Earth has a curious mystery deep within its core. Scientists have found two dense blobs, known as large low-shear-velocity provinces (LLSVPs), sitting above the core. New research suggests these structures may have formed from melted material that leaked out of the core when our planet was young.
Yoshinori Miyazaki, a geodynamicist at Rutgers University, calls these blobs “fingerprints of Earth’s earliest history.” Studying them could give us insights into how Earth formed and became a livable planet.
The LLSVPs were first noticed in the 1980s through seismic data from earthquakes. One is located beneath Africa, and the other is under the Pacific Ocean. They stretch from the core-mantle boundary, which is about 2,900 kilometers (around 1,800 miles) below the surface. Seismic waves pass through these regions more slowly, suggesting they are made of different materials than the surrounding mantle.
Researchers have proposed various theories about their origin. Some think they are remnants of old tectonic slabs, while others suggest they could be parts of a giant object named Theia that impacted Earth and formed the Moon. Recently, some experts have pointed to the impact these blobs may have on Earth’s magnetic field, especially the one beneath the Atlantic Ocean.
Understanding these blobs could reveal how tectonic plates formed. Recent studies indicate they are quite old and stable, aligning with the magma ocean theory. This suggests that Earth once had a molten outer layer. As it cooled, heavier materials sank, creating distinct layers.
However, some data challenges this theory. For instance, seismic data indicates that the content of ferropericlase, a mineral thought to be abundant near the core-mantle boundary, is actually quite low. This discrepancy led Miyazaki and his team to explore whether material leaking from the core could account for what we observe today.
They modeled how different materials cool and crystallize. They discovered that lighter components like magnesium oxide and silicon dioxide could escape from the core and mix with the magma. This shift could lead to the formation of silicate-rich minerals that dominate the lower mantle.
Even in extreme conditions deep inside the Earth, these structures have existed for about 4.5 billion years. They have gradually come together through convection, forming the distinct shapes we see in seismic data now.
This work raises intriguing questions about how different planets evolve. If these blobs contributed to forming tectonic plates, understanding them may help us learn more about other worlds in our solar system and beyond.
In a world where many mysteries remain, Miyazaki notes, “We’re starting to build a story that makes sense.” This ongoing research could reshape our understanding of Earth’s history and why it is a unique place to live. The findings were published in Nature Geoscience.
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