Ojos del Salado The elevation of Ojos del Salado has been the subject of debate. The mountain is hidden behind other peaks and thus its height was not appreciated in early research until 1937, when the mountain was climbed by Polish climbers. A 2006 article in Andes Magazine offered that Ojos del Salado may be higher than Aconcagua, although the argument was premised on older, less accurate altitude surveys. The results of these older surveys assigned Ojos del Salado an elevation of , which would have made it nearly higher than Aconcagua. As early as 1955, an estimate was made that the elevation
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.