When two oceanic plates converge, they create an island arc—a curved chain
of volcanic islands rising from the deep seafloor and near a continent. They are
created by subduction processes and occur on the continent side of the
subduction zone. Their curve is generally convex toward the open ocean. A deep
undersea trench is located in front of such arcs where the descending plate dips
downward. Examples include Japan and the Aleutian Islands in Alaska.
Figure 1.8 Oceanic-oceanic convergenceWhen two continental plates collide, mountain ranges are created as the
colliding crust is compressed and pushed upward. An example is the northern
margins of the Indian subcontinental plate being thrust under a portion of the
Eurasian plate, lifting it and creating the Himalayas.