Subscribe to our free daily newsletters
. 24/7 Space News .




Subscribe to our free daily newsletters



Study Solves Pangea Puzzle

Pangea during the Late Triassic showing showing the position of the rifting zone (yellow), the Newark Supergroup (black) and and the Newark basin.
Ann Arbor - Jan. 8, 2001
Researchers at the University of Michigan and the Geological Survey of Norway say they have solved a longstanding and controversial puzzle over the position of Pangea, the ancient supercontinent that began breaking up some 200 million years ago to form today's continents.

Scientists have long known that the continents are not fixed in place on Earth's 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 data -- records of Earth's magnetic field captured in rocks over eons -- have been troubled by data that just don't 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, a professor of geological sciences at U-M. 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.

Now, Van der Voo and colleague Trond Torsvik of the Geological Survey of Norway have found a way to reconcile the paleomagnetic data with the classical Pangea A model.

The key, they say, lies in assumptions about Earth's magnetic field. Scientists generally have assumed the field is like that of a dipole, an object such as a bar magnet, with north and south magnetic poles.

That view is not exactly correct -- the field does have some non-dipole components today -- but because those components vary from century to century, they have been presumed to cancel out over long spans of time.

But suppose, says Van der Voo, "that the main magnetic field wasn't what we have always assumed as perfectly dipolar -- that there was a longstanding non-dipolar field that did not get averaged out."

If that were true, positions indicated by paleomagnetic data would be slightly different from those that assume a purely dipolar field. Sure enough, when Van der Voo and Torsvik performed an analysis they found long-term non-dipole fields, and inclusion of these fields produced a near perfect continental fit with the Pangea A model.

"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."

They presented their findings Dec. 19 at a meeting of the American Geophysical Union in San Francisco.

Related Links
The University of Michigan
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

Building A Crust By The Continent
Toronto - Dec. 6, 2000
by Janet Wong
Scientists believe they have unraveled one of geology's most enduring mysteries about how the Earth's continental crust was built, and they say it happened in a relative blink of an eye.



Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only






Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News








The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.