Chacaltaya (Aymara for "cold road") is a mountain in the Cordillera Real, one of the mountain ranges of the Cordillera Oriental, itself a range of the BolivianAndes. Its elevation is 5,421 meters (17,785 ft). Chacaltaya's glacier — which was as old as 18,000 years — had an area of 0.22 km2 (0.085 sq mi) in 1940, which had been reduced to 0.01 km2 (0.0039 sq mi) in 2007 and was completely gone by 2009. Half of the meltdown, as measured by volume, took place before 1980. The final meltdown after 1980, due to missing precipitation and the warm phase of El Niño, resulted in the glacier's disappearance in 2009. The glacier was formerly one of the highest in South America, located about 30 kilometers (19 mi) from La Paz, near Huayna Potosí mountain.
Enhanced image of Chacaltaya ski resort, November 2007
The glacier on Chacaltaya served as Bolivia's only ski resort. It was the world's highest lift-served ski area and the northernmost in South America as well as the world's second most equatorial after Maoke, Indonesia. The rope tow, the very first in South America, was built in 1939 using an automobile engine; it was notoriously fast and difficult, housed in the site's original clapboard lodge, and is now inoperable. The road to the base of the 200-meter (660 ft) drop is reached by a narrow road, also built in the 1930s. Traditionally, due to the extreme cold weather, the lift operated exclusively on weekends from November to March. This summer skiing is no longer possible following the unexpectedly early melting of the glacier. As of 2009, skiing is restricted to a 600-foot (180 m) stretch that sometimes receives sufficient snowfall for a run during the winter. The mountain is also popular with amateur mountaineers, as the aforementioned road stops only 200-metre (660 ft) from the summit.
The Mount Chacaltaya Laboratory began as a weather station in 1942. Located at 5,270 meters (17,290 ft), the Chacaltaya Astrophysical Observatory (Observatorio de Física Cósmica) of the Universidad Mayor de San Andrés is operated in collaboration with other universities worldwide. It is an important site for gamma ray research.
Scientists at the Mount Chacaltaya Laboratory started measuring the Chacaltaya glacier in the 1990s. Predicted at that time to survive until 2015, the Chacaltaya glacier has melted at a much faster rate than expected. The 18,000-year-old glacier has been reduced in recent years to just a few small patches of ice and snow near the top of the mountain.
Many Bolivians on the Altiplano and in two of Bolivia's main cities — La Paz and El Alto — depend on the partial melting of Andean glaciers for their water supply during the dry season. The World Bank has warned that many glaciers in the tropical portion of the Andes are expected to disappear within 20 years. This will threaten the water supplies of nearly 80 million people as well as the future generation of hydropower. Bolivia, Ecuador and Peru depend on hydropower for about half their electricity.