The world's highest volcano at 6,893 meters, with a permanent crater lake near its summit. It last erupted around 1,300 years ago. Its next eruption could threaten thousands.
sergejf, CC BY-SA 2.0, via Wikimedia Commons
A high-altitude volcanic complex
Nevado Ojos del Salado is a stratovolcano, a large, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Straddling the border of Chile and Argentina, it is the highest active volcano on Earth, with a summit elevation of 6,893 meters (22,615 feet). This makes it the second-highest mountain in both the Western and Southern Hemispheres, surpassed only by Aconcagua, which is 6,961 meters tall. The volcanic complex is not a single peak but a collection of overlapping lava domes and craters spread over an area of up to 160 square kilometers.
The volcano's rock composition is primarily dacitic, with some andesite and rhyodacite. These are types of volcanic rock that are rich in silica. The lavas contain minerals such as plagioclase, hornblende, biotite, and augite. Geologically, Ojos del Salado is located in the Central Volcanic Zone of the Andes, a region formed by the subduction of the Nazca Plate beneath the South American Plate. Volcanic activity in this area began around 26 million years ago.
Despite its great height, the mountain's location near the Atacama Desert results in extremely arid conditions, which prevent the formation of large glaciers. Snow cover is typically present only during the winter. The last confirmed eruption occurred around 750 CE. However, fumarolic activity, the emission of steam and volcanic gases, persists, and a possible steam emission was reported in November 1993, confirming its status as an active volcano.
The world's highest lake
A permanent crater lake exists near the summit of Ojos del Salado, at an elevation between 6,480 and 6,500 meters (21,260–21,330 feet). This body of water, approximately 100 meters (330 feet) in diameter, is the highest known lake of any kind in the world. The lake is fed by melting permafrost and surrounding snowfields and is located near active fumaroles. The water in streams feeding the lake can reach temperatures of 40.8°C (105.4°F).
This high-altitude aquatic environment is a subject of scientific study for its extremophile inhabitants. Researchers have found salt, acid, and cold-tolerant bacteria in the lake's sediments. These microorganisms are adapted to a unique combination of environmental stressors: low temperatures, acidic water (pH as low as 2.08), high solar radiation, and low oxygen. Bacterial communities identified include iron-oxidizing species like Ferrithrix and sulfur-processing bacteria such as Hydrogenobaculum. The study of these life forms shows the potential for life in similar harsh environments on other planets, such as Mars.
💡Fun Facts
The name Ojos del Salado translates to "Eyes of the Salty One," likely referring to the large, eye-like salt deposits and lagoons that form on its slopes.
It is the second-highest mountain in the Western Hemisphere, only about 68 meters (223 feet) lower than Aconcagua.
In December 2023, a modified Porsche 911 set a world altitude record for a wheeled vehicle by driving to 6,734 meters (22,093 feet) on the volcano's western ridge.
Due to the extreme altitude, the air density at the summit is only about half of what it is at sea level.
Accessible year-round, but the main climbing season is from November to March.
Admission
A permit from the Chilean government (DIFROL) is required for climbing from the Chilean side. Expedition costs with guide services typically range from $3,900 to $4,500 USD.
Accessibility
This is a remote, high-altitude expedition. Reaching the base requires a 4x4 vehicle. The ascent is a non-technical hike for most of the route, but the final section involves a difficult scramble on rock that requires ropes and mountaineering experience.
