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 In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

nachricht Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Comet or asteroid? Hubble discovers that a unique object is a binary

21.09.2017 | Physics and Astronomy

Cnidarians remotely control bacteria

21.09.2017 | Life Sciences

Monitoring the heart's mitochondria to predict cardiac arrest?

21.09.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>