A series of ancient subduction zones could have existed in the palaeo-Pacific Ocean about 200 million years ago, reports a study published online this week in Nature Geoscience. Douwe van der Meer and colleagues compiled geological data stored in rocks found along the margins of the North American and Asian continents. The data show that the rocks originally formed above ancient subduction zones located somewhere in the middle of the Pacific Ocean, around 200 million years ago. Furthermore, seismic images of the mantle beneath the Pacific Ocean identify potential remnant slabs of Earth’s rigid outer shell that could have been forced into the mantle at the subduction zones, and have since lingered there for hundreds of millions of years. Together, the two independent data sets mark out the location of a north?south trending series of subduction zones that would have divided the palaeo-Pacific Ocean into two sub-basins.