Ancient Fragment of the Pacific Ocean Found Buried 400 Miles Below China
By By Peter Dockrill | ScienceAlert

November 18, 2020 | Scientists have identified an old piece of the Pacific Ocean – the ancient remains of its long-ago seabed – extending hundreds of miles underneath China, as it is pulled downward into Earth’s mantle transition zone.

(Image: © Matthias Kulka via Getty Images)

This rocky slab that used to line the bottom of the Pacific is a relic of the oceanic lithosphere, the outermost layer of Earth’s surface, composed of the crust and the solid outermost parts of the upper mantle.

The lithosphere isn’t always destined to enjoy the views up top, however. The upper surface layer is composed of several fragmented tectonic plates, which slowly move and shift around at the surface, occasionally running into each other.