Eos, Vol. 68, No. 16, April 21, 1987 On the Volcanological Evolution of Campi Flegrei PAGES 226-227, 229, 231, 233-234 Lucio hirer Dipartimento di Geofisica e Vulcanologia, Universita di Napoli, Italy Giuseppe Luongo Dipartimento di Geofisica e Vulcanologia, Universita di Napoli, Italy Osservatorio Vesuviano, Ercolano, Italy Roberto Scandone Osservatorio Vesuviano, Ercolano, Italy Introduction Campi Flegrei (Phlegrean Fields) is a Holo- cene caldera located west of the city of Na- ples in an area of regional extension [Finetti and More Hi, 1974; Scandone, 1979]. The erupt- ed products range in composition from K ba- salts to alkali trachyte and phonolite. The complex has been active since at least 47,000 yr B.P. [Capaldi et al, 1985], and it is sur- rounded by three other quaternary volcanic centers: • Ischia Island, where activity ranges be- tween 132,000 yr B.P. to the present; • Procida Island, where products have ages between 40,000 and 14,000 yr B.P.; • Vesuvius, where oldest outcropping products have been dated at 25,000 yr B.P. Activity in Campi Flegrei itself has been dominated by two eruptions that produced Cover. Landsat 4 image of the Campa- nian area of Italy. The island at the left is Ischia, which has had volcanic activity since at least 0.132 m.y. B.P. The last eruption there occurred in 1302. An up- lifted block called Mount Epomeo is visi- ble in the center of the island. The next island to the right is Procida, with volca- nos whose ages range between —42,000- 14,000 yr B.P. Campi Flegrei caldera is in the center of the picture; its last eruption occurred in 1538. The caldera gave signs of unrest, with uplift and seismicity, dur- ing 1970-1972 and 1982-1985. The iso- lated volcano in the right part of the pho- to is Mount Vesuvius, next to the north- ern rim of Somma caldera. The last eruption of Vesuvius was in 1944. The city of Naples is visible between Campi Flegrei and Vesuvius. More than 3 million people live in the immediate surroundings of these volcanos. For more information on the nature and history of volcanic ac- tivity in this region, see "On the Volcano- logical Evolution of Campi Flegrei" by Lu- cio Lirer, Giuseppe Luongo, and Roberto Scandone, p. 226. (Image produced by the National Remote Sensing Centre, Farn- borough, U.K.) 0096-3941/87/6816-226$ 1.00 Copyright 1987 by the American Geophysical Union widespread ash flow deposits: the "Campa- nian Ignimbrite" (CI) at -34,000 yr B.P., and the smaller "Neapolitan Yellow Tuff (NYT) -12,000 yr ago. The area and its eruption products have been intensely studied since the 18th century, and as a consequence, many theories have been postulated about their origin. Breislak [1798] identified the CI and considered it to be the product of mud eruptions from cen- ters scattered across the Campanian plain. Scacchi [1849] at first stated that the CI was erupted from Campi Flegrei; later [Scacchi, 1890], he changed his mind and approached Breislak's view. De Lorenzo [1904] subdivided the activity of Campi Flegrei into three peri- ods, including the CI in the first, the NYT in the second, and the products of recent activi- ty inside the caldera in the third. Zambonini [1919] was the first to interpret the CI as a deposit related to an ash flow mechanism of deposition. Rittman et al. [1950] postulated the existence of a central volcano (the Archifle- greo) that was destroyed by the CI eruption and the following caldera collapse. According to Rittman et al., the subsequent activity pro- duced several other collapses of lesser extent. The Eruptive History of Campi Flegrei With the aid of modern dating techniques a clearer picture has emerged of the absolute ages of the products of Campi Flegrei. The oldest products are the domes of Punta Mar- molite (47,000 yr B.P.) and Cuma (37,000 yr B.P.), which are situated on the border of Campi Flegrei. They were emplaced in a sub- aerial environment. The largest eruption of Campi Flegrei occurred at 34,000 yr B.P. [Di Girolamo, 1968; Barberi et al, 1978]. It pro- duced the CI ash flow deposit, which covered the whole of the Campaniari plain (Figure 1). This deposit has been identified in the east- ern Mediterranean as the "Y-5 layer" [Thunell et al, 1979]. The inferred volume of the ash flow and of the coignimbrite ash fall deposit is 80 km 3 of dense rock equivalent (DRE) [Thunell et al, 1979]. The recent discovery of an ash layer correlated with the CI as far as the Soviet Union [Mlekestsev et al, 1984] sug- gests that the volume of the CI may have been underestimated. Di Girolamo [1970] rec-