The eruption of Vesuvius in 79 AD lasted approximately eighteen hours. It began in the early afternoon of one day and ended around dawn of the next. It buried two Roman towns — Pompeii under approximately twenty feet of pumice and ash, and Herculaneum under approximately seventy feet of pyroclastic flow material — and killed an unknown but substantial fraction of the populations of both. It produced the most thoroughly documented eyewitness account of any volcanic eruption in classical antiquity, in the form of two letters written approximately twenty-five years later by the Roman administrator Pliny the Younger, who watched the eruption from across the bay at Misenum. It produced the most thoroughly excavated catastrophic event in the human archaeological record. And it killed the elder Pliny — the senior naval commander at the Bay of Naples, the author of the Natural History, and the younger Pliny’s uncle — at the small town of Stabiae on the second day of the eruption, while attempting a naval rescue.
The traditional date of 24 August 79 AD, derived from the standard manuscript tradition of Pliny the Younger’s letters to Tacitus, has been substantially revised in recent decades. A growing body of archaeological evidence — the autumn-harvest material in Pompeian shops, the woolen cloaks on victim bodies, the discovery in 2018 of a charcoal inscription dated “the 16th day before the Calends of November” (17 October) in House V.6 — points to an autumn rather than late-summer date. The current scholarly consensus places the eruption at approximately 24 October 79 AD. The corruption in the Pliny manuscript tradition apparently substituted Augustus for Novembres.
What was there before
Pompeii in 79 AD was a Roman provincial town of approximately 11,000 to 12,000 people, sitting on a low hill at the southern end of the Bay of Naples, about five miles south of Vesuvius. It had been a Roman colony since 80 BC. Its economy was based on wine, olive oil, fish processing, and textile manufacturing. It had a forum, a theater, two amphitheaters (one of them the oldest stone amphitheater in the Roman world), public baths, several large temples, and approximately 1,500 surviving inscribed wall texts in the buried excavation. It was a moderately prosperous middle-class Roman town with no particular distinction.
It had also, seventeen years earlier in 62 AD, suffered a major earthquake. The 62 AD earthquake had destroyed approximately half the buildings in Pompeii and Herculaneum and most of the public buildings in both towns. Reconstruction work was still proceeding in 79 AD; many private houses still had unrepaired earthquake damage from the previous quake-cycle. Vesuvius itself had been continuously dormant since around 1200 BC, almost 1,300 years before, and was not understood as a volcano at all in 79 AD. Its slopes were planted with vines. Its summit was wooded. The Roman geographer Strabo, writing around 25 AD, had noticed that the mountain had a flat top that looked geologically anomalous and had speculated that it was an extinct volcano. Strabo’s speculation was not widely repeated.
Herculaneum was smaller — approximately 5,000 people — but wealthier than Pompeii. It sat directly on the coast at the western foot of Vesuvius. It was an unfortified resort town with substantial seaside villas, including the famous Villa of the Papyri, which would later be the source of the only surviving major classical library buried at the eruption. The papyrus scrolls of the villa were carbonized in the pyroclastic flow but preserved in a recoverable state.
The eruption sequence
The eruption began with a vertical Plinian column rising above the summit of Vesuvius at approximately 1 PM on 24 October. The column reached a height of approximately twenty miles within the first hour. It was so visible from across the bay that Pliny the Younger’s uncle, the elder Pliny, at the naval base at Misenum thirty miles to the west, ordered a galley to investigate.
The Plinian column produced a continuous fall of pumice and ash on the towns directly downwind of the summit. Pompeii, southeast of Vesuvius, was directly in the fallout zone. The rate of pumice accumulation on Pompeian rooftops reached approximately six inches per hour through the afternoon and evening of 24 October. The total pumice load on Pompeian roofs reached approximately five feet by midnight. Many roofs collapsed under the load through the night. Most of the deaths at Pompeii that occurred during this first phase of the eruption were the result of roof collapse on people sheltering inside their houses.
The Pompeian population had several hours in which to leave the city, and most of it did. The current archaeological consensus is that the bulk of Pompeii’s population evacuated successfully during the first afternoon, traveling east or south away from the fallout zone. The skeletons recovered from the city — approximately 2,000 in the excavated areas — represent a minority of the original population, those who either chose to remain (to guard property, to look after the elderly or sick, to wait out what they expected would be a brief event) or who could not leave.
Herculaneum, much closer to the volcano but upwind of the falling pumice column, was spared the first-phase fallout entirely. Its population also evacuated, but mostly toward the seaside boathouses on the assumption that boats would come to take them off. The boathouses, which have been excavated since 1982, contain approximately 300 skeletons — the largest single concentration of victim remains anywhere in the eruption deposits.
The eruption mode changed around midnight or shortly after. The vertical column became increasingly unstable and began to collapse periodically, producing pyroclastic density currents — ground-hugging clouds of superheated gas, ash, and pumice fragments moving at approximately 60 miles per hour at temperatures of approximately 400–700 degrees Celsius. The first major pyroclastic current ran down the western flank of the volcano around 1 AM on 25 October and hit Herculaneum at approximately 400°C. The people in the boathouses died instantly. The current then continued through the upper town and buried the city under a deposit that hardened, on cooling, into compact ash 50 to 80 feet thick.
A second and larger pyroclastic surge developed around 7 AM on 25 October and ran south. It overtopped the southern flank of Vesuvius, ran across the surviving pumice deposit at Pompeii, and killed everyone remaining in the city. The current that reached Pompeii was traveling at approximately 100 miles per hour and was approximately 250°C at ground level. The Pompeians who died in this final phase were killed by heat shock — their internal organs and brain tissue cooked within seconds; their bodies were fixed in attitudes of last activity. The famous body-casts of Pompeii, produced by Giuseppe Fiorelli’s 1860s plaster-injection technique, show the postures of people surprised mid-activity by the surge: a woman shielding a child, a man covering his face, several pairs of bodies in mutual embrace, household pets struggling against their chains.
The eruption ended in the morning of 25 October. Total ejecta has been estimated at approximately 4 cubic kilometers. The Bay of Naples and the inland river valleys were buried under varying thicknesses of pumice and ash. The towns of Pompeii, Herculaneum, Stabiae, and Oplontis were buried beyond recovery.
The death of Pliny the Elder
Pliny the Elder commanded the Roman naval base at Misenum on the western horn of the Bay of Naples. When the Plinian column appeared above Vesuvius on the afternoon of 24 October, his first reaction (described by his nephew) was to order a single small galley prepared so that he could sail closer to observe the eruption and write up his observations for inclusion in a future edition of the Natural History. He was 55 years old, asthmatic, overweight, and recognized as the leading scientific writer of his generation.
Before he had launched, he received a courier message from his friend Rectina, who lived at a villa at the eastern foot of Vesuvius. The villa was in the fallout zone. Rectina asked to be evacuated by sea. Pliny ordered the entire Misenum fleet to put to sea on a rescue mission. He went himself in the lead galley.
The fleet sailed across the bay through the afternoon. As they approached the affected coast, falling pumice and ash made the sea increasingly difficult to navigate; the floating pumice mass on the water surface near Herculaneum was impassable. Pliny ordered the fleet to divert to Stabiae, the town at the southern end of the bay where his friend Pomponianus lived. They landed at Stabiae in the early evening.
Pliny spent the evening at Pomponianus’s villa attempting to reassure the local population and the household. He ate dinner. He slept. The household was woken in the night by the deepening pumice fall and the periodic earthquakes that accompanied the eruption. They debated whether to remain in the houses (collapse risk) or to move onto the open beach (asphyxiation risk). Pliny led the group to the beach. He had asked for a sheet to be laid down for him on the sand; he was breathing with increasing difficulty as the air became increasingly loaded with sulfurous and ash particulates.
The second pyroclastic surge, the one that destroyed Pompeii in the early morning of 25 October, reached Stabiae as a hot ash cloud at relatively low temperature (perhaps 100–200°C, by modern reconstruction). Pliny, asthmatic and obese, asked his attendants to support him to his feet. He stood. He collapsed almost immediately and could not be revived. The household survived. Pliny’s body was recovered three days later, when the surviving party returned to Stabiae after the eruption ended. He was buried at Misenum. The exact cause of his death was probably acute respiratory failure under conditions of high heat and high ash concentration — a heart attack precipitated by asphyxiation.
His nephew, who was seventeen, had stayed at Misenum throughout. He survived the eruption, inherited his uncle’s library and Roman senatorial career, and produced approximately twenty-five years later the two letters to Tacitus that remain the primary documentary source for the eruption.
Rediscovery and the modern excavations
The buried towns were forgotten almost completely for sixteen centuries. The local landowners after the Lombard period knew of “Civita” — the rough Italian name for the unidentifiable buried Pompeian ruins — but did not excavate. A Spanish military engineer, Alcubierre, began the first official excavations in 1748 in search of statues for the Bourbon kings of Naples. The 18th-century excavations were tunnel-and-extract operations focused on portable art and would now be classified as systematic looting; substantial damage was done to wall paintings and architectural detail.
The modern excavation method dates from Giuseppe Fiorelli’s appointment as director of the Pompeii excavations in 1863. Fiorelli introduced the systematic stratigraphic excavation methodology, the conservation-rather-than-extraction principle, the numbering and recording of every find by exact location, and — most famously — the plaster-injection technique for recovering the form of organic material decayed in cavities within the ash deposit. The Pompeian body-casts were the first systematic Fiorelli applications; the technique has since been used to recover the forms of wooden doors, shutters, root systems, and chained animals throughout the site.
The Pompeian excavations have continued continuously since 1863. Approximately two-thirds of the ancient city has now been excavated. The other third remains under the ash deposit and modern olive groves on the eastern side of the site. Excavations have been suspended at the edge between excavated and unexcavated zones since approximately 1980 in order to preserve material for future archaeological generations with better techniques. New work in the western and northern zones of the city has produced almost continuous discoveries since approximately 2018, including the dated charcoal inscription of October 79 that allowed the eruption date to be revised.
The site remains the most important archaeological evidence of normal Roman urban life — the only surviving Roman town in which the population was killed mid-activity by an event that preserved their material world almost completely.
Vesuvius has remained active. It erupted in 1631 (approximately 4,000 deaths in the modern Neapolitan suburbs), in 1872, in 1906, and most recently in March 1944, when an eruption during the Allied occupation destroyed the village of San Sebastiano and damaged dozens of B-25 bombers parked at the nearby Pompeii airfield. The volcano has been dormant since 1944. The modern population at risk of a recurrence — the entire Neapolitan urban area — exceeds 3 million people. The Italian government’s evacuation plan, the Piano Nazionale di Emergenza Vesuvio, requires three days of advance notice.