Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

’Anti-plume’ found off Pacific Coast

15.07.2004


The gradual subduction of the Juan de Fuca plate beneath the North American plate puts tremendous stress on the seafloor, creating cracks and fissures, hydrothermal vents, seafloor spreading, and literally hundreds of small earthquakes on a near-daily basis.
Now a North American team of scientists has documented for the first time a new phenomenon – the creation of a void in the seafloor that draws in – rather than expels – surrounding seawater. They report their discovery in the July 15 issue of the journal Nature.

Oregon State University oceanographer Robert Dziak said the discovery is important because it adds a new wrinkle to scientific understanding of seafloor spreading, the fundamental process of plate tectonics and the creation of ocean crust. Dziak has a dual appointment with the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory.


"Just when you think you’re beginning to understand how the process works, there’s a new twist," Dziak said. "There was an episode of seafloor spreading on a portion of the Juan de Fuca Ridge that was covered with about a hundred meters of sediment and what usually happens in that case is that lava erupts onto the ocean floor and hot fluid is expelled into the water. "In this case, though, it actually drew water down into the subsurface, which is something scientists have never before observed," he said.

The research team included Earl Davis, of the Geological Survey of Canada’s Pacific Geoscience Centre; Keir Becker, from the Rosenstiel School of Marine and Atmospheric Science at the University of Florida; Dziak; and John Cassidy, Kelin Wang and Marvin Lilley of the University of Washington.

Dziak said the researchers think the seafloor spreading caused the ocean crust to dilate, increasing the pore space much like a sponge. "It’s like an anti-plume," he said. "Instead of sending materials from within the Earth to the ocean floor, it simply sucks down the surrounding seawater."

The researchers aren’t sure exactly what causes the dilation, but it has multiple implications. First, it changes how scientists view seafloor spreading since there isn’t an automatic outpouring of lava, or hot liquid via hydrothermal vents previously associated with tectonic plate theory.

The size of these potential "voids" also intrigues scientists, who wonder how much seawater can be subsumed. If large, or frequent, they could affect surrounding water temperatures and chemical composition, Dziak said.

Finally, water migrating downward through the Earth may be enough to trigger the growth of bacteria at startling depths. Last year, in an unrelated study, OSU oceanographer Martin Fisk and a team of researchers found bacteria in a hole drilled 4,000 feet through volcanic rock. Basalt rocks have all of the elements required for life, Fisk pointed out, including carbon, phosphorous and nitrogen. Only water is needed to complete the formula.

Dziak is able to monitor offshore activities from his laboratory at OSU’s Hatfield Marine Science Center in Newport, where he uses an array of undersea hydrophones through a unique arrangement with the U.S. Navy. During the past dozen years, Dziak and his research team have recorded more than 30,000 earthquakes in the Pacific Ocean off the Northwest coast – few of which have ever shown up on land-based seismic equipment.

The earthquakes, most having a magnitude of 2.0 to 4.0, originate along the Juan de Fuca Ridge, a submarine mountain range 300 miles west of the Oregon coast that was formed by seafloor spreading or the movement of oceanic plates away from one another.

"It is the only real-time hydrophone system in the world available for civilian research," Dziak said. "It allows us to listen to the earthquakes as they occur and when something unusual happens, we can send out a group of scientists to study the events as they unfold."

The hydrophone system – called the Sound Surveillance System, or SOSUS – was used during the decades of the Cold War to monitor submarine activity in the northern Pacific Ocean. As the Cold War ebbed, these and other unique military assets were offered to civilian researchers performing environmental studies, Dziak said. SOSUS also pointed the researchers to the activities leading to the "anti-plume" discovery outlined in Nature.

The number of earthquakes offshore initially stunned researchers because they weren’t being detected on land – even by the most sensitive seismometers. The scientists also discovered that these quakes occurred daily, but every so often there would be a "swarm" of as many as a thousand quakes in a three-week period.

"In the last 10 years, I’ve seen seven of these swarms," Dziak said. "The plate doesn’t move in a continuous manner and some parts move faster than others. Every four years or so, a section of the Juan de Fuca Ridge exhibits a large earthquake swarm and lava breaks through onto the seafloor.

"Usually, the plate moves at about the rate a fingernail might grow – say three centimeters a year. But when these swarms take place, the movement may be more like a meter in a two-week period."

On Monday, July 12, the region was jolted by a 4.9 magnitude quake just offshore from Dziak’s Newport lab – one that was felt more than 50 miles inland at the main OSU campus.

"There’s a lot of activity going on out there," Dziak said of the offshore quakes. "That was one of the few that did show up on conventional seismic equipment and drew the attention of the public. There are hundreds, even thousands more that do not."

Robert Dziak | EurekAlert!
Further information:
http://www.oregonstate.edu

More articles from Earth Sciences:

nachricht First research results on the "spectacular meteorite fall" of Flensburg
18.02.2020 | Westfälische Wilhelms-Universität Münster

nachricht The Antarctica Factor: model uncertainties reveal upcoming sea-level risk
14.02.2020 | Potsdam-Institut für Klimafolgenforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

Im Focus: Skyrmions like it hot: Spin structures are controllable even at high temperatures

Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices

The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...

Im Focus: Making the internet more energy efficient through systemic optimization

Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.

Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.

Im Focus: New synthesis methods enhance 3D chemical space for drug discovery

After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.

"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.

Im Focus: Quantum fluctuations sustain the record superconductor

Superconductivity approaching room temperature may be possible in hydrogen-rich compounds at much lower pressures than previously expected

Reaching room-temperature superconductivity is one of the biggest dreams in physics. Its discovery would bring a technological revolution by providing...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

Movement of a liquid droplet generates over 5 volts of electricity

18.02.2020 | Power and Electrical Engineering

Powering the future: Smallest all-digital circuit opens doors to 5 nm next-gen semiconductor

18.02.2020 | Information Technology

Studying electrons, bridging two realms of physics: connecting solids and soft matter

18.02.2020 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>