Due to its location near the Atacama desert, the Ojos del Salado has very dry conditions with snow only remaining on the peak during winter. Despite the generally dry conditions, there is a permanent crater lake about 100 metres (300 ft) in diameter at an elevation of 6,390 m (20,960 ft) on the eastern side of Ojos del Salado. This is most likely the highest lake of any kind in the world.
The ascent of Ojos del Salado is mostly a hike except for 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 Szczepanski and Justyn Wojsznis, members of a Polish expedition in the Andes. Its name comes from the enormous deposits of salt that, in the form of lagoons or “eyes”, appear in its glaciers.
Ojos del Salado is a recently active volcano. The most recent known eruption was around 1300 years ago. However, there is also 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."
The first men to successfully climb Ojos del Salado were Polish mountaineers Jan Alfred Szczepanski and Justyn Wojsznis, getting to the summit on February 26, 1937.