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Who is drilling a hole more than 30,000 feet deep in the Earth's crust, and why?

Step aside, construction of mega skyscrapers and colossal bridges. China is now leading the way in a different kind of engineering marvel — they’re digging one of the deepest holes ever attempted into the Earth’s crust.

However, they’re not merely interested in setting a world record. This ambitious project aims to delve into the deep, complex layers of our planet to shed light on Earth’s geology and potentially discover new oil and gas reserves.

To comprehend the scale of this massive undertaking, imagine 33 Eiffel Towers stacked end to end. That’s the depth to which Chinese scientists and engineers intend to dig in the heart of the Taklamakan Desert in northwest China. The proposed borehole will plunge roughly 36,000 feet beneath the Earth’s crust.

Though impressive, this isn’t the first time humanity has dared to delve so deep. The record still lies with the 40,230-foot Kola Superdeep Borehole in Russia and the 40,323-foot BD-04A oil well in the Al Shaheen Oil Field in Qatar. The Chinese effort, however, is not far off from these mind-boggling depths.

Why is China digging such a deep hole?

According to China’s state-run Xinhua news agency, the project’s purpose is twofold. First, it will allow scientists to gather invaluable data on deep Earth geology.

This data will help refine our current understanding of the Earth’s crust. This comprises the rock layer, which averages a depth of about 30 kilometers or a little over 18 miles.

Second, the hole will also be used for a practical purpose — the search for oil and gas reserves. As the drilling descends to previously unexplored depths, new possibilities for fossil fuel extraction could unfold.

How to drill a hole 30,000 feet deep

Naturally, such a colossal project comes with its own set of challenges. Drilling a hole this deep requires the movement of some 2,000 tons of equipment and instruments.

From drill bits and pipes to sophisticated measurement devices, everything is being prepared for this monumental task. The whole project is not expected to be completed for over a year.

Sun Jinsheng is a scientist from the Chinese Academy of Engineering. He compared the construction difficulty of the drilling project to a big truck driving on two thin steel cables.

Moreover, the equipment must withstand extreme conditions. Temperatures can reach up to 400 degrees Fahrenheit, and the atmospheric pressure can be about 1,300 times greater than at the surface.

China is drilling a hole over 30,000 feet deep into Earth's crust. Credit: Getty
China is drilling a hole over 30,000 feet deep. Credit: Getty

What past drilling projects found

Past deep drilling projects have provided significant findings. The Kola Superdeep Borehole, for instance, yielded unexpected discoveries of water and hydrogen at depths scientists hadn’t predicted.

Another fascinating find was the presence of microscopic plankton fossils almost 20,000 feet below the surface.

Upon its completion, estimated to be in approximately 450 days, the Chinese borehole is expected to pass through 10 continental strata. These are layers of sedimentary rock stretching over entire continents. These rock layers date back to the Cretaceous System, which was formed over 145 million years ago.

By taking a deep dive into the Earth, China is offering a fresh perspective on our understanding of this planet. Simultaneously, they are opening new frontiers in the quest for energy resources. The journey to the bottom of the hole may well provide the key to unlocking further mysteries of our ancient Earth.

More about Earth’s core

The Earth is a complex structure, composed of several layers. The division of these layers is based on their chemical compositions, physical properties, and the processes that occur within them.

From the outermost surface to the innermost core, here are the primary layers of the Earth:

Earth’s crust

This is the outermost layer of the Earth that we live on. The crust is composed primarily of silica and alumina. It varies greatly in thickness, ranging from about 3 miles in the oceanic regions to approximately 45 miles in mountainous areas.

The Earth’s crust is divided into two types: oceanic crust (thinner and denser) and continental crust (thicker and less dense).

Earth’s mantle

Beneath the crust lies the mantle. This layer makes up about 84% of the Earth’s volume.

The mantle extends to a depth of about 1800 miles. It is rich in silicates and oxides and is divided into two main parts: the upper mantle and the lower mantle.

The boundary between the crust and the mantle is called the Mohorovičić discontinuity or “Moho.” The mantle is not completely solid but behaves more like a very viscous fluid, allowing for the slow movement of tectonic plates.

Earth’s outer core

The outer core, which extends to a depth of about 3200 miles, is mostly composed of liquid iron and nickel. This fluid layer generates the Earth’s magnetic field through a dynamo effect as the Earth rotates.

Earth’s inner core

The innermost layer of the Earth, the inner core, is a solid sphere composed mostly of iron and nickel. Despite the immense heat (estimated to be similar to that of the Sun’s surface), the enormous pressure at this depth keeps the core in a solid state. The inner core has a radius of approximately 750 miles.

This layered structure is crucial to understanding not just the composition of the Earth, but also the processes that occur within it. These include plate tectonics, volcanic activity, and the generation of the Earth’s magnetic field.

Additionally, there are other ways to categorize the Earth’s layers, such as by their mechanical properties. By this definition, the Earth is divided into the lithosphere (the rigid outer layer that includes the crust and the uppermost mantle), the asthenosphere (the part of the upper mantle that can flow and move), the mesosphere (the lower mantle), and the outer and inner core, as described above.

It’s important to note that although we have a general understanding of the Earth’s structure, there is still much to learn. Our knowledge is based on studying seismic waves from earthquakes, the magnetic field, and other indirect evidence.

As mentioned previously, the deepest humans have ever drilled — the Kola Superdeep Borehole — reached only about 0.2% of the way to the Earth’s center.

More about the Kola Superdeep Borehole

The Kola Superdeep Borehole is a scientific drilling project of the Soviet Union that began in the 1970s. It holds the record for the deepest hole ever drilled into the Earth’s crust.

The site is located on the Kola Peninsula in northwest Russia. Here’s what we know about this significant project:

Depth and duration

The drilling started in 1970 and continued intermittently until 1992 due to various difficulties and delays.

The deepest hole, called SG-3, reached a staggering depth of about 7.5 miles or 40,230 feet in 1989. That depth made it the deepest hole ever drilled at the time, and it still holds that record to this day.

Purpose of digging into Earth’s crust

The primary aim of the project was to explore the Earth’s crust, understand the changes in geological strata, and detect the presence of any resources. This scientific endeavor allowed for unprecedented insight into the Earth’s structure.

What they found deep in Earth’s crust

The project brought about several surprising discoveries. For instance, contrary to expectations, the transition from granite to basalt (referred to as the “Conrad discontinuity”) that was expected to occur at a depth of about 7 kilometers did not happen.

Instead, the drilling revealed more granite. This suggests that our understanding of the Earth’s crust had some gaps. Also, they discovered water at depths where it was not expected to exist, along with microscopic plankton fossils some 6,000 meters below the surface.

Challenges of digging so deep

Drilling to such extreme depths presented numerous challenges. The project encountered higher temperatures and pressures than anticipated.

At the greatest depth, the temperature was around 356 degrees Fahrenheit, which was much hotter than the predicted 212 degrees Fahrenheit. These harsh conditions made drilling further and maintaining the borehole extremely challenging.

Current status

After drilling ceased in 1992, the site was abandoned in 2008 due to lack of funding and the fall of the Soviet Union. The borehole was capped with a welded metal plate.

Legacy of the Kola dig

While the Kola Superdeep Borehole didn’t break through to the mantle as originally hoped, the project yielded valuable information about the Earth’s crust and made a significant contribution to geology. It continues to inspire other ambitious drilling projects aimed at exploring the mysteries of the Earth’s deep interior.

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