National Geographic : 1944 May
Fairchild Aerial Surreys, Inc. To Harvest Coal, Surface Miners Plow Level Indiana Farm Lands into Mountainous Windrows Seen from the air, the coal seam is a long black rut dug by a stripping shovel (page 579). Smaller shovels glean the coal. Soon dirt from afresh turrow will fill the hole and cap it with a ridge. So economical is strip mining that 80 feet of earth have been removed toget36inches ofcoal.