This feature is formed at destructive boundaries where the denser plate (usually the oceanic plate) is subducted underneath the less dense plate (usually the continental plate).
Explanation:
the stress in the boundary between the two plates causes them to warp at the boundary forming a trench. This forced bending and the friction between the two plates (remember tectonic plates are very rugged) causes fissures to develop at the boundary. As the denser plate dives into the mantle, it begins to melt and the molten rock rises through the fissures. The magma erupts at the surface in several fissures forming volcanic mountains ranges along the convergent boundary.
