Geology of Chile the Taitao Peninsula, the Peru–Chile Trench subduction zone is the boundary between the South American and Nazca Plates. At Taitao, the Chile Triple Junction and the Nazca Plate subduct the South American Plate. In Norte Grande the mountains form a series of plateaus, such as Puna de Atacama and the Altiplano. At a south latitude of 27 degrees, Chile's highest mountain (Ojos del Salado) reaches a height of . Below 42 degrees south, the Andes split into a fjord landscape and the highest mountain is Monte San Lorenzo at . As the mountains ebb, the snow line lowers; in the
Ojos del Salado of Ojos del Salado was , but that was "simply [...] based on the altitude of the final camp, and the hours of ascent to the summit." In 1956, the first Chilean expedition led by the retired lieutenant René Gajardo measured the height of Ojos del Salado as with a pocket pressure altimeter. Apart from being an inexact method, the height shown by the altimeter was far too high as air pressure is generally lower in the afternoon, the time at which the team reached the summit. An expedition to the area in the 1990s claimed that nearby Monte Pissis