Plate tectonics
This theory views volcanism as the resultant of lithospheric processes rather than heat from the mantle rising up. Instead of heat coming up from deep in the mantle, volcanic anomalies come from a shallow source. Volcanism thus occurs where the crust is easier to break up because it has been stretched by lithospheric extension, allowing melt to reach the surface. Volcanic anomalies are created by plate tectonics such as spreading plate boundaries or subduction zones. The location of the volcanism is governed by the stress field in the plate and the amount of melt is governed by the fusibility of the mantle beneath. Plate tectonics can explain most of the volcanism on Earth.