An uncommon phreatomagmatic lateral eruption at Etna (Italy): relationship between eruptive activity and sedimentary basement setting.

Abstract

This paper documents a phreatomagmatic ¯ank eruption that occurred 18 700 100 a BP, on the lower north-eastern slope of Etna during the Ellittico volcano activity, which produced fall and surge deposits. This type of eruption is connected to a sedimentary basement ridge at Etna. The interaction between the rising magma and the shallow groundwater hosted in the volcanic pile overlying the impermeable sediments resulted in phreatomagmatic instead of strombolian activity. Three eruptive phases are distinguished based on ®eld and analytical data: (i) an explosive phreatomagmatic opening, (ii) a main phase producing coarse lithic-rich fallout and a strombolian deposit, and (iii) the ®nal pulsating surge-forming phase. The discovery of this phreatomagmatic ¯ank eruption, which occurred at lower altitude, raises important issues for previous hazard assessments at Etna.