A new map of the seafloor off the coast of Iberia—the region of Europe that includes Portugal and Spain—has revealed what could be the birth of a new subduction zone.

Subduction zones happen when tectonic plates—the large rock slabs that make up the Earth’s crust—crash into one another. The edge of the heavier plate slides, or subducts, below the lighter plate. It then melts back into the Earth’s mantle—the layer just below the crust.

The discovery of this new subduction zone … could signal the start of an extended cycle that fuses continents together into a single landmass—or “supercontinent”—and closes our oceans.

Via National Geographic.