Mountains 5 times the height of Mt Everest exist near Earth’s core
Turns out, Earth’s interior is much more complicated than we once thought.
A layer between Earth’s mantle and core—approximately 2,000 miles underground— likely dense and thin, submerged under the ocean floor has been identified using large-scale seismic imaging, according to a new study published in Science Advances, on April 5.
Some regions of this layer have heights ranging from less than about 3 miles to more than 25 miles, underscoring how Earth’s interior is much more complicated than we once thought.
Earth’s underground mountains
The latest data suggests this layer could be the ultra-low velocity zone (ULVZ) which is well known to be ancient ocean floor that resulted from underground subduction long ago. Essentially, oceanic material is carried into the planet’s interior, where two tectonic plates meet, one diving beneath the other. While the ULVZ is not a new concept to science, it has only been seen previously in isolated patches— until now.
For the first time, the team was able to investigate a significant area of the southern hemisphere in high resolution using an in-depth technique that looks at sound wave echoes from the core-mantle barrier.
During four trips to Antarctica, lead author Professor Samantha Hansen from the University of Alabama, along with her students and others, deployed a seismic network that collected data for three years.
The 15 stations in the network buried in Antarctica used seismic waves produced by earthquakes worldwide to create an image of the Earth below, much like a body scan in a medical setting.
The international team discovered unexpected energy in the seismic data that arrived within several seconds of the boundary-reflected wave.
“Analyzing 1000’s of seismic recordings from Antarctica, our high-definition imaging method found thin anomalous zones of material at the CMB everywhere we probed,” Co-author Dr. Edward Garnero said in a press release.
“The material’s thickness varies from a few kilometers to 10’s of kilometers. This suggests we are seeing mountains on the core, in some places up to 5 times taller than Mt. Everest.”
It may be that these underground “mountains” play a significant role in releasing heat from the planet’s magnetic core. The researchers also highlighted that mantle plumes, or hot spots, can carry material from ancient ocean floors back to the surface through volcanic eruptions.
The full study was published in Science Advances on April 5 and can be found here.
Study abstract:
Ultralow velocity zones (ULVZs) are the most anomalous structures within the Earth’s interior; however, given the wide range of associated characteristics (thickness and composition) reported by previous studies, the origins of ULVZs have been debated for decades. Using a recently developed seismic analysis approach, we find widespread, variable ULVZs along the core-mantle boundary (CMB) beneath a largely unsampled portion of the Southern Hemisphere. Our study region is not beneath current or recent subduction zones, but our mantle convection simulations demonstrate how heterogeneous accumulations of previously subducted materials could form on the CMB and explain our seismic observations. We further show that subducted materials can be globally distributed throughout the lowermost mantle with variable concentrations. These subducted materials, advected along the CMB, can provide an explanation for the distribution and range of reported ULVZ properties.
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