Did Antarctica Migrate South for the Winter?
How much do we really know about the history of our world and the migrations of its surface? It now seems that scientists have discovered mineralogical similarities between Antarctica and North America, implying that either they were at one point neighbors, or that materials were somehow transported from one region to the other.
The motion of tectonic plates continually rearranges Earth’s continents, sometimes cramming most or all of them into immense groupings called supercontinents.
Millions of years ago, the American Southwest sat next to East Antarctica
What a juxtaposition: About 800 million years ago, East Antarctica, now one of the coldest regions on Earth, abutted what is now California’s Death Valley, one of the hottest.
Both locales were part of an equatorial supercontinent called Rodinia, says John Goodge, a geologist at the University of Minnesota Duluth.
There has, however, been considerable confusion and controversy over the issue of land masses going back that far in time.
Debate has long raged about how today’s landmasses were arranged then, says Goodge. The orientation of magnetic lines locked into rocks that formed at the time — which often can be used to estimate the location and orientation of ancient landmasses — are in many cases contradictory ...
There seems to have been little agreement as to how land masses were arranged that far back.
In previous studies, various teams have argued that Australia, southern China, or even Siberia lay along the southwestern edge of Laurentia, a landmass that held most of what is now North America.
How does the latest finding relate to the relationship between continents? Contrary to prior suggestions that Australia, China or Sibera lay along the southwest of Laurentia, it seems that at some point either the continents of Antarctica and North America were situated near one another, or that somehow materials were transferred from one to the other.
Now, geochemical analyses of rock samples taken from the Transantarctic Mountains hint instead that portions of East Antarctica occupied that spot, Goodge and his colleagues report in the July 11 Science. For one thing, the ratios of neodymium isotopes in the ancient sediments in the Transantarctic Mountains are the same as those in what was then Laurentia, says Goodge. Also, the hafnium isotope ratios in the 1.44-billion-year-old zircons found in East Antarctica match those of the zircons found in the distinctive granites now found primarily in North America.
Finally, the researchers note, the ratios of various isotopes and elements in a basketball-sized chunk of granite found in East Antarctica — a chunk ripped by a glacier from bedrock now smothered by thick ice, the team speculates — match those of granite found only in what was southwestern Laurentia, which today is the American Southwest.
Mineralogical analysis has shown a striking resemblance between materials of Antarctica and North America. Is it really possible that Antarctica has migrated from an equatorward position to the south polar position it now occupies?
If not, what might the material similarities mean? Did the similar materials evolve independently? Were they somehow transported?
More research in undoubtedly required.