Scientists have been able to reach the center of the Earth via seismic waves and have discovered a ring-shaped structure in the swirling pool of molten metal known as the outer core.
Research Presentation According to a paper published in the scientific journal Science Advances, it was discovered that there is a doughnut-shaped region within the outer core that runs parallel to the equator.
Study co-author Professor Hrvoje Tokarcic, a geophysicist at the Australian National University, said scientists cannot reach the core with current technology, so the team analysed the shape of seismic waves generated by large earthquakes as they pass through the core.
The researchers found that the waves slow down as they pass near the front ceiling of the mantle. “By understanding the shape of the wave path and how it traverses the volume of the outer core, we were able to reconstruct the time it takes for the waves to pass through Earth,” Tokarcic said.
“We noticed that seismic waves slow down in a region mathematically called the torus.”
To most people, it looked like a doughnut, he said.
Understanding the outer core is important, he said, because it's essential for life on the surface to survive: It controls the magnetic field and protects Earth from the constant bombardment of charged particles from the sun.
Electric currents flowing through the molten iron and nickel acted like a “giant dynamo” that generated and maintained the Earth's magnetic field.
Tkarčić said scientists still don't know why Earth has an active dynamo when many other planets don't, but “it's fair to say that we understand the surfaces of other planets in more detail than we understand the interior of Earth.”
He said the Earth's interior is equally vast, with a solid inner core surrounded by a liquid outer core and mantle.
Overall, the core was slightly larger than Mars. “You can think of it as an inner-Earth planet,” Tokarcic said.
“We don't know the exact thickness of the doughnut, but we estimate it extends hundreds of kilometers below the core-mantle boundary,” he added. The buoyancy of the structure suggests the presence of lighter chemical elements such as silicon, sulfur, oxygen, hydrogen and carbon.
“What's really fascinating about this field is that almost everything we know is inference based on data we have on the surface,” he said.
Co-author Dr Ma Xiaolong said that while the discovery of the new structure in the outer core lifted the veil on the dynamics of the Earth's magnetic field, “there are still many mysteries about the Earth's outer core that remain to be solved.”
