ocr: How COAL FORMED - ILLIONS of years ago, plant Mremains (1) were buried and 2 compressed into peat, or rotting vegetation (2). As the peat was buried deeper, heat and pressure 3 changed it first to lignite (3), then to bituminous coal (4), and lastly to anthracite (5). In general, the deeper the coal was buried, the more + carbon it contains. As carbon burns very well, deeply buried coal such as anthracite makes efficient fuel for heating. 5
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