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 Turning the Climate Tide by 2020
29.06.2017 | Potsdam-Institut für Klimafolgenforschung

nachricht Predicting eruptions using satellites and math
28.06.2017 | Frontiers

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>