Apr 14, 2025 04:09 PM
https://www.livescience.com/planet-earth...nics-began
EXCERPTS: . . . These findings are important for the debate over when our planet's plate tectonics began. No one knows exactly when or why the Earth's surface broke into pancake-like slabs that grind and crash against one another, forming mountains and volcanoes and triggering earthquakes.
Historically, the fact that chemical signatures seen in modern plate tectonic processes occurred in protocrust from Earth's first billion years, during the Hadean eon, had been used as evidence to support the theory that plate tectonics started nearly as soon as Earth had solid ground — roughly 4 billion years ago.
"That's probably a flawed argument now," study lead author Craig O'Neill, a geophysicist at Queensland University of Technology in Australia [...] The precise signatures under debate are trace elements, such as titanium and niobium, which combine in the crystal structure of rocks as they solidify from hot magma. However, the behavior of these elements depends heavily on the conditions around them.
[...] The researchers modeled the behavior of these trace elements under the conditions of the first few hundred millions of years of Earth, a time when the crust, core and mantle were still differentiating and the developing mantle was still iron-rich. ... "Some of the evidence people have been using to argue for early plate tectonics is probably not showing you [later] plate tectonics at all," he said. "It's probably showing you older crust."
That doesn't mean plate tectonics wasn't happening at that time, at least on occasion, O'Neill added. There was plenty of debris zipping around the young solar system and Earth was frequently bombarded with impacts, some of which would have been big enough to crack the protocrust and start localized periods of subduction.
But the whole planet probably transitioned to the plate tectonic system later, between 3.2 billion and 2.7 billion years ago...... (MORE - missing details)
EXCERPTS: . . . These findings are important for the debate over when our planet's plate tectonics began. No one knows exactly when or why the Earth's surface broke into pancake-like slabs that grind and crash against one another, forming mountains and volcanoes and triggering earthquakes.
Historically, the fact that chemical signatures seen in modern plate tectonic processes occurred in protocrust from Earth's first billion years, during the Hadean eon, had been used as evidence to support the theory that plate tectonics started nearly as soon as Earth had solid ground — roughly 4 billion years ago.
"That's probably a flawed argument now," study lead author Craig O'Neill, a geophysicist at Queensland University of Technology in Australia [...] The precise signatures under debate are trace elements, such as titanium and niobium, which combine in the crystal structure of rocks as they solidify from hot magma. However, the behavior of these elements depends heavily on the conditions around them.
[...] The researchers modeled the behavior of these trace elements under the conditions of the first few hundred millions of years of Earth, a time when the crust, core and mantle were still differentiating and the developing mantle was still iron-rich. ... "Some of the evidence people have been using to argue for early plate tectonics is probably not showing you [later] plate tectonics at all," he said. "It's probably showing you older crust."
That doesn't mean plate tectonics wasn't happening at that time, at least on occasion, O'Neill added. There was plenty of debris zipping around the young solar system and Earth was frequently bombarded with impacts, some of which would have been big enough to crack the protocrust and start localized periods of subduction.
But the whole planet probably transitioned to the plate tectonic system later, between 3.2 billion and 2.7 billion years ago...... (MORE - missing details)