About 252 million years ago, the world came very close to ending when the vast majority of species on the planet winked out of existence in an event known euphemistically as "The Great Dying." Somehow, very violently, the period known to scientists as the Permian ended and the Triassic began, ushered in by a bang.
Recently, scientists have argued that the bang in question was the violent release of lava over a huge stretch of Russian land known as the Siberian Traps during a flood basalt eruption—a class of eruption which pours out 200 billion gallons of molten rock, at a bare minimum.
"We're looking for something catastrophic," Michael Rampino, a geologist at New York University, told Newsweek, noting that whatever caused the extinction seems to have happened quickly. The Siberian Traps, which is the largest stretch of land on the planet that can host flood basalt eruptions, certainly fit that description. But although scientists had established that they erupted at just about the time of the Permian extinction, they hadn't found a fingerprint of the eruption in rock around the world.
That's very different from the other main culprit of mass extinctions, large asteroid strikes like the one that finished off the dinosaurs almost 200 million years after the Great Dying. Asteroid strikes leave telltale stripes of iridium and other geologic signatures that scientists can easily identify.
Rampino wanted to isolate a similar fingerprint for the Siberian Traps eruption. In a new paper published in the journal Scientific Reports, he and his colleagues point to a sudden spike in nickel found in rocks from Japan, Hungary, India, and Israel, about 3,500 miles away from the eruption site. That's much farther than the lava itself traveled—in fact, some scientists believe lava didn't even need to fully escape Earth's crust in order to wipe out species.
The nickel itself wasn't responsible for the extinction event—that was caused by the huge amount of sulfur dioxide and carbon dioxide release into the atmosphere, first cooling Earth by a few degrees (and causing acid rain), then warming it by about 14 degrees Fahrenheit.
But while those chemicals definitely cause global impacts (welcome to climate change), they don't leave their traces for geologists to find. "I think we have found a nice marker, especially for the Siberian Traps," Rampino says.
It's not clear yet if the nickel fingerprint is a reliable indicator of large-scale flood basalt eruptions generally. It may also be a result specifically of the chemistry of the Siberian Traps, where lava tends to be high in nickel anyway. Rampino intends to find out by looking for similar nickel spikes in the geologic record.