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Monday, December 18, 2006

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Vesuvius, Italy

Mount Vesuvius (Italian: Monte Vesuvio, Latin: Mons Vesuvius) is a volcano east of Naples, Italy. It is the only volcano on the European mainland to have erupted within the last hundred years, although it is not currently erupting. The only other two such volcanoes in Italy (Etna and Stromboli) are located on islands.
Vesuvius is on the coast of the Bay of Naples, about nine kilometres (six miles) east of Naples and a short distance from the shore. It is conspicuous in the beautiful landscape presented by the Bay of Naples, when seen from the sea, with Naples in the foreground. Vesuvius is best known for its eruption in A.D. 79 that led to the destruction of the Roman cities of Pompeii and Herculaneum. 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 3,000,000 people now living close to it and its tendency towards explosive eruptions.
Mount Vesuvius was regarded by the Greeks and Romans as being sacred to the hero and demigod Hercules/Heracles, and the town of Herculaneum, built at its base, was named after him.
Vesuvius, Space Shuttle photograph. Compare to the map below. The Somma Rim, a caldera-like structure formed by the collapse of a stratovolcano about 17,000 years ago, is visible as an arcuate dark area to the right and above Vesuvius. The Bay of Naples is on the lower left. The small hook of land near the right margin of the photo is part of a caldera of the Phlegraean Fields volcanic region. The caldera formed about 34,000 years ago. From 1983-1985 an area of 31 square miles (80 square kilometers) was uplifted, in places up to 5.9 feet (1.8 meters), damaging homes, the harbor, and the tourist industry. Ultimately 36,000 people were relocated.

Vesuvius is a complex volcano. According to Peter Francis (p. 351) a complex volcano is "an extensive assemblage of spatially, temporally, and genetically related major and minor [volcanic] centers with their associated lava flows and pyroclastic flows." Vesuvius has a long history. The oldest dated rock from the volcano is about 300,000 years old. It was collected from a well drilled near the volcano and was probably part of the Somma volcano. After Somma collapsed about 17,000 years ago, Vesuvius began to form. Vesuvius is a stratovolcano. Vesuvius has erupted many times. The famous eruption in 79 was preceded by numerous others in prehistory, including at least 3 significantly larger ones, the best known being the Avellino eruption around 1800 BC which engulfed several Bronze Age settlements. Since 79, 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.[6] 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 it.
The eruptions vary greatly in severity but are characterized by explosive outbursts of the kind dubbed Plinian after Pliny the Younger, the Roman naturalist who observed the 79 eruption, and whose uncle Pliny the Elder possibly fell victim. 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 Constantinople (Istanbul), over 1,200 km away. A few times since 1944, landslides in the crater raised clouds of ash dust, which caused false alarms of an eruption.

In 5960 B.C. and 3580 B.C., Vesuvius had two eruptions that rate among the largest known in Europe. The area was frequently jolted by large earthquakes. This decorative stonework records the damage caused by an earlier earthquake, perhaps the earthquake of 62 A.D. that preceded the 79 A.D. eruption. Copyrighted photograph of Robert Decker.

The 79 A.D. eruption of Vesuvius was the first volcanic eruption ever to be described in detail. From 18 miles (30 km) west of the volcano, Pliny the Younger, witnessed the eruption and later recorded his observations in two letters. He described the earthquakes before the eruption, the eruption column, air fall, the effects of the eruption on people, pyroclastic flows, and even tsunami. Volcanologists now use the term "plinian" to refer to sustained explosive eruptions which generate high-altitude eruption columns and blanket large areas with ash. It is estimated that at times during the eruption the column of ash was 20 miles (32 km) tall. About 1 cubic mile (4 cubic kilometers) of ash was erupted in about 19 hours. Volcanoes by Peter Francis contains several direct passages from Pliny the Younger and describes the archeology of Pompeii and Herculaneum. Copyrighted photograph of a street in Pompeii by Robert Decker, 1971. Vesuvius is in the background.

About 10 feet (3 m) of tephra fell on Pompeii, burying everything except the roofs of some buildings. The city was abandoned and its location forgotten. In 1595, excavations discovered artifacts at Pompeii and centuries of pillaging followed. Archeological excavations began in the mid-nineteenth century. Now, much of Pompeii has been excavated and it has revealed much about how people lived during that time (and died during the eruption). There are numerous molds of people in their final moments. The mold of a dog is shown in the above photo. The poor animal was chained to a post and struggled for hours before finally succumbing to the ash.

The skeletal remains of a young woman killed by the eruption of Mount Vesuvius in A.D. 79. The skeleton, unearthed from the ruins of Herculaneum in 1982, was named the "Ring Lady" because of the emerald and ruby rings found on the woman's left hand. Two gold bracelets and gold earrings were also found by the woman's side,two pairs of earings that seemed to hold perls in them.

Estimates of the population of Pompeii range from 10,000 to 20,000, whilst Herculaneum is thought to have had a population of about 5,000. It is not known how many people the eruption killed, although around 1,150 remains of bodies have been recovered, or casts made of their impressions in the ash deposits in and around Pompeii. The remains of about 350 bodies have been found at Herculaneum (300 in arched vaults discovered in 1980). However these figures must represent a great underestimation of the total number of deaths over the region affected by the eruption.
38% of the victims 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 of buildings probably being killed by falling roof slates or by larger rocks thrown out by the volcano. This differs from modern experience, since over the last four hundred years only around 4% of victims have been killed by ash falls during explosive eruptions. The remaining 62% of remains found at Pompeii were in the pyroclastic surge deposits, and thus were probably killed by them – probably from a combination of suffocation through ash inhalation and blast and debris thrown around. In contrast to the victims found at Herculaneum, examination of cloth, frescoes and skeletons show that it is unlikely that high temperatures were a significant cause.
Herculaneum, which was much closer to the crater, was saved from tephra falls by the wind direction, but was buried under 23 m (75 ft) of material deposited by pyroclastic surges. It is likely that most, or all, of the 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.
Pompeii and Herculaneum were never rebuilt, although surviving townspeople and probably looters did undertake extensive salvage work after the destructions. The eruption changed the course of the River Sarno and raised the sea beach, so that Pompeii was now neither on the river nor adjacent to the coast.
The towns' locations were eventually forgotten until their accidental rediscovery in the 18th century. Vesuvius itself underwent major changes — its slopes were denuded of vegetation and its summit had changed considerably due to the force of the eruption.

The area around Vesuvius was officially declared a national park 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.

There is access by road to within 200 metres of the summit (measured vertically), but thereafter access is on foot only. There is a spiral walkway around the mountain from the road to the crater.

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