This melt then rises through the crust and generates volcanoes at the surface.
These are known as subduction volcanoes, or arc volcanoes, and every active subduction zone has a chain of volcanoes generated by the addition of water to mantle. For example, in Japan, the Pacific Plate is subducting under Asia; in Chile, the Pacific Plate is subducting under the South American plate; and in the northwest United States, the Juan de Fuca Plate is subducting beneath the North American Plate (creating volcanoes like Mount St. Helens).
Although subduction volcanoes dominate Italy’s west coast, it’s largest and most active volcano is not related to subduction. Mount Etna is located in eastern Sicily and stands over three kilometers (11,000 feet) above the ocean. It is one of the most active volcanoes in the world, spewing ash, lava, and gas nearly as often as Mauna Loa in Hawai’I (which erupts, on average, every 3.5 years).
So how do scientists know that it is not an arc volcano, even though it is so close to a subduction zone?
The chemistry of the lavas.
Geochemists analyze the chemical make-up of lavas erupted all over the world to determine their origin. For example, magnesium and iron are found deep in the mantle while potassium and quartz are only found in the crust. Mount Etna’s lavas are rich in Magnesium and Iron, but also have a lot of potassium.