At great depths underground, it is very hot, and the pressure is growing - hell is worse than what Dante described. But more recently, scientists have begun to suspect that there is something in this hell that no one expected to find there - water. And in large quantities: at a depth of four hundred kilometers, underground water is ten times more than in the oceans on Earth.
But this water does not flow or splash. It exists in the form of droplets sometimes several or even a single molecule of minerals embedded in the crystal lattice. But it is this water that can shed light on some unresolved mysteries about the origin of the Earth, about the grandiose eruptions of volcanoes with lava rivers.
There are many different allusions to the existence of this "hidden" water. The first is the insufficient amount of water on our planet compared to meteorites. Scientists have been pondering this mystery for many years.
According to Thomas Ahrens, a geophysicist at the California Institute of Technology in Pasadena, you can estimate how much water was in the solar system in its early youth if you analyze the composition of the meteorites that have come down to us from those distant days. They contain about three percent of water, and on Earth it is small fractions of a percent (of the total mass). A natural question arises: where did all this water go?
Many scientists believe that soon after the formation of the Earth, it was struck by a celestial body the size of Mars. It knocked out a significant chunk of the mass from which the moon was formed, deprived our planet of the atmosphere, and at the same time most of the water. But there are indications that something remains deep in the Earth.
The first is the content of helium-3 and helium-4 isotopes in lava outcrops from volcanoes. Helium-4 is formed as a result of radioactive decay, and helium-3 remained from the first moments of the birth of the Universe. According to Ahrens, helium-3 comes out of deep rocks, it is much more volatile than water. If there is helium-3 in the depths of the Earth, then it is quite possible that there is also water. “Helium-3 gives us clear evidence that the Earth does contain various substances inside its rocks,” Arens emphasizes.
The second is kimberlites, rocks enriched with iron and magnesium, which come to the surface of the Earth from its mantle through narrow channels. They lift diamonds with them, which can only occur at depths of at least 180 kilometers. They travel along these pipes and rocks similar to mica, which bring a lot of water upstairs.
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Stephen Haggerty of the University of the American State of Massachusetts discovered that kimberlites carry up a mineral called majorite, which forms at depths of 300 to 670 kilometers. And from there they bring water, and 670 kilometers is the border between the upper and lower mantle.
Seismic data also testify to water: water slows down the speed of sound passing through rocks. This is exactly what geologists see - seismic waves are inexplicably slowly passing through the mantle. Until the end of the eighties of the last century, it was believed that the inside of the Earth was dry enough. The generally accepted point of view was that there may be water under the surface, but no deeper than 200 kilometers, there is simply nowhere for it to hide. The rocks are too hot to contain water.
The breakthrough came at the University of Colorado when Joseph Smith was studying a mineral called Wadsleyite. It consists of silicon, magnesium and oxygen and, according to scientists, is located at a depth of 400 to 700 kilometers below the surface of the Earth. Of course, scientists cannot look at such a depth and explore the mineral in natural conditions. They create a "hellish" heat and pressure for them in their laboratories. Wadsleyite has been studied since 1960, but in dry form. Smith's discovery was that he discovered its unusual property - even when heated above one hundred degrees, it retains water.
In 1987, a group of Australian researchers led by Ted Ringwood discovered that several other minerals can contain water at high temperatures and pressures. Jay Bass of the University of Illinois noted, "All of a sudden, we realized that there are oceans and oceans of water under the Earth." It is estimated that wadsleyite may contain 3.3% water. It doesn't sound very impressive, but there may be an abyss of wadsleyite beneath the Earth. According to Smith, at a depth of 400-500 kilometers there may be sixty percent wadsleyite, and then a measly 3.3% of the water in it will give us ten of the Earth's oceans of water, which were discussed at the beginning.
Dan Frost, a geologist at the Washington Geophysical Laboratory, believes there could be even more water. His staff estimates that glassy lava materials can contain up to five hundred parts per million of water. And this is another thirty oceans. The main problem is that scientists get all information about the minerals of the mantle from its upper layer. Next comes the extrapolation that the entire mantle is uniform.
The search continued, and in 1997, a group led by Smith found wadsleyite-II, another hydrous mineral that does not decompose even deep in the mantle. And yet, these are only hypotheses about how minerals will behave in underground conditions.
The presence of water inside can greatly influence events such as the emergence of new islands and massive eruptions of volcanic lava. Both are examples of "hot spots", which, according to scientists, represent the outcrops of molten lava to the surface. Previously, it was thought that the lava comes to the surface due to the rise of hot bubbles, but the possibility that the process of liquid evaporation could be the cause of the rise was never considered.
The main objections of the opponents of underground oceans are simple and understandable: under the influence of high temperatures, water must evaporate. But the experiment brings more and more evidence in favor of the supporters of groundwater. Guust Nolet of Princeton discovered that seismic velocities were unexpectedly slow in the tectonic shield beneath Central Europe. It is an old continent and consists of cold, dense rocks, where nothing should lead to a decrease in the speed of seismic waves. Nolet believes that deep water is the only possible explanation.
The hypothesis of underwater oceans was just born, and scientists have not yet translated it into the category of a reliable theory. One of the latest areas of research is an attempt to understand whether water passes from the surface into the depths of the Earth and how much of it comes out from there. In particular, Nolet believes that the area under Europe is constantly being fed by water from the surface. Interesting calculations are underway on how groundwater can affect the state of the atmosphere, the greenhouse effect, the present and future climate.
Alexander Semyonov