The volcanic eruption that wiped out the Roman town of Pompeii created a stream of hot gas with a temperature of 550 degrees Celsius, high enough to turn a human brain into glass.
This brief burst of heat caused the nearby town of Herculaneum to experience temperatures of up to 550 degrees Celsius, causing instant death, according to new research published April 6 in the journal Scientific Reports . The team from Roma Tre University analyzed carbonized wood from multiple sites in Herculaneum, which is closer to Vesuvius volcano than Pompeii, to reconstruct the thermal fluctuating events that took place after the 79 eruption. Because of the charred remains of the specimen, they could speculate that the town was initially covered by a stream of hot air known as a dilute pyroclastic flow (PDC) .
Vitrified human brain fragment in a man’s skull in Herculaneum. (Photo: Pier Paolo Petrone).
The researchers explain that the first PDC spilled over Herculaneum with a temperature of more than 550 degrees Celsius, reflected in specimens collected on the main streets of Collegium Augustalium and Decumanus Maximus. This initial event was followed by a stream of debris that buried the town under a 20-meter thick layer of volcanic ash, which had a lower temperature.
Due to the flashy nature and extreme heat associated with the initial outburst, the entire event left only a few dozen centimeters of ash on the ground, which helps explain why it has never been detected before. . However, the destructive power of dilute PDCs can be observed in more recent volcanic eruptions such as at Martinique in May 1902, when nearly 30,000 people died instantly from this gaseous outflow.
Although direct evidence of dilute PDC in Herculaneum has never been recorded, the study authors say there are many clues in the remains of victims. For example, many bodies in Pompeii are immobile in a postmortem flexion known as pugilistic attitude , victims at Herculaneum do not have such a position because their soft tissues are destroyed by intense heat.
The discovery of a vitrified intact brain inside the skull of a resident of the Collegium Augustalium provides more definitive hints. According to the team, the brain can only turn glass if the heat event is so brief that the tissue doesn’t completely evaporate. The preservation of the cerebellum depends on whether the subsequent stream of debris is cool enough for the ashes to accumulate.
After reconstructing the sequence of events that followed the eruption, the researchers say the findings have implications for residents living in nearby Naples if Vesuvius becomes active again. If a dilute PDC forms, the survival of the population depends on the shelter’s ability to block out the heat. This allows those who do not evacuate early to save their lives and wait for rescue.