Young continents were fragile and prone to destruction

Dec. 2 (UPI) — Earth’s earliest continents were fragile and destruction-prone, according to a new study published Wednesday in the journal Nature.

Earth formed roughly 4.5 billion years ago, but the planet’s infancy — its first 1.5 billion years — and the processes that shaped its continental features are poorly understood.

“This was the time of formation of the first continents, the emergence of land, the development of the early atmosphere and the appearance of primordial life — all of which are the result of the dynamics of our planet’s interiors,” lead study author Fabio Capitanio said in a news release.

For the new study, Capitanio and his colleagues created computer models simulate the conditions of early Earth.

“We show that the release of internal primordial heat, three to four times that of the present-day, caused large melting in the shallow mantle, which was then extruded as magma … onto the Earth’s surface,” said Capitanio, a researcher at Monash in Australia.

According to the models, the pieces of mantle left behind by this process formed the keels of the planet’s first continents. The landforms, however, were dehydrated and rigid.

Simulations suggest the first continents remained weak for billions of years, and were prone to destruction. Early on, Earth’s landforms were easy to melt, making them more malleable, allowing them to became increasingly differentiated.

Over time, this process produced larger and more rigid pieces of mantle, forming what would become the cores of modern continents.

Today, these cores take the form of cratons, the large, stable chunks of mantle and crust found in the interior of Earth’s continents.

The process of early continent formation was essential to the evolution of Earth’s geochemistry and, ultimately, the planet’s biochemistry.

“The emergence of these rigid early continents resulted in their weathering and erosion, changing the composition of the atmosphere and providing nutrients to the ocean seeding the development of life,” Capitanio said.

The new research also explains why so little of Earth’s primordial crust remains. The destruction and incorporation of Earth’s earliest continental crust into the mantle helped reinforce the keel-like chunks of mantle that came to form cratons.

According to Capitanio and his colleagues, these cratons house the earliest evidence of life on Earth, but they make up only a tiny fraction of Earth’s surface.

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