Stromboli Geology and Hazards
The island of Stromboli was built by a series of eruptions of potassium-rich basalt and basaltic andesite lavas. The first eruptions began about 200,000 years ago, and formed the now-eroded Strombolicchio volcano. Starting around 160,000 years ago, the island of Stromboli proper began forming. For the next 150,000 years, lava flows and pyroclastic deposits built a stratovolcano, which was eventually covered by pyroclastic deposits, lahars and lava flows. The Neostromboli period saw the formation of the modern volcanic edifice, which involved numerous flank and summit caldera collapses. The current eruptive vents are located at the top of the Sciara del Fuoco (Stream of Fire), a large collapse scar on the northwest side of the island which formed about 5,000 years ago.
Stromboli is the type location for the "Strombolian" style of eruptions. Strombolian eruptions are mild explosive events where "slugs" of gas periodically rise through a magma-filled volcanic conduit, burst at the surface, and throw bits of lava into the air. The lava falls as bombs (larger than about 3 inches in size) and scoria (smaller fragments), and eventually builds into a steep-sided volcanic cone.
The Sciara del Fuoco poses the most serious volcanic hazard on Stromboli. A catastrophic sector collapse would not only displace large volumes of material and possibly expose dike systems on the volcano's NW slope; it could also create a tsunami, which could cause much damage if it reached any of the other islands in the Aeolian archipelago or the Sicilian coast.