Beneath our feet, thousands of miles deep, lies a donut-shaped region. This structure might well change our understanding of Earth's magnetic field.
Recently detected by a team from the Australian National University (ANU), this region is located solely at low latitudes, aligned with the equator.
Diagram illustrating the path of seismic waves and the heterogeneity of the outer core.
Credit: Science Advances (2024).
This geological "donut" is found in the upper part of Earth's liquid outer core, bordering the mantle. Until now, this structure had escaped detection.
ANU seismologists observed that seismic waves traveling through this region slow down compared to the rest of the liquid core. They estimate that the thickness of this formation reaches several hundred miles beneath the mantle-core boundary.
What enabled this discovery was an innovative method of analyzing seismic waves, long after their emission by major earthquakes. By studying the waves several hours after the quakes, they were able to reconstruct travel times through Earth's core, revealing this low seismic velocity region.
This low-velocity zone could be due to a high concentration of light chemical elements in the outer core. These elements influence the dynamics of Earth's magnetic field, a crucial phenomenon for protecting life on Earth.
The discovery opens new perspectives on the dynamics of Earth's magnetic field. Researchers hope this will stimulate interdisciplinary research to better understand this phenomenon and its implications.
Earth's magnetic field, indispensable for life
Earth's magnetic field is an invisible force surrounding the planet, acting as a protective shield against solar particles and cosmic radiation. This field is crucial for protecting the atmosphere and life on our planet.
The Earth's magnetic field operates through the geomagnetic dynamo, a process where the movement of liquid iron in the outer core generates electric currents. These currents produce a magnetic field that extends into space around the Earth, forming a region known as the magnetosphere. The magnetosphere deflects charged particles from the solar wind, preventing them from directly striking Earth's surface.
The Earth's magnetic field is essential for maintaining life on Earth. It protects our atmosphere from solar winds, which could otherwise erode it, and reduces the impact of cosmic radiation that could be harmful to living organisms. Without this magnetic field, Earth would be much more vulnerable to destructive space effects.