Areas that are now northern Alabama and northeastern South America were once neighbors, according to a new study. The research also suggests that a 3000-kilometer-long swath of magnetized rocks beneath North America—what geologists call the Midcontinent Rift (depicted in red at upper left of this gravity map)—formed just before tectonic activity separated those areas. Geologists have long thought these rocks were remnants of lava from an extended period of widespread volcanic activity and that the ancient supercontinent split much later. But several recent studies, including fieldwork by another team in northeastern South America, suggest that the split did occur that time after all. Tectonic activity cleaved a portion of modern-day North America called Laurentia from a piece of South America known as Amazonia about 1.1 billion years ago—just as volcanism that formed the Midcontinent Rift ended, the researchers reported in the 16 March issue of Geophysical Research Letters.