Researchers have identified a hitherto unknown layer of partially molten rock under the earth’s crust.

The discovery could help scientists learn more about the movements of tectonic plates, which are responsible for earthquakes on the planet, the formation of mountains and the formation of the chemical and physical properties of the environment.

The outermost layer of the planet is the earth’s crust on which we live. Below this is the Earth’s mantle, outer core, and inner core. Oceans and continents lie atop 15 major tectonic plates that span the lower crust and upper mantle.

The new layer, discovered by PhD researcher Junling Hua of the University of Texas School of Geosciences, lies 161 km below the Earth’s surface.

Hua was studying seismic maps of part of the earth’s mantle under Turkey when he noticed the first traces. In the past, scientists have identified parts of this rock layer, thinking it is a local anomaly, but Hua and his team have shown that the layer was widespread.

Scientists have confirmed that the Earth’s asthenosphere (a zone of the globe at a depth of 30 km to 700 km) consists of both solid and molten rock. Part of the molten rock does not affect the movement of tectonic plates. “Its effect on the mantle flow is very small,” Hua explains.

Seismic activity analysis

The biggest difficulty in studying the Earth’s interior is collecting data, because most of the evidence can only be gathered from the surface indirectly. Hua adds that collecting samples from the planet’s interior is difficult.

“For this reason, scientists use the seismic waves generated by earthquakes and travel inside the Earth, studying the propagation velocity in the inner layers.” The process is reminiscent of “computed tomography in a hospital,” Hua comments.

His team collected more than 700 seismograph images from around the world and created a global map of the asthenosphere. By analyzing the data, he looked at how seismic waves travel through various materials under the earth’s crust and measured changes in speed, direction, and detection time.