. Earth Science News .
3D Seismic Model Of Vast Water Reservoir Revealed

Seventy percent of the earth is covered by water, which is very important for the earth's geology, serving as a lubricant that allows efficient convection and plate tectonics and the continental collisions that form mountains. "Water is like a lubricant, constantly oiling the machine of mantle convection which then drives plate tectonics and causes the continents to move about Earth's surface," Michael E. Wysession said. "Look at our sister planet, Venus. It is very hot and dry inside Venus, and Venus has no plate tectonics. All the water probably boiled off, and without water, there are no plates. The system is locked up, like a rusty Tin Man with no oil."
by Tony Fitzpatrick
St. Louis MO (SPX) Feb 13, 2007
Seismologists at Washington University in St. Louis have made the first 3-D model of seismic wave damping - diminishing - deep in the Earth's mantle and has revealed the existence of an underground water reservoir at least the volume of the Arctic Ocean. It is the first evidence for water existing in the Earth's deep mantle.

Michael E. Wysession, Ph.D., Washington University professor of earth and planetary sciences in Arts and Sciences, working with former graduate student Jesse Lawrence (now at the University of California, San Diego), analyzed 80,000 shear waves from more than 600,000 seismograms and found a large area in Earth's lower mantle beneath eastern Asia where water is damping out, or attenuating, seismic waves from earthquakes.

The traditional method seismologists use to image the Earth below us is to measure the speed of seismic waves. This will provide a sort of CAT scan of the Earth's core and mantle. Using wave speeds alone is a problem, however, because they cannot distinguish between temperature and composition variations.

The research is described in a forthcoming monograph, Earth's Deep Water Cycle, which is in press to be published by the American Geophysical Union.

Analyzing damped-out waves

An increasingly popular method, which Wysession used, is to analyze the way waves damp out from their source. If you take a hammer and pound it hard on a desk, waves will go from the source to the end of the table with the mass of the table lessening, or attenuating, the power of waves. A picture near the striking point might topple, but a stapler two feet away might not even budge. Attenuation data tell seismologists how stiff a region is, which is a function of how hot it is and how much water it contains. Looking at the seismic wave speeds and attenuation at the same time can tell whether an anomaly is due to temperature or water.

In analyzing the data, Wysession first saw large patterns associated with known areas where the ocean floor is sinking down into the earth. Beneath Asia, the fallen Pacific sea floor piles up at the base of the mantle. Right above that he observed an "incredibly highly attenuating region, that is both very damping and slightly slow," he said. "Water slows the speed of waves a little. Lots of damping and a little slowing match the predictions for water very well."

Previous predictions calculated that a cold ocean slab sinking into the earth at 1,200 to 1,4000 kilometers beneath the surface would release water in the rock that would escape the rock and rise up to a region above it, but this was never previously observed.

Beijing anomaly

"That is exactly what we show here, the exact depth and high attenuation amounts right above it," Wysession said. "I call it the Beijing anomaly. Water inside the rock goes down with the sinking slab and it's quite cold, but it heats up the deeper it goes, and the rock eventually becomes unstable and loses its water. The water then rises up into the overlying region, which becomes saturated with water.

"If you combine the volume of this anomaly with the fact that the rock can hold up to about 0.1 percent of water, that works out to be about an Arctic Ocean's worth of water."

In recent years, seismologists have become excited at the possibility of a feature like the Beijing anomaly. The availability of vast amounts of digital seismograms made possible the discovery by Wysession and Lawrence, who wrote many thousands of lines of computer codes to do the analyses.

Seventy percent of the earth is covered by water, which is very important for the earth's geology, serving as a lubricant that allows efficient convection and plate tectonics and the continental collisions that form mountains.

"Water is like a lubricant, constantly oiling the machine of mantle convection which then drives plate tectonics and causes the continents to move about Earth's surface," Wysession said. "Look at our sister planet, Venus. It is very hot and dry inside Venus, and Venus has no plate tectonics. All the water probably boiled off, and without water, there are no plates. The system is locked up, like a rusty Tin Man with no oil."

Email This Article

Related Links
Washington University
Water, Water Everywhere and Not A Drop To Drink...

NASA Study Finds Warmer Future Could Bring Droughts
New York NY (SPX) Feb 13, 2007
NASA scientists may have discovered how a warmer climate in the future could increase droughts in certain parts of the world, including the southwest United States. The researchers compared historical records of the climate impact of changes in the sun's output with model projections of how a warmer climate driven by greenhouse gases would change rainfall patterns. They found that a warmer future climate likely will produce droughts in the same areas as those observed in ancient times, but potentially with greater severity.







  • Health Problems Hit Indonesia Flood Victims
  • Japan Launches Alert System For Tsunamis And Missiles
  • Catastrophe Bonds A Market Answer To Hail Or High Water
  • Call To Move Indonesian Capital After Deadly Floods

  • Global Warming Debate Heats Up In Washington
  • Study Shows Largest North America Climate Change In 65 Million Years
  • White House Issues Rare Letter Defending Record On Warming
  • From Greenhouse To Icehouse: New Clues On Ancient Climate Shift

  • Gascom To Launch 4 Smotr Low-Orbit Remote Sensing Satellites
  • GeoEye Makes Final Debt Payment For The Purchase Of Space Imaging
  • Google Earth To Blur Key India Sites
  • Brazilian Satellite Undergoes Environmental Tests

  • Cold Storage Solution For Global Warming
  • Energy Giant Total To Test Scheme To Store Carbon Emissions
  • Chinese firms win 1.46 bln dollar hydro project in Nigeria
  • Storing Carbon Dioxide Below Ground May Prevent Polluting Above

  • Large-Scale Trial Of HIV Vaccine Launched In South Africa
  • AIDS Vaccine Closer But Remains Elusive
  • Global Vaccine Market To Top 23 Billion Dollars
  • US Overdue For Bird Flu Experts Warn

  • Researchers Unearth 4300-Year-Old Chimpanzee Technology
  • Adaptation To Global Climate Change Is An Essential Response To A Warming Planet
  • Electric Fish Shed Light On Ways The Brain Directs Movement
  • Investigating The Invisible Life In Our Environment

  • Britain Launches Investigation Into Monsanto Toxic Waste
  • Pollution Worsens As Curbs Fail In China
  • Facing Jail US Mining Boss Says Pollution Trial A Sham
  • EU To Propose Laws To Fight 'Green Crimes'

  • Human Ecological Footprint In 2015 And Amazonia Revealed
  • Risk Of Extinction Accelerated Due To Interacting Human Threats
  • Carnegie Mellon Student Develops Mood-Sharing Gadget To Help Computer Users Express Their Feelings
  • Selectivity Is Ultimate Aphrodisiac

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement