Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Congestion in the Earth’s Mantle

01.04.2013
Mineralogists of the Universities Jena and Bayreuth explain in the science magazine ‘Nature Geoscience‘ why plate tectonics stagnates in some places

The Earth is dynamic. What we perceive as solid ground beneath our feet, is in reality constantly changing. In the space of a year Africa and America are drifting apart at the back of the Middle Atlantic for some centimeters while the floor of the Pacific Ocean is subducted underneath the South American Continent.

“In 100 million years’ time Africa will be pulled apart and North Australia will be at the equator,” says Prof. Dr. Falko Langenhorst from the Friedrich Schiller University Jena (Germany). Plate tectonics is leading to a permanent renewal of the ocean floors, the mineralogist explains. The gaps between the drifting slabs are being filled up by rising melt, solidifying to new oceanic crust. In other regions the slabs dive into the deep interior of the Earth and mix with the surrounding Earth’s mantle.

The Earth is the only planet in our solar system, conducting such a ‘facelift’ on a regular basis. But the continuous up and down on the Earth`s crust doesn’t run smoothly everywhere. “Seismic measurements show that in some mantle regions, where one slab is subducted underneath another one, the movement stagnates, as soon as the rocks have reached a certain depth,” says Prof. Langenhorst. The causes of the ‘congestion‘ of the subducted plate are still unknown. In the current issue of the science magazine ‘Nature Geoscience‘ Prof. Langenhorst and earth scientists of Bayreuth University now explain the phenomenon for the first time (DOI: 10.1038/NGEO1772).

According to this, the rocks of the submerging ocean plate pond at a depth of 440 to 650 kilometers – in the transition zone between the upper and the lower Earth mantle. “The reason for that can be found in the slow diffusion and transformation of mineral components,“ mineralogist Langenhorst explains. On the basis of high pressure experiments the scientists were able to clarify things: under the given pressure and temperature in this depth, the exchange of elements between the main minerals of the subducted ocean plate – pyroxene and garnet – is slowed down to an extreme extent. “The diffusion of a pyroxene-component in garnet is so slow, that the submerging rocks don’t become denser and heavier, and therefore stagnate,“ the Jena scientist says.

Interestingly there is congestion in the earth mantle exactly where the ocean floor submerges particularly fast into the interior of the Earth. “In the Tonga rift off Japan for example, the speed of subduction is very high,” Prof. Langenhorst states. Thereby the submerging rocks of the oceanic plate stay relatively cold up to great depth, which makes the exchange of elements between the mineral components exceptionally difficult. “It takes about 100 Million years for pyroxene crystals which are only 1 mm in size to diffuse into the garnet. For this amount of time the submerging plate stagnates,” Langenhorst describes the rock congestion. It can probably only diffuse at the boundary of the lower Earth mantle. Because then pyroxene changes into the mineral akimotoite due to the higher pressure in the depth of 650 kilometers. “This could lead to an immediate rise in the rock density and would enable the submerging into greater depths.“

Original Publication:
Van Mierlo VL et al. Stagnation of subducting slabs in the transition zone due to slow diffusion in the majoritic garnet. Nature Geoscience, DOI: 10.1038/NGEO1772
Contact:
Prof. Dr. Falko Langenhorst
Institute for Geosciences
Friedrich Schiller University Jena
Carl-Zeiss-Promenade 10
D-07745 Jena
Germany
Email: falko.langenhorst[at]uni-jena.de

Dr. Ute Schönfelder | idw
Further information:
http://www.uni-jena.de

More articles from Earth Sciences:

nachricht Supercomputing helps researchers understand Earth's interior
23.05.2017 | University of Illinois College of Liberal Arts & Sciences

nachricht How is climate change affecting fauna in the Arctic?
22.05.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

 
Latest News

Scientists propose synestia, a new type of planetary object

23.05.2017 | Physics and Astronomy

Zap! Graphene is bad news for bacteria

23.05.2017 | Life Sciences

Medical gamma-ray camera is now palm-sized

23.05.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>