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.
Low Yielding Rock Formations. In low yielding rock formations the well may have to be drilled deep enough to serve as a storage cavity for ground water. Once a well is drilled, the total depth, depth to the top of the ground water table (static level) and diameter of the well determine how much water will be stored within the well cavity. The larger the well diameter the more water will be stored for a given well depth and water table elevation.