Along Tectonic Plate BoundariesMost volcanoes form at the edges of tectonic plates, where the Earth's crust is either being created or destroyed. a. Convergent Boundaries (Plates Collide)One plate sinks beneath another (subduction).Volcanoes form on the overriding plate.Example: Ring of Fire (surrounding the Pacific Ocean) b. Divergent Boundaries (Plates Move Apart)Magma rises through the gap and creates new crust.Volcanoes form along mid-ocean ridges.Example: Mid-Atlantic Ridge, East African Rift