How could volcano eruption cause victim’s brain to turn into glass?

In 79 CE, Mount Vesuvius erupted catastrophically, obliterating the Roman cities of Pompeii and Herculaneum and claiming thousands of lives.

Among the victims was a young man in his early twenties, discovered in bed inside a structure known as the Collegium Augustalium. When scientists unearthed his remains in the 1960s, they encountered a puzzling find—his skull contained fragments resembling black, glass-like material. While many hypothetical suggestions were made over the years, a recent study published in Scientific Reports provides new insights into this extraordinary occurrence. According to an article by Archaeology News, scientists suggest that his brain underwent vitrification, a process in which organic matter transforms into glass.

For years, experts have debated the nature of this glassy substance, unsure if it was preserved brain tissue or something else. Many doubted that the pyroclastic flows—rapid, scorching currents of gas and volcanic debris—that engulfed Herculaneum reached temperatures high enough to vitrify human tissue. 

However, new research presents a different perspective. Geologist and volcanologist Guido Giordano of Roma Tre University led a study proposing that, prior to the pyroclastic flows, a superheated ash cloud—reaching at least 510°C (950°F)—swept through the city. The extreme heat would have caused the brain to liquefy, followed by an abrupt cooling period that resulted in its transformation into glass. To support their theory, the researchers analyzed nearby charcoal fragments, which displayed evidence of exposure to extreme heat followed by rapid cooling. They also examined data from more recent volcanic eruptions, such as Mount Unzen in Japan (1991) and the Fuego volcano in Guatemala (2018), both of which produced similarly intense ash clouds. 

Using advanced imaging techniques, including electron microscopy, the team closely studied the glassy fragments. Their findings revealed structures resembling nerve cells, strongly indicating that the material was indeed preserved brain tissue. “The glass formed as a result of this process allowed for the integral preservation of biological brain material and its microstructures,” explained forensic anthropologist Pier Paolo Petrone of Università di Napoli Federico II, a lead researcher in the study. This case represents the first known instance of human brain vitrification occurring naturally. 

Scientists have long understood that for glass to form, very specific conditions must be met—an extreme temperature increase followed by rapid cooling, preventing crystallization. While archaeologists have occasionally discovered vitrified wood at sites in Pompeii and Herculaneum, no known human or animal remains have ever undergone this transformation. The study also addresses why only the brain was preserved in this manner. The intense heat destroyed other soft tissues and bones, but the skull may have provided enough insulation to allow the brain to remain intact until the sudden cooling process took effect. New theory faces challenges Despite these compelling findings, some researchers remain skeptical. 

Alexandra Morton-Hayward, a molecular archaeologist at Oxford University, had previously questioned whether the glassy material was truly brain tissue. In a 2020 paper published in Science & Technology of Archaeological Research, she and her team argued that the pyroclastic flows in Herculaneum were unlikely to have reached the necessary temperatures or cooled quickly enough to induce vitrification. They also pointed out that independent researchers had not been able to obtain samples for further verification. The debate surrounding the “glass brain” is far from settled, and as scientific techniques continue to evolve, future studies may uncover additional instances of this rare phenomenon. 

By Nazrin Sadigova