New Study reveals Plate Tectonics Began 3.6 Billion Years Ago
Image: Discover Magazine
Zircons are the oldest minerals in the world and come in colors like the rich blue above. Researchers have now used these gemstones to identify when modern plate tectonics began.
Zircon minerals are the oldest-known Earth material. Some formed even before the planet’s crust became the rigid continental plates that move according to modern plate tectonics.
New research on ancient zircons suggests that Earth’s modern plate tectonics likely formed around 3.6 billion years ago. The paper, published in the journal Geochemical Perspective Letters, reveals how one of Earth’s defining geologic features likely formed — and set the stage for the emergence of life.
“We are reconstructing how the Earth changed from a molten ball of rock and metal to what we have today. None of the other planets have continents or liquid oceans or life,” said Michael Ackerson, a research geologist at the Smithsonian’s National Museum of Natural History and lead author of the study. “In a way we are trying to answer the question of why Earth is unique, and we can answer that to an extent with these zircons.”
Unearthing the world’s ancient past
When the world was only 200 million years old, a few zircons began to crystallize. As they solidified in ancient magma chambers, the minerals incorporated elements from their surrounding environments. By studying them today, scientists can uncover what Earth’s geochemical landscape looked like 4.3 billion years ago.
“But unlocking the secrets held within these minerals is no easy task,” said Ackerson.
To unlock ancient zircons’ secrets, Ackerson and his team gathered 15 grapefruit-sized rocks from an incredibly old geologic site in Western Australia, called the Jack Hills. They ground the rocks into sand, then separated the denser zircons from other minerals with a technique akin to gold panning.
The Jack Hills in Western Australia house rocks containing ancient zircon crystals from 4.4 billion years ago. Researchers are now analyzing these minerals to uncover Earth’s past.
Image: Dustin Trail, Dept. of Earth and Environmental Sciences, University of Rochester
Then, Ackerson and his colleagues examined elements inside several hundred microscopic zircon specimens to determine the minerals’ ages and chemical compositions. They used traces of uranium and lead to pinpoint each specimen’s age and then analyzed the amount of aluminum in the zircons to learn more about what the outside world looked like at the time.
“Each sample has the potential to tell us something completely new and reshape how we understand the origins of our planet,” said Ackerson.
Zircons have a rocky start
After examining the zircons, the researchers found that the aluminum concentration in some had increased roughly 3.6 billion years ago. High aluminum zircons can only be created in a few ways. One of those ways is through melting rocks deeper under Earth’s crust.
“It’s really hard to get aluminum into zircons because of their chemical bonds,” said Ackerson. “You need to have pretty extreme geologic conditions.”
Image: Michael Ackerson, Smithsonian
The team suspects that aluminum concentrations rose in zircons 3.6 billion years ago because rocks were melting deeper beneath Earth’s surface as the planet’s crust thickened and cooled. If correct, this points towards the emergence of modern plate tectonics.
“This compositional shift likely marks the onset of modern-style plate tectonics, and potentially could signal the emergence of life on Earth,” says Ackerson.
A zircon encrusted path forward
Plate tectonics connect Earth’s interior with its crust, atmosphere and oceans, allowing for habitable conditions to persist for eons, which in turn allows the world to host life. But the link between the origins of modern plate tectonics and life’s origins needs further investigation.
Ackerson and his co-authors’ work is part of the museum’s new initiative called Our Unique Planet, a public-private partnership, which aims to facilitate research on the enigmatic reasons behind Earth’s unique status as a habitable planet.
Moving forward, Ackerson wants to study the ancient Jack Hills zircons for traces of life and examine other supremely old rock formations for signs of the onset of plate tectonics on Earth around 3.6 billion years ago.
“We will need to do a lot more research to determine this geologic shift’s connections to the origins of life,” said Ackerson.
See more here: smithsonianmag.com
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Helge Aspevik
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NEW SCIENTIST: TRACES of the Earth’s magnetic field frozen in rocks are yielding surprises
about the planet’s past. A re-analysis of old measurements of these fields has
forced geologists to conclude that either the migrating continents were
clustered closer to the equator than previously thought, or that the Earth’s
magnetic field was not the simple pair of poles it is today.
You can find the article on my web page. 🙂
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Wisenox
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Cynognathus is an interesting creature. I read that it had a habitat that included Antarctica. I’m curious about how they know that.
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Photios
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Fossils have so far been recovered from South Africa, Argentina, Antarctica, and Namibia.
https://en.wikipedia.org/wiki/Cynognathus
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Wisenox
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I would be interested to see the dig sites on Antarctica.
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Mark Tapley
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This narrator declares the evolutionary dogma is: Give me enough time and anything can happen. There are many reasons the world is young, not billions of years old. This video refutes the billions of years hypothesis with several examples including the sedimentary layers of the Grand Canyon.
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Andy
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Oh okay.
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K Kaiser
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There is plenty of geological, biological, and (probably) also chemical evidence of one (or more) super-continents in earth’s history. For example, just look at https://en.wikipedia.org/wiki/Pangaea . In the geological time scale, even one hundred million years is quite small (i.e. 100/4500 million) years. At the current rate of movement/separation of the American continents westward from the Eurasian one (ca. 2.5 inch, or 5 cm per year) over 100 million years that equates to the current distance of ~5000 km.
Everything is on the move, always, has been and likely will continue forever.
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Andy
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There are two ‘super-continents’ known. One was Pangea as you rightly said, the other is known as Gondwana 🙂
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Herb Rose
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Hi Mark,
Sediment is a result of rain washing soil into a body of water. It does not occur when rain falls on water. Your “expert” acknowledges hundreds of layers of sediment rock in the Grand Canyon but then contends that this evidence supports his contention that it was done in one year by 40 days and nights of rain that covered the Earth.
This is a science site where evidence is supposed to lead to truth. Your’s and others misuse of evidence to support your beliefs is the antithesis of science. If you want to just use your interpretation of data to advocate your position and are unwilling to question your beliefs or consider country evidence you should not be on this platform.
Herb
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Mark Tapley
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Hello Herb:
The contention of the narrator is that the deposition of the supposed hundreds of millions of years of sediment was done quickly and then he gives the evidence to prove it. Neither myself nor others require your approval as to what is scientific.
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K Kaiser
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Most (or all ?) gemstone quality zirkons come from Cambodia.
They are mostly hand-cut with a type of facetting not found in other gemstones.
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Lit
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So plate tectonics started about the same time Earth got water. That´s what I thought. When you cover a very hot rock ball with water the surface will contract and form cracks from cooling. Earth is a water-quenched red hot ball of rock.
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Moffin
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Plus you’ve got the naughty old centrifugal force and the especially naughty moon, North then South, squeezing and ripping asunder.
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