fossil fuels

• fossil fuels are formed over millions of years

  they are non-renewable
• coal:

  • formed from the remainder of ferns and trees
  • if these die in marshy wetland so don't decompose (lack of oxygen/acidic conditions) = prevents bacteria from carrying out decomposition
  • overtime the plant remains are covered in sediment and compressed
  • high temp and pressure = coal
• oil:

  • crude oil is formed from plankton
  • when these die, they settle in mud on the sea bed
  • if no oxygen they don't decompose
  • overtime, compressed by sediment
  • heat and pressure = crude oil
• natural gas:

  (mainly hydrocarbon methane)

  • plankton died
  • were covered in sediments
  • subjected to high temperatures and pressures