Geologists matching rocks from opposite sides of the globe have found that part of Australia was once attached to North America 1.7 billion years ago.
Researchers from Curtin University in Australia examinedrocks from the Georgetown region of northern Queensland. The rocks — sandstone sedimentary rocks that formed in a shallow sea — had signatures that were unknownin Australia but strongly resembled rocks that can be seen in present-day Canada.
The researchers, who described their findings online Jan. 17 in the journal Geology, concluded that the Georgetown area broke away from North America 1.7 billion years ago. Then, 100 million years later, this landmass collided with what is now northern Australia, at the Mount Isa region. [Photo Timeline: How the Earth Formed]
“This was a critical part of global continental reorganization when almost all continents on Earth assembled to form the supercontinent called Nuna,” Adam Nordsvan, Curtin University doctoral student and lead author of the study, said in a statement.
Nordsvan added that Nuna then broke apart some 300 million years later, with the Georgetown area stuck to Australia as the North American landmass drifted away.
The continents as we know them today have shifted places throughout Earth’s 4-billion-year history. Most recently, these landmasses came together to form the supercontinent known as Pangaea about 300 million years ago. Geologists are still trying to reconstruct how even earlier supercontinents assembled and broke apart before Pangaea. Scientists first proposed the existence of Nuna, Earth’s first supercontinent, in 2002. Nuna is sometimes called Columbia.
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