Deep within Colombian volcanic rock, scientists have found a quieter past than expected — magnetic signatures preserved in ancient stone reveal that the great collision between Central and South America's tectonic plates reached its most violent crescendo not in the late Miocene, as long assumed, but tens of millions of years earlier, during the Oligocene and middle Miocene. A team led by Victor Piedrahita and J. Li read this history not from fossils or sediment, but from the subtle orientation of magnetic minerals locked inside lava that cooled between 12 and 6 million years ago. The relative