A group of structures just outside Earth's core may be the remnants of an ancient collision.
These structures are known as ultralow-velocity zones because they are slower to travel through than the surrounding mantle. The rest of the mantle may be made of heavier elements, as the ULVZs are denser.
It's difficult to say anything for certain about these dense blobs of rock, because they are deep below the surface of Earth and below the Pacific Ocean. It's too deep for human eyes to see, and only seismic data can give clues about the size, shape and structure of the ULVZs.
What makes Earth unique?
A new computer model and fresh seismic observations from Australia and New Zealand may have added an important piece to the puzzle. According to a study published in the journal Nature Geoscience, the zones are made of layers of different materials that accumulated over the eons.
Surya Pachhai, a researcher at the Australian National University, said in a statement that the ultra-low velocity zones are not homogeneity but contain strong structural and composition variations. The chemicalvariations created at the very beginning of the Earth's history can be explained by this type of ULVZ.
The process by which the solid rocks in the planet's mantle slowly move in accordance with heat currents is called mantle convection.
The origin story for the structures could be as old as 4 billion years ago, after the computer simulations showed that a mixed structure was likely. The heavier elements were sinking toward the planet's core while lighter elements rose toward the mantle.
The giant impact hypothesis is a theory about how a Mars-size planet slammed into the early Earth. The collision may have caused a lot of debris to fall into Earth's orbit, leading to the formation of the moon, and raising the planet's temperature, Pachhai said.
The researchers said that the rocks, gases and crystals that were forged during the collision would have dispersed through the ocean. After billions of years, heavier materials would sink toward the bottom of the mantle, followed by lighter ones, creating a dense structure of iron and other elements at the core-mantle boundary. As the mantle churned over the ages, the dense layer would have separated into smaller clumps, which would have given us the U.S.U.Vs we know today.
The researchers said that this scenario may not explain the source of all ULVZs, as there is evidence that other phenomena could explain them. The team's models show that the giant impact hypothesis explains how dense the zones could have been.
Live Science published the original article.
A group of structures just outside Earth's core may be the remnants of an ancient collision.
These structures are known as ultralow-velocity zones because they are slower to travel through than the surrounding mantle. The rest of the mantle may be made of heavier elements, as the ULVZs are denser.
It's difficult to say anything for certain about these dense blobs of rock, because they are deep below the surface of Earth and below the Pacific Ocean. It's too deep for human eyes to see, and only seismic data can give clues about the size, shape and structure of the ULVZs.
A new computer model and fresh seismic observations from Australia and New Zealand may have added an important piece to the puzzle. According to a study published in the journal Nature Geoscience, the zones are made of layers of different materials that accumulated over the eons.
Surya Pachhai, a researcher at the Australian National University, said in a statement that the ultra-low velocity zones are not homogeneity but contain strong structural and composition variations. The chemicalvariations created at the very beginning of the Earth's history can be explained by this type of ULVZ.
The process by which the solid rocks in the planet's mantle slowly move in accordance with heat currents is called mantle convection.
The origin story for the structures could be as old as 4 billion years ago, after the computer simulations showed that a mixed structure was likely. The heavier elements were sinking toward the planet's core while lighter elements rose toward the mantle.
The giant impact hypothesis is a theory about how a Mars-size planet slammed into the early Earth. The collision may have caused a lot of debris to fall into Earth's orbit, leading to the formation of the moon, and raising the planet's temperature, Pachhai said.
The researchers said that the rocks, gases and crystals that were forged during the collision would have dispersed through the ocean. After billions of years, heavier materials would sink toward the bottom of the mantle, followed by lighter ones, creating a dense structure of iron and other elements at the core-mantle boundary. As the mantle churned over the ages, the dense layer would have separated into smaller clumps, which would have given us the U.S.U.Vs we know today.
The researchers said that this scenario may not explain the source of all ULVZs, as there is evidence that other phenomena could explain them. The team's models show that the giant impact hypothesis explains how dense the zones could have been.
Live Science published the original article.
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