Oceanic plates are usually subducted back into the mantle in subduction zones. The subducted oceanic crust triggers volcanism. They occur almost exclusively at convergent boundaries in association with subducted oceanic lithosphere. This leading edge was then subducted by a NE-dipping subduction zone. Consequently, most oceanic crust is subducted easily at an oceanic trench. Oceanic crust can be subducted, while continental crust cannot. Although originally attributed to a melting of subducted oceanic crust, recent evidence belies this connection. The calcareous ooze blanketing Nazca Ridge is completely subducted. Frontal erosion is most active in the wake of seamounts being subducted beneath the forearc. Volcanoes result primarily from the melting of subducted crust material. The Pacific Plate is being subducted beneath these plates, resulting in volcanic activity. Any older Pacific floor crust has been subducted. The islands were carried eastward as the plate subducted the South American continent. Crust to the west was subducted later. The Cocos Plate is being subducted beneath the Caribbean Plate, in Central America.