The missing bodies of the ancient Roman city were vaporized in a volcanic explosion: ScienceAlert
When Mount Vesuvius erupted nearly 2,000 years ago, the Roman city of Pompeii and its inhabitants were buried alive, buried in ash. But the nearby town of Herculaneum was wiped out and few traces of its inhabitants have been found.
Their bodies were most likely vaporized in a searing blast of gas and particles, according to new research by geologists from Roma Tre University and Federico II University of Naples in Italy, who found new evidence of the fatal event in charred wood.
In 2018, archaeologists discovered the first convincing evidence that some inhabitants of Herculaneum met horrific deaths: their soft tissues and blood boiled in a flash when struck by the extreme heat of the volcanic eruption; their skulls exploded from within.
Two years later, in 2020, archaeologists describes another skull discovered on the site. It contained fragments of a glassy material that led them to believe that the person’s brain had been vitrified or turned into glass.
Not everyone was convinced, however, that the citizens of Herculaneum died this way. Searing temperatures of around 500°C (900°F) could have produced the horrific effects archaeologists have observed: vitrified brains, cracked teeth, contracted limbs, charred bones and ruptured skulls. But other evidence of soft tissue preserved on a few ribs indicated lower temperatures.
Geologist Alessandra Pensa from the University of Roma Tre and her colleagues therefore set out to reconstruct the extreme temperatures that hit the citizens of Herculaneum when Mount Vesuvius exploded in 79 CE.
They analyzed the amount of light reflected in 40 samples of charred wood excavated in the 1960s from five different sites across the ancient city, with the reflectance of the samples indicating the temperature at which the charcoal formed.
“Charcoal was found to be the only proxy capable of recording multiple short-lived extreme thermal events, revealing for the first time the true thermal impact of the 79 CE eruption,” the researchers said. to write.
This ‘geothermometer’ suggests that temperatures initially exceeded 500°C and may have reached as high as 555°C when the eruption’s first short-lived ash cloud passed through Herculaneum – which is located at the foot of Vesuvius, more nearer than Pompeii.
These temperatures would have been “capable of causing the instantaneous death of people, while leaving only a few decimeters of ash on the ground”, according to the researchers. to write.
Interestingly, the highest temperature signals were detected in wood samples from the northern part of the city, at the Collegium Augustalium, where the vitrified brain was found.
The cooler temperatures previously detected on the coastline southwest of the city could be explained by interactions between seawater and the ash cloud when the plume first reached the coast, the researchers suggest.
Later heat waves from the eruption carried more ash and debris to slightly cooler temperatures, between 390°C and 465°C, and 315°C to 350°C.
The technical name of these successive flows is diluted pyroclastic density currents – very turbulent and unpredictable currents, close to the ground, which move at speeds of several hundred meters per second. PDCs have been linked to some of the deadliest volcanic disasters, including the Eruption of Mount Pelee in 1902which killed nearly 30,000 people almost instantly.
Witnesses to the eruption of Mount Vesuvius in Herculaneum actually described seeing clouds “moving like streams over the ground”.
As the researchers note, it is not just the extremely high temperatures of diluted PDCs that can be fatal, but the combination of dynamic pressure, acid gases and suffocation from ash inhalation.
Although little of Herculaneum remains today, the city’s dramatic end serves as a warning of Vesuvius’ bubbling potential to erupt again.
The researchers suggest that buildings in Mount Vesuvius’ ‘red zone’ – where around 700,000 people live – should be reinforced to shelter residents from the thermal impacts of any potential future eruption, if they cannot evacuate in time.
“The documented deadly impact for dilute pyroclastic density currents produced during ancient and recent volcanic eruptions suggests that such a hazard deserves greater consideration at Vesuvius and elsewhere,” the researchers said. to write.
In the case of another short-lived ash cloud, “survivability potential critically depends on the ability of shelters to prevent infiltration of hot, dusty gas,” they said. conclude.
The research has been published in Scientific reports.