Unlike the Spanish, who traded much of their silver and gold to China, the Inca used precious metals for decoration and ritual items, says Kendall Brown, a historian at Brigham Young University. They created jewelry and lavishly decorated sacred places, such as the Temple of the Sun in Cusco and the Temple of the Moon near Machu Picchu, whose walls were covered with sheets of gold and silver.
However, by the 1570s, the Inca and Spanish ran out of the high-quality ore required for smelting, and silver production crashed. But soon a new method of refining silver made its way to South America from Spaniards living in Mexico. “Up until this time, a lot of the technology had been indigenous technology,” says Brown. “But now it becomes Spanish technology.”
Silver amalgamation, in which ground silver ore is mixed with mercury and salt, quickly replaced the guayra in the Spanish quest to refine silver. Potosí, located in modern-day southern Bolivia, is one of the world’s largest historical mining sites. In 1565, it produced 70 tons (63,000 kilograms) of fine silver using guayras. By 1610, Potosí was consistently churning out at least 143 tons (130,000 kilograms) of silver every year using amalgamation.
The levels of chemicals related to metallurgy in the ice core gradually rose and plateaued over the next few decades, until around 1830. Then, over the next century as the Latin American Wars of Independence heated up, the amount of air pollution decreased. Much of the infrastructure for mining was demolished during many wars of independence in South America.
The Quelccaya ice cores, of course, only tell a sliver of the history of South America. “There’s always interesting new questions that these records raise,” Thompson says. What will ice cores in the next century say about our civilization — will there even be ice caps left to look at? And if not, in what other ways have we subtly marked nature with the story of mankind?
As for Atahualpa, the details of his fate can’t be found in the ice, but are instead preserved in the pages of history books. One evening in late July 1533, the great leader found himself being led back to the middle of that square in Cajamarca, the scene of Pizarro’s pivotal ambush a mere eight months earlier.
There, his Spanish conquerors allegedly converted him to Christianity — then strangled him to death and partially burned his body before giving him a full Christian burial for his people to witness. His ashes alone would leave no trace for future generations to read, but the Inca ruler’s death presaged radical changes to the culture and identity of South America — as well as the environment itself.
[This article originally appeared in print as "Freeze Frame."]