Mar 26, 2021 12:09 AM
(This post was last modified: Mar 26, 2021 06:53 PM by C C.)
Scientists Pin Down When Earth’s Crust Cracked, Then Came to Life
https://www.quantamagazine.org/ancient-r...-20210325/
EXCERPTS: Now, a study of the rocks from the Australian Outback by Tusch, Münker and their co-authors, published in Proceedings of the National Academy of Sciences, has captured “a snapshot” of the advent of plate tectonics, said Alan Collins, a geologist at the University of Adelaide in Australia. The team’s analysis of tungsten isotopes in the rocks reveals Earth in the act of transitioning to plate tectonics around 3.2 billion years ago.
[...] It “supports the growing consensus in the geological community that plate tectonics established itself at a global scale” sometime around 3 billion years ago, he said. “There’s a lot of different people, coming from very different perspectives, coming up with a convergence of 3.2 to 3 billion years,” said Collins.
[...] plate tectonics has helped Earth maintain a habitable climate for billions of years despite a gradually brightening sun. Our Goldilocks climate largely results from chemical reactions between carbon dioxide in the air and silicate minerals, which slowly reduces the level of the greenhouse gas in the atmosphere by burying it in sediments. Most of that silicate-carbon dioxide reacting happens on the slopes of mountains made by colliding plates.
Moreover, recycling of material between the mantle, crust, oceans and atmosphere ensures a continuous supply of elements that are crucial to life. Plate tectonics refines the mantle, causing elements like phosphorus to accrue on the surface as continental crust. These elements fertilize life in ocean waters when mountains are weathered and washed into the sea. And the continents themselves provide sunlit real estate for new species.
Just as important, mantle convection lets heat escape from Earth’s core, helping the core generate a magnetic field. The field extends far into space and protects the atmosphere from being eroded away by solar storms... (MORE - details)
Vast fragments of an alien world could be buried deep within Earth itself
https://www.sciencealert.com/vast-myster...tudy-finds
EXCERPTS: They are among the largest and strangest of all structures on Earth: huge, mysterious blobs of dense rock lurking deep within the lowermost parts of our planet's mantle. There are two of these gigantic masses – called the large low-shear-velocity provinces (LLSVPs) – with one buried under Africa, the other below the Pacific Ocean. These anomalies are so massive, they in turn breed their own disturbances, such as the large phenomenon currently evolving within and weakening Earth's magnetic field, known as the South Atlantic Anomaly.
As for how and why the LLSVPs came to exist like this within the mantle, scientists have lots of ideas, but little in the way of hard proof. What is known, however, is that these giant blobs have been around for a very long time, with many thinking they could have been a part of Earth since before the giant impact that birthed the Moon – ancient traces of the collision between Earth and the hypothetical planet Theia.
[...] Some researchers have suggested the cores of these two primordial planets may have fused into one, and that chemical exchanges wrought by this epic merger are what enabled life itself to thrive on the world that resulted.
[...] According to new modeling by researchers from Arizona State University (ASU), the LLSVPs may represent ancient fragments of Theia's iron-rich and highly dense mantle, which sank deep into Earth's own mantle when the two developing worlds came together, and has been buried there for billions of years. While speculation has existed for years that the LLSVPs may be an alien souvenir implanted by Theia, the new research appears to be the most comprehensive formulation yet. The findings are currently under review, ahead of future publication in Geophysical Research Letters... (MORE - details)
https://www.quantamagazine.org/ancient-r...-20210325/
EXCERPTS: Now, a study of the rocks from the Australian Outback by Tusch, Münker and their co-authors, published in Proceedings of the National Academy of Sciences, has captured “a snapshot” of the advent of plate tectonics, said Alan Collins, a geologist at the University of Adelaide in Australia. The team’s analysis of tungsten isotopes in the rocks reveals Earth in the act of transitioning to plate tectonics around 3.2 billion years ago.
[...] It “supports the growing consensus in the geological community that plate tectonics established itself at a global scale” sometime around 3 billion years ago, he said. “There’s a lot of different people, coming from very different perspectives, coming up with a convergence of 3.2 to 3 billion years,” said Collins.
[...] plate tectonics has helped Earth maintain a habitable climate for billions of years despite a gradually brightening sun. Our Goldilocks climate largely results from chemical reactions between carbon dioxide in the air and silicate minerals, which slowly reduces the level of the greenhouse gas in the atmosphere by burying it in sediments. Most of that silicate-carbon dioxide reacting happens on the slopes of mountains made by colliding plates.
Moreover, recycling of material between the mantle, crust, oceans and atmosphere ensures a continuous supply of elements that are crucial to life. Plate tectonics refines the mantle, causing elements like phosphorus to accrue on the surface as continental crust. These elements fertilize life in ocean waters when mountains are weathered and washed into the sea. And the continents themselves provide sunlit real estate for new species.
Just as important, mantle convection lets heat escape from Earth’s core, helping the core generate a magnetic field. The field extends far into space and protects the atmosphere from being eroded away by solar storms... (MORE - details)
Vast fragments of an alien world could be buried deep within Earth itself
https://www.sciencealert.com/vast-myster...tudy-finds
EXCERPTS: They are among the largest and strangest of all structures on Earth: huge, mysterious blobs of dense rock lurking deep within the lowermost parts of our planet's mantle. There are two of these gigantic masses – called the large low-shear-velocity provinces (LLSVPs) – with one buried under Africa, the other below the Pacific Ocean. These anomalies are so massive, they in turn breed their own disturbances, such as the large phenomenon currently evolving within and weakening Earth's magnetic field, known as the South Atlantic Anomaly.
As for how and why the LLSVPs came to exist like this within the mantle, scientists have lots of ideas, but little in the way of hard proof. What is known, however, is that these giant blobs have been around for a very long time, with many thinking they could have been a part of Earth since before the giant impact that birthed the Moon – ancient traces of the collision between Earth and the hypothetical planet Theia.
[...] Some researchers have suggested the cores of these two primordial planets may have fused into one, and that chemical exchanges wrought by this epic merger are what enabled life itself to thrive on the world that resulted.
[...] According to new modeling by researchers from Arizona State University (ASU), the LLSVPs may represent ancient fragments of Theia's iron-rich and highly dense mantle, which sank deep into Earth's own mantle when the two developing worlds came together, and has been buried there for billions of years. While speculation has existed for years that the LLSVPs may be an alien souvenir implanted by Theia, the new research appears to be the most comprehensive formulation yet. The findings are currently under review, ahead of future publication in Geophysical Research Letters... (MORE - details)