“Findings from the archaeological and stratigraphic surveys conducted on the materials deposited during the eruption of Vesuvius in 79 AD were compared with the description of the event that Pliny the Young gave to Tacitus.
Together they have shed light on the progression of consequences for people and things during the eruptive event.
On the morning of 24 August 79 AD, a sudden tremor interrupted the daily routine of the inhabitants of Pompei. This was followed shortly afterwards by a tremendous blast signalling the beginning of a violent eruption with a column of lapilli rising over 20,000 meters into the sky. Carried by the wind, this cloud of lapilli hailed down upon Pompei submerging the city in just a few hours in some three meters of material. The roofs of many houses caved in under the weight, often crushing and killing those who had taken refuge within.
But the worst was yet to come.
At dawn of the following day, the first pyroclastic flow, composed of hot gas and fine ash, hit Pompei and sealed the fate of every person and animal it encountered. The burning ash clogged the lungs and caused death by suffocation.
Shortly thereafter, when already no living thing was left in the city, a second flow, much more powerful than the first, fell with fury upon the walls of the top toppling or sweeping away their upper portions. It has been calculated that this pyroclastic flow was probably travelling at speeds of between 65 and 80 kilometres per hour as it engulfed and carried off objects, roofing tiles and even the bodies of the dead Pompeians.
Other surges hit Pompei in waves after the city had already been destroyed. In the end, Pompei was left buried under 5-6 meters of ash and lapilli in a desolate grey landscape whose only features were a few protruding walls.”