CO2 degassing and energy release at Solfatara volcano, Campi Flegrei, Italy

In the present period of quiescence, the Solfatara volcano, 1 km far from P ozzuoli, releases 1500 t d(-1) of hydrothermal CO2 through soil diffuse deg assing from a relatively small area (0.5 km). This amount of gas is compara ble to that released by crater plume emissions of many active volcanoes. On the basis of the CO2/H2O ratio measured in high-temperature fumaroles insi de the degassing area, we computed a total thermal energy flux of 1.19 X 10 (13) J d(-1) (138 MW). Most of this energy is lost by shallow steam condens ation and transferred to the atmosphere through the hot soil of the degassi ng area. The thermal energy released by diffuse degassing at Solfatara is b y far the main way of energy release from the whole Campi Flegrei caldera. It is 1 order of magnitude higher than the conductive heat flux through the entire caldera, and, during the last 20 years, it was several times higher than the energy associated with seismic crises and ground deformation even ts. It is possible that changes in the energy flux from a magma body seated underneath Solfatara and/or argillification processes at relatively shallo w depths determine pressurization events in the hydrothermal system and con sequently ground deformation and shallow seismic swarms, as recorded during the recent episodes of volcanic unrest centered at Pozzuoli.