Lava effusion — A slow fuse for paroxysms at Stromboli volcano?

The 2007 effusive eruption of Stromboli followed a similar pattern to the previous 2002–2003 episode. In both cases, magma ascent led to breaching of the uppermost part of the conduit forming an eruptive fissure that discharged lava down the Sciara del Fuoco depression. Both eruptions also displayed a ‘paroxysmal’ explosive event during lava flow output. From daily effusion rate measurements retrieved from helicopter- and satellite-based infrared imaging, we deduce that the cumulative volume of lava erupted before each of the two paroxysms was similar. Based on this finding, we propose a conceptual model to explain why both paroxysms occurred after this ‘threshold’ cumulative volume of magma was erupted. The gradual decompression of the deep plumbing system induced by magma withdrawal and eruption, drew deeper volatile-rich magma into the conduit, leading to the paroxysms. The proposed model might provide a basis for forecasting paroxysmal explosions during future effusive eruptions of Stromboli. ► Our aim was to explain why the 2003 and 2007 paroxysms occurred at Stromboli volcano. ► Our model states that paroxysms occurred after a ‘threshold’ volume of magma was erupted. ► This caused decompression of the deep plumbing system and uprise of volatile-rich magma. ► Volatile-rich magma entering the upper conduit triggered paroxysms. ► The proposed model might forecast paroxysmal explosions during future effusive eruptions.