Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Earth’s core rotates faster than its crust, scientists say

26.08.2005


Scientists have ended a 9-year-old debate by proving that Earth’s core rotates faster than its surface, by about 0.3 to 0.5 degree per year.

"Extraordinary claims require extraordinary proof," said Xiaodong Song, a professor of geology at the University of Illinois at Urbana-Champaign and corresponding author of a paper to appear in the Aug. 26 issue of the journal Science. "We believe we have that proof."

Earth’s iron core consists of a solid inner core about 2,400 kilometers in diameter and a fluid outer core about 7,000 kilometers in diameter. The inner core plays an important role in the geodynamo that generates Earth’s magnetic field, and an electromagnetic torque from the geodynamo is thought to drive the inner core to rotate relative to the mantle and crust.



The first observational evidence for differential rotation was presented in 1996 by Song and Paul Richards, a seismologist at the Lamont-Doherty Earth Observatory of Columbia University. For the past nine years, some seismologists have suspected that flaws, or artifacts, in the data were responsible for the purported movement.

By comparing historical seismic waves traversing Earth’s fluid and solid cores, Song and his colleagues found compelling evidence for differential rotation of the solid inner core. The researchers reported observations of 17 sets of similar seismic waves – called waveform doublets – from earthquakes occurring in the South Sandwich Islands region off the coast of South America.

The doublets, which were recorded at up to 58 seismic stations in and near Alaska with a time separation of up to 35 years, allowed the researchers to detect temporal changes along the sampling paths.

"The similar seismic waves that passed through the inner core show systematic changes in travel times and wave shapes when the two events of the doublet are separated in time by several years," Song said. "The only plausible explanation is a motion of the inner core."

The most likely explanation for why the inner core is rotating at a different speed, Song said, is electromagnetic coupling. "The magnetic field generated in the outer core diffuses into the inner core, where it generates an electric current. The interaction of that electric current with the magnetic field causes the inner core to spin, like the armature in an electric motor."

The fluid outer core decouples the solid inner core’s movement from the mantle. Because the fluid outer core is not very viscous, frictional drag is small.

"Differential rotation is a fundamental dynamic process that goes to the heart of the origin of our planet and how it has evolved," Song said. "There is still much to learn about the inner Earth."

James E. Kloeppel | EurekAlert!
Further information:
http://www.uiuc.edu

More articles from Earth Sciences:

nachricht NASA looks to solar eclipse to help understand Earth's energy system
21.07.2017 | NASA/Goddard Space Flight Center

nachricht Scientists shed light on carbon's descent into the deep Earth
19.07.2017 | European Synchrotron Radiation Facility

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

Ultrathin device harvests electricity from human motion

24.07.2017 | Power and Electrical Engineering

Scientists announce the quest for high-index materials

24.07.2017 | Materials Sciences

ADIR Project: Lasers Recover Valuable Materials

24.07.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>