THE Grand Canyon in Arizona has a bizarre Antipodean link. A chunk of the rock sequence that has been sliced through to form this natural wonder of the world now sits thousands of kilometres away in Tasmania, Australia.
To peer into the Grand Canyon is to behold, in its rock layers, a record of Earth鈥檚 distant past. The oldest layers at the bottom date back more than 1.5 billion years.
It is some of the most ancient layers in the sequence that interest Jack Mulder, a geologist at Australia鈥檚 Monash University. He thinks these rocks 鈥� which are between about 1.1 and 1.2 billion years old 鈥� look just like similarly ancient rocks in Tasmania.
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The Tasmanian rocks in question have always seemed a bit out of place, he says. 鈥淭hey didn鈥檛 look a lot like similarly aged rocks nearby.鈥�
Mulder and his colleagues have now found that the rocks contain minerals with the same 鈥済eochemical fingerprint鈥� as those in the Grand Canyon (Geology, ).
鈥淲e concluded that although it鈥檚 now on the opposite side of the planet, Tasmania must have been attached to the western United States,鈥� he says.
鈥淲e concluded that Tasmania must have been attached to the western United States鈥�
Beyond extending the Grand Canyon鈥檚 reach across the Pacific and into the southern hemisphere, uniting the Tasmanian rocks with those in North America helps to solve an ancient geological jigsaw puzzle.
About a billion years ago, all of Earth鈥檚 continental plates formed a single supercontinent called Rodinia. But working out exactly how today鈥檚 continents would once have fitted together to form Rodinia is no simple task given how long ago it existed. The Tasmanian discovery provides a clue because it is clear evidence that North America and Australia were linked together at the time.
鈥淛ack鈥檚 paper shows that Tasmania holds the key to tying together the tectonic geography of the time,鈥� says Alan Collins at the University of Adelaide, Australia. 鈥淚t鈥檚 really a good link and tie that allows us to build full plate models of the ancient Earth.鈥�
This article appeared in print under the headline 鈥淎ustralia鈥檚 Grand Canyon connection鈥�
