WASHINGTON UNIVERSITY IN ST. LOUIS
25 NOV 2018
Slow-motion collisions of tectonic plates under the ocean drag about three times more water down into the deep Earth than previously believed, according to a seismic study that spans the Mariana Trench.
The observations from the deepest ocean trench in the world have important implications for the global water cycle, researchers say.
“People knew that subduction zones could bring down water, but they didn’t know how much water,” says Chen Cai, who recently completed his doctoral studies at Washington University in St. Louis and is first author of the paper, which appears in Nature.
“This research shows that subduction zones move far more water into Earth’s deep interior—many miles below the surface—than previously thought,” says Candace Major, a program director in the National Science Foundation’s Division of Ocean Sciences, which funded the study.
“The results highlight the important role of subduction zones in Earth’s water cycle.”
“Previous estimates vary widely in the amount of water that is subducted deeper than 60 miles,” says Douglas A. Wiens, professor of earth and planetary sciences and Cai’s research adviser for the study.
“The main source of uncertainty in these calculations was the initial water content of the subducting uppermost mantle.”
Under the sea
To conduct the study, researchers listened to more than one year’s worth of Earth’s rumblings—from ambient noise to actual earthquakes—using a network of 19 passive, ocean-bottom seismographs deployed across the Mariana Trench, along with seven island-based seismographs.
The trench is where the western Pacific Ocean plate slides beneath the Mariana plate and sinks deep into the Earth’s mantle as the plates slowly converge.
The new seismic observations paint a more nuanced picture of the Pacific plate bending into the trench—resolving its three-dimensional structure and tracking the relative speeds of types of rock that have different capabilities for holding water.
Rock can grab and hold onto water in a variety of ways. Ocean water atop the plate runs down into the Earth’s crust and upper mantle along the fault lines that lace the area where plates collide and bend. Then it gets trapped.
Under certain temperature and pressure conditions, chemical reactions force the water into a non-liquid form as hydrous minerals—wet rocks—locking the water into the rock in the geologic plate.
All the while, the plate continues to crawl ever deeper into the Earth’s mantle, bringing the water along with it.
Previous studies at subduction zones like the Mariana Trench have noted that the subducting plate could hold water. But they could not determine how much water it held and how deep it went.
“Previous conventions were based on active source studies, which can only show the top 3-4 miles into the incoming plate,” Cai says, referring to a type of seismic study that uses sound waves created with the blast of an air gun from aboard an ocean research vessel to create an image of the subsurface rock structure.
“They could not be very precise about how thick it is, or how hydrated it is,” he says.
“Our study tried to constrain that. If water can penetrate deeper into the plate, it can stay there and be brought down to deeper depths.”
The seismic images show that the area of hydrated rock at the Mariana Trench extends almost 20 miles beneath the seafloor—much deeper than previously thought. The amount of water that can be held in this block of hydrated rock is considerable.
What goes down must come up
For the Mariana Trench region alone, four times more water subducts than previously calculated. Researchers can also extrapolate these features to predict the conditions under other ocean trenches worldwide.
“If other old, cold subducting slabs contain similarly thick layers of hydrous mantle, then estimates of the global water flux into the mantle at depths greater than 60 miles must be increased by a factor of about three,” Wiens says.
And for water in the Earth, what goes down must come up. Sea levels have remained relatively stable over geologic time, varying by less than 1,000 feet.
This means that all of the water that is going down into the Earth at subduction zones must be coming back up somehow, and not continuously piling up inside the Earth.
Scientists believe that most of the water that goes down at the trench comes back from the Earth into the atmosphere as water vapor when volcanoes erupt hundreds of miles away.
But with the revised estimates of water from the new study, the amount of water going into the earth seems to greatly exceed the amount of water coming out.
“The estimates of water coming back out through the volcanic arc are probably very uncertain,” says Wiens, who hopes that this study will encourage other researchers to reconsider their models for how water moves back out of the Earth.
The research has been published in Nature.
Source: Washington University in St. Louis, Stony Brook University
HT/ozspeaksup
Since 70% of the Earth’s surface is oceanic crust whose maximum age has been dated at around 180 m.y., the question is: what happened to the oceanic crust that existed for the remaining 96% of geologic time? Has the purported subduction process been so complete as to expunge every last skerrick of evidence that such a crust ever existed?
It no longer exists on the floor of the ocean. Most of it has been subducted. At the margins of these subduction zones, you can go and see for yourself areas where that ancient oceanic crust has been scraped up by the continent into deposits called a mélange. This ancient ocean floor is visible today and consists largely of a mineral type called serpentinite – which consists of ocean floor basalts that have been altered through hydrolization (forcing sea water into the mineral’s matrix). This produces a set of new minerals and a very distinct and unmistakable texture and appearance to the rock.
“expunge every last skerrick of evidence that such a crust ever existed?” No.
There are many areas on earth where remnants of oceanic crust are preserved and these are primarily along the margins of continents. The suites of rocks formerly existing as oceanic crust are called ophiolite. Ophiolite marks the location of ancient subduction and asscoiated tectonic processes.
http://volcano.oregonstate.edu/ophiolites excellent diagrams and descriptions
The understanding of the origin and significance of ophiolites was one of the pillars of the “revolution in the earth sciences” during the 1960s and 1970s.
According to Wikipedia, ophiolites are common in orogenic belts of Mesozoic age (e.g. Oman) but are quite rare in domains of Archean to Paleo-proterozoic vintage.
Subducted slabs are routinely detected and observed in the mantle, like the Farralon Plate.
Since the ice sheets melted, continental plates once weighed down are still in the process of ‘bobbing up’. Why wouldn’t all the added water weight over the much-thinner oceanic plates push them down, thus reducing friction along subduction faults?
This process could also be opening cracks that allow water to drain into the abodes of the mole people. Perhaps the missing water is pouring through their tunnels and bubbling up at the North Pole, raising temperatures in the Arctic.
Mole People? Of course. That explains everything.
https://youtu.be/kuvAKxlfN3U
Population: 6.023 x 10^23
mol … lol
It took a while looking at the original study to find what I wanted … the global amount of water going into the mantle.
Three billion teragrams per million years, that works out to about 3E+9 cubic metres, or about 3 cubic kilometres of water. More than an Olympic swimming pool, to be sure.
However, given that the oceans contain about 1,370,000,000 cubic km of water, I think the technical term for 3 cubic km is … well … “not much”. It would make a difference of 0.008 mm/year in the sea level …
Check my figures, I’ve been known to lose a decimal point in the shuffle, but I think those numbers are right.
w.
Still, if the figures are correct it would imply that the oceans are recycled about every 450 million years. Doesn’t seem too unreasonable. And 3 cubic kilometers of water per year coming out of volcanoes and as water of hydration in minerals intruded in oceanic ridges doesn’t sound unreasonable either.
Maybe that sucked Trenberth’s missing heat as well?
H20 is the mother of all greenhouse gases, and now its in the mantle too? Oh, the humanity!
Yup, that one’s on us too. Anthropogenic magma is on the way up yer dike.
Obviously, Poseidon is colluding with deniers to reduce the rate of sea level increase.
So how can this be blamed on humans driving SUV’s?
that’s easy. we’re sucking oil out of the ground and nature abhors a vacuum. the real question will be “how did my ribeye contribute?”
Sea Water has lots of dissolved Halite, NACL, and Calcite, CaCO3, to name a few. So there is your carbon being recycled into the mantle to produce Hydrocarbon fluids and Gas phases and in time expelled back into the crust, continental and oceanic reservoirs via deep faults.
Even notionally, this can be disproved. If it was true, then major subduction zones (past and present) would be correlated with major oil and gas provinces. Instead, we find the inverse to be true.
As an example, the west coast of Oregon/Washington or the east coast of Japan are major subduction zones, and, according to your theory, would be foci for hydrocarbon expulsion back into the crust, but that is clearly not the case. As a counter-example – most major hydrocarbon provinces in the world are on passive margins – areas with no evidence of subduction – the Gulf of Mexico, the Persian Gulf, the west cost of Africa, around the South China Sea. These are the opposite geologic settings from what your theory suggests.
“If it was true, then major subduction zones (past and present) would be correlated with major oil and gas provinces.”
Why?
Because the original poster – JBorn – states that light metals from sea water being recycled back into the mantle (I assume the process is subduction since he does not propose an alternative) provide the needed carbon to produce oil and gas.
In my experience, no subsurface fluid or gas – water, magma, oil, gas, CO2, H2S, travels very far laterally from its source – a few miles maybe? If my experience is reflective of reality, then how does this newly generated hydrocarbon migrate from the subduction zones to someplace else? And why are major oil and gas fields not associated with this process as it is described? There is no evidence in the real world for such a process, or even the hint of such a process.
So, what your saying is, that there really is accelerated sea level rise but its being hidden by some sea level going down the big drain. This explains why we dont see the unprecedented, catastrophic, tipping point levels in sea level rise that alarmists expect. My God! if its all those things and we dont notice its worse than we thought!
Clearly only money can save us! where do I send my check?
Oh Boy! “We don’t know WTF is going on!” True science, none of this ‘the consensus is’ garbage.
Previous estimates only out by a factor of 3? Not exactly surprising, really.
Like silly guesses about the amounts of methane emanating from the intestines of ruminants, I would be surprised if their estimates eventually proved to even be accurate to within a factor of 10. It’s usually a case of “Just write the report and stick in any number(s) you want. Nobody will read it or take it seriously anyway”.
Ever hear of the hollow earth theory ? If so, There is plenty of space for water to go. Not saying i believe it but just saying.
THERE IS NO CO2 CLIMATE WARMING ON MARS !!!
Why ?
Does increased CO2 in the atmosphere cause the Earth to warm ?
A comparison with Mars is worth noting. In fact it’s very interesting
CO2 makes up 96% of the composition of it’s atmosphere and weighs ~24 terratonnes.
By contrast CO2 in the Earth’s atmosphere is 0.00048 % & weighs ~ 2.4 terratonnes.
(All these figures come from Wikipedia. I’m not making them up. )
Ummmmmm ? Let’s think about that folks..
Despite all that CO2 in the Martian atmosphere, there is no CO2 greenhouse warming to speak of..
In Winter ambient temperature on Mars can reach a minimum of -136 degrees C..Very bloody cold ! And in Summer ambient temperature gets a maximum of just 35 degrees C.
What’s all that CO2 on Mars doing ? Maybe all that martian CO2 is just not pulling it’s climate warming weight…..
Or is that all the water on Mars is frozen solid under the .. And there is no water vapor in the Martian atmosphere to really get a greenhouse effect going…like we have here on much warmer, much more livable, & much pleasanter, Earth
By the way this has all been said & written about before. But still the CO2 ‘Climate Warmists’ are still crying ‘Wolf, Wolf, Wolf ’ at rising CO2 here in order to scare us…Dopiness abounds..
And unfortunately it looks like my own local member of our Australian parliament ( who I helped to elect in July ) has become a convert as well….
Note that on Mars there is no atmosphere to speak off that will protect you against the sun. Here on earth, solar flares are continually neutralized by earth’s atmosphere by reactions with oxygen, H2O and nitrogen/oxygen, forming ozone, peroxides and N_oxides, respectively. If this did not happen we would all be dead here. Hence the lesson I am trying to teach here: don’t go to Mars until you first established an earth like atmosphere.
I’m not going any time soon Henry !
Ohhh! Good.
I am not sure if anyone here watched is or is watching the series ‘Mars”?
In it AGW is of course accepted as the gospel truth and very much propagated. Deniers [like those in the Rep. Party] are ridiculed.
I even heard Elon Musk saying he is 70% sure he will go to Mars.
I thought about that. Why would he chose 70%? I think he must be sure that like Steve Jobs he is 70% sure of dying of some ailment? so once he is sure of the fact that he is dying, going to Mars is a good place for his grave?
Some of the seawater remains as salt water. Just a few miles north of Hwy 34, 2-3 foothills west of Loveland, Colorado, there is old seawater just a few hundred feet down. This was a problem in the 70s when people built on small acreages, and drilled wells for water. This water is at 5000’+ elevation now.
I am not sure but I would say with reasonable certainty that whatever [liquid] water is sucked into earth will come out as water [vapor] somewhere else, where it finds a little hole to escape. Hence the existence of volcanoes? I don’t expect it to be splitting up or being absorbed/adsorbed, as claimed…..
Now all this water being sucked in coming out as water vapor , would that not contribute to earth’ s natural warming processes? Water is a major GH gas and there is about 10x more of it in the atmosphere than CO2.
Anyway, anyhow, my empirical method shows that CO2 is not to blame for the warming, AGW or non-AGW.
Click on my name and go figure.
The amount of water coming out of volcanoes is infinitesimally small compared to the amount being evaporated from the ocean surface by the sun.
I am sure you are right about that. But seeing that everyone [i.e. non deniers] is able to show how global Tavg and CO2 has been rising, over the past century or so, can somebody also show me how much global RH has been rising?
I had a strong case of deja vu. Then I looked and behold the same discussion was posted 2 weeks ago in this forum about the same Nature article, with almost the same comments.
https://wattsupwiththat.com/2018/11/15/earth-devouring-its-own-oceans-film-at-11/
I don’t think that thread featured as many plate tectonics “deniers” or abiotic oil aficionados.
On the one hand, it isn’t right, abiotic oil was a subject, on the other hand discussing about isn’t a sign for aficionados.
In 10 years, New York will be high and dry – you heard it here first
Not a surprise, really. Look at the shape of the Earth? It’s round – really round. Even a bit overly-round in the middle, making it pudgy! Being thirsty all the time is a sign of the onset of diabetes. Not surprising at all, really…
Verdviewer: The added pressure increases the hydrostatic pressure a tiny amount: 120m sea level rise over the 11,000m deep Mariana Trench. The continental crust of the land under which this oceanic plate is sliding is more than 11,000m of lithostatic pressure, say ~3 x the hydrostatic pressure.
“All the while, the plate continues to crawl ever deeper into the Earth’s mantle, bringing the water along with it.”
The plate goes away from us, so it takes the water along with it. If it goes, it takes. If it comes, it brings.
But even those of us who know how to use “bring” and “take” are doomed.
As we have long feared, the jackassification of science has crept out of the realm of climate studies and infected anything even remotely related…and the rot is spreading at an accelerating rate.
Thanks a heap climate liars…you broke science.
Errors in science thinking happen for a variety of reasons, and science moves on. Remember when some thought that gravity traveled faster than light. Every now and then a nutty idea turns out right, like plate tectonics, quantum dynamics, dare I say entanglement?
I am fairly certain that the degree to which entire generations are being miseducated, not to mention lied to and taught what to think rather than how to think, is unprecedented in the industrial age.
This has grave implications for the ability to simply shrug off a widespread but mistaken belief.