We will now take you to the Mponeng gold mine in South Africa, which lies 4 kilometers below the Earth’s surface. This mine is also known as the deepest mine in the world. This mine is arguably the scene of the strangest business journey in the world, as miners equipped with protective gear and emergency breathing equipment have to take a 90-minute elevator ride to work.
The mine’s wells are so deep that the planet’s geothermal gradient is becoming an issue, as increasing depth means increasing temperatures. Rock temperature can rise to 60°C deep within the Earth, far above the temperature humans can withstand. This problem has required people to get creative with cooling mechanisms that keep the world’s deepest mine at a workable temperature despite the planet’s molten core.
- It may interest you: How much heat can the human body tolerate?
A combination of ventilation systems combined with a cooling plant sends mixtures of ice and cold water along with cold air through the man-made cave system, mitigating the worst effects of high temperatures. However, miners still need to work in shifts to avoid being exposed to dangerously hot conditions for extended periods of time.
Working at this depth brings with it the possible complication of barotrauma, first noticed with French miners in the early 1800s. Hike, or barotrauma, is caused by moving from a place of high pressure to a place of low pressure in a short period of time. For this reason, it is also known as decompression sickness and today most commonly affects divers, aviators, astronauts and people working in a pressurized environment.
Moving from an area of high pressure, such as the Earth’s deepest mine, to a low pressure area, such as the surface, can produce bubbles of nitrogen gas in the body. Where this becomes a problem is when the pressure change is made too quickly and gas is released into the body, the U.S. Centers for Disease Control and Prevention states. “This can be very painful and sometimes fatal,” it says. However, this pressure difference is more of an issue for people working in compressed air than in mines, as the many steps taken to control temperature and airflow reduce pressure on miners’ bodies.
Why is it necessary to dig so deep?
If you’re wondering if mining this deep is really worth all the hassle, Gemma Chilton of Engineers Australia explains that this gold mine is located in the South African state of Gauteng, where over a century of mining has exhausted the shallowest and richest deposits. As a result, humans’ search for precious metals has pushed us below the ground where we encounter new problems that require new scientifically backed solutions.
Ultra-deep mining requires building and maintaining tunnels that can withstand the pressure of the surrounding rock while also resisting subsidence. According to Guinness World Records, 2,300 kilograms of explosives are used each day to clear 6,400 tons of rock. Add to that the occasional earthquakes, and that means you have a lot of problems to contend with just to keep the tunnels afloat.
Mponeng made other surprising discoveries beyond extracting precious gold from the rock. In 2006, the first organisms known to live independently of the Sun were discovered inside the gold mine. These organisms used radioactivity as an energy source, rather than the Sun’s energy, and may be an example of how life can survive on other planets.
Diving deep into Earth’s rock face is a dangerous and complex process, but while we’re there we can learn more about the ground beneath our feet and possibly even the microbes that live elsewhere in the galaxy.
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