
Sep 16, 2020 FOSSIL FUELS FORM. After millions of years underground, the compounds that make up plankton and plants turn into fossil fuels. Plankton decomposes into natural gas and oil, while plants become coal. Today, humans extract these resources through coal mining and the drilling of oil and gas wells on land and offshore. When energy is stored in a material, we call that material fuel. Food and wood are biomass fuels. When you have become old, old biomass that has become concentrated, you have what we call fossil fuel. The Formation of Fossil Fuels Fossil fuels are found deposited in rock formations. They were formed between 350 million and 50 million years ago.