Earth’s tectonic plates are weird as hell. First there weren’t any, then there was a massive shell, then there were baby continents, then supercontinents, microcontinents, regular continents, all of them shifting around the Earth’s crust and changing its appearance, like a very slow inkblot test.
Now, it appears they’re set to get even stranger. A team of researchers – led by the University of Houston – has concluded that, beneath our world’s tectonic plates, there’s another separate layer of independent plates doing their own thing.
Speaking at a joint conference between the Japanese and American Geophysical Unions in Tokyo this week, the team say that they’ve been using seismic waves to peer beneath the crust. These waves travel at different speeds through different materials, and as such, researchers can use them to find out what’s beneath their feet.
Their research uncovered a mysterious layer present beneath Japan, Korea, and Northeast China, as well as beneath the island of Tonga. They’re definitely composed of the same material as modern tectonic plates, but they’re found incredibly deep within the mantle. So what are they?
The tectonic plates we’ve all come to know and love – well, except creationists we suppose – are found within the lithosphere, the outer shell of a rocky planet, including ours. They are composed of the crust – whether that’s the less dense continental variety or the dense, submarine oceanic flavor – and the upper mantle, a layer of slowly moving, superheated solid rock called the “asthenosphere”.
This causes them to drift around, bang into each other, grind past each other, and sometimes even destroy each other. That, in essence, is where we were at as of 2017.
However, this new research suggests that beneath the seven/eight major tectonic plates resides another layer of them. They appear to be vast, continental-sized segments of ancient plates gliding fairly quickly around a transition zone 440-660 kilometers (about 273-410 miles) beneath the surface.