Coal Formation
Coal forms from the accumulated remains of ancient plants that were buried and subjected to heat and pressure over millions of years. This process, called coalification, transforms plant material into progressively denser and more carbon-rich forms: peat, lignite, bituminous coal, and anthracite. As overlying sediments accumulate and compact the organic matter, geothermal heat drives off volatile compounds, leaving behind increasingly concentrated carbon deposits.
Formation and Timing
The vast coal seams found in geological strata worldwide were laid down primarily during the Carboniferous Period (approximately 359 to 299 million years ago), when extensive swamps and forests covered much of the continental landmasses. Conditions during this time favored the accumulation and preservation of plant material, though coal deposits of varying ages exist globally. The timing and extent of coal formation are linked to broader patterns of atmospheric oxygen levels and biological productivity throughout Earth’s history.
Geological Distribution
Coal deposits occur in distinct layers within sedimentary rock sequences, often interspersed with sandstone, shale, and other clastic sediments. The thickness and quality of coal seams vary considerably depending on local depositional environments, the types of plants that accumulated, and the degree of subsequent burial and heating. Major coal-bearing regions include parts of North America, Europe, Asia, and Australia, reflecting the distribution of ancient swamp and forest ecosystems.
Source Notes
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