Natural gas is a mixture of gaseous hydrocarbons located under the surface of the earth, often near petroleum deposits; used as a fuel. Petroleum-liquid is a mixture of complex hydrocarbon compounds, used widely as a fuel source. Oil and natural gas are formed<span> from the remains of plants and animals. </span>
The petroleum and natural gas are two of the non-renewable resources that are formed from the burial of plants and animals about millions of years back. These are comprised of hydrocarbons that are very limited in amount and takes a long time to form. These are the fossil fuels on which the majority of the countries are directly dependent.
These are formed when the fossils were deposited in a shallow marine type of environment, detaching from the atmospheric environment.
For example, the deposition of plants and animals in the seas long time back gives rise to the formation of fossil fuel such as petroleum and natural gas.
In this case we will have deeper sea sediments (shales and limestones) being deposited on top of continentally-derived beach sediments (sand). This forms a sequence (from bottom to top) of: sand to shale to limestone. This is an indication of marine transgression
