Scientists have discovered a massive, donut-shaped structure buried thousands of miles beneath our feet.
Researchers from the Australian National University used seismic waves generated by earthquakes to peer into the Earth’s mysterious molten core.
By following the path of these waves across the planet, the researchers discovered a region several hundred kilometers thick where they traveled two percent slower than normal.
This doughnut-like structure runs parallel to the equator in a ring around the edge of the liquid outer core and could be responsible for powering our planet’s protective magnetic field.
Professor Hrvoje Tkalčić, lead author of the study, said: ‘The magnetic field is a fundamental ingredient that we need to sustain life on the surface of our planet.’
Scientists have discovered a previously undiscovered donut-shaped region buried in the Earth that could be responsible for generating Earth’s magnetic field (stock image)
Researchers have discovered a region hundreds of kilometers thick and thousands of kilometers deep that wraps around the equator in a torus shape (labeled a “low-velocity donut”)
The Earth consists of four major layers: the crust, the semi-molten mantle, a liquid metallic outer core, and a solid metallic inner core.
When the movement of tectonic plates in the Earth’s crust causes earthquakes, they cause vibrations that spread to all other layers of the Earth.
Using the global network of seismographic stations, researchers can see how the waves propagate and make predictions about conditions below the surface.
Normally, scientists only look at the large, powerful wave fronts that travel around the world in the first hour after an earthquake.
However, Professor Tkalčić and his co-author Dr. Xiaolong Ma were able to detect this structure by studying the faint traces left by the waves many hours after the initial quake.
This method showed that seismic waves traveling near the poles moved faster than those near the equator.
The donut was discovered by measuring seismic waves generated by earthquakes around the world (top image). By analyzing this data, the researchers discovered a difference in speed between the waves traveling along the poles (bottom left) and those traveling along the equator (bottom right).
By comparing their results with different models of the Earth’s interior, Professor Tkalčić and Dr Ma found that this could best be explained by the presence of an extensive underground ‘torus’ region, a doughnut-shaped area.
They predict that this region occurs only at low latitudes and runs parallel to the equator, near the ceiling of the outer core, where the liquid portion meets the mantle.
“We don’t know exactly how thick the doughnut is, but we have inferred that it is located several hundred kilometres below the core-mantle boundary,” said Professor Tkalčić.
Because of the crucial role this area plays, their discovery could also have major implications for the study of life on Earth and other planets.
The Earth’s outer core has a radius of about 3,480 kilometers, making it slightly larger than Mars.
The best explanation for these data was the presence of a region of low-density material (shown in red) close to the surface of the Earth’s liquid outer core
The Earth’s inner and outer cores are responsible for generating the planet’s magnetic field, without which life on Earth would not be possible.
This layer consists mainly of hot nickel and iron. Convection currents combined with the rotation of the Earth cause the liquid metal in this layer to flow in long vertical eddies from north to south, like giant waterspouts.
It is the swirling currents of these liquid metals that act as a dynamo, driving the Earth’s magnetic field.
Because this donut region has ‘floated’ to the top of the liquid outer core, it could be rich in lighter elements such as silicon, sulfur, oxygen, hydrogen, or carbon.
Professor Tkalčić says: ‘Our findings are interesting because this low velocity in the liquid core implies that in these regions we have a high concentration of light chemical elements that cause the seismic waves to slow down.
The researchers believe the doughnut-shaped region could be partly responsible for stirring the liquid metal in the outer core into the waterspout-like vortices that generate the planet’s magnetic field.
The Earth’s magnetic field (pictured) deflects charged particles carried by the solar wind, which can destroy the DNA of living things.
‘These light elements, together with temperature differences, cause the fluid in the outer core to move.’
Without that moving motion driving the dynamo in the planet’s interior, Earth’s magnetic field might never have formed.
Without the magnetic field, the Earth’s surface would be constantly exposed to charged particles from the sun, which can destroy the DNA of living things.
This donut-shaped region could therefore be a crucial piece of the puzzle that explains why life arose on Earth and what we look for in habitable planets elsewhere.
Dr. Tkalčić concludes: ‘Our results can lead to further studies of the magnetic field on both Earth and other planets.’