Geophysicists Detect Evidence of Large Amounts of Water in Earth’s Mantle
A new study reveals large amounts of water bound to the rock in the center of the Earth's mantle.
The researchers found evidence of "the value of the ocean" deepwater potential in the United States.
Although not present in a familiar form, the basic components of water are linked in the rock in the center of the Earth's mantle, and enough water to represent the largest reservoir in the world according to the study.
For many years, scientists have tried to determine exactly how much water can be cycling between the surface of the Earth and the inner layers through the action of plate tectonics. Geophysicist Steve Jacobsen Northwestern University and the University of New Mexico seismologist Brandon Schmandt found pockets of magma about 400 kilometers below North America - a strong indicator of the presence of H₂O stored in the crystal structure of high-pressure minerals those depths.
"The total heat content H₂O has long been one of the most poorly controlled" geochemical parameters "in the Earth Sciences. Our study found evidence of widespread hydration of the mantle transition zone," Jacobsen said.
For at least 20 years geologists have known from laboratory experiments that the area of the Land of transition - a layer of rocky mantle of the Earth between the lower mantle and the upper depths of between 250 and 410 miles mantle - can theoretically contain about 1 percent of its total weight as H ₂, mineral called wadsleyite and ringwoodite related. However, as Schmandt said so far has been difficult to determine if the water tank is empty potential, as many have suggested, or not.
If this proves to be a substantial amount of H₂O in the transition zone, and laboratory experiments recently conducted by Jacobsen indicate that there should be no large amounts of what he calls "partial melting" in areas where warm flowing through the area. This rich silicate melt water molten rock is produced in the grain boundaries between crystals of solid minerals and may represent about one percent of the volume of rock.
"The merger is because the hydrated rocks are made of the transition zone, where rocks can contain many H ₂, in the lower mantle, where rocks can not contain as H ₂. Fusion is the way to get rid of H₂O that do not fit this crystal structure in the lower mantle, "says Jacobsen.
He adds:
"When a rock starts to melt, regardless H₂O is bound up in the rock will go in the bathroom immediately. Hence, the melt would H₂O that remaining solid concentration much higher. We're not sure how it got there. Perhaps he was trapped there since the beginning of the history of the Earth, or perhaps it is constantly recycled by plate tectonics "
Mantle Rock Studies
The combined study of the analysis of seismic data Schmandt of USArray, a network of more than 2,000 seismometers across the United States, with laboratory experiments of Jacobsen, in which he examined the behavior of mantle rocks under conditions designed to simulate the high pressures and temperatures of 400 miles below the surface of the Earth.
The EarthScope USArray is part of, sponsored by the program of the National Science Foundation. The experiments were conducted at two sites Jacobsen Ministry user of energy, the Advanced Photon Source at Argonne National Laboratory and the National Synchrotron Light Source at Brookhaven National Laboratory.
Taken together, the findings produced strong evidence that fusion can occur at about 400 kilometers deep in the earth, with H ₂ $ stored in mantle rocks, such as those containing mineral ringwoodite, which is likely to is a dominant mineral in these depths.
Schmandt said he made the discovery after conducting seismic images of the boundary between the transition zone and lower mantle. Evidence that, in areas where the "abrupt transitions" as are present in the melt, was found the energy of the earthquake was converted from a compression wave, or longitudinal, shear or S waves Phase waves S converted in areas where layer is rolled down and out of the transition zone showed a significantly lower rate than the surrounding mantle. The discovery suggests that the water from the surface of the Earth can be driven at these great depths for plate tectonics, ultimately resulting in the partial melting of rocks found deep in the mantle.
"We used a lot of conversions of seismic waves to see many parts of the United States who may have some melt just below the transition zone. The next step was to compare these zones in areas where flow models to predict the mantle flow to the bottom of the transition zone, "Schmandt said.
Big Questions
For the future, Jacobsen admits that some big questions remain. For example, if the transition zone is full of H₂O, what does this say about the origin of water on Earth? And the presence of ringwoodite in the planet's mantle necessary for a planet to retain original water sufficient to form the oceans? Also, how is the H₂O in the transition zone connected to aboveground tanks? It is the transition zone, if it contains more than oceans, somehow dampen the amount of liquid water on the surface of the reservoir geochemistry H₂O Earth?
"An analogy may be a sponge, which must be filled before liquid water may be supported on the top. Water was in the transition region by said tectonic plates of the early history of the earth, or does the mantle of oceans gas until equilibrium between the surface and the inner layers? "Ask Jacobsen is reached.
However, the investigation is likely to be of great interest to astrobiologists largely because water is often closely linked to the formation of biological life. Remote geochemical analysis could be a way to detect whether these processes occur elsewhere in the universe, and it is likely that this analysis involve the use of gamma rays from neutron spectrometers and X-ray of the type used by the NASA MESSENGER spatial distance for geochemical mapping of Mercury.
"On other planets inaccessible that it is impractical to apply the type of earthquake that I used. Imaging So, I guess the geochemical analysis of volcanic rocks from other planetary bodies can be our best way to check if the volatile are stored inside the planet, "Schmandt said.
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