Volcanoes of Mexico are related to subduction of the Cocos and Rivera Plates to the east, which has produced large, explosive eruptions. Most active volcanoes in Mexico occur in the Trans-Mexican Volcanic Belt, which extends from west to east across central-southern Mexico. A few other active volcanoes in northern Mexico are related to extensional tectonics of the Basin and Range Province, which splits the Baja California peninsula from the mainland. Popocatépetl, lying in the eastern half of the Trans-Mexican Volcanic Belt, is the second-highest peak in Mexico after the Pico de Orizaba. It is one of the most active volcanoes in Mexico, having had more than 20 major eruptions since the arrival of the Spanish in 1519. The 1982 eruption of El Chichón, which killed about 2,000 people who lived near the volcano, created a 1-km-wide caldera that filled with an acidic crater lake. Before 1982, this relatively unknown volcano was heavily forested and of no greater height than adjacent nonvolcanic peaks.