The Eruption Of Vesuvius Turned This Guy’s Brain Into Glass

“Our comprehensive chemical and physical characterization of the material sampled from the skull of a human body buried at Herculaneum by the 79 CE eruption of Mount Vesuvius shows compelling evidence that these are human brain remains, composed of organic glass formed at high temperatures, a process of preservation never previously documented for human or animal tissue, neither brain nor any other kind,” write the study authors. 

Located some 17 kilometers (10.6 miles) from Pompeii in the shadow of Vesuvius, the ancient Roman town of Herculaneum was completely annihilated in the wake of the eruption, with many of its inhabitants remaining entombed in a blanket of ash for almost two millennia.

Deposited by scorching pyroclastic flows, this volcanic material would likely have cooled very slowly, making vitrification – the process by which glass forms – impossible. Indeed, glass can only occur when a liquid cools quickly enough to avoid being crystalized as it solidifies.

It’s this principle that forms the basis of cryopreservation, whereby bodies and organs are rapidly cooled to around -120°C (-184°F) using liquid nitrogen, thus converting them to glass while retaining the molecular structure of soft tissues. When thawed, these vitrified components return to their original state.

In nature, however, the conditions required to vitrify organic matter and preserve it as glass simply don’t occur, which is why nothing like this has ever been seen before. Researchers were therefore stunned to find a glassy material with a “black and shiny, obsidian-like appearance” inside the skull of a corpse at Herculaneum.

We don’t know whether he was drunk, whether he was dead, whether he just didn’t care, but he was lying in bed in a house in the city center.

Dr Guido Giordano

Discovered lying in his bed, the young man of about 20 years of age is thought to have been the guardian of the Collegium Augustalium, a public building dedicated to the worship of Emperor Augustus. Scans revealed that the glass-like material contained “exceptionally well-preserved complex networks of neurons, axons, and other neural structures,” yet the unequivocal identification of organic glass had not yet been confirmed.

During a series of thermal experiments, the authors of the new study were able to verify that the substance is indeed natural glass, indicating that the eruption produced the necessary conditions to vitrify the victim’s brain. However, while the pyroclastic flows that occurred during the event are estimated to have reached a temperature of 465°C (869°F), tests revealed that vitrification could only be achieved if the brain tissue was heated to more than 510°C (950°F) before immediately cooling to ambient temperatures.

The study authors therefore deduce that the eruption must have begun with a short-lived hot ash cloud that instantly killed all those in its wake. Reaching temperatures exceeding 510°C, this lethal waft would then have vanished as quickly as it appeared, causing temperatures to instantly return to baseline before the waves of pyroclastic flows began.

“The brain then turned into glass during the fast cooling at glass transition temperature close to 510°C,” write the researchers. 

“Later, in agreement with witness accounts and deposit stratigraphy, Herculaneum was progressively buried by thick pyroclastic flow deposits, but at lower temperatures, so that the unique presence of a vitrified brain could have been preserved until today,” they add.

Speaking to IFLScience, study author Dr Guido Giordano explained that this incredible heat would have destroyed the soft tissue of most of the victims, but that the specific conditions in this young man’s bedroom may have allowed fragments of his brain to survive the initial wave before turning to glass during the cooling phase. 

“Most of the victims were actually found in the harbor, because they rightly got scared and escaped. They went waiting for rescue from the sea,” he said. “But this person, for some reason, did not. We don’t know whether he was drunk, whether he was dead, whether he just didn’t care, but he was lying in bed in a house in the city center.”

“And the outcome of the evidence is that the specific location where the person was staying compared to the others probably allowed, for some reason, the survival of some organic material through the heat wave. So instead of having just bones, we had still bits and pieces of this brain,” says Giordano.

Furthermore, the fact that the initial ash cloud reached a temperature conducive to vitrification helps to fill in the gaps in our knowledge of how things unfolded as the eruption progressed. Specifically, this finding reveals that it was indeed this early blast of heat that provided the lethal blow to the residents of Pompeii and Herculaneum, leading Giordano to confirm that “they were already dead by the time they were buried.”

The study is published in the journal Scientific Reports.