During the Cold War, the United States and the Soviet Union measured themselves in a technological pulse that revolutionized science on both sides of the Pacific. The need to demonstrate an arms superiority motivated the spirit of competition, was the starting point of a race to get there where no human being had been before. A trip to hostile worlds far from the surface of the Earth. And I say worlds because the Moon was not the only objective out of the reveries of Jules Verne. While astronauts and cosmonauts took over the media, another race was taking place, but instead of going up it was moving down. It was a competition to see who penetrated deeper and faster into our rocky home (thankfully psychoanalysis is a hoax)
We could say that it all started at the end of the 50s, when the American Miscellaneous Society it was proposed to reach the earth’s mantle, the mostly “plastic” layer on which the continents move. To get an idea of the size of the project, let’s keep in mind that the Earth is about 6 378 kilometers deep, of which the mantle occupies almost 3,000. However, to reach it we have to drill the “shell” of our planet, the cold and rigid crust that we step on.
It may seem a relatively easy job, after all, the crust is quite “thin”, just a dozen kilometers in the most superficial areas. But let’s not be fooled by the scale. As shallow as it is compared to the immense mantle, crossing it remains a titanic work. In fact, it is estimated that for this, the equivalent of an average of 180 Eiffel towers should be excavated one on top of the other (about 54 kilometers). A tiny part of what separates us from the core of our planet, but equally huge.
The discontinuity of Mohorovičić
The road would be tortuous, but the American Miscellaneous Society I wanted to study the so-called Mohorovičić discontinuity. A complex name for a relatively simple concept: the point at which the crust ends and the mantle begins. Mohorovičić himself had calculated the depth at which this discontinuity was found helped by how earthquakes spread. Studying the earthquakes, he discovered that, by moving far away from the focus of an earthquake, its waves are divided. These do not all arrive in unison, but the seismograph detects them in two stages. Mohorovičić supposed that some waves had to be going through a material other than the crust, denser and through which the vibration would travel more slowly. Their calculations pointed out that the mantle should be about 54 kilometers of average depth.
Thus, to study it, the American Miscellaneous Society set out to dig a hole that would reach discontinuity and called the Mohole project. However, they suspected that the company would be difficult, so they decided to save some kilometers of crust and drill the bottom of the Pacific Ocean, much closer to the mantle than the continental surface.
Meanwhile, Mohorovičić fever infected the U.R.S.S., which in 1970 started its own project, digging in northwestern Siberia, on the Kola peninsula. Twenty years later the Germans did the same, joining the race for the mantle. However, at the risk of annihilating every epic, I will say that the Americans had to abort the project by running out of funds and that the Germans gave up after respectable 9 kilometers. In this case, it is Siberia who has a story to tell us.
Under the Kola Peninsula
The Soviet Union had set out to reach 15 kilometers, and in fact they were about to reach it. After 24 years drilling the basaltic shield of the Kola Peninsula, the depth of the well reached 12,262 kilometers deep and almost 23 centimeters wide. It wasn’t easy, they were being pioneers and that meant learning from their mistakes as they made them. How, where and with what to dig were questions that were answered on the fly, as they encountered new layers of rock. They scratched every inch and not only once, but twice, because during a landslide in 1984 they lost 5 kilometers of depth that had to be drilled again with secondary wells. Neither the weather nor the setbacks seemed to be able to stop the Soviet Union in its strange eagerness to reach the Mohorovičić discontinuity. They seemed unstoppable and yet stopped before 15 kilometers. What stood between the well of Kola and its objective was heat, a suffocating, unexpected and inevitable heat.
As we penetrate the Earth the temperature rises, but it does not do so constantly. There are places on the planet where the heat gained with each kilometer, the geothermal gradient, can reach 200ºC, while in others it barely rises 10. In this case the workers found that at 12,000 meters deep the temperature almost doubled their forecasts. We talked about 180 degrees Celsius which, added to the pressure that bore the rock of the well, made it behave strangely. The lower walls collapsed, deforming and pouring rock inside. Something like when we make a hole too deep in the beach and the water begins to enter and soak its sand collapsing it. Every new inch we dig destroys part of our walls. If the Soviet union left Kola it was not because of the cold or the effort, it was because it was not simply impossible to continue drilling.
The door to hell
The news of this well aroused the imagination of many, who fantasized that it would have reached hell itself. The press began to distort history and the 12 kilometers went to 14, the temperature rose to a ridiculous 1,000 ° C and they said that from their depths the anguished voices of those condemned to eternal punishment emanated. All talk that had nothing to do with true scientific discoveries. Because, although Kola’s well never reached the mantle, along the way he found some surprises hidden under the basaltic crust of Siberia.
The effort and money invested in this pharaonic project was not in vain. Thanks to him we know better the crust of our planet and how it behaves under high pressures and temperatures. Observing the ancient rocks extracted from the depths of the well, they were able to travel 2.7 million years in the past and (although it is not recorded in any official document that is recorded) it is reported that they discovered more than 24 different species of plankton microfossils . They discovered the large amount of hydrogen reserves that hid their soil, emanating from the muddy bottom of the well, and even came to see how water came from depths to which they did not know it existed. The well of Kola was a titanic challenge that pushed us to improve the technology of super deep drilling and that gave us hundreds of precious rocks with which to observe the interior of our cosmic home.
An impossible mint?
Today we still can’t reach the mantle. We have never been able to study “live” what is under the bark, but the dream of achieving it has not vanished. There are projects such as the “M2M-MoHole to the mantle” that seeks to drill the seabed of an area of the Pacific whose crust is just six kilometers thick. Other more futuristic proposals are committed to capsules capable of propelling themselves until the discontinuity of Mohorovičić, melting the crust in its path and saving us the fever of almost impossible wells.
Be that as it may, we have conquered the Moon before the depths of our world. Under our feet there are mysteries that remain hidden. Real secrets that tell us about the history of the Earth, our past and our future. Stories that we are only supposed to know, but we lack direct evidence. Our trip to the center of the Earth has not even begun.
DON’T KEEP IT UP:
- The Kola well is not the longest artificial well in the world. This position has been held since 2011 by the Russian oil well “Sakhalin-I” with 12 345 meters. However, it is still the deepest artificial well.
- The infernal stories echoed by the press had no foundation. In fact, the Norwegian Åge Rendalen, tested the rigor of the media by filtering false news about a winged creature that had emerged from the well to write in the air “I have overcome.”
- The discontinuity of Mohorovičić is the boundary between the crust and the mantle, but not necessarily between the lithosphere (rigid) and the asthenosphere (plastic). The surface layers of the mantle can be as solid as the crust.
- David K. Smythe et al. “Project images crust, collects seismic data in world’s largest borehole” Eos Transactions American Geophysical Union, 75 (41), 473-473 (1994).
- Craig M Jarchow & George A Thompson “The Nature of the Mohorovicic Discontinuity” Annual Review of Earth and Planetary Sciences. 17, 475-506 (1989).