Thanks to seismic imaging, researchers have revealed that an ancient ocean floor may have surrounded the Earth’s core.
This layer is located about 2,900 kilometers below the surface at the core-mantle boundary (CMB), the region within the Earth where the molten outer core meets the silicate rock mantle. Although it is a relatively thin layer, it also has incredibly dense regions that scientists call ultra-low velocity zones (ULVZ) for their ability to slow seismic waves.
How ULVZs arise has been a subject of scientific debate for many years, particularly due to the difficulty of creating large-scale, high-quality images of the region. However, the current study seems to be able to settle this debate. “Seismic surveys like ours provide the highest resolution imaging of our planet’s interior, and we are finding that this structure is much more complex than previously thought,” Samantha Hansen, lead author of the study, said in a statement.
The research team buried a network of seismic probes in Antarctica that use seismic waves created by earthquakes to create an image of the interior of Earth’s southern hemisphere, similar to medical scans of the human body. “Our high-resolution imaging method, which analyzed 1000s of seismic records from Antarctica, found thin zones of anomalous material [UVLZs] in the CMB everywhere we surveyed,” said author Edward Garnero. “The thickness of the material ranges from a few kilometers to 10 kilometers.” It changes as much. This shows that in some places in the center we see mountains 5 times higher than Mount Everest.”
Because of the seismic wave-slowing properties and variable heights of ULVZs, researchers believe the layer is likely composed of ancient ocean crust that remained buried for millions of years as a result of the subduction of tectonic plates. They also suggest that it may cover the entirety of the Earth’s core, given that the continents move slowly over time, but further seismic research is needed to determine whether this is truly the case.
While we don’t know what future studies will show, the current findings give us a better idea of how heat can escape from Earth’s core through thinner regions, through the mantle, and onto the Earth’s surface in the form of volcanic eruptions.
“Our research provides important connections between Earth’s shallow and deep structure and the general processes that drive our planet,” says Hansen.
The study was published in Science Advances.
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