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Earth’s tectonic plates began to move more than 3.2 billion years ago, just over 1.3 billion years after Earth first formed and earlier than originally thought.
Earth’s outermost layer is divided into seven major tectonic plates and many smaller ones that move between 0.4 inches and 6.2 inches per year.
A team of geologists at Harvard University set out to find out how early in Earth’s history tectonic activity, that is, plate movement, began to occur.
The rocks in Western Australia, one of the oldest pieces of the Earth’s crust, show evidence of drift of about an inch per year, starting 3.2 billion years ago.
There are a number of theories about exactly when tectonic activity began on Earth, from a billion years ago to 3 billion years ago, this new research puts the start of the movement some 200 million years earlier than the oldest estimates.
An artistic cross section through the formation of the crust approximately 3-4 billion years ago. The presence or absence of plate tectonics during this time is a subject of vigorous scientific debate.
The research team, led by Alec Brenner of Harvard, searched for clues of tectonic activity in ancient rocks in Australian rocks over 3 billion years old.
The researchers believe this change is the first evidence that modern plate movement occurred earlier in Earth’s evolution than previously thought.
They also believe that it shows that ancient Earth was very similar in structure to the world we know today.
Adding to the growing research, tectonic motion occurred on early Earth and was much more similar to modern motion than previously thought.
The researchers studied rocks from the Pilbara Craton, an ancient and stable part of the continental lithosphere located in Pilbara, Western Australia.
The lithosphere is the rigid outer layer of Earth that the plates are part of and is a mixture of oceanic and continental shells, each topped by its own type of crust.
Roger Fu, author of the study, poses on an outcrop of Honeyeater basalt at Pilbara Craton in Western Australia. The ancient rocks exposed here showed the study authors that the Pilbara Craton moved on Earth’s surface about 3.2 billion years ago.
“Basically, this is a piece of geological evidence to extend the record of plate tectonics on Earth further back in Earth’s history,” said Brenner, co-author of the article.
“ Based on the evidence we found, it seems that plate tectonics is a much more likely process that has occurred on early Earth and that it defends an Earth that looks much more like today’s than many people think. ”
Plate tectonics is key to the evolution of life and the development of the planet.
Today, Earth’s outer layer consists of about 15 rigid blocks of crust that house the planet’s continents and oceans, the researchers say.
The movement of these plates shaped the location of the continents and helped form new ones, as well as unique landforms such as mountain ranges.
It also exposed new rocks to the atmosphere, causing chemical reactions that stabilized Earth’s surface temperature for billions of years.
A stable climate is crucial to the evolution of life, the team wrote.
When the first changes occurred, it has long been a subject of considerable debate in geology, so any information that sheds light on it is valuable.
The study, published on Earth Day, helps fill some of the gaps and generally suggests the earliest forms of life developed in a more moderate environment.
“We are trying to understand the geophysical principles that drive Earth,” said Roger Fu, one of the article’s co-authors.
He said that plate tectonics is responsible for the cycle of the elements necessary for life on Earth and to leave it again.
It is a process that is also helping to understand other planets in the solar system and on exoplanets beyond our own star.
“Currently, Earth is the only known planetary body that has solidly established plate tectonics of any kind,” said Brenner of the Graduate School of Arts and Sciences.
“It really is up to us as we search for planets in other solar systems to understand the full set of processes that led to plate tectonics on Earth and what driving forces emerged to initiate it,” he said.
“Hopefully, that would give us an idea of how easy it is for plate tectonics to happen on other worlds, especially considering all the links between plate tectonics, life evolution, and climate stabilization.”
A geological map of the Pilbara Craton in Western Australia. The rocks exposed here range from 2.5 to 3.5 billion years ago, offering a unique and well-preserved window into Earth’s deep past.
Project team members traveled to the Pilbara Craton in Western Australia.
A craton is a thick, very stable primordial bark. They are usually found in the middle of tectonic plates and are the ancient hearts of Earth’s continents.
These characteristics make them the natural place to study Earth.
The Pilbara Craton stretches about 300 miles wide, covering approximately the same area as the state of Pennsylvania.
In 2017, Fu and Brenner took samples from a portion called the Honeyeater Basalt drilling holes in the rocks and collected core samples about an inch wide.
Fu and Brenner’s work differs from most studies because scientists focused on measuring the position of rocks over time, while other works tend to focus on chemical structures in rocks that suggest tectonic motion.
The researchers used the novel Quantum Diamond Microscope to confirm their findings from 3.2 billion years ago.
The microscope takes pictures of the magnetic fields and particles in a sample. It was developed in collaboration between researchers at Harvard and MIT.
In the document, the researchers note that they were unable to rule out a phenomenon called ‘true polar bum’.
It can also cause the Earth’s surface to shift. Their results are more inclined towards plate tectonic movement due to the time interval of this geological movement.
The research has been published in the journal Science Advances.
Earth is moving under our feet: tectonic plates move across the ledge and produce earthquakes as they scrape together
Tectonic plates are made up of the Earth’s crust and the highest portion of the mantle.
Beneath is the asthenosphere: the warm, slimy rock conveyor belt on which the tectonic plates are mounted.
Earth has fifteen tectonic plates (pictured) that together have shaped the shape of the landscape we see around us today.
Earthquakes generally occur at the boundaries of tectonic plates, where one plate dips below another, pushes another upward, or where the edges of the plate are scraped next to each other.
Earthquakes rarely occur in the middle of the plates, but can occur when old faults or cracks far below the surface are reactivated.
These areas are relatively weak compared to the surrounding plate, and can slide easily and cause an earthquake.
