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| {{Mtnbox start norange|Name=Mount Vesuvius|Photo=Vesuvius_from_Pompeii.jpg|Caption=<small>Mount Vesuvius as seen from ], which was destroyed in the eruption of AD ].</small>| | |||
| elevation=1281| | |||
| Elevation=1,281 m (4,202 ft) as of ]|Location=]}} | |||
| {{Mtnbox coor dm|40|49|N|14|26|E|type:mountain_region:IT}} | |||
| {{Mtnbox volcano|Type=]|Age=Oldest 25,000 yr|Last eruption=]}} | |||
| {{Mtnbox climb|First ascent= |Easiest route=]}} | |||
| {{Mtnbox finish}} | |||
| :''This article is about the ] in ]. For other uses, see ].'' | |||
| '''Mount Vesuvius''' (]: ''Monte Vesuvio'') (also '''Somma-Vesuvius''' or '''Somma-Vesuvio''') is a ] east of ], ], located at {{coor dm|40|49|N|14|26|E|}}. It is the only volcano on the ]an mainland to have erupted within the last hundred years, although it is not currently erupting. The only other two such ] are located on islands. | |||
| Vesuvius is situated on the coast of the ], about nine kilometres (six miles) to the east of the city and a short distance inland from the shore. It forms a conspicuous feature in the beautiful landscape presented by that bay, when viewed from the sea, with the city in the foreground. The mountain is notorious for its destruction of the ] cities of ] and ] in AD ]. It has erupted many times since and is today regarded as one of the most dangerous volcanoes in the world because of the population of three million people now living close to it coupled with its tendency towards explosive eruptions. | |||
| ==Origin of the name== | |||
| Mount Vesuvius was regarded by the Greeks and Romans as being sacred to the hero and demigod ]/], and the town of ], built at its base, was named after him. The mountain is also named after Hercules in a less direct manner: he was the son of the god ] and ] of ]. Zeus was also known as ''Ves'' ({{polytonic|Ὓης}}) in his aspect as the god of rains and dews. Hercules was thus alternatively known as ''Vesouvios'' ({{polytonic|Ὓσου υἱός}}), "Son of Ves." This name was corrupted into "Vesuvius." | |||
| According to other sources, Vesuvius came from the Oscan word ''fesf'' which means "smoke." | |||
| There is a theory that the name "Vesuvius" is derived from the ] ] ''ves-'' = "]". | |||
| ==Physical aspects== | |||
| ] in the background]] | |||
| Vesuvius is a distinctive "humpbacked" mountain, consisting of a large cone (''Gran Cono'') partially encircled by the steep rim of a ] ] caused by the collapse of an earlier, and originally much higher structure called Monte Somma. For this reason, the volcano is also called '''Somma-Vesuvius''' or '''Somma-Vesuvio'''. | |||
| The caldera started forming during an eruption around 17000 (or 18,300) years ago , and was enlarged by later paroxysmal eruptions ending in the one of 79 AD. This structure has given its name to the term somma volcano, which describes any volcano with a summit caldera surrounding a newer cone . | |||
| The height of the main cone has been constantly modified by eruptions but presently stands at 1,281m (4,202ft). Monte Somma is 1,149m (3,770ft) high, separated from the main cone by the valley of Atrio di Cavallo, which is some 3 miles (5 km) long. The slopes of the mountain are scarred by lava flows but are heavily vegetated, with scrub at higher altitudes and ]s lower down. It is still regarded as an active volcano although its activity currently is limited to little more than steam from vents at the bottom of the crater. The eruption of Vesuvius raised the ground by 1.7 ct.Vesuvius is a ] at the ] where the ] is being ] beneath the ]. Its ] is composed of viscous ]. Layers of lava, ]e, ashes, and ] make up the mountain. | |||
| ==Eruptions== | |||
| Vesuvius has erupted repeatedly in recorded history, most famously in ] and subsequently in ], ], in ], six times in the ], eight times in the ] (notably in ]), and in ], ], and ]. There has been no eruption since then. The eruptions vary greatly in severity but are characterised by explosive outbursts of the kind dubbed ] after the Roman writer who observed the AD 79 eruption. On occasion, the eruptions have been so large that the whole of southern Europe has been blanketed by ashes; in 472 and 1631, Vesuvian ashes fell on ] (now known as ]), over 1,000 miles away. The volcano has been quiescent since 1944. | |||
| ===Before AD 79=== | |||
| Although the area has been subject to volcanic activity for at least 400,000 years, the original Somma mountain was formed in a series of lava eruptions between 25,000 and 19,000 years ago. The style the eruptions then changed to a sequence of explosive plinian eruptions, of which the 79 AD one was the last: | |||
| * The Basal Pumice (Pomici di Base) eruption, 18,300 years ago, ] 6, was probably the most violent of these eruptions and saw the original formation of the Somma caldera. | |||
| * The Green Pumice (Pomici verdoline) eruption, 16,000 years ago, VEI 5, followed a period in which several lava-producing eruptions had taken place. | |||
| * The Mercato eruption (also known as Pomici Gemelle or Ottaviano), 8,000 years ago, VEI 6, followed a smaller explosive eruption around 11,000 years ago. | |||
| * The Avellino eruption (Pomici di Avellino), 3,800 years ago, VEI 6, followed two smaller explosive eruptions around 5,000 years ago. The Avellino eruption vent was apparently 2 km west of the current crater, and the eruption destroyed several ] settlements.<br>The remarkably well-preserved remains of one were discovered in May ] near ] by Italian ]s, with ]s, ]s, ] and even the ]s of animals and people. The residents had hastily abandoned the village, leaving it to be buried under under ] and ash in much the same way that Pompeii was later preserved. | |||
| The volcano then entered a stage of more frequent, but less violent, eruptions until the most recent plinian eruption which destroyed Pompeii. | |||
| The last of these may have been in ]. There were earthquakes in Italy during that year and the sun was reported as being dimmed by a haze or dry fog. ] wrote of the sky being on fire near Naples and ] mentioned in his epic poem '']'' that Vesuvius had thundered and produced flames worthy of ] in that year, although both authors were writing around 250 years later. ] ] samples of around that period show relatively high acidity, which is assumed to have been caused by atmospheric ]{{ref|VolHumFoot}}. | |||
| The mountain subsequently went through several centuries of quiescence and was described by ] writers as having been covered with ]s and ]s, except at the top which was craggy. Within a large circle of nearly perpendicular cliffs was a flat space large enough for the encampment of the army of the rebel gladiator ] in ]. This area was doubtless a ]. The mountain may have had only one summit at that time, judging by a wall painting found in a Pompeiian house (the ''Casa del Centenario''). | |||
| By the time the Greeks and Romans settled the area, the nature of the mountain had entirely been forgotten. The area was, then as now, densely populated with villages, towns and small cities like Pompeii, and its slopes were covered in vineyards and farms. | |||
| ===Eruption of 79=== | |||
| ]''.]] | |||
| The devastating eruption of ] was preceded by powerful earthquakes in ], which caused widespread destruction around the Bay of Naples. Earth tremors were commonplace in the region. The Romans, however, were entirely ignorant of the link between earthquakes and vulcanism, and grew used to them; the writer ] wrote that they "were not particularly alarming because they are frequent in Campania." | |||
| This complacency proved fatal for many on ], ], when the mountain erupted spectacularly. It was recorded for posterity by the younger Pliny, who observed the eruption and recorded it in two famous letters to the historian ]. He saw an extraordinarily dense and rapidly-rising cloud appearing above the mountain: | |||
| :I cannot give you a more exact description of its figure, than by resembling it to that of a pine tree; for it shot up to a great height in the form of a tall trunk, which spread out at the top into a sort of branches. It appeared sometimes bright, and sometimes dark and spotted, as it was either more or less impregnated with earth and cinders. | |||
| What he had seen was a column of ash, now estimated to have been more than 20 miles (32 km) tall. | |||
| His uncle ] was that day in command of the ] at ], on the far side of the bay, and decided to see for himself what was going on. Taking a ship across the bay, the elder Pliny encountered thick showers of hot cinders, lumps of pumice and pieces of rock, blocking his approach to the port of Retina. He went instead to Stabiae where he landed and took shelter with Pomponianus, a friend, in the town's bath house.<br> | |||
| Pliny and his party saw flames coming from several parts of the mountain (probably a sign of superheated ]s, which would later destroy Pompeii and Herculaneum). After resting for a short time in the bath house, the party had to evacuate it due to the torrential rain of ] (ash, cinders, and/or rock) filling the courtyard leading to the building. Violent earthquakes shook the town, adding to the danger. Pliny, Pomponianus and their companions made their way back towards the beach with pillows tied on their heads to protect them from the rockfall. By this time, there was so much ash in the air that the party could barely see through the murk and needed torches and lanterns to find their way. They made it to the beach but found the water too violently disturbed from the continuous earthquakes for them to escape safely by sea. | |||
| Pliny the Elder collapsed and died, and in the first letter to Tacitus his nephew suggested that this was due to the inhalation of poisonous, sulphurous gases. However, Stabae was 16 km from the vent and his companions were apparently unaffected by the fumes, and so it is more likely that the corpulant Pliny died through a different cause, such as a ] or ]. His body was found two days later with no visible physical injuries. | |||
| The eruption is thought to have lasted about 19 hours, in which time the volcano released about 1 cubic mile (4 cubic kilometres) of ash and rock over a wide area to the south and south-east of the crater. Pompeii, Herculaneum and many other towns around Vesuvius were destroyed, with about 3m (10ft) of tephra falling on Pompeii. Around 2,000 people are believed to have died in the town, the vast majority as the result of suffocation by volcanic ashes and gases. Herculaneum, which was much closer to the crater, was buried under 23m (75ft) of ash deposited by a series of pyroclastic flows and mudflows. After the devastating eruption, scientists found that the ground level had rose 1.7 centimeters. Pompeii and Herculaneum were never rebuilt, although surviving townspeople and probably looters did undertake extensive salvage work after the destructions. The towns' locations were eventually forgotten until their accidental rediscovery in the ]. Vesuvius itself underwent major changes - its slopes were denuded of vegetation and its summit had changed considerably due to the force of the eruption. | |||
| ===Later eruptions=== | |||
| ] (ca. 1774-6)]] | |||
| Since the eruption of ], Vesuvius has erupted around three dozen times. It erupted again in ], during the lifetime of the historian ]. In ], it ejected such a volume of ash that ashfalls were reported as far away as ]. The eruptions of ] were so severe that those inhabiting the slopes of Vesuvius were granted exemption from taxes by ], the ]ic king of Italy. Further eruptions were recorded in ], ], ], ], ] and ] with the first recorded ] flows. The volcano became quiescent at the end of the ] and in the following years it again became covered with gardens and vineyards as of old. Even the inside of the crater was filled with shrubbery. | |||
| Vesuvius entered a new and particularly destructive phase in December ], when a major eruption buried many villages under lava flows, killing around 3,000 people. Torrents of boiling water were also ejected, adding to the devastation. Activity thereafter became almost continuous, with relatively severe eruptions occurring in ], ], ], ], ], ], ], ], ], ], ], ], ], ], ], ], ], ], ], and ]. The eruption of 1906 was particularly destructive, killing over 100 people and ejecting the most lava ever recorded from a Vesuvian eruption. Its last eruption came in March ], destroying the villages of ], Massa di Somma and part of San Giorgio a Cremano as ] continued to rage in Italy. | |||
| The volcano has been quiescent ever since. Over the past few centuries, the quiet stages have varied from 18 months to 7½ years, making the current lull in activity the longest in nearly 500 years. While Vesuvius is not thought likely to erupt in the immediate future, the danger posed by future eruptions is seen as very high in the light of the volcano's tendency towards sudden extremely violent explosions and the very dense human population on and around the mountain. | |||
| ===The future=== | |||
| ] | |||
| Large plinian eruptions which emit ] in quantities of about 1 km³ or more, the most recent of which overwhelmed Pompeii, have happened after periods of inactivity of a few thousand years. ] eruptions producing about 0.1 km³, such as those of 472 and 1631, have been more frequent with a few hundred years between them. Following the 1631 eruption until 1944 every few years saw a comparatively small eruption which emitted 0.001-0.01 km³ of magma. 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 km³ for each year. This gives an extremely approximate figure of 0.06 km³ for an eruption after 60 years of inactivity{{ref|ItalVolFoot}}. | |||
| Magma sitting in an underground ] for many years will start to see higher melting point constituents such as ] crystallising out. The effect is to increase the concentration of dissolved gases (mostly ] and ]) in the remaining liquid magma, making the subsequent eruption more violent{{ref|ItalVolFoot}}. As gas-rich magma approaches the surface during an ], the huge drop in ] caused by the reduction in weight of the overlaying rock (which drops to zero at the surface) causes the gases to come out of solution, the volume of gas increasing explosively from nothing to perhaps many times that of the accompanying magma. Additionally, the removal of the lower melting point material will raise the concentration of ] components such as ]s potentially making the magma more ], adding to the explosive nature of the eruption. | |||
| The emergency plan for an eruption therefore assumes that the worst case will be an eruption of similar size and type to the 1631 one (which was ] 4). In this scenario the slopes of the mountain, extending out to about 7 kilometres (4.3 miles) from the vent, may be exposed to pyroclastic flows sweeping down them, whilst much of the surrounding area could suffer from ]s. Because of prevailing ]s, towns to the south and east of the volcano are most at risk from ash, and it is assumed that ash falls exceeding 100 Kg/m² – at which point people are at risk from collapsing roofs – may extend out as far as ] and ]. Towards Naples, to the north west, this ash fall hazard is assumed to barely extend past the slopes of the volcano {{ref|ItalVolFoot}}. The specific areas actually affected by ash will depend upon the particular circumstances of the eruption . | |||
| The plan assumes between 20 days and two weeks notice of an eruption and foresees the 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 | |||
| ]s, ], ]s and ]es is planned to take about seven days, and the evacuees will mostly be sent to other parts of the country rather than to safe areas in the local ] 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 ], since if it is left too late then many people could be killed, whilst if it is started too early then the precursors of the eruption may turn out to have been a ]. In ], 40,000 people were evacuated from the ] area, another volcanic complex near Naples, but no eruption occurred . | |||
| Ongoing efforts are being made to reduce the population living in the red zone, by demolishing illegally constructed buildings, establishing a national park around the upper flanks of the volcano to prevent the erection of further ]s and by offering financial incentives to people for moving away. The underlying goal is to reduce the time needed to evacuate the area, over the next 20 or 30 years, to two or three days. | |||
| The volcano is closely monitored by the ] in Naples with extensive networks of seismic and gravimetric stations, a combination of a ]-based geodic array and ]-based ] to measure ground movement, and by local ]s and chemical analyses of ]es emitted from ]s. All of this is intended to track magma rising underneath the volcano. So far, no magma has been detected within 10 km of the surface, and so the volcano is at worst only in the very early stages of preparing for an eruption{{ref|ItalVolFoot}}. | |||
| ==Vesuvius Today== | |||
| The area around Vesuvius was offically declared a ] on 5 June 1995. The summit of Vesuvius is open to visitors and there is a small network of paths around the mountain that are maintained by the park authorities on weekends. | |||
| ==External links== | |||
| * by ]. | |||
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| ==References== | |||
| * {{note|VolHumFoot}}{{Book reference | Title=Volcanoes in Human History | Publisher=Princeton University Press | Year=2002 | Author=de Boer, Jelle Zeilinga & Sanders, Donald Theodore| ID=ISBN 0-691-05081-3}} | |||
| * {{note|ItalVolFoot}}{{Book reference | Title=Italian Volcanoes| Publisher=Terra Publishing| Year=2001 | Author=Kilburn, Chris & McGuire, Bill| ID=ISBN 1-903544-04-1}} | |||
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Revision as of 05:59, 25 January 2006
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