Featured Research

from universities, journals, and other organizations

Congestion in Earth's mantle: Mineralogists explain why plate tectonics stagnates in some places

Date:
March 31, 2013
Source:
Friedrich-Schiller-Universitaet Jena
Summary:
Seismic measurements show that in some regions of the Earth's mantle, plate tectonics stagnates. The causes of the 'congestion' of the subducted plate are still unknown. In a new study, mineralogists from Germany explain the phenomenon for the first time.

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 Earth and mix with the surrounding Earth's mantle.

Related Articles


Earth is the only planet in our solar system, conducting such a 'facelift' on a regular basis. But the continuous up and down on 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 Nature Geoscience, Prof. Langenhorst and earth scientists of Bayreuth University now explain the phenomenon for the first time.

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 Earth's mantle exactly where the ocean floor submerges particularly fast into the interior of 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."


Story Source:

The above story is based on materials provided by Friedrich-Schiller-Universitaet Jena. Note: Materials may be edited for content and length.


Journal Reference:

  1. W. L. van Mierlo, F. Langenhorst, D. J. Frost, D. C. Rubie. Stagnation of subducting slabs in the transition zone due to slow diffusion in majoritic garnet. Nature Geoscience, 2013; DOI: 10.1038/NGEO1772

Cite This Page:

Friedrich-Schiller-Universitaet Jena. "Congestion in Earth's mantle: Mineralogists explain why plate tectonics stagnates in some places." ScienceDaily. ScienceDaily, 31 March 2013. <www.sciencedaily.com/releases/2013/03/130331165559.htm>.
Friedrich-Schiller-Universitaet Jena. (2013, March 31). Congestion in Earth's mantle: Mineralogists explain why plate tectonics stagnates in some places. ScienceDaily. Retrieved November 20, 2014 from www.sciencedaily.com/releases/2013/03/130331165559.htm
Friedrich-Schiller-Universitaet Jena. "Congestion in Earth's mantle: Mineralogists explain why plate tectonics stagnates in some places." ScienceDaily. www.sciencedaily.com/releases/2013/03/130331165559.htm (accessed November 20, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Thursday, November 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Nations Pledge $9.3 Bn for Green Climate Fund

Nations Pledge $9.3 Bn for Green Climate Fund

AFP (Nov. 20, 2014) — Nations meeting in Berlin pledge $9.3 billion (7.4 bn euros) for a climate fund to help poor countries cut emissions and prepare for global warming, just shy of a $10bn target. Duration: 00:46 Video provided by AFP
Powered by NewsLook.com
What's The Point Of Climate Conferences?

What's The Point Of Climate Conferences?

Newsy (Nov. 20, 2014) — There's optimism about the U.N.'s climate conference in Paris next year, and if climate conferences past are anything to go off, that's notable. Video provided by Newsy
Powered by NewsLook.com
Giant Panda at Toronto Zoo Loves Somersaulting in the Snow

Giant Panda at Toronto Zoo Loves Somersaulting in the Snow

Buzz60 (Nov. 19, 2014) — A giant panda at the Toronto Zoo named Da Mao is celebrating the northeast snowfall by playing and tumbling in the snow in his outdoor enclosure. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Scientists Find Out What's Been Killing Millions Of Starfish

Scientists Find Out What's Been Killing Millions Of Starfish

Newsy (Nov. 18, 2014) — Scientists have found the cause of the biggest marine epidemic in history: the virus behind starfish wasting disease. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins