A moon-forming cataclysm could have also triggered Earth’s plate tectonics


THE WOODLANDS, TEXAS — Vestiges of a moon-forming cataclysm could have kick-started plate tectonics on Earth.

The leading explanation for the origin of the moon proposes that a Mars-sized planet, dubbed Theia, struck the nascent Earth, ejecting a cloud of debris into space that later coalesced into a satellite (SN: 3/2/18). New computer simulations suggest that purported remains of Theia deep inside the planet could have also triggered the onset o subduction, a hallmark of modern plate tectonics, geodynamicist Qian Yuan of Caltech reported March 13 at the Lunar and Planetary Science Conference.


Building off that previous work, the researchers used computers to simulate how Theia’s impact, and its lingering remains, would impact the flow of rock inside the Earth.

They found that once these hot alien blobs had sunk to the bottom of the mantle, they could have compelled large plumes of warm rock to upwell and wedge into Earth’s rigid outer layer. As upwelling continued to feed into the risen plumes, they would have ballooned and pushed slabs of Earth’s surface beneath them, triggering subduction about 200 million years after the moon formed.