Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Suction and pull drive movement of Earth’s plates, U-M researchers show

04.10.2002


As anyone with a smattering of geological knowledge knows, Earth’s crust is made up of plates that creep over the planet’s surface at a rate of several inches per year. But why do they move the way they do? Even experts have had trouble teasing out the exact mechanisms.



A model developed by University of Michigan researchers and published in the Oct. 4 issue of Science provides a relatively simple explanation.

"It’s been known that slabs (portions of plates that extend down into the Earth) drive convection in Earth’s mantle, and ultimately the motion of the surface plates, but it hasn’t been well established exactly how that happens---the ideas have been fairly vague," says Clinton Conrad, a postdoctoral fellow in the department of geological sciences. "In this paper, we’ve been able to describe more precisely how slabs interact with the plates."


When two plates collide, one is forced down beneath the other into the mantle (the plastic-like layer between Earth’s crust and core that flows under pressure), creating what geologists call a subduction zone. Because subducting slabs are colder and denser than surrounding mantle material, they tend to sink like a lead ball in a vat of molasses.

There are two main ways these sinking slabs might influence plate motion. If a slab is attached to a plate, the slab can directly pull the plate toward the subduction zone. A slab that is not well attached to a plate, on the other hand, can’t pull directly on the plate. Instead, as it sinks, it sets up circulation patterns in the mantle that exert a sort of suction force, drawing nearby plates toward the subduction zone much as floating toys are drawn toward the outlet of a draining bathtub.

To understand the relative importance of slab pull and slab suction forces, Conrad and assistant professor of geological sciences Carolina Lithgow-Bertelloni, with whom he worked on the project, developed models in which: 1) only slab suction was operating; 2) only slab pull was operating; and 3) both slab suction and slab pull were at work. Then they compared the plate motions that would result from each of these scenarios with actual plate motions. The best fit was the model that combined slab pull and slab suction forces.

The model also explained an observation that has baffled geodynamicists for some time. "The way the observation was originally framed was that plates that have continents on them are slow, compared to plates that are only oceanic," says Lithgow-Bertelloni. But the real issue is whether or not the plates have slabs attached, she explains. Overriding plates, which have no slabs, are slower than subducting plates, which have slabs. The explanation? Subducting plates move faster because the pull effect acts directly on them, making them move rapidly toward the subduction zone. Overriding plates are also drawn toward the subduction zone---by the suction effect---but at the same time, the pull effect creates forces in the mantle that counteract that motion. The net effect is that overriding plates move more slowly toward the subduction zone than subducting plates do.

"We’ve been able to explain that the difference in speed occurs because slab pull generates mantle flow that counteracts the motion of the overriding plate," says Lithgow-Bertelloni. "We also found that this effect is only important for slabs in the upper 600 to 700 kilometers of the mantle. Any slabs deeper than 700 kilometers do not contribute to this effect. They’re important for driving flow in the mantle, but they’re not important for the pull."

Nancy Ross-Flanigan | EurekAlert!
Further information:
http://www.geo.lsa.umich.edu/dept/faculty/lithgowbertelloni/index.html
http://pubs.usgs.gov/publications/text/understanding.html
http://www.platetectonics.com/

More articles from Earth Sciences:

nachricht First research results on the "spectacular meteorite fall" of Flensburg
18.02.2020 | Westfälische Wilhelms-Universität Münster

nachricht The Antarctica Factor: model uncertainties reveal upcoming sea-level risk
14.02.2020 | Potsdam-Institut für Klimafolgenforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

Im Focus: Skyrmions like it hot: Spin structures are controllable even at high temperatures

Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices

The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...

Im Focus: Making the internet more energy efficient through systemic optimization

Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.

Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.

Im Focus: New synthesis methods enhance 3D chemical space for drug discovery

After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.

"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

"Make two out of one" - Division of Artificial Cells

19.02.2020 | Life Sciences

High-Performance Computing Center of the University of Stuttgart Receives new Supercomuter "Hawk"

19.02.2020 | Information Technology

A step towards controlling spin-dependent petahertz electronics by material defects

19.02.2020 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>