Why are most volcanoes located around the Pacific area?
Most of the Earth’s volcanoes are located around the Pacific Ocean because that is where most of the Earth’s subduction zones. A subduction zone is a place where one plate of oceanic lithosphere (= the crust + uppermost mantle) is shoved under another plate. The down going plate eventually starts to melt, and the material rises up to erupt through the overlying plate. If the overlying plate is a continent, you get a chain of volcanoes such as the Andes or Cascades. If the overlying plate is ocean you get a chain of volcanic islands such as the Marianas or Aleutians. This is also where the Earth’s deep ocean trenches are and where the Earth’s deep earthquakes are. The trenches form because the down going plate is bent downward as it subducts. The earthquakes form as the two plates scrape against each other (earthquakes down to about 150 km) and then as the down going plate bends (earthquakes down to about 700 km). The earthquakes do a very good job of tracing the position of the down go
