Water in Mantle May be Associated with Subduction (More water below oceans than in?)

Oregon State University ^ | August 19, 2009 | Unknown

[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

[ErnstStavroBlofeld]

Thanks for the minor correction

:)

[ErnstStavroBlofeld]

The faults of the LA Basin are different than the subductions zones. The subduction zone which one tectonic plate moves under another tectonic plate, sinking into the Earth’s mantle as the plates converge.The ones in the LA Basin is called a stike slip and thrust faults. A strike slip fault is a fracture formed where two parts of the earth’s crust (plates) slide past each other. The ones underneath Los Angeles is a blind thrust fault.If the fault plane terminates before it reaches the Earth’s surface, it is referred to as a blind thrust fault. Because of the lack of surface evidence, blind thrust faults are difficult to detect until they rupture.

[ErnstStavroBlofeld]

Those two types faults are the most common in North America.

[ErnstStavroBlofeld]

There is one thrust fault running from Dodger Stadium underneath Downtown Los Angeles straight down to Long Beach that is capable of producing a 7 plus earthquake. It called the Puente Hills Fault. It was discovered after the 1994 earthquake.

[Ernest_at_the_Beach]

Ugh!

San Diego SuperComputer visualization Services....Puente Hills

***********************EXCERPT*******************

Puente Hills Fault posses a disaster threat for Los Angeles region. Earthquake simulations on this fault estimate damages over $250 billion. The research was conducted by U.S. Geological Survey (USGS) and Southern California Earthquake Center (SCEC). More information about the study could be found at the SCEC research webpage .

Visualizations created by using the data computed from earthquake simulations helps one to fathom the propagation of siesmic waves and the areas affected. Animations were created using SDSC's Vista volume renderer, Alias's Maya and Adobe's After Effects.

[raygun]

How hot does water have to be at the bottom of the Marianas Trench to become steam?

I’d suggest it IS liquid.

[raygun]

That's what they said about the petroleum that's being perpetually renewed beneath ground too.

Except for one thing, the only thing they can find in fumeroles is steam and CO₂ Which, according to proponents is good, because the pressure and associated heat breaks complex hydrocarbons down to what?

O.K., but now there's a whole new fly being rubbed into this oinkment.

Frankly, I see two scientific theories in collision.

[ErnstStavroBlofeld]

If the Puente Hills decides to move it would be more destructive than a movement on the San Andreas. The reason why because the fault will rupture underneath Downtown Los Angeles. Those buildings were not designed for that type of earthquake. I pass the rupture point of the 1994 earthquake twice a week and you can see the the rupture point 15 years afterward

[raygun]

Ya think? What ‘bout all the sludge falling down from on high in the oceans mixed in with all the subducted water.

What’s that stuff that’s in the oil shale, that needs that really difficult refining process, carotene or something.

I don’t know. Its interesting. That’s how science works.

I heard tell that science without religion is misguided and religion without science is blind. I think that everybody needs to stake a claim to that thinking; atheists don’t believe in the coin, agnostics are the edge of the coin, and then there are the two opposing faces to a coin.

[djf]

Well, maybe I’m reading it wrong. But the whole concept here seems to be that as the crust subducts and plunges down, it carries with it liquid water itself as well as large amounts of water trapped in crystalline lattices (limestone/concrete type materials).

So I didn’t think they were talking about gaseous water.

That’s all.

[AndrewC]

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).

Wow, I have to chew on this for a while....

Professor Ballentine added: "Our results also explain why ocean volcanoes, like Hawaii and Iceland, which come from the where the mantle meets the core, have a higher water content than ocean volcanoes that originate from shallower regions of the mantle. Previously, geologists have thought that this is because this region of the planet preferentially preserved water and gasses trapped during earth formation and it is only now 'leaking out'. We know however that if seawater subduction is occurring, it will be carried more efficiently into the deepest parts of the earth, and that contrary to these old ideas, the water in the lavas from Hawaii and Iceland are in fact dominated by old seawater that has travelled from the surface, to the center of the earth and back again."

[ApplegateRanch]

Why doesn't it reveal itself?

Drill, baby; DRILL! Drill there; drill now!

[ErnstStavroBlofeld]

Maybe a new Project Mohole. If anyone knows what that project was it was an attempt to drill through the Earth's crust to the boundary between the crust and the mantle. The drilling was to begin at the ocean bottom because this is where the crust is at its thinnest.They never completed it because it ran into cost over runs. The deepest they got was something around 600 feet below the ocean's floor in 11,000 feet of water.

[null and void]

Yep. I caught my error and corrected it in a later post.

But now that you mention it,

~10 km water -> ~1000 atm -> 945°C boiling point.

That’s for pure water, adding salts and minerals increases the boiling point.

The pressure under a mile or so of rock would be MUCH higher...

[null and void]

Frankly, I see two scientific theories in collision.

Yeah! It's a beautiful thing!

[Squidpup]

http://www.creationscience.com/onlinebook/HydroplateOverview2.html

[fishtank]

http://www.google.com/#hl=en&source=hp&q=%22john+Baumgardner%22+subduction&aq=f&aqi=&oq=&fp=4bb1eec54ca89dc

[colorado tanker]

Of course there’s water in the earth. Otherwise there couldn’t be a lost world in the center.

[ApplegateRanch]

Successor program:

Scientists Aboard Drilling Vessel Recover Rocks from Earth’s Crust Far Below Seafloor

April 5, 2005

Scientists affiliated with the Integrated Ocean Drilling Program (IODP) and seeking the elusive “Moho”—the boundary, which geologists refer to as the Mohorovicic discontinuity, between Earth's brittle outer crust and its hotter, softer mantle—have created the third deepest hole ever drilled into the ocean bottom’s crust.

[snip]

From the ocean drilling vessel, JOIDES Resolution, the researchers recovered rocks from more than 4,644 feet (1416 meters) below the sea floor that will provide valuable information about the composition of the Earth. And despite coming up short, “This is one of the best efforts to date,” said Rodey Batiza, NSF program director for ocean drilling, “to drill into ocean crust and find mantle. It will provide important clues on how ocean crust forms.”
[end excerpt]

Earth's elusive mantle is a near miss They may be using the wrong approach...there are better ways:

[ErnstStavroBlofeld]

Thanks for the information. I am bookmarking this.

:)