When Vesuvius erupted on the morning of 24 August, AD 79, the local population was utterly unprepared. Frustratingly evidence today suggest that all the tell-tale signs were there to warn them if only they had known what to look for. But as we all know, you can’t change the past with hindsight…
So let’s take a look back at those all important tell-tale signs.
Where exactly is Pompeii?
The ruins of Pompeii are located near the modern suburban town of Pompei (nowadays written with one ‘i’). Today it is some distance inland, but in ancient times it would have been nearer to the coast. Pompeii is about 8 km (5.0 mi) away from Mount Vesuvius and was a major city in the region of Campania.
The town was founded around the 6th–7th century BC by the Oscans, a people of central Italy. At the time of the eruption, the town may have had some 20,000 inhabitants, and was located in an area in which Romans had their holiday villas. Due to the difficult terrain, it was not distributed on a regular plan as most Roman towns were, but its streets are straight and laid out in a grid in the Roman tradition with houses and shops on both sides of the street.
The signs: A DECADE of warning
What is surprising to many is that the region suffered minor quakes in the decade leading up to the great eruption. Knowing this makes it easy to assume that the people of Pompeii should have seen it coming, but as the writer Pliny the Younger wrote, “earth tremors were not particularly alarming because they are frequent in Campania”. This reveals the Roman’s comprehensive ignorance of the link between seismic activity (earth tremors) and volcanic activity.
For instance on 5 February 62 AD there was a severe earthquake which did considerable damage around the bay and particularly to Pompeii. It is believed that the earthquake would have registered between about 5 and 6 on the current Richter scale. We know this quake must have caused considerable damage as there was extensive rebuilding of the town during the time of the 79 AD eruption when there was a comprehensive programme of restructuring of public buildings in the Forum of Pompeii. This demonstrates the impressive resilience of the local population.
The volcanologists of today constantly monitor any changes in levels of seismic activity from the observatory on Vesuvius, because they know that the same increase of activity in the deep reservoir of magma (molten or partially molten rock beneath the Earth’s surface) causes both earth tremors and volcanic eruptions. Through measuring seismic activity, these scientists expect to predict an approaching eruption months in advance.
They also know that the activity of Vesuvius is recurrent, and that the longer the intervals between one eruption and another, the greater the eventual explosion will be. The frequent but low-level activity of Vesuvius in recent centuries has relieved the build-up of pressure in the magma chamber. The catastrophic magnitude of the eruption of AD 79 was connected with the extended period of inactivity that preceded it. A long interval combined with mounting seismic activity is a sure sign of impending disaster.
Of course, the Romans could not know this, and our own knowledge owes much to the care of Pliny’s description. The long inactivity of the volcano naturally lulled the people of the region into a false sense of security, though they were aware of the signs of burning at the peak of the mountain.
The day was the 24th August, just one day after Vulcanalia, the festival of the Roman god of fire – and ironically volcanoes.
Recent studies indicate that at Vesuvius and surrounding towns the heat was the main cause of death of people, previously believed to have died by ash suffocation. The results of the study, published in 2010, show that exposure to at least 250 °C (482 °F) hot surges at a distance of 10 kilometres (6 miles) from the vent was sufficient to cause instant death, even if people were sheltered within buildings.
The people and buildings of Pompeii were covered in up to twelve different layers of tephra, in total 25 meters deep, which rained down for about 6 hours.
From his position across the Bay of Naples at Misenum, Pliny the Younger provided a first-hand account of the eruption of Mount Vesuvius. Interestingly, his uncle, Pliny the Elder, with whom he had a close relationship, died while attempting to rescue stranded victims. As Admiral of the fleet, Pliny the Elder had ordered the ships of the Imperial Navy stationed at Misenum to cross the bay to assist evacuation attempts.
The eruption lasted for more than 24 hours from its start on the morning of 24 August. Those who fled at once, unburdened by possessions, had a chance of survival, for the rain of ash and pumice, mixed with lithics, that descended for several hours was not necessarily lethal. It is clear that many, like the elder Pliny, thought their best chance was to take shelter and weather the storm.
It was not until around midnight that the first pyroclastic surges and flows occurred, caused by the progressive collapse of the eruptive column, and these meant certain death for the people of the region. (A pyroclastic flow is a ground-hugging avalanche of hot ash, pumice, rock fragments and volcanic gas, which rushes down the side of a volcano as fast as 100 km/hour or more.)
The hundreds of refugees sheltering in the vaulted arcades at the seaside in Herculaneum, clutching their jewellery and money, met their end swiftly – from the intense heat of the first surge that reached the city.
Subsequent waves reached Pompeii, asphyxiating those who had survived the fall of 3m (10ft) of pumice, and were fleeing across the open in the dark, or hiding beneath roofs. The waves that followed smashed flat the upper floors of houses, and left the corpses encased in successive blankets of gaseous surge and pumice fall.
Extent of the destruction
It is impossible to tell what proportion of the inhabitants died, but the Romans were accustomed to losses mounting to tens of thousands in battle, and even they regarded this catastrophe as exceptional. The corpses found by archaeologists in Pompeii or Herculaneum should be regarded as only a small sample: the destruction encompassed the entire landscape south of Vesuvius to the Sorrentine peninsular. As many died in the countryside or at sea as in the cities. Even as far north as Misenum, the ash lay deep in drifts.
And so, we will end on a question? If you could travel back in time, would you meddle with history?
Knowing what we know today, would you tell the Pompeian people of their impending fate?