Two giant blobs lurk deep within the Earth, but why?

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Volcanoes and earthquakes are among the most dynamic and interesting forces on Earth, but their origins have remained somewhat elusive. Plate tectonics is the result of a cosmic collision about 4.5 billion years ago, when an object the size of the planet Mars collided with Earth. According to new computer modeling research, the impact left some strange blobs on our planet that may have led to plate tectonics. This new hypothesis is described in a study published May 7 in the journal Geophysical research letters.

What are these mysterious blobs?

In 1980geophysicists discovered for the first time two blobs of an unusual material the size of a continent deep near the center of the Earth. One spot has been localized under the Pacific Ocean and the other is under the African continent. Both are twice the size of our moon. They are so large that they would roughly form a layer if placed on the Earth’s surface 60 miles thick around the planet.

Formally known as large low-speed provinces (LLVPs), they are also likely made up of different proportions of elements than the mantle that surrounds them. a 2023 paper published in the journal Nature proposed that these are the remains of an ancient planet called Theia that collided with Earth in the same massive impact that created the moon. The study suggests that most of Theia was incorporated into our young planet, forming the LLVP blobs. The remaining debris formed the moon.

[Related: Earth’s first continent? Probably a giant continental crust.]

“It appears that the moon contains materials representative of both Earth and Theia before the impact, but any remnants of Theia on Earth were thought to have been ‘obliterated’ and homogenized (e.g. convection) by billions of years of dynamics inside the Earth,” astrophysicist from Arizona State University and co-author of the Nature study Steven Desch said in a statement. “This is the first study to show that discrete ‘pieces’ of Theia are still within the Earth, at the core-mantle boundary.”

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The study argues that these blobs themselves then created our planet’s plate tectonics, allowing life to flourish.

A new look at some very old minerals

This new paper builds on that research. Using computer models, they determined that about 200 million years after the Theia impact, the submerged LLVP blobs may have helped create the hot plumes within Earth that disrupted the surface. They broke the flat crust and sank circular plates in a process called subduction.

According to the teamthis could explain why the oldest minerals on Earth are zircon crystals that appear to have undergone subduction more than 4 billion years ago and may have contributed to plate tectonics.

[Related: How old is Earth? It’s a surprisingly tough question to answer.]

“The gigantic impact is not only the reason for our moon, if so, it also determined the initial conditions of our Earth,” geoscientists from the California Institute of Technology and study co-author Qian Yuan told The Washington Post.

The model has been raised Numerous questions for some outside geologists, including whether or not the collision would have resulted in a recycling of the entire Earth’s crust rather than plate tectonics. This process may have occurred billions of years ago on our sister planet Venus. There are also some geochemical inconsistencies that some scientists say cast doubt on the planet-crushing theory as a whole.

Is plate tectonics really necessary for life?

Although they can be destructive to both property and lives, some scientists believe that plate tectonics helps sustain the Earth carbon cycle. This process moves carbon between microbes, plants, minerals, animals, and Earth’s atmosphere. Carbon, the fourth most abundant element in the universe, can also form Earth’s complex molecules, such as DNA and proteins. These building blocks of carbon make life on Earth possible.

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However, another study published last year in Nature states that mobile plate tectonics did not occur on Earth about 3.9 billion years ago, when the first traces of life appeared on Earth.

[Related: Your ancestors might have been Martians.]

“We found that plate tectonics did not exist when life was first thought to have emerged, and that plate tectonics did not exist for hundreds of millions of years afterward,” says paleogeologist John Tarduno of the University of Rochester. said in a statement. “Our data suggest that when we look for exoplanets that harbor life, the planets may not necessarily have plate tectonics.”

What is clear is that concrete answers will continue to exist as to how, when and why life first appeared on our planet and what role the shifting plates did or did not play.

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