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.
After horizontal drilling, the well is hydraulically fractured. From â¼8,000 to 80,000 m 3 (2â20 million gallons) of water, proppants such as sand, and chemicals are pumped underground at pressures sufficient to crack impermeable rock formations (10,000â20,000 psi).