THE INTERPLINIAN ACTIVITY AT SOMMA-VESUVIUS IN THE LAST 3500 YEARS

Between 1884 B.C. and A.D. 472, eruptive activity at Somma-Vesuvius wa s dominated by the three plinian eruptions of Avellino (3550 yr B.P.), Pompei (A.D. 79) and A.D. 472 and, as a result, little attention has been given to the intervening interplinian activity. The interplinian events are here reconstructed using new data from twenty stratigraphic sections around the lower flanks of the volcano. Three main eruptions have beer identified for the protohistoric period (3550 yr B.P.-A.D. 79). The first two occurred shortly after the Avellino event and both show a progression from magmatic to phreatomagmatic behaviour. The thi rd eruption (2700 B.P.) consisted of five phreatomagmatic episodes sep arated by the emplacement of mud flows. Only one event, the explosive eruption of A.D. 203, has been identified for the ancient historic per iod (A.D. 79-472). In contrast, the A.D. 472 eruption was followed dur ing the medieval period (A D. 472-1631) by comparatively vigorous inte rplinian activity, including four strombolian-phreatomagmatic events a nd extensive lava effusion, which formed a summit cone (destroyed in A .:D. 1631) similar to that on Vesuvius today. Such regular alternation s of plinian and interplinian events are evident only since 3550 yr B. P. and provide important constraints for forecasting future behaviour at Somma-Vesuvius. (C) 1998 Elsevier Science B.V. All rights reserved.