The evolution of a dynamic geological system: the support of a GIS for geochemicd measurements at the fumarole field of Vulcano, Italy

The island of Vulcano (Aeolian arc, Southern Italy) has displayed several periods of volcanic unrest since the end of the
last eruption (1890). We report here results obtained from a long-term survey concerning variations of both the steam output
and the exhaling surface area at the sun~mit crater fumarolic field of La Fossa. The field measurements analysed in a
Geographiciil Information System (GIS: show a highly dynamic volcanic system in which deep variations in the
geochemishy and the temperature of the released fluids were accompanied by fluctuations in the mass output of steam and
the topography of the crater field. The use of a GIS facilitated digitized reconstructions of maps of the crater field in addition
to analysis (of the steam flux data. The furnarolic field expanded its surface area from 50 m2 in 1983 to more than 2400 m*
in 1995, accompanied by an increase in steam output from 152 to about 1400 tonnes per day. The possibility that the
observed phenomena are related to volcano-tectonic activity and to magma uprising is taken into consideration.

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