Labels:bulletin board | door | unknown OCR: MINES AND MINING WHAT IS MINING? INING 1S the extraction of natural resources from the Earth's crust Mining possible because over millions of years geologic forces have concentrated these resources into deposits some within human reach Deposits on or near the Earth surface are often excavated by open pit mining or dredging. Deeper deposits are mined underground UNDERGROUND MINE This machine holes for roo bolts under rground sdrilling hotes roaf
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