Pacific Ocean Closing?

The Pacific is the biggest ocean on Earth, but it’s getting smaller every day. Australasia and the Americas are inching closer together, and in about 350 million years the Pacific will effectively close.

That’s when plate tectonics — the process driving all that slow motion, and one that geologists have assumed to be continuous — may grind to a halt.

Plate tectonics is the movement of enormous sections of Earth’s crust—the plates. New crust forms where plates separate on the seafloor, and existing crust sinks into the mantle when a neighboring plate overrides it at what’s called a subduction zone...