HR: 14:15h
AN: V23B-03    [Abstracts]
TI: Controls on Recent Unrest at Campi Flegrei Caldera, Southern Italy
AU: * Woo, J
EM: j.woo@ucl.ac.uk
AF: Benfield Hazard Research Centre, Department of Earth Sciences University College London, London, WC1E 6BT United Kingdom
AU: Bellucci, F
EM: francebel@tin.it
AF: Dipartimento di Geofisica e Vulcanologia, University of Napoli 'Federico II', Naples, Italy
AU: Kilburn, C R
EM: c.kilburn@ucl.ac.uk
AF: Benfield Hazard Research Centre, Department of Earth Sciences University College London, London, WC1E 6BT United Kingdom
AU: Rolandi, G
EM: giuseppe.rolandi@unina.it
AF: Dipartimento di Geofisica e Vulcanologia, University of Napoli 'Federico II', Naples, Italy
AB: Campi Flegrei, in Southern Italy, is an active caldera that has shown signs of unrest since 1969. Because the caldera has a population of 400,000 people, it is especially important to understand the mechanisms driving the unrest and their implication for the probability of a future eruption. Since its last ignimbrite eruption 12,000 years ago (which produced the Neapolitan Yellow Tuff), volcanic activity in Campi Flegrei has consisted of numerous eruptions (volumes ~0.1 km3 or less) surrounding the inferred caldera rim. For at least the last 3,700 years, the caldera has been subsiding at mean rates of 14-17 mm per year, punctuated by two known periods of mean uplift (1430-1538 and 1969-Present). The first period produced a net uplift of about 30 m at the port of Pozzuoli and was followed in 1538 by the eruption of Monte Nuovo (20 million m3) some 4 km to the west. The second period has to date consisted of two episodes of uplift (in 1969-72 and 1982-84), each raising Pozzuoli by about 2 m. Studies of the second period have attributed uplift either to magmatic intrusion or to the expansion of water in heated aquifers. These interpretations assumed a stationary reference condition. It is here proposed that the reference condition in fact corresponds to subsidence at about 17 mm per year. Slower subsidence then reflects the difference between background subsidence and actual intrusion of magma. The revised interpretation suggests a two-component source for the recent episodes of uplift: (1) intrusion of two batches of magma of ~0.1 km3 that have produced a permanent uplift of about 2.8 m, and (2) the expansion and later dissipation of heated water, which produced a temporary uplift of about 0.7 m that has since disappeared. The similar volumes of recent intrusions and post-NYT eruptions further suggest that Campi Flegrei is fed by discrete batches of magma. The caldera today may thus be underlain by a collection of modest magma bodies rather than a single, large reservoir.
DE: 7280 Volcano seismology (8419)
DE: 8414 Eruption mechanisms
DE: 8419 Eruption monitoring (7280)
DE: 8424 Hydrothermal systems (8135)
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly