The origin of the Aeolian islands has its origins in the collision between the African and Euro-Asiatic tectonic plates. The sliding of the African lithosphere below the euro-asiatic one resulted in a complex structure, a so-called volcanic arch, formed of one portion submerged, and another emerging, in an area of around 200km.
Besides the ‘seven sisters’ which emerged after eruptions over the course of millennia, submarine volcanoes (seamounts) such as Eolo, Enarete, Sisifo, Marsili etc. also make up part of the Aeolian arch.
Stromboli is an approximately 3,000 metre-high volcano, 2,000 metres of which extend below sea level, and 926 above the surface.
The first indication of its volcanic nature is provided by Strombolicchio, formed around 230,000 years ago. What now remains is a volcanic neck, formed by rock solidified inside the duct and now exposed by erosion.
The subsequent phase are:
Paleo-Stromboli (from c.100,000 to 35,000 years ago)
Vancori (from c.35,000 to 13,000 years ago)
Neo-Stromboli (from 13,000 to 5,000 years ago)
Recent-Stromboli (from 5,000 to today)
The collapse of the north-western side and subsequent landslides created the so called Street of Fire – a horseshoe – shaped depression inside which flows almost all the material erupted from the active craters.
The active craters of the recent Stromboli are situated around 200 metres below the summit of the island. Until 2002 there were three distinct craters: North-Eastern, the Central and South-West.
After the most recent eruptions, due to violent explosive activity and subsequent collapse, these three became one single crater, inside which there are several continuously forming months.
Stromboli is a strato-volcano, that is, formed by the accumulation of pyroclastic (explosive) matter and laval flows.