You don't need plate tectonics to get continental crust that looks modern, a new study finds.
Earth's crust today has a surprisingly similar composition to the planet's first outer shell, or "protocrust," new research finds. This early rocky shell featured chemical signatures previously thought to occur only in continental crusts made by the process of subduction, in which one tectonic plate slides under another. But plate tectonics isn't actually required to produce these signatures, according to the new study published April 2 in the journal Nature . These findings are important for the debate over when our planet's plate tectonics began . No one knows exactly when or why the Earth's surface broke into pancake-like slabs that grind and crash against one another, forming mountains and volcanoes and triggering earthquakes. Related: Earth's crust is peeling away under California Historically, the fact that chemical signatures seen in modern plate tectonic processes occurred in protocrust from Earth's first billion years, during the Hadean eon, had been used as evidence to support the theory that plate tectonics started nearly as soon as Earth had solid ground — roughly 4 billion years ago. "That's probably a flawed argument now," study lead author Craig O'Neill , a geophysicist at Queensland University of Technology in Australia, told Live Science. Sign up for the Live Science daily newsletter now Get the world's most fascinating discoveries…