A 1994 Argentine expedition claimed —using GPS technology available at the time— that the elevation of Monte Pissis was, higher than Ojos del Salado. Ten years later, with the use of higher precision systems, several other surveys proved that those measurements were inaccurate: in 2005, an Austrian team performed a DGPS survey of Pissis' summit and found the elevation to be. In 2006 an international expedition surveyed the height on the summit, and found results in agreement with an elevation around. This was later confirmed by a 2007 Chilean-Argentine-European expedition, which surveyed both Ojos del Salado and Monte Pissis and provisionally found the former to be and the latter.
Geology
Monte Pissis is a large andesitic-dacitic volcanic centre. It was formed between 6.6 and 6.2 million years ago. Like Cerro Bonete Chico it is one of the large volcanic complexes formed at that time over a deforming Nazcaslab. Volcanism in the area ceased about 2 million years ago. Monte Pissis, Cerro Bonete Chico and Incapillo form a large volcanic complex that is among the highest in the world. Incapillo formed after Monte Pissis had ceased erupting, and hydrothermal activity at Incapillo may continue to this day.
Climbing
Until recently, this mountain had received very little attention. The first successful recorded ascent was achieved in 1937 by Polish climbers Osiecki and Szczepanski. The mountain was not climbed again until 1985. The opening of mining in the area has resulted in the construction of basic roads in the last 15 years. This has developed the tourism in the Atacama Desert and now more people ascend the mountain, usually with a previous stop in Fiambalá to organise the climb. Approaching it from neighbouring Chile is also possible but involves a longer way. As the mountain is very high and remote, a long approach is required but the ascent is easy and does not require any specific climbing skill. Nevertheless, warm clothing and good shoes are required as temperature during the night can drop as low as and winds can be very strong. Usually most teams ascend the peak during December to March, the warmest period of the year. The peak is one of the most heavily glaciated peaks in the Atacama Desert, although the glaciated area starts only at and the size of the glacier is small compared to the overall surface of the mountain. From the base of the mountain several days of hike are required. The summit is usually reached directly from a high camp at at the edge of the glacier.
