What is the relation between volcanos and plate tectonics?
When the tectonics plates move around they rub against each other and create friction and start creating a build up of pressure. They put pressure or sort of compress the magma under the Earth’s crust and when the pressure is too big it cannot be contained and the magma starts flying out of the compress area and a volcano is formed.
Found a good site for you to read through: http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/description_plate_tectonics.html From: Brantley, 1994, Volcanoes of the United States: USGS General Interest Publication Volcanoes are not randomly distributed over the Earth’s surface. Most are concentrated on the edges of continents, along island chains, or beneath the sea forming long mountain ranges. More than half of the world’s active volcanoes above sea level encircle the Pacific Ocean to form the circum-Pacific “Ring of Fire.” In the past 25 years, scientists have developed a theory — called plate tectonics — that explains the locations of volcanoes and their relationship to other large-scale geologic features.