What's the Deepest Hole We Can Possibly Dig?

Ever recall innocently digging a hole as a child and suddenly wondering to yourself: what would happen if I never stopped digging? Perhaps you thought you’d dig your way to another continent on the opposite side of the world, or maybe you hoped to unearth something so valuable or unusual you would be honored for your ground-breaking scientific discoveries.

For most, that isn’t a question we can even hope to answer in our adult lives. But the question itself and the mysteries surrounding it still stands: what is the deepest hole humanity could ever dig, and what might we find there?

The Ultimate Incinerator

The first question on your lips right now might be: why even bother? Isn’t humanity already doing enough damage to the planet without us attempting to drill, burrow or drive some great machine as far down as possible? But research does suggest that there might be a few viable benefits to attempting to achieve that unachievable feat.

First up on our quick list of "reasons we should attempt to dig the deepest hole ever besides just satisfying our own curiosity" is the potential to create the ultimate incinerator. It is actually a pretty handy possible solution to the worlds rapidly increasing waste problem. With landfill sites filling up fast, harnessing the unused potential of such a vast portion of the earth could bide humanity some time for waste disposal while we attempt to fix our current environmental crisis.

But it isn’t just general waste, because the earth’s molten core could also be the most effective nuclear waste disposal unit yet. That concept might sound risky, but as much of the world’s nuclear waste is currently disposed of by storing it in high-cost repositories under mountains or in caves where it can remain for thousands of years, it’s worth thinking about.

As temperatures down at the core are estimated to reach around 6000 Kelvin (5,700C, 10,300F) due to the decay of naturally radioactive elements such as Uranium, Thorium and Potassium, a superdeep, boiling hole could provide a much safer site for the biggest and most effective waste incinerator ever known.

Gravity Train

A second, more outlandish reason for attempting such an ambitious dig would be to fulfil the prophecy of the long-fabled gravity train, which really is more like an elevator than an actual train, would basically comprise of a giant tube stretching from one side of the earth to the other, providing fast and efficient travel as the capsule accelerates toward the earths core and decelerates on the way back out.

If that sounds like something from science fiction rather than a feasible possibility, its probably because it is; the gravity train has already been imagined in various ways, most famously in the 2012 action movie Total Recall. Besides, if you think it gets warm enough being stuck in a crowded elevator on a hot summers’ day, just imagine one hurtling towards the earths boiling core.

Although the gravity train might seem like be a bit of a pipe-dream, there are several other legitimate scientific and commercial gains to be had by attempting to explore further below-ground than man has ever ventured before; namely, by extracting untapped geothermal energy, gold, diamonds or even an oceans worth of water from within the mantle.

The Challenger Deep, Mariana Trench

So maybe there is still a case to be made for the world’s deepest hole, but before we delve into theories about just how to achieve that mammoth task, let’s first discuss the current existing contenders for that same title. For a little perspective, the deepest known point in the ocean is known as The Challenger Deep in the Mariana Trench, which has been measured at a depth of 36,070 feet (10,994 meters). That vastly unexplored area of the deep is shrouded in mystery, and only three men have ever reached the bottom at around 6.8 miles below sea-level.

But what is the deepest hole actually dug by hand? Originally a cost-cutting method which became a world-record attempt, The Woodingdean Water Well in Woodingdean, near Brighton UK is the deepest hand-dug well ever recorded, taking a total of four years to create with a depth of some 1285 feet.

Mir Mine

Turning attention to some of the biggest manmade hole aided by machinery, The Mir Mine is an open pit diamond mine located in Mirny, eastern Russia, which has a diameter of 3,900 ft (1,200m) and a depth of over 1,722ft (525 meters) making it of the largest excavated holes in the world. Following its initial discovery as a diamond-bearing depository in 1955, the mine bought in a 10,000,000 carats of diamond per year, and since being recommissioned in 2009 it is expected to stay in operation for another 50 years.

Natural Sinkhole

If we’re talking semi-natural holes, there’s an interesting one. The Guatemala Sinkhole is a 30-story deep gaping chasm which may appear to have been caused by a freak sinkhole but was in fact the result of a manmade “piping feature”.

A natural sinkhole occurs forms when water-saturated soil causes the roof of an underground limestone cavity to collapse, but as Guatemala City is formed atop ground made up of a material called pumice fill, the natural occurrence of that giant hole is unlikely. Instead, a lack of building regulations in the area means that untreated leaking underground pipes are more likely to have loosened the gravel-like pumice, causing the correct conditions for what is essentially a manmade sinkhole.

Kola Superdeep Borehole

But perhaps the most widely-known ‘deepest hole’ attempt goes to the Kola Superdeep Borehole in Russia, that monster hole is the result of a Soviet Union scientific project which attempted to drill as deep as possible into the Earth’s crust, reaching a true vertical depth of 40,230 feet (12,262 meters). After 24 years, drilling eventually ceased in 1994 because, basically the drill started to melt while struggling against temperatures of 180 degrees C (356 F).

Although that still remains an incredible scientific achievement, reaching deeper than the deepest point in the ocean, the Borehole still only reaches 0.002% of the way to the legitimate center of the earth, which is estimated to be more than 63,000km below the surface.

Deepwater Horizon

Another attempt, the deepest oil well in history known as the Deepwater Horizon, did manage to reach closer to the mantle than the Kola Superdeep Borehole because it was located offshore where the earth’s crust is slightly thinner. However, that particular project ended in total disaster when, in 2010, a geyser of seawater erupted causing a chain of events which transformed the slushy remnants of drilling mud and methane to transform into a gas which then ignited into a series of intense explosions.

Z44-Chayvo

In actual fact, the true deepest hole humans have ever dug is known as Z44-Chayvo, which is the world’s deepest well with a total depth of 40,604 feet (12,376 meters) in length. The Sakhalin-1 project, responsible for creating the well, had previously surpassed the Kola Superdeep Hole with its history of ambitious digging projects, but the Z44-Chavyo seriously takes the cake with a dizzying depth that is 10,000ft deeper than the peak of mount Everest, if it were turned upside down.

Building The World's Deepest Hole

Now that we described about what you might be up against if you were thinking about trying to dig the deepest hole of all time, let’s imagine what it could take to tunnel further than those existing superdeep holes combined; all expenses spared, of course.

As previously mentioned, the Earth’s center consists of various known layers which must be pierced before the spherical true core at the very middle can be reached. What’s known as the outer core, which sits below 230,000 ft (70,000 meters) of surface ‘crust’ and 1800 miles (2900km) known as the ‘mantle’, is around 1400 miles (2,260km) thick and is believed to influence earth’s magnetic field, making the solid inner core at the central point around 3958 miles (6,371 km) down from surface level, give or take.

So, with that basic scientific stuff out of the way, what is the deepest point humanity could hope to reach without all machinery burning up entirely? Current research suggests our greatest achievement could be reaching the Mohorovicic boundary or Moho which is located between the crust and the mantle at 3 to 6 Miles (5 to 10 kilometers) below the ocean floor, and 10 to 60 miles (or 20 to 90 kilometers) beneath typical continental crusts.

That landmark scientific objective could also be extremely valuable for scientific research purposes, because it is the precise area where 99% of all deep-focus earthquakes are generated and could therefore provide answers to some of the biggest questions about the origins of our planet.

Although there have been various attempts, including the Kola Superdeep Borehole to explore the Moho and the upper mantle nearby, humanity has thus far failed to travel more than a mere 0.2% of the distance to the center of the planet, and it took a lot of time and money to get there.

So where does that leave us now exactly? It’s fair to say that we have quite literally only scratched the surface when it comes to exploring the Earth’s true deepest point, but it doesn’t seem all too likely that we can hope to reach it soon, either.

That is primarily due to the extreme conditions which reside below the ground we walk on, only increasing in risk as you travel further to the center. Besides the unbearable temperatures which have now been estimated at a scorching 300 ° c (570 F) at 40,000+ ft, we might also expect to encounter some serious technical difficulties with spontaneous curving of deep wells during drilling.

In fact, it wouldn’t be too much of a stretch to assume that any attempt to drill further than the Z44-Chayvo or Kola Superdeep Borehole have already gone would be so technically challenging and expensive, at an estimated $1 Billion that it would not be done for the purpose of science at all. Considering that the overall risk appears to exceed the possible reward as things currently stand, the closest achievement we can anticipate in the near future would be piercing the outer crust in order to explore the Earth’s mantle, while the innermost layers remain just out of reach.

Don’t loose faith just yet, though; just because the chances of reaching the Earth’s center might seem slim doesn’t mean some pretty feasible ways to beat all odds have not been put forward.

One research paper published in 2005 has proposed that, because both extreme temperatures and ever increasing pressure below surface level are likely to prevent any current drilling techniques from reaching the earth’s inner core, a self-sinking nuclear capsule could well be the answer. That method would essentially involve probing the Earth’s greatest depths by detecting soundwaves omitted by the self-sinking capsule in question, which would then provide us with a greater understanding of the composition of the layers it travels through.

That delightfully simple proposal, while no doubt expensive, manages to overcome the many barriers which currently prevent further drilling by essentially allowing mother nature to do all the work mankind has been unbale to. Because the capsule itself would be made of Tungsten which has an extreme melting point of 3,400 C (6,150 F) it would be able to withstand the temperature of the mantle, while an inner sphere of highly radioactive cobalt-60 would be enough to heat and melt the surrounding rock as it travels toward the core.

Of course, there are also the obvious dangers to attempting to create an unobstructed hole to the center of the earth, like permanently disrupting the earths fundamental structure or even unintentionally causing a brutal active volcano by releasing some insane amounts of pressure through the earth’s crust, but that is all just hypothetical (for now at least)

Ultimately, it’s clear that we know less about what lies below the ground we stand on than what goes on in planets on the other side of the solar system, so attempting to dig deeper than ever before could have some serious benefits. As it stands, attempting to reach the uncharted mantle below the Earth’s crust could be our best bet when it comes to those unanswered questions, and with technological advancements never few and far between, who knows what could follow?

I hope you were amazed at this deep analysis on how to dig the deepest possible hole on Earth! Thanks for reading.