Deciphering the effusive-explosive transitions and the construction of a volcanic cone from geological data: the example of Monte dei Porri, Salina Island (Italy)

New stratigraphic data allowed the reconstruction of the activity responsible of the construction of the Monte dei Porri cone. Alternating explosive and effusive activity, which emplaced fall and pyroclastic density current deposits, and lava flows, form the volcanic cone. The magma composition that fed the different phases of the Monte dei Porri eruptive cycle is poorly evolved to intermediate (basaltic, basaltic andesite and andesite), with the exception of that of the initial phase (dacitic). Hydromagmatic fragmentation cannot be claimed for explaining large variations in explosivity deduced from the stratigraphic succession, being excluded by SEM image analysis on coarse ash from the different pyroclastic units. This suggests that mechanisms responsible of eruption style transitions have to be searched in timing of magma rising, including variations in the local tectonic stress in combination with variable magma chamber overpressure.