by Jörg Erzinger, Christopher J.R. Kilburn, Agust Gudmundsson

Large calderas are the most dangerous volcanoes on the Earth. They are produced by collapse during explosive super-eruptions, which are capable of triggering a global catastrophe second only to that from a giant meteorite impact. The mechanisms for unrest and eruptions at large calderas are at a large extent unknown and, as demonstrated by volcanological research in the last decades, they may be very different from those characterizing more commonly studied stratovolcanoes. Campi Flegrei caldera (Italy) represents an ideal natural laboratory to fully understand mechanisms of caldera dynamics and to develop techniques for eruption forecast and effective risk mitigation. It is an active volcanic area marked by a quasi-circular caldera depression, formed by huge ignimbritic eruptions (Fig.1). The caldera has recently experienced intense deformation, originating uplift phenomena of more than 3.5 m in 15 years, with maximum rates of 1 m/year in the period 1982-1984, which caused the temporary evacuation of 30,000 people from the centre of Pozzuoli and exposed more than 500,000 to the risk of pyroclastic flows (several millions in case of an ignimbritic eruption). The role of deep drilling at this area is then crucial. It could give a fundamental, precise insight into the shallow substructure, the geometry and character of the geothermal systems and their role in the unrest episodes, as well as to explain magma chemistry and the mechanisms of magma-water interaction. Detailed studies of ‘in situ’ physical properties (e.g. temperature, sonic logs, permeability), at increasing depths would provide information about key questions about the substructure and the source mechanism of caldera unrest. The choice of Campi Flegrei as target for the deep study of large calderas is justified by the evidence, from previous drillings and recent deformation and seismicity observations, that it has the structures of main volcanological interest considerably shallower with respect to other well studied similar calderas (i.e. Long Valley). For this reason, the inference about its substructure, thermal state, magma chamber and geothermal system will allow a considerable scientific step towards the understanding of the most peculiar and potentially catastrophic volcanic areas of the World. This ICDP proposal will be also a unique opportunity to experiment and install new technologies for deep borehole monitoring (Campi Flegrei Deep Observatory, CFDO) and seafloor monitoring. The present proposal then represents a unique opportunity to deeply understand one the most crucial issues in volcanology, with strong implications for defence from catastrophes which may attain global scale in case of caldera collapses. It is After favourable evaluation of the pre-proposal by ICDP panel, two Workshops have been held in May and November 2006 to prepare the full proposal, presented in 2007 and here revised to integrate the panel’s comments.

• The main scientific objectives will be achieved by addressing the following targets.
• To determine the main lithological, structural and rheological transitions in the upper crust.
• To determine the temperature and stress fields of the upper crust.
• To develop quantitative models of the magmatic-geothermal system and its relation to caldera unrest and eruptions; these models will be verified using data obtained directly from drilling.
• To test and to improve current reconstructions of the volcanic history of Campi Flegrei since before caldera formation, combining both on-land and off-shore data.
• To develop install a deep observatory for continuous monitoring of temperature, strain and fluid geochemistry close to the sources producing unrests, and to develop a sea-floor monitoring network for effective risk mitigation at the area.
• To develop and test quantitative models to discriminate pre-eruptive patterns in Campi Flegrei and other large calderas.
• To achieve these targets, the project has been divided into four Workpackages, leaded by PIs. Each Workpackage involves an international team of institutions. The themes for each Workpackage have been designed to be self-sustaining and to attract interest from several funding sources, in order to make Campi Flegrei an international laboratory for the advanced study of caldera volcanism, volcanic risk mitigation and development of new technologies for environmental monitoring.

CAMPI-FLEGREI, FLEGREI, Geothermal System, Geothermy, ICDP-2008/05, Italy, Magma Chamber, Volcanic Hazards, Volcanic Systems

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