Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New ASU research reveals the dynamic inner workings of Earth

08.10.2004


Research at Arizona State University hints to a very active inner Earth area as depicted by these drawings. Image on the left is of Earth. The center image shows a section of Earth and its main divisions (solid inner core, liquid outer core and the lower mantle) including the D" zone. The image on the right is a zoom in of the D" region, which was studied by Edward Garnero and his colleagues. The researchers found strong topographical variations of the D" layer. It was detected as geographical variations in the inferred seismic anisotropy, the alignment of fabric or crystals in rocks.


At the surface of Earth, life on a geologic scale is calm and peaceful save the occasional earthquake caused by the rub and slip of Earth’s tectonic plates. But below Earth’s surface, scientists are beginning to find a far more dynamic and tumultuous region than previously thought.

Deep inside Earth, where the mantle meets the molten iron core, researchers are finding telltale signs of what could be a highly active area filled with exotic forms and substances. "This layer is far more complex than what we thought 10 years ago," said Arizona State University seismologist Edward Garnero. "It is a super dynamic situation, probably the most exotic part of Earth’s interior. This area, where the mantle meets the core halfway to Earth’s center (2,900 km below Earth’s surface), the change in density is several times greater than what we find at Earth’s surface, as represented by air and rock."

Garnero and a team of seismologists (Valerie Maupin, of the University of Oslo, Norway; Thorne Lay of the University of California, Santa Cruz; and Matthew Fouch of ASU) recently completed a study of Earth’s interior. They report their findings in the Oct. 8 issue of Science magazine. In "Variable Azimuthal Anisotropy in Earth’s Lowermost Mantle," the ASU researchers decipher unusual layering in Earth’s deep interior that may contain clues about how the interior churns and convects, and the relationship between Earth’s interior and its ever evolving surface.



The deep mantle region the team probed is a several-hundred-kilometer-thick zone called D" (D double prime), which is where the silicate rock lower mantle meets Earth’s liquid iron outer core. The researchers used seismic waves, those generated by earthquakes, to probe this region. They measured unique directional vibrations of seismic waves recorded in North America from South American earthquakes, permitting a detailed probing of D" beneath Central America and the Caribbean Ocean. Garnero and his colleagues found unexpected wave vibration directions from these waves and showed the deepest mantle to be the source of these wave motion alignment changes.

Tilting of the once horizontal rock fabric in the lower mantle by 20 degrees explains the observation, where the fabric contortions must vary over relatively short distances (hundreds of kilometers). The seismic readings indicate a complex area that churns and chugs as the liquid iron core roils at the bottom of the rock-like mantle, Garnero said. "We were detecting changes in the directional dependency over a relatively small size scale of a few hundred kilometers," Garnero said. "We think there must be currents and turbulence over geologic type time scales that are really quite vigorous and which are occurring at short lengths in order to stir things in such a way as to give this preferred alignment of the material.

Garnero explained that what the seismic waves may be detecting are areas where there are dramatic differences in the types of materials inside Earth. "At the core mantle boundary layer there’s a huge contrast in density," Garnero said. "You go from silicate-based rock (the mantle) to a liquid iron material really rapidly. The environment has all of the markings of something that may be more complex than what we see at the surface."

"What hasn’t been appreciated is that in the deepest mantle there are incredible changes from place to place geographically over short distances," he added. "These changes represent a very dynamic mantle system." "The center of the planet is thought to be as hot as the surface of the Sun, so this is a planet that is going to take some time to cool off," Garnero explained. "It cools off through this stirring and internal mixing."

Garnero said this research is helping reshape the contemporary view of the inner workings of Earth. "In the past 10 to 15 years we have come to appreciate the importance of deciphering the lowest couple of hundred kilometers of the mantle. Doing so is critical in understanding how the interior of Earth actually turns and convects, and drives these motions that we see at the surface," Garnero said. "This research supports a new view of the deepest mantle, where the evolution and dynamics of Earth as a whole cannot be understood without first deciphering the D" layer."

Skip Derra | EurekAlert!
Further information:
http://www.asu.edu

More articles from Earth Sciences:

nachricht A close-up look at an uncommon underwater eruption
11.01.2018 | Woods Hole Oceanographic Institution

nachricht Environmental history told by sludge: Global warming lets the dead zones in the Black Sea grow
10.01.2018 | Leibniz-Institut für Ostseeforschung Warnemünde

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

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...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

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

Novel 3-D printing technique yields high-performance composites

16.01.2018 | Materials Sciences

New application for acoustics helps estimate marine life populations

16.01.2018 | Life Sciences

Fast-tracking T cell therapies with immune-mimicking biomaterials

16.01.2018 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>