From Sinuessa to Misenum the coast forms a vast gulf; beyond this is another gulf still larger, which they name the Crater. It is enclosed by the two promontories of Misenum and the Athenæum. It is along the shores of these [two gulfs] that the whole of Campania is situated. This plain is fertile above all others, and entirely surrounded by fruitful hills and the mountains of the Samnites and Osci. (Strabo, Geographica)
Capo Miseno with Vesuvius in the background. Source: https://www.archeoflegrei.it/cosa-vedere-a-miseno-tra-bacoli-e-monte-di-procida/
Volcanology can be traced back to Campania. The first detailed report of an eruption was made here, in the year 79, by an 18-year old boy called Pliny. To avoid confusion with his uncle, a major person in the navy, he was known as Pliny the Younger. Strictly speaking, the additive could have been dropped afterwards since his uncle was one of the many people who died in the eruption. But instead, the name stuck.
People
His uncle is known as Pliny the Elder, which already shows that the boy would go on to make a name for himself. The older Pliny’s full name was Gaius Plinius Secundus (so in a way he also was a ‘younger’). He was a scientist by nature, and produced a huge series (37 volumes – not all survive) called Naturalis Historia (Natural History) which really tried to cover everything – if you wanted to know what use a particular plant was, you could look it up in here. Much of the content came from what was written in other books: Pliny the Elder was the AI of his time. And like modern AI, not all the fact checking was complete. People with umbrella-shaped feet did not really exist. Clearly Pliny the Elder was a voracious reader. Or rather, he was a voracious listener, since he would get his slaves to read the books to him. Glasses did not exist in those days! (In UK Academia, the title ‘Reader’ still exists. It is equivalent to a junior professor in the US, and one step below full professor.) But he also acted on his own curiosity. Pliny the Elder died getting too close to the Vesuvius eruption, both to help people and to get a better look! ‘Fortune favours the Brave’ he reportedly said during the mission.
Pliny the Elder was also a high ranking official in the Roman Empire. He had served in Germany together with Titus, who would later become Emperor. He was a close advisor to another emperor, Vespasian, and he was in charge of the main Roman navy in the Mediterranean, as Prefect of the Fleet. The main base of this fleet (Classis Misenensis) was at Misenum, nowadays known as Miseno, located on the tip of the peninsula southwest of Pozzuoli. Pliny the Younger was staying with him at the time, with his mother. The likely location of the villa was recently identified. The location gave a direct view over the two harbours, the inner harbour for parking ships for the winter (Mare Morto – dead sea), and the outer harbour for exercises. The site also gave a view across the Bay, including Mount Vesuvius, 30 km away.
Site of the (likely) villa of Pliny the Elder at Micenum. Credit: Soprintendenza Archeologia, https://archaeologymag.com/2024/01/roman-villa-linked-to-pliny-the-elder-miseno/
Pliny the Younger’s full name was Gaius Plinius Caecilius Secundus. He was not born with that name, though. His father died early, and he was later adopted by Pliny the Elder, the brother of his mother. Because of that adoption, he changed his name. But that adoption only happened in the will of Pliny the Elder (in which he also inherited the estate). Thus, this was immediately after the eruption of Vesuvius, and during the eruption he wasn’t called ‘Pliny’ yet. After Vesuvius he moved to Rome where he married (we don’t know to whom: he had two or three marriages over his life), became an administrator, later a prosecutor and consul, and finally Governor of a province in Asia Minor where he died, at the age of around 52. We know of him mainly through his many letters. They depict life in and around the senate in Rome, over a time when the Roman Empire slowly became more authoritarian. His letters grow pessimistic towards the end of his life. Rome’s greatest time was also when the faults that would later weaken the empire crept in.
Letters
Two of the letters are about the Vesuvius’s eruption, and especially the death of his uncle, later his late father. Those letters were written around 100 AD, some 20 or 25 years after the events. They were written to his friend Tacitus, who had asked for a detailed account for his book Historiae (Histories). But although we have much of the Histories, the ones detailing events after 70 AD are lost. We have the letters about Vesuvius from Pliny’s own publications, but not from the books for which they were written.
What do the letters say? Let’s see!
petis ut tibi avunculi mei exitum scribam, quo verius tradere posteris possis. gratias ago; nam video morti eius si celebretur a te immortalem gloriam esse propositam.
Of course, they were written in Latin, a language not all VC readers may know. Luckily, translations are readily available:
“LXV – TO TACITUS
Your request that I would send you an account of my uncle’s death, in order to transmit a more exact relation of it to posterity, deserves my acknowledgments; for, if this accident shall be celebrated by your pen, the glory of it, I am well assured, will be rendered forever illustrious. And notwithstanding he perished by a misfortune, which, as it involved at the same time a most beautiful country in ruins, and destroyed so many populous cities, seems to promise him an everlasting remembrance; notwithstanding he has himself composed many and lasting works; yet I am persuaded, the mentioning of him in your immortal writings, will greatly contribute to render his name immortal. ”
And so on. Pliny the Younger was a gifted orator and a beautiful writer, but nowadays we write rather more direct (‘simpler’, some would say) and this style of writing can be hard to read for us. I asked Gemini for a simpler version – simplifying things should be just what AI is written for! It suggested various styles, of which ‘polite professional’ seemed best suited for VC. It even put in headings, which weren’t there in the original. I took them out again. Here we go. The first letter is about the demise of his beloved uncle:
LXV – TO TACITUS
“Thank you for asking me to write down the details of my uncle’s death so future generations can have an accurate account. Honestly, if a writer like you covers this story, I know it will be remembered forever. Even though he died in a massive disaster that wiped out entire cities—which usually keeps a name alive—and even though he wrote plenty of books himself, being mentioned in your work is what will really make him a legend. They say some people are lucky enough to do great things, and others are lucky enough to write about them. My uncle was one of the rare few who did both. I’m more than happy to do this for you; in fact, I would have offered if you hadn’t asked first. At the time, he was in command of the fleet at Misenum.
On August 24th, around 1:00 PM, my mother noticed a very strange cloud and pointed it out to my uncle. He had just finished a cold bath and lunch and was working on his books. He stood up and went to a viewpoint to get a better look. From that distance, we couldn’t tell which mountain the cloud was coming from, though we later found out it was Vesuvius. The cloud looked like a giant pine tree—it shot up like a massive trunk and then spread out into branches. It was sometimes white and sometimes dirty and spotted, depending on whether it was carrying earth or ash.”
“Being a man of science, my uncle thought this was a phenomenon worth investigating up close. He ordered a light galley to be prepped and told me I could come along if I wanted. I told him I’d rather keep working on my studies, and as it happened, he had actually given me a writing assignment earlier.
Just as he was leaving the house, he got a frantic note from Rectina, the wife of Tascus. Her villa was right at the base of the mountain, and there was no way out except by sea. She was terrified and begged him to save her. This changed his whole plan: what started as a scientific trip became a heroic rescue mission.
He launched the large warships and headed straight toward the danger zone to rescue Rectina and many others, as that stretch of coast was very popular. He steered right into the thick of the disaster, completely unafraid, even dictating notes on every shift and shape of the eruption as he saw it.
As they got closer, the ash falling on the ships became hotter and thicker. Then came pieces of pumice and black, charred stones. Suddenly, the water became shallow, and debris from the mountain blocked the shore. His captain urged him to turn back, but my uncle famously said, ‘Fortune favours the brave! Head for Pomponianus at Stabiae.’
They reached Stabiae, where his friend Pomponianus was already loading boats to escape as soon as the wind shifted. My uncle hugged his trembling friend and tried to calm him down. To make everyone feel less nervous, he acted like everything was normal—he went to the baths, sat down for dinner, and was genuinely cheerful (or at least did a very good job of faking it).
Meanwhile, massive sheets of flame and fire were breaking out all over Vesuvius. To ease the panic, my uncle told everyone it was just abandoned villages or farmers’ fires burning out of control. Then, he actually went to sleep; people outside his door could hear his loud snoring.
Eventually, the courtyard outside his room filled up with so much ash and stone that if he had stayed any longer, he would have been trapped. They woke him up, and he joined the rest of the group. They debated whether to stay indoors or try their luck outside, as the whole house was swaying from the constant tremors. They decided to head for the shore, tying pillows to their heads with sheets to protect themselves from the falling rocks.
It was daylight everywhere else, but there it was darker than the deepest night, broken only by torches and flashes of fire. He went down to the water to see if they could escape, but the sea was still way too rough. He laid down on a sailcloth and asked for cold water twice. Then, a smell of sulfur signaled an approaching fire, and his companions scattered. He stood up with the help of two servants but immediately collapsed. I believe the thick fumes blocked his breathing. When light finally returned three days later, they found his body completely intact. He looked less like a dead man and more like someone who was just fast asleep.”
The second letter is about himself, although it still ends with his uncle.
“After my uncle sailed away, I spent the rest of the day studying—since that was why I had stayed behind—followed by a bath, dinner, and a very restless sleep. For many days, we’d been feeling earth tremors, but they didn’t alarm us much because they’re common in this part of Italy. However, that night the shaking became so violent that it felt like everything was being overturned rather than just moved. My mother rushed into my room just as I was getting up to wake her. We sat in the courtyard, and I—with the strange confidence of a teenager—called for a book of Livy and started reading and taking notes as if nothing was wrong.
By 6:00 AM, the light was faint and eerie. The buildings around us were shaking so badly that we were in constant danger of them collapsing. We finally decided to leave the town. A panicked crowd followed us, pushing and shoving as people usually do when they’re terrified. Once we got clear of the houses, we stopped. The carriages we had ordered were rocking back and forth on level ground, and even when we jammed them with stones, they wouldn’t stay still. The sea seemed to be sucked back into itself, leaving sea creatures stranded on the dry sand. On the other side, a terrifying black cloud was shredded by bursts of fire, revealing massive sheets of flame.
Soon, the cloud began to descend and cover the sea. My mother started begging me to leave her and run for it, saying that as a young man I could make it, but she was too old and slow to keep up and didn’t want to be the reason I died. I told her there was no way I was surviving without her. I took her hand and forced her to keep walking. She gave in, but she kept apologizing for slowing me down. Then, the ash began to fall—not a lot at first, but enough to be noticeable.
I looked back and saw a thick, black fog rolling over the land behind us like a flood. I suggested to my mother that we get off the main road while we could still see, so we wouldn’t be trampled by the crowd in the dark. The moment we sat down, total darkness hit. It wasn’t like a moonless night or a cloudy sky; it was like being in a sealed room with the lights turned out.
You could hear the shrieks of women, the crying of babies, and the shouting of men. People were calling out for their parents, children, or spouses, trying to recognize them by their voices. Some were praying for death because they were so afraid of it; others were convinced the gods had abandoned the world and this was the end of everything.
A faint light appeared, but it wasn’t the sun—it was just the fire getting closer. Luckily, the fire stayed a bit of a distance away, and we were plunged back into darkness and heavy falling ash. We had to stand up every few minutes to shake it off, otherwise we would have been buried and crushed by the weight of it.
Eventually, the darkness thinned out into a sort of smoky haze, and the sun actually came out, though it looked sickly and dim, like during an eclipse. Everything we saw was buried in deep ash, looking like a heavy snowfall. We went back to Misenum, and even though we were still shaken and the tremors were continuing, we refused to leave until we heard news about my uncle.”
Locations
The map below indicates the main locations of the events: Misenum (north side of Capo Miseno, indicated by the ship symbol), Stabiae (look for Castellammare di Stabia, eastern tip of the bay), Vesuvius, and of course Pompei. Herculaneum is located at Ercolano. Neither of the latter two are mentioned in the descriptions. They were forgotten after the eruption, deeply buried without survivors. That is typical for major, ancient eruptions: we only have stories from people far enough away to survive, and not from areas where there were no survivors. It can make those eruptions appear less bad than they really were. I think it is one reason why we know so little about the Rinjani eruption – or Iceland’s Eldgja!
Screenshot
Misenum was a major port and cultural centre. Even the emperor would stay here. Nearby Bacoli had a reputation like Las Vegas! The inner bay was separated from the outer one by a spit, through which a channel had been dug. The villa that has been (tentatively) identified as that of Pliny the Elder is located near the Theatrum, along the south side of the outer harbour. The road over which they fled in the morning would have been the Schola Armaturarum. The receding sea which is mentioned would have been the open Mediterranean, on the west side of the peninsula.
Misenum. Source: Wikipedia
Stabiae was another Roman port on the opposite side of the Gulf of Naples. It is known for its seaside villas, used by the Roman elite and strecthing over several kilometers. Misenum could be seen from those villas. There were other wealthy villas a bit in-land, acting as farmhouses often with vineyards. It seems one of those coastal villas that is mentioned in the story of Pomponianus.
Stabiae became buried under ash but was rebuild. The location was too beautiful to surrender to a mere volcano!
Stabiae had not been Pliny’s intended landing point. Pliny the Elder was aiming for the villa of ‘Rectina, wife of Tascus’ but was unable to reach there. We know nothing about them other than the names and that they lived at the base of the mountain. That may have been at Herculaneum but there were villas along much of the coast line. It seems possible that Rectina did not survive. We don’t know what the rest of the Roman fleet that had been send out on the rescue was doing, but presumably they had run into the same problem as Pliny’s smaller (but faster) ship.
Volcanoes
The Romans knew about volcanoes. They also knew that Vesuvius had been a volcano, because of the ash and pumice found in the fields around the summit. But the mountain had not erupted in Roman times. Diodorus Siculus (80–20 BC) reports that the Campanian plain was called “Phlegrean (“fiery”) from the mountain which of old spouted forth a huge fire as Aetna did in Sicily; at this time, however, the mountain is called Vesuvius and shows many signs of the fire which once raged in those ancients times.”
Strabo’s Geographica lists 10 volcanic locations, islands, or features, known in Roman times:
Italy:
- Etna (Sicily): Described as a major volcano.
- Lipari Islands (Aeolian Islands): Including Stromboli and Vulcano.
- Ischia (Pithekoussai): Mentioned as a volcanic island near Naples.
- Vesuvius (Mount Vesuvius): Noted for its volcanic appearance before its famous 79 AD eruption. Campi Flegrei was included in the location
Turkey:
- Catacecaumene (Land of Burned-Out Volcanoes): Located in Asia Minor (modern Turkey).
- Mount Argaeus (Erciyes Dağı): A high mountain in Cappadocia with volcanic activity.
Greece:
- Methana (Peloponnese): A peninsula with hot springs and volcanic vents.
- Thera (Santorini): An island famously known for its ancient caldera eruption.
- Melos (Milos): A volcanic island in the Cyclades.
- Nisyros: A small Greek island with a dormant volcano.
Strabo noted that these areas were known for “fire,” hot springs, or “ignited matters” (sulfur, bitumen), which he accurately attributed to volcanic activity. Interestingly, these volcanoes were mainly non-erupting. The Romans were familiar with Etna and with Stromboli and Vulcano, so knew the eruptions patterns for them. The most damaging one was Etna, but even there the eruptions were manageable. In the words of Virgil (Eneid, Bk. 3), in the free translation of Conington:
“But Etna with her voice of fear
In weltering chaos thunders near.
Now pitchy clouds she belches forth
Of cinders red, and vapour swarth;
And from her caverns lifts on high
Live balls of flame that lick the sky:
Now with more dire convulsion flings
Disploded rocks, her heart’s rent strings,
And lava torrents hurls to-day
A burning gulf of fiery spray.”
2000 years later, that still describes her eruptions pretty well. But there were exceptions. The Romans had experienced only one comparable eruption: Mount Etna in 122 BC. It was an explosive VEI-5 eruption which had pelted Catania with tephra to such a degree that houses collapsed. This eruption formed a large crater at the summit, where the new (currently active) cones later developed. Other than this, the Romans were not familiar with the real dangers of explosive volcanism.
Warnings
There is one clear indication of precursor activity in Pliny’s letters. He writes that “For many days, we’d been feeling earth tremors”. They were ignoring them because earthquakes were common. But it does sound like the activity went beyond the usual.
We know from archaeology that there had been one other warning, albeit not in Misenum. In Pompei, the viaduct that brought in the water had failed, and a new one was being constructed. Models indicate this could have been caused by inflation at Vesuvius. The water viaducts were build with a precise downward slope. Even moderate inflation could have rendered it inoperable by changing the slope, as the viaduct skirted Vesuvius. The problem had been going on for a while, based on the on-going reconstruction.
Route of the Pompei viaduct
There is also evidence of earthquake damage in Pompei. Some of this may be due to the major event in 62 AD, but reconstruction activity in various villas suggests more recent damage.
Eruption
The letters of Pliny the Younger are the only direct description we have of the eruption. It was also the first time such an explosive eruption had been reported in any detail, of what is now called a Plinian eruption. The name does not specify which Pliny!
There is a clear sequence of events. The first eruption that was seen in the early afternoon was a typical large eruption column. It led to Pliny the Elder readying the fleet to help. The message from Rectina came near that time, even though it would have taken a while to arrive. The problems near Pompei started earlier, badly enough to call for help to evacuate. This may have been earthquakes – the letter does not say.
Crossing the Gulf of Naples in the ships of the time would have taken several hours, and probably longer because of the difficult conditions and change of destination. As Pliny the Elder sailed into the Bay, ash fell with pumice and stones at increasing temperatures. This will have been subsequent explosions to the initial one. Finally, the water became shallow and filled with debris. This sounds like pumice rafts. During the afternoon, the eruption had grown into a major one. The wind was on-shore: we know that because Pomponianus was unable to launch his ship because of the wind direction. This may have been caused by the eruption itself: the rising eruption column can pull in ground-level air around it. The letter mentions massive sheets of flame and fire. The cause is not made clear. Most likely it is the hot pumice thrown out by the eruption, causing fires on the flanks. It wasn’t lava, as there is no evidence for lava flows associated with the eruption.
Pliny the Elder slept overnight, but they were in a precarious position in the morning. The ash and tephra layer had grown thick: this may have been a meter or more. Earthquakes were continuous. Climbing out, stones were still falling and they tied pillows to their heads to shield from this! The shore may have been as close as a 100 meters distant. The eruption caused darkness, apart from the lightning flashes, requiring torches. And there he died, whether from exertion or from the sulphurous air is anyone’s guess. The people he was with survived, and fled further. Only two days later (‘the third day’) had conditions improved enough for them to return and find Pliny the Elder’s body.
The story is full of Roman values: courage and fearlessnes, helpfulness, leadership. Pliny the Elder is presented as a typical Roman hero. After all, this letter was written as an In Memoriam for inclusion in the book of Roman History!
The second letter focusses more on the eruption, albeit seen and experienced from 30 km away.
Pliny the Younger picks up his own story on the first afternoon, but apparently caught no further sight of the eruption cloud. While stones were raining down on his uncle out at sea, he continued studying. The tremors, though, continued and became bad overnight. Those were the same tremors that were felt by the party of his uncle across the Gulf. Sometime, perhaps 4am, it became too bad and he and his mother got up. By 6am, they decided to leave as the house was in danger of collapsing from the tremors. The description is vivid: the terrified, fleeing crowd, the ominous black cloud torn by lightning flashes on one side and the retreating sea on the other. By now his uncle lay dying on the distant coast. The retreating sea, by the way, was not the Gulf of Naples which was in the direction of the cloud. It was the sea on the other side of the peninsula. Why was it retreating? It is normally a sign of a tsunami but the letter does not mention this. The sea at Stabiae had been described as ‘rough’. Pyroclastic flows can cause tsunamis even for volcanoes away from the sea: the massive flow across the sea can depress the water and this gives rise to the wave. It happened at Tambora, for instance. Different flows in different places cause interfering waves, made worse by reflections against the coasts. This was possibly the cause of the rough sea. The opposite side of the Misenum peninsula was sheltered from this, but a wave moving into the open sea could have pulled in an out-going current at this coast, lowering the sea here. Of course the water would rise again later, but Pliny did not see this.
Now the black cloud started to descend and ash began to fall, though ‘not a lot at first’. The cloud rolled in off the sea and over the land behind them. This was certainly the outer edge of the collapsing eruption cloud, forming a pyroclastic flow closer to the volcano and a rolling ash cloud here. This cloud was perhaps the reason for the outgoing tsunami wave. Total darkness followed, but Pliny does not mention any heat. And perhaps in this darkness, the sea came back up, unseen. Fleeing people shouted and cried in the sudden night. A strange statement follows, on a light that appeared but wasn’t the Sun but approaching fire, presumably from the direction of the eruption. Had the cloud lifted enough for them to catch a glimpse of Vesuvius?
The cloud came back and ash fell like thick snow. Eventually the Sun managed to get through in a haze and the ashfall lessened or stopped. How long this ‘eventually’ took, the story does not say. Based on the fact that the ash fell at perhaps a centimeter per ten minutes (based on them having to stand up every few minutes), one or two hours seems reasonable. It was still morning but their world had changed. Everything was covered by thick ash, even 30 km away from the mountain. The tremors still continued whilst Vesuvius collapsed into a new crater. Herculaneum and Pompei were lost and buried. His uncle lay dead on a sail, one of many victims for whom fortune and bravery had been no match for the power of the eruption. Pliny the Younger was now an adopted son and heir. And volcanology was born.
Albert (the elder), April 2026
“Had the cloud lifted enough for them to catch a glimpse of Vesuvius?”- I remeber that, during the Merapi eruption back in 2010, people could somehow see the P-flows in the darkness, I have seen that kind of “firelike glow” myself, likely emaneting by such flows in the darkness while waching videos of recent eruptions, maybe I’m wrong and those were actual lava flows.
My love and awe abut volcanoes since my chldhood were probably from rediing these letters from thitd party articles. Great post, thaanks, Albert!
It’s been a while since I’ve commented. I check out the articles from time to time. I really enjoyed your article Albert. I always like when there is something about the volcanic events written by someone who has experienced it from years ago. I still keep tabs on volcanic events around the world. Especially Kilauea & Iceland.
Albert:
Well written article, even though I find my heart saddened. Thank you.
lovely read. from mots the super elder.
VC would not be the same without a super elder mots! Your ‘well done’ is our top accolade
Fanta man just fired our national science board.
Why is the US so afraid of science?
Science destroys the narrative of a whole political ideology within the US as well as corporate interests.
The movement against science start to ramp up with oil execs being scared of green energy. in the same vein, prejudice also lead to education being viewed as a weapon.
In short, intellectualism is gay and liberal
They are not, but if I understand it right it was the only independant science board:
https://www.forbes.com/sites/johndrake/2026/04/25/trump-fired-the-entire-national-science-board-heres-why-that-matters/
Good job Albert. We are left to imagine what was left of the old Vesuvius edifice. The painting on the wall in Pompeii is far too stylized to provide an accurate representation of ii prior to the vent. One wonders if it was itself, a former Somma-Vesuvius construct or whether what we know as Somma today is what remained, a caldera, the Great Cone regenerating within. It’s apparent that the eastern rim has been overflown with the effluent of the succeeding activity since 79 AD.
Just to note that at 18 Pliny the younger was not a “boy”. You could join the roman army typically at 16 and married at 18 (12 for girls). He was a young man and would have been expected to earn his own living outside the monied classes. Note that in my day you could start full time employment at 15 (and most people did) and it was not that uncommon to be a father at 18 in the UK running your own household. For many young men, this is probably preferable to the current system, IMHO. Certainly aged 15 onwards I worked full time during the holidays and I think it was very helpful, if not essential, to my overall education.
Sure. He did get married the next year. But at this time, he was a student and not employed. I wanted to stress his youth. Also note the difference between how he describes his uncle and how himself. In the first letter he honours others: Tacitus in the salutation, and his uncle in the values shown by his actions. In the second letter, he is rather less flattering about himself. Whereas his uncle goes into danger, Pliny the Younger flees – and rather ineffectively as he has to return in the end. His uncle calmness is contrasted against his panic. He describes himself as junior in every respect.
Junior, but that’s how any well brought up person would refer to an ‘elder’ in pretty well all societies worldwide all time (until west late 20 cent). Not a ‘boy’ and not a ‘child’, young man perhaps, aware of inexperience, definitely and probably not a born sailor which his uncle clearly was. In reality its his job to look after his aunt (clearly a bit frail), which he did with success (they lived) in a difficult situation. Not sure how the average 18 year old today would cope in many societies.
Thanks for a very interesting review of Vesuvius. Did you have a label for your very last picture? I’m guessing it’s a post-eruption Vesuvius overlaid on the current landscape?
It is the current landscape. The picture is from https://smv.org/learn/blog/volcano-mount-vesuvius/ and is used in quite a few websites
I see. It doesn’t look like the usual pictures – and actually shows the dangers posed by Vesuvius more clearly!
Great article and translation(s)!
One question I have is the intensity and prolonged earthquake activity might suggest there was a tectonic contribution in addition to the tremor from the volcano/eruption? From the description of the violence of the shocks, these were not your runadamill rock fracturing events commonly associated with an eruption…but rather intense shaking from quakes that were likely on the order of M5’s at least…which other than a caldera-forming event (like Bard) with the trap door repeatedly dropping downward, I’m having trouble visualizing how quakes of this number could be generated strictly by a volcano…especially since it appears quakes were continuing after the start of the eruptive plumes which should have depressurized the entire system?
Bear in mind that there was an earthquake, which severely damaged Pompeii, a decade or more before the big event. They very well might have been magmatic in origin and not tectonic. Hence it took another decade for the pressure below to not only pop the cork, but shatter the entire bottle. With regard to the original Vesuvius edifice, the source article for Albert’s photograph reiterates that evolved out of a Caldera formed by the ancient Somma. When did it become known as Vesuvius? Is there any evidence of a remnant of that structure or can we assume that it’s all been overlaid by the creation of thr Great Cone?
The possibility that the Vesuvius eruption may have happened as part of a rifting event would be interesting, but I’m not sure if there’s any good evidence backing it up. Ongoing caldera collapse of Vesuvius was likely underway during the night, and likely responsible for the increasingly powerful PDC events. Maybe the collapse earthquakes sufficed.
Thank-you Albert for the whole narrative about the original Plinian Eruption!
The eruption has a partially romantic background with the beautiful landscape and Ancient culture surrounding it. Although there are several movies about it, there is none about Pliny (elder and younger). Pliny’s the younger description of the eruption resembles many later attempts until early 19th century for a sophisticated observation of volcanoes. Vesuvius likely had the opportunity to be observed by a skilled writer, while the 122BC eruption of Etna lacked one like that. Added to this the dense neighbourhood of towns/cities to the volcano increased the dramatic development of the eruption for humans.
“there is none about Pliny (elder and younger)”
There does exist a docu-drama called “Pompeii: The Last Day”, that features both of them as part of the characters. I recommend it, found it quite enjoyable.
Pompeii: The Last Day is an excellent early 2000 s BBC production and a childhood memory for me! it haves a unique sound and atmosphere and is excellent showing how terrfying an explosive ( grey ) eruption can be! the volcano vented many many km3 of phonolitic pyroclasts a sign of long dormancy.
Article to be read by me later. But Q:
What is this all about? Never heard of a wuake in that area.
https://www.volcanodiscovery.com/earthquakes/quake-info/22945855/mag4quake-Apr-26-2026-Switzerland-Walenstadt-SG.html
https://www.seismo.ethz.ch/en/earthquakes/switzerland/last-90-days/
Not that rare in CH.
https://earthquakelist.org/switzerland/#major-latest-earthquakes
Earthquakes are known in this region. The largish one of 849 Ad took place here. (“In the year 849, a most significant earthquake occurred, after the first cockcrow, at April 20, a Saturday; and lasted several days. Others followed periodically until the first of June of the same year, early in the morning.”) (Sorry, source behind a paywall – not for public consumption.)
Basel is a known earthquake danger zone: see https://www.volcanocafe.org/the-basel-earthquakes/
Thanks everybody. Objections:
1. ZZDoc’s source gives the Walenstadt quake a 1.4. That sounds normal, so VD’s source might be wrong. USGS btw
2. Rob’s source shows quite clearly that most mentioned quakes are outside of Switzerland. Lugano is right on the frontier to Italy, Geneva on the frontier to France.
3. Albert mentions the famous Basel quake he has written a famous piece about. Basel is in the Rhine Graben. Walenstadt is 157 km from Basel and ~100 km from Schaffhausen.
Addendum> I know the Walenstadt area. If I were there and a quake of more than 4 happened I would get out I guess. It would be news too. It is a pretty tight valley with mountains on both sides of the lake.
The quake was in the news, it was also felt in Austria and Germany, here is the USGS link to it: https://earthquake.usgs.gov/earthquakes/eventpage/us6000ssx8/executive
Maybe this should be corrected > “Gaia Plinius Secundus” Gaia is a female name. Real name:
Gaius Plinius Caecilius Secundus
Indeed, silly mistake on my part. It has now been fixed – thanks!
For an astrophysicist it’s not a silly mistake I guess as an astrophysicist might use Gaia much more frequently than Latin authors’ names.
M3 at Bardarbunga. Is a Tomas event around the corner? Tomas predicted one in the near future
I somehow missed this comment, so I dropped one below instead. I suspect that Bárdarbunga is planning a May Day parade of its own.
– and destroyed so many populous cities, Pliny translation
did he really write “many”?
– Even though he died in a massive disaster that wiped out entire cities
ENTIRE CITIES
Maybe there is more underneath Naples or Pozzuoli. Is that possible?
The list of cities that existed in this region according to Strabo include Heraclæum, Pompeia, Nola, Nuceria, Acerræ, and Surrentum. There are more names but I don’t know whether they were in the same region, and smaller settlements are mentioned but not named. Stabiae is not mentioned, so may have started a bit later.
Having read the vivid Pliny description I tend to siding with the academics who believe it was a lower VEI 6.
Thanks for the piece and Pliny’s description.
I think it is hilarious the the Elder went to take a nap, fatal for him.
I’ve spent the last few (x2) years watching from afar but still love reading all your posts. Been patiently waiting for Lady H to say hello and wondering if that time will be soon. Could be a busy year ahead for Iceland 🤗
My link to the borehole strain meters for Hekla is very old and hasn’t worked for a few years now. Does anyone have a more current one with the seismometer readings as well? 🙏 Many thanks in advance
Fedgar is the nearest to Hekla I think
The chrome browser doesn’t like the address because it has no https, I use a common Samsung browser, that works with http.
http://hraun.vedur.is/ja/hekla/
Borehole strain maesurements are still online, but again use http adress, not the https, and NOT in chrome.
Gps around hekla
https://brunnur.vedur.is/gps/hekla.html
Works with s 😃
Cheers Inannamoon! 🙂
The first link doesn’t appear : one more try
hraun.vedur.is/ja/drumplot/drumplot/fed_highpass_2.0.png
link address should now show. Copy and add http:// at the front, and use a browser that still allows http rather than https – admin
Dragons!!! 🪠🪚🔨🪛 please help….
done. wp seems to block direct links to non-encrypted png files ?
Thank you 😊
More very weak rumbling around Hekla. Very weak meaning almost non-existent.
Very few that are verified. Until they are, I consider them non-existent 🙂
While we’re in Iceland, I think Bárdarbunga should be ready to deliver a nice M5 any day now. It will be interesting to see how the SeisComP system will handle it. The old system usually reported a much smaller quake that got upgraded after manual inspection. Most of those manual M5 assessments have been lost in the transfer of the catalogue to the new system, turning them into measly M4s.
The last eruption of Bardarbunga’s central volcano was on November 6th 1996 in the final days of Gjàlp. It lasted only ~30 minutes, but it was an eruption.
Bardarbunga historically did several subglacial eruptions. So we can’t exclude that an actual small eruption of Bardarbunga will stay below the surface of its glacier.
Thomas: was the intense crazy Bardarbunga earthquake swarm in the caldera last year a small subglacial ring fault eruption that never reached the surface? you can have a very small event that does not reach the surface or deform the ice above it.
I think that swarm was a cone sheet intrusion, but I doubt it made it all the way to the surface. That said, I think a small eruption from a cone sheet reaching the surface is a very real possibility with Bárdarbunga. Such an eruption would likely be small (VEI2?) and short lived.
Also Torfajökull often has earthquakes. Maybe Hekla is going to to an unusual fissure zone eruption towards Torfajökull? An eruption like this would be of pure Hawaiian type (effusive) unlike the famous eruptions on Hekla’s cone.
Hekla’s fissure swarm is oriented SW-NE, so a fissure towards Torfajökull is highly unlikely. A fissure eruption on Hekla’s own fissure swarm would probably induce trigger quakes at Torfajökull, just like Fagradalsfjall and Svartsengi generate trigger quakes in neighboring systems.
Hekla’s fissure swarm is wider south of the mountain, which makes up the Vatnafjöll of its alternative name, “Hekla-Vatnafjöll”. Though all fissures, like those of Hekla, are oriented SW-NE, fissures in this area could, theoretically, extend into Torfajökull’s central volcano (though not the caldera), but they’d very likely miss the latter’s magma chamber. These eruptions would thus be effusive, unlike if they were to occur on Hekla itself or if the magma were to intersect Torfajökull’s chamber. Torfajökull’s own fissure swarm is oriented SW-NE, with an additional area N. The latter is shared with Hekla.
So technically a fissure from Hekla to Torfajökull is possible, but to what extent and its significance depends on the location. Into Torfajökull’s north swarm wouldn’t be significant because it’s shared anyway; in the central volcano from the Vatnafjöll subsystem would carry some significance, but less so than if Bárðarbunga were to spring a leak, intrude into Torfajökull and almost inevitably hits the magma chamber.
The Catalogue of Icelandic volcanoes says: “During the Holocene the Torfajökull system has erupted only when triggered by dyke intrusions propagating from two adjacent volcanic systems, the Hekla-Vatnafjöll system to the west and Bárðarbunga to the northeast. The fissure swarms of these two systems transect the western part of Torfajökull central volcano and its caldera. ”
“Four Holocene eruptions have occurred where Hekla-Vatnafjöll fissure swarm intersects Torfajökull system. At least 8 Holocene eruptions have occurred at the intersection of Bárðarbunga swarm and Torfajökull. ”
100% of all Holocene Torfajökull eruptions were caused by dyke intrusions from Hekla-Vatnafjöll or Bardarbunga. Hekla-Vatnafjöll caused 1/3, Bardarbunga 2/3 of the eruptions. Precursory signs of Torfajökull’s eruptions occur therefore in one of both neighbouring systems.
A single area of roiling dome lava fountains on Io ( a huge mess of fluid lava lake upwellings at diffirent scales ) maybe be as wide as the whole vesuvious area in some of the Ionian lava lake vents. I wants to write some more articles on Io and specialy all the eruptions on Io since Galileo left in 2000 s until 2026, but thats simply too large project to cover in detail its simply too active. But there will be more Ionian stuff later from me.
https://iopscience.iop.org/article/10.3847/PSJ/ae52ee?fbclid=IwRlRTSARccd9leHRuA2FlbQIxMQBzcnRjBmFwcF9pZAo2NjI4NTY4Mzc5AAEefrzBKWWAe32L4FkwO_AnT36OEkB8icfEyd_2xh3thsz649rSDbJGYXRPPFE_aem_JCXYlMmNjKyP-iq_5vDoyw
New paper on Ionian lava lake crust thermal emissions
As I mentioned a while back following the M7.4 off the NE coast of Honshu, that a seismic gap off the SW and E coast of Hokkaido would be an area to watch. And now a M6.1 inland of eastern Hokkaido just happened along a sharply dipping thrust fault (~83 deg dip). For a fault that steep to let loose suggests a lot of stress is present in the area. My fear is this new shock is far enough from the M7.4 that a new seismic gap may be emerging. If so, then the gap appears capable of generating at least an M8+ should it fail all at once?
We shall see, but the activity over the last week or so is suggesting the area north of the Tohoku M9.1 is becoming increasingly unstable.
How far from japan is the centre of that potential gap?
Immediately east of Hokkaido which is the most northern “major” island of Japan. There’s a conspicuous absence of major quakes stretching for at least 300 miles at the southern end of the Kuril/Kamchatka trench. The region is not totally aseismic with several M7’s and high 6’s in the last century, but none of the M8’s that the region has historically generated.
https://earthquake.usgs.gov/earthquakes/tectonic/images/kuril_tsum.pdf
Interesting, presume you mean around the 50 degrees north line. The sea of Okhotsk also seems to have a bit of a gap on that map to the north west. But i am a bit confused about the label saying “north america plate” some AI translation involved maybe?
No…the apparent gap (low seismicity) I’m referring to is around 42N – 44N just east of Hokkaido west of the Kuril/Kamchatka trench. 50N is off Kamchatka.
But also note the dates of all the major events M8 and above. Bracketing this part of the KK trench, there were M8’s in 1994 (to the south) and 2003 (to the north). In between, there’s been nothing of consequence for decades..perhaps more than century…and with ~ 91mm plate motion, it must be close to being fully loaded.
Plus, note the apparent cluster of M8’s between the years of 1952 and 1960 all along the KK trench..5 in total with 3 occurring just in 1952 alone. GIven the histories elsewhere of clusters or pairs of main shocks off Japan, stress transfer seems to be unusually efficient.
And lastly, there was only 15 years between mega thrust M9’s+ along the same generalized tectonic boundary. (Tohoku and Kamchatka). Is there a linkage? Directly, probably not…but then again, 1952 was a very interesting year, since there has been now been 6 M9+ earthquakes since 1952…way more than the 1-3 M9’s / century long term average.
Interesting and not easily understood as the main plate borders (red dashed lines) are found here:
substackcdn.com/image/fetch/$s_!iLyY!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4fd2f181-15ab-488b-ae58-2255f8a93351_800x858.jpeg
Craig:
I asked Google’s Gemini AI about these “earthquake gaps” and it replies
Query successful
As of late April 2026, the seismic situation in Japan is highly active, specifically concerning the Japan Trench (northeast coast) and the long-monitored Nankai Trough (southwest coast).
The most critical recent development is a Special Advisory issued by the Japan Meteorological Agency (JMA) following a major event on April 20, 2026.
1. Recent Major Event: The Sanriku Offshore Earthquake (April 20, 2026)
On April 20, 2026, a magnitude 7.7 earthquake struck off the coast of Iwate Prefecture (Sanriku region) at 4:53 p.m. local time.
JMA Advisory: For the second time in six months, the JMA issued an “Off the Coast of Hokkaido and Sanriku Subsequent Earthquake Advisory.”
Increased Risk: The JMA stated the probability of a magnitude 8.0 or larger “megaquake” in the region is now roughly 1% (ten times higher than the normal 0.1% baseline) for the week following the event.
Scope: The advisory covers 182 municipalities from Hokkaido to Chiba Prefecture. Residents have been urged to maintain high readiness, though not necessarily to evacuate unless a new tremor occurs.
2. Status of Major Seismic Gaps
Seismic gaps—areas along active plate boundaries that have not experienced a major rupture for a long time—are the primary focus of JMA’s long-term monitoring.
Region Current Status / Latest Findings
Nankai Trough The “Big One” gap. Historically ruptures every 100–150 years; the last major events were in 1944 and 1946. The JMA maintains a 70–80% probability of a M8–M9 event within the next 30 years. Experts are currently monitoring “slow slip” events which can precede a major rupture.
Japan Trench (Northern) The April 2026 M7.7 quake occurred in this zone. While the 2011 Tohoku quake relieved stress in the central section, the northern sections (off Aomori/Iwate) and southern sections (off Ibaraki/Chiba) are still considered high-risk gaps.
Sagami Trough Located directly beneath the Kanto/Tokyo region. This gap has not seen a major rupture since the 1923 Great Kanto Earthquake. It remains a top priority for JMA’s urban disaster prevention.
Hokkaido (Kuril Trench) A “megaquake” gap off the coast of eastern Hokkaido (Tokachi/Nemuro). Recent research suggests a cycle of massive M9-class tsunamis every 300–400 years; the last was roughly 400 years ago, making this gap critically overdue.
3. Official JMA Publications & Systems
The JMA has recently refined its communication protocols to avoid “false alarm” fatigue while ensuring safety:
Subsequent Earthquake Advisory System: This is a relatively new protocol (fully active since 2022/2023) used when a M7+ quake occurs near the Japan or Chishima Trenches. It acknowledges that roughly 1 in 100 M7 quakes are followed by a M8+ “megaquake.”
Extra Information (Nankai Trough): JMA publishes “Nankai Trough Earthquake Extra Information” if anomalous crustal deformation or a M6.8+ quake is detected along the trough.
Real-time Monitoring: You can find the latest live “Seismic Intensity” maps and active advisories on the JMA English Portal.
Note: These advisories are not “predictions” of a specific time or date, but rather statistical warnings that the geological conditions for a massive rupture are currently elevated. The JMA advises checking emergency kits and confirming evacuation routes immediately.
Thank you! As I mentioned, the area east of Hokkaido is a ticking time bomb.
While long term averages suggest that M7+ quakes in the region have a 1:100 chance to turn out to be foreshocks, there are clear indications that those moderate/strong quakes off Japan and Kamchatka/Kuril’s becoming foreshocks seem to come in clusters. Both Tohoku and the Kamchatka mega-thrust’s were preceded by strong foreshocks weeks/months beforehand.
But also note, the upcoming/expected Tokai earthquake near Shizuoka is also primed…which did not rupture from the twin M8’s on the Nankai trough further south in 1944 and 1946 . The Tokai zone of the Nankai trough is now way overdue based on past activity… similar to the gap off Hokkaido. Due to much higher population centers nearby, the potential impacts from a Tokai mega-thrust has to be considered the most worrisome.
79 AD Vesvuiuv erupted with a VEI5 after a pause of 300 years.
476 did a VEI5 again, but was preceded by a smaller VEI2 80 years before. The same happened 1631 again, this VEI5 was preceded by a VEI2 60 years before in 1570. In both cases the VEI2 happened after a centuries long dorman period. This shows that the next eruption of Vesuvius doesn’t have to be a VEI5, but can also be a smaller one.
However, I’d assume that the 21st century won’t have any eruptions of Vesuvius. The post-eruption caldera sinking earthquakes lasted too long. The volcano has likely reached its deflation minimum and needs to fill up slowly again.
On the topic of Torfajokull, out of all the years reading about Volcanoes and following this blog, I will say one mystery think is a bit underrated is the nature of Iceland’s large calderas and how they were created. And while this includes all the calderas in Iceland, I am more specifically referring to the large calderas that were likely not formed gradually / from slow piecemeal expansion after frequent recurring eruptions slowly expanded the footprint of the caldera.
The caldera is approximately 18 km × 12 km. By most standards, that’s enormous. IF that formed in a single eruption, it would represent the displacement of a mid-sized VEI-7 eruption’s worth of magma, which would qualify it to be as large as the largest eruptions of the entire Holocene period. Now, it’s of course very possible that this is actually a series of smaller calderas that gradually formed over the years, and the footprint of those calderas collectively covered an area 18 x 12 km. But even if this were a piecemeal caldera born from multiple eruptions, we should see eruption traces that are much larger than what we know of.
To this day, all that we have for comparison is the Thorsmork ignimbrite, which is typically viewed as a VEI-6 in size, although that size is not well-constrained. But that eruption …if it were only VEI-6, would not be nearly large enough to produce a caldera of this size. The Tambora eruption which was much larger by comparison produced a caldera that’s approximately 6×6 km in size. A caldera that’s 18×12 km is at minimum, more than 5x larger than that. That’s enormous, and we do not have any knowledge of what the origin of this was.
Were there simply a lot of VEI-5/6 eruptions over the millenia that gradually caused this to grow? Was this originally a volcano that erupted effusively, only to later transition to an older volcano that only gets triggered by intrusions from neighboring volcanoes’ rift eruptions? Or perhaps are we underestimating how effective the glacial environment was at hiding the evidence of large eruptions such as Thorsmork, thus making them look far smaller than they actually were?
You can apply similar questions to other Icelandic caldera systems. Given, we know more that calderas like Katla’s were piecemeal to some extent, but what about ones like Hofsjokull, or Tungnafellsjökull, etc.
If the explanation here is that Icelandic calderas formed and got to this size from repeat effusive eruptions (be it rift eruptions, or repeat mid-sized explosive eruptions ala Katla), then why do we not find any predominantly effusive volcanoes in the world with calderas even close to this size? There are plenty of calderas around the world that form from effusive gravity-fed draining events similar to what we saw at Bardarbunga, or likely other rifting fissure eruptions in Iceland. Yet outside Iceland, the typical caldera size for volcanoes of this nature doesn’t get much larger than 2km in width. Even Erta Ale, which is has production characteristics similar to an Icelandic central volcano only has a small 1.5km summit caldera.
I don’t know the answers here, but my only thought is that we are quite possibly / quite likely missing a significant chunk of eruptive history in places like Iceland, and we don’t really know the full story of how these things formed.
Please excuse the bad wording / grammar in the post above, wrote this fairly quickly, and didn’t get to read it through before posting.
See https://avo.alaska.edu/volcano/okmok. Very large caldera.
We know there are some rhyolitic pockets in some systems of iceland, is it possible that in the distant past that there was a very large rhyolitc CFE from this and the evidence was bulldozed away by erosion and glaciation events?
Have you seen this article:
https://cp.copernicus.org/articles/18/485/2022/
The Vedde Ash is Katla’s and NAAZ II is thought to be from Torfajökull.
The NAAZ II association is (I think) mainly because of the lack of another candidate. It was deposited during a phase of rapid ice growth, and so may include ash collected on the ice over a longer period. Torfajokul is a funny caldera. The shape isn’t entirely round: it is a bit elongated along the northwest-southeast direction, close to the spreading motion in Iceland. This suggests to me that it once was located on the spreading centre. There are similar calderas in the East Africa Rift system. Extension allows magma chambers to grow larger (and mature), and the spreading allows easier collapse after magma withdrawal.
Thats a good point! Does this mean Caldera’s in rifting areas have the potential to be deceivingly large in size relative to the magnitude of the explosive silicic volcanism involved in creating them. As far as I know Torfajokull is on the largest deposits of silicic rocks in Iceland, could a large rhyolitic plinian eruption have happened that opened the flood gates for the much larger basalt volume to flow out and lead to caldera collapse?
I feel like the vedde ash has gone back and forth quite a bit regarding the source. I would definitely not say i’m up to date on it, but would add that if it’s NOT from Torfajokull, that only adds more mystery to how we have a gigantic rhyolitic caldera in Iceland that has no easily identifiable source ignimbrites.
Thanks for sharing the article, always enjoy more of the ash record history data.
Hector, the list here would imply that the Vedde Ash is responsible for the #1 ranked eruption on the entire list here..? If so, that would imply that the magnitude of the vedde ash eruption is drastically under-reported.
Given, I recognize that proximity to Greenland skews this data a bit along with potential variation of sulfur deposits in the eruption gas. But at the minimum, this would imply a much much larger eruption than the common VEI-5/VEI-6 estimates we see. Provided that this is true, this should also provide some insight into the difficulty of mapping eruption deposits in glacial environments, especially where deglaciation has occurred between the time of the initial eruption and the current timeframe.
I think you mean the NAAZ II (North Atlantic Ash Zone II layer) eruption, which indeed, is thought to be the largest sulfate event of the last 60,000 years.
Regarding the Vedde Ash of Katla, I know a person who got a very rough estimate with isopaches using sparse locations of known thickness, and the ash fallout volume turned out to be 60 km3, with likely a similar additional volume of ignimbrite that got turned into super-lahars when landing on the km-thick glaciers. NAAZ II has 5 times the amount of sulfate deposition in Greenland the Vedde Ash has.
Sorry, I think I was mixing up the Vedde ash with the Thorsmork Ignimbrite. I meant to say the Thorsmork ignimbrite here, not Vedde.
Snaehetta caldera also is enormous.
Buried under the Vatnajokull ice cap.
About 80-90% of the population of Pompei is supposed to have survived the eruption.
That is a lot.
It shines a light on Pliny the Elder’s death as unnecessary. If he had’nt slept he might have survived. Pliny the Elder obviously underestimated the forces and the poisonous gas which is strange considering that they knew Etna.
And he overestimated himself whereas his nephew was the cautious one.
Today, we have a totally different problem: Too many people. In any event, be it Campi Flegrei, be it Vesuvius, they would get stuck on the highways.
Then there is Epomeo, also quite difficult to save everybody esp. in the south in the case of a bigger event.
The best way to survive an eruption like that is follow Lurking’s motto ‘don’t be there’. Either evacuate on time, or don’t be there in the first place. Both have difficulties. In principle, any volcano like this should have a permanent 30-km exclusion zone, like a volcanic Chernobyl. But people do not recognise the danger and will move in. Evacuations are time-limited. People want to return home after a week, and won’t want to evacuate twice. So accurate forecasts are needed and that is something volcanoes don’t easily do. At St Helens, both tourists and workers had moved back in to the evacuation zone in force. It exploded on a Sunday, which meant the loggers weren’t at work, but on the other hand, tourists invite Sunday dangers. So yes, I think Naples is a high-risk area. As in Henrik’s post on Campi Flegrei.
Ischia, interesting piece with plenty pics of rock formations and descritpion of the understanding of the eruption 55 ka.
“A substantial magma chamber, similar to
that under Ischia prior to ∼55 ka, is not thought to presently
exist at depth (e.g., Piochi et al. 1999). Future eruptions on
Ischia will probably be of a similar low magnitude and
impact to that which has characterised Holocene volcanism.
However, an imperfect understanding of the long-term
evolution of the magmatic system beneath Ischia means
that we lack information on the repose periods of MEGT-
type eruptions on Ischia and also on what may trigger such
destructive events. It seems expedient for future research to
explore these themes.”
https://www.researchgate.net/publication/225466423_New_insights_into_Late_Pleistocene_explosive_volcanic_activity_and_caldera_formation_on_Ischia_southern_Italy
Il Fungo, Ischia:
Kilauea’s earthquakes accumulate now “mostly under the pre-2018 location of Halemaʻumaʻu crater” https://www.usgs.gov/volcanoes/kilauea/volcano-updates
Do they precede a return of a lava lake like the one 2008-2018?
https://www.usgs.gov/volcanoes/kilauea/science/chronology-kilaueas-summit-eruption-2008-2018
“Do they precede a return of a lava lake like the one 2008-2018?”
Looks like we might be in for that.
The ponded lava in the caldera also remains molten. During fountain episodes, it looks like the surface flow founders the thin crust near the edges of the massive ponded lava lake, while lifting the center from below. After the episode is over the crustal overturning front continues to advance beyond the surface flow. If the 2008-2018 conduit does return, then we will have a convecting lava lake connected to a massive ponded lava lake, and thus a situation akin to that of the early 19th century…
I’m also increasingly wondering if the ponded lake will soon drain catastrophically down the SWRZ the way it happened in 1823, given how the floor is now quite high.
I wouldn’t be so sure.
I asked the USGS about this a little while ago; they were pretty convinced that the 2018 collapse had completely destroyed the conduit system that supplied magma to the lava lake.
Another lake is far from impossible – but the magma would have a different source and conduit.
HVO counted 96 earthquakes yesterday “primarily within Halemaʻumaʻu crater and south/southwest of the caldera”
A difference between now and 2008-2018 is that we are at a higher level of magma inflow into the summit. The 2008-2018 eruption was predominantly a net zero eruption. If the voluminous eruptions/intrusions since 2023 continue during the formation of a new Halema’uma’u lava lake, the lake will likely be more aggressive than 2008-2018. Maybe a lava lake with many voluminous overflows on the caldera floor.
The 1986 Kupaianaha (Pu’u O’o) eruption might be an example about how a new Halema’uma’u lava lake can look like. Imagine all the lava flows of Kupaianaha, that traveled towards the ocean 1986, would accumulate in the summit caldera.
It is not in a hurry to build up to the next eruption. The tilt shows a deep DI event, the second since the last episode. let’s see whether the volume to support such a scenario is still there.
HVO observed: “UWD is recording slight deflationary tilt”. The same applies to SMC, while IKI tiltmeter has flat deformation.
Does this indicate slow intrusive activity?
HVO is forecasting May 5 to May 9
No, the opposite: it is a DI event leading to deflation, so extrusive. It is one of the stronger such events in recent months, ‘slight’ in comparison with the preceding post-eruption inflation but strong enough that HVO has added 3-4 delay to the predicted next episode.
In which cases does an intrusion do a deflation like in winter 2024?
This deflation was linked to a voluminous intrusion into SWRZ: https://www.usgs.gov/observatories/hvo/news/volcano-watch-another-intrusion-southwest-kilaueas-summit
Such “deflating” intrusion would be because magma goes into one of the rift zones from either magma chamber (south caldera both into the ERZ and seismic SWRZ; Halema’uma’u into volcanic SWRZ). You’d see inflation there, while the rift zones currently are anything but active. It’d be a sudden inflation, too, not slow-acting like the periods of deflation we’ve had in the summit region for several months now between episode intervals (I remain hesitant to call them D/I cycles, because the HVO hasn’t referred to these as such yet in any of the updates in this eruption, unlike the first two eruptions since the caldera collapse), and of course plenty of earthquake activity along the path it takes.
DI events showed a fast onset of deflation, slowing down after while and sometimes settling on a plateau, before a sudden, fast onset of inflation, again slowing down over time and ending when the original tilt was reached. Sometimes, the DI event started with a burb, a quick increase followed by the start of the DI.
The current events show very similar profiles, with as main difference that they occur against a backdrop of rather fast inflation. Looking at the plot the onset is sudden, the ‘plateau’ is not always present but when it does, it shows the same slope as the average behaviour before and after the DI event. It is most obvious at 2/11 in the plot. The start of inflation is also sudden. The burb is visible only once, at the start of the event at 2/11. The event around 03/23 is a bit different so may be something different, but it could also a very long-lived DI event. Overall, I think there is a good case that they will turn out to be the same type of event. I expect they are caused by gas rather than magma, where gas pressure declines and later returns.
The current situation has become a bit different, with a continuing low-level swarm of earthquakes underneath the caldera. The system is not as happy as before. It will be interesting to see whether that causes any changes
Do we know how the inflation in the Kupaianaha region looked like before the actual eruption 1986? There must have been a process of magma seeking and finding its way to the surface there on a different location than the episodic Pu’u O’o 1983-1986. If the summit is going towards a “Kupaianaha eruption” in the calderea in near future, the build-up towards it should resemble something of 1986. As the Kupaianaha eruption wasn’t far from the original (and later) Pu’u O’o, the current summit eruption isn’t far from the traditional Halema’uma’u lava lake location.
Meanwhile Mauna Loa shows a significantly positive deformation, but it’s uncertain how much the recent storm weather disturbed the data.
I wants to write more explaining articles on Io
I just dont know exactly what subject to cover
Following up on what Craig Heden posted, here is what Gemini Flash 3 Ai has to say:
Let’s talk about Hokkaido (Kuril Trench). Can you access any good information which indicates how close we are due to a major magnitude 8 or 9 earthquake?
Query successful
The Kuril Trench (Chishima Trench), which runs off the eastern coast of Hokkaido, is currently one of the most scrutinized seismic zones in the world. As of April 30, 2026, the situation has moved from “theoretical concern” to “active monitoring” due to several recent events and research breakthroughs.
Here is the breakdown of why experts believe a magnitude 8 or 9 is effectively “due at any time.”
1. The 400-Year Cycle is “Mature”
The primary reason for the high alert level is the historical record. Paleoseismologists (who study ancient quakes via soil and sediment) have identified a recurring pattern of massive “mega-tsunamis” in eastern Hokkaido.
The Interval: These M9-class “superquakes” occur roughly every 340 to 380 years.
The Last Event: The last one occurred in the early 17th century (approx. 1611–1637).
Current Status: We are now approximately 400 years past the last event. Statistically, the region has exceeded its typical “quiet” period, leading the JMA and the University of Shizuoka to describe the energy buildup as being in a “mature stage.”
2. Recent Research: “Energy Buildup at Any Time”
As of February 2026, researchers from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) published findings using new seafloor pressure sensors and GNSS-A (Global Navigation Satellite System-Acoustic) monitoring.
Constant Accumulation: Data from 2000–2025 shows that the Pacific Plate is subducting beneath Hokkaido at a rate of roughly 8–9 cm per year.
Locked Zones: The research identified specific zones off the coast of Tokachi and Nemuro where the plates are “stuck” (locked). Instead of sliding smoothly, they are bending and storing massive amounts of elastic energy.
Conclusion: Scientists warned that the energy stored is now sufficient to trigger a magnitude 8.8 to 9.1 earthquake.
3. Latest Official Probability (April 2026)
The Japanese Government’s Earthquake Research Committee maintains a rolling 30-year probability. However, following the M7.5 Sanriku earthquake on April 20, 2026, the JMA took the rare step of issuing an active advisory.
Type of Earthquake Location 30-Year Probability
M8.8 or larger (Megaquake) Kuril Trench (off Tokachi/Nemuro) 7% to 40%
M7.8 – M8.5 (Great Quake) Nemuro-oki section ~80%
M7.8 – M8.5 (Great Quake) Tokachi-oki section ~60%
Current Temporary Alert: Because of the M7.5 quake nearby on April 20, the JMA stated that the risk of a M8+ event occurring in the immediate term is 10 times higher than normal (rising to a 1% chance over the span of a single week).
4. Expected Impact of a Kuril Trench M9
The JMA’s modeling for a worst-case scenario in this gap is severe:
Tsunami Height: Potential for waves exceeding 30 meters (98 feet) hitting the eastern Hokkaido coast (cities like Kushiro and Nemuro).
Tsunami Arrival: Waves could reach the shore in as little as 10–20 minutes after the shaking stops.
Shaking: Expected seismic intensity of 7 (the highest on the Japanese scale) across eastern Hokkaido.
Summary of the “Gap”
The Kuril Trench gap is no longer considered a “slow-moving” threat. Between the 400-year cycle being overdue and the recent M7.5 event in the adjacent Japan Trench, the JMA is operating under the assumption that the plate interface could rupture without further warning.
This is of course very good. But so is wikipedia. I tried the same query and it gave largely the same information, albeit with some missing aspects that I guess it gave you because of carrying the words ‘seismic gap’ from your previous query. It also reduced the tsunami height from 30 meters to you, to up to 20-24 meter to me.
But no actual references so it is not ‘authorative’
Thank you for the additional info, Randall! Based on this querry and the one you posted earlier, it all confirms that another major tectonic event is becoming increasingly likely off Japan.
I do not use advanced AI at present but it appears I may have to get with the times!
This does summarize what I know quite well, although this is the first I’m hearing of a “cycle”. The situation is indeed quite dire. Whether the region takes weeks or years to ultimately rupture, the time for thorough preparation is now.
Might be wise to ask the local Ainu what they know about how tsunamis behave in the area.
I’m also curious what, if any, influence large earthquakes here have on caldera formation. Kitcharo, Mashu, and Akan are all in eastern Hokkaido.
*Kutcharo
Just a general observation, not linked to anything you’ve said beyond the first sentence.
As a professional in the field, anyone caught using a general AI for such a purpose would (metaphorically) be taken out and shot!
What is the meaning of the 1944 eruption of Vesuvius? Was it the “concluding eruption” of an eruption cycle since 1631?
1944 was only a VEI3, but shows how dangerous a VEI3 can be in some places. Vesuvius killed 26 people 1944.
Thanks for posting this link.
It’s been decades since I watched this news reel about the 1944 eruption of Vesuvius. Always a thrill to watch!
The video also shows that the summit looked different until the 1944 eruption than now. There was a cinder cone in the crater of the big cone. Now there is only a big crater. The explosive eruption blew the cinder cone in the air.
Interesting is that the eruption was both Plinian and Hawaiian. A voluminous impressive ash plume and thin Pāhoehoe lava. Unlike this the Plinius eruption 79 AD was without an effusive part, as far as we know. There are sometimes purely explosive eruptions of Vesuvius, and sometimes mixed explosive-effusive eruptions with each part strong and dangerous. Was the 79 AD eruption predominantly Phonolite, while 1944 was a primitive alkali magma (f.e. Tephrite)?
It’s clear from your observation of the cinder cone that some of that volcano eruption footage was stocked from other sources. The images of Pompeii certainly support that. The cone in the crater took me bysurprise, even as a young child more than 70decades ago when I first viewed this documentary.Hence,I wonder about the veracity of thst pahoehoe.
In retrospect, the cinder cone Jesper commented on may have been destroyed in 1929, not 1944.
Vesuvious produces highly fluid tephriphonolitic magmas here is boiling 1929 lava lake with nice lava waves. This is very fluid magma perhaps as fluid as Nyiramuragira but Nyiramuragira maybe a but lower still in viscosity but chemicaly its quite close to Nyiramuragira just that Vesuvio is sligtly more evolved on the TAS plot but its very fluid thats saied its likley more crystal rich than Kilauea and Nyiragongo with many strange crystals including lecuite
https://m.youtube.com/watch?v=-7W6BAV0wmw&pp=ygUOdmVzdXZpb3VzIDE5Mjk%3D
The lave which wrecked San Sebastiano is certainly not fluid.
Thats because thats the Aa flow front and all fluid lavas including Kilauea and Nyiragongo often looks like that during fast open lava channels a few kilometers from the vent, it cools and becomes a rubbly mess. The vent for the 1944 destruction flow likey flowed very smoothly and lamminar in huge open channels before it turned into Aa
P. lava turns fast into Aa lava, if the lava flow enters flat land. Vesuvius is a small volcano, its lava flows quickly reach to flat landscape on sedimentary ground.
Bardarbunga: KISA (NW of Bardarbunga) is running north, while VONC (between Bardarbunga and Tungnafellsjökull) had significant inflation in summer:
Note that you have different time scale for the two stations. Look at the full history of VONC and see that it’s the same trend as previous years. The slight increase in uplift during the summers is because of reduced ice load from the glacier. It’s a yearly pattern.
One thing I find interesting in the KISA plot is the clear acceleration after January 2024. That’s when there was an M4 quake at Grimsvötn. Grimsvötn also changed direction at the same time. On the horizontal component it looks like it’s currently deflating! Is Bárðarbunga stealing all the magma?
USGS has updated its forecast for Kilauea: “Episode 46, forecast by USGS sometime between Saturday, May 2 and Wednesday, May 6.”
Just had a look at the feed from the V3 camera. It appears that the south vent may carry the load for this one. Time will tell, of course.
The eruption window has shifted to “between Tuesday, May 5 and Saturday, May 9”. The shallow earthquakes below Halema’uma’u continue with a number of 23 yesterday.
Yes, it appears they’ve moved it back again
M5.7 earthquake on Nara-Wakayama border. Seeing depths reported anywhere from 50-70 km.
Does anyone know the depth of the subducted plate at that location (and also where I can find that data myself instead of asking)?
Slightly concerned that this may be a very early sign of the Nankai Trough reawakening. Nowhere near as concerning as the situation in Hokkaido and the Kuriles, as mentioned elsewhere in the comments, however.
New post is up! Not ‘new’ as such, but an older post which is well worth re-reading, if you like Iceland, ignimbrite and enigmas. And calderas.
https://www.volcanocafe.org/an-iceland-enigma-the-thorsmork-ignimbrite-2/