A giant cloud of ash and gases released by Vesuvius in 79 AD took about 15 minutes to kill the inhabitants of Pompeii, research suggests. The estimated 2,000 people who died in the ancient Roman city when they could not escape were not overwhelmed by the lava, but rather asphyxiated by the gases and ashes and later covered in volcanic debris to leave a mark of their physical presence millennia later.

The study by researchers from the Department of Earth and Geo-environmental Sciences of the University of Bari, in collaboration with the National Institute of Geophysics and Volcanology (INGV) and the British Geological Survey in Edinburgh, has revealed the duration of the so-called pyroclastic flow, a dense, fast-moving flow of solidified lava pieces, volcanic ash and hot gases that hit the ancient Roman city minutes after the volcano erupted.