Sea level and coastal evolution in volcanic areas: the case of the Somma-Vesuvius

Detailed micropalaeontological and petrochemical analyses of rock samples from boreholes drilled at the archaeological excavations of Herculaneum, ~7 km west, and Pompeii, ~8 km east of the Somma-Vesuvius crater, allowed reconstruction of the Late Quaternary palaeoenvironmental evolution of the sites (Marturano et al., 2009; 2012). The Holocenic sedimentary sequence, on which the archaeological remains rest, has risen several meters at an average rate of 4-5 mm/yr. The uplift has also involved the western apron of the volcano and the Sebeto-Volla Plain, a populous area including the eastern suburbs of Naples, the areas of the Sarno valley (SE of the volcano) and the Somma-Vesuvius eastern apron (Marturano et al., 2011). The data depicted a framework of synchronous ground movements for the whole Somma-Vesuvius edifice, with uplift already in progress at 15-17 ka, a few kyrs after the beginning of the interglacial phase (20-19 ka). In the same period from which appear to start the ground movements, two large explosive events (i.e., 22 ka Pomici di Base and 19 ka Pomici Verdoline) occurred. The following exponential uplift coincides with a period of low documented eruptive activity in contrast with the late phase (after ~9 ka) in which the ground level remains relatively constant and plinian and subplinian eruptions happen (i.e., 9 ka Mercato, 4.3 ka Avellino, A.D. 79 Pompei, A.D. 412 Pollena and the A.D. 1631 Villa Inglese; Santacroce et al., 2008). An axisimmetric deep source of strain is considered responsible for the long-term uplift affecting the whole Somma-Vesuvius edifice. The deformation pattern was modelled by a single pressure source, sited in the lower crust and surrounded by a shell of Maxwell viscoelastic medium, which experienced a pressure pulse that began at the Last Glacial Maximum.