Renewed ground uplift at Campi Flegrei caldera (Italy): New insight on magmatic processes and forecast
ABSTRACT Campi Flegrei caldera, including the extremely urbanised city of Naples, is the most risky volcanic area in the World. The last eruption in the area (1538) occurred at the end of some decades of ground uplift, superimposed to secular subsidence. During the last four decades, it experienced a huge uplift phase, reaching about 3.5 m in 1985, when a subsidence phase started. Recent geodetic data demonstrate that such a subsidence phase has terminated, and a new uplift episode started in November 2004, with a low but increasing rate leading to about 0.04 m of uplift till the end of October 2006. A new indicator, based on the monitoring of maximum horizontal to vertical displacement ratio with continuous GPS, indicates that this uplift is likely to be associated with input of magmatic fluids from a shallow magma chamber. The method is promising to monitor magma intrusion processes, at this and other volcanoes.
Article: Submarine and inland gas discharges from the CampiFlegrei (southern Italy) and the Pozzuoli Bay: geochemicalclues for a common hydrothermal-magmatic source[show abstract] [hide abstract]
ABSTRACT: In this paper the results of a geochemical survey carried out on submarine and subaereal gas discharges located within the caldera of the Campi Flegrei (southern Italy) are presented and discussed. Gas samples were collected inland, i.e. from the Solfatara and Agnano craters and the Pozzuoli Bay, where at least five distinct main submarine fumarolic fields were recognized: Mar Morto, Mercato Ittico, Erculanea, Nisida and Fumose, the latter having the highest temperature (93 °C) among the submarine gas discharges. The chemical composition of the steam-dominated gases from the Solfatara crater and Pisciarelli area (western sector of the Agnano crater) is characterized by significant concentrations of H2S, H2 and CO (up to 18508, 2570 and 3.14 μmol/mol, respectively), suggesting that these fluids are produced by boiling of a hydrothermal aquifer where magmatic-related gas compounds (i.e. SO2, HCl, HF) are mostly dissolved. Geothermometric calculations based on chemical equilibria of both the CO2-CH4-H2 and C3H6-C3H8 systems indicate equilibrium temperatures in the range of 340-380 °C at redox conditions more oxidizing than those typically dominating hydrothermal reservoirs. The relatively high R/Ra ratios (from 2.9 to 3.1) indicate a clear He contribution from the mantle. The gas chemistry of the bubbling pools located at Agnano Terme, in the centre of the Agnano crater, is significantly different, being characterized by lower (two orders of magnitude) H2S and H2 concentrations, CO below the detection limit (0.01 μmol/mol), and a slightly lower (<2.6) R/Ra values. The measured CO2, CH4 and H2 concentrations of these gases indicate apparent equilibrium temperatures of ~200 °C.Procedia Earth and Planetary Science. 01/2011; 4:57-73.
Dataset: Pozzuoli Vaselli et al