Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Purdue scientist adds third dimension to earth beneath our feet

15.10.2002


The swirl of malleable rock in the earth’s mantle – located between the earth’s crust and core – may have greater effect on the earth’s surface than was once believed, a Purdue research team reports.


Under the boundary between two crustal plates, zones in the mantle with different temperatures swirl together like storm fronts in the atmosphere. Over the millennia, these subterranean warm and cold fronts produce storms in the mantle that can move mountains up on the crust. (Image provided by Scott D. King)


Seen from below, a cold region (colored blue) is sandwiched between two warmer regions (yellow). Over millions of years, these subterranean "storms" can affect the motion of the crust and alter geographical features on the surface, as evidenced by the dramatic angle in the Hawaii-Emperor seamount chain. (Image provided by Scott D. King)



Using computer technology to create three-dimensional models of the earth’s mantle, Purdue’s Scott King has found evidence that some dramatic features of the earth’s surface could be the result of relatively rapid shifts in the direction in which crustal plates move. Rather than simply drifting along in straight lines over millions of years, plates can be pushed aside or even be made to reverse direction due to convection in the mantle far beneath them.

"This is not an idea that has been seriously considered before," said King, professor of earth and atmospheric sciences. "Up until this point, plates were thought to change direction more or less independently from the slow-moving mantle. But with the aid of better computer technology, now we are beginning to realize that they are interconnected. The third dimension is important – we have to consider the earth’s depths if we are ever to understand its surface."


The research, which will appear in the Oct. 15 print issue of Earth and Planetary Science Letters, could spur a rethinking of how major geological features, such as continents and mountain ranges, change shape over time.

Past theories considered crustal plates to be essentially flat objects that either broke into smaller pieces or slid under one another when they collided. The remote depths of the earth’s mantle were thought to have little effect on plate motion because of their own comparatively slow movement.

"The crustal plates themselves move very slowly – only a few inches a year," King said. "But the depths of the mantle were believed to move even more slowly than that. The accepted theory was that all the fast action was taking place near the surface, so the earth’s depths could be safely neglected when considering changes in plate motion."

But King and his colleagues were suspicious of some of the earth’s surface features, such as the Hawaii-Emperor seamount chain. This long string of undersea mountains formed one by one as the crust moved across a hot spot in the mantle, which over millions of years left a string of volcanoes on the Pacific’s floor. The chain of seamounts – some of which pierce the surface to form the Hawaiian Islands – takes a sharp turn from the northwest to the north around Midway Island, then stretches nearly as far as the Aleutians. While scientists had known about the bend in the seamount chain for years, no one had found a testable explanation for its existence.

"If the crust was just drifting along in the same direction, a mountain range would not have grown with such a sharp angle in it," King said. "We started to think that the crust was originally drifting northward, but that some other force must have changed its direction halfway along the line. However, until recently, it was difficult to peer deep enough into the earth to find that force."

A new perspective became possible when King and his colleagues gained access to powerful computer systems at Los Alamos National Laboratory and Purdue. These computers were able to crunch the huge quantities of data necessary to model the earth’s interior in three dimensions.

"The computers are like a window into the mantle," King said. "For the first time, we had tools that could translate a complicated set of equations about the mantle into visual maps the human eye can read."

Much as a CAT scan shows slices of the body, the 3-D maps King’s group produced show different slices of the planet. The cooler and warmer regions of the mantle, which are in constant flux hundreds of miles below our feet, twist around each other like gathering storm clouds. Over the millennia, these subterranean warm and cold fronts produce storms in the mantle that can move mountains up on the crust.

"In a sense, we’re trying to figure out the weather of the earth’s mantle," King said. "The ’storms’ take eons to manifest themselves, but over time they exert powerful force on crustal plates – enough, for example, to make a large part of the Pacific Ocean floor change its direction by about 45 degrees. That’s what we think we are seeing in the Hawaii-Emperor seamount chain."

King is optimistic that the group’s work will shed light on the movement of the earth’s crustal plates, but emphasizes that their theory – like others before it – is not yet the complete picture.

"One of the criticisms that our colleagues have made is that we concentrate on the third dimension, depth, at the expense of surface effects," King said. "Our computer model considers crustal plates as having a constant surface area. But we know that they can grow, crumble and shrink over time. We are working to include these factors in our computer models to improve our knowledge of the ground we walk on even further."

This research was a collaboration between King, Carl W. Gable of Los Alamos National Laboratory, and Julian Lowman of Leeds University. Funding was provided by the National Science Foundation, Los Alamos National Laboratory Institute of Geophysics and Planetary Physics, and Purdue.

Writer: Chad Boutin, (765) 494-2081, cboutin@purdue.edu

Sources: Scott D. King, (765) 494-3696, sking@purdue.edu

Carl W. Gable, (505) 665-3533, gable@lanl.gov

Julian Lowman, (113) 343-5212, j.lowman@earth.leeds.ac.uk

Chad Boutin | Purdue News
Further information:
http://www.seismo.unr.edu/ftp/pub/louie/class/100/interior.html
http://www.eas.purdue.edu/%7Escott/surfing.html
http://www.eas.purdue.edu/%7Escott/mantle/mantle.html

More articles from Earth Sciences:

nachricht New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz

nachricht Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Microscopic trampoline may help create networks of quantum computers

17.07.2018 | Information Technology

In borophene, boundaries are no barrier

17.07.2018 | Materials Sciences

The role of Sodium for the Enhancement of Solar Cells

17.07.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>