When Vesuvius erupted in 79AD, the avalanche of volcanic ash that hit Herculaneum caused people's blood to vaporize and their skulls to explode, new analysis of their skeletons has revealed.
When the town of Herculaneum was hit, 300 people took shelter in 12 waterfront chambers located along the beach. In a study published in PLOS One, scientists led by Pierpaolo Petrone, from the Federico II University Hospital in Naples, Italy, looked at skeletons found in these chambers to find out what happened to them at the point of death.
The eruption at Vesuvius was huge. It is estimated to have spewed ash, rock and volcanic gas up to 21 miles into the air and sent lava flowing down the mountain towards the settlements below, with temperatures reaching up to 500C. The level of preservation at the two sites is unprecedented—victims were essentially frozen in time, having been killed instantly then buried under volcanic material for over 1,600 years.
In the latest research, the team looked at the mineral residues encrusting the bones. They looked at how ash filled their skulls and encased the skeletons. From this, they carried out laboratory analysis and placed their results in the context of the archaeological site—the waterfront chambers that would have felt like an oven from the extreme temperatures produced by the volcano.
Petrone and colleagues discovered highly unusual red and black mineral residues covering the skeletons. This was also found inside their skulls.
Further analysis led them to conclude the bodily fluids of the victims had been vaporized. Their blood would have boiled and their skulls would have exploded. "An extraordinary find concerns skulls filled with ash, which indicates that after evaporation of the organic liquids the brain was replaced by ash," they wrote. "The presence of such an ash cast in all victims, even those showing minor heat effects, provides evidence that the surge was sufficiently hot and fluid to penetrate the intracranial cavity soon after soft tissues and organic fluids disappeared."
Concluding, the researchers say this is the first experimental evidence showing rapid vaporization of body fluids and soft tissues.
The findings, they say, "strongly suggest a widespread pattern of heat-induced hemorrhage, intracranial pressure increase and bursting, most likely to be the cause of instant death of the inhabitants in Herculaneum."
The residents of Pompeii, Petrone told Newsweek, suffered a slightly different fate as the avalanches of hot ash and steam was not quite as hot. "While at Herculaneum, more close to the volcano (around three miles), the heat—established by our laboratory experiments to be of at least 500C—was high enough to kill people instantly and let the flesh of their bodies to rapidly vanish by vaporization of body tissues and fluids.
"In Pompeii, placed at about six miles from the vent, the lower temperature of about 250-300C was sufficient to kill people instantly, but not hot enough to vaporize the flesh of their bodies. So, after cooling of the ash surge deposit around the intact victims' bodies, the slowly disappearing of the flesh left a hallow cavity around the skeleton and the negative imprint of the body in the hardened ash, thus allowing to fill such cavity by plaster and therefore obtaining the plaster casts of the victims, casts that obviously still contain the skeleton of the victim."
Researchers say the latest findings are important in terms of the risk posed by the volcano today. Around three million people live near Vesuvius—the center of Naples is just over eight miles from the summit—and the volcano is still active. It will, at some point, produce another big eruption.
"This kind of field and laboratory studies are of great importance not only from the point of view of an historical and biological reconstruction of the Roman age populations, but also because provide fundamental information useful for the assessment of volcanic risk in densely populated areas," Petrone said.
This story has been updated to include quotes from Pierpaolo Petrone.