Ojos del Salado, Nevados

Geography & Climate

Ojos del Salado, Nevados is located in Chile-Argentina, within the Central Andean Volcanic Arc of the broader South America Volcanic Regions. Situated at 27.11° S, 68.54° W in the Southern Hemisphere, the volcano lies within a subtropical climate zone. At 6,879 meters above sea level, Ojos del Salado, Nevados reaches well into the permanent snow and ice zone. Glaciers and snowpack on the upper slopes create the potential for lahars — destructive volcanic mudflows — during eruptions, as heat rapidly melts ice and snow. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Ojos del Salado, Nevados sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Chile-Argentina near Ojos del Salado, Nevados, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is dacite, an intermediate to silica-rich volcanic rock. This composition typically produces more viscous magma, leading to more explosive eruptions with ash columns and pyroclastic flows. Andesitic and dacitic magmas build pressure before erupting, which is why volcanoes with this rock chemistry are often associated with Plinian-style eruptions that can send ash tens of kilometers into the atmosphere and disrupt aviation across entire regions.

Eruption History Summary

Ojos del Salado, Nevados has 2 recorded eruptions in the geological database, spanning from 750 CE to 1993 CE. The most powerful recorded event was a gentle, effusive event in 1993 CE, reaching VEI 1 on the Volcanic Explosivity Index. These eruptions span roughly 1,243 years of volcanic history. The most recent eruption in 1993 CE places this volcano within the modern era of volcanological observation.

GVP Reference Summary

The world's highest active volcano, Nevados Ojos del Salado, rises to 6,879 m along the Chile-Argentina border. The volcano lies about 20 km south of the road that crosses the international border at Paso de San Francisco. The summit complex, which is elongated in a NE-SW direction and overlies a largely buried caldera, contains numerous craters, pyroclastic cones and andesitic-to-rhyolitic lava domes and has been the source of Holocene lava flows. A major rhyodacitic explosive eruption about 1000-1500 years ago produced pumiceous pyroclastic flows. The most recent eruptive activity appears to have originated along a NNE-trending rift along the summit complex. It involved formation of a thick, viscous lava flow and at least a dozen small cones, lava domes, and explosion craters. No confirmed historical eruptions have been recorded, but the volcano has displayed persistent fumarolic activity, and there was an unconfirmed report of minor gas-and-ash emission in 1993.

— Smithsonian Institution, Global Volcanism Program