The Vesuvius Eruption of 79 AD: What Happened and What You Can See

Vesuvius erupted in AD 79 and, in less than two days, buried the Roman towns of Pompeii, Herculaneum and Stabiae. For centuries the date was given as 24 August, the day recorded in the surviving text of Pliny the Younger’s eyewitness letter. The Osservatorio Vesuviano, the Naples section of Italy’s national institute of geophysics and volcanology (INGV), now dates the eruption to 24 October AD 79, and a charcoal inscription found at Pompeii is the main reason why.

The eruption had two very different halves. First a column of gas and pumice rose about 25 km above the mountain and rained stone on the towns downwind. Then, the next morning, the column collapsed and avalanches of hot gas, ash and rock swept down the slopes. This article follows what happened as closely as the sources allow, explains why Pompeii and Herculaneum died in different ways, sets out the date debate, and shows where you can still see the evidence.

The short answer

• When: traditionally 24 August AD 79; the Osservatorio Vesuviano gives 24 October AD 79.
• How long: less than two days, according to Italy’s Civil Protection Department.
• What it destroyed: Pompeii, Herculaneum and Stabiae, and the wealthy villas around the bay.
• What killed people: falling pumice and collapsing roofs in the first phase; fast, extremely hot pyroclastic currents in the second.
• How big: about 4 cubic kilometres of ash and lapilli thrown into the atmosphere, in the Civil Protection Department’s figure. The observatory puts the magma erupted in the first, Plinian phase alone at more than 3 cubic kilometres.

A mountain nobody feared

In Roman times Vesuvius was not considered an active volcano. Its slopes were farmed and settled, and the shore of the bay was lined with towns and seaside villas. The Civil Protection Department notes that the eruption came after about three centuries of rest, long enough for the mountain’s nature to be forgotten.

There were warnings, but nobody read them as such. In AD 62 a strong earthquake struck the area. The observatory stresses that even then no one suspected the ground beneath them was volcanic. Pliny the Younger also recalls that for many days before the eruption there had been slight earthquakes, which alarmed nobody because they were common in Campania.

The eyewitness: Pliny the Younger’s two letters

Almost everything known about how people experienced the eruption comes from two letters written by Pliny the Younger to the historian Tacitus, numbered 6.16 and 6.20 in his collected letters. The observatory’s own account of the eruption begins with them, and volcanologists still call this kind of eruption “Plinian” after him.

Letter 6.16: the elder Pliny sails into the cloud

Pliny’s uncle, Pliny the Elder, a celebrated scholar and author, was at Misenum, the naval base in the Campi Flegrei across the bay from Vesuvius, in active command of the fleet. In the translated text of letter 6.16, it was on 24 August, about the seventh hour, that Pliny’s mother pointed out a cloud of unusual size and shape. From that distance no one could tell which mountain it came from. In shape, Pliny wrote, it was most like a pine tree: a tall trunk that spread out at the top into branches, sometimes white, sometimes dirty and blotched with the earth and ash it carried.

The elder Pliny ordered a ship prepared so that he could study it more closely. Then a written message arrived from Rectina, the wife of Tascus, whose villa lay beneath the mountain with no way out except by sea. The scholarly trip became a rescue. He launched warships, steered straight for the danger and dictated notes on the cloud as he went, while hot ash, pumice and blackened stones fell on the decks.

When the shore ahead was blocked by debris he turned for Stabiae, across the whole width of the bay, where his friend Pomponianus was waiting for the wind to change. That night he slept soundly, his nephew says, while ash and pumice piled up in the courtyard outside. By morning the buildings were rocking with repeated earthquakes. The party tied pillows to their heads against the falling stones and went down to the shore in darkness, but the sea was too rough to sail. Pliny the Elder collapsed there, apparently overcome by the fumes. His body was found two days later, untouched.

Letter 6.20: the view from Misenum

The second letter tells what happened at Misenum, where the younger Pliny, then in his eighteenth year, had stayed behind with his mother. After a night of violent shaking they left the town with a panicking crowd. They watched the sea draw back from the shore, then saw a black cloud, split by flashes like lightning, come down over the bay until it hid Capri and the headland of Misenum itself.

In the darkness that followed, people called out for parents, children and wives they could only recognise by their voices. Ash fell so thickly that the two had to keep standing up to shake it off. When daylight finally returned, the sun came out as blood-red as at sunset, and everything was covered in a deep layer of ash, like snow.

Phase one: the Plinian column

The observatory’s reconstruction, built from the layers the eruption left behind, fits Pliny’s description closely. In the early afternoon a series of explosions, caused by rising magma meeting shallow groundwater, blasted the conduit open. An eruption column rose to about 25 km above the volcano: the pine tree seen from Misenum.

What fell from it was mostly pumice, light and frothy volcanic stone, with finer ash. The wind carried it south-east, and the observatory shows these deposits reaching their greatest thickness around Pompeii and on the southern slopes of the volcano. During this Plinian phase more than 3 cubic kilometres of magma were erupted. The column stood until the early hours of the next morning, accompanied by frequent earthquakes: the shaking that both Plinys describe, at Stabiae and at Misenum.

For people in Pompeii this was the moment to decide whether to run or shelter. Many left; others stayed indoors as the pumice piled up against doors and on roofs.

Phase two: the column collapses

According to the observatory, many inhabitants went back overnight to the houses they had left unguarded. In the morning they were caught by the complete collapse of the eruption column. Instead of rising, the mixture of gas, ash and rock fell back and raced down the flanks as pyroclastic currents: turbulent clouds hundreds of degrees hot, moving far faster than anyone could run.

These currents spread almost all the way round the volcano and reached up to 15 km from the crater, destroying Herculaneum, Pompeii and Stabiae. The observatory links the dense dark cloud that Pliny the Younger watched from Cape Misenum on the morning of 25 October (on its dating) to this phase. More currents followed in the final stage, burying the surrounding towns for good, and an ash cloud spread as far as Cape Misenum.

Geologists divide the deposits into 8 eruptive units, from the first ash of the opening blasts to the last wet surges. Fine ash from the eruption has been traced as far away as Greece.

The eruption also reshaped the mountain. It tore away a large part of the old volcano, leaving a wide caldera whose centre almost coincides with today’s crater. The Civil Protection Department explains that the younger cone of Vesuvius, the one you climb on the crater path, grew inside the caldera of the older volcano, Monte Somma, after AD 79.

The eruption at a glance

Putting the observatory’s reconstruction and Pliny’s letters side by side gives this sequence:

• Early afternoon, day one: explosions open the vent and the column climbs to about 25 km. At Misenum, Pliny’s mother points out the strange cloud; his uncle sets sail.
• Afternoon and night: pumice falls on Pompeii and the southern slopes, roofs start to give way and earthquakes shake the bay. Pliny the Elder lands at Stabiae and sleeps there.
• The next morning: the column collapses and pyroclastic currents destroy Herculaneum, Pompeii and Stabiae. At Misenum the dark cloud comes down over the bay and the younger Pliny flees with his mother.
• The final stage: further currents bury the towns for good, and ash spreads as far as Cape Misenum.
• Afterwards: when daylight returns, Pliny the Elder’s body is found on the shore at Stabiae, and the survivors at Misenum find everything under a deep layer of ash.

Pompeii and Herculaneum: two ways to die

The two famous towns sat on different sides of the mountain, and the eruption reached them in different ways.

Pompeii: buried from above, then overrun

Pompeii lies about 10 km from Vesuvius, downwind of the column. The Pompeii archaeological park explains that in the first phase people who stayed were trapped in houses and shelters by the shower of pumice and lapilli, or killed when roofs and walls collapsed under debris that reached about three metres. Of these victims only bones have been found.

Afterwards a high-temperature pyroclastic flow hit the town at high speed, and anyone still there died at once. Ash hardened around their bodies, and when the bodies decomposed they left hollows. Since 1863, using a method perfected by the archaeologist Giuseppe Fiorelli, a little over a hundred plaster casts have been made from those hollows. In all, excavations have found the remains of over one thousand victims at Pompeii.

Herculaneum: overwhelmed by heat, then sealed in mud

Herculaneum stood on the coast at the western foot of the mountain. The Herculaneum park says the town was hit first by glowing clouds at about 400 degrees, travelling at over 80 km an hour, and then by mudflows that buried it under about 20 m of volcanic material. The result is a town preserved in a different way from Pompeii, with wood and even food surviving where at Pompeii they have long since rotted away.

Its most moving discovery was made on the ancient beach. In the 1980s excavators found the bodies of more than three hundred people who had fled to the shore and crowded into the arched chambers that opened onto the sand, hoping for rescue from the sea. Among them was a young pregnant woman close to giving birth. On 3 August 1982 the keel of an overturned boat began to emerge nearby. It was over 9 m long, and the park’s latest interpretation is that it may have been a military boat from the fleet commanded by Pliny the Elder, sent from Misenum to help. The skeleton of an officer, still wearing a belt with a sword and a dagger, lay close by.

Our article on Herculaneum covers what you can see there today, with tickets and opening hours.

24 August or 24 October? The date debate

The traditional date, 24–25 August AD 79, comes from the text of Pliny’s letter to Tacitus as it has come down to us. It is still widely used, and UNESCO’s description of the World Heritage site gives 24 August too.

For a long time, though, the date sat awkwardly with the evidence in the ground. Autumn fruit found at Pompeii did not fit high summer, and neither did the heavy tunics some of the inhabitants were wearing.

The decisive clue was presented at Pompeii on 16 October 2018. During new excavations in Regio V, archaeologists found a charcoal inscription on the wall of a room in a house that was being renovated. It is dated to the sixteenth day before the calends of November, which corresponds to 17 October. Charcoal is fragile and would not have lasted long on a wall, so the ministry’s announcement concludes that the inscription is most probably from October 79, a week before the eruption, which on this reading happened on 24 October.

In a news item published on 27 June 2022, the observatory reported a multidisciplinary review of the eruption that places it in the autumn of AD 79 rather than on 24 August, and notes that the inscription shows the eruption certainly happened after 17 October. The observatory’s own account of the eruption now uses 24 October.

What does that mean for you? Nothing changes about what you see at the sites; only the anniversary moves. Pliny’s letters remain the essential eyewitness account. It is the date in the surviving text, not his description, that the new evidence questions. This site follows the observatory and gives 24 October AD 79, while noting that the traditional date is still widely used.

Where to see the story today

The eruption is unusual among ancient disasters in that you can stand in almost every part of it: the towns it destroyed, the shore where people waited for boats, and the mountain itself.

• Pompeii. The casts are the most direct link to the people who died. The Garden of the Fugitives takes its name from the thirteen victims whose casts remain where the bodies were found. Walking the streets, you can see how much of the town survived under the pumice.
• Herculaneum. The beach chambers, the surviving woodwork and the depth at which the ancient town lies show what 20 m of volcanic material means. It is compact and easier to see in an afternoon than Pompeii.
• The crater. The rim you walk along belongs to the younger cone that grew after AD 79. From the top on a clear day you look out over the bay that Pliny’s ships crossed. The walk is by timed ticket only; our guide to crater tickets and the Gran Cono path explains how it works.

UNESCO describes the difference between the two towns neatly: the vast expanse of commercial Pompeii against the smaller but better-preserved remains of Herculaneum. If you can, see both.

Seeing the volcano and the ruins in one day

Because Pompeii and Herculaneum sit at the foot of the mountain, it is possible to see the crater and one or both towns in a single day. A day trip from Naples that combines the crater walk with Pompeii and an audio guide takes about 6 hours. A longer day from Naples that adds a walk around Herculaneum takes 7.5–8.5 hours and covers all three sites. Both are listed on the tours page.

Seeing the crater first and the ruins afterwards works especially well for this story: you look down on the landscape the eruption changed, then walk through what it buried. Our guide to Vesuvius and Pompeii in one day compares the tours with doing it yourself by train and bus.

Frequently asked questions

When did Vesuvius erupt?

In AD 79. The traditional date is 24 August, from the surviving text of Pliny the Younger’s letter. The Osservatorio Vesuviano now dates it to 24 October AD 79, supported by a charcoal inscription at Pompeii dated 17 October.

How long did the eruption last?

Less than two days, according to Italy’s Civil Protection Department. The Plinian column stood from the early afternoon into the next morning, when it collapsed into the pyroclastic currents that destroyed the towns; more currents followed in the final stage.

Did lava destroy Pompeii?

No. Pompeii was buried first by pumice and lapilli, which collapsed roofs and trapped people indoors, and then struck by a high-temperature pyroclastic flow. Herculaneum was hit by glowing clouds and then buried by mudflows.

How many people died?

The total is not known. Excavations at Pompeii have found the remains of over one thousand victims, and more than three hundred bodies were found on the ancient beach at Herculaneum. Stabiae and the villas around the bay were hit too.

Where did Pliny the Younger watch the eruption from?

From Misenum, the naval base in the Campi Flegrei across the bay, where his uncle commanded the fleet. His uncle sailed from there towards the volcano and on to Stabiae, where he died on the shore.

Could Vesuvius erupt like that again?

Vesuvius has not erupted since 1944 and is watched around the clock. The Civil Protection Department considers a Plinian eruption like AD 79 unlikely, because surveys have not found a shallow magma chamber large enough to feed one. Our article on whether Vesuvius is still active explains the monitoring and the emergency plan.