Following the eruption of Mount Vesuvius in 79 AD, the city of Herculaneum was hit by a cloud of ash so hot that it incinerated the bodies and vitrified the brains of everyone present, according to analysis of carbonized wood samples carried out by a team of geologists led by Guido Giordano of Roma Tre University and anthropologist Pier Paolo Petrone of the Federico II University of Naples.
The results, published in Scientific Reports, provide a more precise reconstruction of the thermic events associated with the famous eruption.
The study shows that a first cloud of ash hit Herculaneum very briefly at an initial temperature of 500-600 degrees before reaching the coast, causing the immediate death of all in its path. The interaction between the hot ash and seawater then caused the cloud to swell and cool ash was deposited soon after, burying the dead. The city was then gradually hit by subsequent pyroclastic flows at relatively lower temperatures.
The timing of these events appears to explain the vitrification of the brain tissue of a Herculaneum resident. Indeed, the extreme brevity of the first ash cloud would have prevented the brain tissue from being completely vaporized, while the time lapse before the next pyroclastic flow would have allowed for the rapid cooling necessary for transformation into glass.
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