Subduction leads to volcanic activity because as the subducting plate descends lower into the earth, it develops more and more temperature and the increased temperature and pressure results in volcanic activity.
EXPLANATION:
Subduction takes place when a continental and an oceanic plate collide. The oceanic plate is less buoyant than the continental plate and therefore subducts under the continental plate.
As this plate sinks deeper, the temperature increases leading to the release of fluid and the formation of magma.
