Complexity catalyst: Banded iron formations, such as these found in Ontario, Canada, show the chemical features of ancient seawater when they formed in iron-rich oceans billions of years ago.
Credit: Stefan Lalonde
"The timing fits very well. The drop in nickel could have set the stage for the Great Oxidation Event," said Papineau.
But that still left one key question unanswered: what caused the nickel levels to decline?
The researchers point to geological changes. During earlier phases of Earth's history, when the layer known as the mantle was still hot, lava from eruptions flowing into the oceans were very rich in nickel. But as the mantle cooled, the lava contained far less of the trace metal.
"The nickel connection was not something anyone had considered before," said Papineau. "It's just a trace element in sea water, but our study indicates that it may have had a huge impact on the Earth's environment and on the history of life."
