Plates Subduct

When an ocean plate collides with another ocean plate or with a plate carrying continents, one plate will bend and slide under the other. This process is called subduction. A deep ocean trench forms at this subduction boundary. As the subducting plate plunges deep into the mantle, it gets so hot it melts the surrounding rock. The molten rock rises through the crust and erupts at the surface of the overriding plate. The result is either a volcanic mountain range such as the Cascades and Andes, or chains of islands called island arcs such as Japan and the Aleutian Islands. (Illustration by E. Paul Oberlander, © Woods Hole Oceanographic Institution)