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ItalyThe fluctuating behaviour of the volcanic system of Vulcano, which caused changes in chemical physical properties of surface manifestations, moderate ground inflation and seismicity, is interpreted to be the result of different contributions of the deep-seated magma (fire) and the near-surface aqueous environment (water). The phenomena observed during the last fifteen years are explained by variations in these two contributions. A factor analysis method was applied to the variation of temperature and chemical composition of fumarolic gases. The results support the model. The absence of major seismic events rules out eruptive activity caused by ascending magma. Significant thermal output from the deeper portions of the system into shallow aquifers, however, caused vaporization of water and, conse quently, pressure increase and inflation of the volcano. Landslides in the weakest sectors of the crater slopes can be caused by inflation. The resulting pressure decrease beneath the volcano may have trig gered the emission of gases.

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