Above is a representation of what has often been dubbed Pangea A, a
of how the continents might have fit together when they were tightly
clustered. This model, based on geological evidence, has been widely
accepted and reproduced. The maps below represent two efforts to make
continents fit with paleomagnetic data, which often has run contrary to
the Pangea A model.
Now U-M geologist Rob Van der Voo and colleague Trond Torsvik have found a way to reconcile the paleomagnetic data with the classical Pangea A model.
Maps based on those featured in Nature
Scientists have long known that the continents are not fixed in place on Earths surface, but gradually change positions over millions of years. Based on geological evidence, researchers have come up with several models that show how the continents might have fit together when they were tightly clustered. One widely accepted model, dubbed Pangea A and reproduced in countless textbooks, shows what is now South America nestled against the southern edge of North America, with Africa just east of South America, adjacent to the Atlantic coast of North America and southwest of Europe.
But geologists who study paleomagnetic datarecords of Earths magnetic field captured in rocks over eonshave been troubled by data that just dont fit the Pangea A model. Paleomagnetic data reveal the latitude at which rocks were located when the magnetization was recorded. That information, in turn, provides clues to the positions of the continents.
The problem is that, according to the paleomagnetic data, the southern continents should be a little bit farther north than they are in the Pangea A model, explains Rob Van der Voo, professor of geological sciences. That dilemma has led to alternative models that place northwestern South America along the east coast of North America or push it even farther east to lie just south of Europe. While the revised models may satisfy researchers who specialize in paleomagnetism, they gall other geologists who find no evidence in fossils or mountain chains to suggest that the continents have ever been in those positions.
The broader implications of this study, says Van der Voo, are that paleomagnetic results for other times and other continental configurations must now be re-evaluated with the new geomagnetic field model that should include some 10 percent non-dipole fields, and this will keep us busy for decades.