What’s At The Bottom Of The Deepest Hole On Earth?

Geologists and travel enthusiasts are familiar with many of the earth’s deepest places. The Dead Sea is the lowest place on Earth in terms of feet below sea level. We know about the Marianas Trench. There are some super deep mines around the world. What’s deeper than all of those features, though, is the Kola Superdeep Borehole.

This is a hole that’s actually man-made, but the bottom of it has never been accessed by humans. Keep reading to find out what’s at the bottom of it.

Where It Is

borehole
Photo Credit: @goandtryit / Instagram
Photo Credit: @goandtryit / Instagram

The Kola Superdeep Borehole is located in the Pechengsky District northwest of the Murmansk oblast, on the coast of the Barents Sea. This district is close to Finland and Norway. The hole itself is the result of a scientific drilling spearheaded by the Soviet Union.

What Is A Borehole?

borehole left behind
Photo Credit: @thisisnikirussell / Instagram
Photo Credit: @thisisnikirussell / Instagram

Engineers and environmental consultants use the term “borehole” to describe all of the various types of holes drilled as part of a geotechnical investigation. Basically, a borehole is a hole that’s dug for exploratory purposes.

How Deep Is It?

hole in the ground
Photo Credit: @jng.san / Instagram
Photo Credit: @jng.san / Instagram

The Kola Superdeep Borehole is the deepest hole on Earth, as its name suggests. So how deep is it? It’s actually only 23 centimeters (9 inches) wide, but it’s 12,262 meters (40,230 feet) deep.

Why Does It Exist?

MURMANSK REGION, USSR. October 30, 1986. Kola superdeep borehole. Drillers A. Sarayev (L) and I. Gritsay at work.
Photo Credit: Alexander Tumanov / TASS
Photo Credit: Alexander Tumanov / TASS

This hole is the product of a scientific arms race. Around the time that the Kola Superdeep Borehole was dug, America had just won the race to the moon. Other countries were taking another route and trying to beat each other to the center of the Earth.

When Did They Start The Big Dig?

borehole plug
Photo Credit: @intellectinterviews / Instagram
Photo Credit: @intellectinterviews / Instagram

The Americans started what they called “Project Mohole” in 1958. They were trying to beat the Soviet Union to the core of the Earth. They stopped digging in 1966—but the Russians chose not to. They kept digging straight through to the 1990s.

Just Keep Digging

The illuminated Eiffel Tower
Photo Credit: Chesnot / Getty Images
Photo Credit: Chesnot / Getty Images

The Kola Superdeep Hole is actually not one hole but several boreholes attached to a single original hole. The deepest main hole is as deep as 37.8 Eiffel Towers stacked end to end.

What They Found Down There

earths layers
Photo Credit: @intellectinterviews / Instagram
Photo Credit: @intellectinterviews / Instagram

The point of digging this hole in the first place was to gain more information about the physical makeup of our planet. Scientists actually got a lot of geological information from the hole, though they haven’t pierced through to the planet’s mantle.

Very Old Fossils

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Photo Credit: DeAgostini / Getty Images
Photo Credit: DeAgostini / Getty Images

Scientists expected to learn a lot about the formation of the Earth. What they didn’t expect was to make some astounding palaeontological discoveries. At around 6.4 kilometers (roughly 4 miles) down, 2-billion-year-old microscopic plankton fossils were found.

There Was Water Down There

Medium caliber grenades inner chamber borehole with special revolver machines
Photo Credit: Getty Images
Photo Credit: Getty Images

In addition to the fossils, scientists discovered that there was actually free-flowing water below the Earth’s surface. It was squeezed by subterranean rock and trapped under incredible amounts of pressure.

Things Got Hot

borehole skyview
Photo Credit: @tfi5 / instagram
Photo Credit: @tfi5 / instagram

Eventually, the project had to come to an end. The scientists couldn’t keep on digging forever. One of the main reasons why they stopped digging is because temperatures got too high. It was 180°C (356°F) down there.

A Long Way To Go

girl at borehole
Photo Credit: @quasar_waves / Instagram
Photo Credit: @quasar_waves / Instagram

This hole sounds really deep (and it is), but to put things in perspective, even though this is the deepest hole on earth, it’s only 0.19% of the way down to the center of the planet.

Can They Go Deeper?

glass found at hole
Photo Credit: @quasar_waves / Instagram
Photo Credit: @quasar_waves / Instagram

Certain areas on Earth are easier to drill through than others. The floor of the ocean is often at least 4.3 miles deep. Continental crust is thicker at 22 miles deep, but it is often less dense. It is way more difficult to drill through land than it is to drill under the ocean.

So Why Not Drill Under The Ocean?

big boat on ocean
Photo credit: AFP via Getty Images
Photo credit: AFP via Getty Images

That’s a very good question. It turns out, scientists are actually doing this. There’s a dig going on right now in the Atlantis Bank of the Indian Ocean. There’s a piece of oceanic crust that’s cooler than usual in that area, which makes things easier for engineers.

The Dig Continues

The Earth is formed of three concentric layers: the core, the mantle and the crust; these are separated by transition zones called discontinuities.
Photo Credit: QAI Publishing / Universal Images Group via Getty Images
Photo Credit: QAI Publishing / Universal Images Group via Getty Images

This project in the Indian Ocean has been ongoing for a number of years. Scientists have been stopping and starting the dig at this location for a while. At this point, they’re still working to reach beyond the crust to the Earth’s slowly churning mantle.

A Big Discovery

The sun is reflecting on the wet granite rock
Photo Credit: Wolfgang Kaehler / LightRocket via Getty Images
Photo Credit: Wolfgang Kaehler / LightRocket via Getty Images

One of the main things scientists learned from the Kola Superdeep Borehole is that granite doesn’t turn into basalt at great depths as we previously thought. They found no evidence of this transition happening at 4.3 miles below the Earth’s surface.

More New Information

borehole site
Photo Credit: @ra_kamal / Instagram
Photo Credit: @ra_kamal / Instagram

Scientists were also surprised to learn that there was a large amount of hydrogen gas under the Earth’s surface. The mud that flowed out of the borehole was described as “boiling” with hydrogen.

The End Of The Project

mask at site
Photo Credit: @arthurvanderlee / Instagram
Photo Credit: @arthurvanderlee / Instagram

Work finally ended on the Kola Superdeep Borehole in 1995 when the Soviet Union dissolved. The site is now completely abandoned. The mask in the photo above was left behind by one of the scientists who worked on the project.

You Can Still Visit The Hole

abandoned hole
Photo Credit: @gattodimarzo / Instagram
Photo Credit: @gattodimarzo / Instagram

Lots of people still visit the ruins and the remnants of the site all these years later. There was once a tower standing by the hole that was destroyed sometime between 2007 and 2012.

The Value Of The Hole

motorcycle by sign
Photo Credit: @arthurvanderlee / Instagram
Photo Credit: @arthurvanderlee / Instagram

Geologist Benjamin Andrews explained, “If we have a better knowledge of what the mantle is and how the mantle behaves, we have better knowledge of volcanoes and earthquakes, and better knowledge of how the planet as a whole works.” That’s why the Kola Borehole is so important.

Still The Record-Holder

lanscape around hole
Photo Credit: @cartraveller68 / Instagram
Photo Credit: @cartraveller68 / Instagram

Many other boreholes and tunnels have been drilled for the purpose of scientific inquiry, but the Kola Superdeep Borehole still holds the record for the deepest man-made hole on this planet.

Right In Front Of The Pantheon

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Alessandro Serrano’/AGF/Universal Images Group via Getty Images
Alessandro Serrano’/AGF/Universal Images Group via Getty Images

The sinkhole that appeared in the middle of Rome was discovered in front of the Pantheon, a house of worship used continuously since it was first constructed back in 117 AD.

It is located in Rome’s Piazza Della Rotonda, which is exactly where a 10-square-foot section of the earth collapsed on itself, opening a hole in the ground. After the sinkhole emerged nobody knew exactly what the archeologists would find once they began sifting through the rubble.

It Wasn’t Out Of The Ordinary

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CIRO FUSCO/ANSA/AFP via Getty Images
CIRO FUSCO/ANSA/AFP via Getty Images

Although the sinkhole in front of the Pantheon can be considered unique, sinkholes around Rome aren’t all that uncommon. This is mainly because the city is so old that all ancient quarries, tunnels, and catacombs built in the past eventually collapsed after all of those thousands of years.

Particularly in the eastern region, Rome has countless hidden cavities beneath the cobblestone streets that used to be mined, which are now full of history and waiting to be discovered.

They Never Seem To End

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TIZIANA FABI/AFP via Getty Images
TIZIANA FABI/AFP via Getty Images

Sinkholes in the Eternal City can sometimes reach over 100 in just the passing of one year! Nevertheless, not many of them become as popular as the hole that emerged in front of the Pantheon in April 2020.

However, this one caught the attention of countless archeologists who figured that there had to be something worth finding beneath the ground since it was located in a part in the city that was packed full of history.

The Legacy Of The Pantheon

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Laszlo Szirtesi/Getty Images
Laszlo Szirtesi/Getty Images

To this day, the Pantheon remains one of the best-preserved ancient Roman structures that were built by our ancestors thousands of years ago. Even more impressive, it is still in use today and is still utilized as a place of worship, just like it was during ancient times.

However, it is now a church that is typically closed off to tourists during the weekends so that the locals can worship in peace without being disrupted.

It Wasn’t Always A Church

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Hulton Archive/Getty Images
Hulton Archive/Getty Images

Even though Rome’s Pantheon may be used as a church today, that wasn’t always the purpose it served. The original structure, which is different from the one we see today was built in 25 BC by Marcus Agrippa, whose father-in-law Augustus was Rome’s first emperor.

This version was much smaller and wasn’t a church, but a place for the people of Rome to worship the Roman gods. However, the Greek words that makeup “pantheon” are pan, meaning “all” and theos, meaning “gods”.

It Was Destroyed By A Fire

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VW Pics/Universal Images Group via Getty Images
VW Pics/Universal Images Group via Getty Images

Unfortunately, the original Pantheon only stood for around 100 years before a fire consumed it, destroying it almost entirely.

Then, Emperor Minitian, who ruled over Rome from 81 to 96 AD, had the temple rebuilt. Incredibly, this new temple wouldn’t prove to last long either, and it was struck by lightning and destroyed in 110 AD. This led worshippers to be superstitious about the structure, considering that it had been “struck down” twice.

Emperor Hadrian Was Known For Ordering The Construction Of Numerous Structures

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De Agostini via Getty Images/De Agostini via Getty Images
De Agostini via Getty Images/De Agostini via Getty Images

It wasn’t until Emperor Hadrian rose to power in 117 AD that he decided to rebuild the Pantheon that we know today. Known for his appreciation of architecture and the arts, he made building various structures around his empire one of his main priorities.

However, one of his most notable architectural accomplishments is Hadrian’s Wall, a 73-mile wall that stretches across northern England. This wall marked the northwestern border of Rome’s territory, and beyond was considered the “end of the world”.

Hadrian Paid Homage To His Predecessors

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LBERTO PIZZOLI/AFP via Getty Images
LBERTO PIZZOLI/AFP via Getty Images

Most experts agree that the third and final Pantheon was finished between the years 126 and 128. AD. When Hadrian officially opened it, he didn’t forget about those that came before him.

He added a description of the structure that confused historians for quite some time. It reads: “Marcus Agrippa the son of Lucius, three times Consul, made this.” Experts now know that Hadrian most likely built the new Pantheon on the same spot as Agrippa did.

The Pantheon Eventually Suffered From Disrepair

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Icas94 / De Agostini Picture Library via Getty Images
Icas94 / De Agostini Picture Library via Getty Images

Just 200 years later, the capital of the Roman Empire was moved from Rome to Byzantium which is modern-day Istanbul. Unfortunately, this didn’t exactly work out for the Pantheon. During this transition, the Pantheon fell into disrepair. This continued until 609 AD when Pope Boniface IV stepped in to fix things.

He spoke with the Byzantine emperor Phocas, asking permission to give the Pantheon a new purpose, with Boniface hoping to convert it into a Catholic church, which he was allowed to do. He named it Sancta Maria ad Martyres, Latin for St. Mary and the Martyrs.

From Pagan To Catholic

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Fine Art Images/Heritage Images/Getty Images
Fine Art Images/Heritage Images/Getty Images

And just like that, the temple that was once a place of pagan worship was turned into a Catholic church. Not only was this the first time that such a transition was made, but it had a great effect on the Pantheon’s structure.

Now, the Pope had the resources to return it to its former glory and maintain it. To do so, the builders used a combination of concrete and bricks, creating three major sections which are the portico, rectangle interior, and its incredible ceiling.

Its Roof Is An Architectural Feat

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David Aschkenas/Construction Photography/Avalon/Getty Images
David Aschkenas/Construction Photography/Avalon/Getty Images

The Pantheon’s domed roof is considered to be one of the most impressive achievements ever accomplished by Rome’s ancient architects. Incredibly, it arcs overhead without needing any kind of visible support, making it all the more impressive.

For more than 1,000 years, it held the title of the largest cupola in the world, and today remains the only concrete roof in this style that doesn’t have reinforcements to support it. So, not only is it a marvel of the ancient world but the modern world, too.

There’s More Than Just The Dome

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Werner Forman Archive/Heritage Images/Getty Images
Werner Forman Archive/Heritage Images/Getty Images

While the dome itself is incredibly impressive, with a diameter of just over 142 feet, what is even more mind-blowing is the Pantheon’s oculus in its center. At the top, there is a 28.5-foot circular opening. However, this wasn’t included just for any reason.

It’s was built specifically so that those inside could be closer to the gods that they worshipped. Architecturally, it also reduces the tension the dome places on the structure, one reason it has stood for so long.

Even Michelangelo Was Impressed

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DeAgostini/Getty Images
DeAgostini/Getty Images

Michelangelo is considered one of the most talented artists of all time, especially those living during the Italian Renaissance. Speaking of the Pantheon, he described it as a divine design, and it was unbelievable that man could create something so perfect.

The structure’s design also inspired Thomas Jefferson, who created his own copula for his estate in Virginia, known as Monticello. Many of the American state capitol buildings have also drawn inspiration from the design.

Another Connection To The Pantheon

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Kaveh Kazemi/Getty Images
Kaveh Kazemi/Getty Images

On top of impressing some of the Renaissance’s most renowned artists, it became a popular burial site for many people of importance during that time because it was made into a Catholic church.

This includes the painter Raphael and some Italian monarchs. Today, tourists from all over the world come to see the incredible architecture and the gravesites of some incredibly notable individuals from the past.

Lost History

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John Moore/Getty Images
John Moore/Getty Images

The modern-day Rome area has been inhabited by humans for thousands of years, even before it became a civilized city. So, understandably, a lot of this history has been lost beneath the ground. This includes a network of quarries mined by the ancient people.

The miners also dug cavities, tunnels, and catacombs that are causing the sinkholes in Rome today. Another thing that creates the sinkholes is the loose soil that the city’s foundation is built on.

Investigating The Sinkhole

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Alessandro Serrano’/AGF/Universal Images Group via Getty Images
Alessandro Serrano’/AGF/Universal Images Group via Getty Images

The sinkhole opened up in front of the Pantheon in April of 2020, starting out as a 10-foot-square hole that was 8-feet deep. Although the hole itself was big, compared to everything that lies beneath Rome’s city, it was only a fraction of what could be discovered. Nevertheless, the hole provided some key insight into Rome’s past.

A team of archeologists from ANSA took up the role of investigating the sinkhole, unsure of what they might find.

They Found Ancient Stones

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DeAgostini/Getty Images
DeAgostini/Getty Images

When the archeologists from ANSA first made their way into the sinkhole, they discovered paving stones that dated far back to the ancient times when Rome was the capital of the empire.

In total, there were seven of these stones which were dated to be around 25 to 27 BC. Interestingly, 27 BC was also the same year as the empire’s creation.

The Stones Were Part Of The First Temple

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Alessandro Serrano’/AGF/Universal Images Group via Getty Images
Alessandro Serrano’/AGF/Universal Images Group via Getty Images

As we already know, Agrippa built the first Pantheon in Rome around the same time, 25 BC to be exact, with his father-in-law, Augustus, served as Rome’s first emperor.

From this information, historians concluded that the ancient slabs of stone were part of Agrippa’s first temple’s work. What makes it even more fascinating is that Agrippa helped design the stones himself. The archaeologists were astounded by this discovery, knowing they were standing right on top of history.

How The Stones Ended Up Underground

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Araldo de Luca/Corbis via Getty Images
Araldo de Luca/Corbis via Getty Images

After the first Pantheon built by Agrippa had burned down, Hadrian had a new one built in his place, one of his many architectural achievements. Furthermore, he also ensured that the surrounding piazza was refurbished.

The piazza and Pantheon underwent further renovations at the beginning of the 200s, which pushed the original stones used deep into the ground. However, this wasn’t the first time that these ancient stones had been unearthed during the modern age.

Some Were Found In The 1990s

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Alessandro Serrano’/AGF/Universal Images Group via Getty Images
Alessandro Serrano’/AGF/Universal Images Group via Getty Images

In the 1990s, workers were laying a brand new network of service cables that ran through an underground tunnel. It was during this project that they found the travertine stonework laid by the ancient Romans.

While this was still an incredible find in the 1990s, what made the discovery in April 2020 that much more fascinating was that they had been found due to a sinkhole. It was almost as if they wanted to be found.

They Were Reburied After Discovery

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Alessandro Serrano’/AGF/Universal Images Group via Getty Images
Alessandro Serrano’/AGF/Universal Images Group via Getty Images

When the stones were initially found by those working on the service cables in the 1990s, they were examined and then reburied. Nevertheless, they were buried with a layer of pozzolan on top.

The superintendent of Rome, Daniela Porro explained in a statement that pozzolan is a material that is similar to cement when wet. So, adding a layer on top after returning the stone to the earth acts as a form of protection from damage over time.

The Pozzolan Was Successful

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Alessandro Serrano’/AGF/Universal Images Group via Getty Images
Alessandro Serrano’/AGF/Universal Images Group via Getty Images

When the stones were once again uncovered in April 2020, Porro made sure to mention how the pozzolan had successfully protected the artifacts.

In a statement in May 2020, she commented that it was, “an unequivocal demonstration of how important archaeological protection is, not only an opportunity for knowledge but fundamental for the preservation of the testimonies of our history, an invaluable heritage in particular in a city like Rome.”

The Sinkhole Helped Prevent A Disaster

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Alessandro Serrano’/AGF/Universal Images Group via Getty Images
Alessandro Serrano’/AGF/Universal Images Group via Getty Images

Because of all of their planning and preservation tactics that were put in place to protect the stones, the Romans were lucky regarding the timing of the Pantheon’s sinkhole finally opened up.

The national Italian newspaper La Stampa reported that “The area, fortunately closed, could have become a hazardous trap for Romans and the thousands of tourists who on a beautiful day in the middle of spring, in a ‘normal’ period, would have filled it.”

Rome Has Precautions Put In Place

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Annette Reuther/picture alliance via Getty Images
Annette Reuther/picture alliance via Getty Images

Thankfully, Rome’s government is well-aware of the dangers of sinkholes that plague the city, which is one of the downsides of living in such a historic area.

To help correct the problem, in March 2018, the city announced its plan to fix the more than 50,000 potholes that riddled the city to prevent them from opening into sinkholes. The mayor, Virginia Raggi, designated a €17 million (more than $20.5 million) budget to put the project into action and stop future problems.

Things Didn’t Go As Planned

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ANDREAS SOLARO/AFP via Getty Images
ANDREAS SOLARO/AFP via Getty Images

When Raggi first announced her new plan to fix the potholes, she promised that 50,000 of them would be filled and fixed within the first month of the program. Yet, since the spring of 2020, the project has been delayed significantly.

Because of this, potholes still remain a great danger to both the thousands of citizens and tourists of Rome that walk the streets every day. Furthermore, sinkholes have continued to form due to a lack of maintenance.

Other Sinkholes At Historic Sites

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ELIO CASTORIA/AFP via Getty Images
ELIO CASTORIA/AFP via Getty Images

Although the sinkhole in front of the Pantheon was all the buzz for a while, it wasn’t the only sinkhole to open up near one of Rome’s most historic locations. In January 2020, one of these craters opened up on Via Marco Aurelio, which is very close to the iconic Colosseum.

As a result, the city officials had to evacuate an entire apartment building as they closely inspected the safety of the ground surrounding the new hole.