Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Full body scan: Imaging project offers view inside Earth

05.12.2003


Results may help settle debate about how Earth sheds its internal heat



Like doctors taking a sonogram of a human body, Princeton geoscientists have captured images of the interior of the Earth and revealed structures that help explain how the planet changes and ages.

The scientists used tremors from earthquakes to probe the inside of the planet just as sound waves allow doctors to look inside a mother’s womb. The technique, a greatly refined version of earlier efforts, produced a surprisingly sharp image and yielded the first direct measurements of giant spouts of heat, called mantle plumes, that emanate from deep within the planet.


Mantle plumes are believed to cause island chains, such as the Hawaiian Islands and Iceland, when the Earth’s crust passes over the column of heat. Although accepted by most scientists, the existence of mantle plumes has been fiercely contested by a minority of researchers in recent years.

"This is the first visual evidence that mantle plumes exist," said Raffaella Montelli, a Princeton geoscientist and the lead author of a paper published online by the journal Science on Dec. 4. "There is still a very open debate, but we are saying ’Look, here they are; you can see them.’"

Montelli, who received a Ph.D. from Princeton this year and is now a postdoctoral fellow, conducted the study in collaboration with Princeton professors Guust Nolet and Tony Dahlen as well as Guy Masters of the University of California-San Diego, Robert Engdahl of the University of Colorado and Shu-Huei Hung of National Taiwan University.

The scientists used data from more than 3,000 seismographic stations around the world. The stations monitored tremors from more than 86,000 earthquakes since 1964. The seismic waves change speed slightly when they encounter different temperatures and materials in the Earth, said Nolet. In particular, the waves slow down when they encounter warm spots where the rock is very slightly softer than in cooler spots.

"If we can find out if waves are being slowed down or speeded up, then we know whether the Earth is locally hotter or colder," Nolet said. The researchers analyzed these changes in speed and assembled their data into a three-dimensional temperature map. They immediately noticed broad columns of warm material rising out of the Earth’s mantle, which is the layer nearly 2,000 miles thick just under the crust.

"We started the research without any thought of mantle plumes," said Nolet. Their goal was to improve on a century-old theory of how seismic waves travel through the Earth, taking into account how the waves interact with varying temperatures and materials. In addition to developing a better theory, the researchers selected only the highest quality data from millions of measurements that were available, Nolet said.

When the heat columns appeared in their map, the researchers compared their locations to those of suspected mantle plumes around the globe and found close correlations. They identified 32 plumes, most of which are located beneath known hot spots that had been assumed to result from plumes. A few are entirely new and were not associated with known hot spots. At the same time, some expected plumes, such as one believed to be under Yellowstone National Park, did not show up.

The results are an important step in understanding mantle plumes and also raise a host of new questions, said Princeton geophysicist Jason Morgan, who first proposed the existence of mantle plumes in 1971 and, in December, won the National Medal of Science in part for his work on the subject.

The results, for example, do not show all the plumes extending from the bottom of the mantle as he and others anticipated, Morgan said. Some seem to begin in shallower parts of the mantle, he said, noting that understanding the reason for this is likely to provide valuable insights into the dynamics within the Earth. "Some plumes may be gaining strength and others may be fading. I don’t know what will come of that but it will be something interesting I am sure," he said.

Montelli said she plans to continue refining the imaging technique and will repeat the analysis with a different type of seismic wave, which should yield an even sharper image of the plumes.


The research was funded by grants from the National Science Foundation

Steven Schultz | EurekAlert!
Further information:
http://www.princeton.edu/

More articles from Earth Sciences:

nachricht NASA examines Peru's deadly rainfall
24.03.2017 | NASA/Goddard Space Flight Center

nachricht Steep rise of the Bernese Alps
24.03.2017 | Universität Bern

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>