While most of us associate the eruption of Mount Vesuvius in AD 79 with Pompeii, a new study has revealed the devastating impact the event had on inhabitants of another nearby settlement, called Herculaneum.
Researchers have found evidence that ‘pyroclastic currents’ – hot and fast-moving flows of gas and volcanic particles – hit the small Roman town.
The first to hit, estimated to be 1,022°F (550°C), vaporised inhabitants within minutes, while a succession of smaller currents at lower temperatures (up to 870°F or 465°C) buried the town under 65-foot-thick volcanic deposits.
While most bodies at Herculaneum were swiftly reduced to piles of ash, scientists have previously found human tissue that was transformed to glass by the event.
One man’s brain had been burned at a very high temperature, before quickly cooling, turning it into a form of glass – a process known as vitrification.
Pictured are the remains of Herculaneum, a Roman town that was buried under volcanic ash and pumice in the Eruption of Mount Vesuvius in 79 AD
Map shows Herculaneum and other cities affected by the eruption. The black cloud represents the general distribution of ash and cinder. Herculaneum was destroyed – together with Pompeii, Torre Annunziata and Stabiae – by the eruption
The new study was led by a team of geologists from the University of Roma Tre and published in the journal Scientific Reports.
‘Despite the 79CE being one of the most studied eruptions, the exact timing, and the causes of death at Pompeii and Herculaneum are still debated,’ they say in their paper.
‘We show that the first PDC [pyroclastic current] which entered the town was a short-lived ash cloud surge, with temperatures of 555-495°C, capable of causing instant death of people.’
The eruption of Mount Vesuvius in 79 AD destroyed the settlements of Pompeii, Herculaneum, Torre Annunziata and Stabiae, killing thousands in the process, said to be up to 16,000.
After the eruption, bodies of the victims at Pompeii were famously preserved in a protective shell of ash before they eventually decayed.
Since the mid 1800s, the voids that these bodies left behind were eventually filled with plaster casts to recreate their final moments.
In comparison, the bodies of people living in Herculaneum were not well preserved after they were killed – and the researchers wanted to establish why that was.
They collected carbonised wood samples from five sites in Herculaneum and studied them using reflectance analysis, which estimates intensity of energy absorption.
Illustration of the first pyroclastic density current (PDC) to hit Herculaneum, estimated to be 1,022°F (550°C)
The samples showed signs of being subjected to a very hot gas for a very short period of time – evidence of exposure to a pyroclastic current.
The first that entered Herculaneum had a temperature of at least 1,022°F (550°C), although it likely exceeded this figure, according to the team.
This was followed by at least two cooler currents with temperatures somewhere between 600°F and 870°F (315°C and 465°C) that left thicker volcanic deposits on the ground.
These findings allowed the team to understand the conditions for the formation and preservation of the vitrified brain of a victim’s skull in the Collegium Augustalium, reported back in 2020.
The man is thought to have been a caretaker at the headquarters of the Collegium Augustalium, a building owned by an imperial cult that worshipped the former emperor Augustus.
His brain had been burned at a very high temperature before quickly cooling, turning it to a shiny and solid black glass-like material, but this was a unique case, as the vast majority of victims at Herculaneum would have been instantly vaporised.
The experts say in their paper that the ‘transformation into glass of fresh cerebral tissue in a hot environment is only possible if two conditions are met’.
‘[These are if] the heating event is short-lived, so that the tissue is not fully vaporised, and once the diluted current has vanished, the body is not fully entombed in a hot deposit, a necessary condition to allow the very rapid cooling required to attain vitrification,’ they say.
The team also point out that at Pompeii, many bodies showed a typical post-mortem stance known as pugilistic attitude or ‘boxer position’, with flexed elbows and knees as well as clenched fists.
Bodies subjected to high temperatures often end up in this position as their tissues and muscles dehydrate and contract.
Images mark the Herculaneum archaeological site location and the ancient Herculaneum city map with the five sampling sites (b) and (c). Also show is ash cloud surge deposits on few centimeters of black beach sand from the eruption (d)
After the eruption, bodies of the victims at Pompeii were famously preserved in a protective shell of ash before they eventually decayed. Since the mid 1800s, the voids that these bodies left behind were eventually filled with plaster casts to recreate their final moments (pictured)
But this does not occur if temperatures are high enough to rapidly vaporise this flesh off of the bone, as seen in Herculaneum.
‘The lack of such corpse attitude at Herculaneum testifies to the rapid disappearance of soft tissue, as the pugilistic stance is due to dehydration and shortening of muscles induced by intense heat,’ the experts say.
The team suggests their findings should serve as a warning for modern citizens of Naples – a city that is close enough to feel the effects of a pyroclastic current should Vesuvius erupt again.
‘Such hazard deserves greater consideration at Vesuvius and elsewhere, especially the underestimated hazard associated with hot detached ash cloud surges, which, though short lived, may expose buildings to severe heat damages and people to death,’ they warn.
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