An international team of scientists has begun preparations for the journey to the center of the Earth. This figure of speech researchers call the project Mohole to Mantle, whose members aim to reach the mantle. To achieve it they are going to drill the earth#39;s crust in places the ocean floor, where its underlying layer fits quite close.
It should be noted that geologists have repeatedly made an attempt to get to the layer that underlies our earth#39;s crust. It all started in 1904 when the Croatian scientist Andriy Mohorovičić found that seismic waves caused by earthquakes propagate much faster in those layers that the lower 30 miles, than those above that mark. So was the upper limit mantle, called in honor of the discoverer Mohrovichicha abroad.
So, it turned out that the mantle is much closer to the earth#39;s surface than previously thought. However, a little later geologists have found that in some places the Moho boundary runs slightly higher than 30 kilometers. Thus, at the bottom of the oceans there are areas where, until the mantle is called, just a stone#39;s throw - it starts at a depth of just five kilometers from the cortex. Accordingly, it is in these areas and should be deep drilling.
By the way, one time it#39;s trying to do. In the 50-ies of the last century, American scientists Harry Hess and his colleague Walter Munk drafted Mohole. The exercise was carried out on a drilling expedition ship in the Caribbean Sea. Scientists were able to drill the bark on 183 meters around the island of Guadeloupe and collect a lot of valuable samples. However, studies hampered by the fact that in those days there were not developed technology capable of holding a drilling ship in the same place on the high seas.
Shortly after the successful return of the expedition, the project Mohole for unknown reasons was closed - for some reason the state has refused to finance it. However, geologists, this first attempt, released a lump, do not stop - drilling in the ocean crust to reach the mantle continued. One of the most successful studies of this kind was held in the beginning of this century: the 1507-meter hole on the coast of Costa Rica, though not the most deep in the ocean, nonetheless came closest to the Moho boundary (which took place in those places at a depth of 5 , 5 kilometers).
And recently, an international team of researchers said that, too, is going to get to the mantle. The work will be carried out on board a special Japanese ship Chikyu. First of all, the scientists want to get to the fault that caused the devastating Tohoku earthquake last year. However, the project was called Mohole to Mantle, there are other goals.
Although the mantle accounts for 68 percent of the mass of the Earth, we know very little about it. We do not have any pure sample of the mantle - the participant of the project Damon Teagle of the National Oceanography Centre, UK. And it#39;s true: even though some samples of mantle rocks sometimes reach the surface of our planet, all of them are dirty. For example, the rare mantle nodules found in lava, suggest that the mantle is composed of minerals rich in magnesium and silicon-poor (such as olivine and pyroxene).
Of course, in some places at the bottom of the ocean mantle rocks are found in the clear, but when in contact with sea water for many years, they have changed the composition of his. And it turns out that the difference between these models and these mantle nodules, about the same as that between meteorites and direct samples of rocks from another planet. Although contaminated and minerals can also be studied, yet no pure samples can not provide even the basic facts such as the composition of the mantle, ways of its formation, etc.
Well, without such information it is impossible to figure out patterns of a process such as mantle convection (more on that, read the article Volcanoes - anxiety level increases), which not only leads to the drift of continents, but the culprit is such unpleasant for human phenomena, such as earthquakes and volcanic eruptions. However, when scientists fall into the hands of its indicators (such as noble gases and the corresponding isotopes), you can find out how and when our planet is divided into core, mantle and crust, when the tectonic plates and when it will end. In addition, the mineral composition of the upper mantle could tell how water, carbon dioxide and energy transmitted to the cortex and how they affect the global geochemical cycles (which will help to more accurately predict the same earthquake).
In addition, it may be possible to prove the recently proposed hypothesis that the mantle is not lifeless. This assumption arose after the 2011 Tullis Onstott of Princeton University (USA) found microscopic roundworms at a depth of four kilometers in the South African gold mine. It also found that bacteria can live in even greater depth - up to five kilometers. A little earlier, biologists have found marine organisms at a depth of 1.6 kilometers off the east coast of Canada.
The most interesting is that the high pressure at great depths, which at one point would have crushed a man to bacteria and small metazoans is not a serious problem. Laboratory tests have shown that microbes can survive a thousand atmospheres. Moreover, at the time the bacteria were found even in the Mariana Trench, a 11-km-long water column, where the pressure is much higher than at the turn of Moho. There is experimental evidence that such an extremely high pressure in a hot environment for bacteria even useful because it does not allow them to existing boiling water.
In addition, according to the calculations, the temperature just below the Moho - 120 degrees Celsius. It#39;s tempting to close to the upper limit of the known forms of life - 122 degrees Celsius, but still below, - said John Parkes of Cardiff University (UK). As you can see, there are no obstacles to the penetration of living organisms in the upper mantle is not available. Well, if they can be found there, then the hypothesis of Norman Slip of Stanford University (USA) that all of the nitrogen in the mantle derived from ammonia, generated over many billions of years of living beings can be regarded as proven.
So, as you can see, the results of the project Mohole to Mantle able to please many. However, as will be boring? Damon Teagle told that the biggest problem is the production of the corresponding bit. After drilling the hole diameter of 30 centimeters of hard igneous rocks at a speed of one meter per hour drill bit will work normally only about 50 hours. Furthermore, the new superhard material would also have to withstand the pressure in the two kilobars and temperature to 250 degrees Celsius. However, the report, released in 2011 by Blade Energy, which is the technical support of the project, says that this drill can be done.
Furthermore, there is a problem research funding. According to preliminary calculations, the cost of only one vessel Chikyu will cost one billion U.S. dollars. However, the money promised to give, for example, the Japanese government has taken the lion#39;s share of the cost. That, in general, is not surprising, because the project can ultimately help seismologists this is in the active zone of the country to more accurately predict earthquakes. Other countries such as the United States, have also expressed their interest.
Will also have to choose one of three prospective areas for drilling. All candidates are in the Pacific (one, by the way, just in the place where the precursors were drilled from the project Mohole), and one is located relatively close to the mid-ocean ridges, where new crust is formed. In these areas, lifting magma increases the seabed so that there is relatively shallow, and breed colder.
So, if all goes according to plan, prepare for the journey to the center of the Earth will begin next year. To the mantle as the scientists hope to reach by 2020. And in the case of successful completion Mohole to Mantle knowledge of what#39;s inside this layer of our planet will no longer be purely theoretical ...
Material: pravda.ru
