Ojos del Salado

Nevado Ojos del Salado is a massive, dormant complex volcano located in the Andes mountains. It sits directly on the international border between Argentina and Chile. This mountain is a geological marvel because it is the highest volcano on Earth. It also holds the title of the highest peak in Chile.

The mountain is not a single, simple cone. Instead, it is a complex massif made of many overlapping parts. This structure includes lava domes, lava flows, and more than 20 different craters. The entire volcanic area covers an oval shape of about 250 square kilometers.

The volcano forms through a process called subduction. This occurs within the Central Volcanic Zone, where tectonic plates move against each other. Specifically, the Nazca Plate and Antarctic Plate subduct beneath the South America Plate in the Peru-Chile Trench. As these plates slide under one another, they release fluids into the mantle. These fluids trigger the formation of melts, which are pools of molten rock. This melted rock then ascends toward the surface to create volcanic activity.

On Ojos del Salado, thick dacitic lava flows form the core of the mountain. The summit area is also covered by pyroclastic fall material, which is rock debris from eruptions.

Ojos del Salado features several distinct geological structures. The summit is divided into two peaks: the eastern or Argentine summit and the western or Chilean summit. These names depend on which country the peak is easier to reach from. The mountain also appears to contain a buried caldera. A caldera is a large depression formed when a volcano collapses after a major eruption. The rim of the volcano contains basalt, gravel, pumice, and scoria. On the western flank, large lava domes known as Cerro Solo and El Fraile produced pyroclastic flows.

Exploration of this high-altitude region began in the early 20th century. A Polish expedition led by Jan Alfred Szczepański made the first successful ascent in 1937. The expedition named the mountain after the Río Salado, or Salty River, which they used to reach the site. During the mid-20th century, a significant scientific debate occurred regarding the highest point in South America. Experts argued whether Ojos del Salado or Aconcagua was taller. This debate was eventually resolved in favor of Aconcagua.

The mountain reaches a massive altitude of 6,893 meters above sea level. Because it is located near the Arid Diagonal of South America, the climate is extremely dry. This aridity prevents the formation of large glaciers or permanent snow cover. However, the mountain hosts the highest lake in the world. This crater lake is located within the summit crater at an elevation of 6,390 meters. The lake is about 100 meters in diameter and is fed by snowfields and permafrost.

Despite the desert conditions, the mountain displays unique frozen phenomena. One notable feature is the presence of penitentes. These are tall, thin ice spires that form on the slopes. They are created through sublimation, which happens when intense sunlight turns ice directly into water vapor.

Much of the mountain's ice is actually buried beneath sand and gravel. This subsurface ice is vital because the covering acts as insulation. This insulation slows the retreat of the ice as the climate changes. The ground at higher elevations also contains permafrost, which is soil that remains frozen.

Ojos del Salado is part of a much larger volcanic system. It sits at the southern boundary of the Central Volcanic Zone. This zone is part of the Pacific Ring of Fire, a massive area of volcanic activity around the ocean. The landscape surrounding the volcano is dominated by other young volcanoes. Many travelers describe the entire region as a "moonscape" due to its desolate appearance.

This high-altitude environment remains a critical site for studying how volcanoes and ice interact in dry climates.