The world’s deepest operational gold mine is located southwest of Johannesburg, South Africa. The commute to reach the entire vertical length of the mine takes more than an hour. The temperature of the rocks reach a staggering 66°C, and ice slurry is pumped continuously to maintain the temperature below 30°C. Ventilation is provided with 14-foot-wide, giant fans that enable airflow regulation throughout the mine.

The mine workers use shaft elevators to access the mine. The mine is comprised of numerous tunnels that are prone to rock bursts. The crew sprays the walls with shotcrete, a flexible concrete reinforced with steel fiber. It is further held in place by diamond-mesh netting to prevent the rocks from caving in. Moreover, air-powered hand-held drills are used for operations within the mine. For more challenging shafts, the miners use monster fans capable of blasting 10 feet of rock per day. (1, 2)

10 Davidson Seamount – the largest and deepest known seamount is 7,480 feet tall, yet its summit is still 4,101 feet below the sea’s surface.

The Davidson Seamount is a pristine undersea mountain habitat located off the coast of Central California. Measuring from its base to crest, the seamount measures 7,840 feet, yet its summit is located 4,101 feet below the surface of the sea. The seamount was discovered in 1933 and is named after George Davidson, a famous geographer. Based on argon dating, the seamount is estimated to have formed 15 million years ago.

The seamount is a biological treasure trove consisting of 237 species and 27 types of deep-sea coral in its ecosystem. As a diversity measure, the seamount was included into Monterey Bay National Marine Sanctuary in 2009. The surface of the mount is made of blocky lava flows, volcanic ash, and pyroclastic material. The base of the mountain is buried deep within the seabed. (source)

11 Challenger Deep – the deepest known point in the Earth’s oceans measuring 36,070 feet below sea level. If Mt. Everest were placed at this location, it would be covered by over one mile of water.

The Challenger Deep is located in the Mariana Trench in the Pacific Ocean. It is a slot-shaped depression in the bottom of a crescent-shaped oceanic trench. The deep was named after the Royal Navy vessel which recorded its initial depth.

Only four descents have been made so far, and film director James Cameroon became the first human to reach the bottom of the trench. The descent was made possible by a deep-submergence vehicle named Deepsea Challenger. It had taken him a total of two hours and 36 minutes to reach the bottom.

A robot submarine exploring the deep recorded strange noises comprised of low rumbles, alien moans, and high-pitched screeching. Scientists have attributed the noise to both natural and man-made sources. The alien moans were identified to be a never-before-heard song from minke whale, a type of baleen whale.

The rumbles and screeching noises were attributed to a category four typhoon that passed overhead, earthquakes, and ship traffic. The scientists also reported that the deep is home to millions of microbial life forms. (1, 2)

12 Kola Borehole – an abandoned borehole known as the deepest artificial point on the Earth. The 40,000 feet deep man-made hole is shielded by a small metal cover.

The Kola Superdeep Borehole is a scientific drilling project launched by the Soviet Union in the Pechengsky District, Kola Peninsula. The project was a result of competition between the United States and the Soviet Union.

The nations competed with each other to drill the deepest hole in the world. While the United States was forced to abandon its “Project Mohole” due to insufficient funding, the Soviet Union was successful in surpassing the United States by drilling up to 40,000 feet into the Earth.

Numerous boreholes were drilled from a point, and the deepest one reaching over 40,000 feet was named “SG-3.” The project was a site of extensive geophysical studies that included seismic discontinuities, Earth’s thermal temperature, the physical and chemical composition of the crust, rock structures, and geophysics.

The scientists were able to discover water formed by stray oxygen and hydrogen atoms squeezed between the rocks filled with minerals. Microscopic plankton fossils were discovered around six kilometers below the surface. There were large quantities of hydrogen gas in the form of “boiling mud.”

The project was abandoned in 1995 after encountering scorching temperatures of 180°C, increased rock density, and dissolution of the Soviet Union. Though it may appear deep, the hole was able to cover only 0.002% of the distance to the center of the Earth. (source)

13 Z-44 Chayvo Well – belonging to Project Sakhalin-1, it is the world’s deepest extended-reach oil well located offshore to the east of Russia. It reaches a whopping 40,604 feet into the seabed.

The project started on 28 January 2011 by a consortium of oil corporations. The company was successful in drilling the world’s longest oil ERD well surpassing all records.

The well was completed within 60 days and approximately produces 250,000 barrels of oil per day.

The hole is equivalent to 15 times the height of the world’s tallest skyscraper, the Burj Khalifa in Dubai. The cost of drilling the well was estimated to have totaled $12 billion.

The rigs operating in the well are capable of withstanding earthquakes. They can also be operated in -40°C harsh winters that the country is subjected to every year. (1, 2)