Background: Eruption
- Plinian eruptions are to be considered the most violent and powerful type of volcanic activity, the tragedies bestowed upon the cities of Pompeii and Herculaneum and it's people in 79AD are demonstrations of the capability of these kind of eruptions.
- The name "Plinian" derives from the famous Roman senator and writer Pliny the Younger, who described the behaviour of the eruption in letters he wrote about the death of his uncle, Pliny the Elder, a famous naturalist who had died during this event. Due to the limited amount of surviving information from the time of Vesuvius's eruption, his letters are regarded highly as a primary source.
- According to the letters of Pliny the Younger, there had been small emissions occurring a few days prior to the eruption. The significance of these warnings were promptly disregarded as people had become accustomed to the constant trembling.
“For several days past there had been earth tremors which were not particularly alarming because they are frequent in Campania; but that night the shocks were so violent that everything
felt as if were not only shaken but overturned.” - At about midday on August 24th 79AD the peak of Mt Vesuvius exploded, signalling the liveliness of the formerly dormant volcano. Shortly after the eruption, a column of
volcanic material arose from the mouth of Vesuvius at about 20km high. The volcanic cloud, composed of ash, pumice and gas, was "...of unusual size and appearance…being like an umbrella pine, for it rose to a great height on a sort of trunk and then split off into branches…” (Pliny the Younger). - The original city of Pompeii was 39 metres (128ft) above sea level, located on a
prehistoric lava flow about 8 kilometres (5 miles) from Mount Vesuvius. Herculaneum,
another village in the region, was less than 7 kilometres (4.4 miles) from the base of
the volcano. - The swelling dark cloud continued to consume the skies until its weight
became intolerable and tephra began to fall, blown to the south-east by a strong
wind. Pompeii, which lay in that direction, was immediately exposed to the rain
of ash and pumice which covered and destroyed buildings. - While Pompeii was raided with pumice, the nearby town of Herculaneum which lay to the west of Vesuvius experienced only a few centimetres of ash downfall, causing minor damage but even so inhabitants began to flee. This continued throughout the night, outbreaks of fires caused by shattered lanterns spread light across the unearthly darkness that encased the cities of Pompeii and Herculaneum, due to the volcanic dust that was impenetrable by sunlight. But by the second day Herculaneum had become completely buried due to the large surges of volcanic mud that swept across the town, fully encasing it.