Chronology of the Vesuvius activity from A.D. to 1631 based on archaeomagnetism of lavas and historical sources

The activity of Vesuvius between A.D. 79 and 1631 has been investigated by means of precise archaeomagnetic dating of primary volcanic deposits and taking into account the stratigraphy of lavas and tephra, historical written accounts, archaeological evidence related to the developing urbanisation, and radiocarbon ages. We found that the historical record is highly useful in constraining the timing of the main events, even if data are often too scarce and imprecise for ascertaining the details of all phases of activity and especially their magnitude and emplacement of all the deposit types. In addition, some eruptions that took place in the 9th and 10th centuries appear unnoticed by historians. The archaeomagnetic study involved 26 sites of different lavas and 2 pyroclastic deposits. It shows that within the 15 centuries which elapsed between A.D. 79 and 1631, the effusive activity of Vesuvius clustered in the relatively short period of time between A.D. 787 and 1139 and was followed by a 5-centuries-long repose period. During this time Vesuvius prepared itself for the violent explosive eruption of 1631. The huge lava flows shaping the morphology of the coast occurred largely through parasitic vents located outside the Mount Somma caldera. One of these parasitic vents is located at low elevation, very close to the densely inhabited town of Torre Annunziata. Among the various investigated lavas, a number of which were previously attributed to the 1631 eruption, none is actually younger than the 12th century. Therefore, it is definitively concluded that the destructive 1631 event was exclusively explosive