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Posted on 08/30/2009 2:39:28 PM PDT by decimon
CORVALLIS, Ore. – A team of scientists from Oregon State University has created the first global three-dimensional map of electrical conductivity in the Earth's mantle and their model suggests that that enhanced conductivity in certain areas of the mantle may signal the presence of water.
What is most notable, the scientists say, is those areas of high conductivity coincide with subduction zones – where tectonic plates are being subducted beneath the Earth's crust. Subducting plates are comparatively colder than surrounding mantle materials and thus should be less conductive. The answer, the researchers suggest, may be that conductivity in those areas is enhanced by water drawn downward during the subduction process.
Results of their study are being published this week in Nature.
"Many earth scientists have thought that tectonic plates are not likely to carry much if any water deep into the Earth's mantle when they are being subducted," said Adam Schultz, a professor in the College of Oceanic and Atmospheric Sciences at Oregon State and a co-author on the Nature study. "Most evidence suggests that subducting rocks initially hold water within their minerals, but that water is released as the rocks heat up."
"There may be other explanations," he added, "but the model clearly shows a close association between subduction zones and high conductivity and the simplest explanation is water."
The study is important because it provides new insights into the fundamental ways in which the planet works. Despite all of the advances in technology, scientists are still unsure how much water lies beneath the ocean floor – and how much of it makes its way into the mantle.
The implications are myriad. Water interacts with minerals differently at different depths, and small amounts of water can change the physical properties of rocks, alter the viscosity of materials in the mantle, assist in the formation of rising plumes of melted rock and ultimately affect what comes out on the surface.
"In fact, we don't really know how much water there is on Earth," said Gary Egbert, also a professor of oceanography at OSU and co-author on the study. "There is some evidence that there is many times more water below the ocean floor than there is in all the oceans of the world combined. Our results may shed some light on this question."
Egbert cautioned that there are other explanations for higher conductivity in the mantle, including elevated iron content or carbon.
There also may be different explanations for how the water – if indeed the conductivity is reflecting water – got there in the first place, the scientists point out.
"If it isn't being subducted down with the plates," Schultz said, "how did it get there? Is it primordial, down there for four billion years? Or did it indeed come down as the plates slowly subduct, suggesting that the planet may have been much wetter a long time ago? These are fascinating questions, for which we do not yet have answers."
The scientists conducted their study using electromagnetic induction sounding of the Earth's mantle. This electromagnetic imaging method is very sensitive to interconnecting pockets of fluid that may be found within rocks and minerals that enhance conductivity. Using magnetic observations from more than 100 observatories dating back to the 1980s, they were able to create a global three-dimensional map of mantle conductivity.
Anna Kelbert, a post-doctoral research associate at OSU and lead author on the paper, said the imaging doesn't show the water itself, but the level of conductivity and interpreting levels of hydrogen, iron or carbon require additional constraints from mineral physics. She described the study of electrical conductivity as both computationally intensive and requiring years of careful measurements in the international observatories.
"The deeper you want to look into the mantle," Kelbert said, "the longer periods you have to use. This study has required magnetic field recordings collected over decades."
The scientists say the next step is to replicate the experiment with newly available data from both ground observatories and satellites, and then conduct more research to better understand the water cycle and how the interaction with deep-Earth minerals works. Their work is supported by the National Science Foundation and NASA to take the next steps in this research program.
Ultimately, they hope to produce a model quantifying how much water may be in the mantle, locked up within the mineral-bearing rocks.
##
Contact:
Adam Schultz Oregon State University 541-737-9832 adam@coas.oregonstate.edu
I would not be suprised. Most of the worlds major earthquake activity is along subduction zones.
There is some creedence to this.During the 1960s, Rocky Flats nuclear facility began pumping radioactive waste into wells. As soon as they started, earthquakes began. These quakes began on April 24th, 1962, which were triggered by the pumping under high pressure into a 3,670-meter deep disposal well. The first quake was 1.5 on the Richter scale. It was not known that there was a major fault in this area until later. Pumping continued for almost four years as the number of quakes increased and magnitudes reached as high as 5.0. The liquid acted like a lubricant and caused the fault lines to move.
There are other interpretations of the word "firmament".
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not what I was looking for, but nonetheless...
http://www.sciencedaily.com/releases/2007/02/070210171556.htm
http://www.sciencedaily.com/images/2007/02/070210171556.jpg
One of the most dramatic features in the Wysession et. al global mantle shear-wave attenuation model is a very high-attenuation anomaly at the top of the lower mantle beneath eastern Asia. This anomaly is believed due to water that has been pumped into the lower mantle via the long history of the subduction of oceanic lithosphere — crust and upper mantle — in this region. The left figure is a slice through the earth, showing the attenuation anomalies within the mantle. The location of the slice — red line in the upper right figure — is a map of the seismic attenuation at a depth of roughly 620 miles. In both images, red shows unusually soft and weak rock, and blue shows unusually stiff rock (yellow and white show near-average values). The two figures in the lower right are resolution tests to see if the data have the resolution to retrieve Earth structure in these parts of the Earth. The sharper the black-white transitions are, the better the resolution is. (Image Credit: Eric Chou)
Kinda hard to swallow.
I mean, it’s HOT down there - REAL HOT!
And even if subduction zones are cooler, hey, 900 degrees is cooler than 1000 degrees. But still way, way too hot for liquid water!
Scientists Reveal Fate Of Earth’s Oceans
Science News
http://www.sciencedaily.com/releases/2006/05/060511083341.htm
ScienceDaily (May 11, 2006) — Scientists at The University of Manchester have uncovered the first evidence of seawater deep inside the Earth shedding new light on the fate of the planet’s oceans, according to research published in Nature (May 11, 2006).
I thought there was to be war for water in the future. We might, possibly someday, be able to get out of the ground?
The liquid acted like a lubricant and caused enabled the fault lines to move.
Where did it say liquid?
I may be wrong, as I often am.
But it talks about “water”.
Not “steam”.
I think just this one precious time, we can both be wrong.
Me because I missed this part:
“Most evidence suggests that subducting rocks initially hold water within their minerals, but that water is released as the rocks heat up.”
You because you forgot that under pressure the boiling point of water rises...
Above 705 degrees F and 218 atmospheres, wierd things happen to water.
You saved it in the SAHARA FOREST folder!
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Whoops.
Heh... I found it, I think. There’s a folder called “Deep Earth origin?” in the “Water Shortage” folder... six or seven files... but it’s bedtime now that I’ve teased everyone. ;’)
okay, okay, you’ve talked me into it...
Remains of an ancient ocean
26 August 1999
Paul Cooper
http://www.nature.com/nsu/990826/990826-8.html
Leaking Earth could run dry
Water flows into and out of the mantle
Wednesday, September 8, 1999 Published at 23:12 GMT 00:12 UK
http://news.bbc.co.uk/1/hi/sci/tech/442040.stm
Inner Earth May Hold More Water Than the Seas
By Ben Harder
for National Geographic News
March 7, 2002
http://news.nationalgeographic.com/news/2002/03/0307_0307_waterworld.html
Earth could hold more water
Five times as much water as in all the world’s oceans may lurk deep below its surface.
8 March 2002
Philip Ball
http://www.nature.com/nsu/020304/020304-10.html
It's dry as a bone in the LA Basin and all of that water is down there?.....
Why doesn't it reveal itself?
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