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The Deepest Holes Ever Dug

Holes. Whether as children digging in the dirt, or professional engineers and miners, people of all ages share a primordial fascination with wanting to figure out how deep they can bore into the Earth. While the Earth’s crust is relatively thin in comparison to the planet as a whole, the geological scale still allows for tens of kilometers for humans to try to dig through. While this may not seem too far a length on the surface, even going to space can seem a more                   manageable task than getting just halfway through the Earth’s crust. The deeper the hole becomes, the more advanced the technology must be to even function, as temperatures rise to startling high levels the closer the drill gets to the superheated outer mantle. 

There are many reasons to try to dig deep into the Earth’s crust. Many expensive and useful resources exist only at extreme pressure and heat below the surface, such as diamonds and oil. This can make the seemingly direct, if difficult process of drilling thousands upon thousands of meters deep quite lucrative if you know where to begin the hole. However, this was not the case for the deepest hole ever dug, which began through a combination of national pride and scientific exploration: the Kola Superdeep Borehole. 


Kola Superdeep Borehole

the kola superdeep borehole
The Kola Superdeep Borehole.By Rakot13, is licensed under CC-BY-SA

Located in Murmansk, Russia, the story of the Kola Superdeep Borehole mirrors that of the space-race between the United States and Soviet Union. Both countries sought to gain scientific ground on the other, sending crafts far into space itself–but also into the Earth’s crust. While the United States’s project suffered from underfunding and didn’t make much progress, over the course of twenty years, the USSR managed to create the deepest hole in world history. 

Their goal was simple: made it 15 kilometers deep, or as deep as they could until technical difficulties prevented going further. Drilling in the Kola Peninsula began in 1970, eventually creating one giant tunnel with several off-shoot tunnels branching off. The hole that made it the furthest down, titled scientifically “SG-3”, made it an incredible twelve kilometers, piercing about one third of the Earth’s crust. At only just shy of 23 centimeters thick, the Kola Borehole was thin, but yielded an incredible amount of scientific evidence due to the specific parameters of its construction. 

The Russian scientists had made it possible for their instruments to take measurements and other geological data at the tip of the drill. The direct sampling not only provided the Soviet scientists samples from deeper than ever before, but the analysis from the drill itself was far more accurate than if they had needed to bring the samples to ground level. Not only did these discoveries add to our knowledge of tectonic plates, seismic activity, and the cycles of rock formation deep underground, but evidence of life in the form of microscopic fossils was found, dating at over 2 billion years old. 

Unfortunately, the Kola Superdeep Borehole’s original goal of 15 kilometers was not to be. Having reached twelve kilometers–80 percent of their goal–ahead of schedule, the Soviet scientists took a (perhaps earned) vacation, setting plans to move forward with the drilling just one year in the future. But no one remained to take care of the equipment during the vacation–which can be a problem when machines need to reliably function at temperatures as high as 180 degrees Celsius. When drilling resumed, breaking equipment made the project falter at each new step, until it was finally abandoned in 1992. 

Mir Mine

the hole of mir mine
The open pit diamond mine of Mirny in Yakutia. Its depth is 525 meter.By Vladimir is licensed under CC-BY

Interestingly, in addition to the deepest, the world’s second-largest hole dug can also be found in modern Russia. This hole’s goal was not depth, but a combination of width and height–because the builders of this hole wanted to find as many diamonds as they could. Mir Mine, located just outside Mirny, Siberia, is 1.25 kilometers across and one-half of a kilometer deep. This makes it not only a successful diamond mine, but also the largest open pit in the world–and this openness can be a danger, if you believe the rumors of helicopters disappearing due to its construction. 

Supposedly, the sheer size of the hole creates a gap in air pressure around its center–and when helicopters fly through, the vortex prevents their rotors from the spinning, and they plummet to their doom. This led to the myth that helicopters are not even allowed in the airspace above Mir Mine–though controllers at the mine itself have never substantiated these claims. 

Historically, the mine was created in the early days of the USSR to satisfy an industrial need for high-grade diamonds in manufacturing. It was opened by Stalin in 1957, though construction was slow due to the harsh environment of the Siberian tundra. Ice had to be constantly broken, sheared, and burned off, with the scientists having to resort to explosives in some areas to blast through the thick sheets of frozen water formed from the regular -40 degree Celsius temperatures that comprise the Siberian winter. In 2017, an internal flooding closed the mine, the pool at the bottom being visible from its edges. Though inoperational today, there are slow plans to get the mine reopened by the year 2032. 


But digging deep holes doesn’t have to begin at ground level–or even on the ground at all. Many scientists and businesses alike have drilled holes into the Earth through the sea to gain access to materials and geologic data. The records for the world’s largest offshore holes are claimed by two sources, for two purposes: the Japanese ship Chikyu, for the deepest hole made for scientific exploration, and Deepwater Horizon, the BP oil drilling rig that claims the overall record for the deepest offshore hole. 

Since 2007, the ship Chikyu has drilled just over three kilometers into the oceanic crust in search of geologic data related to tectonic activity in the Pacific Ocean. Scientists hope that gathering this sort of information will better enable geologists to predict earthquakes and earthquake-related tsunamis. More accurate predictions would allow faster preparations and evacuations in the case of these devastating natural disasters, saving lives all across the Pacific islands and coasts of Asia and the Americas. As well, like the scientists at the Kola Superdeep Borehole, the crew of the Chikyu also recovered a vast amount of geologic records from billions of years of rock sublimating through the Earth’s crust and back up into the ocean floor. Greater comprehension of this activity could give us information about how the Earth recycles material, and how the heat and pressure within the lower layers of the Earth’s core affect deep sea environments. And as with any environmental research, the Chikyu scientists are hoping that study and evidence in these areas allows for scientists in a variety of fields to better combat the causes and effects of climate change. 

Since 2013, Chikyu has been manned by an international group of geologists as part of the International Ocean Discovery Program. In an effort that continues to mirror the Kola Superdeep Borehole, over one billion dollars may be funneled into new equipment to help the drill go further than ever before. More advanced technologies are being developed and implemented to survive the pressures and heats necessary to continue to search deeper into the oceanic crusts’s mysterious depths. 

Deepwater Horizon

Pushing deeper and deeper for the purposes of science can be more safe than trying to excavate materials from these deep manmade holes–as demonstrated by Deepwater Horizon, the oil rig which since 2010 still holds the record for deepest offshore drilling project, and whose explosive destruction caused an environmental disaster so catastrophic a Hollywood blockbuster was made to dramatize the events. 

BP, or British Petroleum, is one of the world’s largest gathers and sellers of oil, and does so through a total of eleven drilling rigs in the deep regions of the Gulf of Mexico. As a company with a net worth of almost 60 billion USD, it is obvious that their drilling and selling of oil has been commercially successful. However, many critics point to Deepwater Horizon as a prime example of the reasons why deep ocean drilling for oil can go horribly wrong. 

On April 20, 2010, the Deepwater Horizon drilling rig had reached an incredible 5,486 meters deep into the Earth’s crust, on top of the approximately 1500 meters the rig floated atop the ocean floor. On this fateful day, a pocket of natural gas erupted and broke one of the concrete cores which sealed the drill shut, killing and injuring almost 30 crew. While it took two days for the drill to sink, the damage had been done, and the backwards pressure upon release of the broken mechanisms caused oil from the hole to surge into the Gulf of Mexico, topping at an incredible rate of 60,000 barrels per day. 

Over the next few months, BP scientists and engineers managed to overcome the leak and plug it, but over 149,000 square kilometers of ocean been covered by the resulting oil slick, and 1,770 kilometers of beach were polluted, resulting in evacuation of coastal homes and a massive loss of marine life. At incredible cost, the dangers of deep water drilling had been made apparent to the general public, and debate about these questionable oil rigging practices remains a heated topic between climate scientists and oil companies. 

The quest to delve deeper into the Earth’s crust is an exciting and broad topic. Though human beings have gone so far into space as to set foot on the moon, we know remarkably little about the inner workings of the planet we inhabit. While we marvel at the footprints on the lunar soil, even a few miles beneath our own, the Earth houses potential answers to our histories, and greater understandings of dangers we may face in the future. Countries, corporations, and scientific groups alike have all sought to uncover these mysteries. Massive holes have been dug in the frozen tundra in search of industrial-grade diamonds–while thin tunnels have been drilled kilometers upon kilometers deep in search of information and resources. Life has been discovered–and little by little, the inner workings of tectonic activity become less shrouded in the unknown. But this drilling also poses danger–to the crews working these vastly complicated mechanisms, and to the natural life nearest these boreholes. Ethical questions must be asked: how far are people willing to go to continue to push these records further? What are the potential consequences when all might go wrong–do they outweigh the benefits? Benefits to whom? 

In the end, the history of scientific discovery has proven far safer than that of material extraction. And with scientific developments, we may continue to take a particularly human pleasure in witnessing how far down we can dig a really, really big hole. 

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