Onset of the persistent activity at Stromboli Volcano (Italy)

Stromboli, known worldwide as the "Lighthouse of the Mediterranean", is com monly believed to have been in a state of persistent activity for the past 2000-2500 years. However, historical sources older than 1000 A.D. are not a ccurate enough to assess if the activity of the volcano was exactly the sam e as we see at present. In order to attempt to identify the onset of the pr esent eruptive regime, and assess if it has been maintained with the same c haracteristics through time, stratigraphic and radiometric studies of the r ecent tephra deposits were undertaken. Up to 4-m-deep stratigraphic trenche s, dug at a height of approximately 500 m on the NE flank of the volcano, e xposed a conformable tephra pile containing charcoal fragments. One of the most interesting finds was the discovery of a 7-cm-thick weathered bed rich in organic matter (thin palaeosol) approximately 3 m below the surface. Th e sequence underneath the palaeosol consists of decimetre-thick lapilli fal lout beds alternating with ash deposits bearing small charcoals with calibr ated ages of between the fourth century B.C. and the first century A.D. The sequence above the palaeosol is charcoal free and consists of coarse-ash d eposits with discrete, centimetre-thick lapilli fallout beds composed of cr ystal-poor golden pumice and subordinate crystal-rich black scoriae similar to scoria/pumice pairs emitted during the more energetic explosions of the present-day activity. The data collected indicate that between the third a nd seventh centuries A.D., after a period of quiescence, the activity resum ed with an eruptive style identical to the present one. We conclude that th e "Lighthouse of the Mediterranean" actually began its activity in a period much later than previously thought.