A donut-shaped region thousands of kilometers below our feet in Earth’s liquid core has been discovered by Australian National University (ANU) scientists, providing new clues about the dynamics of our planet’s magnetic field.
The structure in Earth’s liquid core is found only at low latitudes and is parallel to the equator. According to ANU seismologists, it has remained undetected until now.
of the core: the inner core, a solid layer, and the outer core, a liquid layer. Surrounding the Earth’s core is the mantle. The newly discovered donut-shaped region is at the top of Earth’s outer core, where the liquid core meets the mantle.
Study co-author and ANU geophysicist Professor Hrvoje Tkalčić said the detected seismic waves are slower in the newly discovered region than in the rest of the liquid outer core.
“The region is parallel to the equatorial plane, is confined to low latitudes, and has a donut shape,” he said. “We don’t know the exact thickness of the donut, but we infer that it reaches several hundred kilometers below the core-mantle boundary.”
New clues about the dynamics of our planet’s magnetic field
Instead of using traditional techniques for observing seismic waves and analyzing the signals generated by earthquakes in the first hour, the ANU scientists analyzed the similarities between the waveforms many hours after the origin of the earthquakes, which led them to make this unique discovery, writes .
“By understanding the geometry of the wave paths and how they traverse the volume of the outer core, we reconstructed their travel times through the Earth, demonstrating that the newly discovered region has low seismic velocities,” said Professor Tkalčić.
“The distinctive structure has remained hidden until now because previous studies collected data with less volumetric coverage of the outer core, observing waves that were typically limited to one hour after the origin times of large earthquakes. “We were able to get much better volumetric coverage because we studied the reverberant waves for several hours after the big earthquakes.”
Study co-author Dr. Xiaolong Ma said the discovery reveals some mysteries of the dynamics
Earth has two core layers
“There are still mysteries that have yet to be solved, which require multidisciplinary efforts from seismology, mineral physics, geomagnetism and geodynamics,” said Dr. Ma.
The outer core is made up predominantly of liquid iron and nickel, and the vigorous movement of the electrically conductive liquid creates the Earth’s magnetic field, which wraps around the Earth and helps support all life by shielding it from damaging solar winds and harmful radiation.
Scientists believe that knowing more about the composition of Earth’s outer core, including light chemical elements, is fundamental to understanding the magnetic field and predicting when it might eventually cease or weaken.
“Our findings are interesting because this low velocity inside the liquid core implies that we have a high concentration of light chemical elements in these regions, which would cause the seismic waves to slow down. These light elements, along with temperature differences, help stir the liquid in the outer core,” said Professor Tkalčić.
The research is published in
