Stromboli (Sicilian: Struògnuli, Ancient Greek: Στρογγύλη, Strongulē) is a small island in the Tyrrhenian Sea, off the north coast of Sicily, containing one of the three active volcanoes in Italy. It is one of the eight Aeolian Islands, a volcanic arc north of Sicily. This name is derived from the Ancient Greek name Strongulē which was given to it because of its round swelling form. The island's population is between 400 and 850. The volcano has erupted many times, and is constantly active with minor eruptions, often visible from many points on the island and from the surrounding sea, giving rise to the island's nickname "Lighthouse of the Mediterranean". The last major eruption was on April 13, 2009. Stromboli stands 926 m (3,034 ft) above sea level, but actually rises over 2,000 m (6,500 ft) above the sea floor. There are three active craters at the peak. A significant geological feature of the volcano is the Sciara del Fuoco ("Stream of fire"), a big horseshoe-shaped depression generated in the last 13,000 years by several collapses on the northwestern side of the cone. Two kilometres to the northeast lies Strombolicchio, the volcanic plug remnant of the original volcano. It is also known for being the inspiration behind Mordor, from J.R.R. Tolkien's Lord of the Rings.
Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust in the interiors of plates, e.g., in the East African Rift, the Wells Gray-Clearwater volcanic field and the Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "Plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth.