Ojos del Salado Spanish, comes from the enormous deposits of salt that, in the form of lagoons or “eyes”, appear in its glaciers. An international highway between Chile and Argentina runs north of the mountain. Ojos del Salado along with several other high volcanoes such as El Muerto, El Solo, Nevado Incahuasi and Nevado Tres Cruces lies at the southern end of the Central Volcanic Zone of the Andes. Volcanic activity in the region commenced 26 million years ago in the Cordillera Claudio Gay, at the same time as the neighbouring Maricunga Belt volcanoes were active. Starting 18 million years ago, local subduction
Ojos del Salado of fumaroles high on the mountain and recent-looking lava flows, albeit of uncertain age, also argues in favor of a categorization as "active." By these definitions, Ojos del Salado is the highest historically active volcano on Earth. If the older date is accepted, the title of "highest historically active volcano" might reside instead with the somewhat lower Llullaillaco volcano, which certainly has erupted in historic times (most recently in 1877) and is considered active. Salado's rock is predominantly potassium-rich dacite and rhyodacite. Its lavas are high in biotite, hornblende, plagioclase, and opaques, with lower levels of augite, quartz, and hypersthene.