In the pulsating heart of our planet, where temperatures exceed those of the surface of the sun, researchers have made a discovery that “tastes sweet”: a doughnut-shaped structure. But don’t let its familiar shape fool you: This geological revelation could revolutionize our understanding of Earth.
A Journey to the Center of the Earth
Imagine taking a journey to the center of our planet. You would first travel through the Earth's crust, then through the mantle, until you reach the liquid outer core. It is here, thousands of kilometers beneath our feet, that a team of scientists from the Australian National University (ANU) has made a surprising discovery.
Professor Hrvoje Tkalcic, a geophysicist at ANU and one of the authors of the study (that I link to you here), explains: “We have identified a doughnut-shaped region at the top of the outer core, right where it meets the mantle.” This structure, which extends parallel to the equator, is not visible to the naked eye (obviously), but was revealed thanks to a groundbreaking analysis of seismic waves.
A new approach
Traditionally, geologists study seismic waves generated by earthquakes in the first hours after the event. The ANU team decided to look further, analyzing the waves that appear many hours after the earthquake.
“It's like hearing the echo of a sound in a cave,” explains Dr. Xiaolong Ma, co-author of the study. “These late waves allowed us to ‘see’ previously hidden structures in the Earth’s core.”
This innovative approach allowed researchers to observe the waves as they passed through the Earth's outer core, leading to the discovery of this unique geological structure.
A 'geological donut' of light elements
But what makes this region so special? Professor Tkalčić explains that in this area seismic waves move more slowly than in the rest of the outer core. This difference in speed suggests a unique composition.
“We believe this region contains a higher concentration of light elements,” says Tkalčić. “We don’t know the exact thickness of this ‘doughnut,’ but we think it extends a few hundred kilometers below the core-mantle boundary.”
Implications for the Earth's magnetic field
The discovery of this structure is not just a geological curiosity. It could have fundamental implications for our understanding of the Earth's magnetic field, essential for life on our planet.
The outer core, composed mostly of liquid iron and nickel, generates the Earth's magnetic field through the movement of its electrically conductive liquid. This magnetic field is crucial to life on Earth, protecting us from solar winds and harmful radiation.
The presence of this donut-like structure could explain some of the mysteries of the magnetic field. Understanding the composition of the outer core, including the presence of light elements, is essential for scientists to better understand the dynamics of the magnetic field.
The light elements, together with temperature differences within the core, play a key role in mixing the liquid in the outer core, thus influencing the magnetic field.
“Our findings suggest that the slower seismic waves in this region could be due to a higher concentration of light elements,” says Professor Tkalčić. “This is important because the magnetic field is a critical factor in supporting life on Earth.”
The future of geological research
This geological discovery not only sheds new light on the inner workings of our planet, but could also have implications for the study of other planets. The research team hopes that their discovery will encourage further studies on magnetic field, not only on Earth but also on other celestial bodies.
The donut-shaped structure in the Earth's core is more than a geological curiosity: it's a window into the fundamental processes that make our planet unique and habitable. Who would have thought that a donut in the heart of the Earth could tell us so much about our place in the universe?
