How is coal formed?
Coal originates from the transformation of terrestrial plants into carbon through burial. As trees and other plants growing in ancient forests and swamps died and decayed, their remains formed peat bogs. Over time, the bogs were buried by sediments, and as the depth of burial increased, the peat was subjected to increasing temperature and pressure, which resulted in a decrease in moisture content and an increase in carbon content. Scientists estimate that a coal seam 30 centimetres thick required up to 2.5 metres of compacted plant debris. The peat was transformed sequentially through the different ranks of coal – lignite, sub-bituminous, bituminous and anthracite. The rank of coal is therefore a function of time, temperature and pressure.
Coal from Canada’s Atlantic provinces began forming between 280 and 350 million years ago; coal in Western Canada began forming between 65 and 135 million years ago.
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