About 3 billion years ago, The Earth‘Geologists have found that the crust swelled during massive growth.
At that time, just 1.5 billion years after the formation of the Earth, the mantle – the layer of silicate rock between the crust and the outer core that was more active in the past – heated up, causing the magma from that layer to flow into fragments of older bark above it. These fragments acted as “seeds” for the growth of modernity continents.
Researchers have found evidence of this leap in growth, which lies in ancient zircon crystals in the sediments of the stream in Greenland. These extremely durable crystals ̵
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“There have probably been many crustal-forming events in Earth’s history,” lead researcher Chris Kirkland, a professor of geology at Curtin University in Australia, told Live Science. “But this global injection event 3 billion years ago is definitely one of the biggest.”
Before this massive period of growth, the ancient crust of the Earth was much thinner and weaker than it is today. Eventually, it disintegrated into fragments of bark that served as floating “rescue rafts” from which new bark could sprout.
“We think of bark as that floating material that sits on the mantle,” Kirkland said. “That means he’s constantly getting an injection of new material coming from below. The longer he sits on top, the more new material is injected into him and the bigger he gets.”
The mantle temperatures peaked at this time due to the radioactive decay of elements such as uranium and potassium in the core of the Earth, as well as from the residual heat that left the formation of the planet. As this peak of temperatures around the world stimulates the process, the crust continues to bubble on a large scale for a period of about 200 million years, according to researchers.
At the end of this period, the first continents began to take shape, eventually allowing the development of complex life on land about 400 million years ago.
Evidence of this growth spurt turned out to be embedded zircon crystals, smaller than 100 microns (less than the width of a human hair), which were eroded by rocks and accumulated in the sedimentary sediments of West Greenland.
“Zircon is like a geologist’s favorite set of tools because it can tell us so much,” Kirkland said. “The crystal is very strong, it captures information about its origin.”
Like trees, crystals have growth rings caused by periods of magma injection. To age exactly these rings, Kirkland and his colleagues blew up the crystals with ion beams – a beam of charged particles capable of accurately breaking ultra-strong miniature crystals to separate the segments of the ring for individual analysis.
By isotope dating – versions of elements with different numbers of neutrons in each atom – in each “ring” they found that the crystals were composed of ancient (4 million years old) and newer (3 million years old) crust. This supports their hypothesis that older fragments of bark acted as seeds to form newer bark.
“It’s amazing that from these individual grains you can gather the ancient history of our planet,” Kirkland said. “It’s like being able to understand someone’s parents’ age just by looking at them.”
Other studies conducted by various researchers in Australia, South Africa and Scotland – all places where you can find ancient rocks – have found similar results, proving that this was also part of a massive global injection.
Understanding the earth’s crust
In addition to the “wow” factor to discover how the Earth’s outer shell has formed so long ago, the results can also be used to find new sources of depleted metals.
“Western Australia is a good example,” Kirkland said. “We have a lot gold,, iron and nickel reserves, but most of them are found in shallow crusts. When we start using these resources, we have to look for new ones in the deeper crust. “
However, he acknowledged that these new resources would be more difficult to access and extracting them would be a huge logistical challenge. Instead, he believes the true value of his team’s discovery is academic.
“It’s all about understanding how these small pieces of bark that we live on evolved,” Kirkland said. “Success is picking up things that happened billions of years ago from these little grains.”
The study was published Jan. 12 in the journal Nature Communications.
Originally published in Live Science.