The people of Pompeii were quite unprepared for the eruption of Vesuvius - getting on with their busy lives, in total ignorance of what was to come.
The signs of impending disaster, though, were there - why did no-one pick up on them?
The unexpected catastrophe
It is certain that when the eruption of Vesuvius started on the morning of 24 August, AD 79, it caught the local population utterly unprepared. Although at the same time, as we now know in retrospect, all the tell-tale signs were there to warn them.
... the sighting of a column of smoke ... triggered a response more of curiosity than of alarm
It is mainly thanks to the vivid eye-witness account of the younger Pliny (a Roman administrator and poet, whose many vivid letters have been preserved), that we have some understanding of what happened. And it is through him that we can gain insight into the reactions and feelings of the people caught up in the drama of this natural catastrophe.
Pliny's account leaves no doubt that everyone was caught unprepared. His uncle, known as Pliny the Elder, was stationed in command of the imperial naval base at Misenum, on the north-west extremity of the Bay of Naples. He was not only the senior military officer in the district, but possibly the most well informed living Roman on matters of natural science. His 37-volume Natural History is the longest work on science in Latin that has survived from antiquity.
But for all his science and his seniority, his nephew tells us that the elder Pliny was relaxing, after a bath and lunch, when Vesuvius started to erupt. And the sighting of a column of smoke 'like an umbrella pine' on the far side of the Bay triggered a response more of curiosity than of alarm in him. He and his companions were evidently not anticipating such an event.
The same account reveals, however, that the signs were there. Pliny's casual reference to earth tremors 'which were not particularly alarming because they are frequent in Campania' reveals the Roman's comprehensive ignorance of the link between seismic activity (earth tremors) and volcanic activity.