Wednesday, Feb 06, 2013
A new fumarole vent has been detected recently in the Campi Flegrei in the hydrothermal field of Pisciarelli. The new vent was seen ejecting hot gas as well as geyser-like fountains of water reaching 4-5 meters of height. This will inevitably trigger headlines in the press about the possibility of a volcanic eruption in the area, however, it should be looked at in a context that such phenomena are a normal part of the behavior of (very) active hydrothermal systems such as the Campi Flegrei have. ... [more]
Monday, Jan 07, 2013
According to a recent report by INGV Naples, the ground deformation of the Campi Flegrei (Phlegraean Fields) near Naples has increased considerably lately. During the last 12 months, the ground in some places near the town of Pozzuoli was uplifted by about 8 cm. ... [more]
Campi Flegrei (Phlegrean Fields) volcanoThe Campi Flegrei ("burning fields") or Phlegrean Fields is a large, 13-km-wide nested caldera located under the western outskirts of the citiy of Naples and under the Gulf of Pozzuoli. It contains many volcanic centers (cinder cones, tuff rings, calderas) that have been active during the past 30-40,000 years. The volcanic field has been the site of some extremely violent eruptions in the past, although the few ones that occurred during historic times were small events. Today, there is no sign of imminent reawakening of activity, although there are abundant signs of the presence of a still active magma chamber in the forms of solfataras, warm springs, gas emissions etc. In particular, the Campi Flegrei is infamous for its frequent episodes of major ground deformation in the form of large-scale up- and downlift of the ground (bradisism, see below).
The earliest known eruptive products are dated 47,000 years before present (BP). The Campi Flegrei caldera formed following two large explosive eruptions, the massive Campanian ignimbrite about 36,000 years BP, and the >40 cu km Neapolitan Yellow Tuff (NYT) about 15,000 years BP. Following eruption of the NYT a large number of eruptions have taken place from widely scattered subaerial and submarine vents. Most activity occurred during three intervals: 15,000-9500, 8600-8200, and 4800-3800 years BP. Two eruptions have occurred in historical time, one in 1158 at Solfatara and the other in 1538 that formed the Monte Nuovo cinder cone.
Episodes of dramatic uplift and subsidence within the caldera have occurred since Roman times. Evidence of this can be seen at many places, e.g. at the submerged ruins of a Roman city offshore the small town of Baia. The most recent episodes of uplift ones took place from 1969-72 and 1982-84, when the inhabitants of the area, Pozzuoli in particular, were witness to and victims of a phenomenon where the earth's surface rose; within a few months it had risen by a total of 3.5 m. This phenomenon is called bradisism (literally a slow movement of the earth's surface, as opposed to fast movement due to an earthquake).
The place which, more than any other, can be considered the evidence over the centuries of Phlegraean bradisim is the macellum (a market of the Roman period, better known as the Temple of Serapide) situated close to the port of Pozzuoli. The remains of this building (which dates back to the end of the first century A.D.) have been very useful in reconstructing the development of bradisism thanks to the holes made by lithodomes (sea molluscs which live in coastal areas on the shore line between high and low tide) on the columns which provide evidence of the variations in ground level as compare to sea level, from the IV century A.D. onwards.
Sources: adapted from GVP, Smithsonian Institution and the website of the Vesuvius Observatory
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