Plate tectonics began somewhere between 3 and 3.5 billion years ago, and as result, Planet Earth became a world full of volcanoes, earthquakes, oceans, and continents. We understand the processes that drive it, but how did it all begin?
A new Nature Geoscience study has a rather remarkable answer: massive asteroid and meteorite impacts kickstarted the formation of mountains, valleys and everything in between. They may have even helped trigger the formation of our planet’s magnetic field, without which life on Earth would all but cease to exist.
The international study, led by researchers at Macquarie University (MU), looked further back in geological time than most, right to the beginning of our planet, 4.5 billion years ago. Shortly after the planet formed from the embers of the Solar System’s violent birth, it developed a shell – a singular crust – that covered the entire world.
Then, between 4.1 to 3.5 billion years ago, the remnants of failed planets and comets began to rain down on the larger worlds out there, including our own. This was known as the Late Heavy Bombardment, and the team wanted to know if it had any effect on plate tectonics.
Setting up a cutting-edge computer model of the Hadean eon Earth, the team simulated several massive impacts on the crusted-over, superheated planet – including one proto-planetary body that was 1,700 kilometers (1,056 miles) across.
“Our results indicate that giant meteorite impacts in the past could have triggered events where the solid outer section of the Earth sinks into the deeper mantle at ocean trenches,” lead author Associate Professor Craig O’Neil, from MU, said in a statement.
The process being described there is subduction, the very same process that leads to the destruction of tectonic plates, the formation of mountains, volcanoes, and the world’s most powerful earthquakes. Tectonic plates can’t drift around if older ones aren’t being destroyed, which means that the very first moment that subduction occurred, plate tectonics officially began.