Featured Article Summary #97

Nevado Ojos del Salado is a dormant volcano in the Andes on the Argentina–Chile border. It is the highest volcano on Earth and the tallest peak in Chile, reaching 6893 m above sea level. The mountain is made of overlapping lava domes and craters and covers 70 to 160 km², with little ice because the area is extremely dry. Despite the arid climate, there is a permanent crater lake about 100 m wide near the summit, the highest lake of its kind in the world, and there is almost no vegetation. The volcano was active in the Pleistocene and Holocene, mainly producing lava flows, and it was also affected by eruptions from nearby Nevado Tres Cruces, with the last known eruption around 750 CE. It can be climbed from both countries, and its height was once compared with Aconcagua, a debate that was ultimately settled in favor of Aconcagua. Ojos del Salado is named after the nearby “Río Salado” (Salty River), which a 1937 Polish expedition used to reach the mountain. The name likely comes from local words like “ojo,” meaning a spring or water source, though some people believe it refers to “salty eyes/springs” caused by mineral deposits. The mountain is also called Cerro Ojos del Salado and Nevado Ojos del Salado, and it has two summits on the Argentina-Chile border: an eastern (Argentine) and a western (Chilean) one. Ojos del Salado rises in the High Andes from the Puna de Atacama near the Atacama Desert, reaching about 4000 m on average across a remote, dry region. The Argentina–Chile border crosses its summit, and Chile Route 31 passes nearby, about 20 km north of the volcano, while most other areas are reached only by dirt roads. The volcano is dormant and the highest volcano in the world at around 6890 m, forming a complex massif with many craters rather than one single peak. Its volcanic rocks include basalt, gravel, pumice, and scoria, with lava flows and pyroclastic material building the summit area. The mountain rises roughly 2 km above the surrounding land over an oval area of about 70–160 km², with features suggesting a buried caldera and a rift-like zone with small craters. Wind erosion creates megaripple sand fields on the north side, slopes are largely covered by talus and lava above 6000 m, and permafrost is likely present at higher elevations, with some signs of mass movement. Ojos del Salado contains the world’s highest lake: a crater lake in the summit crater at about 6,480–6,500 m. It is fed by permafrost and snow, covered by geothermal fumaroles, has an area of around 6,000 m², and inflowing waters can reach about 40.8°C. On the northeastern slope, about 4 km away and at 5,900 m, there are two smaller lakes (about 2,500 m² each) that are likely very shallow. Between roughly 5,900 and 6,000 m, temporary meltwater ponds can form but may freeze permanently, and they could shrink or disappear as permafrost thaws with climate change. The area is dominated by many young volcanoes, among the highest volcanic regions in the world, with conical shapes and summit craters. Because of its stark, rocky look, travellers have compared it to a “moonscape,” and there are hot springs such as Termas Laguna Verde on the shore of Laguna Verde. Ojos del Salado sits in a long east–west chain of volcanoes that acts as a drainage divide, which scientists link to a tectonic lineament possibly caused by the subduction of the Copiapó Ridge, though its exact position may vary.