How to achieve the world's "depth"? Scientific drilling into the earth to explore the secrets

Since ancient times, "going to the sky and into the earth" has been the dream of mankind. Now "going to the sky" has been realized, but "going into the earth" has always faced many difficulties. To directly observe the interior of the earth, only scientific drilling can do so far. It is like a "telescope" that reaches into the interior of the earth and can obtain real information and images deep underground.

Before the birth of scientific drilling, humans mainly studied the internal structure of the earth through seismic wave observation. In 1909, the former Yugoslav seismologist Mohorovic discovered the "Mohorovic discontinuity" 33 kilometers underground through seismic wave observation. In 1914, the former German seismologist Gutenberg discovered the "Gutenberg discontinuity" 2,900 kilometers underground through seismic wave observation. According to scientists' research on the reflection of seismic waves at different interfaces, the earth is divided into the crust, mantle and core from the outside to the inside, and the "Moho discontinuity" and "Gutenberg discontinuity" are the boundaries between the crust and mantle, and the mantle and core respectively. These discoveries are exciting, but "hearing is false, seeing is true". In order to more truly explore the mysteries deep in the earth, scientific drilling came into being in the 1960s.

Image source of the Earth's internal structure: Geographic Salon

Scientific drilling can be divided into ocean scientific drilling, continental scientific drilling, lake drilling and polar drilling. Humans use tools to drill a scientific well deep into the earth. Through drilling, they can obtain cores, rock cuttings and gases and liquids in rock formations. Through long-term observation of the well, they can study the deep structure and evolution of the earth, deep fluids and their effects, and verify geophysical exploration results; in terms of resource and energy development and utilization, they can study mineralization theory, oil and gas genesis, and investigate and develop deep thermal energy; in environmental science, they can study the causes of earthquakes, volcanic eruption mechanisms, geological disaster warnings, earth climate evolution, life evolution history, etc.

Many powerful countries in the world have conducted scientific drilling, and continental drilling is the mainstream. The deepest drilling is the Kola Superdeep Well in Russia, which has a depth of 12,262 meters. In March this year, my country's Deep Earth Tako Well in the Tarim Basin broke through the 10,000-meter mark and drilled through strata 500 million years ago. In the Cambrian period 500 million years ago, the Tarim Basin was still called the Tarim Sea. After millions of years of vicissitudes, the carbonate strata deposited in the ocean were buried thousands of meters underground, slowly forming oil and natural gas. This time, the geologists will analyze the rocks deposited in the ancient strata to gain a deeper understanding of the sedimentary evolution characteristics of the Tarim Basin, provide first-hand information for my country's ultra-deep oil and gas exploration, and light a beacon for my country's future ultra-deep oil and gas exploitation.

A well in the Deep Earth Taco drilled into a 500 million-year-old stratum. Image source: CCTV News

Although the scientific drilling mentioned above has drilled very deep and made a lot of scientific research progress, for the earth, it is undoubtedly equivalent to drilling a hole in the "eggshell". This is because the average radius of the earth is about 6371 kilometers, the average thickness of the outermost crust is about 17 kilometers, the average thickness of the continental crust is about 33 kilometers, and the average thickness of the oceanic crust is about 6 kilometers. Therefore, drilling through the crust and mantle to reach the center of the earth can only be a fantastic and magnificent science fiction dream.

However, human scientists are always persistent. It doesn't matter if they can't reach the center of the earth. Is it possible to drill through the relatively thin oceanic crust and reach the upper mantle? In order to realize this idea, scientists found a special "Atlantis Shoal" on the West Indian Ocean Ridge. It is located on the top of the highest sea ridge on the seabed. It is a dome-shaped uplift of 40 kilometers long and 30 kilometers wide, more than 700 meters underwater. This shoal is mainly composed of ocean core complexes where the lower ocean crust or mantle rocks are lifted upward and exposed on the seabed, which makes it possible for humans to "touch" the boundary between the crust and the mantle here. On December 16, 2015, the ocean drilling ship "Resolution" carried out the first ocean drilling aimed at penetrating the boundary between the crust and the mantle at the "Atlantis Shoal".

Atlantis Shoal on the West Indian Ocean Ridge Image source: KT News Agency

The drilling research of "Atlantis Bank" has made some progress and obtained some rock cores from the earth's crust, but the final research results have not yet been announced, and humans have not yet received any definite news to confirm that they have drilled through the earth's crust. Human exploration of the depths of the earth has not stopped, and the imagination of the depths of the earth has continued.

References:

[1] The last 50 meters! my country's first 10,000-meter-deep well drilled into a 500-million-year-old stratum. CCTV News.

[2] The mysterious Southwest Indian Ocean Ridge “Atlantis Shoal”. Xinhuanet.