Since ancient times, various speculations about the interior of the earth have never stopped. In ancient times, people speculated that there was another world inside the earth, so there were myths and legends about hell and hell. After the era of science and technology, although people don't believe in the legend of hell inside the earth, there are still many people who think that there may be mysterious space inside the earth and people may live there.
There has always been talk about underground civilization, but we have never found any evidence. In ancient times, people could explore the underground. However, when people entered the era of science and technology, the desire to explore the interior of the earth became stronger and stronger, so scientists began to drill underground.
When it comes to drilling experiments, it is necessary to talk about the competition between the United States and the Soviet Union in the last century. At that time, there were two great powers in the world, one was the Soviet Union and the other was the United States. Moreover, these two countries are competitive and both want to push each other more and more. As we all know, the first artificial satellite was launched by the former Soviet Union, and the astronaut who landed in space for the first time was Gagarin of the former Soviet Union. Later, the United States, unwilling to lag behind, began a larger-scale space exploration project on the moon and succeeded. So America made history and became the first country to put a man on the moon. Until now, no second country has achieved manned landing on the moon.
At that time, apart from the exploration of space, the competition between the United States and the Soviet Union also had a big plan for the earth, that is, exploring the underground world. At that time, the United States planned to drill through the crust with an average thickness of 17 km, but it was impossible to drill through the crust from the ground, so the United States chose submarine drilling. Moho is the dividing line between the crust and the mantle, and it only takes about 7 kilometers to drill down from the seabed to the depths of the mantle.
American scientists use Kuszler drilling boat to drill holes in the waters near Guadeloupe. If successful, you only need to drill down an average of 6 kilometers to 7 or 7 meters to drill through the earth's crust and enter the geosphere. At that time, it was planned to spend 300 million dollars, and the first stage of experimental drilling was successful, and rock samples with a depth of 183 meters were harvested from the ocean crust.
However, with the progress of drilling, it becomes more and more difficult, especially in the seabed. According to the estimation of scientists at that time, it would cost more than 300 million dollars to complete this drilling experiment. It is necessary to apply for more funds from the US House of Representatives, but due to political and economic reasons, the application was not passed, and the Moho project of 1966 ran aground.
Seeing the failure of American underground drilling experiment, the Soviet Union began a fierce attack on underground exploration. 1970, code-named "Earth Telescope Project" started. At that time, the Soviet Union selected thousands of researchers to secretly assemble in kola peninsula for geological drilling. It is very wise to choose to drill through the ground, but if you want to drill through the crust, you need to drill through 17 km.
Soviet scientists also spent a lot of money to surpass the United States, but they didn't expect to encounter one difficulty after another after the plan was launched. For this reason, Cora's ultra-deep drilling experiment took 20 years, and then the project was forced to stop and the hole was closed. The deepest part of the ultra-deep borehole in Kola reaches12262m, which is already the deepest underground borehole in the world.
After Cora's ultra-deep drilling experiment stopped, many people who didn't know the truth began to guess, and many versions appeared. The most magical rumor is that when the hole reached the deepest part, it made a scream similar to human beings. Some people even say that it is a hell, and there are even rumors that there are demons in Cora's ultra-deep drilling. Even more amazing is that there is a screaming recording, which seems to be in the depths of the hole.
Of course, all the above are false and unreliable. Some people may ask, if the rumor is false, what is the reason why Cora's ultra-deep drilling experiment really stopped? What did scientists discover through this ultra-deep drilling experiment? In fact, the real reason for stopping the drilling experiment is that it is impossible to continue drilling, because the current materials of human beings are not up to the level of continuing drilling.
As we all know, the interior of the earth is a high temperature and high pressure environment. With the increase of depth, the internal temperature and pressure are increasing. And the deeper the depth, the stronger the geological structure. The harder the rock, the higher the temperature and pressure, which makes the drill bit unbearable. The first ultra-deep drilling in Kola12000m took about 10 years to complete. However, 10 meter was also used for the last 262 meters. At12000m, the drill bit was continuously softened by the high temperature in the deep underground, and it was badly worn, so it was scrapped several times, and then it was necessary to upgrade and replace the drill bit from the depth of10000m.
However, it takes about 8 hours to change the bit back and forth each time, so the progress is very slow. By the time the drill bit reaches12,262 meters, it is difficult for the drill bit to drill through the deep underground strata, so the ultra-deep drilling experiment that has been going on for 20 years is stopped. In the future, when human science and technology are more developed and stronger drill bit materials with high temperature and high pressure resistance are developed, it is believed that Cora's ultra-deep drilling experiment may be restarted and continue downward along the original depth until it penetrates the crust and goes deep into the mantle layer.
So what are the major discoveries made by Soviet scientists in 20 years of ultra-deep drilling experiments? If you don't find it, I believe no one will believe it. In fact, the drilling depth of 12262 meters has opened up more than half of the earth's crust, and many important discoveries are certain. One discovery is that there is no granite-basalt transition layer at 7 kilometers underground. It turns out that scientists have found that the position velocity within 7 kilometers has changed through seismic wave detection. They think there will be a granite-basalt transition layer here, but it can be found through drilling experiments that there is no such transition layer.
The second discovery is that a large amount of hydrogen suddenly emerged when drilling into a mud somewhere, indicating that the hydrogen content in the earth is also very rich. The third discovery is that scientists found a gold layer deep underground, where the gold content reached an astonishing 80 grams per ton. You know, if we exceed 4 grams/ton on the surface, we can meet the initial commercial mining value. The content of 80 grams per ton is amazing, but it is a pity that this depth is 9000 meters underground, and it is impossible for human beings to mine with current technology.
A rich gold layer was discovered 9000 meters underground, which also gave scientists a new understanding of the early history of the earth. For a long time, scientists believed that precious metals such as gold on the earth came from outer space. Some scientists speculate that in the early days of the earth, it experienced a Huang Jinyu, and a large number of gold asteroid fragments fell behind the earth. At that time, the earth was still molten. After gold fell behind the earth, most of it went deep underground, and only a tiny part remained on the earth's surface. Huang Jinyu brought at least 6 billion tons of gold to the earth.
In the past, scientists also speculated that there should be a gold layer inside the earth, but Cora's ultra-deep drilling experiment proved this and knew the specific depth of the gold layer. When the technology is more developed in the future, it may be possible to go deep into the gold layer of 9000 meters underground and extract gold.
The fourth discovery is the discovery of fossil samples of microorganisms at a depth of 12000 meters. Although it is only a fossil sample, it is of great value for human beings to explore underground life. Now scientists have discovered that there is a rich underground ecosystem under our feet, in which the total biomass is at least twice that of marine life. It can be seen that the world inside the earth is definitely more wonderful and mysterious than we thought.