| Cocos plate | |
|---|---|
 | |
| Type | Minor |
| Approximate area | 2,900,000 km2[1] |
| Movement1 | north-east |
| Speed1 | 67 mm/year |
| Features | Cocos Island,Pacific Ocean |
| 1Relative to theAfrican plate | |
TheCocos plate is a young oceanictectonic plate beneath thePacific Ocean off the west coast ofCentral America, named forCocos Island, which rides upon it. The Cocos plate was created approximately 23 million years ago when theFarallon plate broke into two pieces, which also created theNazca plate. The Cocos plate also broke into two pieces, creating the smallRivera plate.[2] The Cocos plate is bounded to the northeast by theNorth American plate and theCaribbean plate. To the west it is bounded by thePacific plate and to the south by theNazca plate.
The only land above water on the Cocos plate isCocos Island, which is administered byCosta Rica and lies approximately 550 km (342 mi; 297 nmi) southwest of the Costa Rican mainland.
The Cocos plate was created bysea floor spreading along theEast Pacific Rise and theCocos 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 denseCaribbean plate, in the process calledsubduction. The subducted leading edge heats up and adds its water to the mantle above it. In the mantle layer called theasthenosphere, mantle rock melts to makemagma, trappingsuperheated water under great pressure. As a result, to the northeast of the subducting edge lies the continuous arc ofvolcanos – also known as theCentral America Volcanic Arc – stretching fromCosta Rica toGuatemala, and a belt of earthquakes that extends farther north, intoMexico.
The northern boundary of the Cocos plate is theMiddle America Trench. The eastern boundary is atransform fault, thePanama fracture zone. The southern boundary is amid-oceanic ridge, theCocos–Nazca spreading centre.[3] The western boundary is another mid-ocean ridge, theEast Pacific Rise.
Ahotspot under theGalápagos Islands lies along the Galápagos Rise. (seeGalápagos hotspot andGalápagos microplate)
TheRivera 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 definitetransform fault, yet they are regarded as distinct. After its separation from the Cocos plate, the Rivera plate started acting as an independent microplate.[2]
The devastating1985 Mexico City earthquake and the2017 Chiapas earthquake were results of the subduction of the Cocos plate beneath theNorth American plate. The devastating El Salvador earthquakes inJanuary 2001 andFebruary 2001 were generated by the subduction of this plate beneath theCaribbean plate.
