How Scientists Discovered the Presence of Mysterious Donut at the Edge of Earth’s Core

Giant Donut Emerges From the Core of Earth

A study published in Science Advances confirmed the existence of a giant donut-shaped structure in the molten metal at the edge of Earth’s core. Prof. Hrvoje Tkalčić, a geophysicist from the Australian National University, told The Guardian , "Because scientists could not reach the core with current technology, the team analyzed the patterns of seismic waves generated by large earthquakes as they traveled through it." Here's how Prof. Tkalčić and Dr. Xiaolong Ma discovered this structure by examining the faint traces left by seismic waves long after the initial earthquake.

Mystery of the Donut-Shaped Region

The scientists discovered a ring-like structure within the Earth's outer core by studying seismic waves. Prof. Tkalčić explained that these waves slowed down in a specific area near the core-mantle boundary. Upon examination, they found that the waves passed through a region shaped like a torus, which is also similar to a donut. He further told The Guardian , "We didn’t know the exact thickness of the donut, but we inferred that it reached a few hundred kilometers beneath the core-mantle boundary." The structure also suggested that it might have contained lighter elements such as silicon, sulfur, oxygen, hydrogen, or carbon.

Coda-Correlation Wavefield Explains the Shape

Researchers used a method called the 'coda-correlation wavefield' to study the weaker part of seismic waves, known as the coda. They compared these waves from different parts of the Earth and found that signals from the equator differed from those at higher latitudes. The donut-like shape of the formation was not completely spherical and turned out to be more complex, according to Indy100 . Knewz.com noted that this formation was located near the equator, where waves traveled more slowly compared to near the poles.

Studying the Earth's Outer Core

With a radius of about 3,480 km, the Earth's outer core was much larger than that of Mars. The outer core was mostly made of iron and nickel, with smaller amounts of lighter elements such as silicon, oxygen, sulfur, hydrogen, and carbon, according to ScienceAlert . The bottom of the outer core was hotter than the top, allowing the liquid metals to move. Scientists believed that the lighter elements in the donut-like structure were related to how heat was transferred to the mantle above.

The Concept of 'Geodynamo'

The Earth was made up of four main layers, which are the surface crust, the partly melted mantle, a liquid metal outer core, and a solid metal inner core. The donut-shaped structure sat at the top of the liquid outer core and contained lighter elements. When the Earth rotated, the liquid metal formed giant vertical vortices, creating the 'geodynamo' responsible for generating Earth's magnetic field. Prof. Tkalčić explained to The Daily Mail , "These light elements, alongside temperature differences, helped stir the liquid in the outer core. Our results could promote more research on the magnetic field of both Earth and other planets." Without the magnetic field, the planet's surface would have faced constant attacks by charged particles from the sun, which could have destroyed life on Earth.