Thermal infrared surveys at Vulcano Island: an experimental approach to the thermal monitoring of volcanoes

The last eruption on Vulcano Island dates back to the end of 19th century. At present, its activity is confined to fumarole fields and sporadic limited phreatic eruptions; other types of surges have been recorded in the past. Two precise airborne infrared surveys were flown over the main cone of La Fossa volcano, where most of the fumarole fields occur, just before dawn and at noon, to give the most extreme temperature variations of the diurnal cycle. During the flights, meteorological data and rground radiance measurements were taken for calibration of thermographs. Later on, the original aerial data were processed by analogue and digital techniques, in order to improve the heat subsurface information. A similar method, recently used in the geothermal filed of Travale (Italy) for energy exploitation (Zilioli et al. 1985), enables us to describe the surface of the volcano in terms of thermal inertia. The influence of the emissivity on various lithologic units has also been taken into account. The algorithm applied seems to offer a more reliable look at the actual residual thermal anomalies, which can be interpreted as surface manifestations of existing heat fluxes.