The world’s oceans and continents sit on 15 major blocks that move and shift, called tectonic plates, that make up the lower crust and upper mantle.

Junlin Hua, a postdoctoral fellow at the Jackson School of Geosciences at the University of Texas at Austin, was studying seismic images of Earth’s mantle located beneath Turkey for his doctoral research when he spotted signs of partly molten rock.

Scientists had previously spotted parts of this rock layer and thought it to be an anomaly, but Hua and his fellow researchers found evidence that it had a broader presence.

The main challenge of studying Earth’s internal layers is gathering the data because most of it can only be collected at the surface, and it’s difficult to directly sample the planet’s interior, Hua said.

By analyzing the data, Hua saw how the seismic waves moved through the different materials beneath Earth’s crust, including changes in speed, direction and time of arrival at the detection sites.

“Ultimately, it provides evidence that other factors such as temperature and pressure variations can control the strength of the asthenosphere and make it weak enough for plate tectonics to be possible.”