Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Images Reveal Different Magma Pools Form the Ocean’s Crust

29.08.2005


For the first time, scientists have produced images of the oceanic crust and found that the upper and lower layers of the crust are likely formed from different magma pools. The images begin to answer some lingering questions about where new ocean crust comes from and whether it is all formed the same way.



Geophysicists Robert Detrick and Juan-Pablo Canales of Woods Hole Oceanographic Institution (WHOI) and colleagues used reflected seismic, or sound, waves to successfully image the structure of the lower crust across the flanks of the Juan de Fuca Ridge, a spreading plate boundary off the Pacific Northwest coast. Their study, co-authored by researchers at Columbia University’s Lamont-Doherty Earth Observatory and Scripps Institution of Oceanography, appears in the August 25, 2005 issue of Nature.

By recording the reflection of seismic waves off the lower crust at the crust-mantle boundary, a technique common in oil exploration, the researchers found evidence strongly suggesting that the base of the crust forms much differently than its overlying layers.


“Seismic reflection is a powerful tool to image the sub-surface detailed structure of the Earth down to several kilometers or miles below the surface," study co-author Canales said. “Scientists studying the formation of the ocean crust have been debating over the past decade whether all of the crust is formed from magma that accumulates in a single pool or lens a mile or two deep, or if it forms from multiple magma sills at different levels.”

Detrick, Canales and colleagues analyzed about 1,500 kilometers (935 miles) of data collected on the Juan de Fuca Ridge off the coast of Washington, Oregon and northern California. The images are the first of their kind showing solidified magma lenses and sills, narrow lateral intrusions of magma, embedded in the boundary between the mantle and the overlying crust, a region known as the Moho transition zone. The existence of these magma lenses near a mid-ocean ridge suggests that the lower oceanic crust is formed from several smaller sources of magma rather than a single large pool located in the middle of the crust.

Unlike continental crust, which is very old and thick, oceanic crust averages 6-7 kilometers (3-4 miles) thick and is constantly being recycled at tectonic plate boundaries on the seafloor. Crust is destroyed at subduction zones, where plates come together, and created at mid-ocean ridges, where plates are pulling apart, like the Juan de Fuca Ridge. At these ridges, also known as seafloor spreading centers, molten rock, or magma, rises from deep within the earth and solidifies to become new crust. But the exact source of that magma—particularly the magma that forms the lower layers of the crust—was not well understood until now.

Previously, geophysicists knew that the topmost layer of the crust cooled from molten rock supplied by a single pool, or lens, of magma located in the crust’s middle layers. What was not known was whether the lower crust, which lies just above the mantle, solidified from the same melt lens or from many smaller magma bodies in the deeper crust-mantle transition zone. The new study found evidence of multiple pockets of molten rock now frozen, lending strong support to the latter theory.

Geophysical studies along mid-ocean ridges to date using seismic reflection have been able to image only one single crustal melt lens, supporting the first model of crustal formation. However, other remote-sensing geophysical methods that are used to infer the mechanical properties of the crust indicate that magma must also accumulate at deeper levels, in particular at the base of the crust or the Moho transition zone.

The multiple-lens model comes from field observations at ophiolites where the remnants of the multiple melt sills can be mapped. Ophiolites are slabs of oceanic crust long ago thrust up onto dry land and are easily accessible to geologists seeking clues to what new crust might look like.

“It is exciting that different observational approaches, marine seismology and ophiolite studies, that look at the same problem at different spatial and resolution scales are converging towards a unified geological and geophysical model of how the ocean crust is formed," Canales said.

The study was funded by the National Science Foundation.

Shelley Dawicki | EurekAlert!
Further information:
http://www.whoi.edu

More articles from Earth Sciences:

nachricht Clear as mud: Desiccation cracks help reveal the shape of water on Mars
20.04.2018 | Geological Society of America

nachricht Hurricane Harvey: Dutch-Texan research shows most fatalities occurred outside flood zones
19.04.2018 | European Geosciences Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>