Scientists from The Australian National University (ANU) have made a discovery deep beneath Earth’s surface revealing a Doughnut-Shaped Structure region within the planet’s liquid outer core. The findings were published in the journal Science Advances.
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Earth’s core has been explored using seismic waves generated by large earthquakes. These seismic waves, which travel through the Earth provide valuable information about the planet’s interior.
Researchers focused on the analysis of these waves, particularly how they behaved as they traversed the outer core. It was observed that the waves slowed down as they passed through a specific region of the outer core.
The slow-moving seismic waves revealed a doughnut-shaped or torus-like structure within the outer core, oriented parallel to the equator.
This Doughnut-Shaped Structure is situated near the boundary between the outer core and the mantle, at lower latitudes. The exact thickness of this doughnut is still unknown, but it is estimated to extend a few hundred kilometers beneath the core-mantle boundary.
The Earth’s outer core plays an important role in the generation and maintenance of the planet’s magnetic field. The outer core is composed of molten iron and nickel, and the movement of these electrically conductive fluids creates a giant dynamo effect generating Earth’s magnetic field.
This magnetic field is vital for life on Earth as it shields the planet from harmful solar radiation and charged particles from the sun.
The Doughnut-Shaped Structure region within the outer core is believed to contain a higher concentration of lighter elements such as silicon, sulfur, oxygen, hydrogen or carbon. These lighter elements combined with temperature variations, contribute to the slowing down of seismic waves in this region.
The presence of these light elements also suggests a buoyancy within this region, which may influence the movement of the molten metal and the dynamics of the Earth’s magnetic field.
The ANU research team employed a unique methodology, analyzing seismic waveforms many hours after the earthquake instead of focusing solely on the wave signals. This approach allowed the researchers to capture more data and revealed the doughnut-shaped structure that had remained hidden in previous studies.
The methodology involved reconstructing the travel times of the seismic waves through the Earth’s outer core, which led to the identification of the slow-moving region.
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The discovered region within the Earth’s outer core has a Doughnut-Shaped Structure and is found only at low latitudes. It is located at the top of the Earth’s outer core, where the liquid core meets the mantle.
Unlike traditional seismic wave observation techniques, which focus on signals generated within the first hour of an earthquake, the ANU scientists analyzed waveforms many hours after the earthquake origin times. This approach allowed them to detect the unique structure that had remained hidden until now.
Seismic waves detected in the newly discovered region travel slower compared to the rest of the liquid outer core. This finding says that the region has distinct physical properties such as a higher concentration of light chemical elements.
The presence of light chemical elements in the region suggests variations in the composition of the outer core. These elements with temperature differences, contribute to the stirring of liquid in the outer core.
The discovery of this Doughnut-Shaped Structure region provides new insights into the dynamics of Earth’s magnetic field. Understanding the composition and behavior of this region is crucial for predicting changes in the magnetic field including potential weakening or cessation.
The study addresses the need for multidisciplinary efforts combining seismology, mineral physics, geomagnetism and geodynamics, to fully understand the complexities of the Earth’s outer core and its role in generating the magnetic field.
The core-mantle boundary is a region where the solid mantle meets the liquid outer core. It is a zone of intense interest for scientists due to its role in regulating the Earth’s magnetic field and geological activity.
Researchers have identified Ultra-Low Velocity Zones (ULVZs) at the core-mantle boundary. These zones are believed to be remnants of ancient ocean floors that have sunk deep into the Earth’s interior.
The ULVZs are composed of compacted and densified ancient oceanic crust. These layers have remained preserved for millions of years. By analyzing seismic waves that slow down upon encountering these dense ULVZs, scientists have been able to map the structures at the core-mantle boundary.
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