Where two oceanic plates meet, one plate will give way to the other and will dive back into the mantle. This process is called subduction. Where they meet, both plates will be bent, and the resulting deformation can be seen as a deep trench. As the oceanic plate descends into the underlying asthenosphere, it heats up and partially melts. This molten material rises and forms volcanos on the leading edge of the non-descending plate (the up plate). Characteristically, these volcanos will have an andesitic composition. This andesitic composition is so linked with subduction zones and trenches that, where andesitic materials are found, it is assumed that they are the products of a subduction zone. Most often, these volcanos protrude above sea level as a chain of volcanos called a vulcanic island arc. 

As the rigid lithospheric plates descend into the asthenosphere, they force their way into mantle materials, maintaining their identity to depths of up to 700 miles. The resulting compression and tension forces acting on the descending plate generate earthquakes of varied foci, ranging from shallow to deep, until the plates lose their identity as they are remelted and recycled into the mantle. Many such examples exist in the Western Pacific, such as the Aleutian and the Phillippine Islands. In the Caribbean, the Windward Islands are associated with this type of convergence.