Intense Heat From Ancient Vesuvius Eruption Caused Victims' Skulls to Explode

The eruption prompted a second wave of evacuations, but with a vastly shorter window of opportunity. Overflowing, the remaining inhabitants of Pompeii, including those living in the near settlements of Herculaneum, Stabiae, and Oplontis, were overwhelmed by avalanches of gas and dust, known as hot surge clouds and pyroclastic flows, pouring down quickly from the mountain. By the time the two-day eruption was over, nearly 2,000 people had died.

That fast-moving pyroclastic influx of gas and ash killed during the eruption is well documented. During the Vesuvius eruption, six distinct surges hurtled through a region extending for 18 miles (30 kilometers). The first of these surges, known as S1, is the superheated gas cloud. The authors of the new study, led by Pierpaolo Petrone from the Federico II University Hospital in Naples, Italy, say many of Vesuvius' victims were killed before the subsequent ash-filled pyroclastic flows reached them. Previous studies have shown the same thing, citing "thermally induced fulminant shock" as a typical cause of death, as opposed to getting slammed by a wall of ash, suffocating, or getting clobbered by a boulder.

As a term, thermally induced fulminant shock is not very descriptive, even if it does sound dreadful. But that's where the new study, published recently in PLoS One, has new things to offer. The superheated surge clouds the bodily fluids of victims in an instant, the researchers say, producing a gruesome effect in the skull, causing it to crack and explode.

The evidence for these claims comes from an archaeological site in Herculaneum, which like Pompeii, was completely buried in ash and mud after the eruption. Soon after Vesuvius erupted, around 140 citizens sought shelter in a dozen boat-chambers, or houseboats, on the town's beach. None survived, but the occupants of these impromptu shelters were spared from the incoming ash avalanches, resulting in "the unique preservation of fully articulated skeletons" still in their final death pose, the authors write.

This site was discovered in the 1980s, and it was the subject of intense study ever since. It is widely believed that the hundreds of people stranded on the Herculaneum were overcome by the extreme heat. The refugees in the boat-chambers, it has been argued, died from asphyxiation after the concrete-like ash smothered the shelters. The new analysis suggests this case, and that, like the people on the beach, these victims were also killed by the heat.

The smoking gun for this claim comes in the form of red and black residues found on the skulls and other bones of the victims inside the boat-chambers. Petrone and his colleagues analyzed 100 samples found at the site using Raman Microspectroscopy and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which can detect the presence of minerals at exceptionally low concentrations. The red and black rests contain an uncommon amount of iron, which the researchers say is consistent with blood.

"These findings, the authors write in the study," suggesting that it is extremely important that it should not be exposed to volcanic ash or other volcanic products, that it might have originated from the victims' body fluids. "

Physical examination of the remains offered further proof. Here's how the authors describe it in their study:

In the present work, careful inspection of the victims' skeletons revealed cracking and explosion of the skullcap and blackening of the inner and inner [layers of the cranial bone], associated with black exudations [i.e. when liquid pours out] from the skull openings and the fractured bone. Such effects appear to be the result of direct exposure to heat and an increase in intracranial steam pressure by ebullition [boiling]with skull explosion as the possible outcome.

After the organic liquids in the brain evaporated, the brain was almost immediately replaced by a chunk of ash. An "ash cast" was found in all of the victims, including those who displayed minor heat effects, providing "evidence that the S1 was readily opened and fluid to penetrate the intracranial cavity soon after soft tissue and fluid fluids disappeared," the authors write. 400 to 500 degrees Celsius (750 to 930 degrees Fahrenheit).

This all sounds unbelievably awful, but these victims died instantly, if that's any consolation. We know this because of their way of being in the chamber (this kind of analysis was possible, the authors say, "extraordinarily well-preserved skeletal joints fixing the body shape in three-dimensional space"). People who have been killed by the ash-filled pyroclastic fluids are exposed to temperatures around 200 to 250 degrees C (400 to 480 degrees F); their bodies burned, their muscles contracted, resulting in a final "pugilistic" body posture in which their toes and fingers were curled inwards. The victims in the boat-chambers, on the other hand, had "life like" death poses, suggesting an instant death. The lack of a "complete pugilistic pose in the victims" corpses at Herculaneum may indicate that the muscles disappeared more quickly than they contracted, "the researchers write. This life-like stance, the researchers argue, can "only be explained by the rapid replacement of flesh by ash."

The phrase "rapid replacement of flesh by ash" is certainly as poetic as it is horrifying.

The authors use an array of tools in their area, while paying close attention to the previous work done in this area. If there is a shortcoming of the study, however, it is the analysis of the red and black minerals. The claims being made are so extraordinary that, ideally, other teams would make the findings and make sure the iron (if that's what it is) is not coming from somewhere else (e.g. coins and other metal objects found within the chambers). It would also be good to see if another team agrees with the morphological analysis done on the skull and bones.

To this day, Mount Vesuvius remains an active volcano, and it's located a mere 8 miles (12 kilometers) from Naples, a large Italian city populated by 3 million people. It's estimated that Vesuvius has had a huge eruption every ounce of history, so that it has been eroded 1,999 years ago. Now, that does not mean an explosion is imminent, but it is a cause of serious concern. Fortunately, local officials have an emergency plan should the worst happen again.