The dominant theory for the birth of the moon argues that a planet around the size of Mars, named Theia, collided with the young Earth, ejecting a cloud of debris into space that subsequently solidified into a satellite (SN: 3/2/18). During the Lunar and Planetary Science Conference on March 13, Caltech geodynamicist Qian Yuan stated that new computer models show that supposed relics of Theia buried deep under the globe may have also caused the beginning of subduction, a characteristic of current plate tectonics.
The narrative provides a coherent account for how Earth acquired both its moon and its moving tectonic plates, and it might assist in the hunt for other Earth-like planets. Others, though, caution that it is far too early to conclude that this actually occurred.
Earth’s plate tectonics may have been initiated by the remnants of a moon-forming catastrophe.
Our planet is the only one on which plate tectonics has been verified (SN: 1/13/21). Throughout the course of billions of years, the Earth’s plates have expanded, clashed, and sunk beneath one another, creating and separating continents, raising mountain ranges, and enlarging seas (SN: 4/22/20, SN: 1/11/17). All of this reworking, however, has eliminated the majority of traces of the planet’s early history, including when and how plate tectonics began.
To explain the beginning of subduction, a tectonic process in which one plate moves beneath another, several ideas have been offered (SN: 5/2/22; SN: 6/5/19; SN: 1/2/18). Yuan and his colleagues selected to focus on two huge low-shear velocity areas in the Earth’s lower mantle (SN: 5/12/16) that are the size of continents. These are places where seismic waves are known to move at an abnormally slow rate. Previously, researchers have theorized that these zones may have developed from ancient, subducted plates. But, in 2021, Yuan and his colleagues argued that the mystery masses may represent the thick, submerged remains of Theia.
The researchers utilized computers to model the effect of Theia’s impact and leftover debris on the movement of rock within the Earth.
After these hot alien blobs had fallen to the bottom of the mantle, they might have caused enormous plumes of heated rock to rise and wedge into the stiff outer layer of the planet. As upwelling continued to feed the rising plumes, they would have expanded and pushed slabs of Earth’s surface beneath them, initiating subduction some 200 million years after the formation of the moon.
Although models imply that huge low-shear velocity provinces may have had a role in initiating subduction, it is not yet known if these masses originated from Theia. “The characteristics… are a very new discovery,” said geodynamicist Laurent Montési of the University of Maryland, College Park. These are really intriguing formations whose origin is unknown. In light of this, he believes it is premature to assert that Theia triggered plate tectonics.
It provokes thought. Large low-shear velocity provinces, as described by Montési, contain a unique substance. “But, I do not believe the argument has been established that it must be initially alien.”