Fossil Fuel

After food, fossil fuel is human's most important source of energy. There are three major fuels: oil, natural gas and coal. Oil gives us our mobility, our cars, planes, trains, trucks and boats. Natural gas is used primarily to produce heat, like gas for cooking, and industrial processes. Coal is used primarily to produce electricity. It provides us with light, and power for electronic devices.

http://usoe.k12.ut.us/curr/science/core/8thgrd/student/biology/fuel.html

The reason they are called fossil fuels is because they are all made from decayed plants and animals that have been preserved in the earth's crust by pressure, bacteria and heat. It takes millions of years for these organisms to chemically change into fossil fuels. We believe that the fossil fuels we use today may have formed back in Mesozoic period, around 250 million years ago, when dinosaurs still roamed the earth, or even before.



http://www.phys.trinity.edu/ece/energy_resources/oil.ht...