ALAN SIRULNIKOFF / SCIENCE PHOTO LIBRARY ALAN SIRULNIKOFF / SCIENCE PHOTO LIBRARY
Nodding donkey at an oil well. The nodding donkey, or beam or jack pump, draws crude oil from under the ground. Beam pumps are used when the oil pressure is not sufficient for it to come to the surface naturally, or when the oil is too viscous for methods such as gas lifting or waterflooding to be used. Photographed at Gull Lake, Saskatchewan, Canada.
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