A giant cloud of ash and gas released by Vesuvius in 79 AD took about 15 minutes to kill the inhabitants of Pompeii, the research suggests.
Numerous studies have confirmed that about 2,000 people who died in the Roman city were asphyxiated rather than killed by the lava. And the work of researchers at the University of Bari, in collaboration with the National Institute of Geophysics and Volcanology (INGV) and the British Geological Survey in Edinburgh, says that the pyroclastic flow – a fast, dense stream of solidified lava pieces, volcanic ash and hot gases – engulfed Pompeii just minutes after the volcano erupted.
The lethal cloud had “a temperature above 100 degrees and was composed of CO2, chlorides, particles of incandescent ash and volcanic glass,” said Roberto Isaia, senior researcher at INGV’s Vesuvius Observatory. “The objective of the work was to develop a model to try to understand and quantify the impact of pyroclastic flows in the inhabited area of Pompeii, about 10 km [6 miles] of Vesuvius, ”he added.
The study confirms that the residents had no escape, with the majority of those who died suffocated in their homes and beds, or in the streets and squares of the city. Isaia’s model estimates that gases, ash and volcanic particles would have engulfed the city for between 10 and 20 minutes.
“It is likely that dozens of people died due to the lapilli rain that fell on Pompeii after the eruption, but most died of asphyxiation,” said Isaia, adding that the pyroclastic flow would have reached Pompeii within minutes of the explosion.
“Those 15 minutes inside that hellish cloud must have been endless. The inhabitants could not imagine what was happening. The Pompeii lived with earthquakes, but not with eruptions, so they were taken by surprise and swept away by that incandescent cloud of ash. “
INGV’s research described pyroclastic flows as “the most devastating impact” of explosive eruptions. “Comparable to avalanches, they are generated by the collapse of the eruptive spine. The resulting volcanic ash runs along the slopes of the volcano at speeds of hundreds of kilometers per hour, at high temperatures and with a high concentration of particles. “
Today, the ruins of Pompeii are the second most visited archaeological site in Italy, after the Colosseum in Rome and, last year, attracted around one million tourists.
“It is very important to be able to reconstruct what happened during the last eruptions of Vesuvius, from the geological record, to trace the characteristics of the pyroclastic currents and the impact on the population”, said Prof Pierfrancesco Dellino, from the University of Bari.
“The scientific approach adopted in this study reveals information contained in pyroclastic deposits and that sheds light on new aspects of the Pompeii eruption and provides valuable information for interpreting Vesuvius’ behavior, also in terms of civil protection.”