The USSR is a country that surprised the world with many projects, grandiose both in scale and cost. One of these projects was called "Kola Superdeep Well" (SG-3). Its implementation began in the Murmansk region, 10 km west of the city of Zapolyarny.

Scientists wanted to learn more about the earth's interior, and "wipe the nose" of American scientists who abandoned their Mohol project due to lack of funds. To the question about what is the deepest well in the world, Soviet geologists dreamed of proudly answering: ours!

We will tell in detail in this article whether such an ambitious idea was successful and what fate awaited the Kola well.

Why did the USSR need a "journey to the center of the Earth"

Back in the 1950s, much of the material about the structure of the Earth was theoretical. Everything changed in the early 60s and 70s, when the US and Soviet Union started new version"space race" - a race to the center of the Earth, so to speak.

The Kola Superdeep Well was a unique project funded by the USSR and later by Russia between 1970 and 1995. It was drilled not at all for the extraction of "black gold" or "blue fuel", but purely for research purposes.

• First of all, Soviet scientists were interested in whether the assumption about the structure of the lower (granite and basalt) layers would be confirmed. earth's crust.
• They also wanted to find and explore the boundaries between these layers and the mantle - one of the "engines" that ensure the constant evolution of the planet.
• At that time, geologists and geophysicists had only indirect evidence of what was happening in the earth's crust, and an ultra-deep well was needed to better understand the processes underlying geology. And the most reliable way is direct observation.

The drilling site was chosen in the northeastern part of the Baltic Shield. There lie little-studied igneous rocks, which are supposedly three billion years old. And on the territory of the Kola Peninsula there is the Pechenga structure, shaped like a bowl. There are deposits of copper and nickel. One of the tasks of scientists was to study the process of ore formation.

Even to this day, the information collected through this project is still being analyzed and interpreted.

Features of drilling an ultra-deep well

For the first four years, while drilling was going on to a depth of 7263 meters, a standard drilling rig called Uralmash-4E was used. But then her opportunities began to be missed.

Therefore, the researchers decided to use the powerful Uralmash-15000 rig with a 46-meter turbodrill. It rotated due to the pressure of the drilling fluid.

The Uralmash-15000 rig was designed in such a way that samples of the mined rock were collected in a core receiver - a pipe passing through all sections of the drill. The crushed rock got to the surface along with the drilling mud. This gave the geologists the most up-to-date information on the composition of the well as the rig went deeper and deeper.

As a result, several boreholes were drilled, which branched out from one central well. The deepest branch was named SG-3.

As one of the scientists in the Kola Geological Survey said: “Every time we start drilling, we find the unexpected. It's exciting and disturbing at the same time."

Granite, granite everywhere

The first surprise that the drillers encountered was the absence of the so-called basalt layer at a depth of about 7 km. Previously, the most up-to-date geological information about the deeper parts of the earth's crust came from the analysis of seismic waves. And based on it, scientists expected to find a granite layer, and as it deepened, a basalt one. But, much to their surprise, when they moved deeper into the bowels of the Earth, they found more granite there, and did not get to the basalt layer at all. All drilling took place in the granite layer.

This is extremely important, as it is connected with the theory of the layered structure of the Earth. And with it, in turn, are associated ideas about how minerals arise and are located.

The Kola superdeep well is a source not only of the most valuable knowledge, but also of a terrible urban legend.

Having reached a depth of 14.5 thousand meters, the drillers allegedly discovered voids. Having lowered equipment capable of withstanding extremely high temperatures, they found that the temperature in the voids reaches 1100 degrees Celsius. And the microphone, before melting, recorded a 17-second audio, which was immediately dubbed "the sounds of hell." These were the cries of damned souls.

The story first appeared in 1989, and its first large-scale publication took place on the American television network Trinity Broadcasting Network. And she borrowed material from a Finnish Christian publication called Ammennusastia.

The story was then widely reprinted in small Christian publications, newsletters, etc., but received little to no exposure from the mainstream media. Some evangelists have cited this incident as proof of the existence of a physical hell.

• People familiar with the principles of operation of acoustic well survey tools only laughed at this bike. Indeed, in this case, acoustic logging probes are used, which catch the wave pattern of the reflected elastic vibrations.
• The maximum depth of the SG-3 is 12,262 meters. This is deeper than even the deepest part of the ocean - the "Challenger Abyss" (10,994 meters).
• The highest temperature in it did not rise above 220 C.

• And one more important fact: it is unlikely that a microphone or drilling equipment could withstand hellish heat above a thousand degrees.

In 1992, the American newspaper Weekly World News published an alternate version of the story that took place in Alaska, where 13 miners were killed after Satan broke out of Hell.

If you are interested in this legend, then on Youtube you can easily find videos with relevant investigations. Just don't take them too seriously, some (if not all) of the audio of supposedly suffering screams in the Underworld is taken from the 1972 film Baron Blood.

What scientists found at the bottom of the Kola superdeep well

• First, water was found at a depth of 9 km. It was believed that it simply should not exist at this depth - and yet it was there. We now understand that even deep-seated granite can develop cracks that fill with water. Technically speaking, water is simply hydrogen and oxygen atoms forced out by the enormous pressure caused by depth and trapped in layers of rock.

• Second, the researchers reported extracting mud that was "boiling with hydrogen." Such a large number of hydrogen at great depth was a completely unexpected phenomenon.
• Thirdly, the bottom of the Kola well turned out to be incredibly hot - 220°C.
• Undoubtedly, the biggest surprise was the discovery of life. At a depth of over 6,000 meters, microscopic plankton fossils have been found that have been there for three billion years. In total, about 24 ancient species of microorganisms have been discovered that somehow survived the extreme pressure and high temperatures below the earth's surface. This raised many questions about the potential survival of life forms at great depths. Modern research showed that life could exist even in the oceanic crust, but at the time, the discovery of these fossils came as a shock.

Despite all the efforts of the drillers and decades of hard work, the Kola ultra-deep well has passed only 0.18% of the way to the center of the Earth. Scientists believe that the distance to it is about 6400 kilometers.

Abandoned but not forgotten

Currently, SG-3 has neither personnel nor equipment. This is one of . And only a rusty hatch in the ground reminds of a grandiose project, listed in the Guinness Book of Records as the deepest human invasion of the planet's crust.

The project was closed in 1995 due to (you guessed it) lack of funding. Even earlier, in 1992, drilling work in the well was curtailed, as geologists were faced with higher than expected temperatures - 220 degrees. Heat damages equipment. And the higher the temperature, the harder it is to drill. It's like trying to create and maintain a hole in the center of a pot of hot soup.

By 2008, the research and production center operating at the well was completely abolished. And all drilling and research equipment was disposed of.

Results of the work

The valiant efforts of the participants of the Kola GRE lasted for several decades. However, the ultimate goal - a mark of 15 thousand meters - was never achieved. But the work done in the USSR, and then in Russia, provided a lot of information about what lies just below the earth's surface, and it still remains scientifically useful.

• Unique equipment and technology for ultra-deep drilling were developed and successfully tested.
• Valuable information was obtained about what the rocks are composed of and what properties they have at different depths.
• At a depth of 1.6-1.8 km, copper-nickel deposits of industrial importance were found.
• The theoretical picture expected at around 5000 meters was not confirmed. No basalts were found either in this or in deeper sections of the well. But unexpectedly, not too strong rocks called granite-gneisses were discovered.
• Gold was found in the range from 9 to 12 thousand meters. However, they did not begin to extract it from such a depth - it is unprofitable.

• Changes were made in the theory of the thermal regime of the earth's interior.
• It turned out that the origin of 50% heat flow associated with the decay of radioactive substances.

SG-3 revealed many secrets to geologists. And at the same time gave rise to many questions that so far remain unanswered. Perhaps some of them will be given during the operation of other ultra-deep wells.

The deepest wells on Earth (table)

Place	Well name	Years of drilling	Drilling depth, m
10	Shevchenkovskaya-1	1982	7 520
9	En-Yakhinskaya superdeep well (SG-7)	2000–2006	8 250
8	Saatlin superdeep well (SG-1)	1977–1982	8 324
7	Zisterdorf		8 553
6	University		8 686
5	KTB Hauptborung	1990–1994	9 100
4	baden unit		9 159
3	Bertha Rogers	1973–1974	9 583
2	KTB-Oberpfalz	1990–1994	9 900
1	Kola Superdeep Well (SG-3)	1970–1990	12 262

In 2008, the deepest well in the world was finally abandoned, and all lifting mechanisms and structures were dismantled.

A couple of years later, the director of the Kola Geological Institute of the Russian Academy of Sciences issued a statement that the well was gradually self-destructing. Since that time, there is no official information about her anymore.

Well depth to date

As of today, the Kola well is one of the largest drilling projects in the world. Its official depth reaches 12,262 m.

Sounds of Hell from the Kola Well

Like any grandiose project created by human hands, the Kola well is shrouded in legends and myths.

The Kola well was drilled intermittently from 1970 to 1991

This can be seen both in the Mariana Trench, which we talked about at the beginning of the article, and in.

They say that at the moment when the workers of the deepest well crossed the line of 12,000 m, they began to hear terrible sounds.

Initially, they did not pay any attention, but over time the situation changed dramatically. With the onset of complete silence, sounds of a different nature were heard from the well.

As a result, the scientists decided to record everything that happened at the bottom of the well on film using heat-resistant microphones.

While listening to the recordings, it was possible to hear human cries and screams.

A couple of hours after studying the film, scientists found traces of a strong explosion, the cause of which they could not explain.

Drilling of the Kola super-deep well was suspended for some time.

When the work resumed, everyone still expected to hear people's wailing, but this time everything was quiet.

Suspecting something was wrong, the management began proceedings regarding the origin of strange sounds. However, the frightened workers did not want to comment on the current situation and in every possible way avoided any questions.

A few years later, when the project was officially put on hold, scientists suggested that the sounds were due to movement.

Some time later, this explanation was rejected as untenable. No other explanation was offered.

Secrets and mysteries of the Kola well

In 1989, the Kola well began to be called the "road to hell", because of the sounds coming from it. There is an opinion that with each next drilled kilometer, on the way to the 13th, one or another cataclysm happened. As a result, the Soviet Union collapsed.

However, the relationship between the drilling of the Kola superdeep well and the collapse of the superpower may be of interest only to those who believe that and others are supernatural "places of power."

There is an opinion that the workers managed to reach a depth of 14.5 km, and it was then that the equipment recorded some underground rooms. The temperature in these rooms exceeded 1000°C.

They also clearly audible and even recorded human cries. However, this whole story is not supported by facts.

Dimensions of the deepest well

Depth of the world's deepest well Kola Peninsula officially registered at 12,262 m.

The diameter of the upper part is 92 cm, the diameter of the lower part is 21.5 cm.

The maximum temperature did not exceed 220°C. Inexplicable in this whole story are only sounds of unknown origin.

Benefits of drilling the Kola well

• Thanks to this project, new drilling methods were achieved, as well as improved equipment.
• Geologists have been able to discover new locations of valuable minerals.
• It was possible to debunk many different theories, for example, conjectures regarding the basalt layer of our planet.

Worldwide ultra-deep wells

As of today, there are approximately 25 ultra-deep wells, most of which are located in the republics of the former USSR.

Others also have a number of ultra-deep wells. We present the most famous among them.

• . Silyan Ring - 6800 m.
• . Tasym South-East - 7050 m.
• . Bighorn - 7583 m.
• . Zisterdorf - 8553 m.
• USA. University - 8686 m.
• Germany. KTB-Oberpfalz - 9101 m.
• USA. Beidat Unit - 9159 m.
• USA. Bertha Rogers - 9583 m.

World records for ultra-deep wells in the world

1. In 2008, the Maersk oil well (Qatar) with a depth of 12,290 m became the new depth record holder.
2. In 2011, during a project called "Sakhalin-1" (), it was possible to drill a well up to a mark of 12,345 m.
3. In 2013, the well of the Chayvinskoye field (Russia) set a new record of 12,700 m. However, it was not drilled vertically down, but at an angle to the surface.

Photo of the Kola well

Looking at the photo of the Kola well, it is hard to imagine that once life was in full swing here, and many people worked for the good of a great country.

Now there is nothing here but garbage and remnants of its former greatness. Reinforced concrete walls and empty, abandoned rooms with randomly scattered things act depressingly. Silence reigns all around.

Drilling rig of the first stage (depth 7600 m), 1974
Electrical substation building
Photo 2012
The wellhead with a metal plug. Someone scratched the wrong depth. August 2012

It is hard to imagine that under this plug there is the deepest “hole” in the earth, extending more than 12 km deep.
Soviet workers on shift change, late 1970s

The stories associated with the Kola well have not subsided so far. At present, scientists have not given a final answer about the origin of mystical sounds.

In this regard, there are more and more new theories trying to explain this phenomenon. Perhaps in the near future, scientists will be able to find out the nature of the "hellish sounds".

Now you know why the Kola well is interesting. If you liked this article, please share it with your friends. If you like it at all - subscribe to the site IinterestingFakty.org in any convenient way. It's always interesting with us!

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Drilled in the world great amount ultra-deep oil wells, but not all of them gave the expected result. However, some of them are worth remembering.

Well Z-44 Chayvo, which was drilled in Russia on the shelf of Sakhalin Island, is considered the deepest oil well in the world. It goes to a depth of about 13 kilometers - this depth is comparable to the height of 15 Burj Khalifa skyscrapers, which so far remains the tallest in the world. What is remarkable: the drillers penetrated to such a depth, which is twice the record height of a balloon flight.

Wells on this shelf are expected to produce a total of 2.3 billion barrels of oil.

Earlier, even before the drilling of Z-44 Chayvo, the famous Kola super-deep well (12268 meters) in the western part of Russia was the leader in this regard. It was drilled during Soviet times - in 1970, near a lake with the virtually unpronounceable name Vilgiskoddeoaivinjärvi. It was assumed that this well would reach a depth of 15 kilometers, but due to high (up to 230 ° C) temperatures, work was curtailed, although scientists still managed to obtain a lot of unique scientific data: for example, with its help, a two-layer model of the structure was called into question earth's crust. Currently, the well is on conservation.

Another super-deep well, OR-11, is also located in Russia. It was drilled to a depth of 12,345 meters. This announcement was made in January. 2011 from Exxon Neftegas. OR-11 became the most long well with a large deviation from the vertical.

OR-11 is located at the Odoptu field. The well set a record for the length of the horizontal well - 11.475 meters. The well was built in just two months. The length of its trunk was 12,345 meters. This well set a new world record for drilling extended reach (ERD) wells, and OR-11 also took the leading position in terms of the distance between the bottom hole and the horizontal drilling point - 11,475 meters.

Well BD-04A, which is located in Qatar, was drilled in the Al-Shaheen oil field by Maersk to a depth of 12,289 meters. The length of the horizontal wellbore was 10,902 meters. Drilled BD-04A in record time - 36 days. The drilling operation used Transocean's GSF Rig 127 drilling rig, which became even more famous in April 2010 after the Deepwater Horizon oil rig crashed in the Gulf of Mexico. Transocean was the operator of the emergency well under a contract with BP.

The Bertha Rogers mine, located in the US, is 9,583 meters deep and is another ultra-deep well. Drilled in 1974 in the Anadarko oil and gas basin in Oklahoma. The well was drilled by Lone Star - 502 days. Then the work was stopped due to the fact that the miners stumbled upon a deposit of molten sulfur. The drilling itself cost the company $15 million.

The same company also drilled another ultra-deep well, the Baden Unit, near the American town of Anadarko. Also in the USA. Its depth is 9159 meters. Drilling work began in 1970 and continued for 545 days. In total, 1,700 tons of cement were used per well, as well as 150 diamond drills. And this well cost the company a rather large amount - $6 million.

In Europe, the Hauptborung well, which is located in Germany, can be considered the deepest. It was drilled to a depth of 9101 meters. It was developed from 1990 to 1994. It was assumed that the drillers would be able to go to a depth of 12 kilometers, but, alas, it did not work out - due to very high temperatures, all work was curtailed, as a result, they managed to reach the mark of 9.1 kilometers. Today, the data on this well remains the most open - both for scientific and drilling work. Apparently, that's why she remains the most famous in the world. :///

Today, the scientific research of mankind has reached the boundaries of the solar system: we landed spacecraft to 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 learn its internal structure - 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 mm, slightly thickened at one end.

Well scheme

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 Kolsky scientific center RAS, 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 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 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 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 branch of the well, which 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 five-kilometer depth, 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 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 target, geologists have chosen a point in Indian Ocean near 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 - not so impressive compared to the scale 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 celestial bodies in solar system, then geologists have all the most interesting things yet to come.

Vladimir Korolev