Evidence of a sudden transition on the planet's surface was found in South Africa.
The crystals show that around that time, the Earth broke up and began moving, a process known as plate tectonics.
The findings offer clues about the evolution of Earth as a planet, and could help answer questions about the evolution of life on the planet.
Drabon told Live Science that Earth is the only planet with plate tectonics.
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Pieces of rigid crust are floating on a hot ocean of magma in the mantle. These pieces of crust push each other up, creating mountains and ocean ridges, and triggering earthquakes that rock the planet. New rocks at subduction zones interact with the atmosphere to suck up carbon dioxide. Drabon said that this process makes the atmosphere more hospitable for life and keeps the climate stable.
Things were not always this way. During the Hadean eon, when the planet was young and hot, it was first covered with a magma ocean and then a solid rock surface.
The exact time when the surface cracked and began moving has been debated. Some studies suggest plate tectonics began 800 million years ago, while others think it's at least 2 billion years old.
There are almost no ancient rocks at the surface to help settle the debate because the planet is recycling its crust into the mantle. Prior to this study, only 5% of the rocks at the surface were between 2.5 billion and 4 billion years old.
In the Barberton Greenstone mountain range in South Africa, Drabon and her colleagues discovered zircon crystals. The team found 33 zircons, ranging in age from 4.1 billion to 3.3 billion years old.
In the new study, published April 21 in the journal AGU Advances, the team analyzed different elements with different numbers of neutrons in ancient zircons, as well as in many other places on Earth.
The scientists found evidence of a sudden transition to primitive plate tectonics in the isotopes. A simple form of subduction had begun in at least one place on the planet. Drabon said that it was likely that the "really efficient engine of plates moving against each other" that existed today hadn't yet emerged.
Rocks from the surface held water as early as 3.8 billion years ago, suggesting that the zircons were once locked in the ocean. The earliest samples from 4.1 billion years ago show that the planet had a solid crust.
The Hadean would be the time when the Earth's magma sea persisted. People used to think that Earth was covered by a magma ocean until 3.6 billion years ago.
She said that the new study suggests that the molten lava ocean existed before the solid crust formed.
What triggered this transition? She said that one theory was that plate tectonics emerged once Earth had cooled. It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556
Drabon said that there is a question if the transition to early plate tectonics helped life evolve.
The chemical signatures of biological processes are older than the fossil evidence of life on Earth. Drabon said that some can be found as far back as 3.8 billion years ago.
It was originally published on Live Science.
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