In the fall of the year 79, Pompeii and its neighbors Herculaneum, Stabiae and Oplontis suffered a great catastrophe. Thousands of people died when Vesuvius erupted and launched volcanic bombs of pumice, ash and gases against these places, in two phases on consecutive days. Many died at home or on the streets, others burned or suffocated as their lungs filled with toxic gases and fine dust. Ash and mud covered the region and preserved those victims for posterity. Daniela Mele, from the University of Bari, and her team have determined how long it took many of the residents to die. Their study of her has been published in Scientific Reports . 

The inhabitants of Herculaneum did not have the slightest chance of survival. There, on the slopes of Vesuvius, disaster struck them fast, relentlessly, in the form of pyroclastic flows . That mixture of ash and very hot gases descended close to the slopes of Vesuvius and killed anyone who was in its area of ​​influence in just a few seconds. Pompeii is about ten kilometers further. There could have been survivors there if the pyroclastic flows had only invaded the city for a few minutes. This is the conclusion of the team of scientists, based on a model of the flows and the way the victims were preserved in ash.

According to previous studies, the thermal shock caused by clouds of gas at hundreds of degrees of temperature killed the inhabitants of Pompeii in seconds. It would have scorched them almost instantly, while they did whatever it was. What is now known contradicts this: archaeologists continue to find remains of clothing, which already with temperatures between 130 and 150 degrees would have been completely consumed. With temperatures lower than that, the victims could have survived a few minutes if the air had not been full of fine hot particles at the same time, which shorten the potential period of survival considerably, say the scientists.

According to his calculations, pyroclastic flows covered Pompeii for ten to twenty minutes; it seems to Mele and his collaborators that 17 minutes was the most likely time: too long to escape death. Consequences for current evacuation plans can be drawn from this, they write. At greater distances from the eruption, where the gas and ash have already cooled and slowed down somewhat, the length of time you can survive depends on the duration of the pyroclastic flow. Therefore, rapid intervention is required.  

Reference: « The impact of pyroclastic density currents duration on humans: the case of the AD 79 eruption of Vesuvius », by Pierfrancesco Dellino, Fabio Dioguardi, Roberto Isaia, Roberto Sulpizio and Daniela Mele, in  Scientific Reports, volume  11 , article number  4959  ( 2021 ).