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The Sicilian Channel (Fig. 4.1) is a vast NW-SE extensional tectonic structure, situated between Sicily and north-east Tunisia (Winnock, 1981; Reuther and Eisbachr, 1985), controlled by NW-SE faults; other than these main discontinuities there are also active faults trending NE-SW and NS, found both in the sea and oniand (Cello et al., 1984; Boccaletti et al., 1987; Lanti et al., 1988). The channel represents the expression, after the formation of the Apeninic-Maghrebian chain, of the post-collisional evolution of the northern border of the African foreland. Along the axis of the channel, in areas of continental crust thinning, rifts up to 1,000 m deep developed (Messinian and Lower Pliocene), flanked by NW-SE faults. Locally the faults allow the rising of deep magmas, and an alkaline, per-alkaline, and tholeiitic volcanism developed in the channel. This began at 8 Ma (Beccaluva et al., 1981) and is in part still active, it constitutes various submarine centres and the composite volcanoes of Pantelleria and Linosa. The island of Linosa has a surface area of 6 km² and a maximum elevation of 196 m above sea level. It is a small part (0.1%) of a large submarine volcanic complex, which has its base at 800 m below sea level and is linked to the NW-SE faults that border, to the