Where it is and what it carries
The Cocos Plate covers about 2.9 million square kilometers, or 0.57% of Earth’s surface, in the eastern Pacific Ocean. It lies west of southern Mexico and Central America and north of the Galapagos Islands. It is entirely oceanic, and no country has land on it apart from small volcanic islands such as Cocos Island.
The plate is named after Cocos Island. It carries the Cocos Ridge, a band of thickened crust formed as the plate passed over the Galapagos hotspot.
What happens at its edges
The Cocos Plate is created on two sides and destroyed on a third. On its western side, it spreads away from the Pacific Plate along the East Pacific Rise at about 10 cm/yr on average and up to about 12.6 cm/yr. On its southern side, it spreads away from the Nazca Plate along the Galapagos Spreading Center at about 5.6 cm/yr. Near the meeting point of these two ridges sits the tiny Galapagos Plate.
The northeastern side is the Middle America Trench, a subduction zone that runs along the Pacific coast from Mexico to Panama. Here the Cocos Plate sinks beneath three different plates. It subducts under the North American Plate off southern Mexico and Guatemala at about 6.2 cm/yr, under the Caribbean Plate off El Salvador and Nicaragua at about 7.6 cm/yr, and under the Panama Plate off Costa Rica and western Panama at about 7.5 cm/yr. In the far northwest, it meets the small Rivera Plate along a short, slow boundary at about 1.3 cm/yr.
History
The Cocos Plate formed about 23 million years ago, when the Farallon Plate broke into the Cocos and Nazca plates along what became the Galapagos Spreading Center. Because the East Pacific Rise produces new crust quickly and the Middle America Trench consumes it, the seafloor entering the trench is relatively young. Young seafloor is warm and buoyant, which partly explains why the slab sinks at a shallow angle beneath central Mexico.
Earthquakes and volcanoes
The dataset lists 13 earthquakes of magnitude 6.5 or larger on the Cocos Plate itself since 1900. The largest was an M7.26 event in 1916 off Costa Rica. In 2016 an M6.9 earthquake struck offshore, south of El Salvador.
The plate’s real influence shows up on its neighbors. Large earthquakes along the Middle America Trench have epicenters on the overriding plates, such as the 2017 Tehuantepec earthquake (M8.2) in Mexico and the 2012 Nicoya earthquake (M7.6) in Costa Rica. Water released from the sinking slab also feeds the Central American Volcanic Arc, with volcanoes such as Fuego in Guatemala, Masaya in Nicaragua and Arenal in Costa Rica, along with many volcanoes in Mexico’s Trans-Mexican Volcanic Belt.
On the plate itself, the dataset lists two volcanoes, both submarine vents on the northern East Pacific Rise.