The only land above water on the Cocos Plate is Cocos Island, which is administered by Costa Rica and lies approximately 550 km (342 mi; 297 nmi) southwest of the Costa Rican mainland.
Geology
The Cocos Plate was created by sea floor spreading along the East Pacific Rise and the Cocos Ridge, specifically in a complicated area geologists call the Cocos-Nazca spreading system. From the rise the plate is pushed eastward and pushed or dragged (perhaps both) under the less dense Caribbean Plate, in the process called subduction. The subducted leading edge heats up and adds its water to the mantle above it. In the mantle layer called the asthenosphere, mantle rock melts to make magma, trapping superheated water under great pressure. As a result, to the northeast of the subducting edge lies the continuous arc of volcanos —also known as the Central America Volcanic Arc— stretching from Costa Rica to Guatemala, and a belt of earthquakes that extends farther north, into Mexico.
The Rivera Plate north of the Cocos Plate is thought to have separated from the Cocos Plate 5–10 million years ago. The boundary between the two plates appears to lack a definite transform fault, yet they are regarded as distinct. After its separation from the Cocos Plate, the Rivera Plate started acting as an independent microplate.[2]