ocr: YORKSHIRE OAL has been mined in Yorkshire, England, since the late 1200s. The coal seams here formed about 300 million years ago. Coal is extracted underground by "longwall" mining, a process in which a cutting machine moves back and forth along a coal face that may be over 2 km (114 miles) long. The roof of the mine is held up by powered supports that move forward with the cutter. COAL MIINE Coal is hauled above the ground using pulleys and hoisting machines.
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