Geologists Show Tasmania and the Grand Canyon Were Connected on Ancient Supercontinent

Rocks from Arizona’s Unkar Group and Tasmania’s Rocky Cape Group were likely part of the same formation 1.1 billion years ago on the supercontinent Rodinia.

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Oct 25 2018, 8:02pm

Grand Canyon Unkar Group. Image: Doc Searles

Arizona’s Grand Canyon and the Australian island of Tasmania are about 8,000 miles apart, as the crow flies. But over the past few years, geologists noticed that some of the oldest rocks in Tasmania look like they could have been pulled straight out of the Grand Canyon.

It turns out over a billion years ago, these two disparate locations were part of the same rock formation in the long-lost supercontinent of Rodinia, according to a study published this month in Geology.

Led by Jacob Mulder, a research fellow at Monash University in Melbourne, the study compares the chemical composition and geological age of rocks in the Unkar Group at the Grand Canyon with the Rocky Cape Group in Tasmania. Both sites date back about 1.1 billion years to the late Mesoproterozoic era, and they contain matching hafnium isotopes readings.

"We concluded that although it’s now on the opposite side of the planet, Tasmania must have been attached to the western United States," Mulder told New Scientist .

Though it doesn’t have the name recognition of Pangaea, the gigantic landmass that existed during the Triassic period, Rodinia represented an important stage in Earth’s continental evolution.

Formed from the broken pieces of an even older supercontinent called Columbia, Rodinia would have been a barren landscape because terrestrial life had not yet evolved. The continent broke up about 800 million years ago in part due to large upwellings in Earth’s molten mantle.

Read More: Researchers Discover Oldest-Ever Evidence of Animals on Earth

Scientists have been trying to reconstruct how Rodinia fit together for years, but it’s like trying to to solve a puzzle that disassembles and reassembles itself in different forms. That’s why identifying two key puzzle pieces—such as the Unkar Group (in the Grand Canyon) and the upper Rocky Cape Group (in Tasmania)—is so crucial. Not only does the study link Arizona and Tasmania across time and space, it is another step towards understanding how our modern world evolved from this bygone supercontinent.

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