Explore More Energy
help teacher resources contact us
web sites glossary careers explore more
profiles uses issues viewpoints

Fossil Fuels: Millions of Years in the Making

Fossil fuels get their name from the organisms that created them. Fossil fuels were formed from plants and animals that lived hundreds of millions of years ago. Around 300 million years ago the earth was covered by giant seas and the continents were just forming. All sorts of organisms were alive: trees, plants, land animals, fish, and protoplankton (one-celled organisms). The climate was warmer and swamps and bogs were everywhere. When these organisms died, they were covered up by layers of mud, rock, sand, and in some cases water. Sometimes thousands of feet of earth buried these fossils. Over the next many millions of years, the plants and animals decomposed into fossil fuels. The type of fuel the organisms became depended on several factors:

Who they were buried with.
How long they were buried.
What temperature and pressure existed while they were decomposing.

Oil and Natural Gas
Sea life is the source of oil and natural gas. These organisms died and were buried in ocean and river sediment. The ancient oceans and rivers dried up and over time new oceans and rivers covered the old waterbeds. Meanwhile, the protoplankton decayed and pressure and heat combined with bacteria to cook the organisms. This produced a thick oil. In hotter regions the cooking process continued for longer and natural gas formed.

Coal was formed by the same sorts of pressure and temperature as oil and natural gas, but coal comes from the remains of ferns (a much more widely spread species 300 to 380 million years ago), trees, and other plants.