The deepest well in the world has served as the source of the legend. The deepest well in the world

23.03.2022

The party said: "We must!". Komsomol answered: “Yes!”. The slogan from the poster from the times of the USSR still did not leave my thoughts while I was going on a business trip to. The only pleasant moment was a meeting with a friend whom I had not seen for almost 10 years. Masha promised me an excursion to the “road to hell”

180 km from Murmansk is located Kola ultra-deep well (12262 m). Drilling began in 1970. It is with her that the legend is connected that Soviet scientists released demons, drilling a path to the underworld. After overcoming a depth of 12,000 m, the employees of the drilling station began to hear strange voices from the mine, similar to human screams. Some of them suggested that people hear the cries of sinners who have fallen into hell. The current depth was reached in 1990. Work was suspended in 1992, and in 2008 the project was completely closed and most of the equipment was dismantled.

From Murmansk we went by car to Zapolyarny. Almost 160 km, slowly, drove in 3 hours. Around the tundra, somewhat strange and dull, the vegetation is scorched in places, in the lowlands there is a small, crooked, sparse forest and snow that has not had time to melt.

What is left of the devil's well lies 8 km from Zapolyarny, but you can skip the turn from the highway without knowing the terrain. Turning off the road, we drove into the region of mountains from industrial waste. These are dumps, huge hills of black stone left after the mining of nickel and copper.

A few tips for those wishing to see the legendary well:

July is the warmest time of the year;
sneakers for light trekking are suitable as shoes;
warm clothes, sudden changes in temperature are possible;
it is easy to get lost among quarries and dumps;
in the ruins you can stumble upon puddles of technical fluid, mercury thermometers, metal pins, glass, walk more carefully, it is advisable to have a first aid kit with you.

All that remains of the Kola Superdeep are bleak ruins under the scorching sun, reminiscent of the greatest discoveries made while drilling.

Rain, fog, ten degrees Celsius. It's called polar summer...

A grader going into the sky is a technological road, and we should not be here. We press to the right, to the side of the road, in order to let the convoy of heavy trucks coming towards us, writes Artem Achkasov

High bodies are loaded to the top with black gravel - copper-nickel sulfide ore. We rise higher, and now a viscous cloud has stuck around our Fords, the wiper leashes flashed rapidly. But the visibility did not get better because of this - in the thick white wool I can only see the rear lights of the car in front. We carefully make our way between the waste heaps.

Suddenly, huge concrete buildings, similar to factory buildings, rise up in the fog.

Welcome to the SG-3 facility, also known as the Kola Superdeep Well. More precisely, what was left of her ...

A merciless thing is history. Its pages are torn out, rewritten, swapped. What every Soviet schoolboy or student knew now does not matter, he has no place in the memory overflowing with various entertainments. Scientific achievements are understood as a new application for a smartphone. The achievements of Russian science are little known. The achievements of Soviet science are ridiculed or completely forgotten. Meanwhile, in a number of areas, Soviet scientists were actually ahead of the rest. This also applies to geological research.

It was for scientific purposes that in 1970 the project of the Kola Superdeep Well was launched. The place near the city-factory Nickel in the Murmansk region was not chosen by chance - firstly, due to the already known abundance of valuable resources in this region (nickel, apatite, titanium, copper, and so on). Secondly, it is here that the lower boundary of the earth's crust comes as close to the surface as possible. And this means that drilling an ultra-deep well here would help not only to identify mineral reserves (in particular, to explore the deep structure of the Pechenga nickel deposit), but also to answer questions about the structure of the Earth, about which scientists had a very approximate understanding in those years. Among other tasks was a comprehensive development of deep drilling technology in order to improve a new generation of equipment for monitoring, research, automation and control of the drilling process.

At first, drilling was carried out with the Uralmash-4E serial rig, designed for oil wells. Down to a depth of 2,000 meters, the bore was drilled with steel drill pipes, which were later replaced with aluminum pipes due to their lighter weight and greater strength. At the end there was a turbodrill - a turbine 46 meters long with a destructive crown at the end, driven by a clay solution, which was pumped into the pipe under a pressure of 40 atmospheres.

Upon reaching the mark of 7264 meters, the sinking was carried out by the more advanced Uralmash-15000 complex, which was the embodiment of Soviet science and technology. The system worked with a lot of electronics and automation. Carbide crowns were replaced with diamond ones. In conditions of high soil density, the resource of bits did not exceed four hours, i.e. from six to ten meters of deepening. After that, it was necessary to lift and dismantle the entire multi-ton column of 33-meter pipes, which took at least 18 hours closer to the 12-kilometer depth.

You ask why all these difficulties? The fact is that almost every meter of penetration was accompanied by a scientific discovery. In the best years, almost two dozen scientific laboratories worked at SG-3. The study of rock samples raised in the core and the lowering of special equipment into the well completely turned the theoretical knowledge of scientists about the structure of the Earth. So, the granite belt turned out to be much thicker than scientists thought. There was no basalt at the expected depth at all - porous granite rocks went instead, which led to multiple collapses and accidents at the drilling rig. Fossilized microorganisms were found at great depths, which made it possible to assert that life on the planet appeared at least one and a half billion years earlier than previously thought. The statements of scientists about the temperature regimes in the bowels of the planet were not confirmed either - it turned out to be much hotter there ...

Of course, drilling such a deep well was very costly. Soil collapses led to accidents, curvature of the trunk. Another accident at a depth of 12,262 meters, which practically coincided with the collapse of the USSR, turned out to be the last in the history of the Kola superdeep. There was no one to finance this project. In the mid-nineties, the well was mothballed. Ten years later, it was finally abandoned, while remaining at that time the deepest well in the world (and the only one drilled for scientific purposes).

Of course, then the station, which once gave the world dozens of scientific discoveries every year, was completely plundered.

All buildings were destroyed, including the 70-meter tower that housed the drilling rig. At the SG-3 facility, rare visitors feel like stalkers.

The wreckage of the former world crunches loudly underfoot. Broken glass, ceramics, rusty iron, broken bricks.

In front of the main building lies the skeleton of a caterpillar conveyor.

There are gaps in the walls of the buildings. Obviously, someone pulled out expensive equipment in this way.

Chemicals are scattered in the former laboratories.

Instead of expensive electronics, electrics and automation, there are empty cabinets torn off their fixtures.

Suddenly, a diesel engine rumbles through a cloud of fog. Instinctively, I duck behind the collapsed ceilings. An old Mercedes minibus slowly drives up to the ruined building. The open rear door slams against the rusty bodywork. Metal hunters continue their dirty work...

At a depth of 410-660 kilometers below the surface of the Earth, the ocean of the Archean period. Such discoveries would not have been possible without the ultra-deep drilling methods developed and used in the Soviet Union. One of the artifacts of those times is the Kola super-deep well (SG-3), which, even 24 years after the cessation of drilling, remains the deepest in the world. Why it was drilled and what discoveries it helped to make, says Lenta.ru.

The pioneers of ultra-deep drilling were the Americans. True, in the vastness of the ocean: in a pilot project, they involved the ship Glomar Challenger, designed just for this purpose. In the meantime, the corresponding theoretical base was being actively developed in the Soviet Union.

In May 1970, in the north of the Murmansk region, 10 kilometers from the city of Zapolyarny, drilling began on the Kola superdeep well. As expected, this was timed to coincide with the centenary of the birth of Lenin. Unlike other ultra-deep wells, SG-3 was drilled exclusively for scientific purposes and even organized a special exploration expedition.

The drilling site was unique: it is on the Baltic Shield in the Kola Peninsula region that ancient rocks come to the surface. Many of them are three billion years old (our planet itself is 4.5 billion years old). In addition, here the Pechenga-Imandra-Varzug rift trough is a cup-like structure pressed into ancient rocks, the origin of which is explained by a deep fault.

It took scientists four years to drill a well to a depth of 7263 meters. So far, nothing unusual has been done: the same installation was used as in the extraction of oil and gas. Then the well stood idle for a whole year: the installation was modified for turbine drilling. After the upgrade, it was possible to drill about 60 meters per month.

A depth of seven kilometers brought surprises: the alternation of hard and not very dense rocks. Accidents have become more frequent, and many caverns have appeared in the wellbore. Drilling continued until 1983, when the depth of SG-3 reached 12 kilometers. After that, the scientists gathered a large conference and talked about their successes.

However, due to careless handling of the drill, a five-kilometer section remained in the mine. For several months they tried to get it, but did not succeed. It was decided to start drilling again from a depth of seven kilometers. Due to the complexity of the operation, not only the main shaft was drilled, but also four additional ones. It took six years to restore the lost meters: in 1990, the well reached a depth of 12,262 meters, becoming the deepest in the world.

Two years later, drilling was stopped, subsequently the well was mothballed, but in fact it was abandoned.

Nevertheless, many discoveries were made at the Kola superdeep well. Engineers have created a whole system of ultra-deep drilling. The difficulty was not only in depth, but also in high temperatures (up to 200 degrees Celsius) due to the intensity of the work of the drills.

Scientists not only moved deep into the Earth, but also raised rock samples and cores for analysis. By the way, it was they who studied the lunar soil and found out that in composition it almost completely corresponds to the rocks extracted from the Kola well from a depth of about three kilometers.

At a depth of more than nine kilometers, they found deposits of minerals, including gold: in the olivine layer it is as much as 78 grams per ton. And this is not so little - gold mining is considered possible at 34 grams per ton. A pleasant surprise for scientists, as well as for the nearby plant, was the discovery of a new ore horizon of copper-nickel ores.

Among other things, the researchers learned that granites do not pass into a super-strong basalt layer: in fact, Archean gneisses, which are traditionally classified as fractured rocks, were located behind it. This made a kind of revolution in geological and geophysical science and completely changed the traditional ideas about the bowels of the Earth.

Another pleasant surprise is the discovery at a depth of 9-12 kilometers of highly porous fractured rocks saturated with highly mineralized waters. According to the assumption of scientists, it is they who are responsible for the formation of ores, but before it was believed that this occurs only at much shallower depths.

Among other things, it turned out that the temperature of the bowels is slightly higher than expected: at a depth of six kilometers, a temperature gradient of 20 degrees Celsius per kilometer was obtained instead of 16 expected. The radiogenic origin of the heat flux was established, which also did not agree with previous hypotheses.

In the deep layers more than 2.8 billion years old, scientists have found 14 types of petrified microorganisms. This made it possible to shift the time of the origin of life on the planet by one and a half billion years ago. The researchers also found that there are no sedimentary rocks at the depths and there is methane, forever burying the theory of the biological origin of hydrocarbons.

In 1970, just in time for Lenin's 100th birthday, Soviet scientists launched one of the most ambitious projects of our time. On the Kola Peninsula, ten kilometers from the village of Zapolyarny, drilling of a well began, which as a result turned out to be the deepest in the world and entered the Guinness Book of Records.

The grandiose scientific project has been going on for more than twenty years. He brought a lot of interesting discoveries, went down in the history of science, and in the end was overgrown with so many legends, rumors and gossip that would be enough for more than one horror movie.

entrance to hell

During its heyday, the drilling rig on the Kola Peninsula was a cyclopean structure 20-story high. Up to three thousand people worked here per shift. The team was led by leading geologists of the country. The drilling rig was built in the tundra ten kilometers from the village of Zapolyarny, and in the polar night it shone with lights like a spaceship.

When all this splendor suddenly closed and the lights went out, rumors immediately spread. By all measures, the drilling was remarkably successful. No one in the world has yet managed to reach such a depth - Soviet geologists lowered the drill more than 12 kilometers.

The sudden end of a successful project looked as ridiculous as the fact that the Americans closed the program of flights to the moon. Aliens were blamed for the collapse of the lunar project. In the problems of the Kola Superdeep - devils and demons.

A popular legend says that from great depths, the drill was repeatedly taken out melted. There were no physical reasons for this - the temperature underground did not exceed 200 degrees Celsius, and the drill was designed for a thousand degrees. Then the audio sensors allegedly began to pick up some moans, screams and sighs. Dispatchers who monitored the instrument readings complained of feelings of panic fear and anxiety.

According to legend, it turned out that geologists had drilled to hell. The groans of sinners, extremely high temperatures, the atmosphere of horror at the drilling site - all this explained why all work on the Kola Superdeep was suddenly curtailed.

Many were skeptical about these rumors. However, in 1995, after the work was stopped, a powerful explosion occurred at the drilling rig. Nobody understood what could explode there, even the head of the entire project, a prominent geologist David Guberman.

Today, excursions are led to an abandoned drilling rig and they tell tourists a fascinating story about how scientists drilled a hole into the underworld of the dead. As moaning ghosts roam the installation, and in the evening demons crawl out to the surface and strive to sneak into the abyss of a gaping extreme seeker.

underground moon

In fact, the whole story with the “well to hell” was invented by Finnish journalists by April 1st. Their comic article was reprinted by American newspapers, and the duck flew to the masses. Long-term drilling of the Kola superdeep proceeded without any mysticism. But what happened there in reality was more interesting than any legends.

To begin with, ultra-deep drilling by definition was doomed to numerous accidents. Under the yoke of gigantic pressure (up to 1000 atmospheres) and high temperatures, the drills could not withstand, the well was clogged, the pipes that strengthened the vent were broken. Countless times the narrow well was bent so that new branches had to be drilled.

The worst accident occurred shortly after the main triumph of geologists. In 1982, they were able to overcome the mark of 12 kilometers. These results were solemnly announced in Moscow at the International Geological Congress. Geologists from all over the world were brought to the Kola Peninsula, they were shown a drilling rig and rock samples mined at a fantastic depth that mankind had never reached before.

After the celebration, drilling continued. However, the break in work proved fatal. In 1984, the most terrible accident occurred at the drilling rig. As many as five kilometers of pipes came off and hammered the well. It was impossible to continue drilling. The results of five years of work were lost overnight.

I had to resume drilling from the 7-kilometer mark. Only in 1990, geologists again managed to cross over 12 kilometers. 12,262 meters - this is the final depth of the Kola well.

But in parallel with the terrible accidents, incredible discoveries also followed. Deep drilling is an analogue of a time machine. On the Kola Peninsula, the oldest rocks, whose age exceeds 3 billion years, come to the surface. Climbing deeper and deeper, scientists have gained a clear idea of what happened on our planet during its youth.

First of all, it turned out that the traditional scheme of the geological section, compiled by scientists, does not correspond to reality. “Up to 4 kilometers, everything went according to theory, and then the doomsday began,” Huberman later said.

According to calculations, having drilled a layer of granite, it was supposed to get to even harder, basalt rocks. But there was no basalt. After the granite came loose layered rocks, which constantly crumbled and made it difficult to move inland.

But among the rocks 2.8 billion years old, fossilized microorganisms were found. This made it possible to clarify the time of the origin of life on Earth. Huge deposits of methane have been found at even greater depths. This clarified the question of the origin of hydrocarbons - oil and gas.

And at a depth of more than 9 kilometers, scientists discovered a gold-bearing olivine layer, so vividly described by Alexei Tolstoy in the Hyperboloid of Engineer Garin.

But the most fantastic discovery occurred in the late 1970s, when the Soviet lunar station brought back samples of lunar soil. Geologists were amazed to see that its composition completely coincides with the composition of the rocks they mined at a depth of 3 kilometers. How was it possible?

The fact is that one of the hypotheses of the origin of the Moon suggests that several billion years ago the Earth collided with some kind of celestial body. As a result of the collision, a piece broke off from our planet and turned into a satellite. It is possible that this piece came off in the area of the current Kola Peninsula.

The final

So why did they close the Kola Superdeep?

Firstly, the main tasks of the scientific expedition were completed. Unique equipment for drilling at great depths was created, tested under extreme conditions and noticeably improved. The collected rock samples were studied and described in detail. The Kola well helped to better understand the structure of the earth's crust and the history of our planet.

Secondly, time itself was not conducive to such ambitious projects. In 1992, the scientific expedition was closed funding. Employees quit and went home. But even today, the grandiose building of the drilling rig and the mysterious well impress with their scale.

Sometimes it seems that the Kola Superdeep has not yet exhausted the entire supply of its wonders. The head of the famous project was also sure of this. “We have the deepest hole in the world - this is how you should use it!” exclaimed David Huberman.

Today, the scientific research of mankind has reached the boundaries of the solar system: we landed spacecraft on the planets, their satellites, asteroids, comets, sent missions to the Kuiper belt and crossed the border of the heliopause. With the help of telescopes, we see events that took place 13 billion years ago - when the universe was only a few hundred million years old. Against this background, it is interesting to assess how well we know our Earth. The best way to find out its internal structure is to drill a well: the deeper, the better. The deepest well on Earth is the Kola Superdeep, or SG-3. In 1990, its depth reached 12 kilometers 262 meters. If we compare this figure with the radius of our planet, it turns out that this is only 0.2 percent of the way to the center of the Earth. But even this turned out to be enough to turn the ideas about the structure of the earth's crust.

If you imagine a well as a shaft through which you can go down by elevator into the very bowels of the earth, or at least a couple of kilometers, then this is not at all the case. The diameter of the drilling tool with which the engineers created the well was only 21.4 centimeters. The upper two-kilometer section of the well is a little wider - it was expanded to 39.4 centimeters, but still there is no way for a person to get there. To imagine the proportions of the well, the best analogy would be a 57-meter sewing needle with a diameter of 1 millimeter, slightly thicker at one end.

Well layout

But this presentation will be simplified. During drilling, several accidents occurred at the well - part of the drill string ended up underground without the possibility of extracting it. Therefore, several times the well was started anew, from the marks of seven and nine kilometers. There are four major branches and about a dozen smaller ones. The main branches have different maximum depths: two of them cross the mark of 12 kilometers, two more do not reach it by only 200-400 meters. Note that the depth of the Mariana Trench is one kilometer less - 10,994 meters relative to sea level.

Horizontal (left) and vertical projections of SG-3 trajectories

Yu.N. Yakovlev et al. / Bulletin of the Kola Scientific Center of the Russian Academy of Sciences, 2014

Moreover, it would be a mistake to perceive the well as a plumb line. Due to the fact that at different depths the rocks have different mechanical properties, the drill during the work deviated to less dense areas. Therefore, on a large scale, the profile of the Kola Superdeep looks like a slightly curved wire with several branches.

Approaching the well today, we will see only the upper part - a metal hatch screwed to the mouth with twelve massive bolts. The inscription on it was made with a mistake, the correct depth is 12,262 meters.

How was a deep well drilled?

To begin with, it should be noted that the SG-3 was originally conceived specifically for scientific purposes. The researchers chose to drill a place where ancient rocks came to the surface of the earth - up to three billion years old. One of the arguments in the exploration was that the young sedimentary rocks were well studied during oil production, and no one had yet drilled deep into the ancient layers. In addition, there were also large copper-nickel deposits, the exploration of which would be a useful addition to the scientific mission of the well.

Drilling began in 1970. The first part of the well was drilled with a Uralmash-4E serial rig - it was usually used for drilling oil wells. The modification of the installation made it possible to reach a depth of 7 kilometers 263 meters. It took four years. Then the installation was changed to "Uralmash-15000", named after the planned depth of the well - 15 kilometers. The new drilling rig was designed specifically for the Kola Superdeep: drilling at such great depths required a serious refinement of equipment and materials. For example, the weight of the drill string alone at a 15-kilometer depth reached 200 tons. The installation itself could lift loads up to 400 tons.

The drill string consists of pipes connected to each other. With its help, engineers lower the drilling tool to the bottom of the well, and it also ensures its operation. At the end of the column, special 46-meter turbodrills were installed, driven by a stream of water from the surface. They made it possible to rotate the rock crushing tool separately from the entire column.

The bits with which the drill string cut into the granite evoke associations with futuristic details from the robot - several spinning spiked disks connected to the turbine from above. One such bit was enough for only four hours of work - this roughly corresponds to a passage of 7-10 meters, after which the entire drill string must be raised, disassembled and then lowered again. Constant descents and ascents themselves took up to 8 hours.

Even the pipes for the column in the Kola Superdeep had to use unusual ones. At depth, temperature and pressure gradually increase, and, as engineers say, at temperatures above 150-160 degrees, the steel of serial pipes softens and holds multi-ton loads worse - because of this, the likelihood of dangerous deformations and breakage of the column increases. Therefore, the developers chose lighter and heat-resistant aluminum alloys. Each of the pipes had a length of about 33 meters and a diameter of about 20 centimeters - a little narrower than the well itself.

However, even specially designed materials could not withstand drilling conditions. After the first seven-kilometer section, it took almost ten years and more than 50 kilometers of pipes to further drill to the mark of 12,000 meters. Engineers were faced with the fact that below seven kilometers the rocks became less dense and fractured - viscous for the drill. In addition, the wellbore itself distorted its shape and became elliptical. As a result, the string broke off several times, and, unable to lift it back, the engineers were forced to concrete the well branch and go through the wellbore again, wasting years of work.

One of these major accidents forced drillers in 1984 to concrete a well branch that reached a depth of 12,066 meters. Drilling had to be restarted from the 7-kilometer mark. This was preceded by a pause in work with the well - at that moment the existence of SG-3 was declassified, and the international geological congress Geoexpo was held in Moscow, the delegates of which visited the object.

According to eyewitnesses of the accident, after the resumption of work, the column drilled a well nine meters down. After four hours of drilling, the workers prepared to lift the column back, but it "did not go." The drillers decided that the pipe somewhere "stuck" to the walls of the well, and increased the lifting power. The workload has been drastically reduced. Gradually disassembling the string into 33-meter candles, the workers reached the next segment, ending with an uneven lower edge: the turbodrill and another five kilometers of pipes remained in the well, they could not be lifted.

The drillers managed to reach the 12-kilometer mark again only by 1990, at the same time the dive record was set - 12,262 meters. Then there was a new accident, and since 1994, work on the well was stopped.

The scientific mission of the ultra-deep

Pattern of seismic tests on SG-3

"Kola superdeep" Ministry of Geology of the USSR, publishing house "Nedra", 1984

The well was investigated by a whole range of geological and geophysical methods, ranging from core collection (a column of rocks corresponding to given depths) and ending with radiation and seismological measurements. For example, the core was taken using core receivers with special drills - they look like pipes with jagged edges. In the center of these pipes there are 6-7 centimeter holes where the rock enters.

But even with this seemingly simple (except for the need to lift this core from many kilometers deep) technique, difficulties arose. Due to the drilling fluid - the same one that set the drill in motion - the core was saturated with liquid and changed its properties. In addition, conditions in depth and on the surface of the earth are very different - the samples cracked from the pressure difference.

At different depths, the core yield was very different. If at five kilometers from a 100-meter segment it was possible to count on 30 centimeters of core, then at depths of more than nine kilometers, instead of a column of rocks, geologists received a set of washers from dense rock.

Micrograph of rocks raised from a depth of 8028 meters

"Kola superdeep" Ministry of Geology of the USSR, publishing house "Nedra", 1984

Studies of the material lifted from the well led to several important conclusions. First, the structure of the earth's crust cannot be simplified to a composition of several layers. This was previously indicated by seismological data - geophysicists saw waves that seemed to be reflected from a smooth boundary. Studies at SG-3 have shown that such visibility can also occur with a complex distribution of rocks.

This assumption affected the design of the well - scientists expected that at a depth of seven kilometers the shaft would enter basalt rocks, but they did not meet at the 12-kilometer mark either. But instead of basalt, geologists discovered rocks that had a large number of cracks and low density, which could not be expected at all from many kilometers of depth. Moreover, traces of groundwater were found in the cracks - it was even suggested that they were formed by a direct reaction of oxygen and hydrogen in the thickness of the Earth.

Among the scientific results, there were also applied ones - for example, at shallow depths, geologists found a horizon of copper-nickel ores suitable for mining. And at a depth of 9.5 kilometers, a layer of a geochemical anomaly of gold was discovered - micrometer grains of native gold were present in the rock. Concentrations reached gram per ton of rock. However, it is unlikely that mining from such a depth will ever be profitable. But the very existence and properties of the gold-bearing layer made it possible to clarify the models of the evolution of minerals - petrogenesis.

Separately, it is necessary to talk about the studies of temperature gradients and radiation. For such experiments, downhole instruments are used, which are lowered on wire-cables. The big problem was to ensure their synchronization with ground equipment, as well as to ensure operation at great depths. For example, difficulties arose with the fact that the cables, with a length of 12 kilometers, were stretched by about 20 meters, which could greatly reduce the accuracy of the data. To avoid this, geophysicists had to create new methods for marking distances.

Most of the commercial tools were not designed to work in the harsh conditions of the lower tiers of the well. Therefore, for research at great depths, scientists used equipment designed specifically for the Kola Superdeep.

The most important result of geothermal research is much higher temperature gradients than expected to be seen. Near the surface, the rate of temperature increase was 11 degrees per kilometer, to a depth of two kilometers - 14 degrees per kilometer. In the interval from 2.2 to 7.5 kilometers, the temperature rose at a rate approaching 24 degrees per kilometer, although existing models predicted a value one and a half times less. As a result, already at a depth of five kilometers, the instruments recorded a temperature of 70 degrees Celsius, and by 12 kilometers this value reached 220 degrees Celsius.

The Kola super-deep well turned out to be unlike other wells - for example, when analyzing the heat release of the rocks of the Ukrainian crystalline shield and Sierra Nevada batholiths, geologists showed that heat release decreases with depth. In SG-3, on the contrary, it grew. Moreover, measurements have shown that the main source of heat, providing 45-55 percent of the heat flow, is the decay of radioactive elements.

Despite the fact that the depth of the well seems colossal, it does not reach even a third of the thickness of the earth's crust in the Baltic Shield. Geologists estimate that the base of the earth's crust in this area runs about 40 kilometers underground. Therefore, even if SG-3 had reached the planned 15-kilometer cutoff, we still would not have reached the mantle.

Such an ambitious task was set by American scientists when developing the Mohol project. Geologists planned to reach the border of Mohorovichich - an underground area where there is a sharp change in the speed of propagation of sound waves. It is believed to be related to the boundary between the crust and the mantle. It is worth noting that the drillers chose the bottom of the ocean near the island of Guadalupe as a place for the well - the distance to the border was only a few kilometers. However, the depth of the ocean itself reached 3.5 kilometers here, which significantly complicated drilling work. The first tests in the 1960s allowed geologists to drill holes only 183 meters.

Plans were recently made to revive the deep ocean drilling project with the help of the exploration drilling vessel JOIDES Resolution. As a new goal, geologists have chosen a point in the Indian Ocean, not far from Africa. The depth of the Mohorovichic border there is only about 2.5 kilometers. In December 2015 - January 2016, geologists managed to drill a well with a depth of 789 meters - the fifth largest in the world of underwater wells. But this value is only half of what was required at the first stage. However, the team plans to return and complete what they started.

***

0.2 percent of the path to the center of the Earth is not such an impressive figure compared to the scale of space travel. However, it should be borne in mind that the boundary of the solar system does not pass along the orbit of Neptune (or even the Kuiper belt). The gravity of the Sun prevails over the stellar one up to distances of two light years from the star. So if you carefully calculate everything, it turns out that Voyager 2 also flew only a tenth of a percent of the path to the outskirts of our system.

Therefore, do not be upset by how little we know the "insides" of our own planet. Geologists have their own telescopes - seismic research - and their own ambitious plans to conquer the bowels. And if astronomers have already managed to touch a solid part of the celestial bodies in the solar system, then geologists have all the most interesting things yet to come.

Vladimir Korolev