Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Oceanic Crust Formation Is Dynamic After All

27.11.2009
Earth scientists at Brown University have found strong evidence that the geological processes that lead to the formation of oceanic crust are not as uniformly passive as believed. The team found centers of dynamic upwelling in the shallow mantle beneath spreading centers on the seafloor. Findings are published in this week’s Nature.

Imagine the Earth’s crust as the planet’s skin: Some areas are old and wrinkled while others have a fresher, more youthful sheen, as if they had been regularly lathered with lotion.

Carry the metaphor a little further and a good picture emerges of the geological processes leading to the creation of the planet’s crust. On land, continental crust, once created, can remain more or less unaltered for billions of years. But the oldest oceanic crust is only about 200 million years old, as new crust is continually forming at midocean ridge spreading centers.

While geologists have known that oceanic crust continually replenishes itself, they have been unsure what occurs below the surface that leads to the resurfacing. What geodynamics are occurring in the mantle that eventually produces new crust, that new layer of skin on the ocean’s bottom?

The answer has been elusive in part because oceanic crust is difficult to reach and instruments that can measure seismic activity have not fully covered the terrain to obtain an accurate picture of forces below the surface. Now earth scientists led by Brown University have observed — in detail and at unprecedented depths — a geological phenomenon known as dynamic upwelling in the underlying mantle beneath a spreading center. Their findings, reported in this week’s Nature, may resolve a longstanding debate regarding the relative importance of passive and dynamic upwelling in the shallow mantle beneath spreading centers on the seafloor.

“We know the crust of the ocean is produced by upwelling beneath separating plates,” said Don Forsyth, professor of geological sciences at Brown. “We just didn’t know the upwelling pattern that took place, that there are concentrated upwelling centers rather than uniform upwelling.”

Mantle upwelling and melting beneath spreading centers has been thought to be mostly a passive response to the separating oceanic plates above. The new finding shows there appears to be a dynamic component as well, driven by the buoyancy of melt retained in the rock or by the lighter chemical composition of rock from which melt has been removed.

The scientists from Brown and the University of Rhode Island based their findings on a high-resolution seismic study in the Gulf of California. In that region, there are 25 seismometers spaced along the western coast of Mexico and the Baja California peninsula, which lie on either side of the Gulf of California. Yun Wang, a Brown graduate student and the paper’s lead author, tracked the velocity of seismic waves that traveled from one station to another. She noticed a pattern: The seismic waves in three localized centers, spaced about 250 kilometers (155 miles) apart, traveled more slowly than waves in the surrounding mantle, implying the presence of more melt in the localized centers and thus a more vigorous upwelling. From that, the geologists determined the centers, located 40-90 kilometers (25 to 56 miles) below the surface, showed evidence of dynamic upwelling in the mantle.

“We found a pattern that was predicted by some of the theoretical models of upwelling in midoceanic ridges,” Forsyth said.

While other studies have been done of mantle geodynamics, most notably an experiment on the East Pacific Rise, the Brown-URI study imaged seismic activity, or the shear velocity of the seismic waves, some 200 kilometers (124 miles) below the surface — a far deeper seismic penetration into the mantle than previous experiments.

Brian Savage, assistant professor of geophysics at the University of Rhode Island and a contributing author on the paper, said the finding is important, because it helps to provide “a basic understanding of how a majority of the earth’s crust is formed, how it emerges from the mantle below to create the oceanic crust. It's a basic science question that helps understand how crust is created.”

The research was funded by the National Science Foundation.

Richard Lewis | EurekAlert!
Further information:
http://www.Brown.edu

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>