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 Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

nachricht Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>