Major discovery in one of Earth’s most inaccessible regions: Six mysterious structures detected

About 2,900 kilometers below Earth’s surface, scientists have traced six regions that had not previously been mapped in detail. They did not reach them through drilling or direct observation. Instead, they followed the vibrations generated inside the planet by major earthquakes.

Chinese researchers used seismic waves to examine the boundary between the mantle and the outer core, one of Earth’s most inaccessible regions. The study, published in JGR Solid Earth, says the data point to previously undetected large-scale heterogeneity in the lowermost mantle.

Earth’s interior can be broadly divided into the crust, the much thicker mantle and the core. At the depth examined in the study, solid but extremely hot and dense mantle meets the liquid outer core. The outer core consists mainly of liquid iron and nickel, whose movement plays an important role in generating Earth’s magnetic field. The mantle appears solid, but it can move extremely slowly over millions of years.

The meeting point between these layers involves major changes in temperature and density. The temperature difference along the boundary is thought to reach about 1,000 degrees. These conditions drive constant movement deep inside Earth, including huge upward flows of very hot mantle material known as mantle plumes. Scientists also link these movements to volcanic activity nearer the surface.

Earthquakes provide the way to study structures that cannot be seen directly. Seismic waves travel through the planet and change speed and direction as they pass through different layers. By analyzing those changes, researchers can investigate whether deep regions contain structures with properties unlike the surrounding material.