Caribbean Plate

The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.

Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean

Plate borders the North American Plate, the South American Plate, the Nazca Plate and the Cocos Plate. These borders are regions of intense seismic activity, including frequent earthquakes, occasional tsunamis, and volcanic eruptions.

Boundary types

The northern boundary with the North American plate is a transform or strike-slip boundary which runs from the border area of Belize, Guatemala (Motagua Fault), and Honduras in Central America, eastward through the Cayman trough on south of the southeast coast of Cuba, and just north of Hispaniola, Puerto Rico, and the Virgin Islands. Part of the Puerto Rico Trench, the deepest part of the Atlantic Ocean (roughly 8,400 meters), lies along this border. The Puerto Rico trench is at a complex transition from the subduction boundary to the south and the transform boundary to the west.

The eastern boundary is a subduction zone, the Lesser Antilles subduction zone, where oceanic crust of the South American Plate is being subducted under the Caribbean Plate. Subduction forms the volcanic islands of the Lesser Antilles Volcanic Arc from the Virgin Islands in the north to the islands off the coast of Venezuela in the south. This boundary contains seventeen active volcanoes, most notably Soufriere Hills on Montserrat;, Mount Pelée on Martinique; La Grande Soufrière on Guadeloupe; Soufrière Saint Vincent on Saint Vincent; and the submarine volcano Kick-’em-Jenny which lies about 10 km north of Grenada. Large historical earthquakes in 1839 and 1843 in this region are possibly megathrust earthquakes.

Along the geologically complex southern boundary, the Caribbean Plate interacts with the South American Plate forming Barbados, Trinidad and Tobago (all on the Caribbean Plate), and islands off the coast of Venezuela (including the Leeward Antilles) and Colombia. This boundary is in part the result of transform faulting along with thrust faulting and some subduction. The rich Venezuelan petroleum fields possibly result from this complex plate interaction.

The western portion of the plate is occupied by Central America. The Cocos Plate in the Pacific Ocean is subducted beneath the Caribbean Plate, just off the western coast of Central America. This subduction forms the volcanoes of Guatemala, El Salvador, Nicaragua, and Costa Rica, also known as the Central America Volcanic Arc.

Origin

There are two contending theories as to the origin of the Caribbean Plate.

One holds that it is a large igneous province that formed in the Pacific Ocean tens of millions of years ago. As the Atlantic Ocean widened, North America and South America were pushed westward, separated for a time by oceanic crust. The Pacific Ocean floor subducted under this oceanic crust between the continents. The Caribbean Plate drifted into the same area, but as it was less dense (although thicker) than the surrounding oceanic crust, it did not subduct, but rather overrode the ocean floor, continuing to move eastward relative to North America and South America. With the formation of the Isthmus of Panama 3 million years ago, it ultimately lost its connection to the Pacific.

A more recent theory asserts that the Caribbean Plate came into being from an Atlantic hotspot which no longer exists. This theory points to evidence of the absolute motion of the Caribbean Plate which indicates that it moves westward, not east, and that its apparent eastward motion is only relative to the motions of the North American Plate and the South American Plate.