The Tyrrhenian Titan
Beneath the surface of the Tyrrhenian Sea, about 175 kilometers south of Naples, lies Marsili, the largest and highest active volcano in Europe. This enormous seamount is approximately 70 kilometers long and 30 kilometers wide, dwarfing terrestrial volcanoes like Mount Etna. It rises about 3,000 meters from the abyssal plain, its summit reaching to within 450 to 508 meters of the sea surface.
Marsili began forming between 0.7 and 1 million years ago in the Marsili Basin, a region of thin oceanic crust only about 10 kilometers thick. Its structure is a NNE-SSW elongated complex featuring multiple eruptive fractures and over 80 smaller adventitious cones. The volcano's activity is a result of the subduction of the Ionian tectonic plate. While its most recent eruptions are estimated to have occurred between 2,100 and 3,000 years ago, evidence of its active nature is abundant. Scientific monitoring has detected ongoing low-magnitude seismicity, hydrothermal venting, and significant heat flow from the volcano's crest. High heat flow measurements, reaching up to 500 mW/m2 in its central parts, combined with gravity and magnetic anomalies, point to the presence of a shallow magma chamber. Studies suggest the top of this magmatic reservoir sits approximately 2 to 3 kilometers below the volcano's crest.