East Pacific and Chile Rise
A triple junction, the Chile Triple Junction, occurs on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula at the southern coast of Chile. Here three tectonic plates meet: the Nazca Plate, the South American Plate, and the Antarctic Plate.
The eastern margin is a convergent boundary subduction zone under the South American Plate and the Andes Mountains, forming the Peru–Chile Trench. The southern side is a divergent boundary with the Antarctic Plate, the Chile Rise, where seafloor spreading permits magma to rise. The western side is a divergent boundary with the Pacific Plate, forming the East Pacific Rise. The northern side is a divergent boundary with the Cocos Plate, the Galapagos Rise.
The subduction of the Nazca plate under southern Chile has a history of producing massive earthquakes, including the largest ever recorded on earth, the moment magnitude 9.5 1960 Valdivia earthquake.