Scientists Uncover Doughnut-Shaped Structure in Earth's Outer Core, Shedding Light on Magnetic Field

In a groundbreaking discovery, scientists have identified a ring-like structure within the Earth’s outer core, approximately 2,890 kilometers beneath our feet. This revelation, detailed in a study published in *Science Advances*, sheds new light on the composition and behavior of our planet’s core.

The study reveals the presence of a large, doughnut-shaped region within the outer core, parallel to the equator, where seismic waves—created by earthquakes—travel about 2 percent slower than in the rest of the core. This finding was made possible through the analysis of seismic waves that travel through the Earth, offering a glimpse into the core’s intricate structure.

Professor Hrvoje Tkalcic, a geophysicist from the Australian National University and co-author of the study, explained the methodology: “It was not possible for scientists to reach the planet’s core using existing technology. So, the team relied on seismic waves, and they analysed the forms of seismic waves generated by large earthquakes as they travelled through the Earth.” He elaborated on the process, stating, “We compared the data generated by seismic detectors nearer to the poles with results from closer to the Equator. We found that the waves slowed down as they passed near the ceiling, before the mantle.”

The research revealed that seismic waves decelerate in a zone that resembles a torus, a shape most people would recognize as a doughnut. Professor Tkalcic noted, “We realised that seismic waves slow down in the zone that mathematically is called a torus. To most people, this looked like a doughnut. Overall, the waves detected closer to the poles were travelling faster than those near the Equator.”

Understanding the outer core is crucial, as it is responsible for generating the Earth’s magnetic field—a protective shield against the sun's charged particles. The core’s molten iron and nickel currents function like a “giant dynamo,” which sustains this vital magnetic field.

The newly discovered structure’s buoyancy suggests it is composed of lighter chemical elements such as oxygen, hydrogen, silicon, sulphur, or carbon. These elements play a significant role in the vast currents of molten metal that flow through the core, influencing the magnetic field.

Overall, the Earth’s outer core has a radius of around 3,480 kilometers, making it slightly larger than Mars. Professor Tkalcic described it as “a planet within our own planet.” While the exact thickness of the doughnut-shaped structure remains unknown, it is estimated to extend a few hundred kilometers beneath the core-mantle boundary.

This discovery not only enhances our understanding of the Earth’s inner workings but also highlights the complexity of the forces that shape our planet.