Why the Soviet Union's dream of digging through the Earth could not be carried out, finally understood after more than 50 years

During the Cold War of the last century, the world's exploration activities went into a frenzy.

On the one hand, the United States and the Soviet Union were chasing each other in space, and finally, the United States won first with the moon landing.

The Soviet Union was not satisfied, and they were ready to do something big to regain their temporary backwardness in the space struggle, which was the Soviet Union's later Project Geocentric.

Beginning in 1970, the Soviets drilled holes in their own Kola Peninsula, trying to penetrate the Moho interface and give the United States failed Moho plan a burn.

So just how deep did the Soviets dig?

Rushing to the Earth's core

The Kola Deep super borehole, once the world's deepest with a depth of 12,263 meters, was the product of the Soviet Union's geocentric program.

In 1970, NEDRA, the Soviet Union's scientific research and development center, began this program, and their destination was the Moho interface, the interface between the Earth's crust and mantle.

The Moho interface is a concept proposed by geologist Mohorovich, and there is no physical presence of this on Earth.

The United States first started the Moho program in the 1950s, but it ended in disaster when it was drilled to 315 meters.

The Soviet Union's Kola Deep Hole started relatively smoothly, breaking the 10,000-meter mark on a high note.

If the trend continues, drilling to the core of the earth does not seem to be a problem.

The road to drilling went on and on, and even the collapse of the Soviet Union did not stop it from drilling down the road, and Russia took over and continued with this core program.

It was not until 2008 that Russia announced that it would not continue drilling the Kola Deep Hole, and its depth was thus fixed at 12,263 meters.

What made it impossible to continue drilling the Kola Deep Hole?

Drilling is not that easy

There are several reasons for stopping the Kola drilling, the main one being funding, as Russia can no longer afford to pay such expensive expenses.

The vast majority of the money spent on the Kola drill hole was spent on drilling equipment, and the drill bit, which was built at great expense, could fall apart after 10 minutes of drilling, and the last 263 meters took Russia 10 years (1983 to 1993)

This is because the drilling team found that the further down the rock was drilled, the harder it became, and could not be drilled at all with just the usual drill bits.

So the researchers frantically developed a new drill bit and then found that the new bit would only drill about 1 meter more than the average drill bit.

The average density of the earth's crust is 2.75g/cm3, but it is unevenly distributed, with the density increasing the further down you go.

In the end, the newly developed drill bit couldn't hold up.

The density of 10,000 meters underground is much higher than ordinary rock

The human-developed drill bit drills the rock below the surface of 1000 meters without effort, but drilling the rock below 10,000 meters, which is very hard, must ensure that the hardness of the drill bit than the rock layer.

Of course, it is not enough to satisfy the hardness, the drill bit must also withstand high temperatures.

The intense friction between the drill bit and the rock generates huge amounts of heat, and this heat is enough to burn the metal of the drill bit.

For this reason, the drillers had to cool the drill bit while drilling to maintain the temperature of the drill pit at over 300 degrees.

This was another huge expense, and the entire program used enough coolant to last a year in all of Russia's steel mills.

In addition to the hard rock and high-intensity friction, there was one more thing that the drills needed to deal with: high pressure.

After entering the underground, the pressure increased by 27.5MPa for every 1,000 meters dug, and when proceeding to a place below 10,000 meters, the drill bit needed to withstand a pressure of 275MPa or more, so it can be said that the scrap rate of the drill bit fee was very large.

When proceeding to 12,263 meters, Russia had already exhausted the funds for the program.

Geologists, after comprehensive consideration, recommended that drilling be stopped, first of all, there is no longer a need to drill further because human technology has reached the top, the current material can only go so far.

Secondly, the Kola borehole is still very far from the center of the earth, and even it is very far from even the target ground Moho interface.

The average thickness of the crust is about 17 km, and the Moho interface is 33 km below ground.

The Kola borehole did not break through the crustal layer and is still more than 20 kilometers away from the Moho interface, which is more than 20 kilometers beyond human reach.

The last thing is that the geocentric plan works very inefficiently because the excess debris inside the drill hole must be removed, so the broken-off heads must be picked up.

Just having to traverse more than 12,000 meters would have taken the drilling crew time to work and would have required replacing the bits, which was another amount of time.

The drilling team kept drilling 24 hours a day and could not have made any more progress.

Even with this ability to drill through, the consequences are very serious. Below the earth's crust is the mantle.

The mantle is divided into the upper mantle and the lower mantle, the lower mantle is mainly solid, but a part of the upper mantle is liquid, and that part is called the soft flow layer.

Perhaps people are unfamiliar with the soft flow layer but say it's another name everyone will be familiar with, magma.

The soft current layer is the transition zone of the crust advancing to the mantle, at a distance of 70 to 250 km from the surface, where the volcanic magma originates.

If the Kola borehole drills through the crust, then it will touch the soft flow layer, which will be ejected directly from the borehole and form a super crater, and then the whole Kola Peninsula will be covered with magma.

What drill bit, derrick, everything on site, all turned into nothing. The temperature of the soft fluid layer is between 700 and 1400°C, enough to melt the surface rocks right off the ground.

As for the core of the earth, where the Soviets wanted to go, that was even less likely!

The hot core of the earth

To get to the core, the soft current layer is but the first obstacle beyond the crust, and below it, there is a thick mantle.

The mantle is the part of the Earth that occupies the largest volume and mass, with a thickness of 2,900 km, and it also becomes denser the further down it goes.

The average density of the upper mantle is between 3.2 and 3.6 g/cm3, but by the time it reaches the lower mantle the average density is above 5 g/cm3.

Imagine how a drill that struggles to drill through the crust can drill through the mantle.

The innermost part of the Earth is the core, and there is also a liquid transition layer between it and the mantle, with a temperature of 4000 to 5000℃.

And in the range of 5100 km to 6300 km underground is the inner core, which is also the highest temperature on the whole earth, with 6000℃, this temperature is close to the surface of the sun.

There is speculation that the core of the Earth is inhabited by "core people", but this is almost impossible, because not to mention the temperature of the core, the pressure of the core alone is 3.6 million atmospheres, no organism can withstand this pressure.

Regarding why the Earth's core is so hot, this may be related to the formation of the Earth. After all, the Earth's core was the first to be formed, and it was the material within the nebula cluster at that time, which was bound to have various fusion reactions.

When fusion proceeds to its limit, the elements formed are iron, cobalt, and nickel, which are the most dominant substances in the Earth's core.

These iron, cobalt, and nickel are completely different from the iron, cobalt, and nickel we see on the surface, and are various isotopes that produce decay, fission, and even more radioactive elements, such as uranium and plutonium.

Scientists speculate that the earth's core is a giant nuclear reactor.

Of course, since humans have never reached the Earth's core, the Earth's core being a nuclear reactor is just a hypothesis by geologists.

Because no one currently knows what the Earth's core looks like or why it is so hot.

Harnessing the Earth

Humankind is in an unprecedented energy crisis because the three main sources of energy on which we depend, coal, oil, and natural gas, are non-renewable and cannot be produced again for 100,000 million years after they are used up once.

However, the energy available to mankind is not to these three, they are somehow only the energy in the earth's crust, and not all the energy of the crust, but only part of it.

Like wind energy, water energy, tidal energy, etc., is also the energy of the earth's crust, human use is not yet very smooth.

The only energy outside the earth's crust that humans use is currently geothermal energy.

In some places where the earth's crust is thin, the soft reservoir layer heats the bottom of the crust and allows it to produce heat, and people can use geothermal instead of coal, oil, and natural gas.

However, geothermal heat is not controllable, it emits energy 24 hours a day and has a very low utilization rate, and most of the geothermal heat is dissipated.

This shows that although humans live on the Earth, our knowledge of the Earth is very limited, and our exploration of the Earth is limited to the surface of the Earth's crust, and even the Kola Deep borehole is still inside the Earth's crust.