Mental Floss

A Vesuvius Victim’s Brain Turned into Glass, and Scientists Think They Know How

The Herculaneum resident, killed by the volcanic eruption in 79 CE, presents the only known vitrified brain on Earth. Now, researchers have a theory for how it happened.
ByNick Keppler|
A fragment of the organic glass found inside the skull of the deceased individual in Herculaneum.
A fragment of the organic glass found inside the skull of the deceased individual in Herculaneum. | Pier Paolo Petrone

The 79 CE eruption of Mount Vesuvius obliterated the Roman cities of Pompeii and Herculaneum with a blast that had the thermal energy of 100,000 World War II-era atomic bombs. About 1950 years later, archaeologists uncovered the remains of one resident whose brain had turned into organic glass in his skull, preserving the organ’s microstructures.

The 2020 discovery baffled scientists. Sure, the blast was hot, but modern measurement tools show that the pyroclastic flow from Mount Vesuvius did not reach the threshold of 510°C (910°F) that would have been needed to transform brain tissue to glass. The process of making glass also requires a torching and then a quick drop in temperature to prevent crystallization. Volcanic ash does not cool so quickly. So, how did this victim’s brain get turned into something akin to a dropped Champagne flute?

The remains of the deceased individual in situ in their bed in the Collegium Augustalium, Herculaneum.
The remains of the deceased individual in situ in their bed in the Collegium Augustalium, Herculaneum. | Pier Paolo Petrone

A new paper published in the journal Scientific Reports presents a theory [PDF]. Guido Giordano, a volcanic geologist at Roma Tre University in Rome, and his colleagues propose that a super-heated ash cloud might have been the first wave of destruction from the eruption. The phenomenon has been observed in recent volcanic blasts. It could have hit quickly and then dissipated, creating the necessary high temperatures and cooldown. 

The hard skull and spine of the man—whose remains archeologists found still in his bed in the town of Herculaneum—likely protected the brain from complete thermal breakdown, allowing fragments to form into organic glass. 

The archaeological site of Herculaneum with Mount Vesuvius visible in the background.
The archaeological site of Herculaneum with Mount Vesuvius visible in the background. | Pier Paolo Petrone

It would have been a completely unique set of circumstances. Organic glass is rare in nature, and the paper notes that this is “the only such occurrence on Earth” of a brain becoming vitrified.

The volcanic ash that buried Pompeii and the vicinity before some of the denizens could even react created an atmosphere devoid of air and moisture, preserving the area for archeologists. Major excavations began in the mid-18th century. A recent spate of small, targeted digs has unearthed horses in their stables, an ornate snack bar, and the remains of one poor guy who was crushed by a boulder as he fled the destruction.

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