Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quakes under Pacific floor reveal unexpected circulatory system

11.01.2008
Study upsets long-held image of volcanism-driven hydrothermal vents

Zigzagging some 60,000 kilometers across ocean floors, earth’s system of mid-ocean ridges plays a pivotal role in many workings of the planet, from its plate-tectonic movements to heat flow from the interior, and the chemistry of rock, water and air.

It was not until the late 1970s that scientists discovered the existence of vast plumbing systems under the ridges, which pull in cold water, superheat it, then spit it back out from seafloor vents—a process that brings up not only hot water, but dissolved substances taken from rocks below. Unique life forms feed off the vents’ stew, and valuable minerals including gold may pile up.

Now, a team of seismologists working under 2,500 meters of water on the East Pacific Rise, some 565 miles southwest of Acapulco, Mexico, has created the first images of one of these systems—and it does not look the way most scientists had assumed. The resulting study appears in the Jan. 10 issue of the journal Nature.

The hypothetical image of a hydrothermal-vent system shows water forced down by overlying pressure through large faults along ridge flanks. The water is heated by shallow volcanism, then rises toward the ridges’ middles, where vents (often called “black smokers,” for the cloud of chemicals they exude) tend to cluster. The new images, from a 4-kilometer-square area show a very different arrangement. The water appears to descend instead through a sort of buried 200-meter-wide chimney atop the ridge, run below the ridge along its axis through a tunnel-like zone just above a magma chamber, and then bubble back up through a series of vents further along the ridge. “If you google on images of hydrothermal vents, you come up with cartoons that don’t at all match what we see,” said lead author Maya Tolstoy, a marine seismologist at Lamont-Doherty Earth Observatory, part of Columbia University’s Earth Institute.

The images were created using seismometers planted around the ridge to record tiny, shallow earthquakes—in this study, 7,000 of them, over 7 months in 2003 and 2004. Using new techniques developed by Lamont seismologist Felix Waldhauser, the quakes were located with great precision. They cluster neatly, outlining the cold water’s apparent entrance. It dives straight down through the ridge about 700 meters, then fans out into a horizontal band about 200 meters wide before bottoming out at about 1.5 kilometers, just above the magma. Heated water rises back up through a dozen vents about 2 kilometers north along the ridge. The researchers interpret the quakes as the result of cold water passing through hot rocks and picking up their heat—a process that shrinks the rocks, and cracks them, creating the small quakes.

The downflow zone is thought to have been formed initially by a kink in the ridge, which stresses the rock enough to crack it mechanically. Seawater, forced down into the resulting space, eventually gets heated by the magma, then rises back to the seafloor—much the same process seen in a pot of boiling water. Tolstoy and her coauthors believe the water travels not through large faults—the model previously favored by some scientists--but through systems of tiny cracks. Furthermore, their calculations suggest that the water moves a lot faster than previously thought—perhaps a billion gallons per year through this particular system. Their chart of the water’s route is reinforced by biologists’ observations from submersible dives that the area around the downflow chimney is more or less lifeless, while the surging vents are a riot of bacterial mats, mussels, tubeworms, and other weird creatures that thrive off the heat and chemicals.

“It’s an exciting and substantial contribution. It begins to look at some really big questions,” said Dan Fornari, a marine geologist at Woods Hole Oceanographic Institution who was not involved in the study. Among other things, it is a mystery where vent organisms came from--some evolutionary biologists believe they originated life on earth—and how or whether they now make their way from one isolated vent system to another. The findings could add to an understanding of seafloor currents along which they may move, and of the nutrient flows that feed them. The work also has large-scale implications for how heat and chemicals are cycled to the seafloor and overlying waters, said Tolstoy. On a practical level, many large ore bodies now on land are thought to have been formed by such systems.

The work is part of a larger long-term interdisciplinary look at the East Pacific Rise, funded by the U.S. National Science Foundation. Scientists from Lamont and other institutions are still retrieving and analyzing data from earlier cruises. In 2006, a volcanic eruption buried some of their instruments; most of the instruments were lost, but those that survived provided new information about how the eruptions work. This summer, researchers hope to return aboard the new Lamont-operated vessel Marcus G. Langseth to generate unprecedented 3D images of the ridge’s interior.

Kevin Krajick | EurekAlert!
Further information:
http://www.earth.columbia.edu

More articles from Earth Sciences:

nachricht Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>