Colonne d'alimentation en magma stationnaire et migration vers la mer des anciens centres d'activité du mont Etna

Abstract

We thank 258 volunteer field assistants for their hard work and dedication to this project, and the Parco dell'Etna, the Corpo Forestale, the Mayor of Linguaglossa and the Aziende Foreste for permission to work in their areas of jurisdiction, and the Osservatorio Astrofisico (Catania) who gave permission to use their land for GPS, levelling and Dry Tilt stations. We are grateful to Salvo Caffo of the Parco dell’Etna for help and advice over many years, to the Ordnance Survey for donation of GPS equipment, to the Istituto Internazionale di Vulcanologia (Catania) for the loan of vehicles and equipment between 1981 and 1989, to the University of East London and University College London for the loan of equipment in 2001 and 2011, and to Mark Breach of Nottingham Trent University for converting the individual trilateration distances and vertical angles measured between 1987 and 1994 into spherical xyz coordinates with STAR*NET - PRO. This work was supported by 6 CNRS (France) grants 1981, 1982, 1983, 1984, 1985, 1986, 2 NATO grants 1987-89 & 1989-1991, U.K. Natural Environment Research Council (NERC) grants NER/A/S/2001/00686, NER/A/S/2002/00411, NER/A/S/2003/00105, NE/D001390/1, NE/E007589/1, and 2 previous NERC grants 1987-88 & 1995-97, also 3 European Union grants ERB40002PL900491-(90400491), EV5V-CT92-0170 & ENV4-CT96-0294, a Leverhulme Trust (U.K.) grant 1995-98, 3 Open University (U.K.) Research grants 1990, 1991, 1998-2000, and by NERC GEF loan Nos. 727, 776, 799, 825 and 869. Since 2008 this project has been self-funded through the kind generosity of 93 field assistants. We also thank David A. Rothery, Open University, and Douglas C. Heggie, Edinburgh University, who read and commented on earlier versions of the manuscript.Annual ground surveying 1981-2023 indicates that land east of Etna's summit is being carried eastwards from a north-south spreading axis at a mean velocity of 91 ±55 mm/yr. If this easterly velocity is representative of past epochs, earlier volcanic centres that are now 3 to 25 km downslope must also have moved eastwards from their original positions, which may have been at the present summit. We use existing data on positions and radioisotopic ages of earlier volcanic centres to make a second, independent determination of present eastward velocity, which gives a result of 74 ±29 mm/yr. The closeness of these values is confirmation that Etna's central crater and magma supply system have always been where they are today, rather than having progressively migrated westward upslope as generally believed. We conclude that Etna is an unusual type of rapidly spreading continental margin volcano with a stationary, shallow magma generation system.Les relevés de terrain annuels effectués entre 1981 et 2023 indiquent que les terres situées à l'est du sommet de l'Etna sont entraînées vers l'est à partir d'un axe d'étalement nord-sud à une vitesse moyenne de 91 ±55 mm/an. Si cette vitesse vers l'est est représentative des époques passées, les centres volcaniques antérieurs qui se trouvent aujourd'hui à une distance de 3 à 25 km en aval doivent également s'être déplacés vers l'est à partir de leur position d'origine, qui peut avoir été le sommet actuel. Nous utilisons les données existantes sur les positions et les âges radio-isotopiques des centres volcaniques antérieurs pour effectuer une deuxième détermination indépendante de la vitesse actuelle vers l'est, qui donne un résultat de 74 ±29 mm/an. La proximité de ces valeurs confirme que le cratère central de l'Etna et le système d'alimentation en magma ont toujours été là où ils sont aujourd'hui, et qu'ils n'ont pas migré progressivement vers l'ouest en remontant la pente, comme on le pense généralement. Nous concluons que l'Etna est un type inhabituel de volcan de marge continentale à expansion rapide avec un système de génération de magma stationnaire et peu profond