early polar explorers during the Age of sail

        • Hi Jesper, this video of mine captures a bit of that imagery. It was shot at Deception Island when there was a fierce wind during most of the day (which prevented us making a landing on the beach to dig a jacuzzi with the heated ocean water from the volcano).
          In the late afternoon we went to an old whale ‘refinery’.
          The blueish color was the natural light. I think this was our coldest day ( Iwas lucky with plenty sunny days)

          It’s still a strange idea that we actually sailed and anchored in the crater of an active volcano.

          (a version with music is in the same playlist)

  4. If you look at the Kilauea KW webcam it is quite visible that the whole crater floor has lifted up a lot compared to the edges, even enough to start changing the shape of the western lake.
    Seems instead of flowing out all of the lava for the last weeks has been building up under the crater floor. There could be some proper lava action again soon when the crust cracks at the edge if this keeps up 🙂

    It is incredible to look at this and think about how that was a 400 meter deep pit with a lake at the bottom only a little over 2 years ago, and that pit itself is only 4.5 years old. What will it look like in 5 more years.

  5. Although not strictly correct, you could make a case for the HT paroxysm being a ‘mega-maar’…
    Be NOT There !!

    FWIW, that bathymetry reminded me of the Santorini caldera before ‘Nea’ popped up. IIRC, yachties would spend a week or two moored over the submerged ‘hot spring’, have a fun time ashore while the sulphur-rich plume briskly de-weeded their craft. Mind you, they had to remember to check their props, through-hull fittings and sacrificial anodes were still intact…

  6. Nice summary of the Hunga Tunga eruption. I wonder how many such eruptions occurred in the past…

    Anyways found this article about the formation of the Burmuda Islands here:
    Apparently, the islands formed from some kind of hotspot that is created by a disturbance of the so-called “transitional layer” between the upper and lower mantle. It is quite interesting…

    • I expect that eruptions like this are not uncommon but are very easy to miss. Maybe every other century, as a guess?

      • I suspect most have been missed. Isolated area with very low populations.
        We really have no idea of the frequency, we may have been living through a period where they were temporarily rare just by chance.
        It wouldn’t be a bad idea to sample any likely candidates to get a better feel.
        If this does turn out to have significant climatic effect then a sequence of these going off could have long term planetary climatic consequences.
        I cannot see any convincing mechanism for why an ice age should ever end as the two states, ice age/tropicalworld both seem to be fairly stable.
        Actually tropical world could sequester enough carbon to destroy itself as it may have done after the carbonaceous.

      • My guess is that, since you mentioned about the amount of water being released could warm up the world by a bit, maybe we could look for periods that are slightly warmer than usual. In that case, it causes a problem as it wouldn’t really show in ice cores (unless if it is really intense) as water vapor released by such eruption would turn to snow (with very minute amounts of sulfur dioxide). Maybe the only way is to look at historical documents from the past, but that would be very hard as it would be scattered and shattered, so it would be really hard to look for this kind of eruption other than the geological evidence left behind, which isn’t really reliable.

  7. Thank you, Albert! We await with anticipation NASA’s Olympic swimming pool measurements. Or the Met Office’s equivalent in yellow weather warnings…

  8. Wow the fountain is a lot taller now. Yesterday there were two fountains as a second one appeared to the right of the original, now that second fountain is huge, I cant remember seeing either fountain this tall since the eruption began. There is no weird deformation signal or earthquakes, what is causing this is a mystery to me, but it looks like there is a bit of a surge going on.

  9. I have updated the post with the results of another paper that has recently come out, with more detail on the cloud heights. The main new image is below. There is also a new video of a nice (from a safe distance) December explosion – almost nothing on this video still exists!

  10. Makes you wonder how dramatic an eruption at Ioto could potentially be.

  11. A common theme I see in articles about Hunga Tonga is that the eruption of hot material through ocean water results in a steam explosion. I very rarely see supercritical reservoirs discussed. Honestly I don’t see how the first scenario could supply the ‘boominess’ – there’s a limit on how fast the water can get heated up and turn into steam. Why don’t we see more discussion of supercritical water explosions as a mechanism for the gigantic booms of Krakatoa and Hunga Tonga?

    • Too tekky.
      Few understand heat, let alone latent heat let alone supercritical steam/water.
      To be honest it never occurred to me that steam could have a negative latent heat of evaporation. I’m tolerably tekky, too, and can see a hechanism.

  12. Auckland, NZ just had an amazing 10″+ 24hr rainstorm that killed several people along with causing massive damage.
    But this event wasn’t a oneofer…but rather another in a growing list of unusual weather events (in many cases way-exceeding records like in Auckland) in the Southern Hemisphere. Portions of Australia (Queensland, if I recall?) also saw record Spring storms as well as the coast of Chile.
    Given the temporal proximity to the Hunga Tonga eruption to this wild year of weather leads to an inescapable temptation to find some causative linkage. But, what that linkage is, and the physical processes that are involved are not at all clear.
    In general, it “appears” that the SH has seen overall cooling after the eruption (but that could change with more data), which seems counter-intuitive to the GHG theory of what aftereffects WV in the stratosphere should have on the troposphere.
    If the upper troposphere is warmed by GHG above, then that should enhance the inversion below the tropopause and promote a generally stable airmass…i.e. warming with less cyclonic activity.
    But, what about micro-droplets of water ice in the stratosphere? Maybe not enough to actually create clouds, but enough to create a light haze…and if there are ice crystals present, then insolar radiation would be reflected, hence a cooling of the troposphere. IMHO, both effects are likely in play, and it may be that in the short term more insolar heat is being reflected than being trapped….but the future, the WV will remain long after the microdroplets evaporate and the GHG effect will then dominate.
    Class is in session, fer sure.

    • It is probably something we cant draw a conclusion to for a while, the weird weather is something that was expected anyway on the climate trajectory so this might have just brought it forward a few years. We also dont know the affects of so much water in the upper atmosphere, only Krakatau among historical large eruptions probably did this all the others were entirely dry.

      Maybe there are NASA documents on it, I think they did study this field to look at water vapor in rocket and high altitude plane exhaust in the stratosphere and mesosphere.

    • It is hard to predict local weather from global changes. Weather patterns change and when one part warms, another may cool. Changes may also be seasonal. I don’t know what weather pattern causes summer rain storms in Auckland! What does La Nina do there? I understand that Antarctic sea ice was the lowest on record.

      • The Humboldt current/SPacific Gyre has been directing ultra warm water in the far western pacific poleward which is warming the Antarctic. The melt water in turn is being directed up the coast of S America by the gyre which is helping support the La Nina conditions over the equator.
        At the time of Hunga Tonga’s eruption, La Nina was in it’s 3rd year which in itself is very unusual…and most models and climatological history were predicating La Nina to be on the wane by 2023 (which is verifying).
        As a result, trying to sort out the effects of Hunga-Tonga from the effects of a waning La Nina that should be happening anyway will be problematic.
        But also note, that very rare polar stratospheric clouds have being reported over Scotland (and elsewhere) just in the last few days. ATTM, I’m not sure if the upper stratosphere is so cold or if there is enough WV to facilitate enough condensation to form clouds… but regardless, there sure is a lot a weird weather/climate going on worldwide. Here in California, we are finally getting some good rain and snow after a 3 yr. mega-drought…plus our average temperature has steadily been colder than it has been in decades. An interesting coincidence?

        • Many places in the northeast US had their warmest January or top 5 warmest on record, not to mention NYC broke their ‘first snow’ record of Jan 29th.

          Those of us on the east coast got head faked by the intense Greenland block in December; we thought we were about the see an epic, snowy winter. Then after the December cold shot (and that epic Great Lakes storm that deconstructed the block), we switched to torchy, mild Pacific air and the northeast cooked all month. Now the southeast ridge is returning for Feb and we’re cooking a different way after this coming cold shot.

          • It’s also odd that the January longwave pattern was reminiscent of a super Nino, several meteorologists were talking about how unusual it was. Now we’re getting more of a canonical Nina Feb in the east making a very good case for one of the worst winters ever here (if you like cold and snow, like me).

      • My view entirely.
        We simply do not have good models for planetary climate generally. Short term is quite good ~30 days maybe, modelling the entire atmosphere is far beyond us.
        Generally the best that can be said is that higher CO2 levels will result in ‘significant’ climatic modification. How significant and on what timescale is not known. More importantly there may well be significant new quasi-stable states we have not encountered very often before. These could be hugely damaging.

        Atmospheric rivers (see California) are normal. There was a long article on it a decade ago in scientific american. Not new, not frequent.

        In the mean time we have a megalomanic 21C hitler/napoleon/alexander/genghis trashing the world economy so he will be remembered as the saviour of russia.

      • La Nina causes rainy weather in northern NZ due to the higher incidence of north-easterly winds and moisture drawing down from the tropical and sub-tropical Pacific.

        This wasn’t an unusual event as far as Auckland weather patterns go, however, it was an especially wet one.

    • In 2022 we have had unusually high rainfall throughout the year which has caused the Orange River to remain a unusually high levels. Tha major dams on the Orange and Vaal rivers have had serious overflow events and the water flow over the Augrabies Falls peaking at over 3900cumecs, the highest since the 1980s. We also had devastating floods on the Natal coast which caused extensive damage to infrastructure. Seems the whole SH is being affected.

  13. Albert a question. Would it be possible to survive a fall from the Karman line with a parachute, or even up where the ISS is? Orbital re-entry gets so hot because of the energy of moving at orbital velocity, but if you fell straight down you have no sideways velocity at all. Perhaps this could be considered like base jumping off a space elevator 🙂

    Just something that I thought about looking at how high up the plume went and how the tallest base jump is still nowhere near this.

    • Then you needs to go up there without orbital speed and thats hard
      A parachute woud be indeed useful slowing down gently, not soure how to get 100 s of km up without orbit trajectories

      Spinning is leathal there without air flow to balance you.. needs a steady angle of jump

    • The problem is keeping your speed under control. There is very little atmosphere and parachutes won’t work. So you are effectively in free fall, and by the time a parachute does something, you are going too fast for it to survive. Say 1 to 2 km/s, very supersonic. You will get very hot once air friction begins. Stability is hard to maintain: you may start spinning at unsurvivable rates. Finally, when deceleration kicks in it may be well be at g-forces that are too high for you. I recommend bringing a capsule to protect yourself and wings for gliding. So if you do get a ride in virgin space, stay inside and don’t use the emergency exit. The soyuz launch that failed had astronauts without propulsion at 50 km. They dropped the rockets and stayed in the cabin. They did not quite reach the Karman line (about 90 km) in their trajectory. They survived.

      • So acceleration under gravity is high enough that heating is still significant without orbital velocity. I was aware of the lack of air meaning high terminal velocity but assumed the density gradient was gradual enough to not kill you with the g forces, but seems not.

        Jesper it is quite a trivial thing to get that high, just go up 100 km, only a small rocket is needed for that like the New Shepard or Virgin Galactic vehicles, I think even ameture rocketeers have made rockets that have gone above the Karman line before. Orbital rockets are massive because rocket fuel is relatively not very energy dense and lots of it is needed to get both itself and the payload that fast, they go up to about 15 km then mostly sideways more than up because most of their energy is to accelerate around the earth not away from it. Something in orbit where the ISS is has enough kinetic energy that it has equivalent energy density to 9x its weight in TNT if it hit something at full speed, is why anything bigger than a grain of sand is considered hazardous up there 🙂

        I think a small rocket powered by nuclear reactions probably would be orbital though, even single stage to orbit. But those will never be used while our biology is a factor.

        • At 100miles, gravity is still essentially 1G. So imagine falling 10 miles with no air resistance, you would be going pretty quick with significant potential energy. Lessee, 100kg person falling 10,000m at 10m/s^2 is 1MJ.or ~250kCal or 250cal/gm so you would heat up by ~250C
          Assuming I haven’t made a mistake, oughta check but …

      • Yes You right they woud be ripped apart I guess

        But perhaps the slowly increasing air density coud cause a chute to work ?

        I have always dreamt of parachuting into Jupiter jumping from the 0,01 bar level and falling down into the clouds below. Falling into a gas giant is stuff of nightmares really

        • Personally I would prefer a balloon for longer life expectancy.

          Personally I wonder if the seasonal colours shown by the jupiter rings are not a sign of life. After all the energy density isn’t so bad and there are many nutrients, but in the clouds. I’m not at all convinced that some earth bacteria could not survive.

          Now there is a scifi story where genetically engineered bugs are released onto jupiter and cause an atmospheric eco-catatrrophe!

  14. Thanks for an very interesting article, I live on Tongatapu and experienced this eruption, it truly was the most terrifying thing I have ever experienced. It’s good to get a better understanding of what happened. Mālō

    • You are very welcome! We would love to hear from your experience. You have been through something extaordinary

    • Is there an etymological connection between that “Mālō” and Hawaii’s “Mahalo”?

  15. Probably water played a role in the plume dynamics, maybe also in the generation of waves in the atmosphere. But to me the most important aspect of this eruption is that it was a caldera-forming ignimbrite eruption, Pinatubo was not, Novarupta was not, Krakatoa was, Tambora was, and Hunga Tonga was too. The size of submarine pyroclastic density currents generated during the Hunga Tonga eruption should be more than enough to place it this category:

    “Based on the relationships identified we propose that ignimbrites that originated from the collapse of single point-source eruption columns, usually smaller than 1 km3, are named “Vulcanian ignimbrites” and “Plinian ignimbrites” depending on the style of the eruption they are associated with. Larger ignimbrites that originated from caldera-forming eruptions along ring-fault fissure vents should be regarded as related to a separate eruption style – with respect to the common Hawaiian-Plinian trend -, where the effect of increased mass flow rate due to ring-fissure vents is dominant and controls the dynamics of the resulting collapsing fountains and pyroclastic flows, irrespective of the kind of eruption style that preceded the onset of the caldera collapse. These are named “caldera-forming ignimbrites” and are further subdivided into small, intermediate, large and super, based on their increasing erupted volume.”

    Caldera-forming ignimbrite eruptions can happen in any location as long as there is a major caldera collapse, you find them in the Altiplano-Puna, or the Sahara, and you also find them hundreds of meters underwater in the Tonga, or Izu-Bonin arcs. In this model Hunga Tonga would have erupted from a caldera fissure. So more than having to do with its location in the ocean, the violence of the Hunga Tonga eruption would have to do with the internal dynamics of the volcano, with the extremely high effusion rates of lava from a ring fissure system along the sides of the collapsing caldera.

    • It is interesting how the distance the flows go from the caldera is not really that different between Novarupta and Cerro Galan, despite there being a 100x difference in size. And that the flows from HTHH went as far as 100 km which is something that I was only aware could happen in the most extreme VEI 8s before, it might have been only a borderline 6 but probably had an intensity that matches the largest VEI 8s, those just have more magma to draw from. There might well be a larger or at least comparable eruption in volume in the next few decades but there is much less chance that it will be anywhere near as explosive. Really the only other thing we have a good record to compare this to is Krakatau which was 140 years ago, so really this is at best a once in a lifetime event statistically.

      And HTHH was neither a long dormant nor silicic volcano, actually from what I can gather it is the most active and most mafic of all the volcanoes in its immediate area… So ironically the criteria we use to find risky future calderas would have taken us nowhere near Hunga Tonga Hunga Ha’apai even if we were looking for it.

      • Even now, in hindsight, it is still difficult to understand what factors led to the caldera-forming ignimbrite eruption of Hunga Tonga. I guess we do not know the criteria very well.

        Hunga Tonga was clearly a caldera system though, it had circumferential fissure eruptions and an earlier caldera. It is also known that basaltic andesite caldera-forming ignimbrites are a thing, in fact a volcano near Hunga Tonga, Tofua, did a similar thing 1000 years ago to what Hunga Tonga has done. So it should have been expected Hunga Tonga had the potential to produce a basaltic-andesite caldera-forming ignimbrite eruption. Of course the exact timing of that could not have been foreseen. I guess the first clear precursor was the December explosive eruption, which showed the volcano was capable of reaching plinian intensity and there was a risk of caldera collapse if the eruptions kept building up in intensity, in fact the second major paroxysm seems to have been the immediate trigger of the caldera collapse. So if a caldera system does a powerful plinian eruption there is a chance of a caldera collapse happening within weeks, but of course it is tricky to know which volcanoes can be considered potential caldera systems.

        • Krakatau behaved in a similar way in 1883. Eruptive activity started in May and continued with several smaller eruptions throughout the summer. On August 25 the eruptions intensified and on August 26 it went into more or less continuous eruption which ended with four enormous explosions in the morning of August 27, the third one being the largest.

        • I mean, even if we know mafic volcanoes with ignimbrie calderas are a thing usually that is explained as some sort of transition with an evolved magma erupting out of an older mafic volcano. I think having Bardarbunga and Kilauea both make effusive calderas recently didnt help to sway that view. I am quite the thorough researcher of basaltic volcanism and I was totally on te wrong path with this, my idea was this was a passive collapse that decompressed some shallow gas rich magma or a hydrothermal system, or both, with a large effusive eruption in deeper water. But now the answer is undeniable.

          I wonder how many even rhyolitic calderas are actually dominated by that magma type too. A lot of ignimbrites have an evolving composition through time of emplacement, but are only a small part silicic. Maybe the best example is Ambrym, which has a dacitic component to its caldera forming eruption, but was by large majority basaltic and has almost not erupted anything else since (some andesite in 1986).

          Even some famous examples are like this. Crater Lake was rhyodacite that trended into andesite, which makes up a large percent if the volume, and crystal free andesite as found at caldera systems tends to be a much more fluid magma than the crystal rich stuff at some stratovolcanoes. In modern times Novarupta was dacite trending to andesite for the main ignimbrite, the rhyolite was afterwards. Granted the andesite at Trident nearby (probably the same stuff) is not very fluid looking but much more mobile than the stuff the Novarupta dome is made of. Seems there is a view that big calderas need viscous magma which is probably not correct at all,maybe to get a magma chamber the size of Toba without it erupting earlier yes but most calderas are way smaller and this wouldnt be a factor. If anything a fluid magma in an ignimbrite eruption would produce a much more powerful eruption all things equal, low viscosity means high flow rate. Basaltic effusive eruptions can already have effusion rates comparable to plinian eruptions and through dikes under 2 meters wide, imagine what would happen if the opening was 10-50x wider. Well, I dont think we need to imagine anymore…

          • Basaltic-andesite ignimbrites are relatively common in volcanic arcs, usually from magmas that are very fluid. Tofua, Yasur or Villarica are great examples, they all have produced caldera-forming ignimbrites with magma compositions similar to the one that they presently erupt. But I am still not aware of any basalt ignimbrites in or outside volcanic arcs, with the exception of one Krafla eruption that started with rhyolite and progressed into basalt. Ultramafic leucitite caldera-forming ignimbrites can happen at Colli Albani, which I wrote an article about, but of course these magmas are probably super gas rich and perhaps have less density than basalts due to their high sodium and potassium contents, and depletion of magnesium (although I’m not fully sure of how the density goes in such odd magmas). Given that Colli Albani eruptions probably have a very high fluidity, comparable to basalts, similar to recent Vesuvius lava flows of a similar composition, I don’t think fluidity is what limits the occurrence of true basalt ignimbrites, probably it has to do mainly with the high density of basalt that may limit an upward emptying of the magma chamber, and also maybe with the gas-poor nature of intraplate basalts.

  16. Etnas upper flank eruption continues and soon Etna will have a larger flank eruption, No doubt about that ..And farmlands Will be destroyed

    Etna had very frequent flank eruptions up to 1900 s after that its mostly been summit stuff
    But been crazy frequent with fast flank eruptions 1600 – 1910 sometimes every 3 to 4 th year. So No doubt that something will happen soon ..

  17. The upper Stratosphere is now <-85C, which explains the appearance of polar stratospheric clouds over the northern latitudes.
    Since the stratosphere is largely heated by ozone production created by UV from the sun reacting with O2 to create ozone plus a release of heat, then I wonder if the cooling could be related to a depletion of ozone?
    Given that water vapor destroys ozone, I wonder if the ozone depletion and resultant cooling of the polar stratosphere is a result of Hunga-Tonga injection of WV? Is this the missing link as to why the tropospheric weather patterns have been so chaotic since the eruption?
    Again, only time will tell, but an intriguing possibility.

    • Creating ozone from oxygen is endothermic, actually very endothermic as O3 on its own has about the same energy content as its weight in tnt, let alone if you mix it with something remotely oxidisable 🙂

      It is a powerful greenhouse gas though so that is probably why, but I havent done any numbers for this. So probably I am oversimplifying There is also nitrous oxide too, same deal except it is more stable. Also I guess just having such thin air probably makes it a lot easier to heat up too, less thermal mass.

  18. The discussion about the consequences of water vapor confuses me. The measurements show an extremely strong COLD anomaly beyond the eruption, even with a short heating, which is also logical: Greenhouse gases COOL the stratosphere (and heat the troposphere). Water vapor is a greenhouse gas.
    I absolutely don’t understand why people are talking about warming up the Strato and at the same time the Severe Weather article is linked, where the cold anomalies can be seen so clearly.
    In addition, the eruption took place in the SOUTHERN hemisphere and the monthly cold anomalies were clearly to be followed (Karsten Haustein – The water vapor has only recently spread slowly and only partially into the NORTH hemisphere (, so why should we have a cold winter, if the water vapor is not in our hemisphere at all???

    • In 2022 we have had unusually high rainfall throughout the year which has caused the Orange River to remain a unusually high levels. Tha major dams on the Orange and Vaal rivers have had serious overflow events and the water flow over the Augrabies Falls peaking at over 3900cumecs, the highest since the 1980s. We also had devastating floods on the Natal coast which caused extensive damage to infrastructure. Seems the whole SH is being affected.

    • The chemistry in the stratosphere varies considerably from the troposphere due to considerably lower pressures (orders of magnitude) and the number of disassociated ions.
      Ozone itself is only relatively stable (in the strat) and it would be more accurate to talk about processes rather than large stable sinks of ozone. Also, given the rarefied atmosphere and height, I don’t think ozone counts in the same manner as a greenhouse gas as, say, CO2 in the trop.
      As to whether there has been a large drop in ozone due to the process described by Craig, it is well monitored so this should become apparent.

      • Sorry this was supposed to be a reply to Craig and Chad above..internet connection dropped out.
        Michael Kleen.. completely agree. At this stage there are no known mechanisms, or certainly none have been seriously postulated

      • Ozone is actually a greenhouse gas but that is not its main effect. In the stratosphere it absorbs UV from the sun, and this heats the stratosphere. So the stratosphere is warmer than the top of the troposphere. It also absorbs and re-emits infrared radiation from the ground, and this acts as a greenhouse. Other gasses can have more than one affect depending on where they are. Sulphate in the stratosphere reflects sunlight and cools the earth. Sulphate in the lower troposphere warms the ground.

        • Sulfate is not a gas though, it is tiny solid particles. Not sure exactly but seems to be mostly Ca, Fe or MgSO4. It could also be frozen H2SO4. Learned that from Hawaii, the SO2 is oxidized in the atmosphere so is only really a hazard on Kilauea itself, the vog at Kona is particulates. Probably during major eruptions though the SO2 goes further, it got pretty far last December when Mauna Loa erupted. Not so much in 2018 but then that was underneath a self induced biblical flood storm so probably scrubbed itself.

          I think the vog from Laki over in Europe was particulates too. Sulfates tend to be very white and reflective so maybe that us why they are effective at cooling. SO2 can sort of be viewed as ozone but the middle oxygen is replaced by a sulfur atom, so it also very strongly absorbs UV.

        • ‘Ozone in the stratosphere is technically a greenhouse gas’ to quote the US EIAA but my point is that language is somewhat less precise in many ways than say physics and it’s importance as a greenhouse gas (relevant to anthropological GW) is minimal.
          Otherwise we will have conspiratorial types decrying our efforts to reduce CFCs!
          I know you understand the physics Albert. I’d encourage anyone interested in potential climate effects of volcanic eruptions (such as HTHH) to do as much research into current knowledge of the stratosphere as they can.

        • Ok, but why there are so many negative (cold) anomalies only in the southern stratosphere from the time of the eruption til today? Don’t tell me that’s a correlation and not causality. ^^ (seen in the severe weather article, Source: NOAA/Simon Lee).
          I’ve read (sorry don’t know the source anymore) that water vapor acts as a GHG in the stratosphere and cools it. Radiosondes has proven the decline of temperature in the stratosphere due to GHG since decades. A water vapor injection should do the same and results in negative anomalies as seen.
          Additionally Water Vapor in this case has the same effect as sulfur dioxid from vulcanic eruptions and cools the hemisphere, later the whole globe additionally. When Water Vapor is absorbing sunlight and heats up the stratosphere then why there are only cold anomalies and no heat anomalies seen in the strato??

          Only when water vapor sinks down into the troposphere the heat radiation from earth is trapped and reflected back to the ground so the troposphere is heating up.

  19. Great article! Regarding the last few sentences – some statistics of how many similar caldera systems are in the sea and how often they erupt would be super interesting. Would add some colour – in theory any eruption at a caldera system with water present could lead to water-magma interaction similar to what we saw here (maybe even bigger?).

    Obviously there is Taal that comes to mind, but many others too! Think VEI6 eruptions could be much more frequent than we would expect. The few 100 years we witnessed so far are not a strong reference in geological time frames. Records tend to get washed away when water is closeby..

  20. And still going on Mars, Ingenuity is now uphill from Perseverance and recently completed Flight 41 scouting ahead for Perseverance’s extended mission now that the primary set of sample tubes have been set down.


    Cheers to a successful Flight 41 🎉
    Ingenuity took to the Martian skies to provide an aerial view of the area for the
    @NASAPersevere team. The #MarsHelicopter’s out-and-back flight covered 600 feet (183 meters) in 109 seconds.

  21. One interesting thing looking at a sample size of two is that this kind of explosion may not really take long dormancies, which is a bit different. Like most of the VEI 5’s and 6’s of our lifetime will probably be from barely monitored volcanos who haven’t done much of anything in thousands of years. But for Krakatoa, Perboewatan had an eruption in 1680 and may have been a smaller, separate island earlier in the century. Of course this expansion may have been more of an ersatz version of Iwo Jima than an eruption per se. While Hunga Tonga had a major eruption about a thousand years ago and has had small eruptions for a while.

    I do wonder what Hunga Tonga’s long-term supply rate is. Like Iwo Jima must have one of the highest supply rates of any non-Kilueau volcano given its eruption around 700BC has been followed by massive, steady inflation. Like the math based on its inflation rate and the area effected suggests it is getting at least 0.5km^3 of magma a century (maybe even a full km^3 per century given the inflation may be bigger than the caldera given Suribachiyama is also going up and wouldn’t expect 100% of intrusion to be reflected in upward displacement). Given Hunga Tonga had a major eruption 900 years ago, does similarly have a huge supply or is just in a self-destructive mood at the moment?

    Now it is easy to say but it hasn’t been that active in the historical record, but is that actually true? Like the 2014-15 island-building was 0.048km^3 just for the part above sea level. Total volume above caldera floor is 0.5km^3, though I am not clear from the article if they know if that was 100% built in 2014-15: Then there was the 2009 eruption which was smaller, but still substantial. Plus 3 more eruptions that didn’t surface since 1900 although they probably were all much smaller. That’s in the ballpark of Iwo Jima, just in a different style. I think that southern platform that keeps getting mentioned is just the eroded remnant of past 2014-style eruptions, note that it is just below sea level, very similar to the 2009 island or what the 2014 one would have looked like in a few decades. So not an outer versus an inner caldera, just a partially filled caldera. Also the old caldera was pretty shallow. I wonder if it is possible that it was rather lower 900 years ago…

    • I’m wondering if Hunga Tonga might just be a smaller, faster-cycle version of Iwo Jima, which does have periodic very minor eruptions. Maybe Hunga Tonga had its eruption 900 years ago, fell quiet for a while, but a very large magma supply meant it rebounded fast, but its roof was much weaker than Iwo Jima’s so at some point it started having major leaks, and a couple largish eruptions formed the southern platform. Maybe Iwo Jima will have smaller failures before its cataclysmic VEI-6.

      This eruption may be a bit over the 900-year feed rate. Counting the southern platform and recent additions, close to 2km^3 of new material added since the last caldera eruption. Inflation since 1100 could be anywhere from a decent bit to only existing in my vivid imagination.

    • Yes, I think the southern platform indeed was just that, remnant of earlier in-fill. We will never know how old it was!

    • Regarding earlier activity of Hunga Tonga, the overall shape of the volcano is like a truncated stratovolcano with steep submarine slopes. So maybe before its first collapse it was a tall stratovolcano. Most other submarine Tongan volcanoes are enormous pyroclastic shields, with shallow slopes and extensive fields of concentric dune/ripple systems, such volcanoes probably were constructed mainly through high magnitude explosive eruptions. But Hunga Tonga is more like a stratovolcano in shape and must have formed though smaller scale effusive/explosive activity, later truncated by a caldera.

      The subaerial remnants of the volcano show a sequence of lavas overlain by 3 major explosive deposits, now 4, after 2022. The lavas might be from the stratovolcano stage maybe. Given all the explosive deposits seem to consist of ignimbrites and are very thick it is likely they are all caldera-forming events. So Hunga Tonga would have collapsed 3 times following its lava/stratovolcano stage and before its 2022 event. The earlier event, a massive welded andesite ignimbrite, dates to 1040-1180 CE. This makes a remarkably short interval of 900 years between its last two caldera forming eruptions. I also recall reading the one before had been around 2000 years ago, although I can’t pinpoint the source now. The activity of Hunga Tonga has probably recently changed from a stratovolcano with small scale activity to a caldera system that collapses every ~1000 years, making for a very interesting volcano. Source on the stratigraphy data:

      Apart from that, the detailed bathymetry of the volcano shows that the southern platform is older that the earlier caldera, given that it is cut by the collapse scarp (blue). But there were a lot of cones (green, with the craters marked in red) that could be younger that the last caldera-forming event. There is the largest cone of of 2014-2022 that might be polygenetic and might have had earlier activity. There were also numerous cones along the southern edge of volcanic platform, with some lava flows (orange). These cones were all blown away by the pyroclastic density currents of 2022, so they probably postdated the earlier equally powerful 1040-1180 CE ignimbrite event. As such, Hunga Tonga likely erupted many times from circumferential fissures in the southern sector of the volcano between the two last caldera forming events:

    • I mean 1 km3/century is probably not that far off what a lot of young and constantly active arc volcanoes do, though Ioto is not young, or constantly active, so that is notable.

      The 700 BCE Motoyama eruption was apparently not extremely large though, the caldera is a much older structure that perhaps has collapsed many times in similar events. That eruption too was not entirely explosive, it erupted welded tuff followed by large lava flows, then more tuff, for about 1 km3 of material. Doesnt mean it isnt dangerous or that future activity will not be bigger but there is a bit of a jump from that to a VEI 7. Lava is trachyte and trachyandesite, mostly the latter, so also not extremely evolved. If there is an eruption it might actually be more like the eruptions at Nishinoshima than a total instant self destruction, although probably of a rather higher intensity, could be quite a unique event really. But probably the article on the island for the New Decade Volcano list is thankfully a very unlikely scenario.

      There was maybe a small amount of lava erupted about 6 months ago. Inflation is also now very high, so it might be ready to go pretty soon.

      • The volcano north of Ioto, the North Ioto or Kita-Ioto volcano, is a prolific caldera system, with a 6 km wide caldera surrounded by a pyroclastic shield of pyroclastic density current covering a radius of 60-80 km all around the caldera. And it frequently produces large-magnitude ring fault earthquakes so might be undergoing rapid resurgence like Ioto. Kaitoku Seamount to the north of Kita Ioto has a 4 km caldera also surrounded by some thick extensive PDC deposits. Ioto might be an emergent caldera system that will develop into something like North Ioto or Kaitoku Seamount.

        This can be appreciated in Google Earth, or in the NOAA bathymetric data viewer when selecting the GRMT data synthesis.

      • Ioto has grown a lot in just over decade. I’ve compared the island outline in 2006 (orange) to an image of 2022 and it shows that a lot of new land has emerged above the waters. Considering the caldera is 10 km wide this is quite breath-taking. The coast has gained 700 meters to the ocean at places.

        Laguna del Maule in Chile also has some impressive inflation, publications put the amount of magma supplied to Laguna del Maule as 0.37 km3 during 2005-2020 as is still continuing steadily.

        • Alright, Iwo Jima has a bit of a hyper-inflation problem at the moment. Hector showed how much it has grown since 2011. I decided to compare to the satellite image from 2018: Here I mapped it: In places Iwo Jima has pushed back the ocean as much as 500 meters! Adding >2km^2 of land to the island! In just over 4 years!!!

          This doesn’t necessarily mean much though. The longterm average is only 0.25 meters of inflation per year, but it was already known that it can have times where that reaches as much as 1 meter per year (and conversely times when it is below that long-term average, like for much of the 1900s).

          • some of the expansion is movement of sand in the frequent typhones. But the rise of the land is real and it is getting faster in recent years

      • Kaitoku seamount is erupting now, or was recently. It is interesting there are so many of these pyroclastic shields in these arcs, they are rare on land and probably even rarer in the deep sea (perhaps impossible) but seem to be the majority of volcanoes along island arcs that are mostly submerged. Although, perhaps they are mostly submerged because the volcanoes dont grow up to form islands much… at the least though I would have expected to see a couple of terrestrial volcanoes that are calderas with massive ignimbrite shields formed by repeated eruptions but there arent any that really fit the bill. The only calderas on land that behave like this seem to be effusive, Kilauea being probably the most active and visible example but Bardarbunga and the Galapagos volcanoes being much more mature structures., their calderas are permanent and fundamental where those in Hawaii possibly are not. But regardless none of those do ignimbrites. Maybe being in water prevents the majority of the explosion, so submarine ignimbrites are basically just fast lava flows, and different in many ways to pyroclastic flows on land. So in that context, HTHH erupted 10 km3 of lava in less than an hour, it is not surprising it went so far from the volcano.

        I wonder if it is actually possible for one of the Galapagos calderas to do an ignimbrite. Or at least can they do a summit eruption that collapses the caldera, or is an explosive eruption required. The size of the summit eruptions at Sierra Negra are equivalent to VEI 5 plinian eruptions just not explosive, but these dont set off a real caldera collapse.

        • Could it be … rain?

          No, seriously. Ignimbrite shields might wash away fairly easily on land from rain erosion, which won’t happen to ones that formed underwater.

          Meanwhile, I have a troubling idea what may be happening with these “super-sharp exploders” like Krakatau and HTHH, which didn’t have a long repose before going bang.

          Supercritical or not, it’s generally agreed that the super-sharp explosions are basically giant boiler explosions, requiring a large amount of pressurized water to flash into steam to set them off; and that this requires confinement of the water — it can’t be hydraulically connected to the open ocean or it would just expand, flow away, and convect the heat away.

          This leads to the following proposed life cycle of these shallow-ocean caldera systems. First, you have something like Ioto. Then, it does a Tambora, but the geography and elevation are such that the resulting caldera is shallow-underwater, with perhaps a few islands poking up around the rim. That first caldera-forming event is an “ordinary” pelean-plinian VEI6-7 rather than a super-sharp bang ala Krakatoa.

          However, the aftermath of that event sees the rubble that collapsed into the former magma chamber being saturated with seawater. So we now have a large body of water at the right kind of depth to serve as the trigger for a sharp explosive eruption. All that remains is for it to get sealed in and pressurized. It’s already in a deep bowl, so all it needs is an impermeable lid to complete the process of boxing it up. The ring fault provides that by erupting degassed dregs of lava that can form a hard top above the water-bearing rubble layer.

          At some point, the activity of the rim volcanoes finishes the job of sealing in the water, and the water begins to pressurize, heated from below by fresh magma intruding from depth and trying to rebuild the pre-caldera magma chamber. On land, it will succeed and build a new cone eventually. In deep water it would do likewise, as the pressure would be too high for steam explosions. But in shallow water, the trapped watery-rubble lens becomes a pressure cooker without a safety valve. At this point the shallow submarine caldera is a ticking bomb.

          Either of two things can then set it off. Enough magma accumulating below may simply heat and pressurize the water-rich layer to the point of cracking the lid; or the lid can be destabilized. A big enough eruption from a rim cone deflating part of the magma chamber fast enough might do it, either by cracking the lid or directly by depressurizing the water enough to let it flash into steam. The other obvious option is shifting the weight distribution sitting on top of the lid, which HTHH’s 2014 cone and the subsequent 2022 activity will have done. Anything that faults the lid clear through and opens a path outward for water will set it off, once it’s become superheated while it was too pressurized to boil on the spot.

          That’s why the short repose times: it takes renewed activity to destabilize the water-bomb, and it does not take a large accumulation of gassy magma and/or the fractionation of a large volume of magma the way a “dry” explosive eruption does.

          This reinforces my earlier suggestion that all shallowly-submerged calderas be regarded as ticking bombs. I will note that this category includes Santorini and Campi Flegrei, putting large populations on Europe’s Mediterranean coast at risk. Renewed volcanism, even on a modest scale (e.g. VEI4 vulcanian activity on the caldera rims), should prompt an immediate large-scale evacuation, not only of a substantial radius about the volcano in question but also everywhere on the Mediterranean coast that’s at low enough elevation to be at risk if a Krakatoa-sized tsunami were to initiate at its position — from Algeciras to Rome to Istanbul to Alexandria and clear around to Tangier.

          • I did think about rain, but then stratovolcanoes abd pyroclastic cones stay pretty obvious in the landscape for a long time and should be more susceptible. At least, if there was an active ignimbrite shield on land that did eruptions of large scale every 1000 years or so it would be pretty obvious in the landscape still. Even every 3000 years probably would be enough.

            But more what I mean is all the calderas on land I am aware of which do large eruptions on the regular are completely effusive, there isnt any ignimbrite shields that erupt often. There is Ambrym and Masaya, and possibly Taal, but those dont do big eruptions often they just have open vents regularly, different sort of volcanism. And all of those would be normal shields regardless with their fluid magma.

            The closest thing I can think of with a mostly explosive caldera that does resurgence and frequent eruptions is maybe Grimsvotn, but eruptions there generally are far too small to really count and nothing is ignimbrite. The only two calderas on land that do predictable ring fault quakes with resurgence that builds to actually large eruptions are Sierra Negra and Bardarbunga, really just the latter with all the signs. I think maybe Askja could fit this now, its inflation is as fast as at Ioto, but it might also be just a sill which is a different sort of thing to real caldera resurgence. And Askja is not an ignimbrite caldera either. There are quite a few more calderas underwater that show active inflation evidence by the ring fault quakes, Hector has more info but I recall there are at least 5 that do this which is much more than on land.

          • There are a lot of submarine pyroclastic shields in the Izu-Bonin-Mariana, Tonga-Kermadec, and South Sandwich volcanic arcs, sometimes forming spectacular continuous fields of underwater ignimbrites and calderas. All five recurrent ring faulting subduction zone volcanoes of the past few decades are in these three volcanic arcs too. So I do think caldera activity is particularly intense in those three oceanic arcs.

            But it is also true that there are many pyroclastic shields that are subaerial too, like Ijen, Tondano, Aso, Kutcharo, Gorely, Okmok, Valles, Ilopango, or Okataina, to name a few. Broad edifices made largely of voluminous pyroclastic falls, ignimbrites, sometimes interbedded with lava flows. For example, Ilopango has produced 7 caldera-forming ignimbrites in the past 1 million years that have been well into VEI 6 territory, or even VEI-7. And in Alaska, the volcanoes Okmok, Aniakchak, and Veniaminof, have each caldera collapsed twice with ignimbrites during the Holocene, and probably additional times during the late Pleistocene. Okmok is almost continuously inflating. And Aniakchak produces bimodal dacite-andesite explosive eruptions from circumferential vents, which surely one day of these will go full ignimbrite mode. So there are also a number of impressive subaerial caldera systems that collapse recurrently, sometimes at intervals of only a few thousand years.

          • Thank you for the fine analysis
            Another satellite observation found steam above the 100km limit.
            But has anyone mentioned what happened to the salt? Or has only steam been sent to the stratosphere?

          • Salt is not volatile so will not become a vapour. It will stay behind. Even it if were to move up in the plume, it is heavier than water so will drop down faster.

      • It probably isn’t doing a VEI 7, but something big is coming. As I mentioned, the inflation includes Suribachiyama on the edge of the caldera, so likely the whole top is pushed up. My rough math is that there has been roughly 20km^3 of inflation since the last eruption, extrapolating backward inflation patterns in recorded times. Decent margin of error on that of course, but not enough to change the number being in the VEI 6 range given it is DRE if it goes caldera again. Not VEI 7, though it might get close to that volume given another 1000 years before bursting. That is of course assuming it limits itself to what has been added since the last big eruption.

  22. If you look at the sea floor on Google Earth or even Google maps, you see dozens and dozens of seamount calderas. Maybe hundreds, and often they are next door to other large seamounts without calderas.

    How old are they? For the most part we don’t know.

  23. The big lava lake at Kilauea has drained out,only a small part of it still has active lava. There was a DI event but the tilt and GPS are both showing longer term drop since the eruption resumed.

    Also at Pu’u O’o, the rift isnt contracting anymore, it hasnt reversed to inflation but it looks like at least pressure is being applied in that direction again. The lake is about 900 meters above sea level which is where the floor of Halemaumau was in the 50s and 60s when the ERZ became active. So the lake need not necessarily reach where it was in 2018.

    At the same time though the GPS hasnt fallen even 1/4 the distance the volcano has inflated in the past 4 months so this might just be an extreme reaction to a DI event.

  24. There is this strange thing I thought recently. Hunga Tunga’s explosions were pretty much caused by the depressurization of the water once trapped at or near the magma chamber. So, I was pretty much thinking and wondered “does this only apply to volcanoes in oceans (in the case of Hunga Tonga 2022 and Kratatau in 1883… maybe?) and lakes (Taupo in 250 AD?), or can it occur elsewhere?” and thought of glaciers.

    The case in point is, could an eruption similar to Hunga Tunga occur in Iceland? I mean, some of the ingredients there are set for such an event, right? The thing is that Iceland is too active for that and that the rock would weaken easily or the magma chambers too deep, or perhaps the water just escapes too quickly, or the ice is too thick. Katla is the closest subject, but even Katla doesn’t really have all the ingredients for such an eruption… could it? (Or am I just crazy enough to think that a glacier-covered volcano has the slimmest of chances to produce a hyper-pheatoplinian eruption, who knows…)

    • Then, again, it could be possible. I could maybe imagine a glacial lake forming during an big eruption, with some of the water draining through jökulhlaups, alleviating the pressure a bit, with the volcano already hydrothermically active before the eruption and, with decreasing pressure, the water turns into steam and goes boom, creating a very loud explosion, though perhaps that might be impossible for a few reasons and hopefully may never happen…

    • Depends on what the real mechanism behind the eruption is. Carl and Albert attribute a large role water had to play, while Hector’s proposal is that being in the ocean was not really important abd the eruption would be the same anyway, that all ignimbrite caldera collapses are like this. My more amature hypothesis is that it is a bit if both, it is hard to imagine there being no water involved especially with the massive plume being mostly water vapor, but that also shows most of the erupted magma stayed low down and went down the sides of the volcano not up, which is an ignimbrite.

      Ignimbrite calderas need an active ring fault, in Iceland only Bardarbunga has this, to my knowledge Katla doesnt, and Grimsvotn is not complete. But the other problem is plume basalt is gas poor and also dense so it is very unlikely to erupt up instead of going into a rift. Katla probably has high enough gas content to do this, but as said its caldera seems to be inactive, all the eruptions are within the pit not following the edge.

      In the future, when Hekla is a lot bigger and has a shallow magma chamber though, I would expect it to be capable of an ignimbrite. But not yet, unless it goes to sleep for 1000 years again.

      • Theoretically then do ignimbrite eruptions have less climate impact vs a more traditional large plinian eruption? I could see co-ignimbrite plumes still lofting a lot of particulate matter pretty high up regardless, but that’s got to be less efficient than a high energy direct injection of material from a plinian blast, no?

        • Typical plinian eruptions rarely go beyond a low end VEI-6 in terms of volume, so most eruptions with a strong climate impact that have larger volumes are ignimbrites, or involve some ignimbrite phase. Co-ignimbrite plumes are as high, if not higher, than plinian plumes. But maybe it is true that less sulphur dioxide will be injected into the stratosphere.

  25. With all this talk of ignimbrite eruptions and the dynamics at play it is interesting to think about what those eruptions would be like under different conditions. What would an ignimbrite look like on Venus where the pressure is too high for the volatiles to expand, would it just erupt as a really fast lava flow?

    Or on Io, there is not really any atmosphere so would the eruptions be more violent or does it also just erupt as a really fast lava flow. Maybe some of the big eruptions on Io that look like hawaiian type eruptions would have been ignimbrites under terrestrial conditions.

    It is probably better to think of ignimbrite flows as their own phenomenon, they are probably more if a real ‘liquid’ like a lava flow but erupt so fast they degas explosively outside the volcano to generate the secondary ash plumes that pyroclastic flows make. What most pyroclastic flows are in media, those from peleean eruptions or plinian column collapse, probably should be called a glowing avalanche as was the original term used. Or perhaps the term ignimbrite should only apply to welded ignimbrite and not just to any ash deposit that isnt fallout.

    I can picture, that after major ignimbrites the deposit is still hot enough to flow, in more mafic examples this might even generate some significant secondary lava flows.

    • On Io the lack of a dense atmosphere and the low gravity should make volcanic eruptions more violent. However, I suspect that Io has been erupting for a long enough time that its magma has been thoroughly degassed and not explosive. The original material that formed Io must have had water and other gases; so the earliest eruptions were probably quite spectacular.

    • The gas in Ionian basaltic magmas are sulfur and the volatile budget in Ionian magmas gets recycled as sulfur snow and lava basaltic layers pile on top and gets buried and melt again in the inner magma ocean.

  26. East Epi submarine volcano in Vanuatu currently erupting. Can’t find much information on it but described as large caldera off the coast of Epi Island. Previously erupted in 1920 & 1953.

    Also found an interesting article stating that the Earth’s inner core may have changed rotation direction in 2009.

  27. This is how small the smallest Ultracool Red Dwarf Star is compared to Saturn. EBLM J0555-57Ab is one of the smallest Red Dwarfs ever seen.

    Its small size and knowing its 80 times more massive than Jupiter in a volume smaller than Jupiter says alot just how incredibley insanely dense these small stars are. EBLM J0555-57Ab barely upheld by its weak fusion, have an avarge density many many times higher than the metal Osmium, yet its a gas plasma. Its Photosphere is cool enough for clouds of sillicates/ metals to condense

    These tiny M Dwarfs can live as long as 20 trillion years .. thats 10 000 times longer than the current Age of the universe…

    • So in a few tens of trillions of years in the Milky Ways future when there is only a few dying red dwarfs remaining, any remaining civilizations, realising that the end is near, will have wars over who have the right to clain the last stars…. pretty gloomy

      But best to move this to VC Bar

    • Hi Albert … knowing that thing is so very densely packed even at the photosphere levels, woud I sink into that gas If I fell into that ? Knowing its incredible dense.. or woud I be floating in the plasma medium?

      In our much less dense Sun.. bloated up by its faster fusion .. I woud sink

      • Of course you would be incinerated instantly. But having said that, If you somehow would be able to survive, you would float, like a little bird!

  28. Thanks Albert for pulling together such a great story. I knew of HTHH from the excellent rooster tails in 2009 which I recall made it into the media at the time.

    The parallels with Krakatau of 1883 are really interesting. My thought is this sort of extremely short explosive eruption is due to a volcano very close to the surface of the ocean. The initial eruptions clear the throat so that new magma rises via the reduction in pressure, then suddenly the crater walls breach just as that magma really gets going up the conduit. Sea water meeting lava going in opposite direction equals the biggest steam cannon on Earth.

    Krakatau was just like that. The eruption cleared the top off the volcano, water poured in then there were four titanic explosions one after another as the sea water vaporized and blew out, after which a new volume flooded in. Until the pluton had been pretty much ejected and there wasn’t much more energy left. The P wave trace for HTHH looks very like that with three or four ingresses/phreatomagmatic outbursts, then that’s mostly it, the new magma injection has gone up the stack.

    Which brings me to the question I was going to ask, which is does this always have to be an above sea level volcano that erupts the top off itself so that it then is below sea level that the ocean can flood in?

    I can’t recall a seamount eruption which has had the same short catastrophic explosivity. I suspect there’s too much cooling effect from ongoing seawater evaporation for one to get so hugely explosive – instead they stay in a sort of pot boiling state rather than exploding like Hunga Tonga did.

    Are there any cases of fully submarine Krakatau type eruptions?

  29. Been looking at Kilaueas lava lakes, and thinking about the way ignimbrite calderas seem to behave, there are a lot of similarities in the behavior.

    The crater floor of Halemaumau today started as a surface lava lake but now the crust is thick enough that I think it is probably better to think of it as a very shallow magma chamber. When the eruption began in January pressure under the crust was able to create a 50+ meter fountain at the vent, if it was thin the crust probably would have just broken up. After the Kilauea Iki lava lake stopped filling the crust was 6 meters thick after a year, and 13 meters thick in December 1962 which was 3 years later. So likely todays lake is somewhere around 10-15 meters thick too and perhaps quite a lot more locally under the island. Barring a major flank eruption draining all of the lava the crater floor is unlikely to founder and if anything will just get proportionally thicker.

    The lake that existed in the early 19th century stayed at about the situation we see today, but that lake was a lot larger in volume too, probably over 1 km3 at times, which is 8x what is there now and a lot larger in overall area. Today the actual core of the lake that is liquid might only be the part that is within the visible circular faults on the crater floor. This structure could be considered analogous to a ring fault of a large caldera, with the endogenous uplift being like resurgence.
    Perhaps in the future Kilaueas summit will be a large shield again but instead of a wide pit with a lava lake it will be kind of like a minaiature Galapagos caldera, flat top with some glowing spatter cones or lava lakes and occasional gushes of lava down the flanks from the ring faults, a sort of crusted over conduit. This is what Pu’u O’o kind of was in the 2000s. Maybe this is what the Observatory and Aila’au shields were too, after all those lasted for many decades possibly over a century, and at least the Observatory shield seems to have been surfaced over in channelized fast flows in the summit area west of HVO. In the Pele-Hi’iaka story there is reference to a place called Kalua Pele, today HVO gives the modern caldera floor that name but back then it seems to refer to the summit crater before the caldera formed, a large pit crater maybe similar to Halemaumau before 2018 but not a caldera. It might have been created by the fissure eruption that made Cone Peak to the southwest, probably not too long before the real caldera collapse the story describes.

    Another thing I have been looking at are the pyroclastic deposits around Kilauea from before the last summit overflows, during the period from 2500 to 1000 years ago, to make the U’ekahuna tephra. These were massive eruptions, pyroclastic flow deposits are exposed in the side of the pit craters on the ERZ, and as far as 15 km to the northeast and 200 meters up the side of Mauna Loa on the available maps. While not exactly large compared to something like Hunga Tonga or Krakatau this is still massive, the 1790 deposits are tiny in comparison. Not exactly suggesting this is certainly in our near future but the U’ekahuna series lasted over 1000 years inbetween known summit overflows. It has been ‘only’ 500 years since the summit overflowed, and without the historical period we would never know about any of the filling that has taken place since 1790, only the 1924 and 2018 ash, which would be interpreted as deep caldera collapse. So if a caldera collapse happens then Kilauea could become a Hunga Tonga, a small one but that doesnt matter if you are 3 km away…

    Caldera collapses seem to happen at Kilauea every 150 years or so since 1500, there was a collapse around that year, then in about 1650, then 1790. The 1924 eruption was probably a failed attempt, if Kilauea was dominant of the plume it likely would have been much larger and become a deep caldera again. It has now been about 100 years since 1924, so another caldera collapse like that of 1790 seems a likely event in the next 50 years, 2018 was not that event despite the size, the real calderas are much larger. At least on a very rough basis each caldera in the past 500 years looks like it has had a more violent formation, the 1500 and 1650 events had massive but still not really explosive lava fountains from the ring faults, probably similar to the fountain of Etna. 1790 though had a full plinian phase to a VEI 4 and directed base surges, only later going to fountaining. Given the scale of the older deposits the Uwekahuna eruptions might go into the VEI 5 range, the next collapse might be potentially like this too. This process might be somewhat randomly sequential and mean nothing really but it could also be seen as Kilauea forming a ring fault that gets progressively more developed with each collapse, eventually it may complete and end up with capabilities to do a much more powerful eruption.

  30. Looking at the Kilauea obs and cams this evening, the lake depth has just taken a sudden dip amounting to a day or two of accumulated depth, and there’s a new bright pond/edge/hotspot on the north edge of the crater. If that’s spilling out from under an uplifted, crusted-over shell, it’s making a good display of it!

    • New breakout, and I guess the lake has withdrawn as the pressure decreases. The edge of the lake has hardly gone up at all since the eruption started while wherever the laser is pointed has gone up 20 meters or something, so the middle is pushed up a lot compared to the edges. The laser is probably still pointed at the western lake as HVO never mentioned a change.

      Probably this will be the first of many breakouts in this area, filling up to overflow the ledge to the northeast 🙂

        • I’d really be interested to see a set of cross-section profiles of the lakes and crater floor. The single depth measurement is interesting, but not quite enough detail to get a proper idea of what’s going on with the proto-shield(s?) that seem to be building… especially without knowing exactly what the rangefinder is pointing at.
          The livestream is great, but being zoomed in means the interesting breakouts round the edges are out of shot!
          Hopefully all the high-res data is also being collected and will show up in a publication sometime soon, even if it can’t be streamed for those of us being amateur observers

          • I mean apart from 10 meters o the top and maybe 5 meters of the edges (maybe a bit more, but not a lot still) the crater is just lava. I have seen some speculation it could be viscous lava but the lava is such a poor conductor if heat it probably doesnt cool down really at all unless it is right near the edge, or even directly in contact with the edge. It seems from study of Kilauea Iki and Makaopuhi lava lakes that they solidify by crashing out crystals, the last lava to solidify is as silicic as andesite. But because the lake today is continuously fed this cant happen, it is probably all basically as hot as when it formed.

            So boring answer but it is liquid lava for 350 something meters, although it does look like there are some proper shields building which is going to be interesting as things go on 🙂

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