Darker skin tends to be more acne-prone because it has larger sebaceous glands that produce more oil. Those with darker skin are more likely to experience post-inflammatory hyperpigmentation (PIH), dark spots that linger for weeks or months after acne has healed, caused by the overproduction of melanin.
If the hole had reached the initial goal of 15,000 meters, temperatures would have reached a projected 300Â°C (572Â°F). When drilling stopped in 1994, the hole was over seven miles deep (12,262 meters), making it by far the deepest hole ever drilled by humankind. The last of the cores to be plucked from from the borehole were dated to be about 2.7 billion years old, or roughly 21 million times older than Coca Cola.
As of 2003 the deepest mine is the East Rand mine at 3585 meters, but as technology improves and the search for natural resources continues many mines are constantly being deepened. In the next few years, the Western Deep mine will reach 5 km. Many problems arise when digging so deep into the Earth. The most obvious is the heat. For example, at 5 km the temperature reaches 70 degrees Celsius and therefore massive cooling equipment is needed to allow workers to survive at such depths.