1. Accumulation of Plant Matter: Large amounts of plant material, mainly from trees and ferns, accumulate in swampy environments like bogs, marshes, and deltas. These areas are rich in water and often experience periods of flooding.
2. Anaerobic Decomposition: The plant material falls into the water, where oxygen levels are low (anaerobic). This prevents complete decomposition by bacteria, leaving behind a significant amount of organic matter.
3. Formation of Peat: Over time, the partially decomposed plant material compacts and forms a layer of peat. Peat is a spongy, dark-colored material that still contains recognizable plant fragments.
4. Burial and Compression: Geological processes like subsidence (sinking of the land) or sedimentation bury the peat layers under layers of sediment. The weight of the overlying sediments creates immense pressure.
5. Heat and Pressure Transformation: As the peat is buried deeper, it experiences increasing heat and pressure. This leads to chemical and physical changes, gradually transforming the peat into coal.
6. Rank of Coal: The type of coal that forms depends on the degree of heat and pressure applied.
* Lignite (brown coal): The lowest rank of coal, with a low carbon content and high moisture.
* Sub-bituminous coal: Has a higher carbon content and lower moisture content than lignite.
* Bituminous coal: A higher-rank coal with a high carbon content and a shiny, black appearance.
* Anthracite coal: The highest rank of coal, with the highest carbon content and a very high heat content.
Key Factors for Coal Formation:
* Abundant Plant Growth: Areas with dense vegetation, such as swamps and forests, are essential for accumulating the necessary organic matter.
* Anaerobic Conditions: Low oxygen levels prevent complete decomposition of the plant material, allowing for peat formation.
* Burial and Compression: Geological processes that bury and compress the peat layers are crucial for the transformation into coal.
* Time: Coal formation is a slow process, requiring millions of years for the transformation from peat to high-rank coal.
Coal deposits are found in many parts of the world, reflecting the past presence of vast swampy environments millions of years ago.
