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
Seven Second Summits of at least 100 km to reach Mount Logan. In South America, Ojos del Salado involves a short scramble while Aconcagua is just a walk. Horrell acknowledged that Ojos del Salado was more technically difficult, but considered Aconcagua a greater challenge because of physical demands. Aconcagua's base camp, at 4,500 m, is accessible by mule, but from that point, climbers must carry all of their supplies to as many as three higher camps before the final ascent. By contrast, Ojos del Salado is accessible by four-wheel-drive vehicles to 5,200 m; from that point, climbers need only carry supplies to a