DID the Earth's magnetic poles once lie near the equator? That could explain puzzling changes in the magnetism of rocks millions of years ago.
The Earth's magnetic poles are aligned along roughly the same axis as its rotational poles. Geologists have assumed this was also true in the past, so they use volcanic rocks, which when they formed took on an imprint of the direction and strength of the Earth's magnetic field, to infer the rocks' original latitude and to trace continental motions over the past billion years.
But doing this for rocks in North America and eastern Europe is turning up a conundrum. In both regions, there appear to be rocks that were at the equator at some points between 550 and 600 million years ago and near the poles for other parts of this time period.
That would imply that the ancient continents sped across the surface at ...
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