New research suggests that a group of mysterious, ultra-dense structures just outside the Earth’s core may be the remnants of ancient interplanetary collisions.
These strange structures are known as ultra-slow zones (ULVZ) because they are generated by seismic waves. earthquake Move these zones about 50% slower than the surrounding mantle. This means that ULVZ is much denser than other mantles and is probably made of heavier elements.
ULVZ is about 1,800 miles (2,900 km) below, so it’s hard to say for sure about these dense rock masses. EarthSurface — One group gathers deep in Africa and the other just below the Pacific Ocean, where the rock mantle meets the outer core of liquid metal. It’s too deep for the human eye to see. Only seismic data can provide clues about the size, shape, and structure of ULVZ.
Now, using new computer models and fresh seismic observations from deep Australia and New Zealand, researchers may have added important pieces to the ULVZ puzzle.According to a study published in the journal on December 30, 2021 Nature GeoscienceIt seems that these zones are not a uniform structure, but are made up of layers of different materials that have accumulated over the years.
“The most surprising finding is that the ultraslow zones are not uniform, but they contain strong structural and structural variations,” said a postdoctoral fellow at the Australian National University. Surya Pahai said. Said in a statement.. “This type of ULVZ can be explained by chemicals [variations] Created in the first stages of Earth’s history, it is not yet fully mixed after 4.5 billion years of mantle convection. “
(Mantle convection is the process by which hard rocks in the planet’s mantle slowly move along with heat currents.)
After their computer simulations showed that layered or mixed structures were likely within the ULVZ, researchers suggested a possible story of the origin of the structure.Below the surface are heavy elements such as: iron, Sinking towards the core of the planet, Silicon, Ascended towards the mantle.
All of this organization was in turmoil when a Martian-sized planet known as Theia collided directly with the early Earth. This is an ancient cataclysm that researchers call the Giant Impact Hypothesis. The collision may have scattered large amounts of debris into the Earth’s orbit. Month — Pachai said, raising the temperature of the entire planet and creating a large “sea” of magma on the surface of the planet.
Researchers have stated that various rocks, gases, and crystals forged during the collision were scattered in the magma ocean, but not forever. Over the next billion years, heavy material sinks towards the bottom of the mantle, followed by light material, eventually forming a dense layered structure of iron and other elements at the core-mantle boundary. Was there. As the mantle was agitated over the years, this dense layer separated into smaller chunks that spread throughout the Lower Mantle, effectively giving the ULVZ we know today.
Researchers added that this scenario may not be able to explain the sources of all ULVZs. There is also some evidence that other phenomena, such as the melting of the oceanic crust in the mantle, can explain ULVZ. However, the team’s model shows that the giant-impact hypothesis does explain how to create dense, layered zones.
Originally published on Live Science.
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