Application of computer-assisted mapping to volcanic hazard evaluation of surge eruptions: Vulcano, lipari, and vesuvius

A previously developed computer-assisted model has been applied to several pyroclastic-surge eruptions at three active volcanoes in Italy. Model hazard maps created for various vent locations, eruption types, and mass production rates reasonably reproduced pyroclastic-surge deposits from several recent eruptions on Vulcano, Lipari, and Vesuvius. Small-scale phreatic eruptions on the island of Vulcano (e.g. the 1727 explosion of Forgia Vecchia) pose a limited but serious threat to the village of Porto. The most dangerous zone affected by this type of eruption follows a NNW fissure system between Fossa and Vulcanello. Moderate-sized eruptions on Vulcano, such as those associated with the present Fossa Crater are a much more serious threat to Porto as well as the entire area within the caldera surrounding the cone. The less frequent surge eruptions on Lipari have been even more violent. The extreme mobility of surges like those produced from Monte Guardia (approx. 20,000 y.b.p.) and Monte Pilato would not only threaten the entire island of Lipari, but also the northern part of neighboring Vulcano. Eruptions at Vesuvius with energy and efficiency similar to that of the May 18, 1980 blast of Mount St. Helens would be still more destructive because of the great initial elevation of the summit vent. In addition, surge eruptions at Vesuvius are generally part of more complex eruption cycles that involve several other types of volcanic phenomena including Plinian fall and pyroclastic flows.