A recent study in the field of geology has revealed the finding of a surprising structure around the Earth’s core. Scientists believe that this structure could be the remnant of an ancient ocean floor. This research has the potential to change our understanding of our planet’s interior and how its magnetic field works.
an unexpected discovery
The search for answers in the Earth’s core
For centuries, scientists have tried to better understand the center of our planet. The Earth’s core is believed to be a huge sphere of iron, but a recent study published in Science Advances suggests that there is an ancient structure surrounding it.
To carry out this research, the scientists used 15 monitoring stations located on the ice of Antarctica. These stations detect seismic waves traveling through the ground, allowing researchers to study how these waves move through the Earth’s core. In this way, it was possible to detect the presence of structures and material compositions under the planet’s surface.
(A) Maps showing the locations along the CMB of previous investigations of seismic wave scattering and ULVZ (Ultra low velocity zone – Ultra low velocity zones are patches at the core-mantle boundary that have seismic velocities extremely low) both in global view (left) and in the southern hemisphere (right). Areas marked in gold indicate regions where ULVZ evidence was found; those outlined in blue indicate regions where ULVZ was not observed, and those outlined in red mark uncertain regions. Pink shading indicates LLVPs (characteristic structures of parts of the Earth’s lower mantle that are characterized by slow shear wave velocities) and green dots mark seismic scatters. (B) Cartoon highlighting both the LLVP upwelling and subduction in the lower mantle along with various CMB anomalies. UHVZ, ultra high speed zones.
Let’s get a little technical
The absolute change in physical properties (for example, temperature, density, and viscosity) from the mantle to the core is greater than the change between solid rock and air. This means that at the border between the Earth’s mantle and the core there is a great variety of phenomena. One such phenomenon is Ultra Low Velocity Zones (ULVZs), which are areas with greatly reduced seismic wave velocities and increased density.
Previous research has found different features in ULVZs, leading to debate about their origins. Some experts think that ULVZs are due to the presence of molten material partly due to temperature anomalies at the mantle-core boundary. However, some ULVZs are located far from the hottest areas of the mantle, suggesting that they could also be related to differences in material composition.
Although only 20% of the mantle-core boundary has been studied, other studies have identified small variations in the deepest part of the mantle. These variations and ULVZs are found in greatest numbers near Low Velocity Provinces (LLVPs) located beneath Africa and the Pacific Ocean, but are also found in other areas of the deep mantle. This suggests that the ULVZ and other mantle anomalies could be part of the Earth’s mantle convection cycle.
Geodynamic modeling studies have shown that mid-ocean ridge rocks and oceanic sediments could be transported into the deep mantle by subducting downdrafts and drift toward areas of mantle rise such as LLVPs. Subducted materials may take more than 100 million years to reach the deep mantle, during which time the convergent boundary at the surface may have shifted elsewhere. Therefore, parts of the mantle-core boundary that are not currently subducting could have been influenced by mantle downdrafts.
In this study, the researchers examined a part of the mantle deep beneath the southern hemisphere that is not within or near the LLVPs or beneath current or recent subduction areas. They used seismic waves and geodynamic simulations to assess the presence and variability of the ULVZ structure and how it relates to possible mineralogical scenarios. Their results, combined with previous research, and their 3D geodynamic models provide strong evidence for a globally distributed but heterogeneous ULVZ structure throughout the Earth’s deep mantle. The widespread distribution of the ULVZs and the range of reported features can be explained by materials subducted along the mantle-core boundary.
Evidence of an ancient oceanic structure
Mountains and valleys in the depths of the Earth
Data collected by the monitoring stations revealed that the ancient structure around the Earth’s core features mountains and valleys, indicating variations in the thickness of the material. This led scientists to hypothesize that it could be remnants of an ancient ocean floor.
The challenges of data interpretation
Despite the evidence found, the researchers admit that it is difficult to make definitive assumptions about the rocks and materials detected through seismic wave monitoring. Therefore, they do not rule out other possibilities.
The implications of the discovery
The magnetic field and the protection of the Earth
The study of this type of structure is essential to expand our knowledge about the functioning of the Earth’s magnetic field, which has the important function of protecting our planet from solar radiation emitted by the Sun.
This discovery provides us with a unique opportunity to reflect on the nature and history of our planet. If it is confirmed that the structure surrounding the Earth’s core is indeed an ancient ocean floor, this could have significant implications for our understanding of Earth’s geological evolution.
