79 A.D. ERUPTION OF MT VESUVIUS

79 A.D. ERUPTION OF MT VESUVIUS

A decade or two later the poet Statius lamented, “In the future, when crops grow again and this devastated wilderness blooms once more, will people believe that towns, people and estates are all buried beneath the soil?”(1).

August 24

At 1,00 pm, after a long rest, Mount Vesuvius suddenly began its explosive activity without any warning which could have given some clue to the inhabitants of Pompeii of what was to follow. Had there been such a warning then, perhaps such a huge loss of life could have been avoided. The telluric movements, which preceded the final disaster, were simply perceived as earthquakes, a typical feature of that territory. The eruption began with a terrifying noise: a lava cap was blown away.

Along the volcanic conduit molten magma came up, which, due to the abrupt release of the gas, became volcanic foam, expanding rapidly and rising to the surface up fragments. The column of gas, ash and pumice stones reached 15 km in height; the cloud, carried by winds in altitude, was dispersed over a very large area in South-East direction, with simultaneous rain of ash over Pompeii and Stabiae. Only a very small part of it rained over Herculaneum, where the volcanic stratigraphy reveals the presence of a thin layer of pumice stones. (2)

At 5,00 pm, The pumice stones, which reached a height of about 50 cm, destroyed the roofs of the houses with their weight. Some of the inhabitants began to flee from the city, searching in the dark “which hides things like when you are in a closed room with lights off” (Pliny the Younger, Letters to friends, VI, 20, 14) and they started to suffer from suffocation crisis due to the dense and warm air that accompanied the emission of ash. (3)

At Midnight, The volcanic column reached a height of 30 km: Mount Vesuvius started to emit 200,000 tons of fragmented magma per second.

August 25

At 1,00 – 2,00 am first collapse of a volcanic column took place, and its top lowered about 20 km. The first surge (incandescent cloud), with a temperature of about 400 degrees centigrade and a speed of about 80 kilometers per hour (10/20 meters per second) reached Herculaneum and caused instant death, by thermal shock, of its inhabitants who were seeking refuge at the beach. (4)

At 2.00 am – 6.00 am At dawn, the emission of pumice decreased, allowing the escape from the city of those who were still able to leave their homes or temporary shelters.

At 6.30 am A renewed eruptive activity caused a surge (S3) that reached Pompeii, stopping along the northern side of the walls; those people who were outside died, in the villas of the Mysteries and Diomedes and the fugitives outside of the Herculaneum Gate.

At 7.30 am Two surges (S4 and S5), which originated within a short time of each other, passed over the wall and hit the city. It was the moment of the death of the Pompeians who remained in the city or were surprised while escaping. Pyroclastic clouds also reached the Moregine area and the fluvial port of Pompeii, located at the mouth of the Sarno river. (5)

In about 20 hours of activity Mt Vesuvius spewed 10 billion tons of magma and hundreds of millions of water vapor and gases out, at a speed of 300 meters per second.

Ancient Herculaneum remained buried under a thick blanket of pyroclastic material, mud and surge between 16 and 30 meters high, above which, in the area of Villa dei Papiri, the lava of the 1631 eruption also overlapped. (6)
Pompeii was buried under a thick rain of ash and pumice stones up to 6-7 meters high.
Today, both of these Roman towns give us an amazing cross-section of all the everyday aspects of Roman civilization. (7)

Bibliography:

1) Statius, Silvae, IV,4, pp. 78-85
2) Maria Paola Guidobaldi – Ercolano – Electa Napoli 2012 – p. 7
3) Fabrizio Pesando Maria Paola Guidobaldi, Pompei, Oplontis, Ercolano, Stabiae, Guide Archeologiche Laterza 2018, p. 14
4) Maria Paola Guidobaldi, op.cit. p. 7
5) Fabrizio Pesando Maria Paola Guidobaldi, op.cit. , p. 15
6) Maria Paola Guidobaldi, op.cit. p. 8
7) A. Maiuri – Pompei – Istituto Poligrafico dello Stato – MCMLXIV – XI edizione – p. 5

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