THE 79 A.D. ERUPTION

The 79 A.D. eruption undoubtedly is Vesuvius' most famous eruption, and perhaps even the most famous volcanic eruption in history. It was described by Pliny the Younger in two well-known letters to Tacitus, which constitute valuable documentation for volcanologists (see "Historical Eyewitness Accounts"). In the letters he recounts the death of his uncle, Pliny the Elder, who set off from Miseno by ship to rescue people during the eruption. This is the origin of the term Plinian eruption to denominate this particularly violent and destructive phenomenon.

The eruption started at around 13 o'clock in the afternoon of 24th August; the conduit opened after a series of explosions due to the immediate vaporisation of surface water coming into contact with rising magma. Then an eruption column of gas, ash, pumice and lithic fragments rose up into the air to a height of about 15 km above the volcano. This phase of the eruption lasted until around 8 o'clock the next morning, and was accompanied by frequent earthquakes.

During the night many people took advantage of an apparent lull in the eruptive activity, to go back to their homes which they had abandoned in haste. But they were surprised during the course of the morning by the reawakening of the volcano. This time there was a total collapse of the eruption column, causing the formation of pyroclastic flows which led to the total destruction of the areas of Ercolano, Pompei and Stabia.

Body casts of some victims from Pompei

During the final part of the eruption, probably in the late morning of 25th August, pyroclastic flows continued to form; their deposits totally buried the surrounding villages while a dense cloud of ash spread into the atmosphere reaching as far as Capo Miseno.

Historical Eyewitness Accounts

He [Pliny the Elder] was at Miseno leading the fleet. On August 24th, barely an hour had passed after midday, when my mother pointed out to him a cloud which had appeared, the like of which had never been seen before in size and shape. [...] We could not be sure which mountain the cloud rose from, as we were looking from a great distance; only later did we realise that it was from Mt. Vesuvius. This cloud resembled a pine (Mediterranean pine) more than any other tree.
As from an enormous trunk, the cloud rose high into the sky and spread out as if it were growing branches. I believe, because it was first blown high by a strong gust of wind, all in one piece, then as it grew smaller it was dropped, or, maybe because of its overpowering weight, the cloud expanded umbrella-like: it shone brilliantly white at times, then at others appeared dirty, darkened by different colour stains depending on the prevalence of the ash or sand that it had lifted up with it.

There follows in the letter, an account of the events that led to the death of Pliny the Elder. He was curious about this extraordinary phenomenon and so decided to go closer with a small boat. In the meantime he received a message with a plea for help from some friends (Rectina, wife of Tascus) who were in the area of Vesuvius.

He changed his mind: the natural anxiety of the scientist gave way to the spirit of the hero. He had the Quadriremi boats let down, and took his place. He wanted to bring help not only to Rectina, but to many others as the happy land was very populated.
He hurried to the place from where others fled and stayed at the helm, setting a straight course towards danger, without a trace of fear, to such an extent that he dictated and noted all the details of this terrible event, all the faces that his astonishd eyes fell upon.

Pliny directed his boats towards Torre del Greco, but, unable to land, he changed his course to Stabia, where his friend, Pomponianus, had a villa:

The ash was already falling onto the boats, gradually getting hotter and thicker the closer they drew; pieces of pumice and blackened stones, burnt and broken by the fire were already falling; already the shallows and the shore were, unexpectedly, too damaged by the mountain to permit a landing. He had a moment's hesitation as if to turn back, as indeed his mate advised him to do, but suddenly called: "Fortune is with the brave. We reach Pomponianus!"
[...]
Pomponianus had already loaded his baggage aboard ships and was determined to flee as soon as the adverse wind calmed. For my uncle, however, the wind blew in a favourable direction and thay managed to land. He embraced his fearful friend, consoled him, and tried to give him courage.
[...]
In the meantime in many points on Mount Vesuvius widespread flames glowed brightly and high columns of fire: their brightness stood out all the more against the darkness of the night.

Staying in his friend's villa that night, Pliny withdrew to his rooms and slept. But…

[...] the courtyard leading to the appartment had been filled up so high with ash and lapilli, that if he had waited any longer inside, he would not have been able to get out at all. So he was woken up. He came outside and met up with Pomponianus again and the others who had not slept at all. They debated over whether it was in their common interest to stay indoors or to roam around outside. Indeed the house itself shook with the frequent, violent quakes and almost came apart at its foundations, as it seemed to sway first this way, then that, and then to regain composure again and be still.
Besides, outdoors there was the fear of falling lapilli, even though they were light and worn. Anyhow they weighed up the risks and chose to go into the open air. He was deep in thought, the others overcome by fears. They put pillows over their heads andfastened them with cloth, and thus defended themselves against the hail of lapilli. Elsewhere ot was already daylight, there it was night: a deeper, blacker night than any other night. However many fires and lights lit up the place. They discussed whether to reach the beach and to see from the nearest point if by now the sea would allow them to try to flee. But the rough sea was still against them. There he threw down a cloth and lay down…

Pliny the Elder, probably asphyxiated by gases, was overcome, and unable to continue his flight, was abandonned by his companions. His body would only be found three days later.
The letter ends with a note:

The whole of my narrative is based on direct experience and on news heard immediately after the catastrophe, when memory of the events is closest to the truth. You will select the most important parts, because writing a letter is not the same as writing a story, just as a letter to a friend is not the same as a letter to all.

Tacitus, however was very interested in his friend's personal experience and asked him to write more, to let him know what it had been like at Miseno, during these tragic events. Thus Pliny the younger wrote a second letter, describing the intense phenomena that had taken place in the Phlegrean area too, during the eruption of 79 A.D. Indeed, he, his mother and many other inhabitants of Miseno abandoned their houses to find shelter in the surrounding countryside. He writes:

Previously, for many days, the earth had been shaking without causing us too much fear, because earthquakes are a common phenomenon in Campania. But that night the earth shook with particular violence and we had the impression that everything was being not so much shaken, as turned upside-down.
[...]
Day had already broken, an hour before and the light was hesitant, without brightness. The houses around were already smashed. The area where we found ourselves, although out in the open, was still oppressive and the danger of a collapse was great, or rather certain.
Only then did we decide to leave the city of Miseno.
[...]
Once outside the built-up area we had a rest. We saw many marvellous sights, and suffered many torments. We had had wagons sent along with us, and although the gound was perfectly flat, they jolted first in one direction, then the other, and even when propped up with rocks, they did not stay still in one place.
In addition we saw the sea draw back, almost as if driven away by the earthquake. Without any doubt, the shore was much wider, and a large number of fish had been left high and dry on the sand.
[...]
Dalla parte orientale, un nembo nero e orrendo, squarciato da guizzi sinuosi e balenanti di vapore infuocato, si apriva in lunghe figure di fiamme: queste fiamme erano simili a folgori, anzi maggiori delle folgori.
[...]
Non molto tempo dopo quel nembo discende sulle terre, copre la distesa del mare. Avvolse Capri e la nascose, sottrasse al nostro sguardo il promontorio di Miseno.
[...]
Rischiarò un poco: non riappariva la luce del giorno, ma era un indizio che il fuoco stava per avventarsi sopra di noi. Ma il fuoco, a dire il vero, si fermò abbastanza lontano. Fu tenebra di nuovo: fu cenere di nuovo, fitta e pesante. Noi ci alzavamo ripetutamente e ci scrollavamo di dosso la cenere. Altrimenti ne saremmo stati coperti e il suo peso ci avrebbe anche soffocato.
[...]
Alla fine quella tenebra diventò quasi fumo o nebbia e subito ritornò la luce del giorno, rifulse anche il sole: un sole livido come suole essere quando si eclissa. Dinanzi ai miei occhi spauriti tutto appariva mutato: c'era un manto di cenere alta come di neve.