Lava rocks! (republication)

/ 15/01/2022

While we are waiting for more information (and daylight) on the large Pacific eruption, here is a repost. It complements the previous post on igneousity (for which surely the ig-nobel prize was invented?). Enjoy.

Built on lava rock

What’s in a name. Would lava by any other name smell as sweet? Perhaps that is not the right question: lava is many things, but sweet-smelling it is not. It smells like a rose bush that was doused in some evil sulphurous pesticide and then put on fire. This rose also constantly explodes with a roar well above the legal maximum. No, Shakespeare’s rose is definitely the wrong analogy. The course of true lava never did run smooth.

But in geology, names are everything. The number of different minerals is staggering, and each has a different name which normally reflects its point of discovery rather than implying anything about the composition. Olivine has nothing to do with olives and perovskite is not a rock band. Do you know your cryolite from your kryptonite? How is your appetite for apatite? Studying geology must be like learning Inuit.

Volcanic rocks share this nomenclaturic nightmare. What on earth is rhyolite? What happened to komatiite? And what stuff is tuff? Even google can get confused: ask for amygdale, and it gives the right definition but images of something completely different. At least it knows not to show images of amygdala (which might require that you confirm your age). But for all of you who were confused but afraid to ask, here is help. This post gives all you need to know to understand the variety of rocks from lava, or at least help you speak like you do. Welcome to the club. We all bluffed our way into geological volcanology.

Lava is molten rock. At the end, it solidifies back into rock. So you should get back what you started with, right? Wrong. Just imagine a block of ice. Melt it, vaporize it, and let it condense and freeze, you may get snow. Both are solid water, but that is all they have in common. So too with rock, although with much more variety.

So let’s have a look at why not all lava is the same. For most of the images, if you click on them you will get full resolution. All the poor ones are from my own collection.

Basalt

Basalt. Photo by the author

The type specimen of volcanic rock is basalt. It is effectively mantle material, which was melted at the bottom of the crust, ejected from a convenient hole (also called a ‘volcano’), flowed downhill for a bit and solidified there. You are looking at displaced mantle material. Most of the ocean floor consists of this stuff. It is heavy because the mantle is made of denser material than the continental crust (if it weren’t, the crust would sink down like an overweight iceberg and continental existence would be short-lived). In practice, the density of basalt is close to 3000 kg per cubic meter. The continental crust is typically around 2700 kg per cubic meter.

Basalt is the ultimate volcanic rock. Why doesn’t every old lava flow look like this? There are a number of reasons why not all lavas are the same.

1. Temperature and viscosity

The first effect is that of temperature and viscosity. I know, that is two, but they are closely related. Lava can be compared to honey. Warm honey flows easily, but put it in the fridge for a few minutes and it becomes much less keen to spread out, even though it is still a liquid. Honey is actually quite a complex substance, even though it is mainly just sugar dissolved in water. The melting temperature is around 45 C (depending on the sugar concentration): above that temperature, it does indeed behave like sugar water. Below that temperature, it should freeze but it doesn’t, at least not until the temperature goes down to about 5 C. In between, it is a super-saturated liquid, where there is more sugar dissolved in the water than fits. The excess sugar forms crystals and this turns the honey into a mush. As it cools, more and more crystals form and the honey becomes stickier and stickier. Finally, it freezes. (Strictly speaking it doesn’t fully freeze until it reaches -50 C, but below 5 C it is so sticky you hardly notice the difference.) Now turn the temperature back up – and nothing happens until you reach the melting temperature. Funny honey. (When we call a loved one ‘honey’ one does wonder which characteristic of honey is intended. This expression is definitely open to interpretation.)

The stickiness is also called ‘viscosity’. Higher viscosity means stickier, i.e. more reluctant to move.

So in what way is lava like honey? Should I call my loved one ‘lava’ or would that get my fingers burned? Well, lava is also a mix of substances, and these have different melting temperatures. As lava cools, some substance may come out of the liquid and crystallize. As more and more crystals form, the lava becomes less runny and more sticky. And this gives rise to the two Hawaiian words used to describe lava flows: Pahoehoe and A’a.

Pahoehoe

A’a.

Pahoehoe is the thinner, runnier lava that happily covers large distances and creates smooth lava flow which afterwards you can walk on. It is the hot honey.

A’a is the sticky lava that refuses to go anywhere fast. It forms very uneven surfaces and is a nightmare to walk on (even after it has cooled enough). Its surface will shred your shoes – this is the one place on earth where high heels may give an advantage. A’a is the honey that has been kept too cool and really would have needed a few seconds in the microwave.

In Puna, the early eruption brought up lava that had been in storage for decades – perhaps centuries. Even though it had stayed warm (a kilometre of rock insulates pretty well), it did not stay hot. This became the sticky stuff, with high viscosity; this explains why the initial eruptions did not produce much in terms of lava flows. It built walls – not roads. Later, the new lava arrived and this was much hotter. The hot, new, all-running and dancing low-viscosity lava ran like runny honey and in no time covered huge swathes of country side.

Even though both are basalt, the two behaved very differently. Poor Puna.

2. Composition

Let me divert for a minute. Lava contains a mix of elements. The main ones are iron, magnesium, silicon, and some other things such as aluminium (called aluminum in Trump land, a spelling that was in use in the UK very briefly but was introduced to the US through the Webster dictionary of 1812.) Each of these forms minerals (mainly oxides), and each mineral has a different melting point. Hot magma contains all these elements and their minerals, although not always in the same ratios. But keep magma for a while in a storage facility (also called a magma chamber) and it begins to cool – very slowly. The first minerals to hit their melting points are iron and magnesium oxides: they form crystals and drop out of the solution. Beforehand, the magma was called mafic (for magnesium (never to be called magnesum) and iron). Now that iron and magnesium are becoming depleted, it is called andesite – you may remember this word from Puna’s infamous fissure number 17.

Store the magma for even longer, and you are left with mainly silicates, mixed with a few other elements (aluminium, calcium, sodium). This is called felsic lava (the word ‘silicic’ is also used). Rhyolite and dacite are of this form. Dacite has made an appearance in the recent Puna stories, albeit only found in deep (geothermal) drilling and not on the surface.

You can expect that this will form a sequence in temperature: mafic lavas are hotter and thus less viscous, andesite is cooler and stickier, and felsic lavas are positively cold (as lavas go) and nearly immovable. And for the most part, you would be right. Mafic flows – felsic stalls.

Rhyolite

Andesite

There are a few exceptions: sometimes magmas form by melting rocks that themselves already lack certain elements. For instance, imagine a rhyolitic magma chamber solidifying into rock. Long after, heat finds its way to the rock and melts it: the new magma will have the composition of rhyolite, but it could well be much hotter than usual, and therefore far less viscous. You can now get a rhyolitic pahoehoe, and this is for instance found along the Snake River in Trump land.

(Hint: if you want to impress your friends, using the term rhyolitic pahoehoe in Puna will do wonders. But avoid saying the andesitic a’a of Haleakala which could leave the impression that you had a drink too many.)

Iron makes the world look black. That is true in lavas as well: mafic basalt is dark to black, while the andesite is greyer and the rhyolite is a bright lava. Of course, add oxygen and over time iron turns red, like the soils of Oklahoma.

I should point out here that the world of lava is simpler than it used to be. A few billion years ago, the mantle was hotter than it is now and therefore lava was considerably hotter as well. This gave a type of lava that is ultra-mafic, an extremely magnesium-rich, which is called komatiite. They don’t make it anymore.

3. Rate of cooling

So temperature is important. But how quickly the temperature goes down is also relevant. Lava rocks that solidify fast look very different from ones that cool only slowly. The rate of cooling has three different effects.

(i) Shape

The first of these makes sense: if the cooling is fast, the flow patterns become fixed in the material. The ultimate example is pillow lava: these are erupted under water, and in consequence cool very rapidly (in the battle between the mid-oceanic ridges and the ocean, the lava has yet to win. Luckily loosing builds character and pillow lavas do have that. Although one could argue that winning builds more character.)

Pillow lavas

Petrified lava ripples

On land, cooling is slower. Thin flows on the surface cool faster than thick ones. In the picture, the difference between the thin flow in the foreground and the thicker ones in the background is notable! The former solidified fast enough that the flow patterns froze in.

Pele’s hair

An extreme case is that of liquid droplets flying through the air. As they cool they solidify, and form long streamers. This creates the strangest rock of all, with the evocative name of Pele’s hair. You have to feel sorry for her hair dresser! What kind of comb would be needed? This lady is not for brushing! Pele’s hair can be found especially around lava fountains. But beware: the hair strands can be needle-sharp and should be handled only with thick gloves.

The strings come from wind acting on the flying droplets. If there is too little wind, you don’t get strings but tear-shaped droplets (very much like the shape of a drop of water falling from a leaky tap), about a centimetre across. These are called, not entirely surprisingly, Pele’s tears (although with the lady’s reputation, the need for tears seems minimal.)

(ii) Glass

So much for the first of the three effects. The second one is very different: this is when lava is cooled so quickly that it briefly forms a supercooled liquid, i.e. a liquid below its melting temperature. You can create this yourself by putting distilled water in the freezer. It will remain a liquid even though its temperature drops far below freezing. But disturb it ever so slightly, and it freezes over instantly. If you do this with molten rock, and let it suddenly solidify well below its melting temperature, it can create a glass. (The temperature below which this can happen is called the glass transition temperature, which is different for each material.) The trick is to make it solidify all at once, with as few separate crystals as possible.

An easier way to do this is by starting out with a lava which contains a bit of water. Water lowers the melting temperature, and so the lava can be cooler whilst still a liquid. Now evaporate the water (as can happen as the lava becomes exposed to air). Suddenly the melting temperature goes up, and the lava finds itself caught out, being a liquid well below its new melting temperature.

Obsidian

A well-known example of a rock that formed in this way is obsidian, a black rock of volcanic glass. It forms from silicate-rich melts, i.e. from rhyolites. Obsidian was sought-after in the stone age as it can be used for cutting (including the careless owner).

It should be harder to make a glass out of basalt, because it is hotter to begin with and readily forms crystals while cooling. But Hawaiian volcanoes manage it quite easily. Basaltic glass is called tachylite. It can be a thin edge on a crystallized lava flow, but on Hawaii it can form thick layers. And now you will not be surprised to know that Pele’s hair also consists of strands of this glass. Ouch again.

Perhaps the most dangerous of all is when lava meets the ocean. The instant cooling forms small particles of glass, and the rising steam carries them away. The white plumes of Puna, where the lava comes over the sea cliffs, are pretty only from a safe distance. There are several reasons why you shouldn’t breath in the stuff – the tiny glass particles among them.

(iii) Crystals

The third effect is that of crystallization. As lava cools, crystals begin to form. The slower the cooling, the larger the crystals can become. These crystals (or their absence) are easily recognized by eye.

Compare the following wo rocks. Both are obsidian, and thus formed through rapid (instantaneous) cooling. The left one looks ‘normal’: a hard glass, albeit with a greenish tint. The one on the right contains a host of crystals, a feldspar to be precise. What happened? It spend some time cooling slowly, allowing the crystals to form, before it suddenly cooled very fast and let the remainder turn to glass. The texture shows that it cooled in two distinct phases, one slow, one fast.

Two types of obsidian, with and without crystals

Pitchstone

The next one is pitchstone: also a rhyolitic glass, like obsidian, but containing a larger fraction of minute crystals. It gives the rock a dull appearance. The crystals are very small, and this shows that the initial cooling was fairly fast. Pitchstone contains a bit more water than normal obsidian, and so the rock has a lower melting temperature. The various minerals with the highest melting temperature had time to form small crystals before the remainder turned to glass.

Pegmatite

And finally the other extreme: this is a rock with enormous crystals which must have cooled very slowly. In fact this particular rock, a pegmatite, would have formed in the deep crust, where the cooling was so slow that the single crystal could take centuries to form, before the surrounding magma finally turned to stone.

Fragmentation

Now we know what volcanic rocks look like. But often, volcanic rocks look very different, striated or welded. They also come in a range of sizes, from the island-sized flows of Mauna Loa to the ash of Mount St Helens. What causes that difference?

Fragmentation of the lava comes mainly from explosions. Rock does not easily explode, of course: it lacks suitable chemistry, and lava is nowhere near hot enough to vaporize rock. The explosions come from trapped volatiles. Big explosions come from volatiles in magma which suddenly decide to become a gas, need a thousand time more volume for this, and end up blowing apart complete mountains. But it can also come from trapped vegetation underneath a lava flow, or even in one infamous incident, trapped snow. These kind of explosions produce flying lava bombs – the name is not entirely accurate, as the bombs are ejected by the explosion – they do not explode themselves.

The explosions produce fragments of a variety of sizes. They are distinguished by size.

Particles smaller than 2 mm are called ash.
Up to 6.5 cm it is lapilli.
Above that size it is a lava bomb.
All together it is called tephra.

Lava bombs of two different sizes

What goes up must come down – as true in volcanics as it is in politics. It is important to know that a lava bomb is made of lava – it will happily start a fire if it lands on flammable material; the danger is not just in being hit by a projectile with the size and speed of a cannon ball (although that is not entirely without danger either). They can be as large as 5 meters (although 20 centimeter is a more typical size, luckily), be ejected at a speed of 200 meters per second, and can travel considerable distances through the air: up to 5 kilometers. Lava bombs may also arrive as tachylite. Ouch!

Lapilli tuff

Smaller fragments travel further than large ones because they benefit from the lift from rising hot air of the eruption. These fragments also are much more voluminous, and the ash can cover large areas in a blanket that is centimeters to meters thick. It welds together, either through heat or over time. The welded layer is called tuff.

The name is not fully appropriate because it is the softest rock created by volcanic eruptions. The tuff can embed lapilli fragments and even lava bombs if not too far from the eruption site. Whereas the lava bombs have the composition of the lava, the tuff will often have a composition close to that of the mountain. If lava, it is often rhyolitic (because that explodes well). Tuff is often light coloured, and can be almost white. The best place to find tuff is in local buildings: it is everyone’s favourite building material. Although, be aware, if your local buildings use it, somewhere in the area is a mountain which made it, and which may have its own building demolition program.

A tuff sandwich. Source: sandatlas.org

The tuff in this image is layered between lapilli (which falls first) and ignimbrite, which is debris from a pyroclastic flow. The tuff can be recognized by its smoother texture.

Gas content

The final piece of the puzzle is the gas content of the erupted lava. If the gas content is high, the lava becomes frothy, and when it solidifies it has lots of holes, like a swiss cheese. There can be so many holes that the rock weighs less than water, and floats: this is called pumice, and it forms especially well after an underwater eruption where the water provides more gas than the lava can cope with. The sea can become covered by rafts of pumice kilometres wide: after Krakatoa, they made local sea travel almost impossible for months.

A floating island of pumice

Scoria. Source: wikpedia (Jonathan Zander)

If the stone has lots of holes but not enough to float it is called scoria or cinder (the two words are interchangeable; ‘cinder’ is older). This is where Cinderella got her name from. (No, I don’t know either. And nowadays she would be called Scorella.) These form especially during volcanic explosions as the gas-rich lava is shot out from the vent.

Amygdale

But gas bubbles can also form underground, and leave magma that solidified under ground with holes. Over time, the holes may become filled with water and the water can deposit new minerals, often a calcite. These rocks are called amygdales.

But it can get even better. The rocks can have very large holes inside, and over time, anything can happen in those holes. Open the rock and you may have the surprise of a life time, with wondrous crystals and colours. Here is an example, an oversized amethyst. What causes the different colours? That, my dear Watson, is elementary. But the science of volcanic gems is a different topic – a different post, perhaps.

An oversized amethyst

Albert, May 2018

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343 thoughts on “Lava rocks! (republication)”

  2. Here are the published pressure measurements of Krakatoa in 1883. Just like today, they show first an increase, followed by a decrease of pressure, and are seen worldwide. The wave was detected 7 times of which 4 are shown. Note that the wave goes around the world both ways, and so passes each place twice coming from opposite directions. So 7 detections means 4 times around the world. The lower pressure part of the wave disappeared after the first round

    • I have some thoughts about the atmospheric shock. The wave that has been recorded all over the planet is likely not caused directly by the ejection of magma but by its interaction with the atmosphere. As the magma exits the nearby atmosphere heats up and expands up into a plume, this pushes the air away generating a wave that causes a pressure increase. The pressure decrease is perhaps due to air flowing back towards the lower part of the plume, or simply a reaction to the first pressure increase.

      The magma must have met water in its way up which then flashed into steam rapidly expanding in volume. The water must have added up to the volume of the cloud. Thus the cloud and the ensuing pressure wave travelling across the atmosphere must be much greater than what would be generated by an eruption of similar volume on dry ground. This makes it hard to judge the volume of the eruption based only in the monster sized plume and the pressure waves it has generated.

      • The pressure wave is explosive, so comes from the shockwave. The positive wave followed by the rarefaction is normal, it is after all a wave. The explosion is caused by the flash evaporation of volatiles, either in the magma or from water. Krakatoa also involved water, probably not from the magma chamber collapse, as often suggested, as the explosion was off-centre and the magma conduit survived the explosion. Perhaps it was triggered by a flank collapse.

      • Obviously it met water
        The caldera is underwater like a lot worldwide on land that are filled with lakes
        This was a particularly fast explosion by the sonic boom which sounds like a rifle shot not the usual low frequency boom with other eruptions
        This literally exploded like TNT
        The volume of material isn’t relevant the energy released in a short space of time made it so violent and powerful

    • Okay… shockwaves. Albert’s data (thanks Albert!) shows that Krakatoa’s shockwaves were powerful enough to circle the Earth more than once. I have yet to see evidence of this for Hunga-Tonga, so IMHO this would mean that Hunga-Tonga was nowhere near as powerful as Krakatoa 1883 (which is estimated to have been a VEI 6, though as others have said, VEI isn’t well suited to measuring explosive intensity).

      As for the shockwave itself, it’s the gunshot-like rapport which IMHO might mean something. I’ve experienced similar pressure pulses (I think) what’s seen on the video; as a child, I grew up right under one of the Space Shuttle’s approach vectors to Edwards Air Force Base, though over a hundred miles from the base, so the Shuttle was still high supersonic when it passed overhead. The double sonic boom was quite intense, you could feel it as much as hear it (and it was exceedingly loud, louder than a close lightning strike). It was very much the sharp ‘crack’ that appears in the video (the one where the people run like heck), This makes me wonder if the driving factor might be related; supersonic shock. If the explosive front was initially supersonic, you’d get a very compressed and intense shockwave (basically a sonic boom) created over a very large surface area. Is it possible that this might have been the case here?

      Also, as for the cause of the explosion itself; is it possible that a landslide or landslip (such as Anak Krakatoa did to create some tsunamis a few years back) might have exposed part of the magma chamber to the sea? I’m remembering the landslide at Mt. St. Hellens, which created the massive blast via exposing a large volume of magma. I’m trying to find seismic data, because this guess of mine is easily falsifiable; a land slip should show up on seismic data right before the big bang if it was causal, and so far I’ve seen no signs of this (so, probably a bad guess on my part).

  6. The shockwave passed Switzerland too.
    Was said to have been 2 hPa of difference.

    • I was going to post this article and saw your post. The author says that the size of the eruption shows fresh gas rich magma intrusion, not simply magma water reaction into steam. It would be interesting to get comment on this. I am having trouble locating information on cloud height, but clearly it went up well beyond the 17 km or 20 km figure quoted on the internet.

    • This is indeed a once or twice in a century event then, and I guess a VEI 6 eruption too. It is frightening that no one saw the caldera collapse coming. There were no reports of unusual activity at Hunga Tonga that could indicate it was preparing for a caldera forming event. That a volcano can go from behaving normal to collapsing into a caldera is terrifying. Imagine if Rabaul, Campi Flegrei or Aira pulled this off, there would be no way to prepare for a VEI 6 scale eruption if there aren’t any particular signs to identify, it could be catastrophic.

      On the other hand it is amazing that a mere 70 kilometres saved Tongatapu from being destroyed even though this was a massive eruption. The pyroclastic density currents and megatsunamis must have dissipated within 70 km of the volcano.

      • “It is frightening that no one saw the caldera collapse coming.”

        Cough…

        • Did you mention a potential caldera-forming event at Hunga Tonga before this eruption happened?

          There even were volcanologists yesterday, watching the eruption unfold, and they didn’t report any suspicions that the volcano was about to go caldera hours later.

          • I did mention the ring fault. I thought people would catch the importance of that in regards of caldera formation risk.

          • That’s what these beasts are like
            Very little obvious precursors

        • Yes, you rightly hinted at it. Then somebody commented on your comment speaking about the volcano on the left without seeing the ring fault, and that was it. You saw the possibility, no doubt about it. Having an eye for also Taal and the Philippines.

    • Those submarine volcanoes are part of a powerful chain that ends with the taupe volcanic zone
      Taupe is thought to have erupted over months before going supernova
      This thing is nasty

    • Yes, but that was from before last night’s eruption, and is from the explosions on the previous day. We don’t know how much is left now. If anything.

      • Seems like you missed the sentinel passes I just posted.

        The 3 images show the following:
        1. Before the first medium eruption.
        2. After the medium eruption.
        3. Yesterdays big eruption.

        It is an interesting timeline of how the caldera was gouged out.

        • The final image was published this morning. The caption actually says that it was taken hours before the cataclysmic eruption. No images of the aftermath will be available until later. The sky has to clear. Also, the explosion was in the evening and darkness fell shortly after. No imagres at night.

          • Thanks, I had not seen this (impressive) one. The one that I responded to showed changes as of yesterday. This one shows there is very little left of the island(s). A quick estimates gives a crater 4 km across. Depending on how deep, this could have reached VEI 6

        • Ringfault, Noread, Invisible, Carl. το βλέπω. I think this has been a crazy one for most VC-readers and contributors. We take different approaches, have somewhat differing views and I like (most of) the balance it has given throughout the day.

          This HAS to be the biggest event in VC-history. And could (could) even be the biggest volcanic eruption in a long time. We just don’t know yet.

          But I still can’t help leaning towards your asessments on this one. Still cu. km of data to collect and process though.

          You all have made it an exiting day. 😉

          • Oh it’s the biggest volcanic eruption in a long time. That much is clear by now. We’re talking high end VEI 5 or low end VEI 6 for this one. That’s the biggest in 31 years and these kinds of explosions only occur a handful of times a century.

  12. “The eruption of Mount Pinatubo in 1991 produced various oscillations both in the atmosphere and on the ground. “Seismic disturbances lasting approximately 3 h were detected around the world. (…) A large volcanic eruption can be a source of atmospheric pressure waves that propagate around the globe, as reported, for example, from the eruptions of Krakatau in 1883 (Simkin and Fiske, 1983), Bezymianny in 1956 (Passechnik, 1958), Mount St. Helens in 1980 (Donn and Balachandran, 1981; Sawada and others, 1982), and El Chichón in 1982 (Mauk, 1983)”.

    https://agupubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1029/2010JB007747

    So I guess it is not so unusual for volcanic eruptions to produce atmospheric waves on a planet-wide scale. e can say however this is the largest “explosion” in Earth since Pinatubo in 1991. As I commented above the pressure waves are generated by the expanding cloud and there are many factors that could influence that like the presence of water being flashed into steam. So it is not necessarily an exact way of approximating the volume nor the eruption rates.

    • The knowledgable can extrapolate the data and thereby appreciate the enormity of the event. However, the visuals of Pinatubo’s final paroxysm or St. Helen’s flank collapse carried far more weight for the lay person.

  13. After this explosion last night, which I had the good fortune of catching on the Himawari-8 live just after it happened, today I realize how that a submarine volcano sometime in 1808 could have done the same thing, but we’d never know about it, since most of the debris is under the water after things settle down.

  15. Is the Tonga volcano erupting again?

    ?w=800&h=623

    ?w=800&h=295

    • There seems to be a small plume in the loop at roughly the one o’clock position to the main plume, so not 100% sure. But must degree with VolcanoNut, certainly possible!

  16. Island nation of #Tonga is completely offline following a #tsunami triggered by a massive volcanic eruption in the Pacific Ocean.

    According to @kentikinc data, traffic volumes began to drop around 4:30 UTC (5:30pm local) before finally going to zero at 5:40 UTC (6:40pm local).

    https://twitter.com/DougMadory/status/1482377945318625294

    • This sounds bad, although I don’t know how exaggerated this info is:

      “Breaking News: Just in The People Are Struggling To Breathe in Tonga as a Result of The Volcano. Also, There Have Also Been Reports That a Rescue Operation is Underway in Atata, a Small island Off Nukuʻalofa, Which Was Completely Submerged By The Tsunami Waves!”

      https://twitter.com/HaydenRocks2022/status/1482427812019843074

  17. Just occurred to me that I have a high resolution barometric sensor module for my Raspberry Pi breakout board. With possible detectable passes to come would be nice if I could actually find it! Just thought I’d mention it because it’s quite a common sensor to have if anyone’s played about with Pi hardware and maybe others reading this have one somewhere.

    • Pimoroni breakout garden with Pimoroni BME280 breakout board – I know that because I can find it in my purchase history but sadly not yet in real life. Unusually for me I seem to have actually stored it somewhere sensible – which means I can’t find it, instead of my normal default storage of it will be in this pile somewhere 🙂

    • My somewhat downmarket Davis Weather Station, recorded the pressure blip on the Barometric Graph, which was flatlining at the time. I checked this against the graph issued by the Bureau of Meteorology for yesterday and both anomalies coincide

      • Hi all, I’m a long-time lurker here and an atmospheric scientist. This is my first post. I just wanted to chime in to state with certainty that my Davis Vantage Pro 2 station here in central Indiana clearly recorded the pressure oscillation from this eruption, as did those of many of my colleagues. I now have an app on my iPhone recording the pressure at 100 ms intervals in an attempt to catch the next passage of the wave assuming it hasn’t completely dissipated by then.

        Thank you! Do let us know if you see it a second time. As a first time commenter, your comment was held back for approval. Future comments should appear without delay.

  20. This is quickly becoming one of the most overhyped eruptions I’ve ever seen!

    • Well, I am sorry that data seems to disagree with you.

      I seriously would not like to see an eruption that you deem underhyped.

    • It is in an isolated part of the world.in the ocean
      That makes.it under reported
      Not overhyped
      It’s scale can only be judged by its effects
      Which are global
      Doesn’t sound over hyped.

    • I was sceptical at first, but have you seen the 30 km high plume, the pressure wave going round the whole planet, and the 4 kilometre wide caldera that has formed?

          • So I’m a troll for expressing my opinion and/or questioning “the narrative”? Our society really is screwed if this is the state of public discourse! Oh, and the unauthorised change of my name on the original comment is rather childish!

          • You’re not “questioning”. You’re ignoring. There’s a big difference.

            This is a high end VEI 5 or low end VEI 6. That scale of eruption only happens a handful of times a century. So yes it very much IS worth talking about and talking about a great deal. If nothing else it’s the first confirmed ocean-wide significant tsunami generated by a volcanic eruption that I can recall. That alone makes it exceedingly notable.

            So yes I’d say your behaviour does qualify as trolling.

          • So not automatically accepting the data without question = trolling? By the way, overhyped in terms of size, not impact or intensity.

          • Was there a large amount of juvenile material? No. Clearly it was an extremely large phreatomagmatic event. However VEI is NOT the amount of juvenile material involved. VEI is the amount of material ejected by the eruption explosively.

            The size of the explosion alone dictates a certain eruption size. The height of the column alone dictates a certain eruption size. The diameter of the umbrella cloud alone dictates a certain eruption size. The ocean basin wide tsunami alone dictates a certain eruption size. All of them point to high end VEI 5 or low end VEI 6.

            So you’re not questioning the data. You’re ignoring it.

  21. There is though a bit of a problem.

    Internet is gone from Tonga, and so far nobody has made contact as far as I know.
    I hope it is just a broken cable.

      • That does not sound good at all. I pray that the people of Tonga are safe and can be safely evacuated as soon as possible. That ash cloud alone must have caused incredible problems for them, add in to that scenario a tsunami causing severe flooding problems, plus night time and poor visibility, as well as possible breathing problems from the ash cloud then this is a very poor situation to be in. I pray that poor scenario does not turn into dreadful scenario. I sincerely hope that the worst of their problems is only a loss of internet connection. Seeing the shockwave causing a pressure wave around the whole world shows what a severe eruption this was. My thoughts tonight in UK are with these poor people not only in Tonga but also in many of the islands of Fiji that will have been badly affected. Hopefully tomorrow will bring better news but it is very worrying tonight.

      • There is very little information about Tonga. I initially thought this meant the damage had not been too serious. I fear however that the information is not getting through.

        • A few minutes ago from the link I posted above:

          “Relief as Southern Cross Cable confirms contact with Tongan comms centre
          Southern Cross Cable Network says it has been able to confirm contact with a communications centre in Tonga, which is working to restore internet and phone links to the island nation.

          Sales director Craige Sloots provided the “good news” shortly after noon, after earlier reporting that the cable company had been unable to make contact with the network operations centre even by satellite phone.

          Sloots said Southern Cross had received a brief update from Fintel, a partner in Fiji, which had managed to get in contact with Tonga, via mobile phone company Digicel.

          Work was underway to “reset submarine line terminal equipment to try and get communications restored”, Sloots said.”

          Good-er news. 🙂

          • There must have been submarine pyroclastic density currents and perhaps they destroyed some of the submarine cables.

          • Sounds to me like it could have been a power issue on the Tongan side.

      • I presume the energy of a circular tidal wave scales as proportional to the distance if energy is largely conserved. Its 60 km to Tonga, really really close, 2000 to NZ and 3000 to aus. So a tsunami of just 1m there would be in the 100’s of meters at Tonga (directed energy excluded). The initial reports suggested Tonga got a few meters, but this may well not have been due to the major blast.

        Its hard not to think that there will be significant devastation

        • Yes, I expect significant damage. One early report mentioned that one of the poorer settlements had been submerged. The power went down some time after the explosion, so I think that was due to ash on the generators. The tsunami height decreases linearly with distance only near to the source. Further away it decreases less fast.

          • From what we’ve seen thus far, the tsunami videos do not carry the visual weight of the Japanese or Sumatran earthquakes, though, having been to Fiji and New Caledonia, its easy to understand the impact of to these islands from a lower wave form.

    • Can anyone get through via ham radio or satellite phone?

    • Just another part of science infected with Trump Derangement Syndrome!

      • Accurate observation however. Idaho very much is Trump land.

        Just imagine Jo Biden being in charge of the disaster relief operations for this. He would display his usual level of competence as with Afghanistan, supply chains, inflation and COVID. So for those who want to make sarcastic and derogatory remarks about Trump consider very, very carefully actual reality and competence.

        Trump can legitimately be criticised for being arrogant, rude and bombastic. Biden can be legitimately criticised for succeeding in running the country into the ground inside a year. Just imagine what he’ll have managed to do it by 2025.

  23. In the grand scheme of things this eruption was close to the ideal place for a VEI 5-6. Uninhabited Island in remote Pacific so relatively small area within range of worse tsunamis. In terms of any climate effects southern Hemisphere has 1/8th the population of northern, so less people effected potentially by weird climate stuff.

    We should probably psychologially prepare though for a considerable death toll. We have been focusing on Tongatapu, and admittedly it could be pretty bad given most of population is on a peninsula and internet is out.

    What scares me though are the small inhabited islands to the north. It seems the worst of the eruption was aimed north given Japan got a 1.2 meter tsunami and Hawaii similar, while Tongatapu only got a 1.6 meter one. Australia and New Zealand also were in the same league as places in the North Pacific 3 times as far away.. There are lots of small islands with a couple hundred people or less. The islands of Tungua and O’ua are just 55 miles northwest of the volcano, are low, and populated. Given islands 40 miles west of the Island were completely destroyed by the tsunami, things could be pretty bad for the couple hundred people who lives on those islands. A little further to the northwest there are even more inhabited islands.

    • On second look, the line between the new hole and those islands passes through Hunga Tonga which was only mostly destroyed, so if they are lucky that helped break the force of the shock wave and water push in their direction.

  24. Made this yesterday. Yellow octagon is a rough estimate of a crater 2 km wide. At the time I thought this was maybe pushing it but like everyone else I was greatly underestimating things… if the picture are to be taken then just the first explosion was as big as the one in my picture, already a sizable VEI 5 of 2 km3, and the second explosion took out the whole cone as well as some of the older islands. Not sure about the volume of new magma, but this is probably a VEI 6 for creating the crater size that it did. Probably not as big as Krakatau though or Tongatapu would have been hit by base surges and we would know about that by now.

    Usually you only get these such big explosions from silicic volcanoes, Hunga Tonga is made of andesite and basalt, if it was on land it would still be young and growing. Goes to show what effect water can have, it is the volcanology equivalent of giving a child a bazooka…

    https://imgur.com/a/ZdVbyM9

    https://i.imgur.com/mqu6FHU.jpeg

    • The 2009 eruption had a SiO2 content of 57.5-58 % SiO2. So yes, a basaltic-andesite. All samples taken from Hunga Tonga-Hunga Haapai fall in the basaltic andesite field, ranging from 54 to 58 SiO2.

      • So probably if the eruption became effusive it would be strombolian, a nice ‘safe’volcano. Maybe this is just a good warning that no volcano that is at sea level of any composition should be considered not potentially dangerous.

        I wonder if maybe a flank vent opened up deep underwater, the eruptions did stop before, and Carl said he saw ring faults. The explosions were pretty sudden and eruptions before not particularly big, not the sort of thing to lead to caldera formation, but an eruption out of sight in the deep sea could have started it off. No plinian stage until after the big blast too.

        Or maybe there was no caldera and this was like a maar explosion in the ocean. I wonder if this would count as a big basalt blast.

        • Well everything happened so fast and with no proper seismic monitoring that I have no idea what happened. All I know is that after some small eruptions which were in no way anomalous, or so it seems, Hunga-Tonga Hunga-Haapai decided to go caldera. Why? I don’t know if we’ll ever know.

        • Taal 1965 was going to be a nice, boring lava flow if the eruptive fissure hadn’t crossed the littoral.

          Looking at acidic eruptions, Saint Helens would still be in its 1980 eruption, burping up lava domes now and then, if the intrusion had happened under flat or less steep slopes than it did.

      • You don’t really know if the magma that went off in this eruption had a different composition
        These systems are probably more complex than you think
        The taupo volcanic zone which sits at the southern end of this chain of activity, has all the different magma types
        I don’t think water interaction explains fully the violence of it,there had to be a lot of trapped gas

  25. Don’t know about the rest of you, but for quick reference to the La Palma eruption or to Fagradalsfjall eruption videos and tremor charts, like many people I use the handy aggregator link https://eruption.acme.to

    The “.to” domain happens to be Tonga.

    Now this huge eruption occurs at Hunga Tonga. Coincidence, or not?

      • Coincidence, Chad? I’m not so sure about that, because what happened does fit into my very own theory: “Volcanic egotisim as a driving factor for eruption timing in basaltic magmatic systems.”

        Hey, if those Bogdanov twins that Carl told us about can get PHDs for their theories, why can’t I get one for my theory that volcanoes have a big jealous streak and, when they browse the Internet and see other volcanoes hogging the attention, basically say “hold my beer…” and go kaboom. That’s gotta be good enough to get me a PHD, right?

        • Volcanic egotism is definitely a thing. Grimsvotn’s been building up to an eruption for a few years now and then Askja comes along and will probably pop off first.

      • “Of all the gin joints, in all the towns, in all the world, she walks into mine.”

    • Coincidence. 😉
      I’m the owner of this domain acme.to since Aug 04 1999 and eruption was never in my mind as an web project. Not until Fagradalsfjall 🌋

      I have added a section for Tonga, but there are no live cameras… https://eruption.acme.to/tonga.php

      • Never imagined anyone would take that seriously, but it is a funny coincidence.

        Great website. Very useful. Thanks for always keeping it current.

  28. Peru, moronically, didn’t issue a tsunami advisory and as such 2 women died. The Tsunami wasn’t large by any stretch and these 2 deaths could’ve been easily avoided. The government has ordered the press to not use the word tsunami and instead use the phrase “Anomalous Waves” instead of taking responsibility for their mistake.
    https://www-biobiochile-cl.translate.goog/noticias/internacional/america-latina/2022/01/15/reportan-dos-muertes-y-danos-por-tsunami-en-peru-pais-no-emitio-alerta.shtml?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp

    • 65-66 million years ago: Most dinosaurs must have drowned right away. All over the world, more locally though.

    • Thank you for the link. Reminding strongly of Kuwae:
      “The Tongoa and Epi islands once formed part of a larger island called Kuwae. Local folklore tells of a cataclysmic eruption that split this island into two smaller islands with an oval 12 x 6 km caldera in between”, en wiki, Kuwae

  31. Crater from the first eruption was 1.7 km across. Not sure how deep or if it was longer in one direction, but that dimension would put it pretty well in VEI 5 territory, at the very least it is comfortably bigger than either of the near 5s in 2011, and the biggest explosive eruption in the 21st century.

    Second big bang on the 15th completely blew up the whole of the 2015 cone, as well as about 2/3 of the northern island. Its crater is at least 4 km in diameter and possibly is the same size as the whole caldera. So very likely this will measure in at a VEI 6. I would guess it was not as big as Novarupta in volume, but way more intense, 5 hours vs 3-4 days. It is probably the biggest eruption in the last 100 years.

    It is quite incredible really, this is not a volcano that a lot of us would immediately jump at as a likely candidate to do this. It is both mostly mafic and also has erupted pretty often in the last few decades. Water really does change things, volcanoes with the same description are everywhere in the Pacific…

    • Good point about the intensity vs. magnitude comparisons. At this point I am thinking that 50-80% of the energy of the Jan 15 eruption was released in as little as 30 minutes. The mushroom cloud appears to have grown to ~250 km diameter in 30 minutes, and perhaps 400 km in the first hour. I am going to compare this to Pinatubo. Thinking the 1 hour growth rate may exceed Pinatubo.

      • Yes, intensity is just as important a factor as volume, I would argue it is what most people actually think the VEI scale measures. Novarupta was a huge volume, but low intensity lasting several days. This probably is lower volume but erupted it all in a few hours.

        After looking over the data though I think we really did just see the next Krakatau, a once in a lifetime bang, probably the biggest bang anyone alive today will ever see. I do in fact actually recall hearing some thunder at about the right time, local weather was expecting thunderstorms so I thought little of it, but the storm never actually happened in the end nor was there any other thunder. So now I think I did hear the eruption after all.
        I live 4200 km from Tonga…

      • “The mushroom cloud appears to have grown to ~250 km diameter in 30 minutes”.

        330 km diameter in just over 30 minutes, I have measured it on Google Earth.

        • It was already 40 km across at the start of those 30 minutes. So grew from 40 to 330 km diameter in 30 minutes.

          • I counted the beginning of the eruption as occurring about 10 minutes before the frame with the 40 km diameter plume. It is difficult to know when to start with 10 minute data but it looked like a small burst had just barely started on the image taken right on the hour. If 330 km in 40 minutes instead of 30 forms a point on the growth curve that is very helpful. Thanks for that measurement. This appears to be greater than the growth of the Pinatubo cloud be a large margin. I am starting to think that the energy released in that first half hour to hour might have been greater than for any volcano since Krakatoa in 1883.

    • Possibly indicates a multiple personality in terms of magma types

    • Quite a stunning reminder of how sudden, dangerous and difficult to predict magma-water interactions are.

  32. Kilauea has paused again, and the deep quakes at 11 km depth ave started up again. I think maybe these could in part be due to pressure increase in the system as the effusion stops?

    it is very interesting though, this didnt happen in the lake before 2018. I am wondering if it is a sign of something bigger long term? Would be nice if we got a big eruption in the caldera in 3 months, when I am there 🙂

    • WELLINGTON, Jan 16 (Reuters) – Tsunami-hit Tonga remained largely uncontactable on Sunday with telephone and internet links severed, leaving relatives in faraway New Zealand praying for their families on the Pacific islands as casualty reports had yet to come through…..
      Internet and phone lines went down at about 6.40 p.m. local time on Saturday, leaving the 105,000 residents on the islands virtually uncontactable.
      https://www.reuters.com/world/asia-pacific/new-zealand-pm-ardern-says-tonga-eruption-hugely-concerning-2022-01-15/

      • Aren’t any amateur radio operators on Tonga who can broadcast sit-reps to others via shortwave?

        • Not according to marinetraffic.com, obviously there’s a considerable chance that various ships and boats in that region don’t have tracking devices on and such, but when zooming out, it indeed looks like the seas around Tonga are almost empty of ships for several hundreds of km

          • Marine AIS is not a satellite based system, it’s a peer-to-peer network running on UHF radios. So if Tonga is severed from the internet, the AIS receivers feeding the tracker-sites are naturally off-line as aswell.

          • Most shipping lanes head up the coast of australia and past papua new guinea. Not sure if there’s necessary less hazards hiding under the water there but that’s the general route.

  34. This image has probably been posted earlier, but its a sat. image taken 2 hours before the eruption. It shows how the waves interacts with a larger submerged crater that has developed during the last week before Jan. 15th.

    Source of photo: https://twitter.com/tanyaofmars

  35. Invisible

    I saw your ring-faulting hint, and that is the advantage of readers knowing that they don’t know enough. They have an eye for important things sometimes, the eye of an unaccomplished person, a learner. Mind.
    I thought first that Lakigigar mad it to big, but she didn’t.
    I think there should be more order with times (hours, dates) though instead of VEI estimates. It took me a good part of the day to figure out that there was one eruption in the morning and one, the worse one, in the afternoon.
    Everything in every outlet is about the what and the greatness of an event. Police would go crazy without precise timing in their field. So time has to be first. Anyway, you were right, and Laki nearly, as she posted a pic of the two islands after the first eruption.
    Higher tsunamis in the parts of the world that scream notoriously for money should be seen with cautiousness, also a single truck accident in Peru, as there seems to be little damage in the islands of Polynesia, and if I remember my geography right, they are closer to Hunga-Tonga. But we’ll see.
    I recommend as usual to listen to the locals as I consider them more honest than PM’s.

    And to Chad to consider a trip to Tonga instead of Hawai’i.Local info is priceless.

    And to Invisible who can be fallible though as everybody, but is right surprizingly often, Héctor (La Palma) following in his steps, to take into account that like children who are more alert than adults, learners sometimes see s.th. That the accomplished ones wouldn’t see. That’s why the world shouldn’t strive for perfection and listen to locals sometimes.

  36. No offical volume estimates yet for this eruption
    It certainly looks much larger than it really is
    Big pyrocumulus steam cloud

    Not much ash as it may seem. The volcanic cloud is white so very steam rich. This was a steam driven bomb eruption

    Probaly more humid condensation than a real dry ashcloud, most of the cloud is a big pyrocumulus with lots of Ice in it. This is a pheratoplinian eruption, wet and steamy, similar to an oversized Grimsvötn eruption in Icelands Vatnajökull Glacier. There maybe even snowfall and hail inside it high up in the atmosphere

    Of course There is ash too inside

    Yes and probaly mostly driven by water, water gets 800 times bigger as steam, and thats a tremedous force. Indeed expanding steam, magmatic water in the magma is a main driver force of an eruption. This was a very water rich eruption, perhaps seawater haves contact with the magma chamber by pathways

    Water is a tremedous driver of an eruption and here water have gained acess to the magma chamber, resulting in a Big Steam Bomb
    The magma rose quickly and allowed endless ammounts of seawater to cascade into the eruption vents, water and magma chambers does not mix well

    It coud also be combination with magma itself thats very water rich and the expanding steam drives the eruption.

    Volcanoes despite the heat, contains alot of magmatic water in the molten rock, when it decompress to steam in shallow levels in Earth crust.. You haves a tremedous force

    • Look at the difference in the thumbnails on The Watchers:

      https://watchers.news/

      The smaller explosion looks phreatoplinian and laden with steam, but the second, larger explosion definitely appears to have a higher ash content.

      I mean we have to wait and ascertain more factual information here, but I’m convinced this was almost as big in terms of volume as it looked.

  37. The pressure chart indicates that the pressure wave passed Manchester for a second time at 2am this morning (UT), 7 hours after the first passage .

    • Wow it races around the world then
      Woud it make a diffrence If Earth was larger ( Super Terestrial type planet ) woud be less of a shockwave on other side of the world then?

      • Given the timing, I’m pretty sure this is the wave coming from the other direction along the great circle.

    • Is this the other great circle route? One going direct and one via the other direction?

    • The Pinatubo umbrella cloud seems to have grown to bigger dimensions than the Honga api cloud but the latter grew faster, particularly in the first hour or so.

  39. Andesite and 30 km height… *pheeeew* =D
    Yep, water appears to amplify the effects a little bit, just a liiittle bit^^
    Shows how steam and supercritical water is truly very dangerous, as Jesper says too.

  41. “16 January 2022
    The Government of Tonga has agreed to the Morrison Government’s offer of a surveillance flight, to assess the damage caused by the eruption of the Hunga Tonga-Hunga Ha’apai volcano yesterday and the subsequent tsunami.

    An ADF P-8 is scheduled to depart Australia for Tonga tomorrow morning, pending ash and weather conditions, to assess damage to critical infrastructure such as roads, ports and powerlines, which will determine the next phase of the response effort.”
    https://www.foreignminister.gov.au/minister/marise-payne/media-release/australia-provide-assistance-tonga-following-volcanic-eruption-and-tsunami

  42. @Albert: Thank you for the article “https://www.volcanocafe.org/krakatoa-skies-when-the-sun-turned-blue/”. Extremely interesting, the different colors of the sun and the sky.
    Have you also heard of the first sightings of NLC with respect to Krakatoa’s aftermath?
    See https://en.wikipedia.org/wiki/Noctilucent_cloud.

    Actually, I wonder what that means? As NLCs are said to originate from a layer about 80 km above ground, Krakatoa must have managed to get some tiny stuff up to that height…?? So maximum height in 1883 was 80 km then instead of some 30 to 40 km? Or is it, once material makes it beyond some limiting level, say 40 km, it slowly continues propagating even higher due to some extra-tropospheric effect/currents?

    • Yes, I am aware of the noctilucent clouds. They are fairly easy to see in the right season and at high latitude, but not easy to recognize s something different. I don’t see how they can have anything to do with Krakatoa. The eruption was large but not exceptional. So I expect it was a coincidence that they were first recognized a few years after Kakatoa.

    • That just means the amount of new magma was not huge, but it would probably still count as a VEI 6 anyway because of the ejects volume. Being that most of that would be existing rock though it wont be lifted easily into the atmosphere. Most of it was not that hot and probably fell into the ocean close to the volcano, which might be why there were no big base surges. So it was basically a maar explosion in the ocean.

      • So this was probably about the equivalent of a VEI 4 eruption in new magma, but got turned into a 6 from the steam explosion.

      • The main eruption cloud was 700 kilometers wide! As big as a dwarf planet in diameter
        Pretty Impressive stuff, bigger than the whole Iceland and as powerful as many VEI 7 blasts

        Yes perhaps like a giant sea maar detonation, the magma chamber is not that big

    • I guess that because this was a basaltic-andesite volcano the eruption may not have been very big despite being a caldera forming event. For example Masaya has a VEI-7 sized caldera, this means a caldera with a size that if belonging to silicic volcano it would have been formed in a VEI 7. And yet Masaya’s caldera collapses are VEI 5-6 eruptions. Masaya erupts basalts and basaltic-andesites.

      This is a list of eruptions their SO2 emission in Tg and their VEI (volume):

      El Chichón 1982 7.5 Tg VEI 5
      Galuggung 1982 2.03 Tg VEI 4
      Nevado del Ruiz 1985 0.66 Tg VEI 3
      Redoubt 1989 0.18 Tg VEI 3
      Pinatubo 1991 18 ± 4 Tg VEI 6 (borderline 5-6)
      Hudson 1991 4 Tg VEI 5
      Spurr 1992 0.8 Tg VEI 4
      Anatahan 2003 0.11 Tg VEI 3
      Soufriere Hills 2003 0.15 Tg VEI 3
      Manam 2005 0.21 Tg VEI4?

      More eruptions here:

      https://www.sciencedirect.com/science/article/pii/S0377027316000032

      The amount of SO2 actually suggests this eruption was a VEI 4, at least when considering fresh magma erupted. If there was a large amount of old rock blown into ash by the explosion, the ejecta may perhaps reach into a VEI 5. This shows that the eruption was a very violent steam explosion that with a small amount of magma was capable of making an eruption cloud as big as Pinatubo and a pressure wave as big as that of Krakatoa, even though the volume of magma involved is the same as that of Kelut in 2014 or Merapi in 2010.

      This is still speculative though. Perhaps there will arrive new information that makes me change my mind yet again.

      • I should say that Masaya has also taught me that when a basaltic/basatic-andesite volcano goes caldera it usually does many explosive events of both phreatomagmatic and magmatic styles separated periods of quiet. So the eruption may not be over…

      • The damage done to the island suggests a crater was made that is big enough to be a VEI 6, I overlayed it on google earth. Just the first crater before the main blast was probably enough to get to VEI 5, let alone the second. Could still be a 5 in the end, but probably on the high end at least.

        • The crater may have been caused by the caldera collapse, not the explosion. Most likely the caldera collapse was already underway hours before the eruption started as shown by sentinel images. The whole caldera floor must have dropped like a piston destroying part of Hunga Tonga and Hunga Haapai. In the meantime something caused this huge steam blast. Maybe a ring dyke had started to grow and met with seawater, or maybe it was the seawater that made its way down to the magma chamber. The eruption seems a reaction to the collapse. The big question is, what caused the caldera to start collapsing? And also is the collapse done or is it going to trigger more explosions?

      • This is what I was trying to say basically. Yes, it was of remarkable intensity, but I cannot see how it could possibly have been a multi-cubic-kilometre event. Plus, the plume was largely steam, given that it was basically a very powerful Surtseyan explosion. I’m not convinced there has been a caldera collapse, or that we should be judging the size of the eruption almost entirely by the size of the crater (especially given we can’t see below the waves!). I think it could have been a simple flank collapse. I do accept that the event may have be similar in style to what happened at Krakatoa.

        Maybe I should have gone about sharing my opinion in a different way but I stand by my comments. There needs to be more tolerance of different opinions.

        • I wouldn’t say overhyped, just mischaracterized. This eruption produced the largest volcanic explosion ever witnessed in modern history. The explosion was heard in Alaska and was the first eruption known to produce an ocean-wide tsunamis. Very impressive eruption with very little magma.

          • The little magma part is concerning
            Could that mean there is a large explosive ash laden eruption still in the works ?
            That sort of violence indicates a massive magma source to drive it

      • Hector are there figures for last year’s Soufriere St. Vincent and Taal?

  46. Has anyone seen this video?
    https://twitter.com/sakakimoana/status/1482218193619865600?s=21

    Can see the repeated tsumani waves that look to be getting bigger each time. It’s stops after 1m42, but you can still see waves out in the distance, that look quite large to me. Also can see lightning from the eruption on the left.

    The size of these waves may not be huge, but for all the low lying islands they are going to be devastating. And while people may have managed to get upstairs, if they get strong enough or big enough to demolish the fairly flimsy houses they have (can’t imagine most have huge foundations) it’s going to be an even bigger disaster. And across an absolutely massive area, so assessing and grasping the scale of impact is going to take ages. Imagine all the small islands that got limited warning. Horrible.

    • That video has been all over the net. The lightning is really something else. In one small part to the sky at perhaps 45 degrees to the left of the front of the house (which faces about 30 degrees true), I saw as many as 3 independent lighting strokes (probably cloud to ground or “CG”) in a period of only 1 second. That burst of 3 stokes in one second occurs twice in the video! Amazing considering the poor lighting conditions for viewing lightning. In that video, the anvil cloud already takes up most of the sky…..the edge of the anvil can be seen to the E or ENE, and above the low level sunlight from the W.

      • I’d missed that lightning. So I went back and watched it again. Thanks for pointing it out!

    • The aurora borealis isn’t affected by weather here on earth, beside it being visible if there are no clouds and such. And while the weather forecast for Denmark looks decent enough, the aurora forecast isn’t looking that good for the next few days. They are two different things.

      • Thank you, for clearing that up for me.

        Auroras and volcanos, two seperat events.

        There’s something about volcanos and color in the sky, right?

    • Its too small To affects the weather and there was little SO2 it was mostly a steam driven pheratomagmatic detonation

      • Looks like huge ammounts of water crashed into the magma chamber conduit during the eruption

        • It’d be interesting to know the process of how that came about.

          Presumably the first explosion removed a lot of surface desposits, and weakened the structure sufficiently that the pressure of the water above eventually collapsed it into the magma chamber – therefore creating a massively explosive reaction from the seawater flowing in directly.

          • Isn’t it more likely that there was a large body of hot wet supercritical rock/sludge in a chamber deep down. Enough was pushed to the surface to explode and remove enough of the overburden which meant the entire main body flashed into steam. Megatons of steam.
            Basically its a pressure cooker when the top blows off. A very big and very supercritical pressure cooker.
            Seawater falling onto magma doesn’t do much because steam and solidified rock rapidly insulates, as we know from submarine eruptions.

          • if faults opened during the eruption allows seawater into magma chamber you gets a steam bomb.. I think this eruption destroyed much of the eruptible upper andesite chamber

          • Jesper, considering the whole area has big eruptions every 1000 years or so I imagine most of the edifice is fractured and probably as we speak water is infiltrating the shattered remains preparing things for the 3020 eruption. That is its easier to get water in first, and then heat, than vice-versa,

  48. https://twitter.com/metoffice/status/1482605906659622914

    Met Office @metoffice
    Our atmosphere acts as a fluid, like dropping a pebble in a still pond and seeing the ripples.

    A UK pressure trace for the past 24 hours shows how our atmosphere continues to see those ripples since the first pressure wave from the #Tonga eruption arrived on Saturday evening.

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