Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New data shakes accepted models of collisions of the Earth's crust

09.02.2007
New research findings may help refine the accepted models used by earth scientists over the past 30 years to describe the ways in which continents clash to form the Earth's landscape.

Eric Calais, an associate professor of geophysics at Purdue University, in collaboration with Ming Wang and Zenghang Shen from the Institute for Geology and Earthquake Science in China, used global positioning systems to record the precise movements of hundreds of points on the continent of Asia over a 10-year period.

"Prior to this, we had only partial regional views that were sometimes inconsistent with each other," Calais said. "With this work, we addressed a fundamental question that geologists have been debating for the past 40 years: Are continents strong and brittle or weak and viscous?"

The "strong and brittle" theory suggests continents break into pieces during collisions of the tectonic plates, pieces of the Earth's crust into which the continents are embedded. The "weak and viscous" theory suggests, on the contrary, that continents thicken and flow upon collision.

The data collected by Calais and his team, reported in the Dec. 30 issue of Geophysical Research Letters, suggests the answer is a combination of both theories. His team found that the surface of the Asian continent behaves differently in areas of high elevation, such as mountains.

"We found that most of Asia is very strong and breaks like a ceramic plate, much like what would be predicted by classic plate tectonics, but there also are large chunks like Tibet and the Tien Shan mountains that seem to deform more like Play-Doh," he said.

The Indian and Eurasian tectonic plates collide at a rate of 38 millimeters, or about one and one-half inches, per year. This slow-motion crash is responsible for the formation of the Himalayas and holds up the Tibetan Plateau, Calais said.

"These movements happen slowly over millions of years, but the impact is tremendous because of the huge masses involved," he said. "When the Earth's crust is put under stress, it deforms. Like a rubber band, the crust can only take so much stress before it breaks, causing an earthquake. We must understand the stresses and their accumulation in the Earth's crust to better understand earthquakes and, eventually, save lives."

The continent of Asia, home to more than 3 billion people, has had some of the largest earthquakes in the recent past, but areas in the United States also are deforming.

"The western third of North America is seismically active," Calais said. "The most well-known area is along the San Andreas Fault in California, but there also is deformation occurring across the Nevada desert, along the Wasatch Mountains in Utah, and further south in Colorado and New Mexico. The National Science Foundation is currently funding a large research effort called the "Plate Boundary Observatory" to apply this same method to study the Western United States."

Calais and his team gathered data from geodetic markers, metal pins about the size of a pen, that they placed in some of the most remote areas of the world, including Siberia and Mongolia. The markers remain in place for use in future studies. They are surveyed for a few days every year by GPS tracking equipment, which is then removed once the data is collected. The tops of the markers have a 1-millimeter-wide dimple that is the actual point tracked by the equipment.

The team tracked changes in height and horizontal movements and compared each site to those surrounding it to determine if the larger area responded to forces as a rigid or malleable segment. If the movement of sites within an area was consistent with a rigid rotation, it could be confirmed that the area fit the strong and brittle theory. However, a change in height did not necessarily mean an area fit the weak and viscous theory, Calais said.

"The change in height of an individual site could be a sign of thickening or it could mean that a rigid block is uplifting as a whole," he said. "We had to look at the behavior of the neighboring sites as well to accurately understand what was happening to the area as a whole."

The team also pulled data from existing tracking stations and through contributions from collaborators, including scientists in Russia and Kirgistan.

"International collaboration was essential for us to achieve a complete view of the surface deformation of the continent," Calais said.

The precision of the team's techniques and use of GPS allowed researchers to track movement as small as 1 millimeter per year. The team plans to place additional GPS tracking points to increase the resolution of their continentwide measurements in the future.

"This is beyond plate tectonics and theories," he said. "We now have the ability to directly measure how continents deform and to use that information to validate or invalidate theories of why this happens."

The National Science Foundation funded this research.

Writer: Elizabeth Gardner, (765) 494-2081, ekgardner@purdue.edu

Source: Eric Calais, (765) 496-2915, ecalais@purdue.edu

Purdue News Service: (765) 494-2096; purduenews@purdue.edu

Elizabeth Gardner | EurekAlert!
Further information:
http://www.purdue.edu/eas/

More articles from Earth Sciences:

nachricht Radioactivity from oil and gas wastewater persists in Pennsylvania stream sediments
22.01.2018 | Duke University

nachricht World’s oldest known oxygen oasis discovered
18.01.2018 | Eberhard Karls Universität Tübingen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Thanks for the memory: NIST takes a deep look at memristors

22.01.2018 | Materials Sciences

Radioactivity from oil and gas wastewater persists in Pennsylvania stream sediments

22.01.2018 | Earth Sciences

Saarland University bioinformaticians compute gene sequences inherited from each parent

22.01.2018 | Life Sciences

VideoLinks Wissenschaft & Forschung
Overview of more VideoLinks >>>