Uncovering the mystery of two structures emerging from the Earth's core

The scientists' models suggest that the LLSVPs may be the result of material being poured up from the core, explaining the unusual structure at the bottom of the mantle.

A study led by geodynamicist Yoshinori Miyazaki from Rutgers University (USA) has proposed a very reasonable new hypothesis to explain the two Giant Low Shear Velocity Zones (LLSVPs) that are sinking at the bottom of the Earth's mantle, the layer between the crust and the core. Photo: Yoshinori Miyazaki.

LLSVPs are regions where seismic waves pass through them at an unusually slow rate because they have a different composition than the rest of the mantle. 3D maps based on seismic waves show that the planet has two LLSVPs larger than continents, one located under Africa and the other under the Pacific Ocean . Image: Sanne.cottaar via Wikimedia Commons (CC BY-SA 3.0).

Previously, several hypotheses about LLSVP were put forward, the most famous of which was the speculation that they were two pieces of Theia - a planet believed to have crashed into Earth 4.5 billion years ago and merged to form today's Earth. Photo: Stock.

A recent study found that the two LLSVPs are very “old” and stable. This fits with the magma ocean theory. According to this theory, Earth was a molten, mushy sphere covered by a magma ocean soon after its formation. As this ocean cooled, it split, with heavier materials separating out and sinking. Image: ISTOCK / GETTY IMAGES PLUS / Utrecht University/ISTOCK / GETTY IMAGES PLUS / Utrecht University.

For the above hypothesis to be feasible, the ancient Earth would need to have nice, neat, clearly defined layers like a cake, with one layer on the core-mantle boundary containing a significant amount of ferropericlase (a common mineral in the mantle). Photo: scitechdaily.

However, seismic data showing much lower ferropericlase content, the disordered stacking configuration of the LLSVPs as well as the ULVZ (ultra-low velocity zone) do not support this hypothesis. Photo: Sebastian Noe / ETH Zurich.

Faced with this mystery, Dr. Miyazaki modeled the data. They mixed the basic components of the Earth and simulated how it would cool under two scenarios: with and without material leaking from the planet's crust. Photo: Vadim Sadovski/Shutterstock.

The team's models show that not all elements cool and crystallize at the same rate. As the core cools and contracts under pressure, lighter components like magnesium oxide and silicon dioxide crystallize more easily than iron in the mix, rising to the surface and "leaching" outward, dissolving with mantle material. Photo: earth.com.

They are today's LLSVPs, like secret continents rising from the core, with mountains rising high within the mantle. Photo: Anotherhood via Getty Images.

Readers are invited to watch the video: Behind the success of scientists . Source: VTV24.

Source: https://khoahocdoisong.vn/kham-pha-bi-an-ve-hai-cau-truc-troi-ra-tu-loi-trai-dat-post2149071640.html