Double origin of hydrothermal convective flux variations in the Fossa of Vulcano (Italy) |
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| Authors: | Maurice Aubert Serena Diliberto Anthony Finizola Yashmin Chébli |
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| Institution: | (1) Université Blaise Pascal et CNRS-LMV, 5 rue Kessler, 63038 Clermont Cedex, France;(2) Istituto Nazionale di Geofisica e Vulcanologia-Sezione di Palermo, via Ugo La Malfa, 153, 90146 Palermo, Italy;(3) Laboratoire Géosciences Réunion, UR, IPGP, UMR 7154, 15 avenue René Cassin, BP 7151, 97715 Saint Denis cedex 9, La Réunion, France |
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| Abstract: | Soil-temperature measurements can provide information on the distribution of degassing fissures, their relationship to the
internal structure of the volcano, and the temporal evolution of the system. At Vulcano Island (Italy), heat flux from a <3
km-deep magma body drives a hydrothermal system which extends across the main Fossa crater. This heat flux is also associated
with variable magmatic gas flow. A high-density map of soil-temperatures was made in 1996 at a constant depth of 30 cm on
the central and southern inner flanks of the Fossa crater. These measurements extended over an area covering about 0.04 km2, across which the heat flux is predominantly associated with a shallow boiling aquifer. The map shows that hot zones relate
to structures of higher permeability, mainly associated with a fissure system dating from the last eruptive cycle (1888–1890).
From 1996 to January 2005, we studied the evolution of the heat flux for the high temperature part of the map, both by repeating
our measurements as part of 14 visits, during which temperatures were measured at a constant depth, and using data from permanent
stations which allowed soil-temperatures to be continuously measured for selected vertical profiles. These data allowed us
to calculate the heat flux, and its variation, with good precision for values lower than about 100 W m−2, which is generally the case in the study area. Above 100 W m−2, although the heat flux value is underestimated, its variations are recorded with an error less than 10%. During the period
1996–2004, two increases in the thermal flux were recorded. The first one was related to the seismic crisis of November 1998
which opened existing or new fissures. The second, in November 2004, was probably due to magma migration, and was associated
with minor seismic activity. |
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| Keywords: | Hydrothermal flux Soil-temperature Monitoring Seismic activity Vulcano |
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