The Campi Flegrei Caldera GIS Database

The Caldera.  The Campi Flegrei are a volcanic field where numerous, different eruptive centres have been active over the last 39,000 years. In its geological history there have been two major eruptions: the eruption of Campanian Ignimbrite (39,000 years ago) and Neapolitan Yellow Tuff (of 15,000 years ago). These eruptions are connected to two instances of subsidence, which together created a complex nested caldera; this is a clearly evident structure of the Phlegraean Volcanic District. This latter includes the Phlegraean Fields, the city of Naples, the volcanic islands of Ischia and Procida, and the north-west section of the bay of Naples.

Volcanic Unrest. From 1969-72 and 1982-84 the inhabitants of the Phlegraean area, and Pozzuoli in particular, were witness to and victims of a phenomenon where the earth's surface rose; whitin a few months it had risen by a total of 3.5 metres. This phenomenon is called bradisism (literally a slow movement of the earth's surface, as opposed to fast movement due to an earthqake). 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 recostructing 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. From 1985, the caldera floor has been subsiding at a average rate of about 1.5 cm/yr.

Monitoring. The Osservatorio Vesuviano started an intensive program of geodetic surveillance in the late 1960s. The monitoring system of the Vesuvius Observatory includes seismic, geodetic and geochemical networks. The goal of this effort is to provide residents and civil authorities in the area reliable information on the nature of the potential hazards posed by this unrest and timely warning of an impending volcanic eruption, should it develop. Most, perhaps all, volcanic eruptions are preceded and accompanied by geophysical and geochemical changes in the volcanic system. Common precursory indicators of volcanic activity include increased seismicity, ground deformation, and variations in the nature and rate of gas emissions.