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 Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Silicon solar cell of ISFH yields 25% efficiency with passivating POLO contacts

08.12.2016 | Power and Electrical Engineering

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>