The eruption at 14th of January. Picture borrowed from Stuff.co.nz.
As the numbers for the Hunga Tonga eruption continues to come in it is becoming ever clearer that something truly momentous happened, something not seen or heard in 139 years.
With a columnar height of 55 kilometres, an explosive pressure wave travelling several laps around the planet, forming a medium sized deadly tsunami, gouging out a few cubic kilometres of rock, ash and silt, and so on and so forth it was to all points and purposes quite something.
Problem is that when we compare this eruption to a more common caldera forming event like for instance Pinatubo, we do not get the numbers to ad up. With such an enormous eruption column we should see very high amounts of SO2, and we should see a lot more erupted material.
The explosion does not seem to add up to the eruption. We need to figure out how such a comparatively small eruption could create such an over-sized explosion.
Judging from early satellite pictures we can estimate the eruption to have been between a mid-sized VEI-5, up to a miniscule VEI-6. So, we are back to 1991 and between Cerro Hudson and Pinatubo. So, the eruption is only small if we compare it to the explosion itself, in any other way it is the largest eruption in 31 years.
As explosions go it was the largest explosion witnessed by humans. Now remember that we are talking about the “boom” and not the eruption, humanity have witnessed quite a few larger eruptions.
Prior to Hunga Tonga the second largest explosion witnessed by humans was Krakatau in 1883, it has been estimated to have been between 20 and 30 megatons of TNT-equivalent.
It took the machinations of Beria, the insanity of Stalin, and the bizarre genius of Sakharov, but it in the early morning of the 30th of October of 1961 an enhanced Sluika with the project number AN602 was detonated with a yield of 50 megaton of TNT-equivalent.
The world named it the Tsar Bomba, and humanity for a brief moment in time grew a brain and stopped that particular direction of the atomic race.
Problem is that Nature is not that easily out staged. It was at that time busily priming a small non-descript volcanic caldera in the Kingdom of Tonga, named after the two small and equally non-descript caldera-rim islands, Hunga Tonga and Hunga Ha’apai.
After a bit of ever more impressive volcanic activity Nature was ready for the main show, and on the 15th of January it was showtime. Judging from audio tapes the main eruption was best counted in seconds, and in those few seconds Nature delivered an explosion in the range of 55 to 60 megatons of TNT-equivalent.
Incidentally, as I was writing this article the agency tasked with judging sizes of Nuclear Explosions just issued their calculations. It turns out I was spot on with my number of 55 to 60 megatons of TNT-equivalent. Just to be clear, I calculated this number on the 16th using barometric pressure readings, having confirmation of not being a “loon” is though always nice. Insert your favourite personal snicker sound here…
All we are left with are two miniscule remnants of the original islands, a gouged-out caldera, and a load of questions.
I will here try to answer two of them, and they are intimately inter-connected. Where did the SO2 go? And, what in the name of heck caused the explosion?
The missing SO2
The SO2 dispersion cloud from Hunga Tonga. Image borrowed from Newstalk.
This part is fairly easy to answer, and it has a profound effect on the second question. SO2 is a volcanic gas emitted from volcanoes together with fresh lava. Old lava contains comparatively little SO2 since almost all of it is transformed into all sorts of organic and non-organic sulphuric compounds, and those do not readily transform back into SO2 if lofted skywards.
We know that during the explosion a bulk portion of the bottom of the caldera decided to go and watch the movie The Adventures of Priscilla, Queen of the Desert at location in Australia.
In other words, it was a mixture of volcanic rock, old ash, old tephra, old pumice, and silt, that was exploded outwards, and that very little of fresh material was exploded skywards. And with little fresh material we get little SO2.
The Eruption Purist Interlude
There is a particular brand of stupid that now will start to argue that it was then a very small eruption, a VEI-2 or a VEI-3.
They will now categorically claim that the definition of every conceivable eruption scale is the amount of fresh material erupted.
I invite them to go and stand at a VEI-3 safe distance from the next Krakatau style eruption. Arguing pointless semantics is not your friend around volcanoes if you wish to remain alive.
The rest of us are probably happy with the total amount of ejecta, and the implications that have on life expectancy. So, let us move on to the main question. At least I am positively wet from anticipation by now.
The Other Volcanic Fluid
Water in two forms I do not like. Ice and cold water. This is the Thwaite Glacier, aka. the Doomsday Glacier, it will be quite gone in 5 years time. Image borrowed from the Rolling Stone Magazine.
Most of our readers are familiar with the term “volcanic fluids”, but I should explain it the same. It is a term often used by volcanologists as they describe any unknown fluid inside of a volcano. Often in relation to inflation or deflation of various sections of very large calderas.
The fluid could be magma, water, molten sulphur, and so on. Basically, anything that is fluid enough to move around causing changes in a volcano, either by intrusion, or by being pressured into a new area.
In large dying calderas like Yellowstone this would be counted in as little as an inch or two over a year. But, in other livelier calderas it could be counted in metres in just a day or two. The latter holds true for calderas like Amatitlán, Campi Flegrei, and Tondano, just to name a few.
Typically, both laypeople and volcanologists are way more interested in the potential for magma movement, after all, that is what we perceive as the dangerous version of volcanic fluids. Turns out we may have been quite wrong about this.
Up until now the only type of volcanologist being arse bothered with the water part was geothermal volcanologists, and we are far and few in between.
So, to understand things we need to study water for a while.
Don’t tickle when wet
Water is an amazing and life-giving fluid existing in a surprising number of different forms. Let us get more intimate with those forms.
First of these forms we have the whisky cube form known as ice. The only version I like is the ice cubes in a drink, I come from Northern Sweden, and we hate Ice in all other forms. It has a magical property, and that is that it takes up a larger volume in frozen form and is thus lighter than water. This is why it is floating on top of lakes.
This is important to people from Northern Sweden since it makes it possible to drill holes in the ice to fish. It is a very miserable and cold version of fishing. It also gives us the opportunity to drive around on top of lakes with building material where there are no normal roads.
Then we have normal water existing between 0 and 100 degrees if we are at oceanic altitudes. We drink it, swim in it, drown in it, use it to cook, and so on. Most people use it to make coffee or tea. It is more often beneficial than not.
Above 100 degrees Celsius (there is probably some weird Imperial number for this that I do not know, and am to lazy to google) we enter the realm of steam. Victorians with impressively high hats understood steam, most of the rest of humanity do not. So, let us don a very high hat and barge onwards into our steamy business.
Isambard Kingdom Brunel with impressive hat, he understood steam well. Wikimedia Commons.
As your teakettle starts to boil you will see white stuff start to waft around, most people think this white stuff is steam. Alas, it is not. It is tiny water droplets that are suspended in the air. They form as the surface turns 100C and steam forms to instantly cool below 100C and the droplets form. The steam-layer is literally one molecule thick top-layer of water, so you will not be able to see it.
It is though amply possible to hurt yourself with your white fluffy wispy stuff. But, to get steam we need to raise the temperature beyond 100 degrees Celsius.
To go beyond we need to ad another force, more heat does not cut it, that would just produce more low energy suspended water droplets at a faster pace. We need to insert pressure into our equation.
Water is funny, it will boil at different temperatures depending on your elevation, this is due to the pressure dropping the higher we go giving us lower and lower temperatures for when the water droplets will form what we call “steam”.
If we instead increase the pressure, we well and truly reach into the realm of flash steam. This is any temperature between above 100 and 184 degrees. In the latter case we need a pressure of 10 Bar (atmospheric pressures, the atmospheric pressure is really 1.01325 Bar, but close enough). This is the same pressure you would find at 100 metres depth of water.
Now imagine being that 184 degrees Celsius pressurised water, as long as you are at or above this pressure you are water, but if you even drop a tiny amount below this pressure, you will instantly flash from 1 litre of water into 2100 litres of suspended water droplets. But if you are contained in a volume less than 2100 litres you will stay in true steam form above 100C.
If you are above that temperature you will get something called dry steam, it is an invisible mess of hotness. It is steam kept at high temperature and pressure, but below the flashover point.
Now, remember the poignant word for us is flashover, this is the point where any amount of water will explosively decompress from water into steam.
There is though one step up from this on the giggly tree of water. It is called Supercritical Fluid. It is water that is at such a high temperature and pressure that it simultaneously behaves as a fluid and a gas, while being neither of those things.
If pressure has the upper hand, it is behaving more like a fluid, and if temperature has the upper hand, it behaves more like a gas.
Steam and water up to this point has been manageable, you obviously need to treat it carefully, but you can safely build systems to power ships, steam locomotives, and all power generation plants with it.
Well, the safely part is not true. Those high hated Victorians literally blew up tens of thousands of workers during the industrial revolution before they mastered their craft, ho-hum history is fun.
Water in supercritical form is the suicidal psychotic giggling version of water, it not only wishes to not exist, but it at the same time also wants to take everyone with it in a big boom. If that was not enough, it likes to go through solids like they where made out of paper. It is also very good at dissolving solids. You need specialised materials to even contain it.
So, you want numbers on this branch of the giggly tree? Supercritical water forms at minimum of 373 degrees Celsius and 220 Bars of pressure. Yes, this is the minimum, in some volcanic systems the Supercritical water can be up towards 800 degrees with corresponding mind-numbing pressure values.
This is the only form of water that could have caused the explosion at Hunga Tonga. There may have been other more normal forms of water involved, but they lack the energy density to produce that kind of explosion.
Incidentally, 220 Bars of pressure is reached at less than 1 kilometre’s depth if we use the specific density of bog standard rock (2.3kg per litre of volume, it is probably something in Imperial that is really hard to calculate).
What was down there?
Hunga Tonga becoming Hunga Byebye. Image from Himawari-8.
If you are like me, you will often and fondly imagine that you are a piece of drill steel being drilled into a volcano. It is not as bizarre as it may sound, after all my daytime job is to plan how to best drill into volcanoes for geothermal fluids to drive geothermal power plants with.
Even though we do not exactly know how Hunga Tonga’s geothermal system looked like, we know a lot about geothermal volcanic systems in general. After all, people have been drilling into them for quite some time.
Most often the drilling has been down into more normal forms of geothermal water. But, at times we have found Supercritical water down there.
A caldera is most often a closed off geothermal ecosystem. At the border of an active caldera, you often have an active ringfault, the inner side of it is often filled with material that is easily permeable to water, while the outside tends to be more sturdy.
Int the case of Hunga Tonga this geothermal ecosystem had a free and endless supply of surface water in the form of the Pacific Ocean. And over time that water slowly permeated down through the crushed up rock that constitutes the roof of the magma chamber.
As it went down it heated up and started to pool in layers (geothermal aquifers) depending on pressure and temperature. The upper ones would be the flash steam portion, but that is not as such interesting to us.
We are mainly interested in the water that climbed up the giggly tree hellbent on throwing itself down, aiming to hit every single branch, in other words let us stick to the Supercritical water.
There was probably one such supercritical layer slightly below 1000 meters depth. This would have been the prime driver of this layered volcanic cake (Sluika = Layered cake in Russian, just another hilarious detail).
Below that there was at least another layer of even hotter and more pressurised supercritical water. There is circumstantial evidence of a third such layer, so let us say that there was 2 to 3 supercritical geothermal layers inside the caldera.
These layers often move about upwards and downwards as they go, and the water is circulating around in them in unexpected and intricate ways.
At older more mature calderas like Yellowstone the supercritical water will find ways upwards with time, and they form some of the more spectacular features like geysers, hot pools, and all the other assorted geothermal joys in life.
Hunga Tonga was young and probably had not had time to become a truly circulating geothermal system. Well, not as far as we know that is.
As long as there was no eruption the supercritical water was happy where it was, it was of course trying to run away to the surface, but it seems like it was very slow going. And that was a good thing since there seems to have been 0.5 cubic kilometres of giggling hell-water down there.
The recipe for doom
The reason that these explosions are rare is because you need a large eruption to kickstart them. A normal eruption will just punch a hole straight through the aquifer with the lava quenching the hole as it passes through. It is like the lava is wielding the aquifers shut as it passes through them.
Most of the water that was seen in the vent came from much more shallow infiltrations of sea water, so let us not mix them together. What little came up from the depth just worked as an additional driver of the eruption.
All was well up until the 14th of January. It was a typical fairly benign Surtseyan eruption slowly building up to an archetypical VEI-4 eruption. On the 14th we had the main eruption, a VEI-4 of some magnitude that removed quite a bit of the island the vent was located at.
It was this excavation of material that spelled the doom of the caldera. Instead of rockmaterial of various sorts compressing the first supercritical layer we now had comparatively lighter water on top. Instead of the 220 Bar we might have had as little as 100 Bar.
I wish we would have had instruments and a camera there when what followed happened. It would have shown a wild ride.
As the pressure from above was lowered the Supercritical water started to move from a more fluidlike state into a more gaslike state, in turn pushing what was above upwards. In the first hour the uplift was probably just a few centimetres, but in the end the ground probably bulged several metres an hour.
In the end the rock layer could not hold it back, instantly all of the supercritical water transformed into dry steam (flashover) and as it did so, it flung up the rock above it in a process taking a second at most. With this layer removed there was not enough pressure left to contain the next layer, and that went up a few second later, and most likely the process had a final third explosive decompression.
All that now remained was for the ocean to fall into the hole that had been produced. At this point there was just a little bit of boiling of the sea water, and the eruption was halted for this eruption.
In a while an “Anak Hunga Tonga” will be born as the volcano rekindles its work, but that is a story for the future.
Conclusion
The question that remains is as follows: Have we just been lucky? Is this a style of eruption that could be far more common that we previously believed?
I think we have been lucky indeed. It is most likely far more common than previously believed, because this type of eruption has a much more common form named a Maar-formation.
Unlike a normal Maar-formation (that can be quite ugly) any calderas contain large amounts of supercritical water, and in my view, it is imperative that we upgrade our risk-assessments to also include this style of eruption.
For calderas near cities like Campi Flegrei it is important that we drill deep into the roof of the magma reservoir to build accurate maps of how much supercritical water there is, and where it is located.
This was a fortuitous wakeup call for science. We need to learn, and learn quickly, because having Tsar Bomba going off next to Naples is bad mojo indeed.
CARL REHNBERG
Thanks for the article, very interesting lines of reasoning. Have to think about it.
It may even be that
“having Tsar Bomba going off next to Naples is bad mojo indeed.”
is a rather conservative comparison. As far as I understand the statement from the CTBTO girls and guys
(https://www.npr.org/2022/01/21/1074438703/nuclear-test-monitor-calls-tonga-volcano-blast-biggest-thing-that-weve-ever-seen?t=1642784737994)
“According to Le Bras, atmospheric measurements in Austria, roughly 10,000 miles from the eruption site, detected a shock wave that was 2 hectopascals in strength. By comparison, the largest nuclear weapon ever tested, the Soviet Union’s Tsar Bomba, generated a shock wave of just 0.5-0.7 hectopascals in New Zealand, which sits at a comparable distance from Russia’s nuclear test site in Novaya Zemlya.”
implies that the 50MT TNT is basically the energy budget for the pressure wave. That would fit precisely with your calculation. But scarily also implies that the amplitude was a factor –3 larger than for Tsar Bomba. Obviously one can not compare directly, but if the energy of the pressure wave alone is about as large as the total energy of the nuclear weapon, the total energy of the volcanic blast can turn out to be even substantially higher than 50MT. An obvious candidate that must have carried away a lot of energy is the tsunami.
There Bomba was detonated in the atmosphere, so all that blast energy affected the atmosphere
A huge amount of energy from the Tonga event went into generating a tsunami
That on recent examples would require a magnitude >8
earthquake to produce
Steam eruption?
I say gas gas gas
I think you will find this was a VEI-0 eruption, 0.000001 Mt, ash column to 30cm, tsunami 2mm.
Downgrading happens:
The Millennium Eruption of Changbaishan Tianchi Volcano is VEI 6, not 7
https://link.springer.com/article/10.1007/s00445-021-01487-8
Paper four months old
Extremely good. I didn’t know that technical stuff could be so much suspense and good reading.
Thanks a lot.
And welcome to the Ring of Fire and Water!
Another quick comment: such a type of eruption may indeed be more frequent than we think. Without instrumented humans to tell, the traces it leaves in the geological record may make it look much smaller than it was in reality. Phrased differently, without the global 2mbar pressure wave, the long distance tsunami, and the 300km umbrella cloud with an overshooting top to heights unheard of, we all would give in to the “small VEI-4” – crowd, I suppose? 😉
It is quite likely that there are numerous similar small, and not so small, calderas out there that fall under the “VEI-4 Crowd Assumption” and was constituted similar to Hunga Tonga.
Iceland’s most dangerous volcano then?:
Probably was yes, in that case the decompression was from magma draining into a rift. The caldera was formed afterwards though, slowly over the next 40 years, Oskjuvatn wasnt there in 1875.
Grimsvotn and Askja are the two more likely candidates in Iceland, though chances of them doing another eruption big enough to effect their calderas so soon after the last one is not high. At least they are both harmlessly in the middle of nowhere, Kilauea could have done this in 2020 if things went different and killed thousands, and then we maybe dont need to introduce Taal… :O
I can only imagine the sheer confusion and shock of every volcanologist if Kilauea was the volcano to do the next Krakatau… the fact even this is not impossible, needs to be big time studies on this sort of eruption now.
I agree on Askja having a lot of potential for a big eruption with Öskjuvatn on top of it, but at the same time it is also a strong candidate for the most pleasant crater lake to swim in. Viti has an absolute perfect temperature, super nice (if you can handle the sulphur smell that is).
So what I took from this –
Water is bad.
Whisky (with ice) is good.
Got it.
Managua is definitely the worst located, at least in Naples you might be able to put the headland (or Vesuvius) between you and an eruption, not sure what the traffic is like mind.
Italian traffic, but worse.
Mostly near standstill. But Campi is near Pozzuoli, better. Naples would get the tsunami though. Map:
Devil may care:
https://www.volcanocafe.org/devil-may-care-campi-flegrei-ndvp-3/
The explosion would do Naples in on it’s own. And the tsunami would be way worse in the confined space and shallow waters of the bay.
Wasn’t thinking of a 7 like 39k years ago. It had a lot more rocky material than Hunga, but probably anyway. Quite close, Naples and Pozzuoli.
Great writeup, Carl! I think you have hit the right explanation.
I f we look at the 8 caldera events in the last 222 years we get the following very sobering list.
1. Tambora, true explosive caldera formation.
2. Askja, collapse caldera formation, partial explosive caldera formation.
3. Krakatau, krakatau-style caldera formation.
4. Santa Maria, Flank-collapse style of caldera formation.
5. Novarupta, collapse formation.
6. Mount St Helens, Flank-collapse.
7. Pinatubo, small explosive caldera formation.
8. Hunga Tonga, krakatau style caldera formation.
Two Krakataus
Two Flank collapse
Two collapses
And two true explosive caldera formations.
If this holds true down the centuries 1 in 4 caldera event is a Krakatau style of explosive formation.
Don’t forget about Bezymianny in 1955. It had a similar episode to Mount St. Helens after being declared extinct by Russian volcanologists.
Interesting and scary. I think you nailed it. I wonder how many natural tsar bombas are really out there, just waiting for a bad day? What would be the prerequisites for large enough layers of supercritial water to form at suitable depths so that a run of the mill VEI4 eruption can trigger the blast? At Hunga nomore, there is, as you say, a very abundant supply of water in the form of an ocean. Does it have to be under water, or could the same scenario happen at a volcano below a glacier?
On a side note, was the same mechanism responsible for the Krakatau blast? It probably was, right?
All of the other conditions was there, so I would say it is likely at least.
It probably depends more on if there is enough supercritical geothermal fluid than what water is on top. That is why you would need to at least have good geosounding of the bedrock, and preferably drill-cores.
I was thinking that the two we know of both had water on top and maybe that favors supercritical fluids below.
Geosounding sounds like a good idea. Once you have found your supercritical fluids I guess the correct action is to harness them for geothermal power.
Harnessing the geothermal energy would if nothing else lower the risk by an incredibly minute amount, so it is also therefore a good idea.
How minute? I calculated this for a very large inflating caldera (that I can’t name for company reasons). If we extracted 1200MWh continuously for 25 years we would delay the eruption with between 2 seconds and a full minute… That miniscule…
What about the effect on my electrical bill? It’s been ridiculously high lately 😅 (oh, and also saving the climate, almost forgot)
With enough funding we would make a dent in that bill.
Carl. please DO make a dent in that bill. I know that is totally not a realistic request 🙂 therefore the grin, but with energy bills rising higher than this old UK pensioner can realistically meet it is just a wistful pipe dream.
However I wish to thank you very much for this interesting treatise of what happened at Hunga bye bye. I found this article really interesting, more particularly that you were able to explain things in a way that a non-scientific person such as myself was able to fully understand and which resonated with the thoughts I already had that this eruption was truly out of the ordinary compared to modern volcanology. Many thanks again!
Sadly I can’t really discuss where we will build, and what we will build, and how we will transfer the power.
So, I can’t discuss any impacts on electricity prices in the UK…
It is also depending on the amount of funding we can get our grubby hands on.
Remember that the going price for a large geothermal plant (as we define large), is 1.8 to 2.5 billion Euros.
The fact that this is relatively rare suggests that quite specific conditions need to be met.
In particular a large mass of water at depth. To achieve this may be harder than you think. To add it to a terrestrial volcano may be rather hard for a whole lot of reasons, it happens here because the volcano to is below sea level (infinite water supply) that immediately floods the cavity vacated by the ejectate. So its common, but not usual.
Mayhe these caldera are relatively stable systems and being covered by a lake or ocean generally moderates them more
But occasionally something goes wrong
Cascading chain of events
Perhaps super eruptions are these catastrophic failures
And not expected events
And that is why they are so historically uncommon
In some ways its a race between water and heat. If we are to start with a very porous plug remaining from the earlier eruption this has to be filled with water before the plug self-seals. I suspect plugs self seals (that is to the km+ depths) quite quickly which would demand a rather high flow/availability of water at the start.
I suspect slow water delivery rates will allow enough time for the rubble interstices to close up and thus limit the amount of supercritical water available at depths (mineralisation may have a similar effect). So explosions of this magnitude may be relatively rare (but locally common).
As always the spectrum will be continuous depending on the amount of water available at depth. I think usually its water from the melting plunging slab, but this has limited supplies of free water because, as you point out, supercritical water is highly reactive.
I don’t know if this is insensitive, but Hunga Nomore sounds like a great name for a Tongoan restaurant.
No more hunger?
Oh if I was younger I would totally use that name for at least a cafe. Being well into pensioner age now it is not a realistic proposition for me even though my husband is/was a superb cook but now hamstrung by arthritis.
Chicxlulub was 200 million tsar bombas in once instant, in form of shock and vaporization of Earths local crust and the vaporization of the asteorid at impact site .. really insane
Thats the biggest blast in 100 s of millions of years by simple kinetic energy
Thank you Carl for this article!
Looks like the Hunga eruption was indeed a giant steam bomb, did the Kikai eruption steam detonate too ?
Woud the soundwave kill me If I was 20 km from the Hunga blast ?
Hard to say really Jesper.
I do not think you would like to test this Jesper.
Incredibly fortunate there very few people in close proximity to this volcano. Not to say it wasn’t destructive, just that it appears the toll from the initial blast itself was limited by its isolation. Very fortunate in this case, but maybe not so much if the same thing were to happen elsewhere.
Seems like this event is going to quickly propel Volcanology forward.
Several of the Kurile Islands must have had a similar fate, particularly Lvinaya Past, Chirpoi, Zavaritsky, Urataman (looks massive on Google Earth), Ushishur, Sarychev, Tao-Rusyr – strong evidence of water interaction blasting out a caldera. Been looking a lot at this region lately.
Thank you. Good read! A lot of information that makes sense.
I have a couple of questions on the SO2-assertions;
“SO2 is a volcanic gas emitted from volcanoes together with fresh lava. Old lava contains comparatively little SO2 since almost all of it is transformed into all sorts of organic and non-organic sulphuric compounds, and those do not readily transform back into SO2 if lofted skywards.”
Reading several papers on this basically saying much of the same, is it basically turning what would normally be SO2 into different sulphuric acids as part of the explotion (we have to consider salt here too), or do we not know as of yet? Looking for (for instance) H2SO4 is not beeing seen looking for/measuring SO2. It requires different settings. Although they may very well have been measured already, I have just seen numbers for SO2, that is why I ask. I saw one paper citing really high H2SO4-numbers in experiments (and low SO2) involving steam/melted Ryholite-interaction. There is also mentionings of particles (in general) beeing quite smaller as a result from this type of eruptions.
The article you mentioned on the size of the blast clearly indicates 3-4 Tzar Bombas, but let’s just wait for that. 😉
https://text.npr.org/1074438703
“According to Le Bras, atmospheric measurements in Austria, roughly 10,000 miles from the eruption site, detected a shock wave that was 2 hectopascals in strength. By comparison, the largest nuclear weapon ever tested, the Soviet Union’s Tsar Bomba, generated a shock wave of just 0.5-0.7 hectopascals in New Zealand, which sits at a comparable distance from Russia’s nuclear test site in Novaya Zemlya.” (wow)
Our local station detected the initial shockwave at ~2,7 hPa. 17.100 km away. That would be 10.625 miles…
Yes, it would be in salts and other compounds not measured by the satellite in question.
Also, an eruption of this speed would shred anything into fine dust.
It is not that straightforward to calculate a nuclear blast, I am happy with the 55-60MT I got, the peak amplitude is just one number to contend with.
Problem with nuclear blasts to.geological.events
The nuclear bomb is placed.in position with the ingredients for the necessary yield
Which is mostly released as heat a.fireball as hot as the sun at its heart
The volcano has the heat already 8n place and ready to tap into a by comparison cooler heat source but monumental in comparison with even a 50Mt hydrogen bomb
In this case heat is transferred into explosive force , via.pressurised volcanic games including water vapour
That’s the fuel and the ocean is the coolant
I think for expressing the explosivity we should perhaps just use the energy in the pressure wave. Luckily that’s easily measured these days and can be given quite a good precise figure. Tying it to atmospheric nuclear blasts is an excellent way to get a feel for these big numbers.
Would the 1754 eruption of Taal compare to this?
Taal 1754 was a “normal” eruption as far as is known.
I do not think we wish to contemplate what a supercritical eruption at Taal would look like. Thankfully this not seem to have happened in the past.
Silly question, would the extreme lightening be a result of the electrical conductivity of the salt water. It seems as though less actual ash was involved to get that high a count from friction of particles of solids.
Good question. It sounds plausible, but I will let one of our meteorology commentators answer that.
Where is Andrej when needed.
From Andrej Flis:
The point she makes is 100% there.
It is well known that hydrometeor charging is also present in ash plumes, depending on the style of eruption and the aboundance of the external H²O
So in the case of Tonga, this was a best case scenario, having a “submerged” blast, with plenty of H2O available for aditional charging from hyfrometeors. Cant tell to what extent, as despite having less ash than in a “typical” such blast, there was plenty of material available in that short but powerful blast for the triboelectrification and fracto-electrification, boosted by the hydrometeor charging from abundand water in the mix.
hydrometeor charging?
‘Meteo’ as from weather. It is used here in the meaning of water that originates as rain or snow. It is not the right term for water that came from the sea. ‘Charging’ for acquiring an electric charge.
So it means there was a lot of erupted water that condensed out as rain, just a big local thunderstorm with crazy windspeeds and windshear?
OK.
This eruption was a good appetizer but I want more. 7,500 km3 ultra violent eruption that will destroy entire countries and cause hemispheric ashfall. Hopefully 2022 is the year
Hopefully not
These kind of comments are extremely disturbing.
It seems like Jesperitis is contagious…
Seems we are too bored for the real world, so we begin to imagine thing too ridiculous to comprehend.
I think it is mostly Ennui caused by The Pestilence.
Oddly enough, it has been during these pandemic years that my casual interest in things geologic was reawakened. Where I live, the night before lockdown was to begin featured a mild earthquake that was nevertheless strong enough to knock books and pictures off the shelves. I hadn’t been woken up by an EQ in 40+ years (though I did sleep through a couple that woke other people).
I’m not sure I would have made it through the second year of the pandemic without volcanos. Etna (I think that’s when I discovered VC), Kilauea, Iceland, La Palma, Kilauea again, Hunga Tonga…
While I’m in absolute awe of the power of Hunga Tonga’s explosion, I’m happy if we don’t have to experience anything like it for quite some time. Now, if we could just arrange for Pele to give us another nice tourist eruption in Iceland, one where idiots could get too close to molten lava and competing TV networks would set up multiple 24/7 live-streaming webcams so I could relax to streams of that wonderful lava flowing down the barren but beautiful hills…
I think Pele would arrange a Krakatau style eruption in Iceland, make the hydrothermal field at Hengill blow up, making Iceland uninhabitable in the winter and maybe going for direct hit on the capital… 🙂
Got to remove the competition from Kilauea, you see 😉
Not sure that field can blow up though, no caldera to bound it, and eruptions from Hengill seem to be the same as at Krafla, curtains of fire, and occurring above the magma chamber so there is no chance of caldera formation or loss of pressure. Same at Krysuvik, although that might be a bit less certain, Kleifarvatn looks like it might be a maar, Carl probably knows.
Krysuvik is indeed the goto place if you want to see a Maar. It is though dry as a bone.
That is good then, dont need a nice effusive eruption on Reykjanes, one that after last year would no doubt draw a crowd, really dont need that suddenly going krakatoa…
Maybe good thing Grimsvotn and Askja are in the middle of nowhere, more of an inconvenience than a disaster, though probably a big shock.
Tallis Rockwell an Asteorid/ Comet Impact does it even better, best you wait for Swift Tuttle or the cometary shower that will be result of Red Dwarf stars Gliese 710 C s extremely close passage to the solar system in the future .. and that means waiting more than a lifetime 😉
And only Gliese 710 s C passage is certain, tuttle not certain in anyway, and the star will get as close as 4000 AU and Will Certainly mess up the Ort Cloud that contains trillons of comets that stretches over a lightyear .. then you will have to wait 1 million years 🙂
But the most fun and civilization safter alternative is a huge VEI 8 deep sea submarine eruption like Gakkel Ridge had. That woud form a massive pumice mats with volume of the whole Vatnajökull Glacier. It erupted in the deep sea, and probaly competely safe for humans on the surface, 3000 km3 of materials where barfed out on the seafloor. Here are the paper: a Deep Sea Toba! And How the hell does a spreading ridge accumulate a 3300 km3 Ryholite chamber, perhaps slow and steady accumulation that evolves and gets Stale like in Icelandic central volcanoes .
The Artic Ocean must have been filled by Pumice after this event
Never knew before that the Deep Sea can have catastrophic VEI 8 pyroclastic eruptions But pressure in the magma chamber probaly even triumphs the sea pressure .. paper
https://www.nature.com/articles/srep46248?fbclid=IwAR32pFxN7_4ZxOtKTf7jRfj_ZQOKRahY9PVqq1jRxYsYAgGC8miegEJcgSQ
Asteroid impacts are too mainstream for my taste. GRB or rogue planet would be cooler.
Gakkel ridge is very slow, and it says this was near where it contacts a continent, seems a case of constant very slow magma supply building up, and then it erupted. It is kind of like a deep sea version of Torfajokull except orders of magnitude bigger. Except in this case it seesm confirmed it was a direct eruption and not lateral intrusion and subsidence, which is probably a large part of the story for Torfajokull as it is for other Icelandic volcanoes.
I guess, there are VEI 7-8 calderas in east Africa, from divergent boundaries under a continent, this is basically the same thing but under the ocean.
You should get an even bigger explosion if you avoid the critical point. Water at pressure ands temperature above the critical point has a density that is about ten times less than ‘normal’ water. (That is why black smokers rise.) As you drop the pressure while keep the temperature high, it turns into a gas (as you say) and this has 1000 lower density than normal water at surface pressure. So it expands by a factor of 100. If you do the same process at lower pressure, it can expand ten times more.
Is Tongas shallow chamber gone now then ?
It was probably not so shallow to begin with, and no. What is blown out was the roof of the magma reservoir.
And most likely not all of the roof, given the small SO2 amounts. Really it just lost a few shingles.
It lost the shingles, but the planking remains…
I don’t like the roof or lid analogies
But with that much energy down there
If the lid or roof really came off…
Let’s not even go there
Carl question
Is Lengai and Kilimanjaro on a Craton?
Are they rare Craton volcanoes? The litosphere is certainly thick in Tanzania and that part of the GAR ( great african rift ) seems to have problems of getting further south deeper Into Tanzania because the litosphere gets so old and thick
Im tempted to Ask even if its not article subject
Ol Donyo Lengai is a cratonic volcano, and I suspect the same goes for Kilimanjaro, but that seems to have a local rift under it, an old suture that has opened up.
Keeper, the African Rift continues into Mozambique then branches east up the Limpopo River valley heading west. The rift is still active, we experience the occasional tremor.
Hmmm Lake Natron is on a rift as well as Lake Eyasi .. Lengai is on this rift
Nope Lengai its not a Craton, its still on a divergent plate boundary. but the rift is trying To get into a Craton. The rift stops just South at the Msawa Game Reserve.. because the litosphere gets too thick?
Kilimanjaro, Mount Kenya, and Mount Elgon does seem To be true Craton volcanoes, but found only at the edges of the great cratons in Africa
Kilimanjaro and Ol Doinyo Lengai are not really true cratonic volcanoes, but Ol Doinyo Legai, however, is perhaps closer to a true cratonic volcano because it has its exotic magma due to the melting of edges. If you want to see a true cratonic volcano, enter the kimberlites. They are, though, monogenetic (aka only erupts once) but they are quite powerful despite their size. They possibly have the faster magma ascent than even those back at Bardarbunga in 2014 and, once they erupt, they are equal to or more powerful than the explosion we saw at Hunga Tonga, so yeah, no where is ever safe from volcanoes.
Yes Kimberlites.. and the youngest Ingwisi Hills are holocene .. its fantastic how they get through a sometimes much more than 300 km thick Craton!
Some persons thinks they are propelled like rockets by their gas content, its a long way to go from the start of the astenosphere and up trough the superthick litosphere.
Carl, thank you for this article. It satisfies my scientific curiousity and answers my questions, I knew that such a huge explosion had to be more than just the normal things.
I know awhile ago that some volcanologists wrote papers on magma mixing and explosive eruptions, such as Montserrat, but would you say that this supercirtical water is the overlooked factor here, not just gas effloresence?
I live near 3 volcanoes, St Helens, Rainer and Hood, but I am concerned about Hood going into a caldera event.
Randall
Supercritical water doing a flashover is definitely energetic enough to drive a very explosive eruption like this.
It is definitely overlooked, as and when it happens. But, for most volcanoes it is not a big factor.
I have noticed that in the US many look at Mount St Helens and think that this is a great risk for the other volcanoes in the vicinity. It is here good to remember all the times that St Helens did normal eruptions. There is a risk, there always is, with volcanoes. But the risk that it will happen again during a lifetime? Almost non-existant.
Also, there are more risky volcanoes in the continental US.
If I would point any fingers Fourpeaked in Alaska would be the most likely to go standard caldera in the future.
Why hood in particular ? Calderas are pretty rare in the Cascades to begin with. That being said the easiest spot that I could imagine a caldera forming in the near geological future would be near South Sister.
It is commonly said that magma mixing, hotter material coming up and reheating the colder magma and also causing gas release is what can cause a caldera collapse. Hood had two magma chambers, and for awhile it was reported that Hood could be a candidate for a caldera type eruption. Others jumped into this discussion and said Hood could never have a caldera eruption that the magma reheating took place at a safe rate.
Can anyone explain why Mount Mazama blew up and became a caldera eruption? It actually had many eruptions before that final one.
I guess nobody knows for sure, but Mazama seemed to start growing a large, integrated shallow magma accumulation about 30 thousand years ago, after mostly having small or isolated magma pockets at shallow depths through most of its 500 thousand years or so of cone building activity. By the early Holocene the accumulation of shallow magma had grown to 50 km^3 and it was more possible for an eruption to tap a large amount of magma at once, and cause the roof rocks to collapse and start caldera formation.
I think the best candidate for a big event could be Mount Mazama in 2000 years or more, probably not now. The setting is so inviting with three little devils taking a bath, and the biggest of them might want to have a lake of his own like Taal has, that’s standard..
On the other hand, I also think that Mount St. Helens was managed very well. The people who were in there at the time of the flank collapse had gone there in spite of warnings. So, Americans seem to pay attention, but that might be the same in other countries. The difference is the number of people living there on a permanent base. It is easier to keep tourists at a distance than evacuate people without knowing where.
Jesper, the African Rift continues into Mozambique then branches east up the Limpopo River valley heading west. The rift is still active, we experience the occasional tremor.
Are not the Zambezi and Luangwa valleys also branches of the Rift? Both now filled with sediments of staggering depth.
Yes.
Many thanks for this article! it should stimulate a lot of scientific discussion.
Given the unprecedented global effects of this eruption and the possible outsized role of water-magma interaction, is anyone in the volcanological community thinking of assigning it a new category? “Plinian” or Surtseyan” as commonly used seem to inadequately capture its intense detonation effects – the nearly hemispheric extent of the shock wave and tsunami, the extreme height of the column relative to erupted volume, and the relative paucity of SO2. A new term might be appropriate to convey the scope of these effects, particularly if supercriticality or some other mechanism was unusually important relative to more typical eruption mechanisms.
“Ha’apian”, perhaps?
I second your comments, we should have a 3rd category.. or at least a recognition that supercritical water plays a key role in certain types of volcanic eruptions.
And I do feel sad, that now we are finding out that the tsunami was a lot higher than first reported, 45 ft high on one small Tonga Island, wiping all the homes out completely
It would be great if we could somehow have a history on all the submarine and surface volcanoes of the Tonga arc, as there are some big calderas there, most are submarine.
I was worried that the tsunami might have been worse than it seemed at first. Most of the early footage was from Nukualofa and the tsunami there would have had to drag across about 10 km of reefs and shallows to get there. That might have greatly weakened the tsunami at Nukualofa.
Mr. Norris, I was actually thinking about this same thing yesterday. How about “Tongan”?
Since the type case is good old Krakatau (Krakatoa for those of the Imperial persuasion) the new nomenclature will be Krakatoan.
It has been debated previously, but since it was a case of one it was postponed until/whenever there was a second instance.
So, Krakatoan eruption it is.
Ah, I was kind of hoping for Ha’apian. I’ve grown to like Hunga Tonga-Hunga Ha’apia even if I never quite pronounce the last name correctly. But I understand that we need to follow the established rules of precedence.
Now, if someone could explain to me the Icelandic system for naming volcanos… 😕
You take either a naughty word, or a raunchy story, and add Fjall, Vötn, Dal, or plain old Bunga to it and you are good to go.
Unless of course you get such a stupendously naugthy word that you need no addendum to the name.
To all points and purposes, it is like they UKians would have named Arthur’s Seat into Mount Dogging.
You will not get anyone from Iceland to openly admit to what I just wrote being true, but I point to Exhibit A: Upptyppingar and Exhibit B: Geirvörtur. Your Honour, I arrest my case!
🙂 🙂 🙂
I’ve always felt that, when it comes to naming things, Icelanders have a rather ribald sense of humor. 🙂
It’s probably for the best that Icelanders aren’t in charge of naming things in my part of the USA, or they’d surely use “Upptyppingar” rather a lot. It’s bad enough without the Icelandic nomenclature; the linked pic below is of a rock formation in Kodachrome Basin, Utah, called “Big Stoney”.
Please be advised that the linked pic is NSFW; it’s just a rock formation, a sedimentary pipe (geothermally fused sandstone left behind when the surrounding sandstone eroded away) , but from certain angles (I’ve seen it in person many times) it looks decidedly NSFW, even more so than in the linked photo (especially on an overcast day). And if a moderator feels this link is inappropriate and thus my comment needs deleting, I shall fully understand and not object.
Hrmmm, my link didn’t post.
In case the link doesn’t post again, the image name is Big_Stoney_Kodachrome_Basin_1217.jpg
Mega-geyser ??
Okay, is only a one-shot, but distinguishes from ‘mere’ maar and caldera collapses with their different mechanisms…
Perseverance films VEI-0 ejection of volcanic rock on Mars!
https://mars.nasa.gov/mars2020/mission/status/359/ejecting-mars-pebbles/
There is a great deal of interest among the world’s aviation community about this (and other) volcanic eruptions. That’s rightly so, as airborne eruption products severely affect all aircraft. I have discovered that great minds (yours, not so much mine) in earth science and aviation think alike, so some of you might want to see what some of those in aviation are thinking. Here is a post to a thread about the Hunga Tonga eruption on the Airliners.net website . . . https://www.airliners.net/forum/viewtopic.php?f=11&t=1469253
https://twitter.com/PlatformAdam/status/1484576991735164929
I just found this paper NUMERICAL STUDY ON HEAT EXTRACTION FROM SUPERCRITICAL GEOTHERMAL RESERVOIR Kimio Watanabe1, Yuichi Niibori2 and Toshiyuki Hashida but the key finding is that supercritical water is able to extract much more heat energy from the rock than normal hot water. This suggests that the explosion at Tonga Hunga was amplified perhaps by this fact?
That paper is a staple if you work with geothermal extraction out of volcanoes, and it was a source for the article (among others).
Thank you, Carl, for this article, and especially for for explaining the mechanism. That’s been the most puzzling thing for me in this eruption.
It seems that you don’t put much faith in the Internet-ubiquitous 200 megaton number for Krakatoa. I never have either, as it seems to be derived from the VEI, and the VEI measures ejecta, not blast.
I’ve likewise been highly skeptical of NASA’s 10 megaton estimate for Hunga Tonga, and that was before I became aware that the amplitude of the pressure wave at roughly the same range was four times larger for Hunga Tonga than Tsar Bomba. The main reason I was skeptical of NASA is what they didn’t (so far as I can find) mention; how they came about that estimate. Like any unsubstantiated claim, it’s best to be skeptical – indeed, the scientific method demands it.
The Hunga Tonga eruption was astounding in many ways. It’s also absolutely crucial to know the explosive yield, because that helps us understand the dynamics, and thus helps us understand the risks. This is especially pertinent because a massive blast of this sort seems to leave little evidence of its magnitude in the geologic record, so we don’t know how frequent such blasts are. We have too small a sample set to say with any confidence whether these are once a century events, or significantly more or less common than that.
In this link posted earlier (https://www.npr.org/2022/01/21/1074438703/nuclear-test-monitor-calls-tonga-volcano-blast-biggest-thing-that-weve-ever-seen?t=1642784737994) NASA explains that their 10 (downgraded to 6) megaton estimate was based solely on the amount of energy needed to obliterate the island. From that article:
“Jim Garvin, the chief scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., who made the original estimate, is more cautious.
” ‘We have to be careful to compare it to a nuclear explosion, because it’s a different process,’ Garvin says. His team’s calculations are based purely on the energy required to destroy the island around the volcano. That island had been closely monitored since it first formed in 2015, and Garvin says he believes the group’s calculations are accurate for the energy required to obliterate it.
” ‘Our estimate is based on moving stuff,’ he says. But it does not include other forms of energy, such as the energy released by the water turning to steam as it touches molten rock, or magma.
“It will take time, he believes, to get a true estimate of the size of the Tonga eruption: ‘When the teams all get together and put these numbers together, the energy balance will come out,’ he says.”
Thank you, John N!
I hadn’t seen that. So, at least now we know what they based their estimate on. I also hadn’t heard that they lowered it to 6 megatons.
I’m still skeptical of it though, because of the atmospheric shockwaves, compared to a known event (Tsar Bomba, 50 megatons) at a comparable distance. (Austria for Tonga vs. New Zealand for Tsar Bomba) was .5 to .7 hectopascals for Tsar Bomba, 2 hectopascals for Hunga Tonga.
I’m more inclined to listen to the Comprehensive Test Ban Treaty Organization (CTBTO), because their infrasound sensors are what they used to come up with the 400-500 KT energy of the Chelyabinsk bolide detonation. So far, all any of their scientists have said (That I can find) is that a “very rough back-of-the-envelope calculation suggests that the energy was around 50 megatons. We haven’t done the real analysis that it would need, but it doesn’t seem like it would be smaller.”
https://www.wabe.org/nuclear-test-monitor-calls-tonga-volcano-blast-biggest-thing-that-weve-ever-seen/
I agree. My gut feel is that the final estimates will be in the 50 megaton ballpark that both the CTBTO and Carl independently calculated on their respective envelopes. This was a very big boom. ❗
Your writing makes a lot of sense. And yep there’ must be out there many potential krakatonga setups waiting for their hypercritical steam release. Once per century could be a good estimate to start with.
There have been a lot of earthquakes at Hunga Tonga Hunga Haapai lately, particularly after January 18, according to IRIS. Not sure what’s happening. Maybe it’s just the caldera settling, or it could be something else.
Year, Month, Day, Time UT, Mag, La, Lo, Depth km, Region, USGS ID.
2022 01 21 19:50:43 4.8 -20.6839 -175.3949 10.0 54 km NNW of Nuku‘alofa, Tonga us7000ge1p
2022 01 21 13:22:33 4.8 -20.7823 -175.3815 10.0 43 km NNW of Nuku‘alofa, Tonga us7000ge1f
2022 01 21 05:45:58 4.7 -20.7481 -175.3195 10.0 45 km NNW of Nuku‘alofa, Tonga us7000gdrz
2022 01 20 23:33:52 4.7 -20.4834 -175.4169 10.0 76 km NNW of Nuku‘alofa, Tonga us7000gdpt
2022 01 20 20:05:30 4.8 -20.3512 -175.3802 10.0 89 km NNW of Nuku‘alofa, Tonga us7000gdmq
2022 01 20 17:10:03 4.8 -20.4535 -175.2501 10.0 76 km N of Nuku‘alofa, Tonga us7000gdpe
2022 01 20 08:29:43 4.6 -20.8171 -175.5203 10.0 48 km NW of Nuku‘alofa, Tonga us7000gdqc
2022 01 20 03:06:12 4.6 -20.7028 -175.3846 10.0 51 km NNW of Nuku‘alofa, Tonga us7000gdqg
2022 01 19 23:23:49 5.0 -20.8485 -175.4097 10.0 38 km NW of Nuku‘alofa, Tonga us7000gdcz
2022 01 19 20:18:10 4.6 -20.5931 -175.4137 10.0 64 km NNW of Nuku‘alofa, Tonga us7000gdqq
2022 01 19 18:22:17 4.8 -20.7456 -175.4360 10.0 49 km NNW of Nuku‘alofa, Tonga us7000gdqu
2022 01 19 11:37:50 4.6 -20.5640 -175.3449 10.0 65 km NNW of Nuku‘alofa, Tonga us7000gdqy
2022 01 19 07:48:56 4.8 -20.5827 -175.3163 10.0 62 km N of Nuku‘alofa, Tonga us7000gdp8
2022 01 19 05:34:39 4.6 -20.6282 -175.6985 10.0 76 km NW of Nuku‘alofa, Tonga us7000gdzh
2022 01 19 03:37:29 4.6 -20.4401 -175.3146 10.0 78 km N of Nuku‘alofa, Tonga us7000gdf7
2022 01 19 02:10:06 4.6 -20.8442 -175.3193 10.0 34 km NNW of Nuku‘alofa, Tonga us7000gdza
2022 01 19 01:16:39 4.8 -20.8291 -175.3305 10.0 36 km NNW of Nuku‘alofa, Tonga us7000gd26
2022 01 18 22:01:10 4.6 -20.8575 -175.1559 10.0 31 km N of Nuku‘alofa, Tonga us7000gde9
2022 01 18 17:59:54 4.9 -20.6508 -175.6063 10.0 68 km NW of Nuku‘alofa, Tonga us7000gcz2
2022 01 18 14:31:50 4.6 -20.6843 -175.3304 10.0 Tonga us7000gdyh
2022 01 18 11:03:55 4.6 -20.6174 -175.6148 10.0 72 km NW of Nuku‘alofa, Tonga us7000gcuy
2022 01 16 05:46:18 4.7 -20.6200 -175.3892 10.0 60 km NNW of Nuku‘alofa, Tonga us7000gds7
2022 01 16 02:24:37 4.8 -20.8784 -175.4558 10.0 39 km NW of Nuku‘alofa, Tonga us7000gdef
https://ds.iris.edu/ieb/index.html?format=text&nodata=404&starttime=2021-12-15&endtime=2025-01-01&minmag=4&maxmag=10&orderby=time-desc&src=usgs&limit=1000&maxlat=-8.60&minlat=-39.85&maxlon=-156.71&minlon=146.12&zm=5&mt=ter
Looks like you are right. . lots of 4’s
Also possibly very well monitored at this time:
“Researchers in New Zealand say that they are closely monitoring the volcano for further eruptions. “We are just keeping our ears to the ground,” says Shane Cronin, a volcanologist at the University of Auckland. The volcano could be resupplied with large amounts of magma from deep underground and produce more explosive eruptions, he says. But if it has exhausted its main supply, it might produce only smaller eruptions, largely hidden beneath the surface of the ocean.”
https://www.nature.com/articles/d41586-022-00127-1
Basically the article (by David Adam) is about the concentirc ripples in the atmosphere though.
First thoughts by marine biologists about the reef, based on last eruption:
https://www.rnz.co.nz/news/national/459937/will-hunga-tonga-hunga-ha-apai-reefs-recover-post-eruption
This might be interesting concerning the sulfur:
“An objective color observation conducted during 2000–2007 revealed that the lake water color changed from blue-green to solid green. The disappearance of the blue ingredient of the water color will result in diminution of aqueous colloidal sulfur from chemical analyses of lake waters sampled simultaneously. The aqueous sulfur is produced by the reaction of sulfur dioxide and hydrogen sulfide supplied from subaqueous fumaroles. However, its production efficiency decreases by domination of sulfur dioxide in the subaqueous fumarolic sulfur gas species with increasing subaqueous fumarolic temperature. The disappearance of blue ingredients from the blue-green color of the lake water may be attributed to activation of subaqueous fumarole activity.An objective color observation conducted during 2000–2007 revealed that the lake water color changed from blue-green to solid green. The disappearance of the blue ingredient of the water color will result in diminution of aqueous colloidal sulfur from chemical analyses of lake waters sampled simultaneously. The aqueous sulfur is produced by the reaction of sulfur dioxide and hydrogen sulfide supplied from subaqueous fumaroles. However, its production efficiency decreases by domination of sulfur dioxide in the subaqueous fumarolic sulfur gas species with increasing subaqueous fumarolic temperature. The disappearance of blue ingredients from the blue-green color of the lake water may be attributed to activation of subaqueous fumarole activity.”
https://www.researchgate.net/publication/225618538_Color_change_of_lake_water_at_the_active_crater_lake_of_Aso_volcano_Yudamari_Japan_Is_it_in_response_to_change_in_water_quality_induced_by_volcanic_activity
In my second link from rnz there’s a photograph from space showing that the lake was green.
Another green lake is Taal’s crater lake:
What a garbled and unclear statement. A few chemical reactions would clrify things because it sounds like the writer hasn’t got a clue and is covering up.
I think he means that colloidal sulphur is produced from H2S when SO2 levels are low and [some other deposition method unstated] takes dominance. [probably more massive deposition at H2S outfalls o].
Imperfect English from the author, I expect. VC of course has covered the colour of volcanic lakes. Can’t always tell the chemistry from the colour
https://www.volcanocafe.org/kelimutu-the-magic-of-colour/
If you don’t like it I suggest reading it in Japanese. Sorry Chad, but as far as I got it we don’t talk about language here.
Not Chad would have surprized me. Now really sorry.
What a nice piece, Albert. I will read it thoroughly later as we are going out to celebrate with a lunch: Our dog’s tumour is benign. I’m so happy. Got the result a few minutes ago.
That piece about the geochemistry of Flores which is on another tectonic setting than Sumatra and most of Java with Krakatau in-between, is very interesting. For me it needs some study-time though, and I will take that time in the next few days. Must be pretty there. I don’t know yet whether this is funny – it probably is:
“But when modern humans expanded into the region, Homo floresiensis faded away”….
Basically they might have been too small to fight Homo Stultus.
I prefer the Komodo a little to the Reticulated Python of Sumbawa.
“We are just keeping our ears to the ground,” says Shane Cronin.
Crikey – I hope they use more advanced detection methods! 🙂
Excellent article. Are you inferring that this eruption was similar to a boiler room explosion in terms of mechanism?
Also I notice there are three 4.8 (more or less) earthquakes today just a bit southwest of the peak of the volcano.
https://earthquake.usgs.gov/earthquakes/map/?extent=-21.74164,183.64197&extent=-19.5132,186.61926&listOnlyShown=true&baseLayer=terrain&timeZone=utc&settings=true
What are the implications of ongoing tectonic activity?
From the article, “For calderas near cities like Campi Flegrei it is important that we drill deep into the roof of the magma reservoir to build accurate maps of how much supercritical water there is, and where it is located.”
Carl is surely aware of this, but for those that aren’t, drilling deep into Campi Flegrei may well be in the works;
http://b-dig.iie.org.mx/BibDig2/P12-0211/papers/10309/12193_natale_paper.pdf
I also note that several major geothermal projects are proposed for the area, so hopefully the needed data Carl refers to will be acquired. I also wonder if the geothermal plants would notice any changes if volcanic unrest increased; if so they might serve a further purpose: early warning.
Wow Kilaueas lava lake is overflowing like crazy now, after pausing for only a few hours and no DI cycle. Maybe those deep quakes meant something after all…
Looks to me like Kilauea is doing what you said it would do. 🙂
The question is, will it continue to do so? I very much hope it continues to be active for your trip. Looks to me like it’ll do so, unless it forces open a rift zone and drains out, like it did in 2018.
The key difference is that even a rift eruption now will not stop the summit eruption, because the ERZ conduit doesnt go far down the rift now. Before 2018 it was able to extend as far as highway 130, well east of Pu’u O’o, because of the high magma pressure. Now the pressure is lower, so the conduit is not complete past Mauna Ulu.
Major, and rather voluminous, flank eruptions happened in 1823 and 1840, but those happened from magma flowing along shallow faults and fissures, very similar to what happens at Nyiragongo. In 1823 the origin was actually directly from the lava in the caldera flowing into cracks towards the southwest. Volume of lava was over 0.1 km3 of lava erupted mostly in a day or 5x as much as Nyiragongo erupted last May and at similar rates.
1840 eruption originated out of the ERZ conduit near Mauna Ulu and flowed far down the rift underground through shallow fissures north of the main rift with small eruptions along the whole length, but mostly flooding out of the ground south of Pahoa. There was also another major drain out in 1832 but no eruption was seen. The lake drained for a final time in the earthquake of 1868.
In all cases lava was drained out of the caldera but the vent was never destroyed, so eruption resumed again immediately or never stopped.
So basically would take nothing short of another total caldera collapse to kill this lava lake now. Eruptions of the type we saw in 1960 or 2018 are decades apart, we are good until at least then 🙂
I’m glad to hear that the ERZ isn’t open as far, because even Pu’u O’o, manged to send lava into towns. Hence, I’m hoping for a SWRZ the next time Kilauea is in a rift zone mood. Or, somewhere near Mauna Ulu would, I think, keep inhabited areas safe.
One of the sights I found quite interesting was Lava Tree State Monument, which is very close to the Puna Geothermal plant (and just a few yards from 2018 lava, per that sat photos). When I was there it was before 2018, and I had exceedingly little knowledge of volcanoes, but I did see that it was thought that Lava Tree was created in the 1790 eruption (the same one that killed a lot of people due to large explosions). The lava trees are basically lava castings of trees, and to me they indicate a very fluid and fast flow for the lava to reach that high, then drain away.
I’ve never found the conventional explanation for Kilauea’s occasional explosive behavior satisfactory (the conduit getting blocked and building up steam pressure). I now wonder if a mechanism similar to what Carl shows us for Hunga Tonga isn’t at play.
And I’m glad to see that you’re going to write an article about your trip!
Lava Tree park was made by a flow in about 1776, which was an eruption of the latter type described above, where lava drained down a crack from further uprift, possibly from Napau crater which had been filled in by a major flood lava fissure eruption some time in the late 18th century (much bigger than anything seen there in the last 80 years), Eruption of 1790 would have been even bigger than 2018, but also probably offshore on the Puna Ridge, and evidently deep enough there was never a trace of it on the surface. The mechanism of the 1790 summit eruption probably was exactly the same as from Hunga Tonga Hunga Ha’apai, not as big of course. I have not found anything very satisfactory about HVO’s explaination of Kilaueas explosive periods, because they only look at summit eruptions, the ERZ has not actually been mapped at all since the 1990s except for Pu’u O’o flows, and there is disagreement about the dating of that time too. Also the fact someone in 500 years would assume we are still in an explosive period because the surface is all tephra and the caldera is not overflowing…
I think personally the caldera will overflow again before rift activity resumes. In theory, the magma supply of this past year is high enough to fill the 2018 caldera by 2030 and the entire caldera pit to the lowest edge within a decade after that. The most recent measurements also suggest the effusion rate is increasing, and quite significantly almost doubling since the 7th, yet even the CRIM station at Keanakako’i is only showing south flank slip, it is as though magma moves completely unobstructed from the deep source into the lava lake now.
Interesting!
If the caldera does fill, that’s one heck of an enormous volume of lava. It is to be hoped that it would not drain out into Puna at some point, or there would not be much left in the region with that kind of volume; it’d make 2018 look tiny.
Then there’s the highly suspicious Pahoa quake swarm. That area looks to be more seismically active than the rest of the Big Island combined. It also seems to be oddly ignored to a degree; a few months ago USGS posted an explainer of various kinds of quakes in Hawaii, and the Pahoa quakes were rather conspicuous by their absence. Do you happen to know offhand if there was any significant change to the long-term magma supply rate around the time Pahoa became as active as it is now?
BTW, you’ve make clear that you like the Kilauea lava lake, so be forewarned; if the lava lake goes missing (like it did in 1924) around the time you leave Hawaii, you’ll be suspected of having taken it home with you. 🙂
Regarding quakes that is definitely for Hector to explain, I mostly have looked at surface level stuff. But Pahala does seem to be a source to Kilauea, and despite what HVO says about it not being related directly to eruptions it is quite clear it has increased following the eruption in 2018.
The lava lake today has got a volume of 0.1 km3. Basically, it is the same amount of magma that if erupted explosively would be a decent VEI 4. The rate for 2021 was about 0.08 km3/year, a little lower than average suggesting magma going elsewhere. But now it seems the effusion rate despite frequent pauses has gone up to around 360,000 m3/day, or 0.13 km3/year, so it has evidently got its preferred path out.
Kilauea has got a history of really massive lava lakes, it makes Nyiragongo look like a puddle, the lake in the early 19th century was over 1 km3.
Did anyone mention about this volcano erupting in Costa Rica? This video was posted yesterday on YouTube.
https://www.youtube.com/watch?v=yH3OiNF67Jc
Not one I have heard much about.
Seems to be lost in the news. Thanks for the link!
Nice. East side of Pacific jealous of attention for west side – not to be taken seriously 😉
It must be famous on VC being a semi-finalist in the 2018 VC-Worldcup, take a look:
https://www.volcanocafe.org/volcano-world-cup-2018-semi-finals/
Was because it looked like a contendor for a future major eruption. There was even a point where there was a ‘lava lake’ there. I dont know if it was a real convecting lake or if it was a bit more viscous and strombolian, or if anyone ever saw it again, but was the first proof of magma on the surface there in over a century. Still, big eruption there is VEI 4, so not too bad but also rather unimpressive by our newly evaluated standards as of last week 🙂
Now that I think about it, probably any explosive eruption we see at any point this year is going to look rather unimpressive, the bar has been set high this year, maybe higher than it has been since 1883.
Concerning the forces involved (not measured in VEI, but in TNT) a comparison between Krakatau and Hunga Tonga might be possible.
Aside from that this comparison should be wrong. The Island Arc of Sumatra and Java is built on continental crust. It is an active continental margin and comparable to the Andes or also SE Alaska.
The Island Arc of the Tonga-Kermadec Trench though is an ensimatic island arc where the arc is built on oceanic crust. It can be compared to the Solomon Islands, the Izu-Bonin- and Mariana trench system, the outer islands of Japan and the Lesser Antilles – Martinique comes in mind.
Also the Philippines and Papua-New Guinea belong to the latter system. Mayon, Taal or Rabaul can do devastating eruptions, even when classified as a VEI 4.
Like I said before, basically every volcano that has got water in its crater in large volume – low elevation near the ocean. I think Mayon is not in that caegory though, but the others are. Taal I think could especially be prone to this,
Mayon and Ulawun are dangerous becuase they are steep, lava flows on their flanks disintegrate and turn to pyroclastic flows. Otherwise they would be probably just standard mafic volcanoes, pretty much just gigantic polygenetic cinder cones.
Thanks for the correction about Mayon. My dog’s tumour turned out to be benign today. It looked malignant, the vet and I had the same diagnosis in mind (mast cell tumour), but it is a benign thing. Just telling as you probably have a dog as well.
Lucky you Denaliwatch. our dog at around 8 years old had never had a days illness in all that time so when he stopped eating we took him to vet immediately. sadly we weren’t so lucky. The vet checked him over and says yes he is really healthy so we will just do some blood tests while you wait for the results as it’s odd a healthy dog stops eating. Sadly his blood count was so low it was almost off the scale so they thought he must have internal bleeding and asked to do a scan. Not good news. 3 tumours in 3 different organs so inoperable. I still miss that tough little dog. Amazing that even though he must have been in severe pain he never showed any sign of it at all. An English Fell Terrier, noted for being one of the toughest dogs.
Alicia, sorry for that. We lost one at the age of four (lymphoma), they didn’t let him wake up after consultation with his owners, my husband was present when they opened him up, and another one at the age of six (squamous cell carcinoma foot), so this time we are very lucky.
I actually dont have any pets, but that is good yours is ok 🙂
🙂
M 4.8 – TONGA – 2022-01-22 09:23:40 UTC
What is actually the observation most constraining the duration of the major energy release? I take that the days before the big blast are energetically not relevant. But what about January 15 itself? The satellite picture time series showing the formation of the cloud seem to point to a brief event. But how brief?
Dominik: I have looked at the satellite pictures in detail. I think that the big eruption continued spasmodically for several hours. Here are some of the details I have noticed:
The eruption’s umbrella cloud or anvil had a tall central fountain or overshoot that featured cloud top temperatures colder than -70 C at 5:10 pm, 5:20 pm and 5:30 pm. At 5:40 pm the cold central overshoot had disappeared or greatly diminished, but at 5:50 pm it was back again. The overshoot had disappeared again at 6:00 pm but was back a third time at 6:10 pm. After that, energetic rings of alternate cold and warmer cloud tops continued to emanate from the volcano, but with no central overshoot colder than -70 C. Around 7:30 pm the concentric rings seemed to disappear, and the anvil top became smoother. Just before 9:00 pm the concentric rings of cold and warmer cloud tops started to radiate from the volcano again after almost 1.5 hours of relative quiet. At 9:20 pm the cold central overshoot reappeared for the 4th time that night, with temperatures colder than -60 C, cooling further to -80 C at 9:30 pm and 9:40 pm. At 9:50 pm the cold central overshoot disappeared for the final time and the generation of those concentric rings from the volcano seemed to stop for good.
It seems that vigorous eruptive activity lasted for almost 5 hours, but with about 1.5 hours of relative quiet from about 7:30 pm until 9:00 pm. The most intense activity, including the generation of the tsunami and loud shock waves seems to have occurred in the first 30 minutes or so, but I wonder if later activity may have generated less atmospheric effects due to the vents being progressively further submerged under water. Possibly, the later activity continued to feature intense venting.
Thanks, this is exactly what I was looking for! Yes, it is interesting, atmospheric wave and ocean tsunami indicate short timescales, but the cloud looks quite dynamic
Thank you Dominik. I have a more detail summary about the satellite obs some distance below if you are interested.
Some of you have mentioned the persistant low level earthquake swarm near Langjökull.
I wrote about it in 2017, and since nothing new has come up I instead thought I would repost those articles.
The center is still directly below Skotmansfell volcano.
The only addendum worth doing, is that this is by now a dyke reaching up to the 4km marker, and that it seems to be going crustal margin up, and not from Ok.
https://www.volcanocafe.org/is-that-a-volcano/
Fagradalsfjall has got a friend, more tourist volcanoes 🙂
Would also give a more convenient place to see lava for those in Europe who cant as easily fly to Hawaii. Or those who wish to play with the lava and avoid an angry goddess 🙂
Ok is a really big shield though, so maybe this one has got quite some big potential. Eruptions in this area seem not to be long fissures or flood lava eruptions, just relentless slow flows of lava for decades, making massive shields. Ok looks like it was maybe even several volcanoes, two table mountains with a shield forming on top, in the last interglacial it seems. Maybe now is time for round 4.
Will start to count the quakes above the 4km mark then!
I am very much looking forward to this one. The eruption will be bigger than Fagradalsfjall, it will for sure be worth the trip with lots of other things to do around Ok: the area in the east is already in the highlands, absolutely spectacular! And further to the west there is the biggest hot spring of Iceland, also great for thermal baths. It is also used for hot water for lots of households on the eastern side of the island.
Many thanks for the article Carl. Even I (a bear of very little brain) could understand it!
Boiling the kettle will never be the same again…daydreaming of calderic flashovers.
Will say too, that I will definitely try to write an article about Kilauea after my trip.
I recently found out you can actually see the vent from the Volcano House too now, not just from Keanakako’i. It really is back into the old days 🙂
Oh this misplaced, was meant to be further up.
Looking forward to the article. 🙂
Fantastic article Carl, thank you!
Your article could explain the very brief and violent quakes we had in the vicinity of a deep geothermal plant here. Maybe the injected water (5-6km deep) got supercritical, and then part of it passed the flashing point when the plant tried to tap the pressurized water from the other well, lowering the pressure in the reservoir.
Could this “tapping” induce explosions in other geothermic fields as well? I never thought of these risks before. What they do in Italy would then be scary, like playing with matches in a petrol station! The first explosion could trigger a domino effect and destabilize the whole area.
Your group constitutes a great think tank.
Take care and stay clear of nasty waters 🙂
Hello Fred!
I do not know what plant you are refering to, and even if I did I would be reticent to answer on their behalf.
So, let me answer this from the point of physics.
It is all about energy, what you do when you tap energy is lowering the risk for an eruption, not increasing it.
The same goes for when you reinject water. You are introducing a cold liquid into a hot system, and that causes further lowering of the local energy reservoir, further decreasing the risk for an eruption or a flashover.
It is here important to understand that flashover can only happen if a large amount of overburden is suddenly removed, it is quite stable otherwise. Also, it requires supercritical fluids, something that most geothermal plants does not contain to begin with.
So, the earthquakes.
As you take out geothermal fluids you will have subsidence unless you reintroduce water at the same rate you are taking out the fluid.
This fluid is introduced under enormous pressure, and often in cycles of reinjection. During those cycles you have lots of water introduced, and that can at times push apart fractures around the reservoir causing earthquakes.
Depending on the depth of the reservoir these earthquakes can range from slightly irritating to a real nuisance.
But, they are almost never a danger if you have done your studies well.
I will be happy to answer any followup question.
After my brief access to that supercritical site the numbers have got me thinking.
Firstly above the critical point it has been stated that the latent heat goes to zero.
BUT there is a boundary between high density form and low density form, but its clearly something different from water-steam. Not least the high volume form appears to convert into the low volume form with little or no energy transferred. This means that the energy put into compressing the low density form goes into the ‘internal stress’ of the high density form. This implies that you can (simplistically) expand the high density form to the low without changing the temperature or pressure. I think its a difference in density and thus volume of ~10:1 to 30:1.
WOW. I can see why power engineers like it!
So lets imagine the volcano as a piston with weights on it (holding it down) containing the high density form at high temperature and pressure. Take a few weights off and the piston moves upwards but the pressure doesn’t drop, just some low density water is produced. The piston top accelerates up at constant speed but the pressure in the chamber doesn’t (much) change. This will prevent any layers beneath from seeing any change. Eventually the piston top is ejected from the volcano (possibly at significant velocity, and gas may well then vent supersonically). [At about this point deeper systems will notice a pressure change].
Now (maybe somewhat earlier) we are in a low pressure regime. The steam expands and cools and produces a mix of water droplets, liberating latent heat and the entire gas cloud goes upwards (because its hot, light and has significant momentum skywards) in a blast of hot raindrops and steam (the ash is important but rather inert). This will expand outwards as it goes, not least because atmospheric pressure drops with height. As it expands, more steam condenses and more latent heat is generated. Its essentially a hurricane without any spin.
Note that when all the steam is converted to water, a vacuum/reduced pressure pulse should form
How high it goes probably depends on how long the blast lasts, and whether its followed by more deeper decompressions.
The main shock wave (the pressure wave, not the supersonic crack) seems to be about 30 mins, followed by a 30 min negative pressure. If we are going up to 30km ish that’s about an ascent rate of 60km/hr ave, which is quite a bit. Alternatively if its a 30 min eruption, that seems to me to be quite long, although putting figures into a f=ma calculation may show it to be reasonable.
Anyway, how I see it right now, subject to corrections.
“WOW. I can see why power engineers like it!”
Ding! Even geothermal volcanologists love it 😉
HUNGA TONGA’S GREAT ERUPTION MAY HAVE LASTED FOR HOURS, AND MAY HAVE BEEN PRECEDED BY A SMALL ERUPTION AN HOUR BEFORE…….
The following observations were gleaned form observation of the Himawari-8, GOES E and GOES west visible and infrared satellite images……..
-At 3:50 PM Local Tonga Time on Saturday Jan 15 a narrow towering cumulus updraft suddenly appears above Hunga Tonga casting a dark shadow across the sea surface to the E. The shadow is several km long.
-4:00 PM A clump of towering cumulus drifts off Hunga Tonga casting a shadow more than 10 km long across the sea surface to the E.
– 4:10 PM The clump of cumulus drifts ESE and dissipates, evaporating with time and leaving a narrow cloud street of smaller cumulus extending ESE from the volcano.
– 4:20 PM The south edge of a regional blob of cumulus and stratocumulus crosses the volcano moving ESE, obscuring the island.
– 4:30 PM The south edge of a regional blob of cumulus and stratocumulus continues to cross the Island, moving ESE.
– 4:40 PM It starts to clear at Honga Tunga as regional cloud blob moves away.
4:50 PM a cumulus cloud appears over the island.
5:00 The island has suddenly disappeared behind a large 10 km wide bank of low topped but tightly convoluted cumulus cloud.
5:10 PM A giant, towering cloud has risen above Honga Tunga and has grown to about 30 km wide. The dark shadow extends across the sea surface to a distance of about 55 km E.
5:15 The giant cloud shadows the sun on Kelefesia, about 70 km east of the volcano.
5:20 The giant cloud is now about over 100 km across. The south edge of the anvil is almost to Nukualofa
The eruption’s umbrella cloud or anvil had a tall central fountain or overshoot that featured cloud top temperatures colder than -70 C at 5:10 pm, 5:20 pm and 5:30 pm. At 5:40 pm the cold central overshoot had disappeared or greatly diminished, but at 5:50 pm it was back again. The overshoot had disappeared again at 6:00 pm but reappeared for a third time at 6:10 pm. After that, the anvil top continued to show energetic rings of temperature fluctuations that radiated from the volcano, but with no central overshoot colder than -70 C. The concentric rings in the anvil seemed to disappear around 7:30 pm when the anvil top became smoother.
Just before 9:00 pm the concentric rings radiating from the volcano reappeared after almost 1.5 hours of relative quiet. At 9:20 pm the cold central overshoot reappeared for the 4th time that night, with temperatures colder than -60 C. The central overshoot intensified after (9:20 pm), cooling further to -80 C at 9:30 pm and 9:40 pm. At 9:50 pm the cold central overshoot disappeared for the final time and the generation of those concentric rings from the volcano seemed to stop for good.
Based on these observations it seems that vigorous eruptive activity may have lasted for almost 5 hours, but with about 1.5 hours of relative quiet from about 7:30 pm until 9:00 pm. The most intense activity, including the generation of the tsunami and loud shock waves seems to have occurred in the first 30 minutes or so, but I wonder if later activity may have generated less atmospheric effects due to the vents being progressively further submerged under water. Possibly, the later activity continued to feature intense venting.
One last observation about this eruption that may be important is the timing of the shock wave. The loudest shockwave in Nukualofa seemed to occur at about 5:22 – 5:24 PM. This is obtained by the timing of arrival of the south edge of the umbrella cloud overhead in Nukualofa estimated from satellite and the occurrence of the loudest shockwave at about the same time as the arrival of that cloud edge. If the timing of the shockwave in Nukualofa is correct, the volcano produced it at about 5:19 – 5:21 PM. At that time the volcano had already been erupting for 20 minutes or more, indicating that the most powerful blast may not have occurred right at the beginning of the eruption.
Please look at the second version of this summary below………I had to make a few small corrections. Sorry.
An argument for the idea that the movement of the plates is caused by gravitational forces of the sun and moon, a topic often discussed here.
https://phys.org/news/2022-01-sun-moon-plate-motions-imbalanced.html
HUNGA TONGA’S GREAT ERUPTION MAY HAVE LASTED FOR HOURS, AND MAY HAVE BEEN PRECEDED BY A SMALL ERUPTION AN HOUR BEFORE…….
The following observations were gleaned form observation of the Himawari-8, GOES E and GOES west visible and infrared satellite images……..
– At 3:50 PM Local Tonga Time on Saturday Jan 15 a narrow towering cumulus updraft suddenly appears above Hunga Tonga casting a dark shadow across the sea surface to the E. The shadow is several km long.
– 4:00 PM A clump of towering cumulus drifts off Hunga Tonga casting a shadow more than 10 km long across the sea surface to the E.
– 4:10 PM The clump of cumulus drifts ESE and dissipates, evaporating with time and leaving a narrow cloud street of smaller cumulus extending ESE from the volcano.
– 4:20 PM The south edge of a regional blob of cumulus and stratocumulus crosses the volcano moving ESE, obscuring the island.
– 4:30 PM The south edge of a regional blob of cumulus and stratocumulus continues to cross the Island, moving ESE.
– 4:40 PM It starts to clear at Honga Tunga as regional cloud blob moves away.
– 4:50 PM a relatively small cumulus cloud appears over the island.
– 5:00 The island has suddenly disappears behind a large 10 km wide bank of low topped but tightly convoluted cumulus cloud.
– 5:10 PM A giant, towering cloud has risen above Honga Tunga and has grown to about 30 km wide. The dark shadow extends across the sea surface to a distance of about 55 km E.
– 5:20 The giant cloud is now about over 100 km across. The south edge of the anvil is almost to Nukualofa
The eruption’s umbrella cloud or anvil had a tall central fountain or overshoot that featured cloud top temperatures colder than -70 C at 5:10 pm, 5:20 pm and 5:30 pm. At 5:40 pm the cold central overshoot had disappeared or greatly diminished, but at 5:50 pm it was back again. The overshoot had disappeared again at 6:00 pm but reappeared for a third time at 6:10 pm. After that, the anvil top continued to show energetic rings of temperature fluctuations that radiated from the volcano, but with no central overshoot colder than -70 C. The concentric rings in the anvil seemed to disappear around 7:30 pm when the anvil top became smoother.
Just before 9:00 pm the concentric rings radiating from the volcano reappeared after almost 1.5 hours of relative quiet. At 9:20 pm the cold central overshoot reappeared for the 4th time that night, with temperatures colder than -60 C. The central overshoot intensified after (9:20 pm), cooling further to -80 C at 9:30 pm and 9:40 pm. At 9:50 pm the cold central overshoot disappeared for the final time and the generation of those concentric rings from the volcano seemed to stop for good.
Based on these observations it seems that vigorous eruptive activity may have lasted for almost 5 hours, but with about 1.5 hours of relative quiet from about 7:30 pm until 9:00 pm. The most intense activity, including the generation of the tsunami and loud shock waves seems to have occurred in the first 30 minutes or so, but I wonder if later activity may have generated less atmospheric effects due to the vents being progressively further submerged under water. Possibly, the later activity continued to feature intense venting.
One last observation about this eruption that may be important is the timing of the shock wave. The loudest shockwave in Nukualofa seemed to occur at about 5:22 – 5:24 PM. This is obtained by the timing of arrival of the south edge of the umbrella cloud overhead in Nukualofa estimated from satellite and the occurrence of the loudest shockwave at about the same time as the arrival of that cloud edge. If the timing of the shockwave in Nukualofa is correct, the volcano produced it at about 5:19 – 5:21 PM. At that time the volcano had already been erupting for 20 minutes or more, indicating that the most powerful blast may not have occurred right at the beginning of the eruption.
WOW! Thanks for this. I did start to try and sort out the details, but it was a lotta work, so stopped.
Its unclear to me whether you think an eruption started at 3.50pm but was small. You do not comment on the cloud colour. I presume you assume this to be a mostly phreatic small initial eruption.
3.30 to 5.00pm a small eruptione mostly steam?
5.00pm it blows. Very significant energy emission starts.
5.20 the sonic boom and shockwave occur.
7.30 the main eruption seems to end
9.00-9.20 final weaker eruption.
So we need to be able to explain (handwavingly for the moment) this sequence of events.
What do we know about a hot water column filled with rocks and hotter at the bottom?
1) The top is just superheated water. If it flashes to steam much of the energy goes in the latent heat of evaporation (as Carl mentioned). So we might guess that the initial eruption(s) are common or garden phreatic eruptions caused by ordinary pressurised steam. This might be partly powered by the deep wet supercritical water mass but this stays supercritical (note it can expand quite a bit and still stay supercritical). We consider that ejecting large amounts of mass vertically results in a recoil, increasing pressure on the eruption base. Amount to be calculated…
2) A little before 5.00pm pressure in the conduit (which is likely ~sq km across) drops enough that the supercriticality of the deeper layers fails, and it commences a rapid expansion.
3) The high pressure high velocity steam reaches the atmosphere to produce a shock wave (this is probably NOT the 30 min one circulating the globe, which may have started earlier) as supersonic gasses produce a sonic boom.
4) Various internal parts of the volcano erupt as and when.
Question: Shock waves.
We have three.
1) A ~1 sec pressure wave that knocks peoples breath away.
2) A sharp sonic boom shortly afterwards.
3) A triangular pressure wave of about 30min abruptly switching to a 30 min vacuum wave and no others suggesting a large singular and unusual event.
What is the timing of (3) at the source?
Thank you for your reply. I do not think the volcano was erupting continuously before 5:00 pm, but there may have been a short “puff” of activity around 4:00 that generated the narrow but tall cumulus updraft. It may have been quiet then until a minute or two before 5:00 pm. At that time something very energetic had started at the volcano because in almost no time there was a billowing bank of very dense “cement” cumulus maybe 10 km wide (but not very tall). By 5:10 there was a very tall cloud probably all the way up to the stratosphere already, and that cloud was already about 30 km wide. By 5:20 the umbrella cloud had grown to about 100 km wide. To create a cloud 100 km wide, the first 20 minutes of the eruption must have been very intense, much more so than the eruptions of the day before. However, the loud shockwave caught on several cameras and phones in and just along the N shore near Nukualofa seems to have been produced around 5:20 pm AFTER what had already been about 20 minutes of very intense eruption.
I found it difficult to gauge the cloud colours, but any ash might have been so rimmed by ice that the clouds looked rather like ordinary meteorological clouds from the top of a tall tropical convective system anyway.
The timing of the tsunami is important, but I do not know it. It is claimed that it arrived in Nukualofa around 5:30 pm but it probably made slow progress over the last 10 km or so as it had to drag across that much coral reef and shallows before reaching Nukualofa. The tsunami seemed to arrive after the loudest shockwave…10 min ? but I wonder if it was initiated before the loudest blast as I don’t think the tsunami could get all the way to Nukualofa in 10 min, or even close. The timing will have to be verified more exactly to draw conclusions.
This volcano makes the best jokes on the planet😂 Lengai really is the perfect place where Vader and Jabba The Hutt can boil Han Solo to death … carbonite… hummm Natrocarbonatite 🙂 carbonatite
https://m.youtube.com/watch?v=qputaVyn7TE&fbclid=IwAR03DhwpIv_uYZrYl9zUq2A6muaKBO9Ht3uHB4XtRSfUD0fyY27h-gRfsCY
Big loud deep booming huttese voice
”Han! …. han .. You are going to Lengai solo!” and Solo is escorted by vaders stormtroopers to Lengai
> Drowing him in a pool of Natrocarbonatite < Blub Blub blub
Hmmmm hughuhuhäh Jabba laugther
And later he is delivered in a white block of Natrocarbonatite to Jabbas Palace
Steam explosions brought my mind back to the relatively recent tragedy at White Island and a scary thought occurred to me; could there be enough supercritical water in there to produce an explosion this massive as well?
Three differences (maybe more): 1. Smaller, 2. Smaller crater lake. 3. Continuous emission of gas, observed since Captain Cook visited it.
Other things to consider
White island has a Dacite component which gives it more potential
Although all historic activity has been andesitic
Also as it has been active continually for hundreds of years it is thought to have many tens of km3 of magma potential
It is a nasty piece of work
Not sure it being dacitic would increase the potential, if anything basalt would be worse because it is a lot hotter, and more porous as a rock too. I guess maybe we are skewed a bit by Krakatau being a silicic volcano before 1883, so until now that is all we had to go off of.
On that subject though, it in theory would not be impossible for Anak Krakatau to already repeat the actions of its parent.
I’d say the scarier part is knowing how long it’s been since it had a proper magmatic eruption as opposed to sporadic phreatic explosions. Hell, even if there is a small to moderate undisturbed pocket of supercritical water, it being triggered could be even more devastating than the last tourism disaster there.
Crater is not very elevated from surrounding Ocean
So that is another danger
That during a major eruption sea water could easily flow in there
It indicates that the coastline of the Bay of Plenty in New Zealand has a greater tsunami risk than expected as this type of activity could occur without any warning of it
Not just white island also the submarine volcanoes extending to the kermadecs
A local news service restored on Tonga:
https://matangitonga.to/2022/01/22/were-back-limited-coms
Many thanks for the article. I think it is overplaying the role of supercriticality a bit, though. What matters is the energy content – and high-energy water often happens to be supercritical. It is nasty because there is so much stored energy, not because it is supercritical. Would it make a big difference if water was initially at, say, 800 degrees and 250 bar (fancy supercritical) or at 200 bar (bog-vanilla superheated)? I doubt it. Anyway, when hot, supercritical water expands, it becomes “normal” steam when the pressure drops below 221 bar.
Actually, if you take ice-cold water and pressurise it above 221 bar, there you have supercritical water. Not very exciting but if you start heating it up, it no longer has a distinct boiling point. Eventually, it’ll have a smooth transition from “water-like” dense state to “steam-like” much less dense state. The higher the pressure, the smoother the transition.
What is possibly even nastier than high-energy water, is wet, hot mud. Expanding steam cools quickly but hot solids can release energy and keep steam hot longer causing it to expand more. In the process the hot solids get a part of the energy and get accelerated. (e.g. maars?)
Now, the fact that Hunga-Tonga was a steamy eruption suggests that there may indeed have been something like high-energy aquifers that blew off. Is it because of wet magma and a long settling time or is it due to water ingress? Hot water is buoyant, so if there are impermeable layers, aquifers could form.
“Actually, if you take ice-cold water and pressurise it above 221 bar, there you have supercritical water.”
No.
That is bogstandard water under pressure equal to 2.2km of depth.
It is not supercritical until heated to the point of gas/fluid equilibrium.
Super-chilly water.
“Actually, if you take ice-cold water and pressurise it above 221 bar, there you have supercritical water…”
Now I have this picture of the deep oceans suddenly exploding for no logical reason.
Life on Earth is seriously dodgy.
Very hard to explode supercritical water. You don’t get explosive eruptions more than 2km down: the water refuses to cooperate. And if your reduce the pressure, the expansion will reduce the temperature and turn it back into liquid water unless the starting temperature is very high. Black smokers are supercritical hot water. They are black because supercritical water is an excellent solvent, and because supercritical water is very turbulent. The black water rises because it has a lot lower density than the surrounding, colder water. As it rise to drops below the pressure of the critical point, turns into normal water, stops rising and the dissolved material drops out again, back to the sea floor. That may be a kilometer above the exit point. Carl proposes that the pressure comes from the rock, not the water, and disappears suddenly. If the water is hot enough, it can turn into a gas on removal of the pressure. It needs to be hotter than a black smoker. This means you can heat the water slowly, to prime the explosion. It also means you get less explosive energy because critical water does not expand as much on becoming a gas (it is already low density to begin with). Against this, you can have a much larger volume of water as you it is much better at taking heat from the surrounding, and you can heat it up at a bit more leisure. My main uncertainty is whether you can get a big enough shockwave at the surface for the immense sonic boom. That would seem easier to make with an explosion closer to the surface. I can’t tell.
I believe you are talking the enthalpy of water here? I looked this up and found the following results
Ref: https://www4.eere.energy.gov/manufacturing/tech_deployment/amo_steam_tool/propSteam
Pressure Temperature Specific Enthalpy Specific Entropy Phase / Quality Specific Volume
psig °F btu/lbm btu/lbm/R ft³/lb
3,625.9 1,472.0 1,738.4 1.655 Gas 0.302
2,900.8 1,472.0 1,748.6 1.684 Gas 0.380
The first is 250 bar at 800 deg C, then 2nd is 200 bar, 800 deg C
Curiously and to my surprise the enthalpy goes down slightly for 250 bar as compared to 200 bar pressure
But it doesn’t look like much change here.
You need to play with the figures a bit. From memory circa 300C and 300bar you will find an area where there is a sudden drop in density with small changes of pressure or temperature. The area where I was looking the factor was about 15x. Elsewhere its said that above the critical latent heat falls to zero although in fact IMHO it becomes negative in that it takes more energy to go from a gas to a liquid rather than less. I imagine that the kinetic energy in the gas phase is less than the elastic energy in the liquid under pressure. What you have is a volume of immensely compact energy if conditions are right. You are way into the gas phase at 800c and only 200bar.
I did post a chart back a bit (maybe previous post) but sadly its mostly too high pressures for this event.
Not that it’s terribly relevant in this context, but if you keep increasing the pressure on that cool water you get some of the more exotic forms of ice:
https://en.wikipedia.org/wiki/Ice#/media/File:Phase_diagram_of_water.svg
But this only happens at extreme pressures (>10 kbar). If you increase pressure to around 1 Mbar then even the supercritical water turns to ice.
For the energy budget, I have to say I also doubt if the distinction between “supercritical fluid” and gas is by itself relevant. As also Albert commented above, it does not mean having a maximum of energy density. Funny things happen close to the critical point (mostly with respect to ability to dissolve stuff), but honestly, farther above in T and p, a supercritical fluid behaves like a gas. Actually, that is one of the defining properties, that it can be treated well with the ideal gas law. Simple example, the air or nitrox in my scuba cylinder is actually a supercritical fluid.
Actually supercritical (steam) not anything to do with the triple point, is interesting stuff and behaves nothing like water does at lower pressures. You should do a little research on it as I had to, to find out its quite strange. The basic difference is that as you put energy in by compressing it, basically the temperature doesn’t change, all the energy goes into converting the vapour phase to liquid phase. Sadly it seems to be only expressed in terms that high pressure energy engineers are familiar with, that is its a specialist niche area in a specialist niche area.
I am presuming the water molecules have their 120 deg bonds bent significantly to pack in at higher density so they all act like springs ready to rebound if space is available. Its a liquid so there is limited bonding between the molecules.
Interesting stuff.
Hydrogen bonds become much less important at these pressures. The hydrogens are mostly unbonded. Normal water cannot expand much: the density is nearly the same at all temperatures. Supercritical water can expand, and has a much lower density than normal water. It is not a gas but it is not a liquid either.
Well…”not a gas”…I mean, away from the critical point, the behaviour ist for all practical purposes gas-like. As I said, compressed air at 200bar and room temperature is far in the supercritical regime. Everyone calls it a gas, and as when breathing the cylinder down, one never comes close to either the critical point for either nitrogen or oxygen (both at T far below diving in liquid water), nothing strange happens when the respective pressure is passed. All I am saying is that unless there is a strong argument that the water was close to the critical point in the system of the volcano, I do not really see what a supercritical state in itself has as a relevance here. The energy density is high at such T and p, and this energy will be released when decompression happens. Isn;t the the basic point?
Yes, that is the issue with this model. It is not easy to get enough energy out. Against this, it is much easier to quickly heat a large volume of water. Perhaps the answer is in between: use supercritical water to extract the heat, use its buoyancy to transfer the heat to higher levels, and so prime the eruption.
Its being close to the critical LINE, at least for water. Really its liquid and gas in close proximity temp and pressurewise. Far from the phase boundary its one or the other (as you comment) and if you read some of the texts online many stress this fact. The critical point seems to be defined as the point where the latent heat of evaporation becomes zero. However past that line there are still two density phases that can be in equilibrium.
So your supercritical gas cylinder, if you allowed it to expand adiabatically would COOL as it expanded and much of the energy becomes kinetic energy in the gas. Supercritical water though (in that region) may even get hotter as it expands and the pressure go up because the elastic energy between the molecules is greater.
For thermal power engineers they seem to operate at insane temps (~600c in some plants) and huge pressure so they get a large delta-T and becaise the density is high, a lot of power from a small turbine.
Albert.
I think its exceedingly hard to quickly heat a large volume of water.
Its vastly easier to slowly heat a large volume of water.
Water is not a very good conductor and nor is rock, as we have seen from countless eruptions. Indeed I am beginning to wonder if the periodicity of phreatic eruptions is as much collecting and heating the water at depth as sudden injection of magma, although that may tip it over the edge.
It explains why phreatic eruptions rarely have any precursors suggesting a sudden influx of magma, it because that’s not how they are caused.
To be honest anything deeper than 1 km is suspect.
PS These do not have to be supercritical, just to have a tipping point, ie hysteresis.
That’s how I had it until I looked carefully. As the supercritical sites keep,pointing out supercritical doesn’t mean there are not phase changes. There are zones with low and high densities close together and where I was looking (in the 1,5 to 3 km seawater depths) it was circa 300C (from memory). The ‘liquid’ phase being @700kg/m^3.
I think for ordinary scientists (like me) we tend to take the ‘critical point’ as being close to the triple point but the thermodynamic engineers seem to use the point where latent heat drops to zero, however its clear it goes negative from the behaviour around the critical line. After all why should it drop to zero and stop since at atmospheric pressure the latent heat is just the kinetic energy in the gas molecules.
PS Do all gasses go through this regime? You are suggesting its a battle between kinetic energy and direct oxygen electron cloud repulsion. You could do it with (say) argon.
farmeroz, triple point and critical point are not at all the same, and actually for the substances we are dealing with, the are quite far apart in the phase diagram!
I am as always amazed at the tangents that the crowd in here can amble off towards. 🙂
I did not expect everyone to start studying supercritical fluids in an attempt to receive impressively tall victorian stovepipe hats. I do though wholeheartedly approve of this. 🙂
Just a few points here.
1. The reason I wrote about supercritical water is not because I wish it to be there, it is because it is what is most often found when you drill down into large caldera volcanoes.
2. Albert is quite correct (as per usual), if this had been superheated water it would have been even boomier.
This is interesting, and worthy of a small sidetrack. It is fully possible that this was in play on the 14th and aided with excavating that first impressive hole.
3. I specifically talked about supercritical water here, not other things like diverse gases used when diving, that can be compressed into a supercritical fluid.
4. Once more, icecold water will not become supercritical water if compressed enough. It will not even compress as such until you reach compression levels that turn it into ice, or even metallic water.
You need to introduce heat to reach supercriticality. Obviously you could produce superhot supercritical metal-water that would be able to flashover… but once again, this was not the scope of what I wrote in the article. 🙂
Off to find an online stovepipe shop.
Edit: Not even if your non-compressed icewater dropped from 221 Bar down into zero pressure (vacuum) would cause flashover, it would still just happily boil away into steam in the regular manner. Remember that water is a non-compressible fluid (well, per definition in it’s normal state).
Edit 2: It seems to be hard to find a suitably impressive stovepipe. I found this, and I am seriously pondering making it a part of company dresscode.
https://www.hatsandcaps.co.uk/products/jaxon-james-victorian-top-hat-black
Carl, it may well be that the water actually was in the supercritical regime. I and several others were just pointing out that your article seems to give the impression that there is something about the energy density in the supercritical state that would be specifically needed to produce such an event. There is not, at least not the extend I can see at the moment.
The part
“This is the only form of water that could have caused the explosion at Hunga Tonga. There may have been other more normal forms of water involved, but they lack the energy density to produce that kind of explosion.”
is in this regard really not ideal, and you say that yourself with your point 2. The energy density could have been even higher without being in the supercritical regime. It may however be that this was not in the cards from the beginning, as pressure and temperature may have forced supercriticality.
It was probably not ideal if read in that manner.
When you write a seven page long article on something that is your daily bread and butter you tend sometimes to assume that everyone will follow your line of thought. 🙂
“It may however be that this was not in the cards from the beginning, as pressure and temperature may have forced supercriticality.”
Ding! You got it! 🙂
It was not meant to be overly critical or to sound smart. No need to see it that way really. As I said from the beginning, enjoyed the article!
Oh, I did not take it that way.
I thought it was a fun discussion. 🙂
I was thinking about Krakatoa, a different eruption because it blew apart much more island, but with a similar chain of events. Its island had 500 meters (or more) of rock above sea level. Any sea water flowing in to the conduit would be under pressure above the critical point just from the weight of the island. The final, enormous explosion involved water (we know this because the ash fall afterwards was wet, while all earlier ash had been dry). Any water in the magma chamber or deeper conduit would certainly be supercritical. But the explosion was off centre (from the crater it left), perhaps on the edge of the island. A flank collapse could have opened the flood gates for the cataclysmic event. Bottom line: Krakatoa will have involved supercritical water. Whether that was enough to power the eruption is not clear, but the model that I had in the previous post and Carl’s model here are not far apart. Both require water stored under pressure, not just water suddenly poring in.
A final comment on the VEI numbers. That scale was meant to measure the explosive energy. A lot of the arguments involve what the energy was used for: part of it into fragmenting rock (tephra), part into boiling water (height of the plume), part into the atmosphere (sound and pressure wave). We just want the total energy from all these, rather than separate scales for all three. I have my opinion of a high VEI-5 but am happy to be convinced otherwise! The height of 55 km (confirmed by three groups for the centre-most column) shows that a lot of the energy was used for putting heat into the atmosphere. Very impressive. It also suggest that, indeed, less energy went into the solid rock.
If there was a bigger island
This eruption would have probably blown that island away as well.
Can only blow away what is there to begin with
That is the issue with the nasa energy required to remove island theory
There was more than enough to remove that island and much more
Albert, thing is still, energy is integral. The timescales of different eruptions are quite dissimilar, no? An event that dissipates 50MT TNT of thermal energy over 9 minutes will look dramatically different from one that dissipates the same amount over 9 hours.
That being said, can you give us your personal “energy boundaries”? You say what we observed was a high end VEI5 in your opinion. Where does then VEI5 end in terms of total energy release, and where does VEI6 begin?
That is an excellent question. The VEI scale was original ‘semi-quantative’, so partly descriptive, partly approximate numbers. We have always focussed on tephra volume as it is measurable. That has become an absolute scale over time, but it was originally just one of the proxies. The VEI scale never used energy, so what we need is it recalibrate it. St Helens, a VEI-5, did 24 MTon TNT (I do not like this unit!) of thermal energy, and 7Mton went into the blast wave. St Helens wasn’t that ashy: only about 1km3, so on that measure a low VEI-5 (the landslide that triggered the eruption was several times larger than the eruption itself!). It had an eruption column of 24 km, which is well into the VEI-5 range. I had been comparing the events to St Helens and it seemed several times larger based on the eruption cloud, so that gave me a higher VEI-5..no sophisticated calculations involved!
But to get the total energy of an eruption is complex calculation, and it requires data that was not available for older eruptions. You won’t find a decent number for say Tambora (you will find a number but it is not decent). You need to measure the thermal energy and the kinetic energy, plus any other energy forms that may be relevant. I can find very places where these calculations are done. These papers do point that you need to divide by the length of the eruption, in order to get a measure of ‘explosiveness’.
I think the main difference in our models is that I am hot water centric.
It may come from me coming from the cold of Northern Sweden, I want as much hot water as possible.
I see it as we covered the same coin from two different sides.
Another question: Could it be that without significant amount of water involved the VEI-scale is in fact a very good parameter, but when it comes to phreatomagmatic eruptions it doesn’t work any more?
The following paper says that craters of pheatomagmatic eruptions are by a factor of 2,5 larger than craters of purely magmatic eruptions (of comparable volumes I guess). Therefore the energy involved is larger.
https://www.edu.kobe-u.ac.jp/fsci-volcano/97grl.pdf
Albert, I am not fixed on MT TNT as energy measure. It is in a way however really useful here, as the discussion started with the pressure wave, and nuclear explosions are an obvious comparison. But Joules or ergs will also work.
I mean what do we know already? The number Carl had for the pressure wave — 50 to 60 MT TNT — seems solid. But that is really the energy needed for the pressure wave alone, not at all the total energy, as also a quick comparison to Tsar Bomba (58 MT TNT total energy, but weaker pressure wave) shows. So on top of that come thermal release, turbulence, fractioning of rock, bulk movement of tephra, the tsunami(!!) and other things. Quite a task to add that all up, but one should try. I do not know how solid either the 24MT TNT thermal or 7 MT TNT blast for Helens are, but maybe the respective ratio could be roughly similar(?)
Carl your reference put me in mind of the only photographic record of the Volcanocafe members’ symposium for Krakatau. Ladies of a nervous disposition may wish to avoid…
https://images.app.goo.gl/fp3ugFtiF3a6Wajk7
Bwahahahahaha!
I needed that laugh!
I remember it well. An explosive event
For the ladies, Albert was dapper in his stovepipe.
Interesting article. Sorry, only just had time to read it.
If I understand it correctly, Carl is saying that the 15 January 2022 eruption was phreatic. A bigger bang than its on land equivalent because sea water was involved.
There is new magma entering the system. If the eruptions from late December 2021 onwards were throat clearing, what happens next?
Not really, what I pointed to was that the water was most likely already there in the form of meteoric supercritical layers.
Having had a walk, and bearing in mind comment and criticism above, how about the following scenario:
After the earlier eruption (100 years ago) the volcano has the x-section of a maar (see web).
That is its a rough cylinder 2-3km deep and 1-2 km wide.
Its filled with wet debris from the earlier eruption.
At the bottom is the magma chamber which does what its been doing for 1000’s of years and that is extruding sills and dykes into its overburden.
These start heating the bottom layers and over time penetrate upwards (and sideways if there is a lateral weakness) heating the water in the surrounding debris/rock.
So we have a perfectly stable (considering depth) column of hot wet rock hotter at the bottom than the top.
For its pressure location its all well in the liquid phase at a few hundred C.
However due to the pressure the water is above the critical region and it is absorbing lots of energy to keep it hot and liquid. That is its in the phase diagram where is has (increasingly) a negative latent heat.
Eventually the dykes reach the surface and an eruption starts, lots of water involved but magma flow is quite modest (as its been for the last 100 or so years). However the entire system is heating up.
These are phreatic, and relatively close to the surface and when they happen pressure deeper down is REDUCED, stopping the eruption, they act as a pressure relief valve.
Eventually significant eruptions 20/12/21 and 13/1/22 reduced the pressure such that part of the deeper layers became supercritical. In this state if allowed to expand they produce gas phase, and the liberated energy results in an increase in temperature and pressure. This flows up the conduit and is seen as a burst of steam 3.30-5.00pm. Meanwhile its getting hotter and the pressure is increasing at depth.
By 5.00pm the pressure is enough to start to blow open the conduit (‘clearing the throat’) and initiate the start of the major eruption, ejecting part of the conduit and a lot of steam high into the atmosphere.
After 20 minutes the temp and pressure at depth have risen enough to blow the top off and we have one pressure wave and the sonic boom.
The energy remaining then vents in the normal way until there is insufficient energy to continue.
The hole is filled with wet rock and debris, and the magma chamber starts to heat the bottom up….
Please note that I have not attempted to downplay any of the observed phases to bolster the argument.
I am very happy for someone else to come up with a better explanation of ALL the observed events.
Most explosive events rely on an energy source collecting energy for a long time and discharging it through an event with positive feedback.
Others have noted that this explanation explains the low SO2 and ash content and the unusual height(s) of the column.
Hunga Tonga tends to erupt in pulses so 15 January may not be the end of the episode; the next few days are apparently crucial. Tonga does not have any active seismometers so they cannot monitor Hunga Tonga as well as we all might like.
Source: https://www.sciencenews.org/article/tonga-volcano-eruption-history-south-pacific
I don’t understand this instead as there are lots of 4,5-4,9 earthquakes registered there in the last few days, also collected by Hèctor her on this post I think. And documented also on VD. This made me think that possibly nobody would go near there at this moment.
Magma movement tends to produce a lot of smaller earthquakes too. If there are only 4.5 – 4.9’s being reported, there may be a lot of smaller earthquakes that are not being reported. Lack of active seismometers in Tonga could explain why the smaller ones are not being reported (assuming that they are normally reported internationally); the larger ones would be detected by more remote seismometers.
Farmeroz,
Having no walk, but taxying one of mine to an airport a bit away I had time to think too. I believe you can think about this for hours.
Your construct could be right. I myself am tending to “jesperize” it. If I assume that Tonga (main island) is the southern border of a large oval-shaped caldera, Going down from Neiafu to Tonga then all of those submarine hills would be sitting on a caldera rim. Any similar structure? Maybe Long Valley, having been sitting under water numerous times. So, what created the caldera then more than 80 Ma? The same structure maybe that created Mount Osbourn some 78.8 ± 1.3 Ma, so the Louisville hotspot. Too far off? Maybe. Bit if I want to I can see it. Missing as usual: evidence by field work which has just started not too many years ago and became more interesting in 2015.
One thing is sure though: The subduction of Mount Osbourn should create some trouble. And there are now and possibly all the time lots of earthquakes in the area north of the collision point, at the moment some more, all around 4,5-4,9. Beginning on Christmas Day though there were numerous earthquakes for around two weeks in the region of 5-5,9. Maybe that is what has to be looked for in the future.
On the other hand Tonga, the main island, might also be the southern rim of a smaller caldera as there seem to be many of them.
Anyway, comparing it with Campi got me there (“jesperizing” it, and Jesper added Benham Rise to that). So, your walking and my driving thoughts don’t even exclude each other mutually, thinking of that scarface of Campi.
Sorry, I cannot follow your sequence of events.
I understand that.
Generally, thinking of large calderas we can see I am just wondering whether in the early geological history there might have been many more of them, huge volcanoes like on Mars then collapsing into calderas as, contrary to Mars or Venus, there was water, at least water that staid there in the form of water (there might have been water on Mars and Venus too), and then there was plate tectonics.
But you don’t have to follow this although in the future more structures like Apolaki may be found. Bathymetry is not so old, and besides it is expensive. Considering the size of the largest tectonic plate on Earth and further considering that most of Earth is covered by oceans we only know a tiny part of it.
I’m more digging around in the depth, studying books (slowly) like “Discovering the Deep” which is more about the Eastern Pacific Ocean and some place in the Atlantic ocean and primaryly about bathymetry. So, that’s a totally different viewpoint, gives you totally different thoughts, has nothing to do with yours, but very much with Japan, which is why I have a Japanese book lying around. That is really hard though. I will have to leave this site for a long time if I want to learn Japanese. It would certainly take four hours a day.