the Caribbean Plate and the South American Plate occurs along the faults of Boconó, El Pilar and San Sebastián. 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 The usual theory of the origin of the Caribbean Plate was confronted by a contrasting theory in 2002. The mainstream theory holds that it is the Caribbean large igneous province (CLIP) which formed in the Pacific Ocean tens of millions of years ago, perhaps originating at the Galapagos Hotspot. 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 CLIP drifted into the same area, but as it was less dense and 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. The 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. First American land bridge The Caribbean Plate began its eastward migration (Ma) during the Late Cretaceous. This migration eventually resulted in a volcanic arc stretching from northwestern South America to the Yucatán Peninsula, today represented by the Aves Islands and the Lesser and Greater Antilles. This arc was the subject of constant tectonism and sea-level fluctuation, but lasted until the mid-Eocene and intermittently formed a land bridge along the eastern and northern boundaries of the Caribbean Plate. What would eventually become present-day Central America, part of the western plate boundary, was still isolated in the Pacific. , during the Late Paleocene, a local sea-level low-stand assisted by the continental uplift of the western margin of South America, resulted in a fully operative