Mount Vesuvius

Mount Vesuvius is located on the Gulf of Naples in Campania, Italy, about 5½ miles east of Naples and a short distance from the shore. It is one of several volcanoes which form the Campanian volcanic arc. Others include Campi Flegrei, a large caldera a mile or so to the north west, Mount Epomeo, 12 miles to the west on the island of Ischia, and several undersea volcanoes to the south. The arc forms the southern end of a larger chain of volcanoes which extends northwest along the length of Italy as far as Monte Amiata in Southern Tuscany. Vesuvius is the only one to have erupted within recent history, although some of the others have erupted within the last few hundred years. Many are either extinct or have not erupted for tens of thousands of years. Vesuvius is a distinctive "humpbacked" peak, consisting of a large cone (Gran Cono) partially encircled by the steep rim of a summit caldera caused by the collapse of an earlier and originally much higher structure called Mount Somma. The Gran Cono was produced during the A.D. 79 eruption. For this reason, the volcano is also called Somma-Vesuvius or Somma-Vesuvio. Vesuvius was considered a divinity at the time of the eruption of AD 79: it appears under the inscribed name Vesuvius as a serpent in the decorative frescos of many lararia, or household shrines, surviving from Pompeii. The historian Diodorus Siculus relates a tradition that Hercules, in the performance of his labours, passed through the country of nearby Cumae on his way to Sicily and found there a place called "the Phlegraean Plain" (phlegraion pedion, "plain of fire"), "from a hill which anciently vomited out fire ... now called Vesuvius." It was inhabited by bandits, "the sons of the Earth," who were giants. With the assistance of the gods he pacified the region and went on. Any facts behind the tradition remain unknown, as does whether Herculaneum was named after it. An epigram by the poet Martial in 88 AD suggests that both Venus, patroness of Pompeii, and Hercules were worshipped in the region devastated by the eruption of 79. The famous eruption in AD 79 was preceded by numerous others in prehistory, including at least three significantly larger ones, the best known being the Avellino eruption around 1800 BC which engulfed several Bronze Age settlements of the Apennine culture. Recent archaeological techniques have revealed remarkably well-preserved forms of perishable objects, such as fence rails, a bucket and especially, in the vicinity, thousands of human footprints pointing into the Apennines to the north. The settlement had huts, pots and goats. The residents had hastily abandoned the village, leaving it to be buried under pumice and ash in much the same way that Pompeii and Herculaneum were later preserved. Pyroclastic* surge deposits were distributed to the northwest, travelling as far as nearly 10 miles, and lying up to 10 feet deep in the area now occupied by Naples.

*A pyroclastic flow is described by the US Geological Survey as “A ground-hugging avalanche of hot ash, pumice, rock fragments, and volcanic gas that rushes down the side of a volcano as fast as 100 km/hour or more. The temperature within a pyroclastic flow may be greater than 500° C, sufficient to burn and carbonize wood. Once deposited, the ash, pumice, and rock fragments may deform (flatten) and weld together because of the intense heat and the weight of the overlying material.”

Since the eruption of AD 79, Vesuvius has erupted around three dozen times. It erupted again in 203, during the lifetime of the historian Cassius Dio. In 472, it ejected such a volume of ash that ashfalls were reported as far away as Constantinople. The eruptions of 512 were so severe that those inhabiting the slopes of Vesuvius were granted exemption from taxes by Theodoric the Great, the Gothic king of Italy. Further eruptions were recorded in 787, 968, 991, 999, 1007 and 1036 with the first recorded lava flows. The volcano became quiescent at the end of the 13th century and in the following years it again became covered with gardens and vineyards as of old. Even the inside of the crater was moderately filled with shrubbery. Vesuvius entered a new phase in December 1631, when a major eruption

buried many villages under lava flows, killing around 3,000 people. Activity thereafter became almost continuous, with relatively severe eruptions occurring in 1660, 1682, 1694, 1698, 1707, 1737, 1760, 1767, 1779, 1794, 1822, 1834, 1839, 1850, 1855, 1861, 1868, 1872, 1906, 1926, 1929 and 1944.

The eruption of April 5th 1906 killed more than 100 people and ejected the most lava ever recorded from a Vesuvian eruption. Italian authorities were preparing to hold the 1908 Summer Olympics when Mount Vesuvius violently erupted, devastating the city of Naples and surrounding communes. Funds were diverted to the reconstruction of Naples, requiring a new location for the Olympics to be found. The last major eruption was on March 18th 1944 which destroyed the villages of San Sebastiano al Vesuvio, Massa di Somma, Ottaviano, and part of San Giorgio a Cremano. At the time of the eruption, the United States Army Air Forces (USAAF) 340th Bombardment Group was based at Pompeii Airfield near Terzigno, close to the eastern base of the volcano. The tephra and hot ash damaged the B-25 Mitchell medium bombers and 78 to 88 aircraft were destroyed.

Another casualty of the 1944 eruption was the funicular cable car which had opened in 1880, commemorated in "Funiculì, Funiculà", the famous Neapolitan language song with lyrics by journalist Peppino Turco set to music by composer Luigi Denza.

There have been no eruptions since 1944, and none of the eruptions after AD 79 were as large or destructive as the Pompeian one. The eruptions varied greatly in severity but are characterized by explosive outbursts of the kind dubbed Plinian after Pliny the Younger, who wrote a detailed description of the 79 AD eruption. A few times since 1944, landslides in the crater have raised clouds of ash dust, raising false alarms of an eruption.

It seems that for Vesuvius, the amount of magma expelled in an eruption increases very roughly linearly with the interval since the previous one, and at a rate of around 0.001 cubic kilometres for each year. This gives an approximate figure of 0.07 cubic kilometres for an eruption after 70 years of inactivity. (For comparison, the 79 AD eruption was about 1.0 cubic kilometres and those of 472 and 1631 were about 0.1.) Mount Vesuvius is the only volcano on the European mainland to have erupted within the last hundred years and is still regarded as an active volcano, although its current activity produces little more than sulphur-rich steam from vents at the bottom and walls of the crater. It is also classed

as one of the most dangerous volcanoes in the world because of the population of 3,000,000 people living nearby and its tendency towards violent, explosive eruptions of the Plinian type, making the area the most densely populated volcanic region in the world. The government emergency plan for an eruption therefore assumes that the worst case will be an eruption of similar size and type to the 1631 one. In this scenario the slopes of the volcano, extending out to about 4½ miles from the vent, may be exposed to pyroclastic surges sweeping down them, whilst much of the surrounding area could suffer from tephra falls. Because of prevailing winds, towns and cities to the south and east of the volcano are most at risk from this, and it is assumed that tephra accumulation exceeding 20 lb/sq ft – at which point people are at risk from collapsing roofs – may extend out as far as Avellino to the east or Salerno to the south-east. Towards Naples, to the north west, this tephra fall hazard is assumed to extend barely past the slopes of the volcano. The specific areas actually affected by the ash cloud will depend upon the particular circumstances surrounding the eruption.

The plan assumes between two weeks and 20 days' notice of an eruption and foresees the emergency evacuation of 600,000 people, almost entirely comprising all those living in the zona rossa ("red zone"), i.e. at greatest risk from pyroclastic flows. The evacuation, by trains, ferries, cars, and buses is planned to take about 7 days, and the evacuees will mostly be sent to other parts of the country rather than to safe areas in the local Campania region, and may have to stay away for several months. However, the dilemma that would face those implementing the plan is when to start this massive evacuation, since if it is left too late then thousands could be killed, while if it is started too early then the precursors of the eruption may turn out to have been a false alarm. In 1984, 40,000 people were evacuated from the Campi Flegrei area, another volcanic complex near Naples, but no eruption occurred. Ongoing efforts are being made by the government at various levels (especially of Campania) to reduce the population living in the red zone, by demolishing illegally constructed buildings, establishing a national park, in 1995, around the whole volcano to prevent the future construction of buildings and by offering sufficient financial incentives to people for moving away. One of the underlying goals is to reduce the time needed to evacuate the area, over the next 20 or 30 years, to 2-3 days. The volcano is closely monitored by the Osservatorio Vesuvio in Naples (founded in 1841 on the slopes of Mount Vesuvius (the operative centre is now in Naples) by Ferdinando II di Borbone, king of "Due Sicile", it is the oldest volcanology institute in the world) to track magma rising underneath the volcano. In 2012 no magma had been detected within 10 km of the surface, and the volcano was classified as at a Basic or Green Level.

The area around Vesuvius was officially declared a national park on June 5, 1995. The summit of Vesuvius is open to visitors and there is a small network of paths around the volcano that are maintained by the park authorities. There is access by road to within 660 ft of the summit (measured vertically), but thereafter access is on foot only. There is a spiral walkway around the volcano from the road to the crater.

The 79 AD Eruption The eruption of Mount Vesuvius in 79 AD was one of the most catastrophic volcanic eruptions in European history. Historians have learned about the eruption from the eyewitness account of Pliny the Younger, a Roman administrator and poet, who was then 17 years old and staying with his uncle, Pliny the Elder, in Misenum, from where he wrote two letters to the historian, Tacitus. The volcano had been quiet for nearly 300 years and was described by Roman writers as having been covered with gardens and vineyards, except at the top, which was craggy. The volcano may have had only one summit at that time, judging by a wall painting, "Bacchus and Vesuvius", found in a Pompeian house, the House of the Centenary (Casa del Centenario). The painting depicts Vesuvius with a single vineyard-covered peak instead of the double-peak profile of today. Although some scholars reject the single-peak hypothesis, the painting is generally regarded as the earliest known representation of the volcano, even if it should not be taken as a record of what Vesuvius actually looked like. Literary sources also describe Vesuvius as covered in grape vines before the eruption. Plutarch says that vines had grown on it in the 1st century BC, when Spartacus and his fellow slaves had taken refuge there and cut them down to make rope ladders. Several surviving works written over the 200 years preceding the AD 79 eruption describe the mountain as having had a volcanic nature, although Pliny the Elder did not depict the mountain in this way in his Naturalis

Historia. The Greek historian Strabo (ca 63 BC–AD 24) described the mountain as having a predominantly flat, barren summit covered with sooty, ash-coloured rocks and suggested that it might once have had "craters of fire". He also perceptively suggested that the fertility of the surrounding slopes may be due to volcanic activity, as at Mount Etna. The architect Vitruvius reported that fires had once existed abundantly below the peak and that it had spouted fire onto the surrounding fields. He went on to describe Pompeiian pumice as having been burnt from another species of stone. Diodorus Siculus (c.a. 90 BC–c.a. 30 BC), another Greek writer, wrote that the Campanian plain was called fiery (Phlegrean) because of the peak, Vesuvius, which had spouted flames like Etna and showed signs of the fire that had burnt in ancient history. However, by 79 AD, Vesuvius was no longer recognized as a volcano. The 79 AD eruption was preceded by a powerful earthquake 17 years before on February 5, 62 AD, which caused widespread destruction around the Bay of Naples, and particularly to Pompeii. Some of the damage had still not been repaired when the volcano erupted. The deaths of 600 sheep from "tainted air" in the vicinity of Pompeii reported by Seneca the Younger, comparable to similar deaths of sheep in Iceland from pools of volcanic carbon dioxide, leads to speculation that the earthquake of 62 AD was related to new activity by Mount Vesuvius. Another smaller earthquake took place 2 years later. It was recorded by Suetonius in his biography of Nero, and by Tacitus in Annales because it took place while Nero was in Naples performing for the first time in a public theatre. Suetonius recorded that the emperor continued singing through the earthquake until he had finished his song, while Tacitus wrote that the theatre collapsed shortly after being evacuated. The Romans grew accustomed to minor earth tremors in the region; Pliny the Younger wrote that they "were not particularly alarming because they are frequent in Campania". Small earthquakes started taking place, with increasing frequency, over the four days prior to the eruption, but the warnings were not recognized. The year of the eruption as 79 AD has never been seriously questioned. It is determined by the well-known events of the reign of Titus. Vespasian died that year. When Titus visited Pompeii to give orders for the relief of the displaced population, he was the sole ruler. In the year after the eruption, 80 AD, he faced another disaster, a great fire at Rome. The time of year was first ‘translated’ as August 24th and this was accepted until 1797 when archaeological evidence began to suggest a later time of year, and the discussion has increased in recent years. The type of clothing worn, the fruits, vegetables and olives for sale, and sealed wine jars all point to a date nearer the end of October or even in November. A commemorative coin has been found in the purse of a woman buried in the ash which should have been minted at the end of September, so dates of October 25th or November 23rd have been suggested. The eruption lasted for two days. The morning of the first day was perceived as normal by the only eyewitness to leave a surviving document. Pliny the Younger was staying at Misenum, on the other side of the Bay of Naples about 19 miles from the volcano, which may have prevented him from noticing the early signs of the eruption. He was not to have any opportunity, during the next two days, to talk to people who had witnessed the eruption from Pompeii or Herculaneum (indeed he never mentions Pompeii in his letter), so he would not have noticed early, smaller fissures and releases of ash and smoke on the mountain, if such had occurred earlier in the morning. Around 1:00 p.m., Mount Vesuvius violently exploded, throwing up a high-altitude column from which ash began to fall, blanketing the area. Rescues and escapes occurred during this time. At some time in the night or early the next day, pyroclastic flows in the close vicinity of the volcano began. Lights seen on the mountain were interpreted as fires. People as far away as Misenum fled for their lives. The flows were rapid-moving, dense, and very hot, knocking down wholly or partly all structures in their path, incinerating or suffocating all population remaining there and altering the landscape, including the coastline. These were accompanied by additional light tremors and a mild tsunami in the Bay of Naples. By evening of the second day the eruption was over, leaving only haze in the atmosphere through which the sun shone weakly. Of the eruption, Pliny the Younger wrote: Broad sheets of flame were lighting up many parts of Vesuvius; their light and brightness were the more vivid for the darkness of the night... it was daylight now elsewhere in the world, but there the darkness was darker and thicker than any night. With his uncle, they saw an extraordinarily dense cloud rising rapidly above the mountain: I cannot give you a more exact description of its appearance than by comparing to a pine tree; for it shot up to a great height in the form of a tall trunk, which spread out at the top as though into branches. [...]

Occasionally it was brighter, occasionally darker and spotted, as it was either more or less filled with earth and cinders. This deadly cloud of volcanic gas, stones, and ash rose to a height of 21 miles, ejecting molten rock and pulverized pumice at the rate of 1.5 million tons per second, ultimately releasing a hundred thousand times the thermal energy of the Hiroshima bombing. Pliny's uncle Pliny the Elder was in command of the Roman fleet at Misenum, and had meanwhile decided to investigate the phenomenon at close hand in a light vessel. As the ship was preparing to leave, a messenger came from his friend Rectina (wife of Tascius) living on the coast near the foot of the volcano, explaining that her party could only get away by sea and asking for rescue - how the messenger escaped remains unexplained. Suddenly grasping the full significance of events, Pliny ordered the immediate launching of the fleet galleys to the evacuation of the coast and he continued in his light ship to the rescue of Rectina's party. His nephew attempted to resume a normal life, continuing to study, and bathing, but that night a tremor awoke him and his mother, prompting them to abandon the house for the courtyard. At another tremor near dawn the population abandoned the village. After still a third "the sea seemed to roll back upon itself, and to be driven from its banks", which is evidence for a tsunami. There is, however, no evidence of extensive damage from wave action. The early light was obscured by a black cloud through which shone flashes, which Pliny likens to sheet lightning, but more extensive. The cloud obscured Point Misenum near at hand and the island of Capraia (Capri) across the bay. Fearing for their lives the population began to call to each other and move back from the coast along the road. Pliny's mother requested him to abandon her and save his own life, as she was too old and fat to go further, but seizing her hand he led her away as best he could. A rain of ash fell. Pliny found it necessary to shake off the ash periodically to avoid being buried. Later that same day the ash stopped falling and the sun shone weakly through the cloud, encouraging Pliny and his mother to return to their home and wait for news of Pliny the Elder. The letter compares the ash to a blanket of snow. Evidently the earthquake and tsunami damage at that location were not severe enough to prevent continued use of the home. Meanwhile Pliny the Elder set off across the bay but in the shallows on the other side encountered thick showers of hot cinders, lumps of pumice, and pieces of rock. Advised by the helmsman to turn back he stated "Fortune favours the brave" and ordered him to continue on to Stabiae (just under 3 miles from Pompeii), where Pomponianus was. (It is not clear whether he was abandoning the effort to reach Rectina's villa or believed Pomponianus was a member of Rectina's party, but Pliny does not mention her again.) Pomponianus had already loaded a ship with possessions and was preparing to leave, but the same onshore wind that brought Pliny's ship to the location had prevented anyone from leaving. Pliny and his party saw flames coming from several parts of the mountain, which they attributed to burning villages. After staying overnight, the party was driven from the building by an accumulation of material which threatened to block all egress. They woke Pliny, who had been napping and emitting loud snoring, and elected to take to the fields with pillows tied to their heads to protect them from rockfall. They approached the beach again but the wind had not changed and Pliny sat down on a sail that had been spread out for him and could not rise, even with assistance, when his friends left, escaping inland. It is most likely that he had collapsed and died, which is why his friends abandoned him, although Suetonius offers an alternative story of his ordering a slave to kill him to avoid the pain of incineration. How the slave would have escaped to tell the tale remains a mystery and there is no mention of such an event in his nephew's letters. In the first letter to Tacitus his nephew suggested that his death was due to the reaction of his weak lungs to a cloud of poisonous, sulphurous gas that wafted over the group. However, Stabiae was 10 miles from the vent (roughly where the modern town of Castellammare di Stabia is situated) and his companions were apparently unaffected by the fumes, so it is more likely that the corpulent Pliny died from some other cause, such as a stroke, heart attack or possibly an asthmatic attack. His body was found with no apparent injuries on the next day, after dispersal of the plume. Along with Pliny the Elder, the only other noble casualties of the eruption to be known by name were Agrippa (a son of the Jewish princess Drusilla and the procurator Antonius Felix) and his wife. The remains of about 1,500 people have been found at Pompeii and Herculaneum, but the overall death toll is still unknown, as is the percentage of the dead to the total number of people at risk.

38% of those found at Pompeii were found in the ash fall deposits, the majority inside buildings. These are thought to have been killed mainly by roof collapses, with the smaller number of victims found outside buildings probably killed by falling roof slates or by larger rocks thrown out by the volcano. The remaining 62% of remains found at Pompeii were in the pyroclastic surge deposits, and thus were probably killed by them. In 2010, studies indicated that during the fourth pyroclastic surge – the first surge to reach Pompeii – temperatures reached 300 °C (572 °F). Volcanologist Giuseppe Mastrolorenzo, who led the study noted that "(It was) enough to kill hundreds of people in a fraction of a second". In reference as to why the bodies were frozen in suspended action, "The contorted postures are not the effects of a long agony, but of the cadaveric spasm, a consequence of heat shock on corpses." Herculaneum, which was much closer to the crater, was saved from tephra falls by the wind direction, but was buried under 75 feet of material deposited by pyroclastic surges. It is

likely that most, or all, of the known victims in this town were killed by the surges, particularly given evidence of high temperatures found on the skeletons of the victims found in the arched vaults, and the existence of carbonised wood in many of the buildings. These people were all caught on the former seashore by the first surge and died of thermal shock but not of carbonization, although some were partly carbonized by later and hotter surges. The arched vaults were most likely boathouses, as the crossbeams in the overhead were probably for the suspension of boats. No boats have been found, indicating they may have been used for the earlier escape of some of the population. The rest were concentrated in the chambers at a density of as high as 3 people per m2. As only a little under 100 yards of the coast have been excavated, the casualties waiting to be excavated may well be as high as the thousands.