Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Brown Grad Student’s Seismic Study Shakes Up Plate Tectonics

29.07.2005


Where even rock is weaker - Between 90 and 110 kilometers below ground, Earth’s hard shell – the lithosphere – meets the more pliable asthenosphere. The boundary between the two layers is no more than 11 kilometers thick, according to a new study.


Earth’s cool, rigid upper layer, known as the lithosphere, rides on top of its warmer, more pliable neighbor, the asthenosphere, as a series of massive plates. Plates continuously shift and break, triggering earthquakes, sparking volcanic eruptions, sculpting mountains and carving trenches under the sea.

But what, exactly, divides the lithosphere and the asthenosphere? In the latest issue of Nature, a trio of geophysicists from Brown University and the Massachusetts Institute of Technology publish research that sheds new light on the nature of the boundary between these rocky regions.

Lead author Catherine Rychert, a 26-year-old graduate student in Brown’s Department of Geological Sciences, found a sharp dividing line between the lithosphere and the asthenosphere, according to data culled from seismic sensors sprinkled across the northeastern United States and southeastern Canada. Rychert and colleagues discovered that sound waves recorded by the sensors slow considerably about 90 to 110 kilometers below ground – a sign that the rock is getting weaker and that the lithosphere is giving way to the asthenosphere. Within in a distance of a mere 11 kilometers – roughly 7 miles or less – the transition is complete.



This evidence runs contrary to the prevailing notion that the lithosphere-asthenosphere transition is a gradual one. It also points up the fact that temperature alone cannot define the boundary. Rychert said that water or a small amount of partly molten rock must also be present in the asthenosphere to cause such an abrupt change in the mechanical strength of the rock.

“These findings will be controversial because they run counter to what some scientists believe is true,” Rychert said. “Regardless, they’re pretty cool. We know something new, literally, about the earth under our feet.”

To conduct the study, Rychert gathered seismic data from hundreds of earthquakes recorded during more than five years at six government-operated or university-run research stations in Canada, New Hampshire, Massachusetts, New York and Pennsylvania. She modeled and analyzed the data with the assistance of Karen Fischer, the Royce Family Professor of Teaching Excellence and professor of geological sciences at Brown, and Stéphane Rondenay, the Kerr-McGee Assistant Professor of Seismology at MIT and a former postdoctoral research fellow at Brown. The project took three years to complete.

“We initially were very surprised by the sharpness of the lithosphere-asthenosphere boundary indicated by the data,” said Fischer, “and so I challenged Kate to prove that such a rapid transition is definitively required. All of her careful modeling has now paid off with a result that makes a fundamental contribution to our understanding of the Earth’s lithosphere.”

The Geophysics Program at the National Science Foundation funded the work.

Wendy Lawton | EurekAlert!
Further information:
http://www.brown.edu

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>