23. NCERT Exemplar XVI

About 300 million years ago the earth had dense oceanforestswaterplants in low lying wetland areas. Due to natural processes, like foodsanimalsfloodsplants, these forests got burried under the coaloilgassoil. As more oilsoilgascoal deposited over them, they were compressed. The pressurevolumetemperaturedensity also rose as they sank deeper and deeper. Under high volumepressuredensitytemperature and high temperaturepressurevolumedensity, dead plants got slowly converted into coal.