Bolivia hosts numerous active and extinct volcanoes across its territory. The active volcanoes are located in western Bolivia where they make up the Cordillera Occidental, the western limit of the Altiplano plateau. Many of the active volcanoes are international mountains shared with Chile. All Cenozoic volcanoes of Bolivia are part of the Central Volcanic Zone (CVZ) of the Andean Volcanic Belt that results due to processes involved in the subduction of the Nazca Plate under the South American Plate. The Central Volcanic Zone is a major upper Cenozoic volcanic province. Apart from Andean volcanoes, the geology of Bolivia hosts the remnants of ancient volcanoes around the Precambrian Guaporé Shield in the eastern part of the country.