silicate — formed during the growth spurt around 3 billion years ago.
"There have probably been multiple crust-forming events in the Earth's history," lead researcher Chris Kirkland, a professor of geoscience at Curtin University in Australia, told Live Science.
"But this global injection event 3 billion years ago is definitely one of the biggest."
Continental seeds
Before this massive growth period, Earth's ancient crust was much thinner and weaker than it is today. Eventually, it broke apart into crustal fragments that served as floating "life rafts" from which new crust could grow.
"We think of crust as this buoyant material that sits on top of the mantle," Kirkland said. "This means it constantly gets an injection of new material coming from below. The longer it sits on top, the more new material is injected into it and the larger it becomes."