The Phlegraean Fields are a large volcanic area situated to the west of Naples, Italy. It was declared a regional park in 2003. Lying mostly underwater, the area of the caldera consists of 24 craters and volcanic edifices. Hydrothermal activity can be observed at Lucrino, Agnano and the town of Pozzuoli. There are also effusive gaseous manifestations in the Solfatara crater, the mythological home of the Roman god of fire, Vulcan.
This area is monitored by the Vesuvius Observatory.
The area also features bradyseismic phenomena, which are most evident at the Macellum of Pozzuoli (misidentified as a temple of Serapis), as geologists puzzled over bands of boreholes left by marine molluscs on marble columns, showing that the level of the site in relation to sea level had varied.
Three geological phases or periods are recognised and distinguished.
- The First Phlegraean Period. It is thought that the eruption of the Archiflegreo volcano occurred about 39,280 ± 110 years ago, erupting about 200km3 of magma (500km3 bulk volume) to produce the Campanian Ignimbrite eruption. Its Volcanic Explosivity Index (VEI) was 7. "The dating of the Campanian Ignimbrite Eruption (CI) to ~37,000 calendar years B.P. draws attention to the coincidence of this volcanic catastrophe and the suite of, Late Pleistocene biocultural changes that occurred within and outside the Mediterranean region. These included the Middle to Upper Paleolithic cultural transition and the replacement of Neanderthal populations by anatomically modern Homo sapiens, a subject of sustained debate.Neanderthal Apocalypse Documentary film, ZDF Enterprises, 2015. Retrieved 26 January 2016. No less than 150 km3 of magma were extruded in this eruption (the CI eruption), whose signal can be detected in Greenland ice cores. As widespread discontinuities in archaeological sequences are observed at or after this eruption, a significant interference with ongoing human processes in Mediterranean Europe is hypothesized." It is possible that these eruptions drove Neanderthals to extinction and cleared the way for modern humans to thrive in Europe and Asia. The area is characterised by banks of and pipernoid grey tuff at Camaldoli hill, like in the northern and western ridge of Mount Cumae; other referable deep products are those found at Monte di Procida, recognizable in the cliffs of its coast.
- The Second Phlegraean Period. Between 35,000–10,500 years ago, it is characterized by the yellow tuff that is the remains of an immense underwater volcano, with a diameter of ; Pozzuoli is at its center. Approximately 12,000 years ago the last major eruption occurred, forming a smaller caldera inside the main caldera, centered on the town of Pozzuoli. This event produced the Neapolitan yellow tuff, referring to the characteristic yellow rocks there.
- The Third Phlegraean Period. Dated between 8,000 – 500 years ago, it is characterized by white pozzolana, the material that forms the majority of volcanos in the Fields. Broadly speaking, it can be said there was an initial activity to the southwest in the zone of Bacoli and Baiae (10,000–8,000 years ago); an intermediate activity in an area centred between Pozzuoli, Spaccata Mountain and Agnano (8,000–3,900 years ago); and a more recent activity, moved towards the west to form Lake Avernus and Monte Nuovo (New Mountain) (3,800–500 years ago).
- There are volcanic deposit indicating possible eruption, dated by argon at 315,000, 205,000, 157,000 and 18,000 years ago.
More recent history
A fumarole at the Phlegraean Fields; painting by Michael Wutky (1780s)
The caldera, which now is essentially at ground level, is accessible on foot. It contains many fumaroles, from which steam can be seen issuing, and over 150 pools of boiling mud at last count. Several subsidiary cones and tuff craters lie within the caldera. One of these craters is filled by Lake Avernus.
In 1538, an eight-day eruption in the area deposited enough material to create a new hill, Monte Nuovo. It has risen about 2m from ground level since 1970. It is a volcano capable of producing VEI 7 eruptions, as large as that of Tambora in 1815.
At present, the Phlegraean Fields area comprises the Naples districts of Agnano and Fuorigrotta, the area of Pozzuoli, Bacoli, Monte di Procida, Quarto, the Phlegrean Islands .
A 2009 journal article stated that inflation of the caldera centre in the vicinity of Pozzuoli might presage an eruptive event within decades. In 2012 the International Continental Scientific Drilling Program planned to drill 3.5 km (2.2 miles) below the earth's surface near Pompeii intending to monitor the massive molten rock chamber below in order to provide early warning of any eruption. Local scientists are worried that such drilling itself could initiate an eruption or earthquake. In 2010 the Naples city council had prevented the drilling project. Programme scientists said the drilling was no different from industrial drilling in the area. The newly elected mayor allowed the project to go forward. A Reuters article emphasized that the area could produce a "super volcano" that might kill millions.Antonio Denti, "Super volcano", global danger, lurks near Pompeii, Reuters, August 3, 2012.
A recent study from Istituto Nazionale di Geofisica e Vulcanologia describing recent volcanic unrest of Campi Flegrei caldera from January 2012 to June 2013 characterised by rapid ground uplift of about 11cm with a peak rate of about 3cm per month during December 2012 mentions, that in previous years from 1985 to 2011 dynamics of ground uplift has been mostly linked to caldera's hydrothermal system. As study describes, this relation broke down in 2012 and the driving mechanism of the ground uplift changed to periodical emplacement of a magma within a flat, sill-shaped magmatic reservoir in depth cca 3000m, 500m south from port of Pozzuoli.
In December of 2016, activity became so high that an eruption was feared. In May 2017 a new study by UCL and the Vesuvius Observatory and published in Nature Communications revealed that an eruption may be closer than previously thought. The study found that the geographical unrest since the 1950s has a cumulative effect, causing a build-up of energy in the crust and making the volcano more susceptible to eruption.
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Italian wine, both red and white, under the Campi Flegrei DOC appellation comes from this area. Grapes destined for DOC production must be harvested up to a maximum yield of 12 tonnes/hectare for red grape varieties, and 13 tonnes/ha for white grape varieties. The finished wines need to be fermented to a minimum alcohol level of 11.5% for reds and 10.5% for whites. While most Campi Flegrei wines are blends, varietal wines can be made from individual varieties, provided the variety used comprises at least 90% of the blend and the wine is fermented to at least 12% alcohol for reds and 11% for whites.
Red Campi Flegrei is a blend of 50–70% Piedirosso, 10–30% Aglianico and/or Sciascinoso and up to 10% of other local (both red and white) grape varieties. The whites are composed of 50–70% Falanghina, 10–30% Biancolella and/or Coda di Volpe, with up to 30% of other local white grape varieties.
Campi Flegrei has had strategic and cultural importance.
- The area was known to the ancient Greeks, who had a colony nearby at Cumae, the seat of the Cumaean Sibyl.
- The beach of Miliscola, in Bacoli, was the Roman military academy headquarters.
- Lake Avernus was believed to be the entrance to the underworld, and is portrayed as such in the Aeneid of Virgil. During the civil war between Octavian and Antony, Agrippa tried to turn the lake into a military port, the Portus Julius.
- Baiae, now lying underwater, was a fashionable coastal resort and was the site of summer villas of Julius Caesar, Nero, and Hadrian .
- A Flavian Amphitheatre, the third-largest Italian amphitheatre, after the Colosseum and the Capuan Amphitheatre.
- The Via Appia passed through the comune of Quarto, entirely built on an extinguished crater.
- The Cave of Dogs, a famous tourist attraction during the early modern period—is on the eastern side of the Fields.
- Europe's youngest mountain, Monte Nuovo is here. A WWF oasis lies beside the enormous Astroni crater.
- The tombs of Agrippina the Elder and Scipio Africanus are here as well.
- At Baiae, a Bacoli district the most ancient hot spring complex was built for the richest Romans. It included the largest ancient dome in the world before the construction of the Roman Pantheon.
- Astronomical broadcaster and writer Patrick Moore used to cite these Fields as an example of why the impact craters on the Moon must be of volcanic origin, which was thought to be the case until the 1960s.
- A Campanian ignimbrite super-eruption around 40,000 years ago has been hypothesised as having contributed to the demise of the Neanderthal, based on evidence from Mezmaiskaya cave in the Caucasus Mountains of southern Russia.