Evrim Yazgin
Cosmos science journalist
Archaeologists have determined that an individual’s skull was turned to glass during the eruption of Mount Vesuvius in 79 CE which led to the destruction of ancient Roman town Pompeii.
The individual lived in Herculaneum – a town on the Italian west coast near Naples, even closer to the eruption than Pompei.
Analysis published in Scientific Reports suggests that the person’s skull was transformed into a unique, dark-coloured organic glass when they were killed by a very hot, sudden ash cloud. It’s believed the glass comprises the fossilised brain of the individual.
Glass requires specific conditions to form – a substance’s liquid form must cool fast enough not to crystalise when becoming solid. This means it must become a solid at a temperature much higher than its surroundings.
Naturally occurring glass is rare. In 2020, archaeologists believed they found the only example of glass formed naturally from heated organic matter at Herculaneum.
An interdisciplinary team subjected the glass to calorimetric analysis to test this theory. The analysis sought to determine the thermal properties of the material.
X-rays and electron microscopy indicated that the individual’s skull would have to have been heated to 510°C before cooling rapidly to be turned into glass.
This could not have happened if the individual was heated solely by pyroclastic flows – high-speed currents of gas and other volcanic matter. The temperature of these flows from Vesuvius would not have reached higher than 465°C and would have cooled too slowly.
Instead, a super-heated ash cloud must have preceded the pyroclastic flows and caused the brain to turn to glass. Such ash clouds have been observed in modern volcanic eruptions.
“The glass that formed as a result of such a unique process attained a perfect state of preservation of the brain and its microstructures,” the authors say.
