Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Atoms under the mantle

08.03.2007
At a depth of 2900 kilometres, the layer between the Earth's mantle and its core has always intrigued geophysicists because they are unable to explain the seismic data it generates. Researchers in the Solid State Structure and Properties Laboratory (CNRS/Université Lille 1/Lille National School for Advanced Chemistry) have studied its deformation which influences convection movements within the mantle or even those by tectonic plates.

Despite the inaccessibility of this layer and the extreme conditions which prevail, they have succeeded in modelling the defects responsible for its deformation. These results, obtained using a novel approach which combines numerical calculus and quantum mechanics, constitute the first step towards modelling deformation of this layer and its effects on the mantle. They are published in the March 1st, 2007 issue of Nature.

Direct access to the Earth's interior is impossible: even the deepest bore holes are only scratches on the surface. Our knowledge of the Earth's interior comes from studying the seismic waves which propagate through the Earth from the focus of an earthquake. We know today that the Earth is divided into layers. The crust on which we live only represents a thin skin. The main shell is called the mantle, a layer made up of solid rock which extends to a depth of up to 2900 kilometres. It surrounds the liquid core which in turn shields the solid core, with a radius of 1200 kilometres. The interface between the mantle and the core, called the D" layer, has long intrigued geophysicists because they are unable to explain the seismic data it generates.

From a mineralogical point of view, 80% of the terrestrial mantle is made up of a silicate (MgSiO3) with a crystalline, perovskite structure. This mineral accounts for half of the Earth's mass. In 2004, several teams (notably from Japan) showed that perovskite became unstable near the core-mantle interface to form a new phase, or post-perovskite. Could post-perovskite deformation explain the seismic signature of the D" layer?

Patrick Cordier and his colleagues based themselves on this hypothesis. But how could a crystalline solid be deformed? The answer lies at the atomic scale: the crystals contain defects called dislocations, which are responsible for plastic deformation. Although their structure is relatively well understood in simple materials such as certain metals (copper, aluminium, etc.), the scientists had little knowledge of the structure of dislocations in complex materials such as minerals, particularly under extreme conditions of pressure. The team in Lille employed a novel approach: instead of reproducing the conditions prevailing inside the Earth in the laboratory, they used a simulation method by injecting the results of quantum mechanics into a numerical model to render it simpler. They are the first to have thus modelled dislocations at the atomic scale for complex materials under extremely high pressure.

The dislocations of which we now know the structure move within the crystal and interact between each other. Scientists thus have access to calculation codes which allow them to describe these interactions. They now want to clarify the behaviour of each grain of crystalline matter, then of the rock and beyond that, of the mantle. A dream? Maybe not. The advances achieved in recent years allow us to be optimistic. So perhaps our voyage to the centre of the Earth will be numerical.

Monica McCarthy | EurekAlert!
Further information:
http://www.crns.fr

More articles from Earth Sciences:

nachricht Geophysicists and atmospheric scientists partner to track typhoons' seismic footprints
16.02.2018 | Princeton University

nachricht NASA finds strongest storms in weakening Tropical Cyclone Sanba
15.02.2018 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>