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 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: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

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...

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

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>