Formation of Coal:

• Ancient Plant Matter: Coal is formed from the accumulation of plant matter in swampy environments millions of years ago.
• Peat Formation: The plant matter, including trees, ferns, and other vegetation, accumulates in layers. Incomplete decomposition due to acidic and anaerobic (oxygen-poor) conditions in swamps leads to the formation of peat.
• Burial and Compression: Over time, the peat is buried under layers of sediment, such as sand and mud. The pressure and heat from the overlying layers compress the peat.
• Transformation to Coal: As the depth of burial increases, the heat and pressure intensify, gradually transforming the peat into various grades of coal:
  • Lignite: The lowest grade of coal, with a high moisture content.
  • Bituminous Coal: A higher grade with increased carbon content.
  • Anthracite: The highest grade of coal, with the highest carbon content and energy density.

For more information, see:

• World Coal Association - How Coal Formed

Formation of Petroleum (Crude Oil):

• Marine Organisms: Petroleum is formed primarily from the remains of tiny marine organisms, such as plankton and algae, that lived millions of years ago.
• Sedimentation: When these organisms die, their remains accumulate on the sea floor and mix with sediment (sand and mud).
• Burial and Transformation: Over millions of years, the organic-rich sediment is buried under more layers of sediment. The increasing pressure and temperature transform the organic matter into kerogen, a waxy substance.
• Oil and Gas Formation: With further increases in temperature (typically between 60 to 150°C), the kerogen breaks down into hydrocarbons, forming crude oil and natural gas.
• Migration and Accumulation: The oil and gas migrate upwards through porous rocks until they encounter an impermeable rock layer (a cap rock) that traps them. These trapped accumulations form oil and gas reservoirs.

For more information, see:

• Science Learning Hub - Oil and Gas Formation