why do they call oil and natural gas "fossil" fuels?

http://www.kidzworld.com/article/1423-fossil-fuel-energy

http://dictionary.reference.com/browse/fossil

thanks:)

Oil and natural gas are referred to as "fossil" fuels because they are formed from the remains of ancient plants and animals that lived millions of years ago. The term "fossil" comes from the Latin word "fossilis," which means "dug up." Over time, the dead organisms settled at the bottom of bodies of water and were covered by sediments. As more and more layers of sediment accumulated, the pressure and heat caused the organic matter to undergo a chemical transformation, converting it into oil and natural gas. These fuels are called "fossil" fuels because they are extracted from the fossils, or the preserved remains, of ancient life forms.

The terms "fossil" fuels are used to refer to oil and natural gas because they are derived from the remains of ancient plants and animals that lived millions of years ago. Here's how to understand this:

1. Formation: Oil and natural gas are formed over long periods of time, typically millions of years. The process begins when tiny marine organisms, such as algae and plankton, die and settle at the bottom of oceans or lakes.

2. Decomposition: Over time, layers of sediment cover these dead organisms, creating immense pressure and high temperatures. This process is known as sedimentation and burial. As more layers accumulate, the organic matter undergoes decomposition.

3. Chemical Transformations: Under intense heat and pressure, the organic material undergoes significant chemical transformations. This results in the formation of hydrocarbons (molecules made of carbon and hydrogen atoms), which are the primary components of fossil fuels.

4. Trapped in Rock Layers: Oil and natural gas then migrate through porous rock layers, seeking paths of least resistance. Eventually, they can become trapped in reservoirs or reservoir rocks, often located deep beneath the Earth's surface.

5. Extraction: Extraction of oil and natural gas is accomplished by drilling wells into these reservoirs and using advanced technology to bring the fuels to the surface.

The term "fossil" is used because these fuels are derived from the remains of ancient living organisms that have undergone geological transformations.