Ojos del Salado

Nevado Ojos del Salado is an active stratovolcano in the Andes on the Argentina–Chile border and the highest active volcano in the world at . It is also the second highest mountain in both the Western Hemisphere and the Southern Hemisphere behind Aconcagua at approximately 7,000 meters (23,000 ft) and it is the highest in Chile.
Due to its location near the Atacama Desert, the mountain has very dry conditions, with snow usually remaining on the peak only during winter, though heavy storms can cover the surrounding area with a few feet of snow even in summer. Despite the generally dry conditions, there is a permanent crater lake about in diameter at an elevation of on the eastern side of the mountain. This is most likely the highest lake of any kind in the world.
The ascent of Ojos del Salado is mostly a hike until the final section to the summit, which is a difficult scramble that may require ropes. The first ascent was made in 1937 by Jan Alfred Szczepański and Justyn Wojsznis, members of a Polish expedition in the Andes.
An international highway between Chile and Argentina runs north of the mountain.
Name.
"Nevado" ("permanently snowbound') is a toponym sometimes used for stratovolcanoes. "Ojos del Salado" could be translated as "Eyes of the Salty One"; it comes from the enormous deposits of salt that, in the form of lagoons or “eyes”, appear in its glaciers.
Geology and geomorphology.
Regional.
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 of the Nazca Plate beneath the South America Plate became increasingly shallower, and this caused volcanism to shift from the Maricunga Belt to the Ojos del Salado region.
The Paleozoic basement crops out only northwest of Nevado Tres Cruces. Other geologic units in the region are Oligocene sedimentary units and volcanic rocks ranging from Oligocene age to less than 1.5 million years old. The area is part of a tectonic boundary between a volcanically active region north of the boundary and a less volcanically active region south of the boundary, which is also characterized by geographical differences, e.g. the presence of transverse valleys.
Local.
Ojos del Salado, like other major neighbouring mountains, is a complex of lava domes and lava flows, with the main summit surrounded by peripheral domes such as El Solo and El Fraile and many other lateral centres. Fumaroles are encountered at the summit of Ojos del Salado within a depression. Potassium-argon dating has yielded ages of 1.2 ± 0.3 million years ago and less than 1 million years ago from rocks north of Ojos del Salado.
There are glaciers on the mountain, in the crater and in the form of penitentes which reach heights of . Other reports indicate the absence of glaciers on Ojos del Salado. The melting of permafrost on the mountain nourishes several lakes, one of which, fed by a creek, lies at altitude.
Ojos del Salado is an active volcano, but the question of whether it should be considered "currently" (or "historically") active is arguable. According to the Smithsonian Institution's Global Volcanism Program, the most recent known eruption was about 1,300 years ago, an estimate with large margin of uncertainty; there is, however, some evidence for a minor ash emission in 1993, which would definitely qualify the volcano as historically active. The presence 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 erupted most recently in 1877 and is considered active.
Composition.
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.
Elevation.
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 proposed that Ojos del Salado may be higher than Aconcagua, an argument premised on old altitude surveys of questionable accuracy which assigned Ojos del Salado an elevation of , nearly higher than Aconcagua. A 1955 estimate set the elevation of Ojos del Salado at , but that was "simply [...] based on the altitude of the final camp, and the hours of ascent to the summit." In 1956 the first Chilean expedition, led by the retired lieutenant René Gajardo, using a pocket pressure altimeter, measured the height of Ojos del Salado as . Compounding the inexact quality of this method is the fact that the measurement was taken when the team reached the summit in the afternoon, when air pressure generally decreases, which resulted in a reading far too high.
An expedition to the area in the 1990s claimed that nearby Monte Pissis was even higher than Ojos del Salado. Later measurements using more precise equipment showed that Ojos del Salado is about higher than Pissis; furthermore, a 2007 Chilean–Argentine–European expedition organized by Andes Magazine and Azimut 360, using even more accurate instruments and performing surveys on both Ojos del Salado and Monte Pissis, found the former to be and the latter Although this fits within recent handheld GPS surveys which have estimated the mountain to be between and , the vertical error margin of the expedition's equipment , leaves the mountain's precise altitude uncertain.
A DGPS study from Phillipe Reuter in 2007, measured Ojos del Salado as 6,891.7 meters (SIRGAS).
Ojos del Salado has two summits, one in Argentina and the other in Chile (the border between the two countries runs between the two summits). The difference in elevation of the two summits is less than 1m (less than 3 ft 3 in).
Motorized partial ascent.
Ojos del Salado has been a popular mountain for attempts to attain the highest altitude aboard a land vehicle.
The previous long-standing record altitude for a four-wheeled vehicle was set on April 21, 2007 by the Chilean duo of Gonzalo Bravo G. and Eduardo Canales Moya. Reaching an altitude of 6,688 meters (21,942 ft.) with a modified Suzuki Samurai, the duo beat the previous record of 6,646 m which had been set on March 13, 2007 by German Matthias Jeschke in a Jeep Wrangler Unlimited Rubicon.
Jeschke set the high altitude record for trucks reaching a height of 6,675 meters (21,899 ft) with a Mercedes-Benz Zetros truck on March 6, 2015. This is also a world record for a diesel-powered engine.
On April 19, 2015 Chilean Gianfranco Bianchi reached an altitude of 6,472 m (21,233 ft) with a Suzuki RMZ 450, setting the altitude record for a motorcycle.
On November 6, 2017, Matthias Jeschke, again, attempted to gain two world records, one for construction at altitude and the other by beating the then current 6,688 m record. A refuge hut was built at 6,100 m (a record), but on December 19 it was announced the altitude record attempt had been called off at a height of 6,150 m for a combination of factors including an insurmountable rock barrier and adverse weather conditions.
On December 13, 2019, a 10-person team led once again by Matthias Jeschke finally succeeded in breaking long-standing record. They reached an altitude of 6,694 m (21,962 ft) in a modified Mercedes-Benz Unimog U 5023. It was part of an expedition to set up an emergency radio system on top of the volcano.