Scientists have discovered a previously unknown doughnut-shaped region in Earth’s outer core, providing new insights into the dynamics of the planet’s magnetic field.
The “doughnut” hidden in the core of the Earth PHOTO: Video capture
Located thousands of kilometers below the Earth’s surface, this doughnut-shaped region lies in the liquid outer core, parallel to the equator and confined to low latitudes.
More than just a quirk in our planet’s internal structure, the donut’s composition could help us better understand Earth’s magnetic field — the shield that surrounds us and protects life on the surface from damaging solar winds and radiation, according to newsweek. com.
The magnetic field is formed by the vigorous movement of liquid iron and nickel, a process determined by temperature differences and, crucially, by the presence of light elements such as those in the doughnut.
“The outer core is a bit larger than the planet Mars, but we know more about the surface of the red planet than the interior of the core,” study co-author Hrvoje Tkalčić told Newsweek. His team’s findings, published in the journal Science Advances, add a huge piece to the puzzle that has so far gone undetected.
The Earth itself is composed of two core layers: a solid inner core and a liquid outer core, which is surrounded by the mantle. The newly discovered structure is located at the top of the outer core, where it meets the mantle.
“The region is parallel to the equatorial plane, is confined to low latitudes, and has a donut shape,” Tkalčić said in a statement. “We don’t know the exact thickness of the donut, but we deduced that it reaches several hundred kilometers below the core-mantle boundary”.
The discovery was made possible by a new approach to seismic wave analysis.
“Like doctors who use ultrasound or X-rays, global seismologists can use the waveforms recorded on seismographs around the world due to the passage of seismic waves after large earthquakes, explosions, impacts and other natural phenomena”said Tkalčić.
“We can use their arrival times, amplitudes or waveforms. The key is understanding how these waves travel through the Earth, propagating, penetrating or ricocheting at internal boundaries and inhomogeneities.”
Instead of relying on traditional methods that focus on signals in the first hour following a seismic event, the scientists analyzed waveforms several hours after the earthquakes. This method allowed them to better measure the internal properties of the core, because the waves have time to bounce off the boundary structures, like echoes in a cave.
“Of course, these signals are tiny because their energy weakens during multiple passes through the core, but we don’t look directly at the weak signals. We detect them by measuring their similarity on many recorders around the world. The similarity of two weak signals becomes more important information than the signals themselves,” explained Tkalčić.
The speed at which seismic waves travel through this donut is slower than in other regions, the team found, implying a higher concentration of light chemical elements than elsewhere.
Tkalčić added: “Light chemical elements are an essential ingredient that drives vigorous convection in the outer core due to their buoyancy, and in turn this process, associated with Earth’s rotation, sustains a geodynamo in the liquid core – the source of Earth’s magnetic field. Understanding the spatial distribution of the elements bright is an essential initial condition for numerical simulations of the geodynamo and for understanding the change in its intensity and direction over time.”
