Charcoal is a form of the element carbon. Carbon is in all common fuels. Fuels are materials that give off heat when they are burned. A fuel may be a solid, a liquid, or a gas. Fuels that come from the remains of living things are called fossil fuels. Wood, coal, natural gas and the liquid fuel petroleum are common fossil fuels. We are only going to discuss petroleum here.

 

Petroleum is formed within the crust of the earth. It is also called crude oil. Scientists think that the bodies of prehistoric sea animals and plants became trapped in sediments. After millions of years, heat and pressure changed them into crude oil and natural gas. Crude oil and natural gas are usually found together in the crust of the earth. To get the oil and gas, it is necessary to drill into the earth's crust.

Origin and Accumulation of Oil and "Gas

Oil is a fossil fuel that is formed from plankton that is deposited in the sediments of oceans and lakes, and then buried deeply in the earth.

Coal

Fossil fuels are formed by the building up of organisms that have died. As time goes by they are buried under layers and layers of sediments. As the layers of sediment build up the pressure and heat of the organisms increases. After millions of years of increasing pressure and temperature these organisms become hydrocarbons. Most organic debris is destroyed at the earth's surface by oxidation or by consumption by microorganisms. Organic material that survives to become buried under sediments or deposited in other oxygen-poor environments begins a series of chemical and biological transformations that may ultimately result in petroleum, natural gas, or coal. (1) 

The formation of a fossil fuel depends on how deep it is in the ground. The deeper it is, the hotter it is. When it is very hot, fossil fuels form as a natural gas. When it is cooler, they form as oil. (4) 

Both oil and natural gas are formed by plants and bacteria that live on the ocean floor. When they die, the organisms combine with the sand to create an organic-rich mud. Sediment builds up over the mud and heats its up. (7) 

Fossil fuels take hundreds of millions of years to form.