In 79 CE, Vesuvius erupted, emitting huge clouds of volcanic ash and casting settlements 20 kilometers (12 miles) from the crater in dust. It's safe to say that any form of volcanic-induced death is not a pleasant way to go but research recently published in the journal PLOS ONE suggests that – at least for some – it may have been even more gruesome than we thought.
According to a team of archaeologists led by Pierpaolo Petrone at the Federico II University Hospital in Naples, some victims may have died after their bodily fluids were vaporized by the intense heat of the first pyroclastic surge. This would have caused steam pressure to build up inside the body until it reached a tipping point, causing the skull to explode.
They came to this conclusion after studying the mineral residue sticking to skeletons discovered in 12 waterfront chambers in Herculaneum, a Roman seaside town of just 4,000 to 5,000 inhabitants. These Roman boat houses were the last refuge of 300 residents, where they died instantly from the wave of gas and rock fragments spat from Vesuvius's crater.
From the remains, the team examined 103 archaeological samples encrusted in residue ranging in color from light red to dark red and black, using inductively coupled plasma mass spectrometry (ICP-MS) – a technique that can detect tiny traces of metals (and some non-metals). Twenty-two of these samples were then analyzed using Raman microspectroscopy to identify the residue's chemical fingerprint. The results revealed traces of iron and iron oxide, likely, the researchers say, from blood exposed to intense levels of heat.
The highest amounts of iron were found in the red-colored incrustations, found on cranial and postcranial bones, the ash filling the skulls, the ash-bed, and the sand. In contrast, the lowest amounts were found in the black-colored incrustations on bones and sand.
"These findings indicate that the extremely high content of iron could not be ascribed to volcanic ash or other volcanic products, suggesting that it might have originated from the victims' body fluids," explained the study authors.
The results are not conclusive – some residue may have originated from metal objects (coins, jewelry, and other personal artifacts belonging to the victims) located nearby. But in support of Petrone's blood-boiling hypothesis, there were skulls and bones that were not close to metal objects and still coated in the iron-containing residue. What's more, color changes, carbonization, and cracking (all indicative of tissue exposed to high temperatures) were found in the victims' bones and skulls.
The position of the skeletons again hints at an instant death, like sudden body fluid vaporization, as opposed to something more drawn out. The study authors describe the bodies as "frozen" in a life-like stance rather than a voluntary self-protective position or pose suggesting they were in intense agony, emblematic of a slower death like asphyxiation (which was previously assumed to be their cause of death).
"Here we show for the first time convincing experimental evidence suggesting the rapid vaporization of body fluids and soft tissues of the 79 AD Herculaneum victims at death by exposure to extreme heat," the study authors concluded.
"The detection of such iron-containing compounds from the skull and the ash filling the endocranial cavity, coupled with brown coloration of venous sinuses, bone blackening and cracking, strongly suggests 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."