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A glass-like substance found in the skull of a person who perished in the volcanic eruption of Mount Vesuvius has helped archaeologists unravel the sequence of events that wiped out Pompeii and Herculaneum in 79AD.
The study, published on Thursday in Scientific Reports, assessed the mysterious substance bearing similarities to glass and found that it comprised the individual’s brain.
Researchers suspect the person’s brain likely underwent “fast heating” followed by “very fast cooling” to turn into glass.
Glass rarely occurs naturally as it needs a liquid to cool rapidly and not crystallise when turning solid.
For glass formation, the substance must become solid at a temperature well above its surroundings.
It is thus extremely rare for an organic substance to take a glass-like form as ambient temperatures are rarely low enough for water – a key component of organic matter – to solidify.
This is why the formation of glass in nature is mostly restricted to comet strikes on sandy landscapes.
The only piece of suspected naturally occurring organic glass was found in Herculaneum, Italy, in 2020, but it was unclear how the material had formed.
“Here we demonstrate that material with glassy appearance found within the skull of a seemingly male human body entombed within the hot pyroclastic flow deposits of the 79CE Vesuvius eruption formed by a unique process of vitrification of his brain at very high temperature, and is the only such occurrence on Earth,” the new study noted.
Scientists analysed fragments of the glass found inside the skull and spinal cord of the individual from Herculaneum, found lying in their bed in the Collegium Augustalium. They carried out advanced imaging using X-rays and electron microscopy to find that for the brain to become glass, it must have been heated above at least 510C before cooling rapidly.
Such organic glass couldn’t have formed if the person was heated solely by the fiery wind and ash that buried the city. That is because the temperatures of these flows did not reach higher than 465C and they would have cooled slowly.
Based on this analysis and studies of modern volcanic eruptions, researchers concluded that a super-heated ash cloud that dissipated quickly was the first deadly event during Vesuvius’s eruption.
This event likely raised the individual’s temperature above 510C before they rapidly cooled to ambient temperatures as the cloud dissipated.
The individual’s skull and spine likely protected the brain from a complete thermal breakdown and allowed fragments of this unique organic glass to form, researchers said.
