Scientists Uncover Secrets of Earth’s Deepest Layer

For decades, the enigmatic “D” layer,” nestled thousands of kilometers beneath our feet, has puzzled researchers. Now, a team has unlocked its mysteries, revealing how this region shapes seismic waves, providing a new perspective on the Earth’s inner workings.

Unveiling the D” Layer’s Secrets

To explore Earth’s depths, scientists typically rely on seismic waves generated by earthquakes. These waves offer a glimpse into the planet’s interior, allowing researchers to infer the composition of materials deep underground. A team of researchers, led by Motohiko Murakami, has pinpointed a key aspect of the D” layer, approximately 2,700 kilometers below the surface. They’ve discovered that the layer doesn’t behave as either liquid or solid rock, but as a flowing solid.

“We finally found the last piece of the puzzle,”

—Motohiko Murakami, ETH Zurich Professor

The U.S. Geological Survey records thousands of earthquakes each year, many of which originate deep within the Earth, providing the data needed to study these phenomena (USGS 2024).

How the D” Layer Works

The investigation showed that in the D” layer, crystals of post-perovskite, a mineral found under extreme pressure, align, impacting seismic wave speed. Solid rock flows slowly and horizontally at the base of the mantle. This motion, researchers suggest, resembles the movement of boiling water in a pan.

Implications for Earth Science

This revelation not only illuminates the D” layer’s behavior but also broadens our understanding of Earth’s dynamics. Murakami emphasizes that their findings demonstrate the planet’s activity extends far beneath the surface. This knowledge fundamentally alters our comprehension of the Earth’s interior, revealing a dynamic environment deep within.