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| Mythology | |
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Vesuvius has a long historic and literary tradition. It was considered a divinity of the Genius type at the time of the eruption of 79 AD: it appears under the inscribed name Vesuvius as a serpent in the decorative frescos of many lararia, or household shrines, surviving from Pompeii. An inscription from Capua[2] to IOVI VESVVIO indicates that he was worshipped as a power of Jupiter; that is, Jupiter Vesuvius.[3]
The historian Diodorus Siculus relates a tradition that Hercules, in the performance of his labors, 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."[4] 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. The facts behind the tradition, if any, 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.[5] Whether Hercules was ever considered some sort of patron of the volcano itself is debatable.[citation needed]
Tags:Pompeii,Type,Volcano,Herculaneum,Frescos,Capua,Diodorus Siculus,Hercules,Cumae,Epigram,Martial,Venus,Fresco, | |
| Origin of the name | |
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Vesuvius was a name of the volcano in frequent use by the authors of the late Roman Republic and the early Roman Empire. Its collateral forms were Vesaevus, Vesevus, Vesbius and Vesvius.[6] Writers in ancient Greek used Οὐεσούιον or Οὐεσούιος. Many scholars since then have offered an etymology. As peoples of varying ethnicity and language occupied Campania in the Roman Iron Age, the etymology depends to a large degree on the presumption of what language was spoken there at the time. Naples was settled by Greeks, as the name Nea-polis, "New City", testifies. The Oscans, a native Italic people, lived in the countryside. The Latins also competed for the occupation of Campania. Etruscan settlements were in the vicinity. Other peoples of unknown provenience are said to have been there at some time by various ancient authors.
On the presumption that the language is Greek, Vesuvius might be a Latinization of the negative οὔ (ve) prefixed to a root from or related to the Greek word σβέννυμι = "I quench", in the sense of "unquenchable".[6][7] In another derivation it might be from ἕω "hurl" and βίη "violence", "hurling violence", *vesbia, taking advantage of the collateral form.[8]
Some other theories about its origin are:
From an Indo-European root, *eus- < *ewes- < *(a)wes-, "shine" sense "the one who lightens", through Latin or Oscan.[9]
From an Indo-European root *wes = "hearth" (compare e.g. Vesta)
Tags:Naples,European,Roman,Roman Republic,Roman Empire,Collateral Forms,Etymology,Campania,Roman Iron Age,Oscans,Italic,Latins,Indo-european,Latin,Oscan,Hearth,Vesta,Greek, | |
| Physical appearance | |
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A view of the crater wall of Vesuvius, with the city of Torre del Greco in the background
Vesuvius is a distinctive "humpbacked" mountain, 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 Monte Somma.[10] The Gran Cono was produced during the eruption of AD 79. For this reason, the volcano is also called Somma-Vesuvius or Somma-Vesuvio.
The caldera started forming during an eruption around 17,000[11][12] (or 18,300)[13] years ago and was enlarged by later paroxysmal eruptions[14] ending in the one of AD 79. This structure has given its name to the term "somma volcano", which describes any volcano with a summit caldera surrounding a newer cone.[15]
The height of the main cone has been constantly changed by eruptions but is 1,281 m (4,202 ft) at present. Monte Somma is 1,149 m (3,770 ft) 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 and forest at higher altitudes and vineyards lower down. Vesuvius is still regarded as an active volcano, although its current activity produces little more than steam from vents at the bottom of the crater. Vesuvius is a stratovolcano at the convergent boundary where the African Plate is being subducted beneath the Eurasian Plate. Layers of lava, scoria, volcanic ash, and pumice make up the mountain. Their mineralogy is variable, but generally silica-undersaturated and rich in potassium, with phonolite produced in the more explosive eruptions.[16]
Tags:Ad 79,Somma Volcano,Stratovolcano,Cone,Caldera,Convergent Boundary,African Plate,Subducted,Eurasian Plate,Scoria,Volcanic Ash,Pumice,Silica,Potassium,Phonolite,African,Eurasian, | |
| Formation | |
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A view of Somma-Vesuvius, from a convent on the Sorrento Peninsula
Vesuvius was formed as a result of the collision of two tectonic plates, the African and the Eurasian. The former was pushed beneath the latter, deeper into the earth. As the water-saturated sediments of the oceanic African plate were pushed to hotter depths in the earth, the water boiled off and caused the melting point of the upper mantle to drop enough to create partial melting of the rocks. Because magma is less dense than the solid rock around it, it was pushed upward. Finding a weak place at the Earth's surface it broke through, producing the volcano.
The volcano is one of several which form the Campanian volcanic arc. Others include Campi Flegrei, a large caldera a few kilometres to the north west, Mount Epomeo, 20 kilometres (12 mi) 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 produced by the subduction process described above, 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.
Tags:Italy,Arc,Campanian Volcanic Arc,Tectonic Plates,Campi Flegrei,Ischia,Subduction,Monte Amiata, | |
| Eruptions | |
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An aerial photo of Vesuvius
Mount Vesuvius has erupted many times. The famous eruption in 79 AD 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. Since 79 AD, the volcano has also erupted repeatedly, in 172, 203, 222, possibly 303, 379, 472, 512, 536, 685, 787, around 860, around 900, 968, 991, 999, 1006, 1037, 1049, around 1073, 1139, 1150, and there may have been eruptions in 1270, 1347, and 1500.[14] The volcano erupted again in 1631, six times in the 18th century, eight times in the 19th century (notably in 1872), and in 1906, 1929, and 1944. There has been no eruption since 1944, and none of the post-79 eruptions were as large or destructive as the Pompeian one.
The eruptions vary greatly in severity but are characterized by explosive outbursts of the kind dubbed Plinian after Pliny the Younger, a Roman writer who published a detailed description of the AD 79 eruption, including his uncle's death.[17] On occasion, eruptions from Vesuvius have been so large that the whole of southern Europe has been blanketed by ash; in 472 and 1631, Vesuvian ash fell on Constantinople (Istanbul), over 1,200 kilometres (750 mi) away. A few times since 1944, landslides in the crater have raised clouds of ash dust, raising false alarms of an eruption.
Tags:Plinian,Avellino Eruption,Pliny The Younger, | |
| Before AD 79 | |
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Scientific knowledge of the geologic history of Vesuvius comes from core samples taken from a 2,000 m (6,600 ft) plus bore hole on the flanks of the volcano, extending into Mesozoic rock. Cores were dated by potassium-argon and argon-argon dating.[18] The mountain started forming 25,000 years ago. Although the area has been subject to volcanic activity for at least 400,000 years, the lowest layer of eruption material from the Somma mountain lies on top of the 34,000 year-old Campanian Ignimbrite produced by the Campi Flegrei complex, and was the product of the Codola plinian eruption 25,000 years ago.[10]
It was then built up by a series of lava flows, with some smaller explosive eruptions interspersed between them. However, the style of eruption changed around 19,000 years ago to a sequence of large explosive plinian eruptions, of which the AD 79 one was the last. The eruptions are named after the tephra deposits produced by them, which in turn are named after the location where the deposits were first identified:[19]
The Basal Pumice (Pomici di Base) eruption, 18,300 years ago, VEI 6, saw the original formation of the Somma caldera. The eruption was followed by a period of much less violent, lava producing eruptions.[13]
The Green Pumice (Pomici Verdoline) eruption, 16,000 years ago, VEI 5.[10]
The Mercato eruption (Pomici di Mercato) — also known as Pomici Gemelle or Pomici Ottaviano — 8000 years ago, VEI 6, followed a smaller explosive eruption around 11,000 years ago (called the Lagno Amendolare eruption).[10]
The Avellino eruption (Pomici di Avellino), 3800 years ago, VEI 5, 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 Bronze Age settlements of the Apennine culture. Several carbon dates on wood and bone offer a range of possible dates of about 500 years in the mid-2nd millennium BC. In May 2001 near Nola Italian archaeologists using the technique of filling every cavity with plaster or substitute compound recovered some 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 was later preserved.[20][21] Pyroclastic surge deposits were distributed to the northwest of the vent, travelling as far as 15 km (9.3 mi) from it, and lie up to 3 m (9.8 ft) deep in the area now occupied by Naples.[22]
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 217 BC.[14] There were earthquakes in Italy during that year and the sun was reported as being dimmed by a haze or dry fog. Plutarch wrote of the sky being on fire near Naples and Silius Italicus mentioned in his epic poem Punica[23] that Vesuvius had thundered and produced flames worthy of Mount Etna in that year, although both authors were writing around 250 years later. Greenland ice core samples of around that period show relatively high acidity, which is assumed to have been caused by atmospheric hydrogen sulfide.[24]
Fresco of Bacchus and Agathodaemon with Mount Vesuvius, as seen in Pompeii's House of the Centenary.
The mountain was then quiet for hundreds of years and was described by Roman writers as having been covered with gardens and vineyards, 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 Spartacus in 73 BC. This area was doubtless a crater. The mountain may have had only one summit at that time, judging by a wall painting, "Bacchus and Vesuvius", found in a Pompeiian house, the House of the Centenary (Casa del Centenario).
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:[25]
The Greek historian Strabo (ca 63 BC–AD 24) described the mountain in Book V, Chapter 4 of his Geographica[26] 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.
In Book II of De Architectura,[27] the architect Vitruvius (ca 80-70 BC -?) reported that fires had once existed abundantly below the mountain 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 (ca 90 BC–ca 30 BC), another Greek writer, wrote in Book IV of his Bibliotheca Historica that the Campanian plain was called fiery (Phlegrean) because of the mountain, Vesuvius, which had spouted flame like Etna and showed signs of the fire that had burnt in ancient history.[28]
Tags:Italian,Etna, | |
| Precursors and foreshocks | |
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Computer-generated imagery of the eruption of Vesuvius in BBC/Discovery Channel's co-production Pompeii
The AD 79 eruption was preceded by a powerful earthquake seventeen years beforehand on 5 February, AD 62, which caused widespread destruction around the Bay of Naples, and particularly to Pompeii.[29] Some of the damage had still not been repaired when the volcano erupted.[30] The deaths of 600 sheep from "tainted air" in the vicinity of Pompeii reported by Seneca the Younger leads Haraldur Sigurdsson to compare them to similar deaths of sheep in Iceland from pools of volcanic carbon dioxide and to speculate that the earthquake of 62 was related to new activity by Vesuvius.[31]
Another smaller earthquake took place in 64 AD; it was recorded by Suetonius in his biography of Nero,[32] and by Tacitus in Annales because it took place while Nero was in Naples performing for the first time in a public theatre.[33] 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; the writer Pliny the Younger even wrote that they "were not particularly alarming because they are frequent in Campania". Small earthquakes started taking place on 20 August, 79[30] becoming more frequent over the next four days, but the warnings were not recognised.[34]
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| Nature of the eruption | |
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Vesuvius erupting. Painting by Norwegian painter J.C. Dahl, 1826
Reconstructions of the eruption and its effects vary considerably in the details but have the same overall features. The eruption lasted two days. The morning of the first day was perceived as normal by the only eyewitness to leave a surviving document, Pliny the Younger. In the middle of the day an explosion threw 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 were seen on the mountain 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. Those are the historical facts as far as they can be discovered. Many studies[citation needed] both scientific and speculative have attempted to fill in additional detail, most claiming to be based "on new evidence." Much of this evidence is scientifically cogent[citation needed], but the authors of the studies present different views. How to reconcile them remains an on-going concern.[citation needed]
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| Stratigraphic studies | |
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According to a stratigraphic study (a study of the layers of ash) by Sigurdsson, Cashdollar and Sparks, published in 1982, and now a standard reference, the eruption of Vesuvius of 79 AD unfolded in two phases:[35] a Plinian eruption that lasted eighteen to twenty hours and produced a rain of pumice southward of the cone that built up to depths of 2.8 metres (9 ft 2 in) at Pompeii, followed by a pyroclastic flow or nuée ardente in the second, Peléan phase that reached as far as Misenum but was concentrated to the west and northwest. Two pyroclastic flows engulfed Pompeii, burning and asphyxiating the stragglers who had remained behind. Oplontis and Herculaneum received the brunt of the flows and were buried in fine ash and pyroclastic deposits.
In an article published in 2002 Sigurdsson and Casey elaborate on the stratigraphic evidence based on excavations and surveys up until then. In this interpretation, the quasi-initial explosion (not quite initial) produced a column of ash and pumice ranging between 15 kilometres (49,000 ft) and 30 kilometres (98,000 ft) high, which, due to northwest winds, rained on Pompeii to the southeast but not on Herculaneum upwind. The eruption is viewed as primarily phreatic; that is, the chief energy supporting the column came from the escape of steam superheated by the magma, created from ground water seeping over time into the deep faults of the region.
Subsequently the cloud collapsed as the gases expanded and lost their capability to support their solid contents, releasing it as a pyroclastic surge, which reached Herculaneum but not Pompeii. Additional explosions reinstituted the column. The eruption alternated between Plinian and Peléan six times. Surges 3 and 4 are believed by the authors to have destroyed Pompeii.[36] Surges are identified in the deposits by dune and cross-bedding formations, which are not produced by fallout.
The authors suggest that the first ash falls are to be interpreted as early-morning, low-volume explosions not seen from Misenum, causing Rectina to send her messenger on a ride of several hours around the Bay of Naples, then passable, providing an answer to the paradox of how the messenger might miraculously appear at Pliny's villa so shortly after a distant eruption that would have prevented him.
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| Magnetic studies | |
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Inside the crater of Vesuvius
A 2006 study by Zanella, Gurioli, Pareschi and Lanza used the magnetic characteristics of over 200 samples of lithic, roof-tile and plaster fragments collected from pyroclastic deposits in and around Pompeii to estimate the equilibrium temperatures of the deposits.[37] The deposits were placed by pyroclastic density currents (PDCs) resulting from the collapses of the Plinian column. The authors argue that fragments over 2–5 cm were not in the current long enough to acquire its temperature, which would have been much higher, and therefore they distinguish between the depositional temperatures, which they estimated, and the emplacement temperatures, which in some cases based on the cooling characteristics of some types and fragment sizes of rocks they believed they also could estimate. Final figures are considered to be those of the rocks in the current just before deposition.[38]
All crustal rock contains some iron or iron compounds, rendering it ferromagnetic, as do Roman roof tiles and plaster. These materials may acquire a residual field from a number of sources. When individual molecules, which are magnetic dipoles, are held in alignment by being bound in a crystalline structure, the small fields reinforce each other to form the rock's residual field.[39] Heating the material adds internal energy to it. At the Curie temperature, the vibration of the molecules is sufficient to disrupt the alignment; the material loses its residual magnetism and assumes whatever magnetic field might be applied to it only for the duration of the application. The authors term this phenomenon unblocking. Residual magnetism is considered to "block out" non-residual fields.
A rock is a mixture of minerals, each with its own Curie temperature; the authors therefore looked for a spectrum of temperatures rather than a single temperature. In the ideal sample, the PDC did not raise the temperature of the fragment beyond the highest blocking temperature. Some constituent material retained the magnetism imposed by the Earth's field when the item was formed. The temperature was raised above the lowest blocking temperature and therefore some minerals on recooling acquired the magnetism of the Earth as it was in 79 AD. The overall field of the sample was the vector sum of the fields of the high-blocking material and the low-blocking material.
This type of sample made possible estimation of the low unblocking temperature. Using special equipment that measured field direction and strength at various temperatures, the experimenters raised the temperature of the sample in increments of 40 °C (104 °F) from 100 °C (212 °F) until it reached the low unblocking temperature.[40] Deprived of one of its components, the overall field changed direction. A plot of direction at each increment identified the increment at which the sample's resultant magnetism had formed.[41] That was considered to be the equilibrium temperature of the deposit. Considering the data for all the deposits of the surge arrived at a surge deposit estimate. The authors discovered that the city, Pompeii, was a relatively cool spot within a much hotter field, which they attributed to interaction of the surge with the "fabric" of the city.[42]
The investigators reconstruct the sequence of volcanic events as follows. On the first day of the eruption a fall of white pumice containing clastic fragments of up to 3 centimetres (1.2 in) fell for several hours.[43] It heated the roof tiles to 120 °C (248 °F) to 140 °C (284 °F).[44] This period would have been the last opportunity to escape. Subsequently a second column deposited a grey pumice with clastics up to 10 cm (3.9 in), temperature unsampled, but presumed to be higher, for 18 hours. These two falls were the Plinian phase. The collapse of the edges of these clouds generated the first dilute PDCs, which must have been devastating to Herculaneum, but did not enter Pompeii.
Early in the morning of the second day the grey cloud began to collapse to a greater degree. Two major surges struck and destroyed Pompeii. Herculaneum and all its Tags: | |
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