Old cliffs show earliest proof of tectonic activity on earth

Cliffs in Australia present evidence that plates in the Earth’s crust were moving 3.5 billion years ago, a finding that pushes back at the beginning of plate tectonics of hunter of millions of years.

Today, about eight wines, stiff stones of stones are pulled on the surface of the planet, plus some smaller plates, pulled or pushed along a softer layer of stone underneath. When the edges of these plates slide or slide past another, sudden geological events may occur, such as earthquakes, as well as a more gradual process, such as the formation of mountain pidies.

But geologists disagree about how many records once were when they started moving and how they used to move. Some researchers claim that they have found evidence from as far back as 4 billion years ago, when the planet was meaningful, while others say the strongest evidence is newer, from 3.2 billion years ago.

Most of this evidence consists of hints of the chemical composition of cliffs that geologists can use to derive how these rocks moved in the past. However, there is little overview of how early plates may have moved in relation to each other, which is seen as the strongest proof of tectonic record movements.

Now, ALEC Brenner at Yale University and his colleagues says they have found clear evidence of relative flat movements about 3.5 billion years ago in Eastern Pilbara Craton in Western Australia. The researchers asked how the magnetic field in the rocks, which were in line with the Earth’s magnetic field, moved over time, similar to how a compass buried in the rock would change the needle direction as the earth moved.

Brenner and his team first date the rocks by analyzing the radioactive isotopes they contain, and then proven that Rocks’ magnetization had not been reset at some point. By tracking how this magnetization had moved, they could show that the entire rock region was migrated over time at a speed of tens of thousands of centimeters a year. Then they compared this to cliffs that had been date and tracked using the same technique in the Barberton Grestone belt in South Africa, which showed no movement.

“This means there may have been a kind of platform between these two [regions] to meet the relative movement. It’s record movement, definition, ”Brenner told Goldschmidt Geochemistry conference in Prague, Czech Republic, July 9.

“Pilbara, about 3.8 billion years ago, moves from the middle of high latitudes to very high latitudes, news with the area of the geomagnetic pole, and probably close to maker, where Svalbard’s latitude is today, in just a few million years. While the barber tone is just there, it doesn’t matter much,” Brenner said.

“If two plates move compared to each other, there have also been a lot of things going on in between,” says Robert Hazen at the Carnegie Institution for Science in Washington DC. “It can just be a whole local thing.”

But there is the possibility of different interpretations of what caused this movement, says Hazen. This is partly because there is a broad uncertainty about how fast the plate was moving and the data could fit several different theories about what the Earth’s interior looked like at the time.

At least the finding involves the existence of a tectonic border, says Michael Brown at the University of Maryland. However, he says that the movement of the rocks seems significantly different from what we understand as platform tectonics today. “In essence, Pilbara [plate] Going steaming up to higher latitudes and stopping dead, which is unusual in any plate tectonic context. “

Brown claims that this fits with a theory that the Earth’s crust at that time was composed of Mayry smaller plates pushed around by columns with hot stone, called plumes waving from the more melted mantle. The surviving maintenance of these smaller plates, which in this view Brenner and his team would have sampled from, are useful to indicate that there was movement, but because they are only a small part of the crust, they may not be representative of how the earth moved.

Brenner and his team also found evidence that the Earth’s magnetic field direction turned 3.46 billion years ago, which is 200 million years before the next post-purely flip. Unlike today’s magnetic field, which turns about every 1 million years, the magnetic field then seemed to turn less often at a rate of tens of thousands of millions of years. This can involve “completely different underlying driving energy and mechanisms,” Brenner said.

What the Earth’s magnetic field looked like at the time in its development is also warmly discussed, says Hazen, partly because of the lack of magnetic data. “I think this is moving the bar,” he says. “It’s a real opinion that it’s so early to find a turn. It tells you something about the geodynamics of the core that wasn’t spiced down.