On the Chilean--Pacific--side of the Andes, that's courtesy of the ocean and the cold Humboldt Current.

FORBES: Making a Case for South America

Normally, the coast of Peru is washed by the Humboldt current, which carries cool waters from Antarctica almost as far north as the equator.

ECONOMIST: The unkind child

The Humboldt current supports one of the world's great fisheries: despite years of over-exploitation, its plankton-rich waters teem with shoals of Pacific pilchard (anchoveta) and horse mackerel.

ECONOMIST: The unkind child

From there the crew plotted a course west, riding the Humboldt Current across the Pacific -- it would be more than three months before they saw land again.

CNN: The Kon-Tiki: Crossing an ocean on balsa