Pompeii and Herculaneum: what the eruption of AD 79 preserved

The short answer

One eruption, two kinds of burial. Vesuvius buried both towns in AD 79, as UNESCO's inscription of the two sites records.[7] XTOUR's reading of the two parks' accounts is that the difference in what survived comes from how each town was buried.

At Pompeii, ash and pumice and then a cloud of hot volcanic material left empty spaces where bodies had been, which archaeologists learned to fill with plaster.[1] At Herculaneum, a far deeper mass of hot volcanic material sealed the town so completely that wood turned to charcoal instead of burning.[4]

Pompeii: ash, pumice and a hot cloud

The Herculaneum park's account of the eruption says a column of volcanic material rose 14 kilometres and released lapilli and pumice that the wind deposited on Pompeii and the neighbouring towns.[2] The Archaeological Park of Pompeii says the eruption buried the city beneath metres of ash and pumice, and that people trapped beneath the ash were rapidly covered by a cloud of hot volcanic material which solidified around their bodies. Its new exhibition includes a video reconstructing what the park describes as "a column of about 4 metres of ash and lapilli", the volcanic material that completely buried the city.[1] In XTOUR's reading, that is a measure of what fell on Pompeii, not the 14-kilometre column that rose from the volcano.

The plaster casts

The casts exist because of that hardened material. According to the park, the bodies and other organic materials decomposed over time and left voids in the hardened ash. In 1863 the archaeologist Giuseppe Fiorelli became the first to succeed in pouring liquid plaster into such cavities, producing figures that often still have their bones inside. The park says about a hundred casts have been made at Pompeii since the nineteenth century, and that some remain in the houses and buildings where they were found.[1]

The park says a permanent exhibition in the Palestra Grande, open from 12 March 2026, shows 22 casts of victims, along with two casts of doors.[1]

Herculaneum: twenty metres of hot material

The Archaeological Park of Herculaneum says the town was first hit by fiery clouds of around 400 degrees Celsius and then by mudslides that buried it under about twenty metres of volcanic material.[2] Tools, architectural elements and wooden furniture were carbonised, and the park calls Herculaneum the only city in the Roman world that preserves wood as a building material and in its furnishings.[3] Its exhibition on the site's wood explains why: the twenty-metre mass of superheated pyroclastic mud created an environment so short of oxygen that the wood carbonised instead of combusting.[4]

A study published in Scientific Reports in 2023 used charred wood from the site to estimate temperatures. It found that the first current to enter the town was a short-lived ash-cloud surge at about 555 to 495 degrees Celsius, and that the currents which went on to bury the town were mostly denser and cooler. That is higher than the park's "around 400" figure for the first clouds; the two are different estimates, and neither is a settled figure.[2][6]

Why the two sites look different today

XTOUR's reading of these sources is that the burials explain the different kinds of survival. At Pompeii, the voids left in hardened ash are what made the casts possible. Herculaneum was sealed under about twenty metres of material poor enough in oxygen to turn its wood to charcoal rather than ash, which is why the park can describe its town as unique for preserved wood.[3][4]

Herculaneum's deep burial also shaped its excavation. The park says the first systematic explorations began in 1738, under Charles of Bourbon, through shafts and tunnels dug down through about twenty metres of volcanic subsoil, and that the hardness of the volcanic mud led to the work being abandoned after a few decades. New excavations began only in 1927, under Amedeo Maiuri.[5]

What XTOUR does not tell you

This is an explainer about the past, not a visiting guide. XTOUR does not publish opening hours, prices or access rules for either park; the Pompeii, Herculaneum and Vesuvius comparison says who runs each site and where their rules are published. Figures such as burial depths, temperatures and numbers of casts are attributed to the park or study that gives them.