supercontinent, starting with its name. “Nuna” is from the Inuktitut language of the Arctic. It means lands bordering the northern oceans, so dubbed for the supercontinent’s Arctic-fringing components. But some researchers prefer to call it Columbia after the Columbia region of North America’s Pacific Northwest.
Whatever its moniker,
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, Nuna/Columbia is an exercise in trying to get all the puzzle pieces to fit. Because Nuna existed so long ago, subduction has recycled many rocks of that age back into the deep Earth,
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, erasing any record of what they were doing at the time. Geologists travel to rocks that remain in places like India,
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, South America and North China, analyzing them for clues to where they were at the time of Nuna.
One of the most promising techniques targets magnetic minerals. Paleomagnetic studies use the minerals as tiny time capsule compasses,
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, which recorded the direction of the magnetic field at the time the rocks formed. The minerals can reveal information about where those rocks used to be,
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, including their latitude relative to where the Earth’s north magnetic pole was at the time.
Salminen has been gathering paleomagnetic data from Nuna-age rocks in Brazil and western Africa. Not surprisingly, given their current lock-and-key configuration, these two chunks were once united as a single ancient continental block,
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, known as the Congo/S?o Francisco craton. For millions of years,
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, it shuffled around as a single geologic unit,
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, occasionally merging with other blocks and then later splitting away.
Salminen has now figured out where the

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